[Premium-Rx] Removing SMT Components

[jan at skirrow.org]

A few weeks ago I asked for advice on depopulating SM boards. Thanks to 
those who sent advice!

The results:

I tried using a lab type heat gun. This certainly works, but is cumbersome 
and risks burning the operator! Also, the heat is uneven and I suspect it 
is very easy to have temperatures way over what is safe for the components.

I tried a conventional kitchen oven. So far this is my method of choice. I 
figured the solder would probably soften/melt around 360F. I set the over 
to 375F (but don't know how accurate this is) and left the boards to bake 
for ten minutes. A few parts did come off, but it seemed the temp was 
marginal, and there wasn't enuff time to remove the parts before the solder 
re-solidified (and I didn't fancy working inside the oven!). A longer time 
might have worked a bit better, but I went to 400F for 10 minutes, and this 
worked very well. Most of the parts came off.

BTW - it's a good idea to first remove any largish plastic parts, and 
probably make sure the XYL is away for a couple of days - baking boards 
don't smell all that good!

There was another problem, and that was that the parts tended to stick to 
each other if they'd clumped on the board or fallen together when I knocked 
the board against a surface to dislodge the bits. Probably could avoid a 
lot of this by keeping the board flat while it is hot and hitting it 
straight down on something so the parts don't run together.

Still, I think this works well. For bigger boards (these were small cel 
phone boards that I'd already carved up to remove the RF amp) I think the 
"Weber" method suggested by Kerry Banke, a list member, would be 
better.  And I even have a Weber BBQ sitting out on the deck - same 
procedure as above, but definitely mass production!

Now my problem is measuring the value of these often unmarked parts...

Jan Skirrow