US 12,030,139 B2
Sn—Cu mixed alloy solder paste, method of making the same and soldering method
Wallace Chuang, Taipei (TW); Eckart Schellkes, Kirchentellinsfurt (DE); Yee-Wen Yen, Taipei (TW); and Chia-Yu Liu, Taipei (TW)
Assigned to Robert Bosch GmbH, Stuttgart (DE)
Appl. No. 17/602,046
Filed by Robert Bosch GmbH, Stuttgart (DE)
PCT Filed Oct. 30, 2019, PCT No. PCT/EP2019/079580
§ 371(c)(1), (2) Date Oct. 7, 2021,
PCT Pub. No. WO2020/089258, PCT Pub. Date May 7, 2020.
Claims priority of application No. 201811285893.3 (CN), filed on Oct. 31, 2018.
Prior Publication US 2022/0395934 A1, Dec. 15, 2022
Int. Cl. B23K 35/26 (2006.01); B23K 35/02 (2006.01); C22C 12/00 (2006.01); C22C 13/00 (2006.01)
CPC B23K 35/262 (2013.01) [B23K 35/025 (2013.01); C22C 12/00 (2013.01); C22C 13/00 (2013.01)] 14 Claims
OG exemplary drawing
 
8. A soldering method, comprising:
applying a solder paste between a first device with a copper substrate and a second device of a chip element;
heating to melt the applied solder paste using a reflow soldering process to form a soldering seam connecting the copper substrate and the second device, the first device and the second device forming a soldering assembly; and
heating again using said reflow soldering process to solder said soldering assembly with another device,
wherein the solder paste comprises:
a powder and solder flux, and
wherein the powder comprises:
(i) a first solder alloy powder in an amount ranging from 30% to 95% by weight, the first solder alloy powder including a first solder alloy with a solidus temperature of 200° C. to 260° C., the first solder alloy including an Sn—Cu alloy or an Sn—Cu—Ag alloy, and the first solder alloy including by weight, 10%-50% of Cu, and 0%-4% of Ag, with a remainder being Sn, and
(ii) a second solder alloy powder in an amount ranging from 5% to 70% by weight, and the second solder alloy powder including a second solder alloy with a solidus temperature below 250° C.