Press-fit PCB pins

[Alex Eisenhut]

Following my brain fart about a TO-3 outline switcher drop-in replacement for linear regulators, I started looking for press-fit pins.

Here's my initial guess, I need a pin that's gonna stick out 10-12mm from the PCB, and have a diameter of 1.0mm +/- 0.1mm.
I also want flush fit, so no swage, and something like tin, or light gold flash finish.
PCB will be 1.5mm (62mils) thick, and have PTH.



...but these are either non-stock or MOQ 10k I'd guess.

Closest I got so far is Harwin H2157-xx, but it's too short and too thick.

There's this dude

http://www.digikey.ca/product-search/en?x=21&y=15&lang=en&site=ca&KeyWords=8979-0-00-15-00-00-03-0

Better, but too short.

I want to avoid SMT or solder-only since the pin might fall off when soldering into the final application.

Any pointers? I've looked at Keystone, Mill-Max, TE, 3M, got close. Can you get me closer???

TIA

[SeanB]

Wire wrap pins not good enough? Any square section pin will be a press fit in an appropriate diameter round PCB hole. Even the common PCB mount plugs for IDC connectors will work, once you pull the plastic base off or use single pin versions or the snap apart ones that can be split to single pins. That way you get the bonus of a built in insulation sleeve for the hole area, and they are very close to the TO3 pin diameter as well.

[edavid]

You could use these Vector round pins and cut off the top: http://www.vectorelect.com/Catpdf/New%20Page%2074.pdf

Or these wire-wrap pins: http://www.vectorelect.com/Catpdf/New%20Page%2073.pdf

Or how about Samtec?

[Alex Eisenhut]

Might not fit into TO-3 sockets reliably.

[T3sl4co1l]

Mill-Max might have something like that??

[free_electron]

i don't know what you are trying to accomplish but : soldering press fit pins is a no-no.

even if you press fit them in your board , but solder them on the other end.

[Alex Eisenhut]

i don't know what you are trying to accomplish but : soldering press fit pins is a no-no.

even if you press fit them in your board , but solder them on the other end.

Don't see why, entire generations of boards were assembled with press-fit turrets with wires soldered to them.

[BradC]

i don't know what you are trying to accomplish but : soldering press fit pins is a no-no.

even if you press fit them in your board , but solder them on the other end.

Don't see why, entire generations of boards were assembled with press-fit turrets with wires soldered to them.

They're not pressed into plated holes.

[Alex Eisenhut]

i don't know what you are trying to accomplish but : soldering press fit pins is a no-no.

even if you press fit them in your board , but solder them on the other end.

Don't see why, entire generations of boards were assembled with press-fit turrets with wires soldered to them.

They're not pressed into plated holes.

That wasn't the claim, the claim was you can't solder them...



Here's my International Power supply press-fit, swaged, soldered on both ends.

[BradC]

That wasn't the claim, the claim was you can't solder them...



Here's my International Power supply press-fit, swaged, soldered on both ends.

Sorry, I'm confused by the specification of "non-swaged" press fit pins in your original post and how that has anything to do with swaged/soldered press fit pins you just pointed to. I'll leave you to it.

[Alex Eisenhut]

Sorry, I'm confused by the specification of "non-swaged" press fit pins in your original post and how that has anything to do with swaged/soldered press fit pins you just pointed to. I'll leave you to it.

If I use a press-fit pin, I want to solder to the other end eventually. I assume that's what the variety of finishes is for. For the Mill Max part

SPECIFY PIN FINISH:
01 200 ?” TIN/LEAD OVER NICKEL
80 200 ?” TIN OVER NICKEL (RoHS)
15 10 ?” GOLD OVER NICKEL (RoHS)
21 20 ?” GOLD OVER NICKEL (RoHS)
34 50 ?” GOLD OVER NICKEL (RoHS)

What is the purpose of a press-fit pin that is 1mm thick, 10mm long, comes in these finishes, but can't be soldered to? (The first three finishes at least.)

Swaging has that flange that gets in the way, and I don't have the tool for that anyways. So what would be the problem of using that Mill-Max part, pressing it in with a drill press, but soldering to the free end? Will that thermal cycle weaken that press-fit bond?

For example

https://www.harwin.com/products/H3150-01/

Here's a product that's a press-fit pin, specified for "Maximum Soldering Temperature:    260°C for 10 seconds"

But they also say "hey use this tool for "properly" swaging it!".

Also: "Retention Feature for mechanical board retention". Mechanical? But not electrical?

This has been quite confusing. I hate these borderline mechanical/electrical products because mechanical product companies are obtuse in their information.

And what I want to do? Thought I was pretty clear: make a PCB with a switching power supply to replace TO-3 linear regulators. I want pins that will stick out just like the ones on a TO-3 case, which implies that the pins will be soldered on the free end in the final application. That's why I wanted the press-fit option, it won't melt off as it's being soldered. I could use HMP solder for that but I have none.

Am I the first person in history to want to solder to a press-fit PCB pin? I don't know what to feel. I think it's fear.

[T3sl4co1l]

Perhaps, if you heatsink the pins with some generous copper pours on the module side, and specify a sufficiently brief soldering profile, they won't melt out.

If the board is to be flush-mountable without any stacking height, that still wouldn't help much.  Even with steel pins.

Other retention might be an option, too.  Use a board-to-board header with zero solder tail length, extra stacking height (i.e., 10mm pin length + 1.6mm board thickness), and a plastic molding that rests on the PCB top side.

I don't think I've ever heard press-fit connectors recommended where reliability is desirable.  One story I heard:
An FAE was in, bragging about their new so-and-so press-fit headers.  Typical 99.7% connectivity rate!  Engineer: "So, if I have a little backplane, with three of these 300-pin connectors on it, can you tell me where those three faulty pins are?"  The meeting got suddenly quiet...

Mechanically/metallurgically speaking, I don't see why you wouldn't be able to / want to solder such a pin.  If the press part comes loose, surely it's no less strong than a tight fitting soldered joint?  Perhaps the assumption is, the insertion process destroys the barrel of the pad, weakening the solder joint?

It's generally not recommended to solder *crimped* terminals, but I believe that's more for fatigue reasons -- the joint itself is already more reliable than solder ("gas tight" bond, without using a soft filler that can fatigue and creep), but by adding solder, you inevitably cause the wire to stiffen, increasing fatigue stress on the wire at a little distance from the connection (assuming stranded wire, that is).  In this case, I wouldn't think heat stress would be a player at all -- crimp lugs are made of the same material as the wire, so they both heat up and expand at the same rate (being conductive and all).

The same won't be true of PCB, as FR-4 has a much greater expansion rate, and the copper plating isn't there for strength (if it were, it would pull away from the board, readily!).  But, having a metal-filled barrel obviously isn't a terrible hazard (soldering in leads and all), so...

Tim

[mikeselectricstuff]

Some other pressfit pins :
http://www.interplex.com/compliant/pressfit

[mzzj]

I don't think I've ever heard press-fit connectors recommended where reliability is desirable.  One story I heard:
An FAE was in, bragging about their new so-and-so press-fit headers.  Typical 99.7% connectivity rate!  Engineer: "So, if I have a little backplane, with three of these 300-pin connectors on it, can you tell me where those three faulty pins are?"  The meeting got suddenly quiet...

Tim

I have seen plentifull of press-fit connectors on cellular base station hardware and I have to say I am impressed with the mechanical grip. Those 300-pin (or so) connectors seem impossible to remove without sledgehammer and chisel.

[max_torque]

I don't think I've ever heard press-fit connectors recommended where reliability is desirable. 

Here's a mass produced safety critical Automotive device with press fit terminals:






However, the development effort and validation processes on those terminals was probably fairly heinous!

[German_EE]

Try products from Oxley Group in the UK.