US 11,872,656 B2
Core material, electronic component and method for forming bump electrode
Shigeki Kondoh, Tokyo (JP); Masato Tsuchiya, Tokyo (JP); Hiroki Sudo, Tokyo (JP); Hiroshi Okada, Tokyo (JP); and Daisuke Souma, Tokyo (JP)
Assigned to SENJU METAL INDUSTRY CO., LTD., Tokyo (JP)
Appl. No. 17/610,876
Filed by SENJU METAL INDUSTRY CO., LTD., Tokyo (JP)
PCT Filed Sep. 30, 2020, PCT No. PCT/JP2020/037042
§ 371(c)(1), (2) Date Nov. 12, 2021,
PCT Pub. No. WO2021/079702, PCT Pub. Date Apr. 29, 2021.
Claims priority of application No. 2019-194731 (JP), filed on Oct. 25, 2019.
Prior Publication US 2022/0212294 A1, Jul. 7, 2022
Int. Cl. C22C 13/02 (2006.01); B23K 35/26 (2006.01); B23K 103/08 (2006.01); H05K 3/34 (2006.01)
CPC B23K 35/262 (2013.01) [C22C 13/02 (2013.01); B23K 2103/08 (2018.08); H05K 3/34 (2013.01)] 4 Claims
 
1. A core material comprising:
a core having 0.95 to 1.0 sphericity;
a solder layer made of a (Sn-58Bi)-based solder alloy provided on an outer side of the core; and
a Sn layer provided on an outer side of the solder layer, wherein
when a concentration ratio of Bi contained in the solder layer is a concentration ratio=a measured value of Bi/a target Bi content, the concentration ratio is 91.4% to 108.6%, or
when the concentration ratio of Bi contained in the solder layer is a concentration ratio=an average value of measured values of Bi/a target Bi content, the concentration ratio is 91.4% to 108.6%,
a thickness of the solder layer on one side is 1 μm or more and 100 μm or less,
a thickness of the Sn layer is 0.1 μm to 12 μm on one side,
the thickness of the Sn layer is 0.215% or more and 36% or less of the thickness of the solder layer, and
the core material has a yellowness of 8.5 or less in a L*a*b* table color system, and when ten sample core materials produced in a same production batch as the core material having the yellowness of 8.5 or less are bonded to a substrate by reflow processing, none of the ten sample core materials exhibit a defect at a time of bonding.