This project has the goal of developing a new process able to guarantee a high adhesion between the copper innerlayers of a multilayer and the dielectric material made of high glass transition temperature (Tg) resins.
The recent introduction of the RoHS European Directive, which imposed a reduction of use of hazardous substances in electronic and electric equipment (especially Pb and Cd), influenced a lot the printed circuits industry. In fact the “historic” soldering technology, with Sn/Pb alloys, of electronic components on the boards has gradually been replaced with the new “lead-free” technology.
These “lead-free” soldering alloys are used at about 270 °C of temperature that means about 20 °C more than Sn/Pb alloys.
For this reason the printed circuit boards should be resistant to high soldering temperatures, in order to be adapted to the new soldering technologies.
High glass transition temperature (Tg) resins (about 200 °C) are now more and more common for multilayers manufacturing because they are resistant to the soldering process with “lead-free” alloys.
The current technology for multilayers printed circuit boards manufacturing needs a chemical treatment of the innerlayers copper surface, with an adhesion promoter depositing an organo-metallic film able to supply high adhesion (about 1 kg/cm with low and medium glass transition temperature (Tg) epoxy resin).
The copper surface treated with this adhesion promoter, if used with high glass transition temperature (Tg) resins, gives about 0.5 kg/cm of adhesion, not sufficient to assure reliable performances.
This project has the aim of modifying the current process of adhesion promotion in order to increase to about 1 kg/cm the adhesion got with high glass transition temperature (Tg) materials.