Yup. The cap is cracked. The internal plates are shifting and making your
"resistor".
You need to look as mechanical and thermal variation in your process.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Ahmet Coþan
Sent: Friday, April 21, 2006 5:40 AM
To: [log in to unmask]
Subject: [TN] Capacitor Metamorphosis


Hi everyone,

We’d a capacitor problem recently which we suppose that the soldering
proses causes it.

In our first board in which this problem occured, our 805 case 1nF Multi-
Layer-Ceramic SMD capacitor behave like resistance (33k ohm) after assembly
process. When we heat its pads up with a soldering iron, the problem
disapperad.

In our second board in which this problem occured again, we disconnect one
pin of the damaged SMD capacitor, and we still measure 23kohm resistance
value, then we disconnect both capacitor pins and measure the capacitor
alone, than we still measured 23k, however, when we apply continious heat
for 5 sec.with soldering iron again, we observed that the wrong resistance
value 23k increased till several megaohms is measured.


I wonder if anyone is faced with such a problem before with their SMD
capacitors? I really do appreciated if you can send any comments with this
problem


ps: We use SAC305 alloy in our electronic boards for wave and reflow
soldering.


Best regards,


Ahmet

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