Tin pest

Tin pest is a problem that happens to things made out of tin. It occurs when tin is exposed to low temperatures, changing the crystal structure of the metal. Tin pest can weaken tin structures and cause electrical problems like a short circuit or open circuit in electronics that use tin solder.

Historically, tin was alloyed with lead to prevent tin pest. When lead use was limited by the European Union's Restriction on Hazardous Substances Directive, the new lead-free solders did not have the same protection against tin pest. Controlling tin pest in lead-free solders became an important goal in metallurgy.

 Mechanism 
Tin has two main allotropes. At room temperature, it is the metallic β-tin, also called white tin. Around , it changes to α-tin, a non-conductive semimetal, also called grey tin. The change is autocatalytic: grey tin acts as a catalyst for the change, so the reaction continues speeding up until all the white tin has changed.

Grey tin has very different physical properties than white tin. It has the crystal structure of diamond and silicon. While white tin is a metal, grey tin is considered a semimetal or zero-band gap semiconductor. It is also brittle, unlike white tin which is ductile. Together, these properties mean tin pest can cause both physical weakness and electrical faults.

 Sources 

Category:Tin