Ian:

The general rule is that laminates .031 inch and greater are specified as received, over copper.  Laminates .028
inch and thinner are specified as core, i.e. bare laminate.  Analysis of the thickness tolerances for the two
classes will explain the difference.  Generally the thicker (.031+) class has a tolerance of +/- .005 (or
greater).  The thinner (.028-) class has a tolerance of .002 or less.

The short explanation is that double sided materials (.031+) have a tolerance that will accommodate most copper
cladding while inner layer materials (.028-) are specified with a tighter tolerance but without the copper
cladding.  More specific details should be obtained from your laminate supplier.

Hope this was of some help.  Best wishes:

Don Vischulis

Ian Squires wrote:

> Help,
> Looking at substrate thickness on PWB
> if i specify 2oz copper 1.6 mm would the substrate be the same size, thicker or thinner than 1oz copper 1.6 mm.
>
> Many thanks for any speedy replies (one of those urgent ones where the boss man is standing over me).
>
> Regards
> Ian Squires
> Senior Production Engineer
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