[SI-LIST] Re: Why are PCIe card edges beveled and DIMMs aren't?
- From: "Bert Simonovich" <bertsimonovich@xxxxxxxxxx>
- To: <leeritchey@xxxxxxxxxxxxx>, <jeff.loyer@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Wed, 25 Mar 2015 13:51:23 -0400
Jeff,
I think you will find DIMMs are also chamfered. I just looked at some I have
lying around in my drawer. In addition to providing a guide for insertion
and reduce the wear and tear on the socket contacts, it also trims off the
thin trace used to short all the fingers for plating. To plate the fingers,
the artwork extends the fingers past the finished edge of the board with a
thin trace and shorts all the pins together - usually extending from one
side of the fingers. After plating, chamfering the edge removes most of this
thin trace. The fingers are also set back from the finished board edge to
ensure the edge remains plated with gold to prevent corrosion.
-Bert
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Lee
Sent: March-25-15 12:26 PM
To: jeff.loyer@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Why are PCIe card edges beveled and DIMMs aren't?
Beveling has its origins in the old days when we had edge connectors that
fit .063 thick PCBs. If we did not bevel the edges, the sharp corners
collapsed the pins in the connectors.
Old guys sometimes remember such trivia!
-----Original Message-----
From: Loyer, Jeff
Sent: Wednesday, March 25, 2015 9:06 AM
To: si-list (si-list@xxxxxxxxxxxxx)
Subject: [SI-LIST] Why are PCIe card edges beveled and DIMMs aren't?
Does anyone know why they bevel PCIe cards but don't bevel DIMMs? We're
guessing that they want less insertion force for PCIe cards which ostensibly
get swapped more often, but wonder if anyone knows the actual
history/explanation. It seems (to me) that removing the bevel from PCIe
cards would be a welcome change for manufacturing and signal integrity
folks.
Thanks,
Jeff Loyer
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