Ion migration inhibiting plastics for electric and electronic component applications

Many electric and electronic components are made using resin flame retardant plastics to improve their fire resistance and prevent fires and combustion due to short circuits.

There are many different kinds of flame retardants, and suitable formulas are used in each resin material. Flame retardants can be divided into inorganic and organic categories. Red phosphorus is a typical example of an inorganic flame retardant. Organic flame retardants include phosphorous compounds such as phosphate ester, halogenated compounds such as brominated polymers, and nitrogen compounds such as melamine cyanurate.

Such flame retardants, however, can form substances that corrode metal depending on the environment the product is used in. Red phosphorus is one such example. It reacts with moisture in the air, forming phosphoric acid, which is a corrosive substance (refer to “Phosphoric acid formation mechanism” on the right). Phosphoric acid is conductive, so when it forms inside resin, insulation properties are adversely affected, resulting in elution of copper ions from the electrodes due to a weak electric current.

Normally, when used as a flame retardant, the surface of red phosphorus is coated with resin or a metallic compound. However, when the red phosphorus is not coated or insufficiently coated, phosphoric acid can be formed over time even if it works as a flame retardant initially, resulting in fire due to short circuits caused by ion migration.

For example, in 2014, NITE (Independent Administrative Agency, National Institute of Technology and Product Evaluation) published "Methods for flame retardant plastics and trouble cases caused by flame retardants" which states that the DC plug part on the secondary side of the AC adapter generates heat. There have been reports of accidents resulting in deformation. The cause was ion migration caused by red phosphorus added as a flame retardant to the resin material of the DC plug insulation.

With the above background in mind, demand is growing for flame retardant resin materials that do not use red phosphorus to prevent ion migration in electric and electronic component applications.

Moreover, with recent concerns about the global environment, brominated flame retardants such as polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE) fall under REACH regulations, driving demand for non-halogenated flame retardants. Due to the above reasons, the need for electric and electronic components that do not use resins with red phosphorus or halogenated flame retardants is on the rise.