My question would have to be: did you damage that solder
mask the last time you worked on the MUX?
If not, it should be fine the way it is.
It is the flux that allows the solder to pull back into
a blob. Without a good flux, it forms oxide stringers
that allow bridges. Good flux, and everything works
out nicely.
I keep the board under preheat the entire time I am
working on the topside. When I am done, I just turn it
off, and let the board cool down naturally. I find that
there are fewer stress problems that way.
Let us know how you like working with the preheater. You
should see a remarkable difference.
-Chuck Harris
machineguy59 via Groups.Io wrote:
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I plan to replace the MUX (U2530) this weekend and wonder if I can put solder mask on the guard traces between signal pins? I would use Circuit Works CW2500 epoxy which is good to 350 C. I cant think of any downside and it would help avoid solder shorts. The guard traces are very close to the signal pins and shorts mean rework with solder braid. 14 pins at this pitch are sure to get one that needs touch up.
I haven't decided yet whether I will do hand soldering or hot air. I purchased a griddle at Walmart for $18.00 to act as a preheater and calibrated it with my IR temperature meter. Its easy to hold the temperature around 170 C. I will use a hand held fan to cool the board after soldering and before lifting it off the griddle so I don't temperature shock the board. But I may loose my nerve and just hand solder the new part. Either way, I think solder mask over the guard traces would help keep the solder from overflowing.
