New Chemistries for Advanced Printed Circuit Board Fabrication

The relentless demand for enhanced electronics processing capabilities is causing major changes in all sectors of the electronics industry, particularly in interconnection and packaging. Printed circuit board line widths and hole diameters are decreasing and new substrate materials are finding increasing use. In addition, newer high density interconnection and packaging techniques such as multi‐chip modules, chip on board and TAB are beginning to move into production. These developments are placing new demands upon PCB manufacturers, who are in turn driving their process suppliers to provide the enabling chemistries. These demands have, for example, encouraged the development of high resolution electrophoretically deposited photoresists, photoimageable solder masks and the chemical deposition of solder from solution. However, against this requirement for improved and new processing chemistries there are growing environmental pressures which have necessitated changes in both materials and processing methods, a typical example being the growing interest in direct plating of via holes. This paper reviews the challenges and opportunities in advanced PCB fabrication from a processing chemical supply perspective and discusses the new processes and chemistries that will enable the PCB industry to produce state‐of‐the‐art boards in an environmentally acceptable manner.