In a message dated 10/31/0 4:12:07, [log in to unmask] writes:
> One partly poor wetting component  after wave soldering, through-hole
>solder joint shows good wetting near top side PCB, but show bad wetting
>on the bottom side and through-hole is about 70% filled. some suggest good
>wetting is key to evaluate a SJ reliability. IPC suggest 75% filled is
>OK, which one I choose?
>Same situation happen to  paste in hole process, Which type SJ is ok?
>the key is the fill ratio or the good wetting?
>If half of through hole SJ is good wetting, half of which is bad, Is it ok?

Hi Liu,
Good wetting is by far the more important physical aspect--however, an
incomplete fill may be a sign of wetting problems. Further, if you have
"partly poor wetting", how do you know the rest is "good wetting"?
If you have good wetting, a partial hole fill is only important in a severe
use environment, e.g. automotive, because of the stress concentration on the
PTH barrel at the solder/no-solder interface.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com

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