| 摘要 |
PROBLEM TO BE SOLVED: To relieve the strain due to stress of bumps due to the difference between the thermal expansion coefficients of a semiconductor chip and a circuit wiring board by a method wherein high-melting point solder alloy layers, which are firm to the strain due to stress, are selectively arranged only on the side of the board and the compositions of the alloy layers are changed in a stepwise manner to the side of the chip. SOLUTION: Bump electrodes 3 are respectively constituted of a first solder alloy layer 4 having a first melting point, a third solder alloy layer 5 having a third melting point, which is lower than the first melting point and is higher than a second melting point, and a second solder alloy layer 6 having the second melting point, which are arranged in order from the side of a circuit wiring board 2. Accordingly, as the solder composition alloy layers, which are firm to the strain due to stress, are arranged on the side part, in which the strain due to stress is generated most greatly, of the board 2, the strain due to stress of bumps is relaxed. Moreover, as the melting temperature of the layer 5 is within the ranges of the melting temperatures of the layers 4 and 6, a semiconductor chip 1 can be reliably bonded to the board 2 without needing a flux by heating simultaneously the chip 1 and the board 2 within the ranges of these temperatures to pressure-weld the alloy layers to each other. |
