Cupric Chloride-Hydrochloric Acid Microetching Roughening Process for Copper Surfaces in Printed Circuit Board Fabrication
MultiPrep is a cupric chloride-hydrochloric acid based microetchant process developed by MacDermid, Inc. based in Waterbury, CT. MultiPrep provides a unique roughened copper surface, which yields excellent adhesion for both solder mask and dry film photoresist applications. The mechanism of the chemistry is the same as cupric chloride based etchants, whereby copper (Ⅱ) complex reacts with metallic copper (0) to form copper (Ⅰ) complex. The copper (Ⅰ) complex is then oxidized to copper (Ⅱ) complex by oxygen from the air in the presence of hydrochloric acid.Cupric ion is formed continuously in the chemical solution so that microetching characteristics can be kept constant by periodic addition of suitable acids, such as hydrochloric acid. The amount of copper etched using MultiPrep is not as high as that seen in typical cupric chloride etching systems. Oxygen from the air is efficient enough to be used as an oxidizer in the system. Hydrochloric acid maintains the proper hydrogen ion and chloride ion concentration. The cupric ion maintains itself.During the microetching process, the interface of copper crystal structure is etched first in the presence of the additives to form grain structure on copper surfaces. This is the mechanism of obtaining a roughened surface. The microetching rate or amount is predictable from this chemistry. Depending on the dwell time required, the microetching rate (amount) is easily controlled by bath temperature. For example, the micro etching amount is approximately 0.80 μm when bath temperature is maintained at 33 oC with a dwell time of 45 seconds. This cycle is sufficient for inner layer photo resist applications while maintaining proper adhesion and high yields. A higher microetching rate is obtained, such as 1.13 μm, when temperature is at 37 oC. This cycle gives superior roughness to provide excellent adhesion for outer layer solder mask applications.Roughness, Ra (average roughness), indicates that a higher microetching amount provides a higher roughness. Higher temperatures will give a rougher surface even at the same microetching amount. The acidity has little effect on surface roughness, but higher acidity increases microetching rate.After processing copper panels through the microetching solution, the formed copper complex or copper oxide on copper surface needs to be removed with diluted hydrochloric acid (4-6％) solution to get a clean rough surface.
Kesheng Feng Nilesh Kapadia Brian Jobson Steve Castaldi
Electronics Solutions,MacDermid,Inc.227 Freight Street,Waterbury,CT 06410
国际会议
上海
英文
2008-03-17（万方平台首次上网日期，不代表论文的发表时间）