TECHNET Archives

December 2012

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
"David D. Hillman" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Fri, 14 Dec 2012 07:29:40 -0600
Content-Type:
text/plain
Parts/Attachments:
text/plain (67 lines)
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

______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________




______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________

ATOM RSS1 RSS2