Indium Corporation's extensive solder alloy list contains over 200 alloys and pure metals. Some of these alloys have been around for decades while several have recently been created to address a variety of challenges including:
- RoHS requirements for Pb- or Cd-free alloys
- Low-temperature requirements to avoid damage of components or substrate materials
- Devices with higher thermal output requiring a thermal interface materials to help dissipate the heat generated
- Need for high-reliability alloys
- Improved drop shock alloys for hand-held devices
- Hermetic sealing
So, how do you know which is the right alloy for you? There are a few basics to consider, including:
- Operating temperature of your final product
- RoHS or other environmental requirements
- Your current assembly process
- Any conditions that might limit your choices, such as component and substrate temperature constraints; gold or other metallizations
For more information on this, go to our new solder page.
If this seems overwhelming, don't despair! Indium Corporation's experts in solder selection will spend time talking to you and providing their input.
One expert is Tim Jensen. Tim is our Engineered Solder Product Manager so he has a great deal of expertise with "non-standard" alloys. Here he discusses Low-Temperature Alloys:
There are many times when a low-melting point solder can be used to increase the reliability of electronics. For this discussion, a low-temperature alloy is one that has a melting point lower than that of the commonly used SAC 305 (217°C). A lower temperature solder alloy will require a lower peak temperature in the reflow process and this will result in a reduced risk of thermal damage to the components and warping of the board. These issues can lead to reduced reliability of the end product as well as head-in-pillow and non-wet open defects.
Lower temperature alloys also have the benefit of being Pb-free. Some of the more popular alloys in use include:
Indalloy #254 (86.9Sn 10In 3.1Ag). This alloy melts at 205°C and exhibits very good ductility due to the 10% indium.
Indalloy #227 (77.2Sn 20In 2.8Ag). By increasing the indium content to 20%, the liquidus point of this alloy decreases to 187°C. The alloy has good reliability and high ductility and is best for products that operate at temperatures less than 100°C.
Indalloy #282 (57Bi 42Sn 1Ag). This alloy melts at 140°C and can enable a much lower temperature reflow process than SAC305 and is commonly used in step soldering on a PCB where SAC305 is already present.
Indalloy 1E (52In 48Sn). With a eutectic melting point of 118°C, this alloy can be used to solder components with very high temperature sensitivity. And, with the 52% indium content, this alloy also has extremely good thermal conductivity.
Choosing the right alloy for the right application is not always easy. The Pb-free alloys mentioned above are some of the most commonly used low-temperature solders that can produce high reliability electronics when used in the appropriate application.