[time-nuts] Vaperware Parts and pulse stretching circuits

[Bill Notfaded]

I totally agree with the Metcal soldering station!!!  I'll never go back to
anything else.  I don't even use a scope.  I bought some magnifying glasses
with 5 sets of different power lenses you wear like glasses.  It has built
in led light and adjustable strap that hold it on your head off Amazon.
Works great.  I can do all small surface mount stuff with them.  Plus I
have my normal vision and hand eye coordination going that way.  Soldering
under a scope or on a video monitor is a lesson all in itself!

Bill

On Sat, Apr 25, 2020, 6:15 AM Gerhard Hoffmann <ghf at hoffmann-hochfrequenz.de>
wrote:

>
> Am 25.04.20 um 13:41 schrieb John Ackermann:
> > I do have a microscope (cheap Chinese unit, maybe $400 with articulated
> arm and the works) and it does make things much easier.  But as long as you
> can see the work, you can do the job.
> >
> > It's not that hard to do small pitch parts.  I usually do the best I can
> soldering individual pins, knowing their will be bridges, then clean up
> with solder wick and *lots* of no-clean flux.  You can never have too much
> flux.  I've found a 1.6 mm chisel tip is a good all around size for SMD
> work, though I have a 0.8 mm chisel available for when things get tight.
> >
> > The hardest part is getting the first couple of pins tacked down so the
> part is square on the pads.  After that it's fast.
> >
> > John
>
> I have about the same here, plus a cheap Chinese Ayoue852 hot air
> station. Exchanging the Weller for a Metcal was the biggest improvement
> after the LED ringlight for the microscope.
>
> In my quest to scrutinize the 1/f region, I have built some chopper
> amplifiers and the newest one will have GaN transistors that are nekkid
> chips with jut 4 tin bumps below. No case, just the passivated chip, 1 *
> 1 mm, EPC2038. Low channel resistance, even lower capacitance -> low
> charge injection. Resistors are 0603.
>
> Fearing I could not handle them, I made a minimum version of the switch
> itself as a test structure in an unoccupied corner of a different
> project. But soldering did take just 3 minutes, it was surprisingly
> easy. Just keep the air flow low enough, or you will have trouble to
> find the chips again. The thick-liquid flux helps to fix the chips in
> place.
>
> Legible part numbers on the board are hopeless at this scale. The board
> was made by PCBway, there were some discussions about having solder mask
> ON part of the pads, and some discussions with our German customs that
> you cannot buy 10 boards for $10 or so.
>
> The chips are the gray squares between the 2 vias on the left and the 4
> huge coupling capacitors.
>
> Cheers, Gerhard
>
>
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