Still pushing the envelope Roy? It's that TOP GUN Blood coursing through
your veins... I know it!
I have not seen anyone do that, controlled depth drilling, before. Sounds
touchy at best. Might be a re-producability issue. How tightly can they
control the tolerances? Why not use blind vias... are they more expensive?
Here's another thought... and something I have seen, bonding or just
loosely placing an etched aluminum sheet under the board.. it doesn't need
to be very thick... just enough to clear the via pads on the back
side...like .032 sheet stock.
Also I have done a board where we left the pads off the back side, and had
them countersink the vias from the backside, to gain clearance from the
chassis and ground plane. I think we had them screen soldermask into the
countersinked holes just to make sure... anyway keep coming up with ideas...
it's a problem without an elegant solution. Good to see you're still out
there designing.
Bill Brooks
PCB Design Engineer
DATRON WORLD COMMUNICATIONS INC.
3030 Enterprise Court
Vista, CA 92083
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
mailto:[log in to unmask]
IPC Designers Council, San Diego Chapter
http://www.ipc.org/SanDiego/
-----Original Message-----
From: Beckman, Roy [mailto:[log in to unmask]]
Sent: Wednesday, January 03, 2001 4:01 PM
To: [log in to unmask]
Subject: [DC] Controlled depth drilling
Welcome to the real new millennium!
One of our board shops has suggested an alternative strategy to handle
through-hole vias for a PCB mounted on a flat metal plate. They suggest
that we
remove the bottom pads on all non-ground vias and then they will drill the
plated holes out to a depth of 0.010". (The finished hole sizes for these
vias
are 0.012" and 0.018".) The previous strategy was to drill holes in the
mounting plate at the via locations.
Has anyone had any experience with this scenario?
Can you recommend any board shops that do this?
How reliable are the vias after this drilling?
Thanks for your feedback,
Roy
Roy H. Beckman, C.E.T., C.I.D.
Senior PCB Designer
Harris Corporation
Harris Canada, Inc.
6732 - 8th Street, N.E.
Calgary, Alberta, Canada T2E 8M4
Phone: 403-295-4758
Fax: 403-295-4622
email:[log in to unmask]
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