Thermal-mechanical considerations during thermal solution assembly of bare-die packages

Thermomechanical Interaction Between Thin Bare-Die Package and Thermal Solution in Next-Generation Mobile Computing Platforms

“…A prime example of this is very thin, bare-die ball grid array (BGA) MCPs, whose postsurface-mount (SMT) shape increases the challenge of achieving good thermal contact between the package and the thermal solution [10][11][12]. The second effect is that the load and pressure that can be generated between the silicon dice and the thermal solution tends to be limited, due to the reduced stiffness of the thin system components [13]. Figure 1(a) illustrates a representative thermal solution design (also known as, remote heat exchange) [1][2][3][4].…”

“…Correspondingly, the paper is divided into two main sections: Experimental methodology developments: TIMs are tested to characterize their performance at various load conditions using ASTM TIM tester [14]. In parallel, a metrology is developed to measure in situ die warpages of a bare-die package under thermomechanical loading conditions [13]. Finally, a new metrology is developed to measure thermal attach performance as a carefully controlled function of thermal solution load on the SoC package, so that thermal and mechanical data can be collected under identical boundary conditions.…”

“…a) Representative thermal solution design for mobile PC platform and (b) schematic of package and thermal solution shapes post assembly (not to scale)[13] Flowchart of the approach. Experimental metrologies are developed to characterize the underlying thermomechanical interactions.…”

“…Contact properties for TIM model from ASTM TIM tester dataFig. 5(a) Schematic of the loading fixture with a sapphire window that allows optical access to the dice at use conditions and (b) die warpage measurement results of an MCP under thermomechanical loads[13] Schematic showing temperature gradient method to measure h TIM based on ASTM D5470 standard[14] …”