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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