Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


C.K.

#11184

Wave Solder Problems - VIA HOLES | 3 June, 1999

I'm encountering a new problem at my new company that I haven't encountered before in my past life - and that's Wave Soldering VIA holes.

We've been getting a rash of defects that we call in this company, "insufficient solder in VIA hole." These defects result in failures at ICT. Some of our PCB's have over a thousand (.013" dia.?) holes, and yes, they're plated-through.

I've checked for everything required to make a solder joint - flux, heat, and sufficient solder contact and dwell time. Every other joint looked excellent. Other PTH's, such as axial and radial parts' holes, had excellent solder fillets and great top-side wetting. Even the 0603's soldered nicely.....so, it lead me to one conclusion...POOR PCB QUALITY.

My theory is that there is bad or insuffient copper plating in these VIA hole plated barrels, and as a result, solderability is compromised. I know it isn't a PROCESS PROBLEM (even though our manufacturing supervisors LOVE to think so), based on all the other indicators that I've described above. After all, solderability of your boards and parts is half the battle. If my theory is correct, what do i need to do to check solderability of these things?

Oh great WAVE SOLDER GURUS of this forum, please help me either confirm or dispute this theory!!

reply »

#11185

Re: Wave Solder Problems - VIA HOLES | 3 June, 1999

| I'm encountering a new problem at my new company that I haven't encountered before in my past life - and that's Wave Soldering VIA holes. | | We've been getting a rash of defects that we call in this company, "insufficient solder in VIA hole." These defects result in failures at ICT. Some of our PCB's have over a thousand (.013" dia.?) holes, and yes, they're plated-through. | | I've checked for everything required to make a solder joint - flux, heat, and sufficient solder contact and dwell time. Every other joint looked excellent. Other PTH's, such as axial and radial parts' holes, had excellent solder fillets and great top-side wetting. Even the 0603's soldered nicely.....so, it lead me to one conclusion...POOR PCB QUALITY. | | My theory is that there is bad or insuffient copper plating in these VIA hole plated barrels, and as a result, solderability is compromised. I know it isn't a PROCESS PROBLEM (even though our manufacturing supervisors LOVE to think so), based on all the other indicators that I've described above. After all, solderability of your boards and parts is half the battle. If my theory is correct, what do i need to do to check solderability of these things? | | | Oh great WAVE SOLDER GURUS of this forum, please help me either confirm or dispute this theory!! |

CK: You�ve sold me. It sounds like an in-bound material problem, but before we go into that:

1 I�ll buy the heat, sufficient solder contact, and dwell time, but how do know that you�re fluxing the vias properly? Are you getting flux on the top side of the board? 2 How do you know the vias are supposed to be soldered, other than some techs in ICT whining about not getting good vacuum? 3 Will solder flow through a 13 mil diameter hole? Or is the surface tension of solder too great?

OK let�s talk about your board:

1 Is this new problem new to you and new to your new company? 2 What is the history of this design? (is this a new product)? 3 How widespread is the problem? 4 Is the failed item from a single manufacturer or from various sources? 5 Is the failed item from a single lot or from various lots? 6 Why aren�t you having your fab supplier plug the vias? Then, this is just a discussion on whether you should be plugging top or bottom side. 7 What kind of solder mask is on the boards? Has someone changed the solder mask? Was the solder mask used to plug the vias previously? 8 What kind of solderability protection is on the vias? 9 How are these boards checked for solderability at incoming? 10 When you look at a section of the via, what kind of wetting do you get? 11 Has the manufacturer been contacted, provided samples of failed items, and provided a response? 12 So, when the manufacturing supervisors squirt flux on the vias, load-up a 800 watt iron with solder, and solder the vias; can they get good solder flow?

Dave F

reply »

Scott B

#11186

Re: Wave Solder Problems - VIA HOLES | 4 June, 1999

| I'm encountering a new problem at my new company that I haven't encountered before in my past life - and that's Wave Soldering VIA holes. | | We've been getting a rash of defects that we call in this company, "insufficient solder in VIA hole." These defects result in failures at ICT. Some of our PCB's have over a thousand (.013" dia.?) holes, and yes, they're plated-through. | | I've checked for everything required to make a solder joint - flux, heat, and sufficient solder contact and dwell time. Every other joint looked excellent. Other PTH's, such as axial and radial parts' holes, had excellent solder fillets and great top-side wetting. Even the 0603's soldered nicely.....so, it lead me to one conclusion...POOR PCB QUALITY. | | My theory is that there is bad or insuffient copper plating in these VIA hole plated barrels, and as a result, solderability is compromised. I know it isn't a PROCESS PROBLEM (even though our manufacturing supervisors LOVE to think so), based on all the other indicators that I've described above. After all, solderability of your boards and parts is half the battle. If my theory is correct, what do i need to do to check solderability of these things? | | | Oh great WAVE SOLDER GURUS of this forum, please help me either confirm or dispute this theory!! |

We have experienced exactly the same problem and no matter what process tweaks we made, we still could not fill all of the vias. We eventually put it down to the via hole diameter as Dave suggested. Despite reluctance from our ICT engineer we insisted that it was not a requirement to fill the vias and forced him to look for a test solution. He has now replaced all via probes with spear tips which has now solved the problem.

Regards

Scott

reply »

#11187

Re: Wave Solder Problems - VIA HOLES | 4 June, 1999

| | I'm encountering a new problem at my new company that I haven't encountered before in my past life - and that's Wave Soldering VIA holes. | | | | We've been getting a rash of defects that we call in this company, "insufficient solder in VIA hole." These defects result in failures at ICT. Some of our PCB's have over a thousand (.013" dia.?) holes, and yes, they're plated-through. | | | | I've checked for everything required to make a solder joint - flux, heat, and sufficient solder contact and dwell time. Every other joint looked excellent. Other PTH's, such as axial and radial parts' holes, had excellent solder fillets and great top-side wetting. Even the 0603's soldered nicely.....so, it lead me to one conclusion...POOR PCB QUALITY. | | | | My theory is that there is bad or insuffient copper plating in these VIA hole plated barrels, and as a result, solderability is compromised. I know it isn't a PROCESS PROBLEM (even though our manufacturing supervisors LOVE to think so), based on all the other indicators that I've described above. After all, solderability of your boards and parts is half the battle. If my theory is correct, what do i need to do to check solderability of these things? | | | | | | Oh great WAVE SOLDER GURUS of this forum, please help me either confirm or dispute this theory!! | | | | CK: You�ve sold me. It sounds like an in-bound material problem, but before we go into that: | | 1 I�ll buy the heat, sufficient solder contact, and dwell time, but how do know that you�re fluxing the vias properly? Are you getting flux on the top side of the board? | 2 How do you know the vias are supposed to be soldered, other than some techs in ICT whining about not getting good vacuum? | 3 Will solder flow through a 13 mil diameter hole? Or is the surface tension of solder too great? | | OK let�s talk about your board: | | 1 Is this new problem new to you and new to your new company? | 2 What is the history of this design? (is this a new product)? | 3 How widespread is the problem? | 4 Is the failed item from a single manufacturer or from various sources? | 5 Is the failed item from a single lot or from various lots? | 6 Why aren�t you having your fab supplier plug the vias? Then, this is just a discussion on whether you should be plugging top or bottom side. | 7 What kind of solder mask is on the boards? Has someone changed the solder mask? Was the solder mask used to plug the vias previously? | 8 What kind of solderability protection is on the vias? | 9 How are these boards checked for solderability at incoming? | 10 When you look at a section of the via, what kind of wetting do you get? | 11 Has the manufacturer been contacted, provided samples of failed items, and provided a response? | 12 So, when the manufacturing supervisors squirt flux on the vias, load-up a 800 watt iron with solder, and solder the vias; can they get good solder flow? | | Dave F | | |

Geez, those test guys are always whining about via holes, aren't they? I even had one test guy go over to our finals/add-on department and instruct everone to look for unfilled vias and fill them by hand! Without consulting the area manager or engineer! Just took matters into his own hands. I'll tell ya, that little trick put him right at the top of my Christmas List.

The other guys pretty much coverd all the bases on why vias aren't filling - gotta narrow it down to a specific lot/vendor/source if it's an incoming material problem. One thing I have encountered in the past, however, that hasn't been mentioned is adhesive residue in the holes. If the bottomside operators get a bad glue print (or dispense) and clean off the board, they get the surface free of adhesive, but don't always check the holes. When you're wiping or squeegeeing glue off the board, it likes to sneak into those holes and hide there, silently waiting to hose up your soldering process. If there is adhesive in there, you should be able to see a light residue under the scope. Just a tinge of color. Given the contamination theory, the boards could have contaminants in there from the fab house, too.

Now them thar holes are pretty small and tough to get flux/solder into. Air environments make trying to get solder in the hole even tougher, since all these nasty little pieces of microdross are sitting on top of the wave just trying to block the flow of the nice solder.

And even though you get good flux coverage across the board, it doesn't necessarily mean that the flux is penetrating the tiny little vias. Good ol' foam used to penetrate the vias well, since it's surface tension was always getting busted up. Ultrasonics make nice tiny little droplets that will penetrate well, but pressure sprays can have some difficulty, since their drops are bigger (just opened the door for Steve Skinner on that one, didn't I?). To see if the flux is penetrating, give it the old fax paper test. Sandwich the paper between two raw cards and flux them. You should see the penetration on the fax paper when you pull the sandwich apart. If you don't, you may just have to adjust your fluxing parameters - more pressure or more air flow to enhace the spray. I don't know what kind of fluxer you're running, but when we were evaluating the Jet Fluxer, this was one of the issues we found. And the only solution on that model was more pressure - I think we had to go to 20 psi to get good topside wetting. Needless to say, we "Opt"ed for a different machine.

As for checking for solderability, the first place to go is your procurement spec, since that the contract that binds you and your suppliers. Your company may have their own spec, or they may use an IPC standard. The spec should call out a test method and a pass/fail criteria. It may seem to be a really STUPID, USELESS, OUTDATED test, like something with RA flux and 5 seconds dwell time, because it never got updated with the rest of the world, but unfortunately, them's the breaks. Or it may be reasonable. In any event, that's the test, and if the boards pass, you got yourself a process problem. Even if they are crappy boards on the edge of failing the test, your supplier doesn't have to take them back. You have to live with them until you change you supplier or spec, or both.

The quick and dirty solderability test that I use on the floor involves a vice grip. Grab the thing that ain't soldering and dunk it in the pot. Give the scientiffic two-count while its under. Pull it out and give it a look-see. Did it take solder? No? Dunk it again for the five count. IF it took solder without any flux, it's solderable. If it didn't, Give it some flux and repeat the two and five counts. With flux and a two count, I'd call it acceptable, but I'd get it quantified on a wetting balance. With flux and five count and still no solder, get the whole lot of parts off the floor and off to a wetting balance for some real data. Now I do this for parts; aint never done it for baords, but I believe the same principle would apply.

Good luck.

reply »

Earl Moon

#11188

Re: Wave Solder Problems - VIA HOLES | 4 June, 1999

| I'm encountering a new problem at my new company that I haven't encountered before in my past life - and that's Wave Soldering VIA holes. | | We've been getting a rash of defects that we call in this company, "insufficient solder in VIA hole." These defects result in failures at ICT. Some of our PCB's have over a thousand (.013" dia.?) holes, and yes, they're plated-through. | | I've checked for everything required to make a solder joint - flux, heat, and sufficient solder contact and dwell time. Every other joint looked excellent. Other PTH's, such as axial and radial parts' holes, had excellent solder fillets and great top-side wetting. Even the 0603's soldered nicely.....so, it lead me to one conclusion...POOR PCB QUALITY. | | My theory is that there is bad or insuffient copper plating in these VIA hole plated barrels, and as a result, solderability is compromised. I know it isn't a PROCESS PROBLEM (even though our manufacturing supervisors LOVE to think so), based on all the other indicators that I've described above. After all, solderability of your boards and parts is half the battle. If my theory is correct, what do i need to do to check solderability of these things? | | | Oh great WAVE SOLDER GURUS of this forum, please help me either confirm or dispute this theory!! |

reply »

Tony

#11189

Re: Wave Solder Problems - VIA HOLES | 4 June, 1999

| I'm encountering a new problem at my new company that I haven't encountered before in my past life - and that's Wave Soldering VIA holes. | | We've been getting a rash of defects that we call in this company, "insufficient solder in VIA hole." These defects result in failures at ICT. Some of our PCB's have over a thousand (.013" dia.?) holes, and yes, they're plated-through. | | I've checked for everything required to make a solder joint - flux, heat, and sufficient solder contact and dwell time. Every other joint looked excellent. Other PTH's, such as axial and radial parts' holes, had excellent solder fillets and great top-side wetting. Even the 0603's soldered nicely.....so, it lead me to one conclusion...POOR PCB QUALITY. | | My theory is that there is bad or insuffient copper plating in these VIA hole plated barrels, and as a result, solderability is compromised. I know it isn't a PROCESS PROBLEM (even though our manufacturing supervisors LOVE to think so), based on all the other indicators that I've described above. After all, solderability of your boards and parts is half the battle. If my theory is correct, what do i need to do to check solderability of these things? | | | Oh great WAVE SOLDER GURUS of this forum, please help me either confirm or dispute this theory!

C.K.

here is a quick fix that I implemented in my process..

OPEN APERTURES for your vias ON YOUR STENCIL AND PLUG YOUR VIAs DURING SMT PROCESS..

now this actually worked for my board, we had vias that were not soldering at wave.

Good LUCK..

reply »

Earl Moon

#11190

Re: Wave Solder Problems - VIA HOLES | 4 June, 1999

| I'm encountering a new problem at my new company that I haven't encountered before in my past life - and that's Wave Soldering VIA holes. | | We've been getting a rash of defects that we call in this company, "insufficient solder in VIA hole." These defects result in failures at ICT. Some of our PCB's have over a thousand (.013" dia.?) holes, and yes, they're plated-through. | | I've checked for everything required to make a solder joint - flux, heat, and sufficient solder contact and dwell time. Every other joint looked excellent. Other PTH's, such as axial and radial parts' holes, had excellent solder fillets and great top-side wetting. Even the 0603's soldered nicely.....so, it lead me to one conclusion...POOR PCB QUALITY. | | My theory is that there is bad or insuffient copper plating in these VIA hole plated barrels, and as a result, solderability is compromised. I know it isn't a PROCESS PROBLEM (even though our manufacturing supervisors LOVE to think so), based on all the other indicators that I've described above. After all, solderability of your boards and parts is half the battle. If my theory is correct, what do i need to do to check solderability of these things? | | | Oh great WAVE SOLDER GURUS of this forum, please help me either confirm or dispute this theory!! | I tried, unsuccessfully, to post before with a picture or two. How do you do that?

My message concerned difficulties with higher aspect ratio plated through holes. Those holes, exceeding 6:1, as an example, often will not solder wet throughout - no matter their diameter, wetability, wave pressure, flux effectiveness, or capillary activity. Also, I often have found solder mask, not fully stripped off pads and out of holes, to be a problem.

Earl Moon

reply »

JohnW

#11191

Re: Wave Solder Problems - VIA HOLES | 4 June, 1999

| | | I'm encountering a new problem at my new company that I haven't encountered before in my past life - and that's Wave Soldering VIA holes. | | | | | | We've been getting a rash of defects that we call in this company, "insufficient solder in VIA hole." These defects result in failures at ICT. Some of our PCB's have over a thousand (.013" dia.?) holes, and yes, they're plated-through. | | | | | | I've checked for everything required to make a solder joint - flux, heat, and sufficient solder contact and dwell time. Every other joint looked excellent. Other PTH's, such as axial and radial parts' holes, had excellent solder fillets and great top-side wetting. Even the 0603's soldered nicely.....so, it lead me to one conclusion...POOR PCB QUALITY. | | | | | | My theory is that there is bad or insuffient copper plating in these VIA hole plated barrels, and as a result, solderability is compromised. I know it isn't a PROCESS PROBLEM (even though our manufacturing supervisors LOVE to think so), based on all the other indicators that I've described above. After all, solderability of your boards and parts is half the battle. If my theory is correct, what do i need to do to check solderability of these things? | | | | | | | | | Oh great WAVE SOLDER GURUS of this forum, please help me either confirm or dispute this theory!! | | | | | | | CK: You�ve sold me. It sounds like an in-bound material problem, but before we go into that: | | | | 1 I�ll buy the heat, sufficient solder contact, and dwell time, but how do know that you�re fluxing the vias properly? Are you getting flux on the top side of the board? | | 2 How do you know the vias are supposed to be soldered, other than some techs in ICT whining about not getting good vacuum? | | 3 Will solder flow through a 13 mil diameter hole? Or is the surface tension of solder too great? | | | | OK let�s talk about your board: | | | | 1 Is this new problem new to you and new to your new company? | | 2 What is the history of this design? (is this a new product)? | | 3 How widespread is the problem? | | 4 Is the failed item from a single manufacturer or from various sources? | | 5 Is the failed item from a single lot or from various lots? | | 6 Why aren�t you having your fab supplier plug the vias? Then, this is just a discussion on whether you should be plugging top or bottom side. | | 7 What kind of solder mask is on the boards? Has someone changed the solder mask? Was the solder mask used to plug the vias previously? | | 8 What kind of solderability protection is on the vias? | | 9 How are these boards checked for solderability at incoming? | | 10 When you look at a section of the via, what kind of wetting do you get? | | 11 Has the manufacturer been contacted, provided samples of failed items, and provided a response? | | 12 So, when the manufacturing supervisors squirt flux on the vias, load-up a 800 watt iron with solder, and solder the vias; can they get good solder flow? | | | | Dave F | | | | | | | | Geez, those test guys are always whining about via holes, aren't they? I even had one test guy go over to our finals/add-on department and instruct everone to look for unfilled vias and fill them by hand! Without consulting the area manager or engineer! Just took matters into his own hands. I'll tell ya, that little trick put him right at the top of my Christmas List. | | The other guys pretty much coverd all the bases on why vias aren't filling - gotta narrow it down to a specific lot/vendor/source if it's an incoming material problem. One thing I have encountered in the past, however, that hasn't been mentioned is adhesive residue in the holes. If the bottomside operators get a bad glue print (or dispense) and clean off the board, they get the surface free of adhesive, but don't always check the holes. When you're wiping or squeegeeing glue off the board, it likes to sneak into those holes and hide there, silently waiting to hose up your soldering process. If there is adhesive in there, you should be able to see a light residue under the scope. Just a tinge of color. Given the contamination theory, the boards could have contaminants in there from the fab house, too. | | Now them thar holes are pretty small and tough to get flux/solder into. Air environments make trying to get solder in the hole even tougher, since all these nasty little pieces of microdross are sitting on top of the wave just trying to block the flow of the nice solder. | | And even though you get good flux coverage across the board, it doesn't necessarily mean that the flux is penetrating the tiny little vias. Good ol' foam used to penetrate the vias well, since it's surface tension was always getting busted up. Ultrasonics make nice tiny little droplets that will penetrate well, but pressure sprays can have some difficulty, since their drops are bigger (just opened the door for Steve Skinner on that one, didn't I?). To see if the flux is penetrating, give it the old fax paper test. Sandwich the paper between two raw cards and flux them. You should see the penetration on the fax paper when you pull the sandwich apart. If you don't, you may just have to adjust your fluxing parameters - more pressure or more air flow to enhace the spray. I don't know what kind of fluxer you're running, but when we were evaluating the Jet Fluxer, this was one of the issues we found. And the only solution on that model was more pressure - I think we had to go to 20 psi to get good topside wetting. Needless to say, we "Opt"ed for a different machine. | | As for checking for solderability, the first place to go is your procurement spec, since that the contract that binds you and your suppliers. Your company may have their own spec, or they may use an IPC standard. The spec should call out a test method and a pass/fail criteria. It may seem to be a really STUPID, USELESS, OUTDATED test, like something with RA flux and 5 seconds dwell time, because it never got updated with the rest of the world, but unfortunately, them's the breaks. Or it may be reasonable. In any event, that's the test, and if the boards pass, you got yourself a process problem. Even if they are crappy boards on the edge of failing the test, your supplier doesn't have to take them back. You have to live with them until you change you supplier or spec, or both. | | The quick and dirty solderability test that I use on the floor involves a vice grip. Grab the thing that ain't soldering and dunk it in the pot. Give the scientiffic two-count while its under. Pull it out and give it a look-see. Did it take solder? No? Dunk it again for the five count. IF it took solder without any flux, it's solderable. If it didn't, Give it some flux and repeat the two and five counts. With flux and a two count, I'd call it acceptable, but I'd get it quantified on a wetting balance. With flux and five count and still no solder, get the whole lot of parts off the floor and off to a wetting balance for some real data. Now I do this for parts; aint never done it for baords, but I believe the same principle would apply. | | Good luck. | CK...

what ever happened to test points..???? I've actually had a test guy getting operator's to increase the amount of solder on a test point rather than change the dam pin...

Anyway's I'd basically be doing the same stuff that's above, I'm taking it that you will have ensured that your not getting a thin coating of resist in the via's from the board manufacturing process?? The only other thing I can throw up is the flux and the solid's content of it or the application of it. If the solid content is to high there is no whay it's going up the via's, equally if the spray fluxer aint producing a fine enough mist your never gonna get it there. The next step would proabably be an ultra sonic head..

JohnW

reply »

C.K.

#11192

Re: Wave Solder Problems - VIA HOLES | 4 June, 1999

| | | I'm encountering a new problem at my new company that I haven't encountered before in my past life - and that's Wave Soldering VIA holes. | | | | | | We've been getting a rash of defects that we call in this company, "insufficient solder in VIA hole." These defects result in failures at ICT. Some of our PCB's have over a thousand (.013" dia.?) holes, and yes, they're plated-through. | | | | | | I've checked for everything required to make a solder joint - flux, heat, and sufficient solder contact and dwell time. Every other joint looked excellent. Other PTH's, such as axial and radial parts' holes, had excellent solder fillets and great top-side wetting. Even the 0603's soldered nicely.....so, it lead me to one conclusion...POOR PCB QUALITY. | | | | | | My theory is that there is bad or insuffient copper plating in these VIA hole plated barrels, and as a result, solderability is compromised. I know it isn't a PROCESS PROBLEM (even though our manufacturing supervisors LOVE to think so), based on all the other indicators that I've described above. After all, solderability of your boards and parts is half the battle. If my theory is correct, what do i need to do to check solderability of these things? | | | | | | | | | Oh great WAVE SOLDER GURUS of this forum, please help me either confirm or dispute this theory!! | | | | | | | CK: You�ve sold me. It sounds like an in-bound material problem, but before we go into that: | | | | 1 I�ll buy the heat, sufficient solder contact, and dwell time, but how do know that you�re fluxing the vias properly? Are you getting flux on the top side of the board? | | 2 How do you know the vias are supposed to be soldered, other than some techs in ICT whining about not getting good vacuum? | | 3 Will solder flow through a 13 mil diameter hole? Or is the surface tension of solder too great? | | | | OK let�s talk about your board: | | | | 1 Is this new problem new to you and new to your new company? | | 2 What is the history of this design? (is this a new product)? | | 3 How widespread is the problem? | | 4 Is the failed item from a single manufacturer or from various sources? | | 5 Is the failed item from a single lot or from various lots? | | 6 Why aren�t you having your fab supplier plug the vias? Then, this is just a discussion on whether you should be plugging top or bottom side. | | 7 What kind of solder mask is on the boards? Has someone changed the solder mask? Was the solder mask used to plug the vias previously? | | 8 What kind of solderability protection is on the vias? | | 9 How are these boards checked for solderability at incoming? | | 10 When you look at a section of the via, what kind of wetting do you get? | | 11 Has the manufacturer been contacted, provided samples of failed items, and provided a response? | | 12 So, when the manufacturing supervisors squirt flux on the vias, load-up a 800 watt iron with solder, and solder the vias; can they get good solder flow? | | | | Dave F | | | | | | | | Geez, those test guys are always whining about via holes, aren't they? I even had one test guy go over to our finals/add-on department and instruct everone to look for unfilled vias and fill them by hand! Without consulting the area manager or engineer! Just took matters into his own hands. I'll tell ya, that little trick put him right at the top of my Christmas List. | | The other guys pretty much coverd all the bases on why vias aren't filling - gotta narrow it down to a specific lot/vendor/source if it's an incoming material problem. One thing I have encountered in the past, however, that hasn't been mentioned is adhesive residue in the holes. If the bottomside operators get a bad glue print (or dispense) and clean off the board, they get the surface free of adhesive, but don't always check the holes. When you're wiping or squeegeeing glue off the board, it likes to sneak into those holes and hide there, silently waiting to hose up your soldering process. If there is adhesive in there, you should be able to see a light residue under the scope. Just a tinge of color. Given the contamination theory, the boards could have contaminants in there from the fab house, too. | | Now them thar holes are pretty small and tough to get flux/solder into. Air environments make trying to get solder in the hole even tougher, since all these nasty little pieces of microdross are sitting on top of the wave just trying to block the flow of the nice solder. | | And even though you get good flux coverage across the board, it doesn't necessarily mean that the flux is penetrating the tiny little vias. Good ol' foam used to penetrate the vias well, since it's surface tension was always getting busted up. Ultrasonics make nice tiny little droplets that will penetrate well, but pressure sprays can have some difficulty, since their drops are bigger (just opened the door for Steve Skinner on that one, didn't I?). To see if the flux is penetrating, give it the old fax paper test. Sandwich the paper between two raw cards and flux them. You should see the penetration on the fax paper when you pull the sandwich apart. If you don't, you may just have to adjust your fluxing parameters - more pressure or more air flow to enhace the spray. I don't know what kind of fluxer you're running, but when we were evaluating the Jet Fluxer, this was one of the issues we found. And the only solution on that model was more pressure - I think we had to go to 20 psi to get good topside wetting. Needless to say, we "Opt"ed for a different machine. | | As for checking for solderability, the first place to go is your procurement spec, since that the contract that binds you and your suppliers. Your company may have their own spec, or they may use an IPC standard. The spec should call out a test method and a pass/fail criteria. It may seem to be a really STUPID, USELESS, OUTDATED test, like something with RA flux and 5 seconds dwell time, because it never got updated with the rest of the world, but unfortunately, them's the breaks. Or it may be reasonable. In any event, that's the test, and if the boards pass, you got yourself a process problem. Even if they are crappy boards on the edge of failing the test, your supplier doesn't have to take them back. You have to live with them until you change you supplier or spec, or both. | | The quick and dirty solderability test that I use on the floor involves a vice grip. Grab the thing that ain't soldering and dunk it in the pot. Give the scientiffic two-count while its under. Pull it out and give it a look-see. Did it take solder? No? Dunk it again for the five count. IF it took solder without any flux, it's solderable. If it didn't, Give it some flux and repeat the two and five counts. With flux and a two count, I'd call it acceptable, but I'd get it quantified on a wetting balance. With flux and five count and still no solder, get the whole lot of parts off the floor and off to a wetting balance for some real data. Now I do this for parts; aint never done it for baords, but I believe the same principle would apply. | | Good luck. |

reply »

C.K.

#11193

Re: Thanks. | 4 June, 1999

| | | | Geez, those test guys are always whining about via holes, aren't they? I even had one test guy go over to our finals/add-on department and instruct everone to look for unfilled vias and fill them by hand! Without consulting the area manager or engineer! Just took matters into his own hands. I'll tell ya, that little trick put him right at the top of my Christmas List. | | | | The other guys pretty much coverd all the bases on why vias aren't filling - gotta narrow it down to a specific lot/vendor/source if it's an incoming material problem. One thing I have encountered in the past, however, that hasn't been mentioned is adhesive residue in the holes. If the bottomside operators get a bad glue print (or dispense) and clean off the board, they get the surface free of adhesive, but don't always check the holes. When you're wiping or squeegeeing glue off the board, it likes to sneak into those holes and hide there, silently waiting to hose up your soldering process. If there is adhesive in there, you should be able to see a light residue under the scope. Just a tinge of color. Given the contamination theory, the boards could have contaminants in there from the fab house, too. | | | | Now them thar holes are pretty small and tough to get flux/solder into. Air environments make trying to get solder in the hole even tougher, since all these nasty little pieces of microdross are sitting on top of the wave just trying to block the flow of the nice solder. | | | | And even though you get good flux coverage across the board, it doesn't necessarily mean that the flux is penetrating the tiny little vias. Good ol' foam used to penetrate the vias well, since it's surface tension was always getting busted up. Ultrasonics make nice tiny little droplets that will penetrate well, but pressure sprays can have some difficulty, since their drops are bigger (just opened the door for Steve Skinner on that one, didn't I?). To see if the flux is penetrating, give it the old fax paper test. Sandwich the paper between two raw cards and flux them. You should see the penetration on the fax paper when you pull the sandwich apart. If you don't, you may just have to adjust your fluxing parameters - more pressure or more air flow to enhace the spray. I don't know what kind of fluxer you're running, but when we were evaluating the Jet Fluxer, this was one of the issues we found. And the only solution on that model was more pressure - I think we had to go to 20 psi to get good topside wetting. Needless to say, we "Opt"ed for a different machine. | | | | As for checking for solderability, the first place to go is your procurement spec, since that the contract that binds you and your suppliers. Your company may have their own spec, or they may use an IPC standard. The spec should call out a test method and a pass/fail criteria. It may seem to be a really STUPID, USELESS, OUTDATED test, like something with RA flux and 5 seconds dwell time, because it never got updated with the rest of the world, but unfortunately, them's the breaks. Or it may be reasonable. In any event, that's the test, and if the boards pass, you got yourself a process problem. Even if they are crappy boards on the edge of failing the test, your supplier doesn't have to take them back. You have to live with them until you change you supplier or spec, or both. | | | | The quick and dirty solderability test that I use on the floor involves a vice grip. Grab the thing that ain't soldering and dunk it in the pot. Give the scientiffic two-count while its under. Pull it out and give it a look-see. Did it take solder? No? Dunk it again for the five count. IF it took solder without any flux, it's solderable. If it didn't, Give it some flux and repeat the two and five counts. With flux and a two count, I'd call it acceptable, but I'd get it quantified on a wetting balance. With flux and five count and still no solder, get the whole lot of parts off the floor and off to a wetting balance for some real data. Now I do this for parts; aint never done it for baords, but I believe the same principle would apply. | | | | Good luck. | | | |

Hiya Chrys:

Thanks again for your advice. to answer a few of your questions, i do have a $1k "thermal-fax-paper-sandwiched-between-2-boards gizmo" called a flux-o-meter (made by ECD) and that's how i tested my flux. Yeah, i know, I felt guilty for spending a thousand bucks such a simple little gizmo too... Got pretty decent top-side penetration too. Actually, I use a PH-sensitive paper now since we're now using the water-based alpha nr310b. My Optiflux paramters are: 7.0 PSI reservoir pressure, and 12.0 IPS traverse speed, 4 Inch spray patern, and 4.0 IPM conveyor speed...are your settings similar?

Upon further investigation and some asking around, I found out that this problem has happened before, and the cause was operators haphhazardly alcohol-wiping a misglued board, thus pushing the adhesive into those 13 mil via holes...... long term solution for us will be to get a good board cleaner (probably ultrasonic/alcohol type.)

...but if this problem continues even with no glue in via's, my last resort will be to try that IPC 1960's solderability test that you describe above...yikes...do they actually still make Rosin-Active stuff???? Sounds like something a "lead-head from way-back-when" would do.

Hahaha..I deal with a self-proclaimed resident wave solder guru here who describes himself as a "lead-head-from-way-back-when." ..he "attempted" to give this rookie a "lesson" in wave soldering... Didn't really pay much attention to him either..

CK

reply »

Brian Wycoff

#11194

Re: Thanks. | 7 June, 1999

| | | | | | | Geez, those test guys are always whining about via holes, aren't they? I even had one test guy go over to our finals/add-on department and instruct everone to look for unfilled vias and fill them by hand! Without consulting the area manager or engineer! Just took matters into his own hands. I'll tell ya, that little trick put him right at the top of my Christmas List. | | | | | | The other guys pretty much coverd all the bases on why vias aren't filling - gotta narrow it down to a specific lot/vendor/source if it's an incoming material problem. One thing I have encountered in the past, however, that hasn't been mentioned is adhesive residue in the holes. If the bottomside operators get a bad glue print (or dispense) and clean off the board, they get the surface free of adhesive, but don't always check the holes. When you're wiping or squeegeeing glue off the board, it likes to sneak into those holes and hide there, silently waiting to hose up your soldering process. If there is adhesive in there, you should be able to see a light residue under the scope. Just a tinge of color. Given the contamination theory, the boards could have contaminants in there from the fab house, too. | | | | | | Now them thar holes are pretty small and tough to get flux/solder into. Air environments make trying to get solder in the hole even tougher, since all these nasty little pieces of microdross are sitting on top of the wave just trying to block the flow of the nice solder. | | | | | | And even though you get good flux coverage across the board, it doesn't necessarily mean that the flux is penetrating the tiny little vias. Good ol' foam used to penetrate the vias well, since it's surface tension was always getting busted up. Ultrasonics make nice tiny little droplets that will penetrate well, but pressure sprays can have some difficulty, since their drops are bigger (just opened the door for Steve Skinner on that one, didn't I?). To see if the flux is penetrating, give it the old fax paper test. Sandwich the paper between two raw cards and flux them. You should see the penetration on the fax paper when you pull the sandwich apart. If you don't, you may just have to adjust your fluxing parameters - more pressure or more air flow to enhace the spray. I don't know what kind of fluxer you're running, but when we were evaluating the Jet Fluxer, this was one of the issues we found. And the only solution on that model was more pressure - I think we had to go to 20 psi to get good topside wetting. Needless to say, we "Opt"ed for a different machine. | | | | | | As for checking for solderability, the first place to go is your procurement spec, since that the contract that binds you and your suppliers. Your company may have their own spec, or they may use an IPC standard. The spec should call out a test method and a pass/fail criteria. It may seem to be a really STUPID, USELESS, OUTDATED test, like something with RA flux and 5 seconds dwell time, because it never got updated with the rest of the world, but unfortunately, them's the breaks. Or it may be reasonable. In any event, that's the test, and if the boards pass, you got yourself a process problem. Even if they are crappy boards on the edge of failing the test, your supplier doesn't have to take them back. You have to live with them until you change you supplier or spec, or both. | | | | | | The quick and dirty solderability test that I use on the floor involves a vice grip. Grab the thing that ain't soldering and dunk it in the pot. Give the scientiffic two-count while its under. Pull it out and give it a look-see. Did it take solder? No? Dunk it again for the five count. IF it took solder without any flux, it's solderable. If it didn't, Give it some flux and repeat the two and five counts. With flux and a two count, I'd call it acceptable, but I'd get it quantified on a wetting balance. With flux and five count and still no solder, get the whole lot of parts off the floor and off to a wetting balance for some real data. Now I do this for parts; aint never done it for baords, but I believe the same principle would apply. | | | | | | Good luck. | | | | | | | | | | Hiya Chrys: | | Thanks again for your advice. to answer a few of your questions, i do have a $1k "thermal-fax-paper-sandwiched-between-2-boards gizmo" called a flux-o-meter (made by ECD) and that's how i tested my flux. Yeah, i know, I felt guilty for spending a thousand bucks such a simple little gizmo too... Got pretty decent top-side penetration too. Actually, I use a PH-sensitive paper now since we're now using the water-based alpha nr310b. My Optiflux paramters are: 7.0 PSI reservoir pressure, and 12.0 IPS traverse speed, 4 Inch spray patern, and 4.0 IPM conveyor speed...are your settings similar? | | Upon further investigation and some asking around, I found out that this problem has happened before, and the cause was operators haphhazardly alcohol-wiping a misglued board, thus pushing the adhesive into those 13 mil via holes...... long term solution for us will be to get a good board cleaner (probably ultrasonic/alcohol type.) | | ...but if this problem continues even with no glue in via's, my last resort will be to try that IPC 1960's solderability test that you describe above...yikes...do they actually still make Rosin-Active stuff???? Sounds like something a "lead-head from way-back-when" would do. | | Hahaha..I deal with a self-proclaimed resident wave solder guru here who describes himself as a "lead-head-from-way-back-when." ..he "attempted" to give this rookie a "lesson" in wave soldering... | Didn't really pay much attention to him either.. | | | CK | I had one of thoise guys who had 40 years wave soldering experience too.....or was it one years experience 40 times over... Anyway, Check the workmanship standard you are using. The JSTD-001 ( and the referenced IPC-610B) do not require fill of via holes. It is not the best idea in the world for designers to use vias as test points. All of the other ideas are good ones, but alos try to push it back to the designers when relaying out the board. Then put it into a Design for Manufacturability/Testability specification and force them to stay away from that.

Brian

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#11195

Re: Wave Solder Problems - VIA HOLES | 7 June, 1999

| I'm encountering a new problem at my new company that I haven't encountered before in my past life - and that's Wave Soldering VIA holes. | | We've been getting a rash of defects that we call in this company, "insufficient solder in VIA hole." These defects result in failures at ICT. Some of our PCB's have over a thousand (.013" dia.?) holes, and yes, they're plated-through. | | I've checked for everything required to make a solder joint - flux, heat, and sufficient solder contact and dwell time. Every other joint looked excellent. Other PTH's, such as axial and radial parts' holes, had excellent solder fillets and great top-side wetting. Even the 0603's soldered nicely.....so, it lead me to one conclusion...POOR PCB QUALITY. | | My theory is that there is bad or insuffient copper plating in these VIA hole plated barrels, and as a result, solderability is compromised. I know it isn't a PROCESS PROBLEM (even though our manufacturing supervisors LOVE to think so), based on all the other indicators that I've described above. After all, solderability of your boards and parts is half the battle. If my theory is correct, what do i need to do to check solderability of these things? | | | Oh great WAVE SOLDER GURUS of this forum, please help me either confirm or dispute this theory!! | Hey CK,

Posted my answer to your question here instead of burying it down below.

My Opti paramters:

Tank pressure - 2.2 tp 2.5 psi Traverse speed - 10 in/sec Connveyor speed - 4.5 to 6.0 ft/min. Spray width - 4.3 in on one machine; 4.5 on the other.

Here's what I did to get those spray width numbers (4 in is the system's default):

Shut off the air, pop the hood, and pull the head out to where you can see it, touch it, etc.

Loosen the set screws that hold the applicator in place, so you can slide it back and forth. You don't have to turn them completely out; just loosen them so you can slide the applicator.

Manually turn on the flux flow and ultrasonics.

WORD OF CAUTION - DON'T HAVE YOUR FACE DIRECTLY OVER THE SPRAY HEAD HERE, UNLESS YOU WANT TO GET FLUXED.

Gently move the applicator back towrds the horn. tap tap tap, real nice and gentle-like, until you get the widest possible spray pattern across the head. At first contact it will be somewhat skinny, then as you push it into the horn, it will spread, until you've pushed it too far, where it will get thin again. Optimum is a spray that extends all the way across, except for about an 1/8 inch at each edge.

Got that nice spray? Stop right there. Turn the flow off. Set the set screws. Turn the flow back on to make sure the head didn't move whilst you were turning those screws. Repeat if necessary.

So now you've got it perfect. Get a set of feeler gauges and check that gap. (One of my fluxer heads optimized at a 14 thou gap; the other one optimized at a 17 thou gap.)

Rip that feeler gauge from the set. You're sacrificing it for a higher purpose. Put a handle on it and chain it to the outside of the machine. This is your new "wonder tool" that you cannot afford to lose. I'm not kidding. The gap is critical.

Now, when anyone does maintenance on the fluxer, they will use this tool to set the gap between the head and the horn. It is a very critical gap. It determines the width of your spray pattern. USI's directions tell you to push the applicator against the horn until it "just lightly touches." That term meant completely different things to me and each of my techs. The "wonder tool" eliminated any and all interpretations of this terminology.

Now your gap is locked down as a constant, so your spray width will always be a constant (as opposed to being in a constant state of flux - yuk, yuk). No overlap that gives extra flux to spatter at the wave; no underlap or skips to give poor solderability. Most of the process control battle has been won.

But you still gotta see what this translates to in width at the actual circuit board. And since the pattern spreads after it leaves the spray head, it depends on the distance that the head is from the board.

Turn your air back on; close the hood, and return to manual operation.

So set the fluxer to do a single pass. Get your high-falutin' flux-o-meter (or glass plate for us "lead-heads from a way-back-when") and run it through. Measure the pattern width. Program it in the fluxer configuration parameters, and you're home free.

If your spray pattern doesn't come up in the 4 - 5 inch range, check the orifices on the air assists. They can get obstucted with flux solids if your operators let the solvent tank run empty. If they are clean, check the height of the fluxer itself. You can move it closer or farther away by turning the mounting nuts for the pan on the fluxer. Nothing against Electrovert's field service guys, but some of them do not share my intense love of precision setups for process control. I usually perform several setup tweaks after the installation is complete. I get a little A-R about setups sometimes.

This might sound complicated when I describe it in writing, but it's really very simple. Takes about a half hour. And is totally worth it.

Happy fluxing,

Chrys

reply »

Steve Skinner

#11196

Re: Wave Solder Problems - VIA HOLES | 8 June, 1999

| | | I'm encountering a new problem at my new company that I haven't encountered before in my past life - and that's Wave Soldering VIA holes. | | | | | | We've been getting a rash of defects that we call in this company, "insufficient solder in VIA hole." These defects result in failures at ICT. Some of our PCB's have over a thousand (.013" dia.?) holes, and yes, they're plated-through. | | | | | | I've checked for everything required to make a solder joint - flux, heat, and sufficient solder contact and dwell time. Every other joint looked excellent. Other PTH's, such as axial and radial parts' holes, had excellent solder fillets and great top-side wetting. Even the 0603's soldered nicely.....so, it lead me to one conclusion...POOR PCB QUALITY. | | | | | | My theory is that there is bad or insuffient copper plating in these VIA hole plated barrels, and as a result, solderability is compromised. I know it isn't a PROCESS PROBLEM (even though our manufacturing supervisors LOVE to think so), based on all the other indicators that I've described above. After all, solderability of your boards and parts is half the battle. If my theory is correct, what do i need to do to check solderability of these things? | | | | | | | | | Oh great WAVE SOLDER GURUS of this forum, please help me either confirm or dispute this theory!! | | | | | | | CK: You�ve sold me. It sounds like an in-bound material problem, but before we go into that: | | | | 1 I�ll buy the heat, sufficient solder contact, and dwell time, but how do know that you�re fluxing the vias properly? Are you getting flux on the top side of the board? | | 2 How do you know the vias are supposed to be soldered, other than some techs in ICT whining about not getting good vacuum? | | 3 Will solder flow through a 13 mil diameter hole? Or is the surface tension of solder too great? | | | | OK let�s talk about your board: | | | | 1 Is this new problem new to you and new to your new company? | | 2 What is the history of this design? (is this a new product)? | | 3 How widespread is the problem? | | 4 Is the failed item from a single manufacturer or from various sources? | | 5 Is the failed item from a single lot or from various lots? | | 6 Why aren�t you having your fab supplier plug the vias? Then, this is just a discussion on whether you should be plugging top or bottom side. | | 7 What kind of solder mask is on the boards? Has someone changed the solder mask? Was the solder mask used to plug the vias previously? | | 8 What kind of solderability protection is on the vias? | | 9 How are these boards checked for solderability at incoming? | | 10 When you look at a section of the via, what kind of wetting do you get? | | 11 Has the manufacturer been contacted, provided samples of failed items, and provided a response? | | 12 So, when the manufacturing supervisors squirt flux on the vias, load-up a 800 watt iron with solder, and solder the vias; can they get good solder flow? | | | | Dave F | | | | | | | | Geez, those test guys are always whining about via holes, aren't they? I even had one test guy go over to our finals/add-on department and instruct everone to look for unfilled vias and fill them by hand! Without consulting the area manager or engineer! Just took matters into his own hands. I'll tell ya, that little trick put him right at the top of my Christmas List. | | The other guys pretty much coverd all the bases on why vias aren't filling - gotta narrow it down to a specific lot/vendor/source if it's an incoming material problem. One thing I have encountered in the past, however, that hasn't been mentioned is adhesive residue in the holes. If the bottomside operators get a bad glue print (or dispense) and clean off the board, they get the surface free of adhesive, but don't always check the holes. When you're wiping or squeegeeing glue off the board, it likes to sneak into those holes and hide there, silently waiting to hose up your soldering process. If there is adhesive in there, you should be able to see a light residue under the scope. Just a tinge of color. Given the contamination theory, the boards could have contaminants in there from the fab house, too. | | Now them thar holes are pretty small and tough to get flux/solder into. Air environments make trying to get solder in the hole even tougher, since all these nasty little pieces of microdross are sitting on top of the wave just trying to block the flow of the nice solder. | | And even though you get good flux coverage across the board, it doesn't necessarily mean that the flux is penetrating the tiny little vias. Good ol' foam used to penetrate the vias well, since it's surface tension was always getting busted up. Ultrasonics make nice tiny little droplets that will penetrate well, but pressure sprays can have some difficulty, since their drops are bigger (just opened the door for Steve Skinner on that one, didn't I?). To see if the flux is penetrating, give it the old fax paper test. Sandwich the paper between two raw cards and flux them. You should see the penetration on the fax paper when you pull the sandwich apart. If you don't, you may just have to adjust your fluxing parameters - more pressure or more air flow to enhace the spray. I don't know what kind of fluxer you're running, but when we were evaluating the Jet Fluxer, this was one of the issues we found. And the only solution on that model was more pressure - I think we had to go to 20 psi to get good topside wetting. Needless to say, we "Opt"ed for a different machine. | | As for checking for solderability, the first place to go is your procurement spec, since that the contract that binds you and your suppliers. Your company may have their own spec, or they may use an IPC standard. The spec should call out a test method and a pass/fail criteria. It may seem to be a really STUPID, USELESS, OUTDATED test, like something with RA flux and 5 seconds dwell time, because it never got updated with the rest of the world, but unfortunately, them's the breaks. Or it may be reasonable. In any event, that's the test, and if the boards pass, you got yourself a process problem. Even if they are crappy boards on the edge of failing the test, your supplier doesn't have to take them back. You have to live with them until you change you supplier or spec, or both. | | The quick and dirty solderability test that I use on the floor involves a vice grip. Grab the thing that ain't soldering and dunk it in the pot. Give the scientiffic two-count while its under. Pull it out and give it a look-see. Did it take solder? No? Dunk it again for the five count. IF it took solder without any flux, it's solderable. If it didn't, Give it some flux and repeat the two and five counts. With flux and a two count, I'd call it acceptable, but I'd get it quantified on a wetting balance. With flux and five count and still no solder, get the whole lot of parts off the floor and off to a wetting balance for some real data. Now I do this for parts; aint never done it for baords, but I believe the same principle would apply. | | Good luck. |

reply »

Steve Skinner

#11197

Re: Wave Solder Problems - VIA HOLES | 8 June, 1999

| | | I'm encountering a new problem at my new company that I haven't encountered before in my past life - and that's Wave Soldering VIA holes. | | | | | | We've been getting a rash of defects that we call in this company, "insufficient solder in VIA hole." These defects result in failures at ICT. Some of our PCB's have over a thousand (.013" dia.?) holes, and yes, they're plated-through. | | | | | | I've checked for everything required to make a solder joint - flux, heat, and sufficient solder contact and dwell time. Every other joint looked excellent. Other PTH's, such as axial and radial parts' holes, had excellent solder fillets and great top-side wetting. Even the 0603's soldered nicely.....so, it lead me to one conclusion...POOR PCB QUALITY. | | | | | | My theory is that there is bad or insuffient copper plating in these VIA hole plated barrels, and as a result, solderability is compromised. I know it isn't a PROCESS PROBLEM (even though our manufacturing supervisors LOVE to think so), based on all the other indicators that I've described above. After all, solderability of your boards and parts is half the battle. If my theory is correct, what do i need to do to check solderability of these things? | | | | | | | | | Oh great WAVE SOLDER GURUS of this forum, please help me either confirm or dispute this theory!! | | | | | | | CK: You�ve sold me. It sounds like an in-bound material problem, but before we go into that: | | | | 1 I�ll buy the heat, sufficient solder contact, and dwell time, but how do know that you�re fluxing the vias properly? Are you getting flux on the top side of the board? | | 2 How do you know the vias are supposed to be soldered, other than some techs in ICT whining about not getting good vacuum? | | 3 Will solder flow through a 13 mil diameter hole? Or is the surface tension of solder too great? | | | | OK let�s talk about your board: | | | | 1 Is this new problem new to you and new to your new company? | | 2 What is the history of this design? (is this a new product)? | | 3 How widespread is the problem? | | 4 Is the failed item from a single manufacturer or from various sources? | | 5 Is the failed item from a single lot or from various lots? | | 6 Why aren�t you having your fab supplier plug the vias? Then, this is just a discussion on whether you should be plugging top or bottom side. | | 7 What kind of solder mask is on the boards? Has someone changed the solder mask? Was the solder mask used to plug the vias previously? | | 8 What kind of solderability protection is on the vias? | | 9 How are these boards checked for solderability at incoming? | | 10 When you look at a section of the via, what kind of wetting do you get? | | 11 Has the manufacturer been contacted, provided samples of failed items, and provided a response? | | 12 So, when the manufacturing supervisors squirt flux on the vias, load-up a 800 watt iron with solder, and solder the vias; can they get good solder flow? | | | | Dave F | | | | | | | | Geez, those test guys are always whining about via holes, aren't they? I even had one test guy go over to our finals/add-on department and instruct everone to look for unfilled vias and fill them by hand! Without consulting the area manager or engineer! Just took matters into his own hands. I'll tell ya, that little trick put him right at the top of my Christmas List. | | The other guys pretty much coverd all the bases on why vias aren't filling - gotta narrow it down to a specific lot/vendor/source if it's an incoming material problem. One thing I have encountered in the past, however, that hasn't been mentioned is adhesive residue in the holes. If the bottomside operators get a bad glue print (or dispense) and clean off the board, they get the surface free of adhesive, but don't always check the holes. When you're wiping or squeegeeing glue off the board, it likes to sneak into those holes and hide there, silently waiting to hose up your soldering process. If there is adhesive in there, you should be able to see a light residue under the scope. Just a tinge of color. Given the contamination theory, the boards could have contaminants in there from the fab house, too. | | Now them thar holes are pretty small and tough to get flux/solder into. Air environments make trying to get solder in the hole even tougher, since all these nasty little pieces of microdross are sitting on top of the wave just trying to block the flow of the nice solder. | | And even though you get good flux coverage across the board, it doesn't necessarily mean that the flux is penetrating the tiny little vias. Good ol' foam used to penetrate the vias well, since it's surface tension was always getting busted up. Ultrasonics make nice tiny little droplets that will penetrate well, but pressure sprays can have some difficulty, since their drops are bigger (just opened the door for Steve Skinner on that one, didn't I?). To see if the flux is penetrating, give it the old fax paper test. Sandwich the paper between two raw cards and flux them. You should see the penetration on the fax paper when you pull the sandwich apart. If you don't, you may just have to adjust your fluxing parameters - more pressure or more air flow to enhace the spray. I don't know what kind of fluxer you're running, but when we were evaluating the Jet Fluxer, this was one of the issues we found. And the only solution on that model was more pressure - I think we had to go to 20 psi to get good topside wetting. Needless to say, we "Opt"ed for a different machine. | | As for checking for solderability, the first place to go is your procurement spec, since that the contract that binds you and your suppliers. Your company may have their own spec, or they may use an IPC standard. The spec should call out a test method and a pass/fail criteria. It may seem to be a really STUPID, USELESS, OUTDATED test, like something with RA flux and 5 seconds dwell time, because it never got updated with the rest of the world, but unfortunately, them's the breaks. Or it may be reasonable. In any event, that's the test, and if the boards pass, you got yourself a process problem. Even if they are crappy boards on the edge of failing the test, your supplier doesn't have to take them back. You have to live with them until you change you supplier or spec, or both. | | The quick and dirty solderability test that I use on the floor involves a vice grip. Grab the thing that ain't soldering and dunk it in the pot. Give the scientiffic two-count while its under. Pull it out and give it a look-see. Did it take solder? No? Dunk it again for the five count. IF it took solder without any flux, it's solderable. If it didn't, Give it some flux and repeat the two and five counts. With flux and a two count, I'd call it acceptable, but I'd get it quantified on a wetting balance. With flux and five count and still no solder, get the whole lot of parts off the floor and off to a wetting balance for some real data. Now I do this for parts; aint never done it for baords, but I believe the same principle would apply. | | Good luck. | Yes you certainly did open the door for me. I will argue that a pressure spray will penetrate the vias. A reciprocating spray will do a much better job than a stationary spray head.

Ultra sonics should do the job if it is the reciprocating type.

I am tired of hearing the myth of droplet size as it relates to penetration in a pressure spray versus a non pressure spray.

What do you work for one of the ultrasonics comapanies?

With regard to soldering vias. Proper topside temp is critical as is proper flux penetration of the via holes. The activity level of the flux may be playing a role in this also.

It is always easy to blame bare board suppliers and many have made themselves prime targets. One thing I would suggest trying is if you have a turbulent wave on the machine try running it for some tests.

Foam fluxers will not always do the trick and if you are spraying you should be getting penetration of the vias. The thermo fax paper test should confirm. I suspect that if you are getting good topside fill on the rest of the board, that you are getting flux penetrating the vias.

Try the chip wave if you have one. Good luck.

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reflow oven profiler