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Dealing with TH Barrels on Bds w/Heavy Ground Planes

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#56945

Dealing with TH Barrels on Bds w/Heavy Ground Planes | 15 October, 2008

Dear SMTNetters:

What are some favorite techniques for getting all of the solder from a plated throughhole on a heavy ground plane area? We are using a SAC 405 alloy.

Regards

BWET

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#56962

Dealing with TH Barrels on Bds w/Heavy Ground Planes | 16 October, 2008

A good solder connection with heavy ground plane requires: * Plenty of heat [Is the preheater located too far from the wave? Whenever you look at board temperature, there is a sharp decrease in temperature between the preheater and the wave.] * Contact time [This is the standard solution. With lead-free, copper dissolves into the solder pot. Copper dissolution from the corner between the barrel and the pad is concerning. For a reliable product, it makes you wonder if copper shouldn't plated be thicker during fabriction.] * Adequate flux [Ugh, longer contact time just exhausts the flux.] * Solderable surfaces * Proper exit/peel away from the wave

We believe the chip wave is useless in helping to increase barrel fill, because the added benefit of additional heat input seems to be counter-balanced by the chip wave contribution to exhausting the flux.

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