To the ITM Team,

Gee you sure are critical and quick to jump to conclusions. I wonder where
our industry would be if people choose NOT to try new things because of
criticism like yours. Perhaps you should stick to comments where you have
first hand experience.

I have to ask, do you have any first hand experience with "differential
heating" or an ETS CUREFLOW System? I bet the real story is that you sell a
competing reflow oven that is not as flexible as the CUREFLOW (aka Whoopee
Flow).

Now, why don't you tell us how to solder the BGA to the bottom side if the
surface tension will not hold during second reflow?

BS

PS- I never said that the ETS system is the only oven that could solder
bottom side BGA's.




>Regarding populating both sides of the board with BGAs, I think Bev Christian
>summed it up pretty well.  If you meet the parameters she mentioned, you
>should be fine with most PBGAs. The formula I use for calculating what will
>stay in place when re-reflowed is the sum of the lead (or collapsed sphere)
>surface area (all interconnects on the device) divided by the weight of the
>component in grams.  If it comes out to less than 30 grams/ sq in, the
>component will stay on as there is ample surface tension.  (Note, most ceramic
>BGAs or CGAs exceed this ratio).
>
>You sure don't need "differential heating" and you can do it on ANY reflow
>oven (not just an ETS whoopee-flow or whatever) that, as Bev mentioned, has a
>smooth running, edge conveyor
>HOWEVER........
>As Jerry Cupples wisely insinuates - beware when you do populate both sides
>with these.  Remember to allow room for removal and replacement (Design for
>Repairability 101) !  We don't live in a perfect world, you know.
>
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