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Tight fitting Backplane dimensions (IEEE 1101 Subrack) / Panelizing
639 1 Sep 07.2019, 10:15:46

Hello,I'm constructing a modular backplane for a 19'' subrack. Each slot, 4 units wide, has it's own backplane segment which houses the DIN 41612 connector.
The standard IEEE 1101.1 tells me the width of a 4 unit frontpanal should be: 4 x 5.08 - 0.3 [+0 / -0.2] = 20.02 mm
I'm planning to order in PCB manufacturer in China. They specify their outline milling / v-scoring precision at ±0.2mm.
Please have a look at the attached picture of the board.
The curved shape of the board is my solution to the 7.62 mm distance from the sidewall of the subrack to the first mounting hole. The boards are supposed to be mounted very easily. This way you can just align the first one to the side wall. (I hope  )
My questions are: 

How much clearance should I have between each segment so ensure them fitting nicely besides each other?

I want to panelize the boards before manufacturing. Would you put the V-score at the top and bottom? The boards have to fit exactly in the subracks mounting rails. (128.7 mm +0/-0.3)

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A****min

Sep 11.2019, 09:29:13

Clearance is generally based upon how much flex your rail system and board give, the Idea is that when its being moved and jostled about, the boards should not flex enough to contact one another, e.g. electrolytic capacitor tops with throughole solder joints of the next board. for this I would say 0.5mm - 1mm depending on your manufacturing method, skewing closer to 1mm if you plan to double load and dont have an offset already planned into your front plates,
For similar reasons you generally will see higher components set back a bit from where the rails start, this is because the board can be quite unparrellel at insertion, and you both dont want to hit the next cards components, and dont want to damage components near the backplane connector until its properly being guided.
As for V-scoring, the edge is going to be rough, plan atleast 0.06mm of margin on vscored edges, if you need perfect dimensions you need routing.

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