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Reply-To: "fred bartoli"
From: "fred bartoli"
Subject: Re: 1206 Chip Capacitors end crack problem
Date: Tue, 29 Oct 2002 15:59:46 +0100
X-Newsreader: Microsoft Outlook Express 5.00.2314.1300
Organization: Guest of ProXad - France
NNTP-Posting-Date: 29 Oct 2002 15:58:13 MET
Bob a écrit dans le message :
> "Joseph Goldburg" wrote in message
> > HI All,
> > I have some 1206 SMD chip cap's which ocasionally
> > crack on the ends after I receive them from the SMT board
> > loader.
> > The 1206 chip caps are in the middle of the PCB 4' x 4'
> > Any pointers to common failures would be appreciated.
> > Regards
> > Joseph
> As another poster (Dave) pointed out, it's the reflow temperature profile
> that's the problem. The capacitor manufacturer specifies a max dT/dt
> in temp vs time). The difference in coefficient of expansion of the cap vs
> the pcb material is to blame.
> Make sure your assembly house is NOT soldering these caps by hand with a
> solering iron. The sudden increase in temperature that a cap sees when the
> iron tip hits it will be too much for it. A hot air tool is recommended
> hand soldering smt parts.
The fact that the cracked parts are in the middle of the board plaid for a
flexion pb somewhere in the process.
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