31 Mar
2017
31 Mar
'17
9:15 p.m.
On 03/31/2017 06:15 PM, Jon Elson via cctech wrote:
I have a project I do from time to time using 128-lead
14mm TQFPs
with 0.4mm lead spacing. I use a stereo zoom microscope with a
home-made LED ring light. First, I rub the pads with a pencil eraser
to remove oxidation caused by reflow temps on the rest of the board.
I put a tiny dab of solder on two pads at opposite corners. I then
place the chip in place and reflow those pads. If the alignment is
not good enough, I can "walk" the chip a bit by reflowing one, then
the other pad. Then, I apply liquid flux to the rows of leads with
a wire dipped in the flux. And, then solder down the rows with a
fine-tip soldering iron. If a bridge develops, solder wick fixes
it.
There are plenty of good Youtube videos describing this. I use pretty
much the same method, but start off with just a binocular loupe and then
finish with a stereo microscope for final inspection.
The soldering iron tip that works best for me is a rather broad chisel
tip. I leave the fine tips for other work.
--Chuck