Silicon Die Encapsulant

I want to encapsulate a silicon die directly wirebonded on PCB. I am looking for the product used for that application. You may ever saw it, it's a little drop of product, usualy it's a thin black stoff that recover the silicon die on a PCB. It is used by the cell phone indystry per exemple.

This product must have a very low CTE and must not retract when polymerizing.

Thanks for help !