铝焊盘镀钯铜丝多焊球脱焊失效的电化学评价

Electrochemical Evaluation of Multi-Ball Desoldering Failure with Palladium-Plated Copper Wire Solder Balls on Aluminum Pads

研究铝焊盘的镀钯铜丝(PCC)焊点的多焊球脱焊(MLB)失效过程,对提高产品的可靠性至关重要。利用电化学方法测定了在不同氯离子浓度、pH值和铜暴露面积等条件下电极的腐蚀电流,以表征铝及其金属间化合物(IMC)的腐蚀速率。结果表明,氯离子可以改变阳极极化率,从而影响腐蚀电流;pH值的变化可以改变阴极极化率,从而影响腐蚀电流。钯作为铜丝的保护层,在镀层分布不均或参数选择不当的条件下,与暴露的铜表面形成腐蚀电偶,导致铝及其IMC成为牺牲阳极并被腐蚀。

Studying the failure process of multi-ball desoldering(MLB)of palladium-plated copper wire(PCC)solder joints on aluminum pads is essential to improve the reliability of products.The corrosion current of the electrode under different chloride ion concentrations,pH values and copper exposure areas is measured by electrochemical method to characterize the corrosion rate of aluminum and its intermetallic compounds(IMCs).The results show that chloride ions can change the anode polarizability and thus affect the corrosion current.A change in pH value can change cathode polarizability,which affects the corrosion current.As the protective layer of copper wire,palladium forms corrosion couples with exposed copper surface under the condition of uneven distribution of plating or improper selection of parameters,resulting in aluminum and its IMCs becoming sacrificial anodes and being corroded.