Steve,
 
A difficult question. My gut tells me that if the parts wetted fine, then the solder joint is fine.
 
Just wondering if this is a "bad" gut feeling since the part does eventually take solder. I know that the 2331ZX flux widens the process window so that even some stubborn oxides and contamination can be overcome and soldered. I would not suspect that the flux would help form a good wetted solder joint while at the same time masking a component problem.
 
Keep us posted. Thanks.
 

Bill Kasprzak
Moog Inc, Electronics Process Engineering

-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]]
Sent: Tuesday, July 29, 2003 12:04 PM
To: [log in to unmask]
Subject: [TN] Capacitor Dewetting...

Hi All!

I hope your day is going better than mine...

Starting from the beginning. We have a board here that has SMT capacitors on the bottom of the board that we wave solder, I also use Kester 2331ZX flux which is pretty aggressive.

We've been building them a while without problems. Then I get flagged down one day last week by one of our touch-up operators who tells me that shes seeing a lot of dewetting on certain capacitors, and sometimes she can't get the solder to wet at all to the terminations, so she has to change the cap with another one from the reel.

Go to:  http://www.stevezeva.homestead.com   and look at capacitor dewetting.

We're seeing this problem in varying degrees on close to half of this particular capacitor. I sent the picture that's on my page with another one to the manufacturer.
They asked me to give them the lot code that was on the reel that the capacitors came from, and could I send at least 200 pieces for analysis.

The response came back via email that this definitely was a lot related issue, and in short, the parts did not receive proper nickel coverage during the plating process. I was told that they were working to figure out the best way to issue us a RMA so we could return the parts we have in house, and also have the inventory from that lot returned by the distributor we bought them from.

I replied to their email asking if there were any reliabilty issues with the caps on boards we've already built, even if they show good wetting, but I haven't received a reply yet. I've also called only to get voicemail.

Should I suspect the caps that are already installed on assemblies, even if they look fine? My gut feeling tells me that I shouldn't trust these caps...am I paranoid?

Thanks everyone...

-Steve Gregory- ---------------------------------------------------
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