On 6/21/2014 6:09 AM, David wrote:
At Fri, 20 Jun 2014 07:02:44 -0400, Jerry Stuckle rearranged some
electrons to write:

On 6/20/2014 3:54 AM, Brian Reay wrote:
Michael Black wrote:


I seem to recall from early articles about surface mount the
suggestion of using a dab of flux to hold the component in place. It
was only to hold it until you actually had something soldered.

That said, I really think a good magnifiying glass or microscope makes
sense. I was trying to figure out something, and got out the
jeweller's loupe, and it's amazing how much bigger everything is.
That's not going to work for soldering, but getting good magnification
that will stand on its own is bound to help a lot. And good lighting.
Looking at that board with the loupe almost makes the idea of
soldering surface mount within my capability.

Michael,

For SMD projects, rather than repairs, you can use a domestic oven to
solder the boards. Ideally, get a small table top model (the type of
thing student or caravaners use) but I did a test run in a full sized
kitchen one. The key thing is to be able to get to 230C or so at least.

You need to plot a graph of the way the oven temp rises using a
thermocouple (I borrowed one but they are cheap enough to buy).
Basically you put the board it with all the components held in place by
solder paste.
Set the temp to about 200C and watch as it rises. When it gets to 100,
turn oven off for 3 min, this is known as drying time and is to drive
the solvent from the solder paste, them set temp to 250 or as high as
you can if lower. Now watch carefully, as soon as the solder paste
melts and flows to make the joints, turn off the oven and open the
door.

I've tried this a couple of times and the results are surprisingly
good. No dry joints, no moved components.

The graph will help you predict when things are about to 'happen' and
the thermocouple is essential if your oven temp. gauge isn't accurate.


Brian,

I hadn't heard of using a domestic oven like this. It sounds like an
interesting idea. But wouldn't it be a bit hard on the components? I
wouldn't think many would like being heated his hot.

The commercial assembly lines I've seen use robot soldering irons
instead of heating the entire board.

I guess you haven't seen many commercial assembly lines then.


You can't read, can you?

SMD assembly lines use reflow ovens. The temperature profile is designed
to preheat the boards as they move through and get the solder above the
liquidus temperature for a few seconds.

SMD components are designed to withstand a reflow cycle.


See, that's the difference between you and me. You think there's only
one way things are done. I know there are many ways, and acknowledge that.

So just stop your trolling.

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Jerry Stuckle

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