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February 1997

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From [log in to unmask] Mon Feb 3 16:
03:50 1997
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"ddhillma" <[log in to unmask]>
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     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
     [log in to unmask]
     


______________________________ 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
[log in to unmask]
     
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