I have pressed many, many, many connectors into .031 PWBs, nearly all were HASL finish which seems to work best as the lead in the HASL acted as a sort of lubricant.
I have not done it on any other finish, however.
One thing you need to check is the split pin dimension on the connector; it has to fit inside the hole, ie, cannot go past the hole.
As far as the 031" thickness, that did not seem to matter as long as the tooling nest was properly designed. The holes in the nest have to support the PWB right up to within a few thousandths of an inch from the plated through holes, else you will get the delamination (actually, measling) that Scott experienced.
I did this for ADC/Tyco 20 years ago, before they were the same company. We used a Tyco press that was able to sense overpressure and stop if something was wrong. It worked extremely well. It was all in the set-up.
You certainly do not need much in the way of pressure. You must have a precise shut-height control also.
But I know it can be done, even on small backplanes with connectors right next to each other.
-----Original Message-----
From: TechNet <[log in to unmask]> On Behalf Of Steve Gregory
Sent: Thursday, August 22, 2019 4:50 PM
To: [log in to unmask]
Subject: Re: [TN] [External] [TN] Minimum PCB thickness for press-fit technology?
Hi Scott,
Thanks for the feedback. These will be connectors, I don't know what manufacturer is so I can't dig into a datasheet to learn what PCB sort of spec's will be required. I'm doing a budgetary quote for some boards that haven't been designed yet. The customer is asking for some very rough labor numbers based on a general description of the PCBA like: 150 single-sided SMT components, 5 through hole connectors, 4 press fit connectors, 6-layer, 5" X 8", .031" thick PCB. When I saw the press-fit and .031" thick PCB is what got my attention. I've never pressed any connectors into a board that wasn't at least .062" thick...
Steve
On Thu, Aug 22, 2019 at 3:37 PM Decker, Scott Collins < [log in to unmask]> wrote:
> Steve,
> I think the answer is, "it depends". We have a rigid-flex board that
> is .093" thick and had issues with press fit nuts, but ended up
> increasing the hole size a tiny bit to lessen the force required to
> press the nuts in. We had a supplier using a 5 ton hydraulic baring
> press to do the pressing and they promptly delaminated the boards.
> (That was not needed to press them either, you could do it with a pair of pliers almost.) Ouch!
> Anyway, I have done .031" boards in the past and used Pem nuts in
> them just fine. Just take note that they recommend different hole
> sizes for PCB versus sheet metal, etc. That said, in our case,
> increasing the hole size slightly, prevented the board from getting
> damaged during the press operation. The key to watch is the press
> section of the nut/spacer, and that it's not any longer than the board thickness.
> I've done both plated and non-plated holes and had good results in
> both cases so plating wasn't an issue in my cases at least. I would
> suggest that if you do plate the holes, don't use HASL for the finish,
> that will cause issues sometimes. In all cases too, the compression
> mode was to pull the nut into the PCB and not push it away/out. In the
> case of the .093" board, the press was just enough to hold the nut in
> during assembly and a few on off cycles so we've not had any issues
> with the larger hole size. Don't know if this helps or not, but...
> Later...
>
> Scott Decker | Senior Engineer, PCB Design Services CID+ | Electronic
> Systems Center COLLINS AEROSPACE
> 3445 S. 5th Street, Suite 170, Phoenix, AZ 85040 U.S.A.
> Tel: 602 308 5957 FAX: 602 243 2347
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> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
> Sent: Thursday, August 22, 2019 1:05 PM
> To: [log in to unmask]
> Subject: [External] [TN] Minimum PCB thickness for press-fit technology?
>
> Hi all!
>
> I thought I'd throw the question out there while I'm google-ing for
> it, is there a minimum PCB thickness that you would want to use
> press-fit technology? I'm thinking it's .062", I think I read that
> somewhere, now I'm trying to find it. But a .031" thick PCB seems too thin. Thoughts?
>
> Steve
>
> --
> Steve Gregory
> Kimco Design and Manufacturing
> Process Engineer
> (208) 322-0500 Ext. -3133
>
> --
>
>
>
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Steve Gregory
Kimco Design and Manufacturing
Process Engineer
(208) 322-0500 Ext. -3133
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