Lead-free solder paste
US9185812B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | May 24, 2006 |
| Grant date | Nov 10, 2015 |
| Priority date | — |
| Expiry date | Oct 9, 2031 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05K2201/0257
- WIPO fieldMachine tools
- WIPO sectorMechanical engineering
Abstract
In a conventional Sn—Zn based lead-free solder, Zn crystallized to a large size of several tens of micrometers, and it was difficult to suppress the formation of coarse crystallizates and to increase the bonding strength without changing the soldering temperature. There were alloys which improved strength by the addition of a minute amount of a Group 1B metal, but the alloys had an increased melting temperature so that reflow could not be performed with the same temperature profile as for Sn—Pb, so the alloys had advantages and disadvantages.By using a solder paste formed by mixing an ethanol solution containing nanoparticles having a particle diameter of 5-300 nm and containing at least one of Ag, Au, and Cu with a flux and solder powder for an Sn—Zn based lead-free solder paste, the formation of an alloy of Au, Au, or Cu with Zn occurs during soldering, thereby forming fine clusters in the resulting liquid phase of molten solder, and a fine solder structure is obtained following melting.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.