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opinion that the 5,000 ppm is obsolete.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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