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Study of direct soldering of silicon and copper substrate by use of Bi-based solders with lanthanides addition

Roman Kolenak (Faculty of Material Science and Technology, Slovak University of Technology in Bratislava, Trnava, Slovakia)

Soldering & Surface Mount Technology

ISSN: 0954-0911

Article publication date: 5 June 2017




This paper aims to investigate the effect of solder alloying with a small amount of La and Y on bond formation with the Si and Cu substrates.


Bi2La and Bi2Y solders were studied. Soldering was performed using a fluxless method in air and with ultrasonic activation.


It was found that in the process of ultrasonic soldering, the La and Y were distributed at the interface with Si and Cu substrates, which enhanced the bond formation. Addition of La or Y elements in a Bi-based solder also ensured wetting of non-metallic materials such as Si, Al2O3 and SiC ceramics.


The addition of lanthanides offers a method for ensuring wetting of non-metallic materials. The bond with Si was of an adhesive character without the formation of a new contact interlayer. This resulted in lower shear strength of the bond with Si (8-10 MPa). The shear strength of the bond with a Cu substrate was 22-30 MPa.



The paper was prepared with the support of APVV–0023–12: Research of new soldering alloys for fluxless soldering with application of beam technologies and ultrasound and VEGA 1/0089/17 project: Research of new alloys for direct soldering of metallic and ceramic materials. The authors thank Ing. Marián Drienovský, PhD, for DSC analysis, Ing. Martin Sahul, PhD, for EDX analysis, RNDr Petr Harcuba for microscopic analysis and Professor Ing. Maroš Martinkovič, PhD, for providing the methodology for the shear test measurement.


Kolenak, R. (2017), "Study of direct soldering of silicon and copper substrate by use of Bi-based solders with lanthanides addition", Soldering & Surface Mount Technology, Vol. 29 No. 3, pp. 121-132.



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