Eurocard Format PCB

I've been looking at some various PCB formats and found something I don't understand.

The original VME Bus format was called the Eurocard 6U and 3U formats. The 6U is 234mm X 160mm and the 3U is 100mm X 160mm. The 3U mechanical format was then adopted by Compact PCI (and some others).

As everything kept getting smaller some applications used a "Half Eurocard" format which should be 100mm X 80mm. However in looking for some cases to fit this board size I ran across several SBC's that were "Half Eurocard" but were 100mm X 71mm. Other boards use Half Eurocard to mean 100mm X 80mm. I'm very curious as to why?

I was under the impression that all the extension pieces for VME cards came in 60mm increments. So saying a half Eurocard was 100mm X 100mm would make more sense (at least to me) but a 9mm discrepency seems odd.

In any case, I did not find any cases for either of these sizes. (lots of stuff slightly bigger and smaller but nothing that you would just be able to drop a board into.)

Thanks for helping settle my curiosity.

Kevin

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Kevin C. Castner kccnospam at glenevin dot com

"Good ideas are not adopted automatically. They must be driven into practice with courageous patience." -- Adm. Hyman Rickover, USN

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Well, their manufacturers are wrong then. It is not a half Eurocard.

Because they are right. That _is_ half a Eurocard.

True.

That would be a 5/8ths Eurocard, but it is more practically known as a square Eurocard. It is a legitimate Eurocard size, but not widely used.

It is a shame the PC104 standard did not chose this size, as gives a bit more room for I/O connectors and fits in Euroracks.

Just how many manufacturers use that size? If more than a few, there may be a good reason.

Well, Fischer (German, very good) and Hammond (Canadian, almost as good) make aluminium extrusions for 100 mm cards to slot into. Usually comes in

160/220 mm lengths but if you want more than a few I'm sure they will sell you it in any length you want. If you just one a few then any light machine shop with a mechanical saw could cut it down to the size you want.

Don't forget that the PCB may be 80, 100, 120, 160, 220 mm but you may need to allow a few mm for connector overhang. I've seen Eurocard cases 5 mm bigger than Eurocard sizes to allow clearance front and back.