Interplay of Wettability, Interfacial Reaction and Interfacial Thermal Conductance in Sn-0.7Cu Solder Alloy/Substrate Couples

• Published in: Journal of electronic materials Vol. 49; no. 1; pp. 173 - 187
• Main Authors: Soares, Thiago, Cruz, Clarissa, Silva, Bismarck, Brito, Crystopher, Garcia, Amauri, Spinelli, José Eduardo, Cheung, Noé
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.01.2020; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Copper; Directional solidification; Electronics and Microelectronics; Emerging Interconnection Technology; Heat transfer; Heat transfer coefficients; Instrumentation; Interconnect; Interface reactions; Intermetallic compounds; Low carbon steels; Materials Science; Nickel; Optical and Electronic Materials; Pb-free Solder; Soldering; Solid State Physics; Substrates; Thermal conductivity; Thermal contraction; Tin base alloys; TMS2019 Advanced Microelectronic Packaging; TMS2019 Microelectronic Packaging; Transient heat transfer; Wettability; Wetting; Workpieces; wettability; reaction layer; solders; heat transfer; solidification; Sn-Cu alloy
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-019-07454-6

Directional solidification experiments coupled with mathematical modelling, drop shape analyses and evaluation of the reaction layers were performed for three different types of joints produced with the Sn-0.7 wt.%Cu solder alloy. The association of such findings allowed understanding the mechanisms affecting the heat transfer efficiency between this alloy and substrates of interest. Nickel (Ni) and copper (Cu) were tested since they are considered work piece materials of importance in electronic soldering. Moreover, low carbon steel was tested as a matter of comparison. For each tested case, wetting angles, integrity and nature of the interfaces and transient heat transfer coefficients, ‘ h ’, were determined. Even though the copper has a thermal conductivity greater than nickel, it is demonstrated that the occurrence of voids at the copper interface during alloy soldering may decrease the heat transfer efficiency, i.e., ‘ h ’. Oppositely, a more stable and less defective reaction layer was formed for the alloy/nickel couple. This is due to the suppression of the undesirable thermal contraction since the hexagonal Cu 6 Sn 5 intermetallics is stable at temperatures below 186°C in the presence of nickel.