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October 2001

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Subject:
From:
Mel Parrish <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 4 Oct 2001 16:51:43 -0700
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Will
Your suspicions are likely to be correct. There has been a great deal of
information published cautioning against point to point soldering of these
components which causes degradation or failure. Internally micro cracking
changes the component value over time if not immediately.
Typical solutions include hot air soldering techniques (skill related),
preheat of the assembly and component with reduced iron temperatures,
machine processing with preheat, etc.
Most of the data supports something around 2 degrees C per second for
temperature limitations of the components. Believe that might be a little
conservative.

Mel Parrish
Soldering Technology International
Madison, AL
256 705 5530
256 705 5538 Fax
[log in to unmask]

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Will Cabrera
Sent: Thursday, October 04, 2001 2:09 PM
To: [log in to unmask]
Subject: [TN] Leaky Capacitors


Does anyone have any experience with multilayer ceramic 1206 capacitors
turning into low value resistors? These are rework capacitors (manually
soldered) between a PTH pin and a #22 ga wire. What are the possible causes
of failure? Is flux absorption into the ceramic a possibility? My strong
suspicion is that they are being damaged by heat during the rework process.

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