I just took a certification class at work for IPC-610(D) whihc is for
solder inspection. So, I'm now authorized to answer your question! The
method of bending the leads over is called "cinching" the leads and is
acceptable as long as the component lead does not get close to other
circuit components, traces, leads, etc. that would violate any designed
minimum electrical spacing requirements. It doesn't take very much of a
bend to allow the parts to be held into place. You might not want to
bend them at 90 degree angles to make the leads flat with the board,
though because it would likely be more difficult if you need to perform
rework later.
Are there other methods? Well, IPC-610(D) did specify other methods as
well, actually. One was an example of a resistor that had a wire that
went over the top of it and was soldered through holes alongside the
resistor, but boards would have to be built specifically to do that and
I'm sure yours isn't. That example really only applied to axial lead
parts. The hold-down wire is really not used very often, although I did
see it used on some larger axial lead parts in old aerospace qualified
parts, and probably other applications where there may be a high
vibration environment. The other method that was mentioned was use of
some sort of adhesive or staking material. There were specifications on
how much you would apply, and then it gets messy as well to have to deal
with that stuff (what is the right stuff to use was not specified, the
class didn't address process issues, just inspection criteria of solder
joints). Although it wasn't addressed, I think that if you wanted you
could probably also just hold the component until at least one lead is
soldered (or for ICs and other long SIP or DIP packages leads on both
ends of the part).
Don't use too much solder, minimize the amount of time that you have the
soldering iron on the circuit pad & component lead, and inspect your
solder joints after soldering to make sure you don't have an accidental
short circuit to adjacent pads or other problems. The training we got
was pretty much common sense, but since common sense is lacking and
industry needs standards which they can use to specify acceptability,
IPC-610(D) seemed pretty good. I wish I had the course before
assembling my K2, but I think that in general my common sense was okay
anyway.
Have fun!
Mark, NK8Q
Clint Sprague wrote:
I'm attempting my 1st contruction project in many
years...
CMOS4 keyer, and I have what is probably a pretty
stupid question that maybe others can answer for me
here. When you install a component on the printed
side of the circuit board, and then you tip the board
over to solder, what are accepted methods to keep the
compenent from falling off? I've read
that you should bend the leads to hold the component
onto the board
but I was wondering if this is the only acceptable
way?
Thanks for you info,
73 - Clint - WS1V
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