Solder alloy, solder ball, solder paste, and solder joint

Patent metadata

Field	Value
Publication number	US-12109653-B2
Application number	US-202318224833-A
Country	US
Kind code	B2
Filing date	Jul 21, 2023
Priority date	Jul 22, 2022
Publication date	Oct 8, 2024
Grant date	Oct 8, 2024

Abstract

Provided are a solder, a solder alloy, a solder ball, a solder paste, and a solder joint, which have a low melting point, high hardness in a high-temperature environment, heat cycle resistance, and electromigration resistance. The solder alloy has an alloy composition that includes by mass %, Bi: 30 to 60%, Ag: 0.7 to 2.0%, Cu: more than 0% and 1.00% or less, Ni: 0.01 to 1.00%, Sb: 0.2 to 1.5%, with the balance being Sn.

First claim

The invention claimed is:

1. A solder alloy having an alloy composition consisting of, by mass %,
Bi: 30 to 60%,
Ag: 0.7 to 2.0%,
Cu: more than 0% and 1.00% or less,
Ni: 0.01 to 1.00%,
Sb: 0.2 to 1.5%, with the balance being Sn,
wherein the solder alloy exhibits the following properties:
a melting rate in which 99.9% has melted before reaching 200° C., wherein the melting rate is judged based on an area ratio of a DSC curve and is a value obtained by dividing reaction calories necessary for complete melting by reaction calories completed before reaching 200° C., and multiplying the result of dividing by 100;
an average surface hardness of 7.0 Hv or more, wherein the average surface hardness is determined by measuring surface hardness of 5 bumps that are subjected to a load of 1.96N for 60 seconds at 110° C.;
an average number of heat cycles until rupture of at least 3,000, wherein the heat cycles include a low temperature of −40° C., a high temperature of +100° C., and a holding time of 10 minutes, wherein determining the average number of cycles until rupture includes subjecting test substrates to the heat cycles, monitoring resistance values using a daisy chain circuit, and judging that rupture has occurred when a resistance value increase of over 200% is reached from the start of the test, wherein the test substrates are prepared by placing solder balls with a diameter of 0.24 mm on electrodes of a substrate on which a soldering flux comprising a solvent, an activator, a thixotropic agent, and an organic acid was applied, mounting BGA components, and performing reflow soldering under conditions of a maximum temperature of 190° C. and a holding time of 90 seconds; and
an electromigration resistance in which at least 300 hours elapses until the electrical resistance increases by 150% compared with an initial electrical resistance value, wherein the electrical resistance is determined by connecting a test substrate to a variable switching power supply and applying a current in a silicon oil bath held at 110° C. and continuously measuring the electrical resistance, wherein the test substrate is prepared by fabricating a package using solder balls with a diameter of 0.24 mm made of the solder alloy by performing reflow soldering on a package substrate with a size of 12 mm×12 mm including Cu electrodes with a diameter of 0.24 mm by using a water-soluble flux, printing solder paste on a glass epoxy substrate with a size of 29 mm×19 mm and a thickness of 0.8 mm, and mounting the fabricated package to the glass epoxy substrate using reflow soldering under conditions of a maximum temperature of 190° C. and a holding time of 90 seconds to fabricate the test substrate.

2. A solder alloy having an alloy composition consisting of, by mass %,
Bi: 30 to 60%,
Ag: 0.7 to 2.0%,
Cu: more than 0% and 1.00% or less,
Ni: 0.01 to 1.00%,
Sb: 0.2 to 1.5%, and
at least one selected from the group consisting of,
at least one of P, Ge, Ga, and As: 0.1% or less in total,
at least one of Fe and Co: 0.1% or less in total,
Pd: 0.1% or less,
Zr: 0.1% or less,
Zn: 0.1% or less, and
Pb: 0.02% or less,

with the balance being Sn,
wherein the solder alloy exhibits the following properties:
a melting rate in which 99.9% has melted before reaching 200° C., wherein the melting rate is judged based on an area ratio of a DSC curve and is a value obtained by dividing reaction calories necessary for complete melting by reaction calories completed before reaching 200° C., and multiplying the result of dividing by 100;
an average surface hardness of 7.0 Hv or more, wherein the average surface hardness is determined by measuring surface hardness of 5 bumps that are subjected to a load of 1.96N for 60 seconds at 110° C.;
an average number of heat cycles until rupture of at least 3,000, wherein the heat cycles include a low temperature of −40° C., a high temperature of +100° C., and a holding time of 10 minutes, wherein determining the average number of cycles until rupture includes subjecting test substrates to the heat cycles, monitoring resistance values using a daisy chain circuit, and judging that rupture has occurred when a resistance value increase of over 200% is reached from the start of the test, wherein the test substrates are prepared by placing solder balls with a diameter of 0.24 mm on electrodes of a substrate on which a soldering flux comprising a solvent, an activator, a thixotropic agent, and an organic acid was applied, mounting BGA components, and performing reflow soldering under conditions of a maximum temperature of 190° C. and a holding time of 90 seconds; and
an electromigration resistance in which at least 300 hours elapses until the electrical resistance increases by 150% compared with an initial electrical resistance value, wherein the electrical resistance is determined by connecting a test substrate to a variable switching power supply and applying a current in a silicon oil bath held at 110° C. and continuously measuring the electrical resistance, wherein the test substrate is prepared by fabricating a package using solder balls with a diameter of 0.24 mm made of the solder alloy by performing reflow soldering on a package substrate with a size of 12 mm×12 mm including Cu electrodes with a diameter of 0.24 mm by using a water-soluble flux, printing solder paste on a glass epoxy substrate with a size of 29 mm×19 mm and a thickness of 0.8 mm, and mounting the fabricated package to the glass epoxy substrate using reflow soldering under conditions of a maximum temperature of 190° C. and a holding time of 90 seconds to fabricate the test substrate.

3. A solder alloy having an alloy composition consisting of, by mass %,
Bi: 30 to 60%,
Ag: 0.7 to 2.0%,
Cu: more than 0% and 1.00% or less,
Ni: 0.01 to 1.00%,
Sb: 0.2 to 1.5%, and
at least one selected from the group consisting of,
P: less than 0.01%,
Ge: 0.01% or less,
Ga: less than 0.01%,
As: more than 0.001% and 0.01% or less,
Co: less than 0.01%,
Pd: 0.01% or less, and
Pb: less than 0.004%,

with the balance being Sn,
wherein the solder alloy exhibits the following properties:
a melting rate in which 99.9% has melted before reaching 200° C., wherein the melting rate is judged based on an area ratio of a DSC curve and is a value obtained by dividing reaction calories necessary for complete melting by reaction calories completed before reaching 200° C., and multiplying the result of dividing by 100;
an average surface hardness of 7.0 Hv or more, wherein the average surface hardness is determined by measuring surface hardness of 5 bumps that are subjected to a load of 1.96N for 60 seconds at 110° C.;
an average number of heat cycles until rupture of at least 3,000, wherein the heat cycles include a low temperature of −40° C., a high temperature of +100° C., and a holding time of 10 minutes, wherein determining the average number of cycles until rupture includes subjecting test substrates to the heat cycles, monitoring resistance values using a daisy chain circuit, and judging that rupture has occurred when a resistance value increase of over 200% is reached from the start of the test, wherein the test substrates are prepared by placing solder balls with a diameter of 0.24 mm on electrodes of a substrate on which a soldering flux comprising a solvent, an activator, a thixotropic agent, and an organic acid was applied, mounting BGA components, and performing reflow soldering under conditions of a maximum temperature of 190° C. and a holding time of 90 seconds; and
an electromigration resistance in which at least 300 hours elapses until the electrical resistance increases by 150% compared with an initial electrical resistance value, wherein the electrical resistance is determined by connecting a test substrate to a variable switching power supply and applying a current in a silic

Assignees

• Senju Metal Industry Co

Inventors

• MATSUFUJI Takahiro
• Yoshikawa Shunsaku
• Sudo Hiroki

Classifications

• C22C13/02

  with antimony or bismuth as the next major constituent · CPC title

• B23K35/025

  Pastes, creams or slurries · CPC title

• B23K35/0244

  Powders, particles or spheres; Preforms made therefrom · CPC title

• B23K3/0623

  for shaped solder piece feeding, e.g. preforms, bumps, balls, pellets, droplets · CPC title

• B23K35/0222

  for use in soldering or brazing (B23K35/0205 takes precedence) · CPC title