(Part one, Part two, Part three - will open in new window) 

The electronics industry’s mantra has for many years been “Smaller, Faster, Lighter, Better and Cheaper.” However, as I/O counts continued to rise on the chip and thus the IC package, peripherally leaded devices found themselves unable to keep pace. The packages were getting too large and the lead too long, and both cost and performance were suffering as a result. It was clear that something new on the IC packaging front was going to be required. SO and TSOP packages were still satisfactory for lower I/O, but for higher pin counts the pin grid array (PGA), which had been used primarily for microprocessors, was reinvented to become the ball grid array or BGA, and the BGA has been a huge success in the world of IC packaging. This did not spell the end of the PGA however. The PGA, which IBM had actually employed as the format for the modules used in the IBM 360 computer when it was introduced in the early 1960s, remains a popular format with the pin pitch decreased and the height lowered for socketable devices, primarily microprocessors, but we will see later how it has worked its way into other fewer I/O package applications as well. 

Read the full column online.

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