No worry Jorge,

we've been doing this for three years and had no issue. The assemblies
passed the qualifications and have a good field performance.

You don't even have to worry about special precautions. If you get poor
soldering on one of the BGAs, there must be a DFM violation, or bad
profiling. The only concern is the moisture sensitivity. Make sure you don't
expose the already soldered BGA to ambient conditions more than the time
recommended by the manufacturer, in between the reflow passes. So instead of
running during two shifts one side only, alternate the build of the sides.
Otherwise you'll have to bake the half assembled boards according to the BGA
req's, or store the PCBs at 50 Celsius.
Also, when reworking, you'll have to bake the whole assembly to preserve the
good BGA.

Hope it helps,
Ioan

> -----Original Message-----
> From: Jorge A Rodriguez [SMTP:[log in to unmask]]
> Sent: Tuesday, April 11, 2000 6:13 PM
> To:   [log in to unmask]
> Subject:      [TN] Double reflow with BGA
>
> Technetters,
>
>      We are trying to use BGA on both sides of a PWB. The BGA is a 50 mil
> pitch 27 mm x27 mm or 35 mm X 35 mm.
> We have some experience with BGA , but we have never used it with double
> reflow. Is there anyone that has this experience?. The only concern is the
> conditions of the BGA from first pass when doing the second reflow. Any
> ideas?,  has anyone deal with this issue?
>
>
>      Any comments, suggestions will be appreciated
>
>
>
> Jorge A Rodriguez
> Conexant Systems Inc
>
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