[hpsdr] SMT Soldering and Circuit Board Heat Question

[Steve Nance]

Bruce,

I went the hot plate route and gave up the idea. To get enough heat to melt
the paste on top of the board the bottom side gets so hot the white
silkscreen turns brown/yellow. The major problem is the airspace between the
hot plate and the board. The actual hot plate surface gets so hot my digital
thermometer pegs out. To me this is just asking for trouble. I even have a
temperature controller with a thermocouple on it and it is useless as it
can't control the hot plate since it's temp is completely out of range.

I actually bought a high end cast iron hot plate ($100) thinking that it
would have better heat distribution across it's surface, which it does, but
it takes forever to cool off, also bad.

I've scrapped the hot plate idea and gave it to my wife who told me nobody
uses the things anymore, I'll make somebody a really good deal on it
though...

Other people use them as warmers in conjunction with hot air on the top side
which works ok if you keep the hot plate temp down. I have a hot air rework
station that works well for me. The only problem is it is slow as you can
only do one part at a time. 

I think a good quality convection Toaster Oven with a reflow controller is
the way to go. Everything gets heated up at the right time based on the oven
air temperature which is much easier to control. Somebody mentioned here a
while back having bought a nice convection oven with quartz elements from JC
Penny I think for around $100, but I can't find that post.

Just my 2 cents worth.

73
Steve

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

 I have been trying to learn how to solder these smt parts.

What I have is some solder paste with a melting temp of
361 degrees F, and a cheap six inch hot plate. The hot plate is made out of
cast iron and I an able to measure the temp with fair accuracy.

 Now my concern is this; how much heat can the circuit board stand before it
turns to junk? My plan is to heat the circuit board with the smt parts and
solder paste and finish this off with the embossing tool that Cash Olsen
uses. But, I am worried about the heat on the board being too much, prehaps
some of you have gone throuh this and know if the boards can stand the heat.

 Bruce K3CMZ

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