Development of a cost effective high performance metal QFP packaging system

This paper describes the design and development of MQUAD technology. The MQUAD packaging system is a high performance reliable technology currently in use for packaging of microprocessors, high-speed ASIC devices, including CMOS, Bi CMOS, Bi polar, gallium arsenide, and other high performance IC's. The packaging technology is being used for devices dissipating up to 14 watts and switching speed of up to 300 MHz. The design and development was carried out with the objectives of high thermal performance (up to 15 watts), high electrical performance (inductance and capacitances lower than comparable PQFPs) and reliability superior to the PQFPs. The approach taken was; to use an adhesively bonded metal package. An aluminum alloy lid and base were chosen to give excellent heat dissipation ability, mechanical integrity and light weight construction. A special anodization process was developed to put a hard, electrically insulating black colored anodic film on the aluminum alloy components. The adhesive seal is a filled epoxy having low dielectric constant and low ionic content and with excellent adhesion to both copper alloys and aluminum anodic films, especially in moist environments. The leadframe chosen is a high-strength, thermally conductive copper alloy. The assembly process for the MQUAD package emulates the PQFP assembly process except that the molding step is replaced by a single step pad attach simultaneous with the seal adhesive lamination/cure process. The leadframe pad is attached to the anodized aluminum alloy base via a silver-filled epoxy paste. The package was thoroughly tested for reliability and fully characterized for thermal and electrical performance. Reliability tests performed include temperature cycling, thermal shocks, solvent resistance, flammability, pressure cooker, and vapor phase shocks. Reliability of MQUAD packages is superior to that of PQFPs. Characterization includes /spl theta//sub ja/ and /spl theta//sub jc/, and resistance, inductance and capacitance measurements. Thermal and electrical performance of MQUAD packages equal or exceed that of comparable plastic or ceramic QFPs. The high reliability and performance of MQUAD was confirmed by many customers and users and has been published. Because of these benefits, the technology is being further extended to advanced packages such as MCMs, TAB and ball or pad grid arrays.<
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