Low Temperature Alloys

Low temperature alloys, which typically contain indium or bismuth, melt at temperatures less than 180°C. These low-melting alloys are required for a wide variety of applications, including:

1. Step soldering involving temperature sensitive components
2. Soldering to molded interconnect device (MID) plastics
3. Fusible alloys/fuse applications
4. Mercury replacement
5. Thermal and electrical conductivity

Step Soldering Involving Temperature Sensitive Components

Step soldering is the process of attaching components to a substrate in a series of steps where each step in the soldering process uses a lower reflow temperature than the step before it. Standard components are attached first and then temperature sensitive components (like LEDs) are done last. These temperature sensitive components reflow at temperatures less than 180°C.

Soldering To MID Plastics

Molded interconnect device (MID) plastics have been around for many years, but are becoming more popular in product design. MID plastics, which are formed into 3D shapes to increase the functionality and reduce overall weight of each product, are important in automotive and medical applications.

Fusible Alloys/Fuse Applications

Fusible alloys are valued for their relatively low-temperature melting point precision, as well as for their physical properties at room temperature.

Fusible alloys can be used for:

• Fuses
• Tube bending
• Lens blocking
• Wax pattern dies
• Potting molds
• Punch anchoring

Properties

Property	Indalloy
	117	158	160-190	217-440	255	281
Melting Point or Range Deg/F	117	158	160-190	217-440	255	281
Weight lbs/in3	.32	.339	.341	.343	.380	.315
Tensile Strength lbs/in2	5,400	5,990	5,400	13,000	6,400	8,000
Brinell Hardness No.	12	9.2	9	.19	10.2	22
Maximum Load 30 sec lbs/in2	---	10,000	9,000	16,000	8,000	15,000
Safe Load Sustained	---	300	300	300	300	500
Conductivity (Electrical) Compared with Pure Copper	3.34%	4.17%	4.27%	2.57%	1.75%	5.00%
Cumulative Growth and Shrinkage Time after Casting
2 min.	+.0005	+.0025	-.0004	+.0008	-.0008	+.0007
6 min.	+.0002	+.0027	-.0007	+.0014	-.0011	+.0007
30 min.	.0000	+.0045	-.0009	+.0047	-.0010	+.0006
1 hr.	-.0001	+.0051	.0000	+.0048	-.0008	+.0006
2 hr.	-.0002	+.0051	+.0016	+.0048	-.0004	+.0006
5 hr.	-.0002	+.0051	+.0018	+.0049	.0000	+.0005
500 hr.	-.0002	+.0057	+.0025	+.0061	+.0022	+.0005

Mercury Replacement

Indium Corporation manufactures several alloys that have very low-melting points. These liquid-at-room-temperature alloys are finding increased uses in various applications as a replacement for the more toxic mercury. In addition, the vapor pressures of these alloys are substantially lower than mercury.

Thermal and Electrical Conductivity

Alloy systems that are liquid at room temperature have a high degree of thermal conductivity, far superior than ordinary non-metallic liquids. This allows for the use of these materials in specific heat-conducting applications, such as the heat dissipation of sensitive components during operation, machining, and/or manufacturing.

Other advantages of these liquid alloy systems are their inherent high densities and electrical conductivities. Typical applications for these materials include thermostats, switches, barometers, heat transfer systems, and thermal cooling and heating designs.

The table below lists available Indalloy® alloys which are liquid at room temperature.

Indalloy Number	Liquidus C	Solidus C	Composition	Density lb/in3	Specific Gravity gm/cm3	Thermal Conductivity (W/mK)	Electrical Resistivity (10-8 Ω-m)
46L	7.6	6.5	61.0Ga / 25.0In / 13.0Sn / 1.0Zn	0.2348	6.50	15*	33*
51E	10.7	10.7	66.5Ga / 20.5In / 13.0Sn	0.2348	6.50	16.51	28.91
51	16.3	10.7	62.5Ga / 21.5In / 16.0Sn	0.2348	6.50	16.51	28.91
60	15.7	15.7	75.5Ga / 24.5In	0.2294	6.35	20*	29.42
77	25.0	15.7	95Ga/5In	0.2220	6.15	25*	20*
14	29.78	29.78	100Ga	0.2131	5.904	28.13	14.854

Packaging for Liquid Metal Alloys

Liquid metal alloys are shipped in polyethylene bottles.

Storage/Shelf Life for Liquid Metal Alloys

Unopened bottles have a guaranteed shelf life of one year. It is recommended that the volume be replaced with dry argon as the material is removed from the bottle. This will minimize any possibility of oxidation on the surface of the alloy. If the alloy has been stored below its melting point and has solidified, it should be remelted and thoroughly shaken or mixed before use.