Anti-tombstoning solder alloys for surface mount applications
US6783057B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 20, 2001 |
| Grant date | Aug 31, 2004 |
| Priority date | — |
| Expiry date | Jan 27, 2022 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05K3/3463
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
The object of this invention is to employ a solder alloy comprising tin/lead/silver in order to provide a wider solidification range and achieve balance between the surface tensions of both side of a small leadless component. The expanded solidification range slows the melting and wetting time so as to balance the surface tension of the molten solder, and in turn reduces the tombstoning frequency. The preferred Ag concentration is 0.2-0.5% in weight, the more preferred Ag concentration is 0.3-0.4% in weight. For reflow soldering of small leadless components, the pastes made with the alloy compositions of Sn62.6Pb37Ag0.4 and Sn63Pb36.6Ag0.4 results in improvements in tombstoning.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.