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Structure of ball grid array/permanent semi-elastomeric thermally conductive crumb rubber reinforced stencil/printed circuit board interconnects

Panagiotis Frantzis, Panagiotis Karydopoulos, Nikolaos Karagiannis

The aim of this paper is to investigate the structure of a BGA/Stencil/PCB interconnect, i.e. the structure produced when a permanent semi-elastomeric stencil is formed or placedwithin a usualBGA(BallGridArray) / PCB(Printed Circuit Board) interconnect.Apermanent semi-elastomeric BGAstencil is a membrane that consists of arrays of perforations arranged in a grid manner. The membrane is produced from a thermally conductive material that is made by mixing synthetic rubber latex or styrene acrylic emulsion binders, conductive filler, and crumb rubber. The development of the new family of stencils transfers knowledge from the field of materials to the field of PCB manufacture/rework andmay provide benefits to include increase in thermal conductivity, reinforcement with crumb rubber, inhibition of whisker formation/growth, protective coating to prevent the formation of corrosion products, and no need to use adhesives. The BGA/Stencil/PCB interconnects have the potential to extend the service life of a PCB and offer amore reliable operation, especially for PCBs used in high-risk applications (aviation, shipping andmilitary applications). It is the first time that suchmaterials are being used in highly sensitive electronic hardware applications.