Advanced thermal interface materials for enhanced flip chip BGA

Abstract

A family of advanced thermal interface materials for high-power flip-chip BGA (FCBGA) packages is discussed. These silver-filled adhesives provide for high reliability on laminate FCBGA packages. Laser flash thermal testing is utilized to demonstrate that these materials not only have low bulk thermal resistance, but also very low interfacial, or contact resistance. These adhesives have a low modulus and high adhesion, which enables them to flex and remain bonded as the laminate package undergoes stress during temperature cycling. Data also show that this family of TIMs has very low moisture absorption, which contributes to excellent adhesive reliability during HAST (highly accelerated stress test). Reliability data on laminate test packages will be presented. This family of materials has been shown to pass more than 1000 cycles of temperature cycling B (-55 to +125/spl deg/C, liquid-to-liquid) and 200 hours HAST (121/spl deg/C, 100% relative humidity), after JEDEC Level 3 preconditioning and three reflow simulations at 220/spl deg/C on a laminate package with 10/spl times/10 mm die. Total thermal resistance of less than 0.10 cm/sup 2/ K/W has been achieved, at a 25 /spl mu/m bondline thickness.