Our correspondence about red phosphorus use (ion migration)

Flame Retardants Classification and Red Phosphorus

Flame retardants are classified into organic and inorganic types, with red phosphorus falling into the inorganic category. Red phosphorus-containing flame retardants, known as red phosphorus-based flame retardants, are added to certain plastics to enhance their flame resistance.

From around the summer of 2000, users of PCs and PC servers began experiencing HDD (Hard Disk Drive) failures. The failures were caused by short circuits between pins inside the LSI package due to the migration of the material Ag (Silver). This issue of HDD failure had a significant impact on the electronics industry. Still, it also led to the recognition of metal migration phenomena caused by phosphorus (P), moisture, and electric fields.

However, this knowledge did not fully permeate to the raw material plastic manufacturers, leading to incidents. In 2014, NITE (National Institute of Technology and Evaluation) published "About Trouble Cases by Flame Retardation Methods and Flame Retardants in Plastics," which included incidents where the DC plug part on the secondary side of an AC adapter overheated and deformed. The cause was migration caused by red phosphorus added as a flame retardant to the resin of the insulation sleeve (also known as bushing) made of Polybutylene Terephthalate (PBT).

Our Measures and Efforts Towards Non-Red Phosphorus Usage

Even before NITE's publication was released, we started replacing red phosphorus in insulation sleeves with non-red phosphorus flame retardants in response to customer requests. From April 2016, we also began using non-red phosphorus flame retardants in plastics (heat shrink tubes) used in areas of the DC plug part where an electric field is applied. To prevent what is known as a silent change by part manufacturers, we clearly state "No use of red phosphorus flame retardants" in the part approval documents and manage accordingly. Additionally, for these parts, since April 2016, we have been measuring the phosphorus (P) content using a simple measurement device (RoHS fluorescence X-ray equipment) during our incoming inspection, managing it with an upper control limit of 1000 ppm.

For existing parts, other plastics (cases, AC pins, AC inlets, DC cord sheathing, AC cord sheathing) are using non-red phosphorus-based flame retardants. We manage these by obtaining certifications from each part manufacturer stating "No red phosphorus content, or no intentional inclusion of red phosphorus."

For new parts, during the part approval process, we require our component supplier to clearly state "No red phosphorus content, or no intentional inclusion of red phosphorus" in the part approval documents.