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Radial capacitors have water gain

Boca

#11524

Radial capacitors have water gain | 10 May, 1999

We have been having an ongoing problems with radial electrolytic capacitors (thru hole)for some time. 1. When we wash them in our inline cleaners the sleeving shrinks up from the PCB leaving the 'can' exposed. Some designs have traces on the surface of the PCB and the 'can' can short to the trace. Also customers just don't like seeing the exposed 'can'. 2. Again, during wash, the caps entrap water inside the sleeving and under the plastic disk (if present) located on the top of the caps. If the cap is squeezed the water literally squirts out. ICT and functional test types really hate this, especially the high voltage testers. Sometimes we prick the side of the cap and drain the water, but frequently we have to replace the cap.

We have checked vendor specifications, allowable processing temperatures range from 40C to 110C. All vendors ecourage lower wash temperatures and presures. Hey, SM technology is producing smaller clearances to clean and greater density, the preasure (pun intended) is toward higher preasures. The water temperature is already at the minimum specified by the flux manufactures. Most vendors claim only a few shops have these problems.

I've profiled the washers, max temp is 150F. Not using IR heaters in drying. Checked presures, 25 to 30 PSI.

A. Do any of you have similar problems or are the vendors right, we are alone on this one?

B. Any solutions to offer from those of you who have fought this one?

I apologize for being lenghty, this one is buggin us.

Thanks

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#11525

Re: Radial capacitors have water gain | 10 May, 1999

| We have been having an ongoing problems with radial electrolytic capacitors (thru hole)for some time. | 1. When we wash them in our inline cleaners the sleeving shrinks up from the PCB leaving the 'can' exposed. Some designs have traces on the surface of the PCB and the 'can' can short to the trace. Also customers just don't like seeing the exposed 'can'. | 2. Again, during wash, the caps entrap water inside the sleeving and under the plastic disk (if present) located on the top of the caps. If the cap is squeezed the water literally squirts out. ICT and functional test types really hate this, especially the high voltage testers. Sometimes we prick the side of the cap and drain the water, but frequently we have to replace the cap. | | We have checked vendor specifications, allowable processing temperatures range from 40C to 110C. All vendors ecourage lower wash temperatures and presures. Hey, SM technology is producing smaller clearances to clean and greater density, the preasure (pun intended) is toward higher preasures. The water temperature is already at the minimum specified by the flux manufactures. Most vendors claim only a few shops have these problems. | | I've profiled the washers, max temp is 150F. Not using IR heaters in drying. Checked presures, 25 to 30 PSI. | | A. Do any of you have similar problems or are the vendors right, we are alone on this one? | | B. Any solutions to offer from those of you who have fought this one? | | I apologize for being lenghty, this one is buggin us. | | Thanks | | Must be your wash process, because companies all around the world use these parts, and nobody else has this problem...

Yeah, right! I heard that one, too. Same problem. We called them "pregnant capacitors" because they were retaining water, and they actually looked a little pregnant by their profile. And our vendors told us that it must be something with our process, because nobody else had ever had this problem. And we went through that dang water washing process with a fine tooth comb. Lowered temperatures, checked pressures, changed out filters, changed out nozzles, even had the mfr come in to verify it. Everything checked out. Still got pregnant caps. And you're right about those "testy" test types. They sure do get their knickers in a twitch when you send wet parts to their fixtures.

Then the problem subsided for a while. Just when we sat back and and said "phew" and asured our customers that everything was under control, it came back. DOOP!

I left the company before this thing ever got resolved, so I don't know the answer, but here's what we did to get boards out the door. Baked them in a desicating oven. You know, the kind that pulls vacuum? It was a regular overnight process. We'd put all the boards with pregnant caps in one area, and at a particular time every night, a designated person would put the totes on carts and wheel them down to another part of our facility and put them in the chamber overnight. The bake was something like 100C for 8 hours with low vacuum pressure. It managed to pull the water out.

Nice band-aid, huh? Made a regular (almost ISO-documented) process out of it. Well, that's contract mfg fer ya. Gotta do whatcha gotta do to get them boards out the door.

This was about 4 years ago, but I seem to recall that we were narrowing the problem down to the shrink tubing that makes the sleeve. Our supplier QE's found that there was no tracability on this when they went digging into vendor records. That was around the time that the problem went away for a few months. When it was considered resolved and the inquiry was closed is when it came back.

So one must consider the source of the caps and the fact that the problem is intermittent. My thoughts were that they were getting this shrink wrap from an alternate (aka cheaper) source, and ended up going back to the original.

That's a start anyway. Hope it helps.

Chrys

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C.K.

#11526

Re: Radial capacitors have water gain | 10 May, 1999

| | We have been having an ongoing problems with radial electrolytic capacitors (thru hole)for some time. | | 1. When we wash them in our inline cleaners the sleeving shrinks up from the PCB leaving the 'can' exposed. Some designs have traces on the surface of the PCB and the 'can' can short to the trace. Also customers just don't like seeing the exposed 'can'. | | 2. Again, during wash, the caps entrap water inside the sleeving and under the plastic disk (if present) located on the top of the caps. If the cap is squeezed the water literally squirts out. ICT and functional test types really hate this, especially the high voltage testers. Sometimes we prick the side of the cap and drain the water, but frequently we have to replace the cap. | | | | We have checked vendor specifications, allowable processing temperatures range from 40C to 110C. All vendors ecourage lower wash temperatures and presures. Hey, SM technology is producing smaller clearances to clean and greater density, the preasure (pun intended) is toward higher preasures. The water temperature is already at the minimum specified by the flux manufactures. Most vendors claim only a few shops have these problems. | | | | I've profiled the washers, max temp is 150F. Not using IR heaters in drying. Checked presures, 25 to 30 PSI. | | | | A. Do any of you have similar problems or are the vendors right, we are alone on this one? | | | | B. Any solutions to offer from those of you who have fought this one? | | | | I apologize for being lenghty, this one is buggin us. | | | | Thanks | | | | | Must be your wash process, because companies all around the world use these parts, and nobody else has this problem... | | Yeah, right! I heard that one, too. Same problem. We called them "pregnant capacitors" because they were retaining water, and they actually looked a little pregnant by their profile. And our vendors told us that it must be something with our process, because nobody else had ever had this problem. And we went through that dang water washing process with a fine tooth comb. Lowered temperatures, checked pressures, changed out filters, changed out nozzles, even had the mfr come in to verify it. Everything checked out. Still got pregnant caps. And you're right about those "testy" test types. They sure do get their knickers in a twitch when you send wet parts to their fixtures. | | Then the problem subsided for a while. Just when we sat back and and said "phew" and asured our customers that everything was under control, it came back. DOOP! | | I left the company before this thing ever got resolved, so I don't know the answer, but here's what we did to get boards out the door. Baked them in a desicating oven. You know, the kind that pulls vacuum? It was a regular overnight process. We'd put all the boards with pregnant caps in one area, and at a particular time every night, a designated person would put the totes on carts and wheel them down to another part of our facility and put them in the chamber overnight. The bake was something like 100C for 8 hours with low vacuum pressure. It managed to pull the water out. | | Nice band-aid, huh? Made a regular (almost ISO-documented) process out of it. Well, that's contract mfg fer ya. Gotta do whatcha gotta do to get them boards out the door. | | This was about 4 years ago, but I seem to recall that we were narrowing the problem down to the shrink tubing that makes the sleeve. Our supplier QE's found that there was no tracability on this when they went digging into vendor records. That was around the time that the problem went away for a few months. When it was considered resolved and the inquiry was closed is when it came back. | | So one must consider the source of the caps and the fact that the problem is intermittent. My thoughts were that they were getting this shrink wrap from an alternate (aka cheaper) source, and ended up going back to the original. | | That's a start anyway. Hope it helps. | | Chrys |

reply »

C.K.

#11527

Re: Radial capacitors have water gain | 10 May, 1999

| | | I left the company before this thing ever got resolved, so I don't know the answer, but here's what we did to get boards out the door. Baked them in a desicating oven. You know, the kind that pulls vacuum? It was a regular overnight process. We'd put all the boards with pregnant caps in one area, and at a particular time every night, a designated person would put the totes on carts and wheel them down to another part of our facility and put them in the chamber overnight. The bake was something like 100C for 8 hours with low vacuum pressure. It managed to pull the water out. |

In my previous life, we also had a problem with PREGNANT Electrolytic capacitors in our board washer!!! What happened to ours were 2 things - they would blow up with water, and also, the bottom part of the sleeving (just above the base) would go up and expose the can. ...but in our case, it was only one of those "here-and-there" type problems and not recurring. It was one of those problems that would "go away" and then come back for a couple of weeks, and then go away again. We did the same thing...we changed washer paramters, profiled the washer, called the manufacturer, etc...and got the same response from them, as well. We would rack up the boards with the pregnant caps, and just have repair people swap 'em out.

Like you, Chrys, i left the company without ever fully resolving this problem!! ...so much nicer now to be in a "no-clean" environment.

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P.L. Sorenson - Technical Consultant

#11528

Re: Radial capacitors have water gain | 11 May, 1999

| | | | | | | I left the company before this thing ever got resolved, so I don't know the answer, but here's what we did to get boards out the door. Baked them in a desicating oven. You know, the kind that pulls vacuum? It was a regular overnight process. We'd put all the boards with pregnant caps in one area, and at a particular time every night, a designated person would put the totes on carts and wheel them down to another part of our facility and put them in the chamber overnight. The bake was something like 100C for 8 hours with low vacuum pressure. It managed to pull the water out. | | | | | In my previous life, we also had a problem with PREGNANT Electrolytic capacitors in our board washer!!! What happened to ours were 2 things - they would blow up with water, and also, the bottom part of the sleeving (just above the base) would go up and expose the can. ...but in our case, it was only one of those "here-and-there" type problems and not recurring. It was one of those problems that would "go away" and then come back for a couple of weeks, and then go away again. We did the same thing...we changed washer paramters, profiled the washer, called the manufacturer, etc...and got the same response from them, as well. We would rack up the boards with the pregnant caps, and just have repair people swap 'em out. | | Like you, Chrys, i left the company without ever fully resolving this problem!! ...so much nicer now to be in a "no-clean" environment. | You might consider the following: 1. Obtain and test samples of capacitors from various manufacturers. Those that pass get on your approved supplier list. 2. Perform receiving inspection of each lot by running a sample quantity of parts through your process. Reject lots that don't meet your requirements.

reply »

Joe Byrde

#11529

Re: Radial capacitors have water gain | 11 May, 1999

| | | | | | | | | | | I left the company before this thing ever got resolved, so I don't know the answer, but here's what we did to get boards out the door. Baked them in a desicating oven. You know, the kind that pulls vacuum? It was a regular overnight process. We'd put all the boards with pregnant caps in one area, and at a particular time every night, a designated person would put the totes on carts and wheel them down to another part of our facility and put them in the chamber overnight. The bake was something like 100C for 8 hours with low vacuum pressure. It managed to pull the water out. | | | | | | | | | In my previous life, we also had a problem with PREGNANT Electrolytic capacitors in our board washer!!! What happened to ours were 2 things - they would blow up with water, and also, the bottom part of the sleeving (just above the base) would go up and expose the can. ...but in our case, it was only one of those "here-and-there" type problems and not recurring. It was one of those problems that would "go away" and then come back for a couple of weeks, and then go away again. We did the same thing...we changed washer paramters, profiled the washer, called the manufacturer, etc...and got the same response from them, as well. We would rack up the boards with the pregnant caps, and just have repair people swap 'em out. | | | | Like you, Chrys, i left the company without ever fully resolving this problem!! ...so much nicer now to be in a "no-clean" environment. | | | You might consider the following: | 1. Obtain and test samples of capacitors from various manufacturers. Those that pass get on your approved supplier list. | 2. Perform receiving inspection of each lot by running a sample quantity of parts through your process. Reject lots that don't meet your requirements. | | Have you ever tried putting tape on the top of the caps before washing them? This works for me. No baking, no rework, no testing batches.

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Dave McDermid

#11530

Re: Radial capacitors have water gain | 16 May, 1999

| | | | | | | I left the company before this thing ever got resolved, so I don't know the answer, but here's what we did to get boards out the door. Baked them in a desicating oven. You know, the kind that pulls vacuum? It was a regular overnight process. We'd put all the boards with pregnant caps in one area, and at a particular time every night, a designated person would put the totes on carts and wheel them down to another part of our facility and put them in the chamber overnight. The bake was something like 100C for 8 hours with low vacuum pressure. It managed to pull the water out. | | | | | In my previous life, we also had a problem with PREGNANT Electrolytic capacitors in our board washer!!! What happened to ours were 2 things - they would blow up with water, and also, the bottom part of the sleeving (just above the base) would go up and expose the can. ...but in our case, it was only one of those "here-and-there" type problems and not recurring. It was one of those problems that would "go away" and then come back for a couple of weeks, and then go away again. We did the same thing...we changed washer paramters, profiled the washer, called the manufacturer, etc...and got the same response from them, as well. We would rack up the boards with the pregnant caps, and just have repair people swap 'em out. | | Like you, Chrys, i left the company without ever fully resolving this problem!! ...so much nicer now to be in a "no-clean" environment. | We too had this problem a few years back. Our resolve was, as you mentioned, moving the product to a no-clean process. Though this transition was not painless (flux residue loves to hide under these guys and when you get them warm enough to volitalize the flux you usually have dramatic changes too the insulating tubing and plastic tops),we did so sucsessfully just before the customer pulled the product back in-house. UGH!

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