Defects Definition

Jose: Those are good guesses. Without knowing more, ask yourself:

1 There is probably adequate heat available, but that portion of the substrate that�s not soldering well is not receiving proper heating. Why is the component getting so hot, relative to the substrate, that the component is taking all available solder? What is it about the substrate that is preventing it from heating properly? Where is the heat going? Are other components, vias, or substrate design of large copper plains draining-off the heat? 2 Some surfaces must be wetting, there is solder on the lead, so there must be flux. It is not likely the flux is burning off the pad, but not the component lead. What is it about this pad that it doesn�t wet? Do other pads on this substrate have good solder flow? What�s different about this pad? Is there a solder stop on it? Are both sides of the pad wetting poorly?

Good luck

Dave F

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Jose,

I have seen this defect before. We called it re-reflow. We found the part was originally attached at SMT. Later on after seeing a heat cycle at the wave machine the leads would de-attach causing an open at In-Circuit Test.

Resolution was to monitor the component/board from SMT through to the Wave and verify the quality of the joints after each step. To check for the condition inspectors were instructed to use a 'pick' and very gently push on the suspected lead(s). Once we firmly established the wave profile as the processs breaker, we reprofiled and got the topside temps down a bit the problem went away.

Hope this helps,

Tony Di Mauro Circuit Technology Center

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Hi Jose,

J-lead are very sesitive to coplanarity, which is the major cause for the defect you described. Other posibility is that there is not enough solder paste ; J-lead need around 10% more solder past then L-lead, You have to consider the screen width (5/6/7 mil) to detrmine the past VOLUME you need !

Roni

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I have had the exact thing you describe happen to me, at least it sounds the same. On the PLCC there could be maybe 1 leg not soldered or many of them tending to be in groups but not necessarily. This happened on a established board that had always run 0 defect for the PLCC�s anyway, no parameters had been changed. It only happened on the one run and I have never seen it again. I do suspect contamination.

Travis S

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