Soldapullt original vs III

[Jon Elson]

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