Use of Red Phosphorus (Ion Migration) in AC/DC Power Adapters — Desktop & Wall-Mount and Our Company’s Response

We have taken early measures against red phosphorus in AC/DC power adapters — desktop & wall-mount — and switching power supplies, even before the issue recently came into the spotlight. This page introduces some of our thorough measures against so-called silent changes.

Classification of Flame Retardants and Red Phosphorus

Flame retardants are broadly classified as organic or inorganic based on their components, and red phosphorus is classified as an inorganic flame retardant. Flame retardants containing red phosphorus (known as red phosphorus-based flame retardants) are added to certain plastics to enhance their flame resistance.

Around the summer of 2000, issues with hard disk drives (HDDs) began to surface among PC and PC server users. The cause of the failure was short-circuiting between pins inside the LSI package due to migration of Ag, which was used as the pin material. Although this HDD failure had a major impact on the electronics industry, the phenomenon of metal migration caused by phosphorus (P), moisture, and electric fields became widely recognized within the industry.

However, accidents occurred suggesting that this knowledge did not fully permeate upstream to plastic material manufacturers. In 2014, NITE (National Institute of Technology and Evaluation) released a report titled "Flame Retardant Methods for Plastics and Trouble Cases Due to Flame Retardants." One of the cases described involved the DC plug section on the secondary side of AC/DC power adapters — desktop & wall-mount types — becoming hot and deforming. The cause was identified as migration triggered by red phosphorus added as a flame retardant to the resin of the DC plug’s insulation sleeve, which was made of polybutylene terephthalate (PBT).

Our Countermeasures and Efforts to Eliminate Red Phosphorus

In response to customer requests, our company began eliminating red phosphorus-based flame retardants from insulation sleeves even before the NITE report was published. Additionally, from April 2016, we started removing red phosphorus from flame retardants used in plastics (heat shrink tubing) where electric fields are applied in DC plug sections. Furthermore, to prevent component manufacturers from making so-called "silent changes," we clearly state "No use of red phosphorus flame retardants" in component approval documents to ensure proper management by manufacturers. Since April 2016, we also inspect all such components upon receipt using a simplified phosphorus (P) content testing device (RoHS X-ray fluorescence equipment), managing them under an upper control limit of 1000 ppm.

As for existing components, none of the resin parts mounted in our finished products contain red phosphorus; we use non-red phosphorus-based flame retardants. For these parts, we have acquired and stored certificates from each component manufacturer stating "Red phosphorus not contained" or "No intentional use of red phosphorus," ensuring strict management.

For newly adopted components, we require component manufacturers to clearly indicate in the approval documents whether the part is "red phosphorus-free" or "not intentionally containing red phosphorus" during the approval process.