From: Andrew Kohlsmith
Subject: Re: Total lack of response re SMT query - What gives ?
Date: Tue, 31 Dec 2002 12:23:17 -0500
NNTP-Posting-Date: Tue, 31 Dec 2002 12:23:25 EST
Organization: WorldCom Canada Ltd. News Reader Service
> I do not like to work with chip so small unless the design requirements
> dictate this route! SMT is super hard to work with in the prototype or
> bread board stage. Damned solder drpis all over the leads and all at
Slow down, cowboy. I solder TSSOP and PQFP parts by hand without (too much)
trouble. Solder wick is amazing (get good quality stuff, and a hot iron)
at correcting fine-pitch mistakes, and low-solids flux is essential at
preventing soldering errors.
I used to prototype PCMCIA cards when I was 19 -- a 204 pin PQFP took 10
minutes: flux pen all the pads for the chip (just like a highlighter -- 4
wipes, once for each row), then place the part. Get a bit of solder on the
iron and touch down a corner. Do the opposite corner. Now blob up solder
to cover 3-4 pins on one row. Flux pen again. Nice and wet. Now drag the
iron across the entire row -- the solder will follow, leaving the exact
right amount at each pin. You may have a bit of cleanup to do at the last
pins, but that's it. Use a dentist's pick and rake it across to make sure
you got a good solid connection.
The trick was the angle to drag the iron. I destroyed 2 parts before I got
Nowadays (I'm 26) I can't do it in 10 minutes, but I can get it done in
under half an hour. I don't rake the iron across because I usually don't
have spare parts, but I use my iron with a tiny bit of solder and touch
down a pin, then then the next and so on... Always putting solder on the
iron and never trying to solder down a pin in the traditional manner.
I use a standard Weller iron (the magnetic tip temp control, 700oF tips (I
think) -- I believe my tip of choice is the conical fine-pitch (1 or 1.5mm)
1206 and 0805 parts aren't a problem at all, nor are most ICs and SOT/SOD