|
||
|
||
|
||
|
||
|
Properties of Lead-Free Solders (Cont.)
3. Candidate Alloys for Replacing Lead-Alloy Solders
| Table 3.1. Criteria for Down-Selection of Alloys |
| Property | Definition | Minimum Acceptance Level |
| Liquidus temperature | Temperature at which solder alloy is completely molten | |
| Pasty Range | Range of temperature between solidus and liquidus, where alloy is part solid and part liquid. | < 30 (ºC) |
| Wettability | Assessed by force required to wet a copper wire with molten solder. A large force indicates good wetting, as does short duration t0 at zero wetting force and time t2/3 to reach two thirds of maximum wetting force. | Fmax > 300 uN t0 < 0.6 s t2/3 < 1 s |
| Area of Coverage | Measures coverage of copper test piece by solder | > 85 % |
| Drossing | Measured by amount of oxide formed in air on surface of molten solder after a fix duration at soldering temperature | Qualitative |
| TMF | Lifetime at a given failure rate compared to that of (eutectic) Sn/37Pb, for a specific configuration of board and solder joint | > 75 % |
| Thermal Mismatch | Difference in coefficients of thermal expansion that causes unacceptable thermal stress | < 29 ppm/ºC |
| Creep | Stress load to failure at room temperature, in 10,000 minutes (~167 hours) | > 500 psi |
| Yield Strength | >2000 psi | |
| Elongation | Relative elongation of material under uniaxial tension at room temperature | > 10 % |
Source: Technical Reports for Lead Free Solder Project: Properties Reports: "Down Selection;" on Lead Free Solder Project CD-ROM, National Center for Manufacturing Sciences (NCMS), 1998
Back to Properties of Lead-Free
Solders Back to main page
| Table 3.2. Chemical compositions of 79 lead-free solder alloys down-selected for preliminary testing by the National Center for Manufacturing Sciences (NCM). |
| The seven lead-free alloys in bold type are those down-selected for extensive testing and measurement from the initial pool of 79. Selection process is detailed in Technical Reports for the Lead Free Solder Project: Properties Reports: "Down Selection," on Lead Free Solder Project CD-ROM, National Center for Manufacturing Sciences. |
| NCMS Alloy Code |
Chemical Composition (% by wt.) |
NCMS Alloy Code |
Chemical Composition (% by wt.) |
NCMS Alloy Code |
Chemical Composition (% by wt.) |
||
| A1* | Sn-37Pb | D8 | Sn-3Ag-55Bi-2Sb | F5 | Sn-20In-2.8Zn | ||
| A2 | Sn-2Ag-36Pb | D9 | Sn-3Ag-54Bi-2In-2Sb | F6 | Sn-5Bi-7Zn | ||
| A3 | Sn-97Pb | D10 | Sn-3Ag-54Bi-2Cu-2Sb | F7 | Sn-31.5Bi-3Zn | ||
| A4* | Sn-3.5Ag | F8 | Sn-3.5Ag-1.5In | ||||
| A5 | Sn-5Sb | E1 | Sn-3Ag-2Sb | F9 | Sn-2Ag-7.5Bi-0.5Cu | ||
| A6* | Sn-58Bi | E2 | Sn-3Ag-2Cu-2Sb | F10 | Sn-0.2Ag-2Cu-0.8Sb | ||
| A7 | Sn-3.5Ag-0.5Sb-1Cd | E3 | Sn-3Ag-2Bi-2Sb | ||||
| A8 | Sn-75Pb | E4 | Sn-3Ag-2Bi | F11 | Sn-2.5Ag-19.5Bi | ||
| E5 | Sn-2.5Ag-2Bi | F12 | Sn-3Ag-41Bi | ||||
| B1 | Sn-50Bi | E6 | Sn-2Bi-1.5Cu-3Sb | F13 | Sn-55Bi-2Cu | ||
| B2 | Sn-52Bi | E7 | Sn-2Bi-8In | F14 | Sn-48Bi-2Cu | ||
| B3 | Sn-55Bi-3Cu | E8 | Sn-10Bi-10In | F15 | Sn-57Bi | ||
| B4 | Sn-48Bi-4Cu | E9 | Sn-10Bi-20In | F16 | Sn-56.7Bi-0.3Cu-1In | ||
| B5 | Sn-2Ag-46Bi-4Cu | E10 | Sn-9Zn | F17 | Sn-3.4Ag-4.8Bi | ||
| B6 | Sn-56Bi-2In | F18 | Sn-3Ag-15In | ||||
| EN1 | Sn-5Ag-8.6In | F19 | Sn-3Ag-5Bi-10In | ||||
| C1 | Sn-2Ag-1.5Sb-29Pb | EN2 | Sn-5.6Ag-14.4In | F20 | Sn-5Bi-10In | ||
| C2 | Sn-3Ag-4Cu | EN3 | Sn-6.8Ag-20In | ||||
| C3 | Sn-2.5Ag-2Bi-1.5Sb | EN4 | Sn-3.1Ag-6.1Bi | F21 | Sn-2.8Ag-20In | ||
| C4 | Sn-3Ag-1Bi-1Cu-1.5Sb | EN5 | Sn-3.5Ag-10Bi | F22 | Sn-0.1Ag-1Bi-3.9Sb | ||
| C5 | Sn-2Ag-9.8Bi-9.8In | EN6 | Sn-3.3Ag-15Bi | F23 | Sn-0.5Ag-1.5Bi-3Sb | ||
| EN7 | Sn-6.8Ag-30Bi | F24 | Sn-55Bi-2Zn | ||||
| D1 | Sn-45Bi | EN8 | Sn-3.3Ag-11.2Bi-5.5In | F25 | Sn-0.5Ag-56Bi | ||
| D2 | Sn-57Bi-2In | EN9 | Sn-2.5Ag-11.2Bi-5.5In | F26 | Sn-4.5Ag-1.6Cu-5Sb | ||
| D3 | Sn-2Ag-57Bi | F27 | Sn-3.5Ag-0.5Cu-1Zn | ||||
| D4 | Sn-57Bi-2Sb | F1 | Sn-2Ag-7.5Bi-0.5Cu | F28 | Sn-3Ag-10.9In-0.4Sb | ||
| D5 | Sn-57Bi-1Sb | F2# | Sn-2.6Ag-0.8Cu-0.5Sb | F29 | Sn-4.7Ag-1.7Cu | ||
| D6 | Sn-2Ag-56Bi-1.5Sb | F3 | Sn-0.5Ag-4Cu | F30 | Sn-3.2Ag-0.7Cu | ||
| D7 | Sn-3Ag-55.5Bi-1.5Sb | F4 | Sn-8.8In-7.6Zn | F31 | Sn-3.5Ag-1.3Cu |
*Eutectic composition
#Composition F2 is a proprietary composition, Castin®
Back to top (Part 3)
Back to Properties of Lead-Free Solders
|
| NIST home | Boulder
Labs | NIST & you | Programs Guide to NIST | General Info | Staff | Events | Publications | Search | News |
National Institute of Standards
& Technology
325 Broadway, Boulder, CO 80303. Phone: (303)497-3523
---------------------------------
Comments and suggestions e-mail to: webmaster
This page was last updated on: 2002 February 11 8:30:50 pm
