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June 2001

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Subject:
From:
David Douthit <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 13 Jun 2001 19:00:07 -0700
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Earl,

Your problem raises an interesting issue. If you are using plastic encapsulants  on a die
(PEMs) and the junction temps are over 100 degree C (at sea level) then "popcorning could
become an issue after the PEM is attached to the PCB. If the PEM is used at higher elevations
then the critical water vapor temp will lower. (The Air Force has discovered that PEMs
"popcorn" when put into orbit due to absorbed moisture)

This is something for anyone to consider when designing high power (wattage) ICs or
circuitry.

David A. Douthit
Manager
LoCan LLC

Earl Moon wrote:

> Bruce,
>
> Thanks much. I hope everyone responding (like Mike Fenner & sorry about
> your slow computer situation), whether on or off forum, knows I'm only using
> these parts in a new product and they ain't workin.' I'm not making the
> parts. Therefore, I have little idea how they come together under what
> conditions but for obvious dicing, die attach/bond, and wire bonding.
>
> I'm still leaning toward a possibility that cracking is occurring in the die
> because of the warpage and subsequent thermal stress. Thanks again for the
> die penetrant process for crack detection. Hope I don't have to go that far,
> but whatever it takes.
>
> Thank you Bill Campbell for your offerings. Ms. Koo is to be commended as
> well even though she likes money and games, or so it would seem. Whos is
> this lady? She says you all know her. I think she's hiding something. Do you
> folks think it wise to pay to find out what?
>
> Ingemar, I know you would have responded more but for lack of information.
> Don't know what else, yet, to provide pal.
>
> I have just a couple more images to post before, hopefully with all your
> help, a final conclusion's pics and analysis is provided. Feel close to
> resolution even after absorbing many hundreds of pages about GaAs FET MMIC
> high power/speed R/F amplifiers.
>
> Who is that lady?
>
> MoonMan
>
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