Permanent Non-Etching Adhesion Promotion System for Solder Mask Applications

With the constant drive for miniaturization in the IC substrate market, and the increasing performance demands being made on completed assemblies, the use of etch based adhesion promoter systems is coming into question. Unlike the current technology, Atotech´s Secure^TM HFz process enhances the adhesion between a Copper conductor and a solder mask with no etching to the conductor itself. This unique approach is designed to meet the current and future market requirements typical to ultra fine line IC substrate manufacturing (sub 10/10 mum line and spaces can be achieved). This work details the Secure^TM HFz process and discusses testing carried out, in which, the adhesion properties are attained for treated surfaces and a range of solder mask materials. The tests show that surfaces treated with this non-etching chemistry exhibit comparable or greater adhesion strength when compared to a traditional etching based system. Long term reliability is also evaluated through HAST (Highly Accelerated Stress Test) where again overall performance is equivalent to, or better than the current etch based process. The summary of this work is that Copper surfaces treated with the Secure^TM HFz process offer a technical advantage in ultrafine line and space applications due to their improved adhesion to solder mask materials with no changes, critically reduction, in overall track geometry.