Tin and other alloy melting points
| |
Melting Point |
Composition |
| Sn Pb |
183 oC |
Sn - 37Pb |
| Sn |
232 oC |
|
| Sn Bi |
138 oC |
Sn - 58Bi |
| Sn Ag |
221 oC
221-226 oC |
Sn - 3.5Ag
Sn - 2Ag |
| Sn Ag Cu |
217 oC |
Sn - 3.8Ag - 0.7Cu |
| Sn Cu |
227 oC |
Sn - 0.7Cu |
| Sn In |
118 oC
118-125 oC |
Sn - 52In
Sn - 50In |
| Sn Zn |
198 oC |
Sn - 9Zn |
|
Ref : Lead Free soldering, an Analysis of the Current Status of Lead Free soldering
( BP Richards and associates), January 1999 |
Properties of Sn-Pb and Pb-Free Component Finish Materials
|
Material |
Sn-Pb |
Sn |
Sn-Ag |
Sn-Cu |
| Eutetic Composition |
63Sn-37Pb |
n/a |
96.5Sn/3.5Ag |
99.3Sn/0.7Ag |
| Melting Point |
183 oC |
232 oC |
221 oC |
227 oC |
| Electrical Resistivity |
14.99 ľohm/cm |
11.5 ľohm/cm |
12.31 ľohm/cm |
11.67 ľohm/cm |
| Toxicity |
High |
Low |
Low |
Low |
Ref: Rob Schetly, Shipley Ronal, USA: Pb-free Component
Finishes
Surface Finish for Molded Components
|
Finish |
Manufacturing
Experience |
Concerns |
| Ni-Pd |
Yes |
Material Cost |
| Ni-Pd-Au |
Yes |
Material Cost |
| Sn-Bi |
No |
The assembly must be totally
lead-free |
| Sn-Cu |
Yes |
Tin whiskers |
| Sn |
Yes |
Tin whiskers |
Ref: IPC Roadmap for Lead-Free Electronics Assemblies, 4th Draft June 2000
| Lead-Free Solder Pastes |
- 1997 : NCMS recommended Sn-Bi, Sn-Ag, & Sn-Bi-Ag based on 4 year study
- January 2000 : NEMI (National Electronic Manufacturers Institute) recommend for use by industry as a standardized lead free solder alternative:
- For reflow applications : Sn3.9Ag0.6Cu
- For wave soldering : Sn0.7Cu, or Sn3.5A
Ref:
NEMI Grup- Alloy Selection Team Press Release, Jan 2000
Pb-free Component finishing Seminar, Shipley Ronal, May 2000
|
|
