Search

Increased demand on the mechanical and thermal properties on the thermal interface and die attach material creates a demand for materials with tailored material properties. Solder matrix fiber composites (SMFCs) have been shown to address these challenges, but have, so far, required complicated procedures and components. In this paper, we present the fabrication of a new type of SMFC based on commercially available fiber networks infiltrated with Sn–Ag–Cu alloy (SAC305) or indium using equipment for large-volume production. The composite material exhibits similar thermal properties compared to pure solder, and mechanical properties that can be tailored toward specific applications. We also show that the handling properties of the SMFC allows it to be used in process flows where multiple reflow cycles are required and can achieve a well-defined bond line thickness (BLT) and good bonding using fluxless reflow under pressure. [ABSTRACT FROM AUTHOR]

A reliable thermal interface material (TIM) typically has a low storage modulus ( \textG^\prime ) and a tan( $\delta$ ) less than one; these mechanical properties are crucial for minimizing contact resistance ( \mathbf {R}_{\mathbf {c}} ). This paper demonstrates the correlation between storage modulus ( \textG^\prime ) and the crosslink density of silicone gels. Formulations span between 0.30 and 1.00 hydride to vinyl (H:Vi) ratios for the vinyl terminated and hydride pendent polymers used in the gel. These gels are tailored for TIM applications by adding highly conductive particles to improve thermal conductivity. During this study, when 80 wt% conductive filler was added to gels with a 0.6 H:Vi ratio, the \textG^\prime increased by 6025%. In order to minimize \textG^\prime , the crosslinker in the formulation was replaced with a chain extender. With this formula substitution, the modulus of the filled gel can be successfully lowered to the original value of the unfilled gel while maintaining the crucial properties of a reliable TIM. In effect, it is possible to independently optimize the thermal conductivity of a TIM while creating a compliant gel that maintains surface contact and minimizes contact resistance. [ABSTRACT FROM AUTHOR]

This paper describes and qualifies a partial thermal impedance measurement technique to evaluate the thermal behavior of the physical layers close to the die in power electronic assemblies. The measurement approach is derived from the pulsed heating curve method; nonetheless, the experimental setup proposed here is fitted for a higher sensitivity analysis of die interconnections due to the extraction of the transient thermal impedance at very high current levels and short heating times. Another advantage of this method is that the cooling efficiency of the system has no impact on the sensitivity of the measurements, which makes it particularly suitable for aging monitoring or in-line manufacturing process control. The method is then implemented with power diodes in order to compare the thermal impedance of two power modules with different solder void repartitions. Experimental results and finite-element simulations show that this method has a very good sensitivity and can, therefore, be used to compare the quality of different die attaches without requiring an efficient power module cooling system. [ABSTRACT FROM PUBLISHER]