Review of RF microsystem packaging process technology

Abstract

The 3-D heterogeneous integration technology of microsystem is the best technical means to achieve higher integration, higher performance and higher working frequency of radio frequency (RF) electronic system. RF microsystem integration technology is categorized into three main types based on the packaging substrate: silicon-based, ceramic-based, and resin-based. In this work, the principle of RF microsystem integration technology is demonstrated in detail, and the process routes and characteristics of different packaging structures are clarified. Moreover, through the multi-dimensional comparison of different packaging structures, the application conditions of specific packaging structures are obtained. According to the comprehensive evaluation, the resin-based embedded chip package shows outstanding potentials in RF performance, integration capability, batch production capability and process cost. However, there are three shortcomings that limit its application in RF microsystems: Firstly, in terms of the universality of RF chips, metal grounding on the back of RF chips cannot be realized by this packaging, and special design of RF chips is required. At present, however, the universal chip with gold back grounding on the market cannot meet the requirements of the packaging process. Secondly, because of the high cost of customized chips, this packaging process is not suitable for small-scale production. Thirdly, the resin-based package does not have the sealing function, thus reliability of the product still needs to be verified. Ceramic-based RF microsystems do not require customized chips and have advantages in chip versatility compared to resin-based systems, with integration capabilities comparable to resin-based systems. However, its batch production capacity is much lower than resin based. In contrast, the silicon-based embedded chip package is as excellent as the resin-based products in chip versatility, RF performance, integration capability, batch production capability, etc., except that the manufacturing cost is high, and the yield should be effectively guaranteed in the manufacturing process. The conclusion provides a guidance for the future research of RF microsystem integration technology.