[Elecraft] Bad KPA100 PCB?

[W3FPR - Don Wilhelm]

Ron's points should be well taken by everyone.  It takes 2 things together 
to cook components and PC board traces - temperature and time, and actually 
the time factor is more critical than the temperature.  If solder does not 
flow in 2 to 3 seconds, turn up the heat or use an iron with a larger tip 
(more heat mass).  Modern components usually are speced to withstand 
soldering temperatures for 5 to10 seconds, so you are more likely to cause 
damage from the time element than with a high temperature.  Keep those 
soldering irons between 700F (375C) and 800F (426C).

PS - when the surface to be soldered is large (as on the KPA100 output 
transistors and transformers), use a large iron tip, a small tip will have 
the heat 'sucked out of it' by the large metal area on the PC board, and you 
will have to dwell on the joint a long time waiting for the iron (and PC 
board copper) to come up to temperature.

73,
Don W3FPR

----- Original Message ----- 

You do not want to hold an iron on the joint too long, even at 300C. It
should be hot enough for the solder to flow within 2 or 3 seconds at the
most. So cranking up the temperature close to 400C and getting the solder to
flow quickly is easier on most parts - especially the I.C.s, transistors and
diodes.

I normally work at 375C (700F).

That brings up another point for anyone using de-soldering braid. In that
case 375C (700F) is not hot enough. The braid will pull too much heat away
from the joint, meaning the joint has to "cook" for a long time to melt the
solder. Like most of us, I prefer a solder sucker type of tool,  but when I
choose braid, I find no problem getting it to work with the iron at 425C
(800F). "Cooking" a joint with a cooler iron will more likely debond the
trace from the board!