Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Wave Profiling a Ceramic SMT Cap

C.K.

#18536

Wave Profiling a Ceramic SMT Cap | 2 January, 2002

What is the rule-of-thumb on wave profiling Ceramics? I've used 2 methods:

1.) putting the T/C on the lead, and get a pretty good delta (within 50-80 deg. before hitting chip wave), well within manufacturer's spec.

2.) Right on the part body. Obviously the delta is alot more since the part body doesn't conduct as much heat. Hence I get a delta of 140 - 150 C (40 - 50 deg. above ideal delta), when probing the part body.

Which method is ideal?

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#18537

Wave Profiling a Ceramic SMT Cap | 2 January, 2002

The rule-of-thumb is to follow the flux mfg.'s recommended profile to achieve their specified top side PCB temperature before making contact with the wave. Typical top side PCB temps are 100-120deg.C. Your wave contact time should be around 2 seconds. You should not have a thermal shock issue or have any heat damage to the ceramic cap following this rule (w/ wave pot temp. @ 240-250C). If this is a non-standard heat sensitive cap check the cap mfg.'s specification for max. temp. and temp. rise rate.

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