I. Introduction
With the rapid development of high frequency and high speed chip technology, there is an urgent need for high frequency, high speed and broadband package [1] [2]. Ball grid array (BGA) package is widely used for RF microwave and high-speed ICs because of its small size, many pins and excellent signal integrity. The input signal is transmitted through the ball-grid structure to the "quasi-coaxial" interconnection structure of the ceramic substrate, and then connected to the chip through the horizontal transmission line of the dielectric surface. The key "quasi-coaxial" interconnection structure adopts vertical interconnection structure, with bandwidth up to DC~30 GHz [3] [4]. In the frequency band above millimeter wave, there is a sudden change in impedance at the corner of the traditional BGA vertical interconnection structure, causing discontinuity in characteristic impedance, resulting in worse signal insertion loss and return loss, thereby affecting signal transmission. In this paper, based on the "quasi-coaxial" interconnection structure, a novel non-vertical structure is proposed. Through the dislocation design of the metallized through hole between the ceramic dielectric layer, the impedance mutation of the vertical through hole and the horizontal transmission line bend is improved. Finally, the DC~55 GHz low loss interconnection structure is designed and implemented, which can meet the high speed digital and broadband RF circuit applications.