Posted by
Ron D'Eau Claire-2 on
Mar 21, 2005; 11:00pm
URL: http://elecraft.85.s1.nabble.com/RE-Double-Solder-each-one-tp376024p376026.html
Maybe double-soldering each joint works better. It's not something I've
done, but it brings up a point of trouble that I have seen often enough that
I've begun to allow for it when I write an assembly procedure.
Many builders use TOO MUCH SOLDER! Sorry for shouting, but it's astonishing
the number of solder bridges and over-sized solder fillets left on the pads
that turn up. With the plated-through pads Elecraft uses, there's absolutely
no need to have a fillet or "bump" of solder sitting on the pad.
Without being there when it was done, I can only guess at the cause. What
I'm guessing is that those builders have the same experience I do when I
pick up some over-sized solder for the job.
Too large a diameter solder makes it well nigh impossible to apply exactly
the right amount. That's why *small diameter* solder - 0.03" MAX - is
specified for Elecraft kits. Only in very rare places, like soldering the
big 'nubs' on the pc-board mounted BNC connector in the KX1, is a larger
solder useful, and even then it's not really needed. For putting components
on boards, my favorite is Kester #44 0.025" diameter.
Many of us, especially OT's like me, have plenty of larger solder in our
kits. It's the stuff we used to solder leads to huge tie points or to the
terminals of 8-pin tube sockets in our Heathkits and homebrew tube rigs in
days long past. That stuff is still fine for soldering antenna wires and
attaching connectors to feedlines, but it is way too big for building
Elecraft rigs. By the time the smallest bit at the end of the solder melts,
there's already too much on the joint. All that's wanted is enough solder to
fill the pad without leaving a bump that rises above the pad.
It's okay if there's a very small solder fillet flowing up the lead on the
component side, especially on toroid leads. Indeed, it's a good idea to be
able to see clearly that the solder is flowing from the pad up onto the
tinned lead on the toroid side. If there isn't evidence of solder flowing
onto the lead *above* the pad on the toroid side you probably have a PTTL
(poorly-tinned toroid lead) that will cause you a world of grief later on.
Pull the toroid out and tin those leads higher up. It won't hurt a thing if
the tinned lead touches the core.
On most of the kits there's plenty of room for some sloppiness in the size
of the solder bump on the bottom of the board, but that's not always true.
In any case that extra solder is just waiting to become part of a solder
bridge touching an adjacent pad, or it's already covering up a badly
soldered joint underneath.
Ron AC7AC
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