HIGH-PERFORMANCE CAVITY-DOWN METAL-BASED BALL GRID ARRAY (MEBGA) PACKAGE

The recent trend in microprocessor technology is for high-speed device s 200 similar to 500 MHz) on which a large number of drivers simultane ously switch on/off. On the other hand, the trend in high-performance ASIC devices is also far higher on-and off-chip devices speed: higher chip I/O density and larger power. Our newly developed high-performanc e Cavity-Down (C/D) Metal Based Ball Grid Array (MeBGA) package is con structed of a unique three-layer substrate, which is composed of a cop per foil and copper alloy substrate which are insulated with polyimide . The MeBGA has two unique and important structures, which are termina l and ground bonding area. As a result, MeBGA realizes higher thermal performance, higher electrical performance and lower cost than those o f conventional Plastic BGA (PBGA). For example, thermal resistance is 40% lower than that of conventional PBGA package at 1.0 m/s air veloci ty. Electrical analysis is presented to show that the simultaneous swi tching noise including the ground bounce noise and power supply noise is about 40% lower than that of conventional PBGA. The terminal is fab ricated on the rear side of MeBGA for currently testing interconnectio n between solder balls and the Printed Wiring Board (PWB), and also re ducing the thermal expansion stress between solder ball and copper foi l. The ground bonding ar ea has a flat area fabricated around the slop e of die cavity for direct wire bonding to the copper substrate, Both terminal and ground bonding areas are provided with a much simpler pro cess. This paper describes MeBGA's structure, assembly process, some c haracteristics, and the results of a reliability test.