Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

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Re: Press-Fit



Press-Fit | 7 November, 2000

WE are using press fit connnectors on a range of boards, one of which is posing me a few process questions . The Machine is a fully automatic machine. The problem is intermittent and I can't seem to put a finger on it. An array of connectors ( consisting of a single, double and triple modules)are pressed fitted in one single press,the two problems I'm seeing are : 1) time too time the centre of the array of connectors won't sit completely flush with the board (0.006-0.008" of the board ), and secondly the connector which is sat on the corner, every now and again the pins on the very end row will not fully insert, the reason for this is because the pins are slightly deforming before the connecor is fully inserted,and I don't know whats causing this deformation on some boards and yet it's alright on others. Any help on the above issues will be appreciated.


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Re: Press-Fit | 7 November, 2000

We see this type of problem with a couple of our boards. It has proven to be a problem with the board. During manufacture at the board house the thru holes for the connectors are plated a little too heavy causing a smaller hole. If you haven't already I'd measure the hole diameter to insure it is up to spec. Another problem would be if your back plate has an imperfection or not solid/rigid enough (another of my associates tried to use a hard plastic type material), while we're at it your top die/block should also be rigid. I use aluminum for all my "press fit" tooling.

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Peter Barton


Re: Press-Fit | 7 November, 2000


The most common cause for this problem is a variation in the plating thickness of the through holes, particularly if they are Sn/Pb solder levelled PCB's.

Most pressfit connectors require a fairly tight control on the diameter of the holes to which they are fitted. If there is too much plating in the holes it interferes too much with the connector pin. This can lead to the connectors not being fully inserted and/or individual pins being deformed as you describe.

Does your automatic machine rely on a preset travel or a preset insertion pressure being reached to stop the insertion part of the cycle? If it is the latter then it would more or less confirm that variation in hole plating thickness is probably the problem.

Have a look at how far the connector pins have come through on the other side of the PCB. Are they all the same height or do they vary?

Hope this helps,

Pete B.

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Re: Press-Fit | 7 November, 2000

There is a variation on the pins that come through on the other side. The pins that are deforming are roughly half the size of those which aren't deformed.There are no witness marks on the pins that are deformed, suggesting that the pins aren't fouling on anything on their way down. I have taken photographs showing what I'm going on about. If you guys send me an email address I will forward them on.Isn't it too much of a coincidence that variation in thickness only seem to occur in those holes where the connector ends ?


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Re: Press-Fit | 8 November, 2000


If you send the info to I'll be happy to have a look and give you my view.

Pete B

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