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1996

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Subject:
From:
"Edwards, Ted A (AZ75)" <[log in to unmask]>
Date:
10 Jun 1996 15:48:23 -0500
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One approach is to fill the hole with a temporary solder mask  forced into 
the holes from the back side.  This works on thinner boards by completely 
filling the hole but as the boards get thicker it does not go all the way 
through.  Even so the volume remaining unfilled is predictable.
 ----------
From: [log in to unmask]
To: [log in to unmask]
Subject: ASM: SMT pads with vias.
Date: Friday, June 07, 1996 6:25PM

        We are manufacturing military multilayer circuit cards with via 
holes      in the smt pads, unless they are filled prior to mounting 
components,      they affect the reflow process in an uncontrolled manner, 
producing      random solder joints with insufficient solder volume.
        Is there a know process for either plating shut (not my choice)or 
     filling the vias during the pwb fab process, of is there a known 
     process for controlling the travel of solder down unfilled vias that 
     remain in the compontent pads such that there is less variability in 
     the finished solder joint volume?
        Thanks, [log in to unmask]
     Neal Preimesberger at Hughes Missile System Co. Tucson AZ.



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