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September 1997

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Subject:
From:
"Larry J. Fisher" <[log in to unmask]>
Reply To:
TechNet Mail Forum.
Date:
Thu, 18 Sep 1997 23:08:52 -0400
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The age old question "What tests can be run in the short term under stress
conditions on materials/products that will correlate to long term under
normal conditlions?" Bell Laboratories (now Bellcore) has been wrestling with
this problem for a long time because of their need to assure the reliability
of their products in an ambient, field envoronment (i. e. the telephone
switching boxes that are located all over the countryside).

The standard "stress" conditions that have been used in the printed wiring
board and assembly industries have consisted of:

1. High temperature - 85+ deg C
2. High humidity - 85+% R. H.
3. Thermal cycling or thermal shock - -55 deg C to +125 deg C (or even
greater range).
4. High pressure - such as a pressure cooker
5. Low pressure - such as a vacuum chamber
6. Varying degrees of voltage applied to the PWB or assembly
7. Chemical corrosive environment - High acid, high alkaline, salt spray,
etc.
8. All of the above

I would say that one document that covers a wide spectrum of both PWB's and
assemblies would be the Bellcore #TSY-000078 specification. In this document
there are lots of "stress" tests for many different areas. This is a very
long document; however, I can make a copy and send it to you if you request
it off line.

Hope this helps

Larry Fisher
Dexter Electronic Materials
[log in to unmask]

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