Studies and Application of Organic Additives on Microvia Filling of Printed Circuit Boards by Copper Electroplating

• Main Authors: Ming-Yao Yen, 顏銘瑤
• Other Authors: 竇維平
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/35731201380567755069

博士 === 國立中興大學 === 化學工程學系所 === 100 === Electrolytic copper microvia filling is an enabling technology, prominently used in today’s manufacture of HDI and IC substrates products for better reliability, designed flexibility and thermal management. In this research, the study of how the chemical and physical factors affect the microvia filling technology is shown as following. First of all, the influence of the molecular weight Mw of polyethylene glycol PEG on the microvia filling by copper electroplating was discussed, and the electrochemical behavior of PEG of different molecule weights in the copper electroplating was studied. Secondly, Microvia filling process was achieved using an accelerator-free acid copper plating solution. The required accelerator (i.e., bis (3-sulfopropyl) disulfide, SPS) for the filling procedure was adsorbed on seed layers in advance. Effect of the seed layers of metallic materials, copper and gold on the microvia filling performance was discussed emphatically. Thirdly, a plating process for microvia filling by Cu electroplating, carried out in a plating bath without an accelerator but with a suppressor only, was proposed in this work. The seed layer of microvia used for subsequent Cu-filling plating is Au formed by electroless plating. Effects of the seed layers of gold on the microvia filling performance and their mechanisms of action were mainly studied. Fourthly, in this work, microvia filling was performed by copper electroplating using two plating formulas with and without a leveler at a low concentration of chloride. Effects of the low concentration of chloride on the microvia filling performance and their electrochemical behavior were was discussed. Fifthly, the mechanism of microvia filling by copper electroplating was investigated by means of a special pattern design of printed circuit board (PCB). These microvias employed in this work had no sidewall copper layer. The outer and the inner copper layers of these microvias were connected together to the cathode during electroplating in order to clarify the mechanism of bottom-up filling. A plating formula that was composed of CuSO4, H2SO4, polyethylene glycol (PEG), bis (3-sulfopropyl) disulfide (SPS), Cl-, and Junas Green B (JGB) was employed as a model formula for studying the filling mechanism. According to this research, we can understand the mechanism of copper deposition due to the additives of carrier, accelerator and Leveler molecules. Moreover, the research provides people with a further consideration. Finally, it is expected that this technology is applicable for control in a practical plating bath.