Determination of internal stress in soldered joints with Sn-based alloys by X-ray diffraction

• Published in: Materials today : proceedings Vol. 45; pp. 4364 - 4366
• Main Authors: Codrean, Cosmin, Buzdugan, Dragoş, Şerban, Viorel-Aurel, Vodă, Mircea
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2021
• Subjects: Compression stress; Nanocrystalline structure; Sn-based alloys; Soldering; Whiskers growths; X-ray diffraction; Whiskers growths; X-ray diffraction; Sn-based alloys; Compression stress; Nanocrystalline structure; Soldering
• ISSN: 2214-7853; 2214-7853
• DOI: 10.1016/j.matpr.2021.02.761

Soldering electronic components with Sn-based alloy may lead to an occurrence of defects of which the most dangerous are the whiskers growths. These whiskers growths are crystalline structures that grow spontaneously in the solder alloy and cause a short circuit in PCBs (Printed Circuit Boards). An important factor that favors the appearance of whiskers growths is the internal stress that occurs in the solder alloy. The higher the state of compression stress is, the higher the risk of growing whiskers. By X-ray diffraction, the internal stresses were calculated in the case of two soldered joints made by the reflow method. The first joint was performed with a commercial solder alloy Sn99Ag0.3Cu0.7, and the second one with the nanocrystalline structured alloy Sn95Cu2Ga3, obtained by the melt-spinning method. It was found that the value of the compression stress determined in the case of soldering with Sn95Cu2Ga3 alloy is about 12 times lower than the value of the compression stress calculated in the case of soldering with Sn99Ag0.3Cu0.7 alloy. In conclusion, a significant grain finishing of the solder alloy reduces the risk of whiskers growths.