Liquid Metal Paste Jetting for High-Performance Computing Applications in Electronics Assembly

ABSTRACT Metals have long been used as thermal interface materials (TIMs). Due to their high reliability and thermal conductivity, metal TIMs are excellent solutions for heat dissipation in electronic systems, especially for more challenging applications. Thermal conductivity and interfacial resistance are the most important properties of TIM. One of the biggest obstacles for using metal TIMs is interfacial resistance. Most metal TIMs are quite stiff and require compressive force to maintain necessary contact with active components to lower the interfacial resistance. With devices becoming smaller, consuming more power, and producing more heat, finding the right TIM becomes a highly critical step in any electronic systems application. Recently, liquid metal TIMs have gained popularity, especially for thermal management of high-performance computing semiconductor applications such as in central processing units (CPUs), graphics processing units (GPUs), and multi-chip modules (MCMs). Due to their fluid nature, liquid metal TIMs do not need to be compressed to maintain even contact, and they can accommodate imperfections in the neighboring components. The newest metal TIMs are made of liquid metal paste (LMP). These gallium-based, high viscosity materials maintain all the good properties of liquid metals but also offer some improved mechanical properties. A key challenge lies in applying LMPs consistently through various dispensing techniques which could be traditional, like time-pressure versus advanced jetting technology. Both dispensing techniques will be compared based on dispensing quality, weight repeatability on substrates, and valve-hardware stability. This paper addresses the challenges faced during LMP dispensing in high-volume manufacturing, and how to maintain constant volume over the product with good dispense quality leading to higher throughput and process reliability.