真空汽相焊冷却速率对多层板焊点质量的影响

为解决多层印制板真空汽相焊由于焊后冷却不足导致的焊点纹路问题，本文确定多层板焊点纹路出现的根本原因，对焊后冷却区进行改造，进而研究不同焊接工艺对焊点表面形貌、内部组织形貌及焊点力学性能的影响。实验结果表明，快冷下焊点形成的界面金属化合物（IMC）更薄，焊点组织也更加均匀，即Pb在Sn中的分布更弥散。快冷下形成的IMC层晶粒直径在1μm左右，剪切强度为17.26 MPa，较慢冷提高了43%，达到细晶强化的目的。此外，由于冷却速度过慢导致的焊点表面纹路缺陷也得到明显改善。

Effect of Cooling Rate of Vacuum Vapor Phase Welding on Solder Joint Quality of Multilayer Printed Circuit Board

In order to address the issue of solder joint lines resulted from inadequate post-welding cooling in vacuum vapor phase welding of multi-layer printed boards,this study identified the underlying cause of solder joint lines in multi-layer boards and enhanced the post-welding cooling zone,enabling disclosure of the effects of different welding processes on surface morphology,internal structure morphology, and mechanical properties of solder joints.Experimental findings demonstrated that fast cooling led to thinner interfacial metal compound (IMC) within solder joints and a more uniform distribution of Pb in Sn. The grain diameter of IMC layer formed under fast cooling was approximately 1 µm, while shear strength reached 17.26 MPa-an increase by 43% compared to slow cooling rate - thus achieving fine crystal strengthening objectives. Furthermore, significant improvements have been observed in surface quality by fast cooling reducing solder joint lines.