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Development of Highly Reliable Crack Resistive Build-up Dielectric Material with Low Df Characteristic for Next-Gen 2.5D Packages

Due to the full-scale start-up of 5G communications as well as increase in use of online video sharing services and various teleworking services due to the impact of COVID-19, investments in data centers and high performance servers are accelerating leading to higher data transmission speed requirements in semiconductor device used in high performance computing (HPC). Technological breakthrough not only in silicon technologies but packaging technologies have become more crucial to enable these demands. One such technology, 2.5D packaging utilizing silicon interposers have emerged with increasing number of dies being placed in a single package, thereby making the size of silicon interposers larger. This has also led to advanced organic build-up laminated substrates, commonly used in these devices to connect the die / interposer to the PCBs, becoming ever complex and larger in size, requiring many features such as low insertion loss at high frequency even at elevated temperatures and high humidity conditions. Furthermore, maintaining reliability of these substrates are becoming more challenging as the size of the substrates continue to increase and greater stress is exerted on the substrates. In this paper, we present a newly developed dielectric build-up material; one of the main component of advanced organic build-up substrates, with designs to enable lower insertion loss even at elevated humidity and temperature. Furthermore, flexible segment was introduced into the resin to enable higher fracture toughness in an attempt to enable better reliability of larger substrates. The material design philosophy as well as the data showing the contribution of the flexible component to suppress substrate cracking and thus, enabling higher fracture toughness even at low temperatures, and the result of Thermal Shock Cycle Reliability Test will be presented.