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RE: Fillet or not?

Posted by Ron D'Eau Claire-2 on Mar 30, 2005; 8:42pm
URL: http://elecraft.85.s1.nabble.com/Fillet-or-not-tp376397p376399.html

There are those who advocate no fillet when soldering plated thru  holes.
Is
an obvious fillet in that instance a sign of too much  solder?
 
K3UJ
 
=======================================

With Elecraft's plated-through holes, it's at least a sign of "more than
enough" solder. When soldering boards without plated-through holes, it's
virtually impossible to have good solder flow without something of a fillet
because the solder only has the copper around the opening of the hole to
bond with.

On Elecraft boards, if the lead is soldered *in* the hole, there's no need
at all for any fillet to rise above the hole.

If you're having trouble making fillets when you solder, use a
smaller-diameter solder. For Elecraft boards, I never use anything bigger
than .031 and I prefer .025" diameter.

It's not a big deal on most solder pads, but there are places where it can
cause real grief. A common one in the K2 is when soldering crystals. Excess
solder will form a fillet under the crystal where you can't see it. More
than one builder has agonized over a non-functioning rig until one of those
hidden fillets was found under a crystal shorting out the signal path. It
was a tough one to troubleshoot and was found only by removing the crystal,
cleaning off the excess solder, and re-installing it.

Other kits, like the KX1 and the T1, have some very close spacing in places
that require virtually no "bump" on the soldered side of some boards for the
unit to fit together and avoid shorts.

Ron AC7AC



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