On 2/27/21 8:12 PM, Jeffrey Birt wrote:
Or you can just use the 'Arduino' headers which are 1/6 the cost, don't have
the shoulder, don't require a special PCB design, etc. etc.
Not to beat a dead horse but why try to reinvent the wheel?
I do like them the best so far, both because of no shoulder and because
of gold plating. The legs are plenty long enough to just drop down
through from the top and still leave enough length on top to make it
easy to cut with flush-cutters.
If they are thin enough. I know they are thinner than square pins but I
still haven't found a drawing to nail down what they exactly are.
But I just had a totally different idea...
For reference, let's get some actual numbers.
Here is a bog-standard DIP-28-600
http://www.microchip.com/mymicrochip/filehandler.aspx?ddocname=en589327
See the B and C dimensions.
The legs are 0.20mm to 0.38mm thin, and 0.36mm to 0.56mm wide, and since
it's rectangular the diagonal can be even a little more than 0.56mm, and
we know these fit into round machined sockets and do not damage any
sockets, leafe or round.
Common cheap machined round pins are 0.50mm wide, and fit in round
sockets, and maybe possibly theoretically too thick for leaf sockets
(they fit of course, but do they weaken the leaf? eh, probably not but
who knows)
The TE-Connectivity leadframe pins are 0.25mm x 0.50mm, and cost $0.03
per pin.
https://www.digikey.com/en/products/detail/te-connectivity-amp-connectors/1544210-2/4731536
Mill-Max and Keystone micro-pins are 0.43mm wide,
https://www.mill-max.com/products/pin/3121
https://www.keyelco.com/product.cfm/product_id/2999
And are $0.10 per pin.
https://www.digikey.com/en/products/detail/mill-max-manufacturing-corp/3121-2-00-15-00-00-08-0/436677
which is thinner than normal machined round pins yet still thicker than
pcb legs. But, I say they are thin enough that they won't hurt any
socket even theoretically. So taking that number as a reference for
"good enough"...
For the cost of the micro-pins, and since they come loose in bags where
you have to tweezer each one individually anyway, I just now thought of
an option that is no more labor than micro-pins, gold plated, but
ridiculously cheaper than even the tin TE leadframe pins:
You can get a lifetime supply of 0.40mm gold-plated brass or copper wire
on spools for a few bucks.
- Just set the pcb on top of a machined round socket, maybe clamp it
with a clothes pin or rubber band or tape etc so that it won't move
while leaving both your hands free,
- poke the wire through the pcb down into the socket until it stops,
- cut,
- poke, cut, poke, cut... you have all 28 in less than a minute.
Soldering would be a breeze from the top, no further trimming needed
when done soldering.
Plus little bonuses like, since the wire is round, it doesn't matter if
you accidentally heat the solder after the leg has been trimmed and the
leg rotates in the hole. If you break a leg it's nothing to replace it
because it's not special. And freak unexpected bonus: no waste. Every
single mm of wire is actually used.
And 0.40mm is even thinner than the micro pins. If that turns out to be
too thin (too weak and just crumples) then you can get 0.50mm which is
at least the same as common machined round pins, and still no wider than
the wide dimension of legit DIP legs, without any shoulder or insulator,
and probably actually better than machined pins because you can probably
bend the wire at least once or twice before it breaks where the machined
pins break immediately.
https://www.amazon.com/dp/B07S9JFK2V gold plated brass, 300ft, $14
or
https://www.amazon.com/dp/B07H9RBTPF gold plated copper, 60ft, $5
This is probably even less labor than the TE-Connectivity leadframes I
use now, and those are tin plated instead of gold. The "comb" lets you
work on a whole row of 14 at once, like those Arduino stackable headers,
or the "flip" pins, but the amount of fiddling you have to do almost
cancels that out where it's no quicker than individual pins.
I think the only thing to check out is if the different wire hardnesses
matter. They make this wire in different hardnesses. Is the copper wire
stiff enough? Through-hole component leads are stiff enough and they are
just copper, or is the brass wire too brittle? Probably not, since it's
meant to be wrapped into jewelry. And, is the gold plating actually gold
or some kind of colored anodization, and is it really bare with no
clearcoat? I think it's probably meant to be soldered and brazed so
probably it is nice and bare.
I think 0.4mm (26 guage) wire in brass is probably going to be perfect.
This probably works best with a pcb designed with small holes just to
fit the wire (maybe 0.55 or 6mm?), so that when you solder it, you don't
have to gob so much solder in there that it ends up running down the
leg. But should be doable even in huge holes (pre-existing boards).
Damn I can't wait to try this.
--
bkw
