16 Jan
2017
16 Jan
'17
4:26 p.m.
On 01/16/2017 01:26 PM, Brian Walenz wrote:
While I wholeheartedly agree with the tool advice and the trick, I lifted a
bunch of traces on a PDP8a CPU board doing this.
Earlier machines often had
single-sided boards with no
plated through holes. These are REALLY fragile when doing
rework. It seems like the 8A should have had double-sided
boards with plated through holes, but in the early days, the
tricks we now know to make the boards durable were not
invented yet.
Today, it is common practice to use textured copper foils,
they grip the epoxy on the board substrate better. They
remove epoxy smear left by the drills with plasma etching,
exposing the glass fibers. This gives the through hole
plating better grip. The epoxies have improved to handle
heat better. And, there's more, but those are some of the
big ones.
I've also started reflowing and adding fresh
solder before attempting to
desolder. Could be better heat transfer, or just easier to suck up a
larger blob.
Especially helpful with lead-free boards, but it does help
heat transfer. You need the heat to get all the way to the
other (component) side of the board for the desoldering to work.
Jon