On Tue, 13 Dec 2011 08:34:06 -0000, "N_Cook"
wrote:


PCB holes somewhat larger than the component pins always, given time, would
cause ring cracks in solder but with PbF occurs in just a year or two.

PbF is Lead Fluoride in chemical terms. Please find a better abrev.

For
things like pcb mounted multi-terminal transformers they could have an extra
machining stage. A conical grinding or milling stage, per hole, on the side
that accepts the component so that larger holes could be avoided and still
not mess-up the hand alignment/placement due to microscopic , but in spec,
misalignment of the pins

It's been a while since I've ordered production PCB's, but as I
recall, the number of drill changes has a huge impact on the cost.
Auto manufacturers are VERY sensitive to costs. As a result, it's
more common to use cylindrical holes and wedge shapped component pins
on things like xformers and relays. These have the added bonus of
being self supporting during wave soldering.

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