Low-Temperature Soldering

Low-Temperature Soldering

Indium Corporation makes a wide range of alloys that melt or reflow below 180°C and can be used to solve a great many assembly and other challenges.

Features & Benefits

Low-temperature solder is often used in electronics assembly including for these applications:
  • Attachment of temperature sensitive components to printed circuit boards
  • Step soldering, when a secondary, lower temperature reflow process is required after a standard SAC soldering process is completed
  • Eliminating warpage of thinner chips due to high temperature reflow
  • Low melting or low-Tg flex circuitry which are used in cellphones, smartwatches, and many internet-of-things (IoT) devices
  • Large area array devices, such as BGAs, to avoid head-in-pillow (HIP) and non-wet-open (NWO) failures
Low-Temperature Soldering

DuraFuseLT

Indium Corporation has invented a new low temperature solder paste called DuraFuseLT. This new low temperature alloy uses a mixed powder system (a low-temperature alloy powder mixed with a typical SAC alloy powder) to achieve higher drop shock and thermal cycling performance as compared to the typical BiSnAg alloys currently on the market.

Older legacy low temp options are brittle and tend to crack when stressed, which make it unsuitable for many applications. DuraFuseLT is more robust and increases durability in drop shock not just incrementally, but by a significant measure. In fact, under the right process conditions, DuraFuse LT’s performance is comparable to SAC305.

Other low temperature alloys include:
Indalloy # Liquidus
(°C)
Solidus
(°C)
Element
1
% Element
2
% Element
3
% Element
4
%
1E 118 118 In 52.0 Sn 48.0        
1 125 118 In 50.0 Sn 50.0        
71 131 118 Sn 52.0 In 48.0        
281 138 138 Bi 58.0 Sn 42.0        
282 140 139 Bi 57.0 Sn 42.0 Ag 1.0    
290 143 143 In 97.0 Ag 3.0        
87 145 118 Sn 58.0 In 42.0        
203 150 125 In 95.0 Bi 5.0        
88 150 150 In 99.3 Ga 0.7        
225 151 143 In 90.0 Sn 10.0        
90 152 152 In 99.4 Ga 0.6        
91 153 153 In 99.6 Ga 0.4        
2 154 149 In 80.0 Pb 15.0 Ag 5.0    
92 154 154 In 99.5 Ga 0.5        
4 157 157 In 100.0            
204 175 165 In 70.0 Pb 30.0        
205 181 173 In 60.0 Pb 40.0        
231 186 174 Sn 86.5 Zn 5.5 In 4.5 Bi 3.5
227 187 175 Sn 77.2 In 20.0 Ag 2.8    
226 187 181 Sn 83.6 In 8.8 Zn 7.6    

Other Low Temperature Applications

In addition to the soldering, Indium Corporation provides low temperature solution for thermal management, hermetic sealing, fusible alloys, eye glass lens blocking and more.

Thermal Management

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 heat dissipation in sensitive components during operation, machining, and/or manufacturing.

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

Hermetic Sealing

Some sealing operations use pure indium and require no heat at all. The sealing process uses mechanical pressure to create the bond. The softness and malleability of indium, not to mention its ability to retain these characteristics at cryogenic temperatures, allows it to fill in imperfections in mating surfaces to create a hermetic seal.

Fusible Alloys

Low temperature or fusible alloys are commonly used in a variety of safety devices where they are designed to melt at a peak temperature to initiate a process. Eye glass lens blocking is another application where low-temperature or fusible alloys work well. The lens is held in place using a block of the alloy, which is then easily removed with hot water.

Some common fusible alloys are:
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%

Low-Temperature Soldering Products