How are PC boards made?

Usually the board house buys copper foil clad laminate and etches the unwanted stuff away, then electroplates the bores of the through-holes.

John

OK, but how is the original copper foil attached to the board? Is there an adhesive involved, or is it deposited in a molten or powder state somhow?

Don

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AIUI, the laminate they buy comes with a copper weight of about 1/2
an ounce per square foot, which is what they etch,  and then they
plate what\'s left to get to the customer\'s specified
weight/thickness.

nb

In a nutshell...

Copper foil is glued to a "substrate" board (anything from plastic to teflon, usually fiberglass). The fab shop drills all the holes in it, then plates (usually electrochemically) additional copper over it all (making the foil thicker as well as electically connecting through the holes). Then, a mask is applied over the copper and whatever isn't masked is chemically removed.

Or they pretend to. I almost never get 1 oz or 2 oz when I specify it. On one of my fab drawings, it says

START WITH 2 OZ COPPER

which helps.

John

As far as I know, roll copper foil is epoxied to the laminate, which is usually epoxy-glass. The foil is usually "black oxide" treated on one side to stick better.

For some exotics, generally microwave stuff, the copper is electroplated onto the substrate and not glued. These are usually teflon or polyimide boards, low-loss stuff, and they want both good adhesion and a micro-inch smooth, pure copper surface on both sides of the copper.

John

PC board material has a solid copper foil glued (or otherwise attached) to the fiberglass. When you make your board, any copper that doesn't look like your circuit is etched away.

--
Peter Bennett, VE7CEI  
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--
So does incoming inspection and rejection.

And for multilayer boards do they simply epoxy each layer on top of each other layer?

-phaeton

Multilayer ( 4 or greater) actually have prepreg (a form of glue) as the outer layer

A typical stack might look like:

Top ------------ 1 oz Cu Prepreg ---------- Inner 1 ----------- 0.5 oz Cu Core ----------- [FR4, typically. Depends on application] Inner 2 ----------- 0.5 oz Cu Prepreg ----------- Bottom ------------ 1 oz Cu

[thicknesses and types of core / prepreg are carefully selected for impedance controlled boards]

Cheers

PeteS