High Thermal Die-Attach Paste Development for Analog Devices

In recent years, various die attach (DA) materials have been developed to cope with the higher power dissipation requirements of semiconductor devices. DA materials based on metals such as solder or sintered silver (Ag) are used for very high heat generating power devices. While they show outstanding thermal performance, the mechanical properties of these materials are less than ideal. This limits the application window for adoption of these DA materials. Many semiconductor devices such as analog circuits, microcontroller units (MCUs) and application-specific integrated circuits (ASICs) that are widely used in electronic products do not require as much heat dissipation as high-power devices but could benefit from increased thermal capacity and can have larger die sizes. For such products, a DA material with a large amount of Ag powder is added to epoxy resins or acrylic resins to lower the elastic modulus. However, when a polymer is added to the system, the interface resistance increases between the DA material and the die, or between the DA material and the lead frame must be considered. As a result, even if the DA material includes a large amount of Ag, the thermal resistance of the entire package is not improved as expected due to the increase in resistance. To solve this problem, a new DA material concept has been jointly developed that can be applied to a large die size to improve the bulk and interface resistance. This paper will discuss material properties, improved thermal resistance of the package and reliability test results for this material.