Jean-Francois

I went to the Cambion site and looked at 'Turret Terminals' and the like,
especially the type that require swaging and the examples that they have
there indicate a fairly tight tolerance hole for the size barrel of the
terminal. They do however supply a recommended hole diameter for the board.
I would expect that the designer would use the recommended hole size for a
part and deviate only if it does not work in his/her application.
I think you need to elaborate on the specific issue you are having, what
part and barrel diameter and tolerance is being used as a 'test point' and
the hole diameter and tolerance call out that you are verifying in order for
someone to make a determination about the correctness of it.

Most swage operations are done with a tool that is designed specifically for
the terminal to be used.. giving the installer the desired ferrule or funnel
shape desired to retain the terminal. The diameter of the hole that the
terminal or pin is being installed into must fall within the recommended
tolerance rage or the results will be undesirable.

There is an interesting spec available online that was published by NASA
that covers the soldering of swaged terminal posts and the like...

Here are some links to check out for your research...

http://www.quality-control-plan.com/pdf/NASA-STD-8739.3.pdf

http://www.cambion.com/Main/catalogue_solder_terminals_non_insulated.htm

Cambion offers two types of punches - roll and flare.   Often both will
appear in the recommended tooling information for a given product.   As a
general rule a roll swage should be used where no soldering is to take place
on the swaged side of the board and a flare swage where a post assembly
soldering operation takes place.  Note that a flare swage is not expected to
be more than finger tight prior to soldering - the mechanical strength of
the joint is greatly increased by the solder fillet.

In the old days, back in the 1970's we made boards for use by Hughes
Aircraft that used funnel shaped 'eyelets' to carry the signals through to
the other side of a 2 sided PCB. This was when plated though hole technology
was in its infancy and was not recognized as a reliable method for
interconnections on the board... They required a funnel type of staking for
these copper 'eyelets' that allowed them to be soldered when passing through
a wave soldering machine. The hole diameter to funnel eyelet diameter was
critical because the barrel would split if it was over stretched.

But to answer your question concisely, we always referred to the
manufacturer's recommended hole size for any given terminal post or eyelet
used on a board. IPC 2221 8.2.10 refers to eyelets and the critical
relationship between the barrel diameter and the hole diameter and indicates
that the difference between the two shall not exceed .006 in. or 0.15 mm.

Also IPC 2221 8.2.9 refers to Solder Terminals and there are some details
specified in figure 8-17 and 8-18.

Most of us are not installing a terminal or eyelet as a test point. I use a
100 mil diameter pad that is accessible to a spring contact or test probe
tip usually from the secondary side of the board (solder side). The 'one
time use' nature of test points makes them expensive if you install a
terminal in the board... the pad is much cheaper and less likely to fail due
to some soldering operation variance.

I hope that helps a little, good luck with your design!

Best Regards.

Bill Brooks
PCB Design Engineer , C.I.D., C.I.I.

-----Original Message-----
From: Bissonnette, Jean-Francois [mailto:[log in to unmask]]
Sent: Friday, January 16, 2004 6:02 AM
To: [log in to unmask]
Subject: [DC] Hole size for test points

Hi

I've posted this message on Technet but I think here would be much more
appropriate:

I would like to know how to calculate a hole size for a test point that will
be swaged.
Is there a specific ratio between hole size and turret size.  For instance
we have a board
that is 0.094" thick and the "barrel" of the turret is .135".

Thanks!

Jean-Francois Bissonnette
Quality Control, Electronics
Vapor Rail

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