hi smwk,

If I am not mistaken, the second page of the datasheet shows a suggested PCB layout for the chip, with suggested biasing and matching components. I am not sure what "duroild" is ... but I am guessing it is a spelling error ... and meant to say "duroid" 6010 from Rogers Corp.

It is fairly common for manufacturers to do this ... especially when power dissipation approaches 1kW !

Good luck ...