Stuffing boards with pulled QFP chips
cclist at sydex.com
Fri Mar 31 23:15:22 CDT 2017
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
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.
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