Pre-curing investigation of filling conductive paste in prepreg to interconnect two multilayer structures of backboard for press-fit application

Abstract

Purpose The purpose of this paper is to form high density interconnection (HDI) of backboard for press-fit applications with the pre-curing conditions of conductive paste. The best condition of pre-curing conductive paste should be found to obtain good electrical and physical performance of the conductive paste and avoid the simultaneous curing behavior of prepreg. Design/methodology/approach A novel structure of backboard was designed by using the connection of conductive paste-filled through holes to connect two multilayers. Pre-curing conditions of conductive paste were investigated to find their effects on resistance, bond strength and volume shrinkage. The reliability of pre-curing conductive paste was also analyzed. Findings Pre-curing conditions led to a great influence on the resistance, bond strength and volume shrinkage of the conductive paste. The best condition of pre-curing conductive paste was chosen as the low curing temperature of 60°C and a curing time of 30 min. Cured conductive paste exhibited square resistance of 4.205 mΩ/□ and bonding strength of 22.86 N. The as-obtained pre-curing condition could improve the reliability of conductive paste. Pre-curing process of conductive paste at extremely low temperature to interconnect two multilayer structures improved the density interconnection of backboard for press-fit applications. Originality/value The use of HDI of backboard could lead to good assembly for high-speed signal transmission of electronic products with press-fitting components. The connection of pre-curing conductive paste for multilayers could have important function for improving the application for communication backboard.