This is a familiar twist on the same old drill. Counter bore is a last ops
type process where you risk losing a perfectly good PWB to some lousy bore
down the hall. If they didn't get the hole right, which should be part of
some automated cad-driven system how are they going to get a manual process
correct. If the PWBs are cheap and not high tech then go ahead, but if they
are that then they shouldn't be that expensive, so why not throw them away
and save yourself some worry.
If they are high-tech, then you need to verify that the design allows you
the clearance to counter bore and not cut into traces or internal planes
that were designed or checked to the hole that was originally drilled. You
also need to verify that the as designed minimum dielectric spacing has not
been compromised or that the overall functional integrity has been
diminished.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Green, Mike
Sent: Monday, May 23, 2005 1:57 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Terminals
I might suggest that if your board size is not the one specified by your
terminal, counterbore the board until it is the right size. Terminals are
designed to fit a specific size. It is up to the designer to supply a
board of that size.
Mike Green
Production Design Engineering
Lockheed Martin Space Systems
Sunnyvale, CA 94089
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Brooks,Bill
Sent: Tuesday, March 29, 2005 9:00 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Terminals
Hi Robert,
Yes... I recall the acceptability of cracks in terminals and eyelets...
Thanks for the reminder. It's been a long time since I have had to deal with
them. Your last comment on PTH swaging of terminals... I thought they didn't
allow that in the Mil Specs... there was an issue with damage to the PTH I
think... We always added multiple vias around any non-plated or plated
mechanical hole that was used for ground and/or mounting or if the board was
under any mechanical compression so as to guarantee that the continuity of
the pads on top to the planes and pads on the bottom was maintained by a via
free of mechanical compression... regardless of any single failure in a
mounting or swaged terminal hole. It was just 'good insurance'.
Do you have the specific spec numbers for those? I'd like to look at them
again.
Best regards,
Bill Brooks - KG6VVP
PCB Design Engineer , C.I.D.+, C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 e-mail:[log in to unmask]
http://www.dtwc.com http://pcbwizards.com
-----Original Message-----
From: Langston, Robert L [mailto:[log in to unmask]]
Sent: Tuesday, March 29, 2005 3:08 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Terminals
Cracking of the solder terminals is a subject that has been around forever
and is not confined to any one supplier.
IPC,MIL, and NASA Spec's address this and allow end item terminal cracks of
a maximum of 3, if they are located at least 90 degrees apart, and none
enter into the barrel of the terminal.
Final swaging in a PTH should allow rotating the terminal with finger
pressure.
Bob
-----Original Message-----
From: Brooks,Bill [mailto:[log in to unmask]]
Sent: Monday, March 28, 2005 1:02 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Terminals
They may have changed materials in the alloy on you...
Check with the manufacturer of the terminals to make sure the alloy has not
changed. Or if that isn't it, then maybe the plating process is affecting
the brittleness of the material? Dead soft copper is very malleable and
brass is less malleable. Most of the terminals I have used in electronics
are tin plated brass with the only exception being copper eyelets back in
the 1970's.
I assume that you have not changed the hole size in the board and the board
thickness is the same... The speed with which the material is 'cold formed'
may also come into play... If you are using automated tooling the stops on
the swage tool will have something to do with preventing over stretching the
material to the cracking point. The 'very old' terminals comment you made
makes me suspect that the materials have changed rather than the process of
forming them with the Cambion tool. Just a guess. Work with your supplier
and see if the old batch of terminals came from a different source or used
different materials.
Best regards,
Bill Brooks - KG6VVP
PCB Design Engineer , C.I.D.+, C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 e-mail:[log in to unmask]
http://www.dtwc.com http://pcbwizards.com
----------------
Hi Technetters:
I would like to know if anybody has experienced difficulties in flaring
the flange of solder terminals. On J-std-001C 6.2.3 it states that the angle
of flare shall be between 35 and 120 deg. Some terminals crack even if they
are flared at 36 deg. Other terminals can be flared at 120 deg and not
crack. I suspect that the plating finish has a lot to do with it.
Regards,
Ramon
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