A Metallurgical Phenomenon
Whiskers are a metallurgical phenomenon in which thin strands of metallic material grow away from the metal surface. They are a result of a spontaneous crystalline growth of tiny, filiform hairs from a metallic surface. Whiskers longer than 0.25" have been documented.
A Major Concern For The Electronics Industry
These thin strands can break away from the base material and cause problems such as electrical shorts and arcing in all types of electronic components. Tin whiskers are one of the more prevalent types of whiskers because of tin's use in electronic components and circuit boards.
What Causes Whiskers?
What causes whiskers to develop is not well understood and is the subject of much current research. Whiskers seem to be encouraged by compressive mechanical stresses including:
- Residual Stresses from electroplating
- Mechanically induced stresses
- Stresses induced by diffusion of different metals
- Thermally induced stresses
Adding Lead To Tin To Reduce Whisker Growth
The growth of tin whiskers can be reduced through the addition of lead to the tin coating. However, since many industries are looking to remove lead completely from their products for RoHS compliance, alternatives to lead need to be considered.
Non-Lead Alternatives To Whisker Growth
Studies have shown that Reflowed Tin or Hot Tin Dip coatings greatly reduce the risk of tin whisker growth. Other options that are thought to reduce the incidence of whiskers include coating with nickel before plating with tin, or using custom alloys that show resistance to whisker growth.
Consult With The Experts
Hi-Tech Plating can work with your design engineers to develop a strategy to minimize the possibility of whisker growth. Call us today at 1-617-389-3400.