US 12,138,715 B2
Solder paste
Lei Wang, Hanau (DE); and Sebastian Fritzsche, Hanau (DE)
Assigned to HERAEUS DEUTSCHLAND GMBH & CO. KG, Hanau (DE)
Appl. No. 17/756,875
Filed by Heraeus Deutschland Gmbh & Co. KG, Hanau (DE)
PCT Filed Sep. 4, 2020, PCT No. PCT/EP2020/074721
§ 371(c)(1), (2) Date Jun. 3, 2022,
PCT Pub. No. WO2021/115644, PCT Pub. Date Jun. 17, 2021.
Claims priority of application No. 19214787 (EP), filed on Dec. 10, 2019.
Prior Publication US 2023/0001520 A1, Jan. 5, 2023
Int. Cl. B23K 35/36 (2006.01); B23K 1/00 (2006.01); B23K 35/02 (2006.01); B23K 35/26 (2006.01); B23K 35/365 (2006.01); C22C 13/00 (2006.01); B23K 101/36 (2006.01)
CPC B23K 35/3618 (2013.01) [B23K 1/0016 (2013.01); B23K 35/025 (2013.01); B23K 35/262 (2013.01); B23K 35/365 (2013.01); C22C 13/00 (2013.01); B23K 2101/36 (2018.08)] 20 Claims
 
1. A solder paste consisting of 85 to 92% by weight of a tin-based solder and 8 to 15% by weight of a flux, wherein the flux comprises:
i) 30 to 50% by weight, based on the total weight of the flux, of a combination of at least two modified or unmodified colophony resins;
ii) 5 to 20% by weight, based on the total weight of the flux, of at least one low-molecular carboxylic acid; and
iii) 0.4 to 10% by weight, based on the total weight of the flux, of at least one amine, wherein
at least one of the at least two colophony resins has an Mw in the range of 150 to 550 and an acid number in the range of 180 to 280 mg KOH/g,
at least one of the at least two colophony resins has an Mw in the range of >550 to 10,000 and an acid number in the range of 1 to 50 mg KOH/g, and
the combination of the colophony resins has an integral molecular weight distribution of 45 to 70% by area in the molecular weight range of 150 to 550 and of 30 to 55% by area in the molecular weight range of >550 to 10,000 in a combined gel permeation chromatogram (GPC).