Thermal characterization of a 149-lead VLSI package with heatsink

The steady-state and dynamic thermal characteristics of a 149-lead hermetic PGA (pin-grid array) package are studied, with focus on three different configurations of a stacked-fin heatsink and on two types of fillers for the epoxy heatsink attach adhesive. The package described has high thermal performance in an air-cooled regime. Data are presented showing thermal resistance from junction to ambient as a function of the number of heatsink fins and the composition of the heatsink-attach epoxy. At nominal conditions, thermal resistance from junction to ambient of the selected 5-fin heatsink and aluminium-filled epoxy adhesive is less than 6°C/W at an airflow of 2.5 m/s (500 linear ft/min). Also discussed is the function-to-case thermal resistance, measured per SEMI Standard G30-86. A value of 2.1°C/W was measured for the package