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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.
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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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