Gary Griffin wrote:
>
> Does anyone know where I can find information on the dielectric
> constants of pre-preg materials used for PCBs?
>
> Gary

The supliers of the materials.

Depending on the supplier the Er of FR4 material varies from 3.8 to 4.9.The actual Er
that you as a laminator of the multilayer board obtain may not be the same as the
suplier of the material would publish. The Er depends on the mass of glass cloth, the
weave (or at least the gaps in the weave) and the mass of resin left after bonding. You
should bond samples of the prepreg between copper foils, measure the thickness, check
its capacitance and from there calculate the Er. Better still send the samples to your
supplier and have him do the test.

Roger Hammond

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