Hi Doug -
This may seem to be a trivial point but the JSTD-001 committee spent
considerable time (I mean a bunch!) on the discussion of "high
reliability' versus "high performance" as a descriptor. We all want
our electronics to be very reliable whether its on a F-16, a 1997
Chevy or my boy's Teddy Ruxpin toy. There is a natural tendency to
look at a specification's classifications and pick the "high
reliability" choice because of one's impressions about that descriptor
seems to indicate rather than looking at what one's use environment
really demands. That's why in JSTD-001 there is General electronics,
Dedicated electronics, and High performance electronics with
descriptions of each. We probably should petition Dave Bergman to see
about getting this philosophy discussed as something for all the
specifications within the IPC system. Ok, now I'll go get a Coke and
get off my soapbox.
Dave Hillman
Rockwell Collins
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______________________________ Reply Separator _________________________________
Subject: Re: IPC-SM-840
Author: [log in to unmask] at ccmgw1
Date: 1/31/97 11:54 PM
LaVern,
In the C rev of SM-840, we went away from the usual class 1,2,3 of IPC
convention and went to a class H (for high reliability) and class T (for
telecommunications).
T - Telecommunications (includeds computers, telecommunication equipment,
sophisticated business machines, instruments, and certain non-critical
military applications). Solder mask on boards in this class is suitable for
high performance commercial and industrial products in which extended
performance life is required, but for which interrupted service is not life
threatening.
H - High Reliability / Military (includes that equipment where continued
performance is critical, equipment down-time cannot be tolerated and / or the
equipment is a life support item). Solder mask on boards of this class is
suitable for applications where high levels of assurance are required and
uninterrupted service is essential.
Note: Class Designations - Previous versions of this specification, and
other IPC documents, make reference to Class 1, Class 2, and Class 3. For
all practical purposes, there is no Class 1 solder mask. Class 2 is
equivalent to Class T. Class 3 is the equivalent of Class H.
If you would like more information, please contact me.
Doug Pauls
Vice-Chair
Solder Mask Task Grou
CSL
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