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January 1999

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Subject:
From:
"Stephen R. Gregory" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 22 Jan 1999 12:25:47 EST
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In a message dated 1/22/99 7:56:42 AM Pacific Standard Time,
[log in to unmask] writes:

<< Hi,

      We use the Voltronics JS100 variable capacitor on some of our
      products. Recently we have encountered failures - mode is device open.
      On inspection it was found that the ceramic substrate was cracked on
      many devices where the metal frame is crimped. Inspection of devices
      still on the reel shows the same problem. Is anyone else using this
      part and having the same problem?

      Bob Smith
      Quality Engineer >>

Hi Bob,

     I'm having problems as well with a variable capacitor, but the one I'm
using is a Sprague/Goodman cap. It's about the size of a 1206 and supposedly
it's able to be processed like any other SMT part. But the last batch of
boards we built for our customer that used that cap said that almost every one
of them failed...same mode as you. In fact, they sent me a change for us to
hand solder them with no clean as a last step, and not to run them through a
cleaner.

I noticed your post, and got some of the caps we're using from the reel I
have. Looked at about 5-10 of them under a scope, but didn't see any sort of
cracking. Our customer sent me the application notes for the cap and I didn't
exceed any of them when I last built their boards. The  processing guidelines
are:

Preheat 140° ±10° C. for 2-mins., then don't exceed 240° ±5° C for 20 secs.
maximum. Recommend water soluble fluxes, and water wash with, or without
saponifier at fairly low temperatures (their words).

I followed all the guidelines, and they still fail. I'm gonna hand solder em'
this next run of boards and we'll see what happens...

-Steve Gregory-

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