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July 2010

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Wed, 7 Jul 2010 18:33:57 +0200
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Thanks all.
I agree with the statement that silver migration is of less importance as
it's not likely to happen. BUT...if you make a simple calculation on the
electrical field strength, you come to the fact that you'll have 200 V per
millimeter. That is a lot. Much more than what the semi chip makers
recommend. I have foundry book from Triquint, and they don't ever exceed 100
V per millimeter, which is valid for dry air.  What do you think? Isn't 200
V/mm  too much?

Yes, Joyce, they should use a preform. With such a one, there will be no
epoxy creeping up the walls of the chip.  I'll check and see if preforms are
allowed for Class S.

Wetting maximum 50%,  that's what I have been recommending for two decades,
and I will insist  that  they adopt that in their process description.

Inge

--------------------------------------------------
From: "Thayer, Wayne - IIW" <[log in to unmask]>
Sent: den 7 July 2010 18:05
To: <[log in to unmask]>
Subject: Re: [TN] Hybrid precap q

> Hi Inge-
>
> Yes that's scary, but it will probably work.  I don't see how much you can
> do about it unless you can find that it actually violates a written
> specification.  The usual problem I get with too much silver epoxy is
> bleedout contamination of wirebonding pads, so maybe you will find poor
> statistics in bondpads close to this oversized deposit.
>
> Other than that, if your gut tells you 50 microns is too small, then have
> a chat with your gut about why.  You will probably come to the conclusion
> that your concern is based on potential gradient across the surface, so
> then try to estimate what it is with the present design in relation to
> your experience based on previous migration situations.  If you find this
> to be much more severe than your previous experience with known problems,
> then hopefully it fails a written spec.
>
> Wayne
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
> Sent: Wednesday, July 07, 2010 6:16 AM
> To: [log in to unmask]
> Subject: [TN] Hybrid precap q
>
> Hi  all,
> will be back with quiz 11, but before that , I have a q about silver epoxy
> mounting MMIC chips.  The amount of glue is so rich, that the silver epoxy
> wets all the way up the walls and stops just before the horizontal plane
> of
> the chip. Now, some conductors are as close to the chip edge as two times
> the diameter of a bond wire, which is about 50 um. I dislike such a small
> distance between the silver and the conductors.  I'm doing a consulting
> job
> for a company, and they mean  that this space is enough. The chips are in
> a
> laserwelded kovar package, so they are well protected, but I'm still not
> satisfied. I've seen too much of migration issues in my days.  The
> packages
> are class S. What are your opinions?
> Thanks in advance
> /Inge
>
> --------------------------------------------------
> From: "Whittaker, Dewey (EHCOE)" <[log in to unmask]>
> Sent: den 6 July 2010 17:43
> To: <[log in to unmask]>
> Subject: Re: [TN] NTC: Friday quiz 11
>
>> It's like what Doug said when he was asked if he could hear in a vacuum:
>> "is it turned on"?
>> Dewey
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Ken Bloomquist
>> Sent: Tuesday, July 06, 2010 8:18 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] NTC: Friday quiz 11
>>
>> Did we ever find out what these were?
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
>> Sent: Friday, July 02, 2010 10:40 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] NTC: Friday quiz 11
>>
>> Hi Laides and Gentlemen,
>> time again for you to sharpen yourself after a whole week of sloppiness
>> and
>> lack of challenges. The real brainy solves both mysteries.
>> Steve, are you taking the catch?  Twangggg.....
>> /Inge
>>
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