RE: [uCsimm] Soldering, was: RTL Port, actually RTAI.

From: Sergei Sharonov (
Date: Wed Jan 19 2000 - 14:31:43 EST

> I use a Metcal soldering iron for that and are very satisfied with it.
Metcal soldering iron (plus a bunch of different tips) is by far the best
tool to do any prototyping SMT work (well, except BGA). A while ago there
was a discussion on GNUSIMM mailing list and I posted a message about it but
nobody seemed interested...

> The tip is shaped as if you'd write with a pencil on sanding paper.
You probably talk about "hoof" tip. It is designed specifically to be used
with "dragging" technique.

> Then I found out that the tin on the pads is already sufficient.
Actually the rule of thumb is:
- fill 100% of the tip with solder for 100 mil pitch
- fill 50% of the tip with solder for 50 mil pitch
- fill 25% of the tip with solder for 25 mil pitch
- fill 0% of the tip with solder for <25 mil pitch. There is enough solder
on the land and the pin.

> I never had a bridge between pins this way.
I was less fortunate (or less handy) but most the time it worked fine.

> For the actual soldering, I put the soldering iron onto the
> pads, touching
> the pins from the side:
The tip angle in respect to the PCB makes a big difference.

> No matter which way you go, the pads Protel has per default are
> sub-optimal (at least for the chip I'm using). It's a lot easier
> to solder when you move the pads slightly outwards:
Well, I would be a bit cautious here. If it works fine with "dragging"
technique it does not necessarily mean that it will work fine for
production. Any experts on PCB yields here? Can anybody comment?

Sergei A. Sharonov, project manager
Daniel Measurement & Control
9753 Pine Lake Drive
Houston, TX 77055

P.S. I do not work for Metcal, etc., etc., but I did go to their seminar
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