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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Closer lead more soldering bridge by using spray flux

Wister

#11138

Closer lead more soldering bridge by using spray flux | 8 June, 1999

Hi,my master How to iron out such soldering bridge with below conditions: 1.The component(Harness)lead pitch is 2.0mm,the lead length is 3.2mm. 2.PCB width is 1.6mm.Pad size is 1.65mm.Its a single copper PCB 3.using spraying fluxer and no-clean flux(Alcoho-base,solid content is 3.0%) After go though the wave solder machine,The DPM of soldering bridge on this component would be 12000, I try to cut the lead length from 3.2mm to 2.7mm,it sharply decreased to 3300. Our target is 400DPM. How to reduce the soldering bridge on such "fine" pitch component? Could you please kind enough to give me some suggestions? Thanks, Wister

reply »

#11139

Re: Closer lead more soldering bridge by using spray flux | 8 June, 1999

| Hi,my master | How to iron out such soldering bridge with below conditions: | 1.The component(Harness)lead pitch is 2.0mm,the lead length is 3.2mm. | 2.PCB width is 1.6mm.Pad size is 1.65mm.Its a single copper PCB | 3.using spraying fluxer and no-clean flux(Alcoho-base,solid content is 3.0%) | After go though the wave solder machine,The DPM of soldering bridge on this component would be 12000, I try to cut the lead length from 3.2mm to 2.7mm,it sharply decreased to 3300. | Our target is 400DPM. | How to reduce the soldering bridge on such "fine" pitch component? | Could you please kind enough to give me some suggestions? | Thanks, | Wister | Wister: It looks like you have yourself in a fine mess now!!! Think about this:

1. Lead length is not meaningful. But if I think about what you�re saying, your lead protrusion was about 1.6 mm and you reduced it to about 1.1 mm. Ideally, lead protrusion is 1 mm, but up to 1.3 mm is acceptable. So, the reduction was a good move. 2. Your new lead protrusion and pad size work well together to contribute the size of the solder fillet. 3. Pads should be round, may be elliptical or tear dropped, but not square or rectangular. 4. Your focus in describing the situation was on the board, the wire harness, and the flux type. Other areas deserve your attention also. For instance:

� Assuring proper machine set-up in terms of correct immersion depth, proper preheat, retention of flux, and correct wave exit angle and speed. � Checking contamination of components, solder, or boards.

5. Wave solder the row(s) of leads perpendicular to the direction of travel on the machine, add thieving pads at the end(s) of the row(s), if necessary.

Good luck

Dave F

reply »

Kevin Hussey

#11140

Re: Closer lead more soldering bridge by using spray flux | 8 June, 1999

| | Hi,my master | | How to iron out such soldering bridge with below conditions: | | 1.The component(Harness)lead pitch is 2.0mm,the lead length is 3.2mm. | | 2.PCB width is 1.6mm.Pad size is 1.65mm.Its a single copper PCB | | 3.using spraying fluxer and no-clean flux(Alcoho-base,solid content is 3.0%) | | After go though the wave solder machine,The DPM of soldering bridge on this component would be 12000, I try to cut the lead length from 3.2mm to 2.7mm,it sharply decreased to 3300. | | Our target is 400DPM. | | How to reduce the soldering bridge on such "fine" pitch component? | | Could you please kind enough to give me some suggestions? | | Thanks, | | Wister | | | Wister: It looks like you have yourself in a fine mess now!!! Think about this: | | 1. Lead length is not meaningful. But if I think about what you�re saying, your lead protrusion was about 1.6 mm and you reduced it to about 1.1 mm. Ideally, lead protrusion is 1 mm, but up to 1.3 mm is acceptable. So, the reduction was a good move. | 2. Your new lead protrusion and pad size work well together to contribute the size of the solder fillet. | 3. Pads should be round, may be elliptical or tear dropped, but not square or rectangular. | 4. Your focus in describing the situation was on the board, the wire harness, and the flux type. Other areas deserve your attention also. For instance: | | � Assuring proper machine set-up in terms of correct immersion depth, proper preheat, retention of flux, and correct wave exit angle and speed. | � Checking contamination of components, solder, or boards. | | 5. Wave solder the row(s) of leads perpendicular to the direction of travel on the machine, add thieving pads at the end(s) of the row(s), if necessary. | | Good luck | | Dave F | You might want to try a pallet that allows you to rotate the board.

reply »

#11141

Oooooh noooooo!!! | 8 June, 1999

| | Hi,my master | | How to iron out such soldering bridge with below conditions: | | 1.The component(Harness)lead pitch is 2.0mm,the lead length is 3.2mm. | | 2.PCB width is 1.6mm.Pad size is 1.65mm.Its a single copper PCB | | 3.using spraying fluxer and no-clean flux(Alcoho-base,solid content is 3.0%) | | After go though the wave solder machine,The DPM of soldering bridge on this component would be 12000, I try to cut the lead length from 3.2mm to 2.7mm,it sharply decreased to 3300. | | Our target is 400DPM. | | How to reduce the soldering bridge on such "fine" pitch component? | | Could you please kind enough to give me some suggestions? | | Thanks, | | Wister | | | Wister: It looks like you have yourself in a fine mess now!!! Think about this: | | 1. Lead length is not meaningful. But if I think about what you�re saying, your lead protrusion was about 1.6 mm and you reduced it to about 1.1 mm. Ideally, lead protrusion is 1 mm, but up to 1.3 mm is acceptable. So, the reduction was a good move. | 2. Your new lead protrusion and pad size work well together to contribute the size of the solder fillet. | 3. Pads should be round, may be elliptical or tear dropped, but not square or rectangular. | 4. Your focus in describing the situation was on the board, the wire harness, and the flux type. Other areas deserve your attention also. For instance: | | � Assuring proper machine set-up in terms of correct immersion depth, proper preheat, retention of flux, and correct wave exit angle and speed. | � Checking contamination of components, solder, or boards. | | 5. Wave solder the row(s) of leads perpendicular to the direction of travel on the machine, add thieving pads at the end(s) of the row(s), if necessary. | | Good luck | | Dave F | Wister: Ooooh nooo!!! Sorry, but I messed-up #5. The rows should move in the direction of board travel, not perpendicular, as stated. I was thinking too much. Dave F

reply »

JohnW

#11142

Re: Oooooh noooooo!!! | 8 June, 1999

| | | Hi,my master | | | How to iron out such soldering bridge with below conditions: | | | 1.The component(Harness)lead pitch is 2.0mm,the lead length is 3.2mm. | | | 2.PCB width is 1.6mm.Pad size is 1.65mm.Its a single copper PCB | | | 3.using spraying fluxer and no-clean flux(Alcoho-base,solid content is 3.0%) | | | After go though the wave solder machine,The DPM of soldering bridge on this component would be 12000, I try to cut the lead length from 3.2mm to 2.7mm,it sharply decreased to 3300. | | | Our target is 400DPM. | | | How to reduce the soldering bridge on such "fine" pitch component? | | | Could you please kind enough to give me some suggestions? | | | Thanks, | | | Wister | | | | | Wister: It looks like you have yourself in a fine mess now!!! Think about this: | | | | 1. Lead length is not meaningful. But if I think about what you�re saying, your lead protrusion was about 1.6 mm and you reduced it to about 1.1 mm. Ideally, lead protrusion is 1 mm, but up to 1.3 mm is acceptable. So, the reduction was a good move. | | 2. Your new lead protrusion and pad size work well together to contribute the size of the solder fillet. | | 3. Pads should be round, may be elliptical or tear dropped, but not square or rectangular. | | 4. Your focus in describing the situation was on the board, the wire harness, and the flux type. Other areas deserve your attention also. For instance: | | | | � Assuring proper machine set-up in terms of correct immersion depth, proper preheat, retention of flux, and correct wave exit angle and speed. | | � Checking contamination of components, solder, or boards. | | | | 5. Wave solder the row(s) of leads perpendicular to the direction of travel on the machine, add thieving pads at the end(s) of the row(s), if necessary. | | | | Good luck | | | | Dave F | | | Wister: Ooooh nooo!!! Sorry, but I messed-up #5. The rows should move in the direction of board travel, not perpendicular, as stated. I was thinking too much. Dave F | Nice recovery Dave!

Wister,

Another thing you could do would be to add thief pad's at the back of the connector pin's to dray the solder onto them. At the moment it has no where to go after the lerad's and nothing to break the equlibrium of the solder so it'll hang around unless you do something like..reduce the lead's or add flux or add abit more to the board design like the thief pad's. You could also think about angling the board to the wave. I use a carrier's with a cirular hole cut out that I can have 'plug's' made for that I can get to take any board. I can then rotate the card 5 or 10 degree's at a time till I get an optimum didtance between the pin's, which is more often than not the logest diagonal distance between the pin's..if you understand my rambling. Also depending on your machine you could set about it with an air or n2 knife..but that's cheating..

All the best

JohnW

reply »

#11143

Re: Closer lead more soldering bridge by using spray flux | 8 June, 1999

| | | Hi,my master | | | How to iron out such soldering bridge with below conditions: | | | 1.The component(Harness)lead pitch is 2.0mm,the lead length is 3.2mm. | | | 2.PCB width is 1.6mm.Pad size is 1.65mm.Its a single copper PCB | | | 3.using spraying fluxer and no-clean flux(Alcoho-base,solid content is 3.0%) | | | After go though the wave solder machine,The DPM of soldering bridge on this component would be 12000, I try to cut the lead length from 3.2mm to 2.7mm,it sharply decreased to 3300. | | | Our target is 400DPM. | | | How to reduce the soldering bridge on such "fine" pitch component? | | | Could you please kind enough to give me some suggestions? | | | Thanks, | | | Wister | | | | | Wister: It looks like you have yourself in a fine mess now!!! Think about this: | | | | 1. Lead length is not meaningful. But if I think about what you�re saying, your lead protrusion was about 1.6 mm and you reduced it to about 1.1 mm. Ideally, lead protrusion is 1 mm, but up to 1.3 mm is acceptable. So, the reduction was a good move. | | 2. Your new lead protrusion and pad size work well together to contribute the size of the solder fillet. | | 3. Pads should be round, may be elliptical or tear dropped, but not square or rectangular. | | 4. Your focus in describing the situation was on the board, the wire harness, and the flux type. Other areas deserve your attention also. For instance: | | | | � Assuring proper machine set-up in terms of correct immersion depth, proper preheat, retention of flux, and correct wave exit angle and speed. | | � Checking contamination of components, solder, or boards. | | | | 5. Wave solder the row(s) of leads perpendicular to the direction of travel on the machine, add thieving pads at the end(s) of the row(s), if necessary. | | | | Good luck | | | | Dave F | | | You might want to try a pallet that allows you to rotate the board. | | My 2 cents:

Flux. We like to think of the flux's job as preparing the surfaces for soldering. Once the board is heated, the flux is activated, and the surfaces are clean, it's done it's job. Actually, there are surfactants in the flux that help to break the surface tension and therefore, break the bridges.

I had a board with one stupid transformer oriented wrong that I swear just existed to make me miserable. 70% bridging rate. Shortened the leads, got it down to 50%. Drew pictures for the operators of the "perfect" wave height for peel off, ran different conveyor speeds, etc, got it down to 30% on a good day. Mgt wouldn't let me puchase pallets; respinning the artwork was not an option.

Then I talked to an Alpha guy who explained the whole business of surfactants to me, and how the trick to getting them to work is to get a flux stable enough to not burn off in the chip wave. So I tried this formula - and it worked! Ambient bridging levels went down to 5 - 10% of the circuit boards. And I no longer had to worry about operators setting the proper wave height or prepping the leads at the right length nearly as much anymore.

Life got good (for this board anyway). I switched over to this NR-310B stuff on all my lines, and those pesky bridges on my TO-220's went away too. So now I'm a believer.

Try it - what have you got to lose?

Chrys

reply »

Plasma Prior to Conformal Coating