In a message dated 02/06/2000 5:54:02 AM Central Standard Time,
[log in to unmask] writes:

> Could someone tell me what the standard is regarding immersion of PEM's in
> the solder wave?  Addition comments would be welcome.
>
>  Thanks
>
>  Hank

Hi Hank!

I don't think there's any standard out there, it would be dependant on the
manufactureres recommendations...I wouldn't be suprised that most won't
recommend exposure to wave soldering. A PEM by the way for those that aren't
familiar with that acronym is Plastic Encapulated Microcircuit, or IC's as
more widely known.

I think that most smaller packages are pretty tolerant to wave solder,
anything from a SO20 and below. If you start getting larger than than, then I
would start to worry.

Of course there should be a good preheat prior to the package hitting the
wave, and there are design considerations (orientation to the wave, thieving
pads etc.) that will reduce defects during the process. But my preferences
are to do a double-sided reflow on boards that have active components on both
sides, rather than expose them to wave solder. That process in my opinion is
easier than dealing with epoxy, even if you have to mask the SMT on the
bottom-side.

-Steve Gregory-

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