Contact impedance characterization of metallized particle column to copper strip in high frequency domains

Abstract

The number of applications using high frequency bands up 10 GHz is in constant progression in various domains (highspeed communication, portable phone, radar…). This demand has been widely extended to connectors in automotive applications. In fact various connectors have been designed and developped in order to be used over a wide range of frequencies from a few MHz to several GHz. Among these connectors, Metallized Particle Interconnects (MPI) used widely in interconnections (ASICs, PCs, workstations …), constitute an interesting candidate to be developped for high frequency connectors, for frequencies up to 18GHz. In order to simulate the connector, an MPI column was used as a terminal and compressed between two microstrip lines of copper (PCB). Signal losses measurements in the frequency band 100MHz to 18GHz are evaluated as a function of compression force. It was found that the impedance of the system is equivalent to an RCL circuit. By fitting experimental loss data we have analyzed each component and have established the impedance laws. I. INTROCUCTIONMetallized Particle Interconnects (MPI) have been introduced by several manufacturers and been used worldwide in a variety of applications. MPI is a material system designed to address high density socket and connector requirements. Today's microprocessors and ASICs continue to increase in both pin count and density. The MPI product line produces sizes from 24 to 5000+ I/O on 0.5mm and 2.54mm grid spacing. The patented MPI technology provides a highly conductive interconnect. The proprietary material consists of a high temperature polymer compound that has been embedded with metallized particles. The MPI, in general was designed to provide an electrically and mechanically reliable, low cost interconnection method without the use of metal pin or solder techniques [1]. Some investigations have been made on an MPI using a coplanar technique in the range from 0.05GHz to 2.05GHz [2]. The results reveal the existence of a low mutual inductance and capacitance (0.3nH/0.065pF).A lot of work has been done in this area. Ahn et al [3] have introduced an electrical model and determined the high frequency characteristics of a multiple line grid array (MLGA) interposer. Their model was derived on the basis of S parameter measurements and a subsequent microwave network analysis. They have measured different types of MLG interposers with different dielectric insulators and dimensions and they have shown that by reducing the height of the MLGA, the effect of parasitic inductance and capacitance decreases.W. Ryu et al [4] have developed a high frequency SPICE model of anisotropic conductive film Flip chip (ACF) interconnections based on S parameter measurements and a genetic algorithm which is known as a robust optimisation tool. Two different ACF interconnections were studied using an Au-coated polymer ball and a Ni-filled ball. The extracted model of the two ACFs was found to be strongly dependent on not only the size and the rigidity of the conducting balls but also on their...

BGA MPI socket analysis and validation

“…MPI columns can be modeled as a lumped RLC model with good results in [2] for a wide range of frequencies. Fig.…”

“…Current technologies enable designs with high-density MPIs, going from few columns until thousand of columns with a pitch as low as 0.4mm [1]. Jeema et al [2] have studied the effect of the compression force at the MPI columns in the value of capacitance, inductance and resistance of the column. They observed a decreasing (increasing) value of resistance and inductance (capacitance) as the compression force increased.…”

“…They observed a decreasing (increasing) value of resistance and inductance (capacitance) as the compression force increased. Mathematical lumped models of the MPI and similar devices as MLGA have been developed by [2], [3]. In a similar way, Yim et al [4] have been working on microwave model in anisotropic conductive film flip chip interconnections.…”