Hi Isaac,

        You'll probably get the answer of "It depends" more than once.  Most
assemblies consider the board to be such a small factor in the overall
reliability of the product that it's negligible (that is, unless it's leading
edge technology or very simple).  The active devices fail first.  But, maybe
this will help.

        Section 16.1 of Mil-Hdbk-217F has a section on "Interconnection
Assemblies with Plated Through Holes."  This will enable you to develop a
"Reliability Prediction" of the board based on its construction and quality.
I didn't see anything in the Bellcore (Telcordia) model, but I'm working off
of Issue 4 (can't afford the new version).
         Now, before everyone shoots me for even mentioning 217 and
predictions, let me put out the disclaimer.  Reliability predictions should be
used cautiously and 217 has been known to be overly pessimistic on it's
factors.  Especially since technology has continually improved with revisions
lagging.  Mil-Hdbk-217 is still active with Notice 2 dated 28 Feb 1995.

        You can download the document from:
http://www.dtic.mil/stinet/str/dodiss4_fields.html

Hope this helps,
Glenn

Isaac Stringer <[log in to unmask]> Wrote:
|
| Greetings!
|
| I have a customer who has asked for information regarding the MTBF (Mean
| Time Before Failure) of bare pcbs.
|
| I am wondering if there is any 'standard' information for FR4 boards.  Can
| anyone point me in the right direction??
|
| Thank you.
|
| Isaac Stringer
| VP - Vector Fabrication Inc
| Milpitas, CA
| [log in to unmask]

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