Reverse engineering techniques of Cu wire bonding process used in manufacturing microelectronic packing components are proposed for evaluating Cu-Al intermetallic phases. The High Thermal Storage (HTS) in the molded bond reliability test and Cu-Al IMC coverage estimation method on Cu ball-bonded parts contribute to increased production efficiency and improved bonding process quality. The results show that distinct intermetallics of microscopic lamellar structures were identified as CuAl2, CuAl and Cu9Al4 after thermal annealing to 2000 h at 150 °C. After post annealing process, voids appear here are too small to pose a threat to reliability concern and Al fragments emerge during bonding process accompanied with smaller diffusion voids are highly connected to create more robust intermetallics. The growth kinetics of Cu-Al intermetallic compound was determined simultaneously during annealing tests. From Arrhenius equation, the growth rate of intermetallic formation (k) has been obtained under three different annealing temperatures and calculated its activation energy of 76.13 kJ/mol and the growth rate constant of k0 = 46.47 μm2/s. The obtained universal equation of layer thickness can be acted as the prediction model for the guideline of intermetallic growth behavior under thermal effect which diminished the Cu-Al interface failures for practical field application. Cu-Al intermetallics coverage inspection and ball shear test was investigated in the unmolded bake reliability test, which addressed the specification of IMC coverage >80% and typical minimum shear strength of 6.67 g/mil2 (= 10.34 Kg/mm2).
All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Computer Science Applications
- Metals and Alloys
- Industrial and Manufacturing Engineering