Adhesion of Thermoplastics to Materials used in Electronics (Tin)

Electronics manufacturers are under legislative pressure to find alternatives to non-recyclable thermoset PCBs for production of electronics. A candidate process being developed at Loughborough University uses injection over-moulding to embed components in a polymer matrix, prior to interconnection by electroplating of the moulding or by printing of a conductive ink. Crucial to the manufacturing quality and reliability of products made using the process will be the adhesion/interaction between the metallisation surfaces, such as tin, of the electronic components and the overmould. In this work, a set of experimental procedures developed to study the interaction forces and adhesion between tin and thermoplastics in the melt and in the solid state are reported. Direct adhesion force measurements in the solid state will be undertaken using Atomic Force Microscopy (AFM) with tin functionalized probes. A novel method of functionalisation using a Focused Ion Beam (FIB) apparatus is described. Trials of a Wilhelmy plate method for measuring the contact angle between thermoplastic melt and tin foils are also described, together with a wetting force method which is in development. Finally trials of in situ injection moulding methods for creating artifacts suitable for tensile adhesion strength measurements are described.