The development of a top-bottom-BGA (TB-BGA)

Abstract

A "top-bottom ball grid array" (TB-BGA) is described which takes advantage of existing BGA and chip scale package (CSP) techniques to create a new package for SCMs, MCMs, sensors and actuators. By using a pin-compatible BGA configuration at the bottom and the top of the carrier, a 3D stack assembly of several TB-BGAs is possible. By considering thermomechanical reliability, the compact stack assembly reduces bending loads and shear forces by using suitable materials. The area configuration of solder balls ensures good thermal conductivity. As demonstration devices, ceramic TB-BGAs are developed as single chip modules (SCMs) and few chip modules (FCMs). They are mounted as intelligent sensor bus interfaces in conventional sensor casings. A fully operational 16 bit processor unit, including microcontroller, SRAM, EEPROM physical CAN bus interface, oscillator and SMD components, requires a volume of only 1.5 cm/sup 3/.