研究目的
To study the effect of the Ni layer thickness on the morphology and evolution of IMC and the reliability of ENEPIG.
研究成果
Substrates with different surface finish were used to evaluate the microstructure and evolution of IMC in aging process. As for common ENEPIG, the thicker Ni-P can enhance the diffusion inhibition effect sufficiently and there was o brittle IMC growth even after long time aging. For ultrathin ENEPIG, the Ni-P layer was soon consumed completely but the subsequent formation of Ni-Sn-P layer still had a slightly inhibitory effect on the diffusion of Cu. In general, crystalline Ni3P and Ni-Sn-P layers might retard the rapid growth of Cu3Sn IMCs. With the growth of IMC, the shear strength between solder joints and pads was on a downward trend. Properly increasing the thickness of Ni-P layer could reduce the appearance of brittle fracture and effectively enhance the bonding strength.
研究不足
The study did not observe obvious Kirkendall voids in the experiments maybe because of the short aging time. Further drop tests and temperature cycle tests will be conducted and the failure models together with cause will be also presented combined with previous results of IMC evolution.
1：Experimental Design and Method Selection:
Commercial SAC305 solders were reflowed on different thicknesses of Ni (
2：3um and 3um) to study the Cu/Ni IMC evolution while OSP sample was used as a control sample. Aged experiments were conducted at 150°C to evaluate the long term thermal stabilization. After every aging stage, high speed shear test was conducted to estimate the mechanical strength of the IMCs and analysis of fracture morphology. Sample Selection and Data Sources:
Different thicknesses of Ni-P(
3：3um and 3um) were used to study the Cu/Ni IMC evolution and the thickness of Au and Pd was almost 05um and 1um respectively. List of Experimental Equipment and Materials:
SEM(scanning electron microscope), PTR 1101 type bonding strength tester.
4：Experimental Procedures and Operational Workflow:
The samples were aged at 150°C for different time and after every aging stage, high speed shear tests were carried out to study the mechanical strength of the IMCs and analysis of fracture morphology. The microstructures were observed by SEM. Cross section samples were first mounted in epoxy resin, then rubbed by #800, #1200, #2400 and #4000 sandpaper and finally polished by
5：25μm diamond powder. Data Analysis Methods:
Adobe Photoshop was used to select the same layer IMC area according to the different lining image and the thickness T was calculated by the formula T=A/L.
独家科研数据包，助您复现前沿成果，加速创新突破
获取完整内容
