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ICT, a 24-hour burn-in, and a functional test after burn-in would typically
not show you a fractured solder joint, because solder joint failures are
almost always intermittent and only show up when disturbed mechanically
(vibration) or thermally (heating or cooling). Insufficient solder is also
not your likely problem--I would guess it is inadequate wetting, for whatever
reason. Since you talk about a fine-pitch component, it is likely large;
temperature profiling of large components during reflow has shown them to lag
behind the PWB and smaller components by as much as 20C at peak reflow. Your
solder joint may never have reached temperatures high enough to assure
consistent good wetting.
Werner Engelmaier
Engelmaier Associates, Inc.
Electronic Packaging, Interconnection and Reliability Consulting
23 Gunther Street
Mendham, NJ 07945 USA
Phone & Fax: 201-543-2747
E-mail: [log in to unmask]
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