The Research Of Conductive Graphite Emulsion Used In PCB Microporous

With the development of science and technology, electronic products is more and more miniaturization and multi-functional. This should lead the communicate aperture between the printed circuit board layers to be smaller and smaller. The microporous conductive treatment is an important process of high-end printed circuit board assembly process. Due to convenient and eco-friendly, the graphite emulsion attracted attentions and got developed in recent years in Japan, South Korea, the United States and the European Union and other countries, and gradually replace the traditional chemical plating process, widely used in the manufacture of printed circuit board.In this research, the conductive principle, method and technology of the conductive graphite emulsion were studied. Whereas the technical requirement of the minimum communicate aperture between the printed circuit board layers is less than 1 mm, the graphite emulsion with good film-forming ability and electrical conductivity used in the printed circuit board micro-pore wall was developed, based on the expanded graphite created by the micron graphite.Firstly, the composition of the conductive graphite emulsion and the modification methods of micron graphite were designed, based on the structure and physicochemical properties of graphite. The expandable graphite was prepared by chemical oxidation method using micron graphite, NA-PP-PA-AA as the oxidant and intercalation agent. Through single-factor experiments, the optimum process conditions were determined. The FTIR and SEM results showed that, during the preparation of expandable graphite, the intercalates had already been inserted into the graphite layers. The expanding volume increased six times. The conductive graphite emulsion was mainly composed of the expanded graphite, organic binder, water and auxiliary.Secondly, the expanded graphite, organic binder SP-33 and auxiliary RX-20, were used to develop the graphite emulsion with the characteristics of good film-forming ability and electrical conductivity. The graphite emulsion was used for the film and the electrical conductivity technology research based on the plastic experiment board. The results showed that, the minimal surface resistivity of the graphite emulsion was 2.36Ω2/m2, which was created by 1.00% expanded graphite,5% RX-20 and 6.00% SP-33 at 25℃. The SEM results showed that, dense and uniform conductive coating were formed on the surface of the plastic experiment board. This part of the research laid the foundation for the PCB processing used by the graphite emulsion.Finally, the graphite emulsion was used to deal with single and multilayer PCB, the microporous aperture of the PCB include 0.8mm, lmm and 1.2mm. The results showed that could satisfy the requirement of the PCB board processing technology under the condition of dipping 4 times,15 min and 1 hour drying time each time.