Indium-Containing Preforms
The unique characteristics of indium metal combined with the advantages of making solder into an exact, repeatable shape make preforms made from indium metal the ideal solution for many soldering, thermal, and sealing challenges.
Alloys Containing Indium
| Melting Points | |||
|---|---|---|---|
| Indalloy® Designation | Composition | Liquidus | Solidus |
| Indalloy #1E | 52In/48Sn | 118°C Eutectic | |
| Indalloy #290 | 97In/3Ag | 143°C Eutectic | |
| Indalloy #2 | 80In/15Pb/5Ag | 154°C | 149°C |
| Indalloy #4 | 99.99 Indium | 157°C | |
| Indalloy #9 | 70Sn/18Pb/12In | 167°C | 154°C |
| Indalloy #205 | 60In/40Pb | 181°C | 173°C |
| Indalloy #7 | 50In/50Pb | 210°C | 184°C |
| Indalloy #164 | 92.5Pb/5.0In/2.5Ag | 310°C | 300°C |
For reference, standard SnPb-based solders melt in the 179°C to 183°C range.
For Soldering
- Enables Low Temperature or Step Soldering
Indium metal melts at 157°C, which makes it a fairly low melting temperature metal. Combining indium metal with lead, tin, and/or silver can lower the melting point of the resulting alloy. These alloys can then be used to solder heat sensitive components or in step soldering operations without disturbing previously reflowed solder. - Reduces Gold Leaching
When soldering to gold-plated components (where the gold plating is greater than 15-30µ inches), standard tin-based solders can leach the gold into the joint, which will result in a compromised joint that can fail after several temperature cycles. The use of a solder preform made of an indium-based alloy will inhibit this phenomenon. - Compensates for Different CTEs
Metals with differing coefficients of thermal expansion (CTE) will expand and contract at different rates. Soldering metals with different CTEs can result in a weakened or cracked solder joint. Adding indium metal to the solder preform alloy can help compensate for these different rates. - Improves Thermal Fatigue
Adding even a small amount of indium metal to a solder preform alloy can greatly improve the thermal fatigue performance of the resulting solder joint.
As a Thermal Interface Material
The unique thermal properties of indium-containing preforms and our Heat-Spring® preforms make them the best solution for a variety of thermal challenges. Dissipating the heat generated by smaller, yet more complex packages becomes a challenge for ensuring long-term reliability of a device. Pure indium, with a thermal conductivity of 86W/mK at 85°C together with its malleability, minimizes surface resistance, which increases the flow of heat away from the device, making it an ideal choice as a thermal interface material.
The use of indium-containing preforms, as opposed to other options like thermal grease, creates a clean, repeatable solution that resists pump out.
For Hermetic Seals
One of the most efficient ways of bonding two surfaces together is to use indium-containing solder preforms, wire, or ribbon. Indium metal has a variety of attributes that make this possible:
- Solder preforms made of indium metal can form a hermetic seal between two mating parts.
- Indium metal wets very well to non-metallics such as glass, glazed ceramics, mica quartz, and various metallic oxides. Pure indium metal (Indalloy #4) and 52In/48Sn (Indalloy #1E) exhibit the best wetting for hermetic seals.
- Indium metal remains malleable at cryogenic temperatures.
