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Subject: Re: p.c.b forum

Date: 05/04/00 at 2:14 PM
Posted by: John W. Childers
E-mail: jwchilders@goldengategraphics.com
Message Posted:

In Reply to: Re: p.c.b forum posted by shoshi on 05/04/00 at 3:09 AM:

Vias are usually uncovered in prototypes, giving access to points on the circuit for debugging. They may be tented on the top side and open on the bottom side in production boards where the vias are being used as probe points for bed-of-nails test fixtures.

There may be a mixture of tented and bare vias. It all depends on what is needed for that board. Tented vias can't be shorted out by stray flakes of metal, so can improve reliability. But a tented via can not be probed electrically for test or debugging.

I'm *not* familiar with double reflow. What is that?

>Do you know the spec for iner layers?
I'm Not sure what you're asking. Copper weight is usually 1 ounce (that is, 1 ounce per square inch) on inner layers.

Thanks for visiting my site. I would be delighted if your would sign up for our free on-line training pilot project.

John


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