Xiao Jin, Cheng Wei, Fu-Kang Qu
School of Mechanical and Electrical Engineering, Guangzhou Huali College, Guangzhou, 511300, China.
School of Advanced Manufacturing, Guangdong Songshan Polytechnic College, Shaoguan, 512126, China.
Heliyon. 2024 Feb 28;10(5):e27010. doi: 10.1016/j.heliyon.2024.e27010. eCollection 2024 Mar 15.
High density packaging technology reduces the pad size and the number of grains contained in the pad. When the polycrystalline pad turns into a single crystal pad, the grain orientation has an important impact on the formation of the intermetallic compound (IMC) at the interface. The growth of IMC at the interface between the solder and the single-crystal copper substrate is investigated by selecting the prospective Sn-1.5Ag-2Zn as the solder alloy. Sn-1.5Ag-2.0Zn lead-free solder joints soldered with single crystal (111) copper substrate and polycrystalline red copper substrate are reflowed at 250 °C for 5 min. Samples are subsequently aged at 160 °C. The uneven scallop like CuSn IMC layer grows rapidly when the alloy solder contacts with the copper substrate. The CuSn grain size formed on the surface of single crystal copper is larger than that of polycrystalline copper. Single crystal copper has no grain boundary to block atomic diffusion, which affects grain nucleation and growth. The growth rate of CuSn formed by alloy solder and the single crystal (111) copper solder joint after aging treatment at 160 °C for 20 h is about twice that of the polycrystalline copper solder joint. Then it grows slowly with the increase of aging treatment time. The thick layer CuSn breaks due to crack diffusion after 600 h of aging treatment, and the thickness of IMC remains at 3.5 μm. CuZn generated at the solder and polycrystalline copper solder joint during aging treatment acts as a barrier layer, preventing the solder from contacting the copper substrate and inhibiting the formation of CuSn. CuZn is broken and decomposed after 300 h of aging treatment, and CuSn grows rapidly after the barrier layer disappeared. The thickness of CuSn is about 2.8 μm. The thickness of IMC of solder joint on single crystal copper is 0.7 μm more than that on polycrystalline copper. After aging treatment, the IMC formed at the interface between alloy solder and single crystal copper has better compactness and basically no pores, while there are obvious pores between IMC grains at the interface between alloy solder and polycrystalline copper, which can predict that the soldering quality of the interface between alloy solder and single crystal copper is better. This will provide application prospects for solder joint interface reliability research.
高密度封装技术减小了焊盘尺寸以及焊盘中所含晶粒的数量。当多晶焊盘转变为单晶焊盘时，晶粒取向对界面处金属间化合物（IMC）的形成具有重要影响。通过选择预期的Sn-1.5Ag-2Zn作为焊料合金，研究了焊料与单晶铜基板界面处IMC的生长情况。将用单晶（111）铜基板和多晶紫铜基板焊接的Sn-1.5Ag-2.0Zn无铅焊点在250℃下回流5分钟。随后将样品在160℃下时效处理。当合金焊料与铜基板接触时，不均匀的扇贝状CuSn IMC层迅速生长。单晶铜表面形成的CuSn晶粒尺寸大于多晶铜表面的。单晶铜没有晶界来阻挡原子扩散，这影响了晶粒的形核和生长。合金焊料与单晶（111）铜焊点在160℃时效处理20小时后形成的CuSn生长速率约为多晶铜焊点的两倍。然后随着时效处理时间的增加，其生长缓慢。时效处理600小时后，厚层CuSn因裂纹扩散而破裂，IMC厚度保持在3.5μm。时效处理期间在焊料与多晶铜焊点处生成的CuZn起到阻挡层的作用，可以防止焊料与铜基板接触并抑制CuSn的形成。时效处理300小时后CuZn破裂并分解，阻挡层消失后CuSn迅速生长。CuSn的厚度约为2.8μm。单晶铜上焊点的IMC厚度比多晶铜上的厚0.7μm。时效处理后，合金焊料与单晶铜界面处形成的IMC具有更好的致密性，基本无孔隙，而合金焊料与多晶铜界面处IMC晶粒之间存在明显孔隙，可以预测合金焊料与单晶铜界面处的焊接质量更好。这将为焊点界面可靠性研究提供应用前景。
