Study On Preparation And Dielectric Property Of Polymer Composites Filled With Aluminum Powder

It's known that embedded passives technology is one of key to realize miniaturization, high speed high reliability of PCB-based component. Among PCB passives, the capacitors take up about 60 percent. The dielectric required for embedded capacitors must be of high dielectric constant (K) and low dielectric loss (tgδ). For this purpose, this paper aims to develop a new type of epoxy resin (ER) dielectric filled with diverse passivation aluminum powders of a few microns.The research results show that dielectric constant of composites increases with the addition of aluminum powder, and sees a percolation transition at a fixed loading. At 1000Hz, the threshold value is measured about 36vol%, 28vol% and 13vol% for ER filled with global aluminum powder (Alg), big sheet-like aluminum powder(b-Als)and small sheet-like aluminum powder (Als), respectively. The corresponding loss is found rather low, generally less than 0.1, indicating that the self-passivation film outside prevents the aluminum core from electron's traverse, thus reduces the dielectric loss from electrical conduction. Moreover, dielectric constant of composites increases with test frequency in the range of 102～107Hz, which is attributed to the hysteresis of composite polarization to alternating electric field excited at higher frequency.The comparison experiments show dielectric constants of Alg /ER, b-Als/ER and Als /ER system increase gradually in order, because sheet-like aluminum powder leans to form stronger micro capacitors in insulating ER due to their good one dimensional surface, in comparison with global aluminum powder. Also, the dielectric properties of b-Als/ER were found enhanced by introducing the high-aspect-ratio carbon nanotubes, due to their contributions to the reduction of percolation threshold.In particular, the Als/ER system with a low loading of 22vol% was found excellent dielectric properties asεr=160, tgδ=0.04. This system is a good candidate of low-cost and high performance dielectric for embedded capacitor application in future.