To suppress thermomigration of Cu–Sn intermetallic compounds in flip-chip solder joints

• DOI: 10.1016/j.jmrt.2023.05.084
• Publication Date: 2023-05-11T02:31:01Z
• Authors: Yan-Rong Huang; Dinh-Phuc Tran; Po-Ning Hsu; Shih-Chi Yang; A.M. Gusak; K.N. Tu; Chih Chen
• Keywords: Isothermal process; Temperature Gradient

We report here an approach to inhibit Cu–Sn intermetallic compounds (IMCs) in flip chip solder joints under thermal-gradient annealing. reflowed two types of solders joints, Cu/SnAg/Cu and Cu/SnAg/Ni, oven (isothermal) on a hot plate (with thermal-gradient) at 260 °C. During the isothermal reflow, IMC growth rates top bottom sides joint were ∼4.0 × 10−2 8.9 μm/min, respectively. However, rate increased 7.8 10−1, 7.9 10−1 μm/min cold ends with low, medium, high thermal gradients, Yet, thickness remained almost unchanged. These results indicate that gradient has facilitated formation ends. But, when Ni film was sandwiched end, end reduced ∼9.7 10−2, 1.4 1.5 respectively, indicating thermomigration IMCs retarded by Ni. It is speculated layer transformed into stable (Cu,Ni)6Sn5 ternary IMCs, thus Cu suppressed. A kinetic model also proposed address competitive reactions Cu-molten joints.