General Review of Lead Free Solder Options
APC International has completed its evaluation of Lead Free Solder options for soldering to piezoelectric ceramics and devices. For RoHS compliance requirements, we now recommend Sn96 solder to replace the previous standard Sn62 lead based solder.
We have reviewed the basic literature available for lead free solders and consulted with experts from Alpha Metals and Indium Corp. Out of this, we selected the following products to evaluate for Lead Free Solder options:
- SN96 (Sn96/Ag4.0): Melt ~ 220C
- Alpha Lead-Free (Sn96/Ag3.5/Cu0.5): Melt ~ 220C
- Indium 241 (Sn95.5/Ag3.8/Cu0.7): Melt ~ 220C
- Indium 282 (Bi57/Sn42/Ag1.0: Melt ~ 140C
Sn96, Alpha Lead-Free, and Indium 241 will be considered equivalent and the group will generally be called Standard Lead-Free Solder of Sn96 Solder. Indium 282 will be called Low-Temp Lead Free Solder or Bi Solder.
The Sn96 solders have been used for many years for higher temperature piezo applications. It is now becoming the standard for lead-free solder. The melt temperature for the Sn96 solders is a little higher than Sn62, but they have better overall properties. The addition of Cu in the Sn96 solder alloy seems to help with wet out and strength of the solder joint. In general, Sn96 should be considered the standard Lead-Free Solder replacement for Sn62 Lead based Solder.
The Low-Temp Lead Free Solder (Bi Solder) is an option for some application. The Lower melt temperature is a plus, but the Bi has some concerns. The Bi cannot be exposed to Lead. The exposure to lead will seriously affect the melt temperature and quality of the joint. The MSDS for Bi should be reviewed to ensure proper handling and use. The Bi Solder should only be used after a technical review of the application.
We have tested all of the above listed solders and all are acceptable for RoHS Compliance.
To make your project a little easier, APC offers a soldering starter kit containing lead free solder.