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Subject:	RE: DES/FAB: PEMNUT FASTENERS IN FR4 FIBERGLASS -Reply
From:	JIM ENNIS <[log in to unmask]>
Date:	Thu, 11 Jul 96 16:17:00 PDT
Content-Type:	text/plain
Parts/Attachments:	text/plain (44 lines)

Another point in using press-in standoffs:  Be sure to use these in laminate 
over .045 inch thick.  Any less will bow the board during assembly and could 
fracture nearby joints or stress traces.  Also, your assemblers should have 
the proper tooling.  Without the proper support of the card during assembly, 
the standoffs can go in at odd angles; repair / realignment of these is next 
to impossible without messing up the hole.
 ----------
From: TechNet-request
To: DesignerCouncil; TechNet; willli
Subject: DES/FAB: PEMNUT FASTENERS IN FR4 FIBERGLASS -Reply
Date: Thursday, July 11, 1996 8:25AM

One word of caution when choosing your pad sizes and inner layer
clearances, base them on the component diameter and not the specified
hole size. The diameter of the part is normally some .015 larger than the
finished hole size specified and should be taken into account in your
design.

Another problem that comes up is that many of these fasteners require
a +.003, -.000 tolerance on the finished holes. When placing in
nonplated holes this is not much of a problem. If using plated holes this
tolerance is too tight for a large plated thru hole. We have been very
successful using a +.004,-.001 finished hole size tolerance.

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