What Is a Whisker?
Whiskers are fine, whisker-shaped, or needle-shaped single-crystal metal structures that spontaneously grow from the surfaces of metals, commonly tin (Sn) or zinc (Zn) platings. These tiny structures, typically 1-2 microns in diameter and 1-10 microns in length, can cause short circuits in electronic devices by bridging different potential points or by breaking off and infiltrating circuits.
Whiskers were a notable issue in the mid-20th century with the use of zinc and tin in plating and soldering. The shift to lead-free solder since 2000 has seen a resurgence of whisker-related problems in electronic equipment.
Uses of Whiskers
While generally problematic for electrical equipment, whiskers are valued in other applications due to their high strength, heat resistance, and corrosion resistance. They are used as reinforcing materials in ceramics, metals, and plastic composites, particularly in microwave-heatable ceramics and hard ceramics for cutting tools.
Features of Whiskers
Whiskers are categorized into genuine and non-genuine types:
- Genuine Whiskers: These single crystals grow on metal surfaces at room temperature under minor compressive stress. Commonly found on tin, zinc, and cadmium, they can also occur on other metals like silver, gold, iron, and lead under high temperatures.
- Non-Genuine Whiskers: Typically produced artificially and utilized as reinforcing agents in metals and plastics, these whiskers are formed through various processes like vapor phase condensation, electrolytic deposition, and thermal decomposition.
Silicon carbide or silicon nitride whiskers are also used in some applications for reinforcement purposes.