Bismuth in many languages1
German: Wismut - r
Bismuth (Bi) is being used more and more as a replacement for lead in solder alloys because it is non-toxic. Although the melting temperature of pure bismuth is 271°C, the addition of bismuth will lower the melting temperature of most metals it is alloyed with. Bismuth compounds are also widely used in medical and cosmetic applications.
- The most popular lead-free bismuth solder alloys are Indalloy® #281 (58Bi 42Sn) which melts at 138°C and Indalloy® #282 (57Bi42Sn1Ag) which melts at 140°C. The addition of the 1% Ag makes the alloy more malleable. Both alloys can be used for step soldering applications. After the initial joints are made with a standard SAC alloy (220°C) subsequent soldering operations can be done using the bismuth alloys.
- Indalloy #281 and #282 have joint properties similar to those of tin-lead solders, with superior fatigue and copper dissolution characteristics.
- Bismuth is the most diamagnetic and the least thermally conductive of all metals
- In addition to being non-toxic it does not oxidize as readily as lead does.
Bismuth Blog Posts
Here’s a true story regarding the service temperature of solder joints. Yesterday, as I left work, I noticed that it felt really hot outside. I got in my car and cranked up the AC. I...
If you haven’t heard about Bi-containing (bismuth) solder alloys recently, that may change in the near future. Low-melting Bi-containing solders are now in increasing use and gaining popularity due to their lower melting temperatures—58Bi/42Sn is eutectic at 138°C and 57Bi/42Sn/1Ag melts 137-139°C (both are Pb-free alternatives). A low-temperature solder is advantageous...
I’ve always been a strong believer that a customer should not get a solder alloy that just “works” for their application, they should get the best alloy for their application. Of course, this is...
From One Engineer to Another®
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