Use of red phosphorus in AC adapter (ion migration) and our response

Our company has been proactively addressing the issue of red phosphorus in AC adapters and switching power supplies even before it recently came under the spotlight. This page introduces some of our thorough measures against so-called silent changes.

Classification of Flame Retardants and Red Phosphorus

Flame retardants can be broadly classified into organic and inorganic types based on their components, and red phosphorus is categorized as an inorganic flame retardant. Flame retardants containing red phosphorus (referred to as red phosphorus-based flame retardants) are added to certain plastics to improve their flame resistance.

Around the summer of 2000, issues with hard disk drive (HDD) failures began to emerge among PC and PC server users. The cause of these failures was short-circuiting between pins within the LSI package, due to the migration of Ag, the material of the pins. Although the HDD failure problem had a major impact on the electronics industry, it also increased awareness within the industry of the phenomenon where metal migrates in the presence of phosphorus (P), moisture, and electric fields.

However, an incident occurred suggesting that this knowledge had not fully permeated to plastic manufacturers supplying raw materials. In 2014, NITE (National Institute of Technology and Evaluation) published a report titled “Methods of Flame Retardation for Plastics and Trouble Cases Involving Flame Retardants,” which described an incident where the DC plug part on the secondary side of an AC adapter overheated and deformed. The cause was identified as migration caused by red phosphorus added as a flame retardant to the insulating sleeve resin, polybutylene terephthalate (PBT), in the DC plug part.

Our Measures and Commitment to Red Phosphorus-Free Solutions

In response to customer requests, and prior to the release of the NITE report, our company had already begun the transition to red phosphorus-free flame retardants in insulating sleeves. Starting in April 2016, we also began using red phosphorus-free flame retardants in plastics (heat-shrink tubing) used in areas of the DC plug where electric fields are applied. Additionally, we manage suppliers to prevent so-called “silent changes” by requiring the phrase “Red phosphorus flame retardants not used” to be clearly stated in component approval documents.

Starting in April 2016, we also began measuring the phosphorus (P) content in parts using simple measurement equipment (RoHS X-ray fluorescence analyzer) during our incoming inspection process. We manage this with an upper control limit set at 1000 ppm.

As for existing components, all resin materials implemented in our products do not contain red phosphorus and instead use red phosphorus-free flame retardants. For these as well, we obtain and retain certificates from each component manufacturer stating “Red phosphorus not contained” or “Red phosphorus not intentionally added” to ensure thorough management.

For newly adopted components, we require component manufacturers to specify in the component approval documents that the parts are “Red phosphorus not contained” or “Red phosphorus not intentionally added” during the approval process.