Inge,
That is an interesting thought!
Steve C
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord
Sent: Friday, December 14, 2012 10:04 AM
To: [log in to unmask]
Subject: Re: [TN] Component issue - epoxy die attach
The critria was THEN (about 1965) *FIVE MOLECULE LAYERS OF WATER ON A CHIP.
* Considering the extremly tough coatings the semis have today, I am of the
opinion that the 5,000 ppm is obsolete. I proposed many years ago, that we
should accept packages with He leakage 5x10exp-7 and so we did. We have made
tens of thousands hermetic packages and never had any issues connected with
humidity on inside. Medium value is of course higher, about 10exp-9.
Inge
On 14 December 2012 14:29, David D. Hillman
<[log in to unmask]>wrote:
> Hi Howard - Steve and Inge have provided you some good stuff so I can
> only offer one additional detail. The reason for the 5000 ppm limit is
> that is the' line in the sand' where you will get condensation inside
> a hermetically sealed package as you go thru temperature swings. There
> are a bunch of very fun mathematic equations which can be used to
> show that below 5000 ppm you won't get condensation as you go thru the dew
point.
> With a reading of 5600, you may want to evaluate "are you good enough"
> in terms of would water cause you issues in your product use environment.
> Good Luck.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
>
>
> From: "Watson, Howard A" <[log in to unmask]>
> To: <[log in to unmask]>
> Date: 12/13/2012 05:25 PM
> Subject: [TN] Component issue - epoxy die attach
> Sent by: TechNet <[log in to unmask]>
>
>
>
> Hello 'netters,
>
> I debated posting this, as it seems to me to be an obscure problem,
> but then, I'm always amazed at your knowledge base. I have a JFET
> 2N6550 component to be used for space application. Unfortunately, it
> is not manufactured at JANS space quality, so we buy the commercial
> grade, plus an option 2 screening, which upscreens the part to "like"
> JANTXV. I think this is called re-branding. Then, we send it to a lab
> for further upscreening to JANS. The problem is that the parts are
> failing the moisture test of the residual gas analysis (RGA). I found
> out that epoxy is used for the die attach, and likely the epoxy is
> outgasing during subsequent baking as part of the testing. My first
> question is who knows of a standard for die attach of this component
> type stating that epoxy is forbidden for military and space use? The
> epoxy used by the manufacturer is Ablestik p/n 84-1LMI; Material #
> 1119570. I just found out today that they do have the capability of
> eutectic die attach, and I'm pursing this option, expecting a huge expense
and lead time.
>
> Secondly, I had two independent labs perform the RGA. The first lab
> had results averaging ~28,000 PPM. The second lab results averaged ~5600
PPM.
> The standard is no more than 5000 PPM. They both performed the
> testing to the same MIL-STD-750. I can't understand the wide range of
> results, but my second question is who knows of any studies related to
> the negative effects of excessive (>5000 PPM) moisture inside
> hermetically sealed devices used in space? By the way, they all passed
the seal tests.
> Perhaps some of you are knowledgeable in this area. Thanks in advance
> for your help.
>
> Howard Watson
>
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