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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Min Hole/Pad distance to edge of PCB

Stuart Adams

#4666

Min Hole/Pad distance to edge of PCB | 13 March, 2000

Assuming agressive design rules what is the minimum distance I can get away with between the board edge and a SMT pad and between the board edge and a plated mounting hole ???

(The board is only 1"x2" and the mounting holes are 80 mil dia, 125 mil pad - I have a fixed size board and fixed component set and am running out of space :)

Thanks, Stuart

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Ioan

#4667

Re: Min Hole/Pad distance to edge of PCB | 13 March, 2000

Stu,

it is good you know that there are limitations and you want everything. Wish our designers work like that.

So, the limitations we impose are dictated by the rails of the insertion and dispensing machines. Normally a .150" keepout will make a safe design. Honestly, I don't think you can make it smaller than .120", or the paste will get smeared.

Ioan

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Nancy V

#4668

Re: Min Hole/Pad distance to edge of PCB | 14 March, 2000

Would this dimension be the same if the board is panelized and the board has break aways?

Nancy

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#4669

Re: Min Hole/Pad distance to edge of PCB | 14 March, 2000

Bingo!!! By panelizing and adding breakaway rails (as Nancy says), Stuart can pour copper up to his board fab's tolerance from the board edge. Traditionally, he just wants to make sure no copper shows on the edge of the board. Then again, it's his board and he can waive the IPC-A-600 requirement that no copper shows. (He may regret waiving it later, but that's a different story.)

And that doesn't even touch on other benefits of panelizing.

Good luck

Dave F

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#4670

Re: Min Hole/Pad distance to edge of PCB | 23 March, 2000

Stuart,

My suggestion is a DFM meeting (most of the process people dream about a meeting like this, and luckily, I've been to a few) with:

- project manager (if there's one) - customer service rep (annual volume, lot size, product life) - smt process person (machine limitations, reflow oven limitations, preferred board width to reduce setup time, per previous experience) - blank pcb manufacturer rep (suggested final panelized board size for lowest cost per board) - wave soldering process person (selective soldering required?, preferred board width to reduce setup time?) - depanelization process person (v-grove? break-away? preferred clearance between each panel copper?!!!!) - packing process person (new esd bags, new cardboard boxes required?)

Depending on the company size and/or organization you might not have someone for every position given above. Few may be covered by one person. This meeting will not only answer your question but others' and will prevent possible mess caused by surprises...

Hope this doesn't sound too much like a perfect world...

Regards Erhan

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