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

From: Alexander Langer (eedala@eed.ericsson.se)
Date: Fri Jan 21 2000 - 07:13:30 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...

I like the Metcal also for "normal" soldering. By far the best I have
used so far.

>
> > 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.

Yes, it is. My point was mainly that you *don't* need a needle-tip-thin
soldering tip. It works better with a thicker one.

>
> > 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.

Aha! We have 25 mil pitch, so my 0% is marginally working.

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

I guess I don't have problems because I use too little tin anyway :-)
(according to your rules)

>
> > 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?

We'll soon ship the boards to be populated/soldered automatically.
Then I'll see.

Alex.

This message resent by the ucsimm@uclinux.com list server http://www.uClinux.com/



This archive was generated by hypermail 2b30 : Sun Apr 07 2002 - 00:01:34 EST