Estimated reading time: 5 minutes

Standing Room Only at ICT's Winsford, UK Seminar

Past Chairman of ICT Steve Payne gave a thought-provoking overview of laminate-based semiconductor packaging and system-in-package technology--effectively an insight into some applications of PCBs in miniature.

With some silicon dies now having as many as 5,500 input-output connections, wire bonding was a not a practicable interconnection option and a flip-chip approach was preferred, with a laminate substrate within the package. This was compatible with BGA-style area-array packaging and gave the electrical benefit of very short interconnects, but mechanically the interconnections were stiff and rigid. Therefore for high reliability applications there was a critical need to match thermal expansion properties of silicon and substrate, and to aim for a low modulus to aid mechanical compliance. Very thin substrates were preferred, to minimise z-axis stresses, and materials without woven-glass reinforcement were favoured, which gave the additional benefits of more efficient laser drilling and the absence of CAF effects.

Typical substrate design rules were 25 to 35 micron track and gap, to enable conductor routing from flip-chip solder bumps at pitches trending towards 100 microns, 50 micron via holes and 100 micron capture pads, with a construction based on build-up technology having dielectric thicknesses of 40-50 microns. Semiconductor packaging and system-in-package could use the same substrate technology, and there had been heavy investment in Asia to satisfy high volume requirements for smart phones and tablets. The global market for semiconductor packaging materials was expected to grow to over $25 billion by 2015, of which laminate substrates represented the largest market segment, with a growth forecast of 8% over the next five years.

Although the manufacture of semiconductor substrates was technically challenging, they were in fact miniature PCBs and Payne indicated that there was a significant and growing requirement for high-reliability medium-volume substrates in Europe which represented a substantial market opportunity, with typical selling prices in the range £20 to £40 per square inch.

Bill Wilkie brought proceedings to a close, acknowledging the generous support of CC Electronics, and reporting a record number of advance registrations for the ICT/NUKCG Foundation Course in April and a high level of interest in the ICT Annual Symposium and 40th anniversary celebration dinner in June (full details at www.instct.org).

The ICT continues to gain momentum, with membership now well into the 300s, and the Winsford Seminar was another excellent opportunity for members to share knowledge and to network with their peers in the UK PCB industry.

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