On Wednesday, March 4, 2020 at 8:31:42 PM UTC-5, Robbie Hatley wrote:
At my workplace, I'm often faced with circuit boards which WOULD be
repairable, if not for the fact that the CPU on the board is fried.
(These CPUs are not like the CPUs in PCs; they're 15mm-square
$5 8-bit 8MHz 100-pin CPUs with 25 pins on each side, surface-mount
soldered directly to circuit boards.)

Repairing these boards is maybe impossible, but I'm investigating
options. The 2 main problems that would have to be solved a

1. Remove CPU from board. (CPU doesn't need to survive, but board does.)
Heat gun? (Might damage surrounding components.)
Solder bath? (Might unsolder surrounding components.)
Cut pins? (Might damage traces.)
OTHER???

2. Extract software from good CPU???
(The board maker won't supply the software due to copyright issues.
The boards DO have programming headers, presumably for use with an
external programming module which connects to a PC via USB; but I
don't know if such programmers can work in reverse, READING software
from a CPU instead of WRITING to it.)


Anyone here have some ideas regarding these two issues?


I used to replace Motorola MC68340 processors fairly often. I used solder wick to remove most of the solder, then an Ungar Loner soldering iron with a .015" tip, along with a tiny curved pick. I would apply a slight pressure to a pin, as I touched it with the soldering iron tip. It would op free, and the pic would remove enough heat that it stayed free from the pad. It took really good soldering skills but both the board and the IC were undamaged. These were 288 pin, 72 per edge. The programming port was JTAG, not USB.