Interfacial Reactions and Compound Formation in the Edge of PbSn Flip-Chip Solder Bumps on Ni/Cu Under-Bump Metallization

Authors: Huang, Chien-Sheng; Jang, Guh-Yaw; Duh, Jenq-Gong

Source: Journal of Electronic Materials, Volume 32, Number 11, 1 November 2003 , pp. 1273-1277(5)

Publisher: Springer

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Abstract:

Flip-chip technology with the layout of ball grid array has been widely used in today's microelectronics industry. The elemental distribution in the edge of the solder bump is crucial for its correlation with the bump strength. In this study, Ni/Cu under-bump metallization (UBM) was used to evaluate the intermetallic compound (IMC) formation in the edge of the solder bump between the UBM and eutectic Sn-Pb solder in the 63Sn-37Pb/Ni/Cu/Ti/Si₃N₄/Si multilayer structure. During reflows, layered-type (Ni_1-xCu_x)₃Sn₄ and island-like (Cu_1-yNi_y)₆Sn₅ IMCs formed in the interface between the solder and UBM, while only the (Cu_1-yNi_y)₆Sn₅ IMC was observed in the sideway of the Ni/Cu UBM. After high-temperature storage (HTS) at 150°C for 1,000 h, both (Cu_1-yNi_y)₆Sn₅ and (Cu_1-zNi_z)₃Sn were found in the sideway of the Ni/Cu UBM. Two other IMCs, (Ni_1-xCu_x)₃Sn₄ and (Cu_1-yNi_y)₆Sn₅, formed in the interface between the solder and UBM. The growth of the (Cu_1-yNi_y)₆Sn₅ IMC was relatively fast during HTS.

Keywords: FLIP CHIP; REFLOW; HIGH-TEMPERATURE STORAGE; UNDER-BUMP; METALLIZATION; INTERMETALLIC COMPOUND

Document Type: Research article

Publication date: 2003-11-01