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PCB related question

Hi everyone, Here's the dilemma. We want to ensure accurate positioning of a SMT connector.

We can specify better accuracy on the drilling of the pcb (for alignment pins) and place fiducials on the board for AOI pick and place.

However, we want a visual feedback after assembly.

I've proposed putting a pattern on the foil with 1 mil steps and a reference mark.

A kind of vernier if you will. I'll be putting a big shape so it's easily manufactured, but how well will 1 mil steps come out?

Anyone every tried this? Does this have a name?

And yes, I will be calling our PCB shop.

Reply to
a7yvm109gf5d1
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You will not be able to get 1 mil traces on your PCB. How small you can go depends on the board house, and copper thickness, but I would expect no smaller than 6-8 mils. If you choose this path, you will need to leave some soldermask off the spot where you want to view the traces.

Does your SMT connector have alignment pins on it? That should take care of any drifting in reflow...

Chris

Reply to
Christopher Ott

And they will tell you they can't do 1mil traces. 3-4 mil maybe if you pay them.

How much positional accuracy do you need on this connector?

If you have physical allignment pins on the connector then I can't see why you need to even check the allignment after assembly?...

Dave.

Reply to
David L. Jones

I'm not really asking for 1 mil traces. I'm drawing a solid piece of copper of about 100x50 mils, but it has steps on it that change by 1 mil. It looks like stairs. I figure that there will be enough of a difference on average to serve as a visual reference. There are no features below 10 mils on my copper piece.

It does, and it doesn't. We are having all kinds of problems.

Reply to
a7yvm109gf5d1

This will etch out as a diagonal line. Even if the traces are 10 mil, you are asking for 1 mil resolution...

What kind of problems? If there is an alignment locator on the part, and you have an alignment hole on the board, it seems reasonable that you should get some decent accuracy. Is the locator hole too large? Are you using too much paste and floating the parts? What kind of problems specifically?

Chris

Reply to
Christopher Ott

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