Electromigration in thin-film solder joints

Crystallographic Orientation Effect on Electromigration in Ni-Sn Microbump

“…Based on the fact that the b-Sn comprises a body-centered tetragonal structure with a highly anisotropic diffusion behavior, the diffusion atoms would be driven rapidly away from the cathode interface as the Sn c-axis grain nearly aligns with the current direction. 18 Therefore, Ni atoms in the Sn grain #1 quickly diffused to the anode interface and reacted with Sn to form Ni 3 Sn 4 , as shown in Fig. 2a.…”

Electromigration in 3D-IC scale Cu/Sn/Cu solder joints

“…4(a) shows the combined result of EBSD image quality (IQ) and orientation map for the area marked with a dotted square in Fig. 2 [9], in which approximately one single grain spanned from the cathode to the anode interface, especially after current stressing of 10 4 A/cm 2 for a few hours (150 C). The Sn grains shown in Fig.…”

“…The second mechanism arose from the Sn self-diffusion as the a-axis was aligned with the electric current, and resulted in a void formation along the cathode interface [8]. Ho et al [9,10] developed a mathematical analysis based on crystallography and Huntington's electromigration theory [17], to quantitatively characterize the dependencies of IMC growth and Cu depletion on the Sn orientation. This study confirmed that the highly anisotropic electromigration behavior of Cu in the Sn lattice would govern the IMC growth and the Cu depletion [9,10,13e16], which could seriously threaten the reliability of thin-film solder joints [9].…”

“…Ho et al [9,10] developed a mathematical analysis based on crystallography and Huntington's electromigration theory [17], to quantitatively characterize the dependencies of IMC growth and Cu depletion on the Sn orientation. This study confirmed that the highly anisotropic electromigration behavior of Cu in the Sn lattice would govern the IMC growth and the Cu depletion [9,10,13e16], which could seriously threaten the reliability of thin-film solder joints [9]. Kang et al [18] reported that the fast electromigration of Cu atoms through GBs of Sn may cause a large number of Cu 6 Sn 5 accumulating in the matrix, especially in the high-angle grain boundaries (HAGBs) (44e95 ).…”

The Dissolution and Supersaturation of Zn in the Sn9Zn Solder Under Current Stressing

“…8,9 The IMC will dissolve and the constituent atoms rapidly diffuse from the cathode side to the anode side through the Sn grain boundaries or grain bulk when the electric current flows in the direction of the c-axis of Sn. 10 Sn9Zn has eutectic temperature of 198°C close to that of the conventional Sn-Pb eutectic alloy. 11,12 The Sn9Zn solder exhibits good mechanical properties.…”