Enhancing Interlaminar Bond Strength for High Performance Resin Systems andLiquid Photoimageable Soldermasks with an Organo-metallic Copper SurfaceTreatment Process

摘要

The technology shift toward higher performance (low Dk, low Df, faster signal speeds) resin materials for high reliabilityrnhigh layer count multlayer interconnect devices is moving rapidly. PWB fabricators are discovering that the bond strengthrnbetween the copper circuitry and these resin systems is not as reliable with reduced oxide bonding treatments. It has beenrnshown in the market place that reduced oxide processes are being replaced by new process developments for a variety ofrnreasons that will be explained. In addition, increased use of ENIG (electroless nickel-immersion gold) and immersion tinrnprocesses is causing adhesion failures of some liquid photoimageable soldermasks. This paper will explore the mechanism ofrnresin adhesion to copper surfaces and provide a discussion on the interaction of the key process parameters (etch rate, organicrncoating content, sulfuric acid concentration, copper loading in solution) on the process performance. Reduced oxide bondingrntechnology will be the benchmark comparison for the performance of the alternative technology. Bond strengths for a varietyrnof high performance resin systems will be measured. These materials will include high Tg epoxy FR-4, cyanate ester, BT,rnpolyimide, PPE and PPO resins. In addition to measuring bond strengths, other methods including solder float and T-260rntime to delamination will be utilized to compare results. Additional IPC recognized test methods would be employed torncompare the performance and reliability of the organo-metallic process to reduced oxide. The paper will conclude with arndiscussion on improving soldermask adhesion with a modified organo-metallic surface treatment process.