Investigation of over-moulded hybrid metal/polymer devices

Miniaturized devices with increased functionality can be obtained by means of incorporation of metal micro parts in a polymer matrix. They allow achieving both conductive circuits and mechanical functions in the same device, enabling design of MIDs with enhanced characteristics. New design principles, in-process manufacturing technologies, as well as testing methodologies have to be established in order to be able to develop such integrated devices.

In this paper an investigation of the bonding between miniaturized metal insert and a polymer matrix is presented. A special demonstrator was designed and manufactured by over-moulding and hot-embossing. The bonding strength between the insert and the plastic part was tested by means of a tensile test.

A variety of parameters was studied in order to investigate their influence on the bonding: different polymeric and metallic materials, insert thickness, metal surface roughness and texture topography, surface treatment and coating, i.e. metal insert designs to improve polymer/metal interlocking and tensile test speed.

Results show a strong influence of the surface properties and of the employed material on the bonding strength. The proposed testing procedure provides properties, characteristics, and data to be used when dimensioning and designing MIDs which involves conductive and mechanical functions.