There are two types of migration, electromigration and ion migration (electrochemical migration), and this page covers information on the latter, which occurs due to external factors.
Ion migration occurs when there is poor insulation between electrodes due to factors such as chemicals or heat, causing elution of the electrode metal and a subsequent short circuit.
To support our customers’ initiatives in making products used in electric and electronic applications, we offer a variety of engineering plastics that inhibit ion migration, haveare flame retardancet, and are superior in terms of various electrical properties (tracking resistance (CTI), etc.), glow wire ignition temperature (GWIT, etc.), long-term heat resistance (UL 746B RTI, etc.), and weather resistance, (UL 746C f1, f2). For example, using a material that does not result in ion migration suppresses short circuits between terminals, contributing to improved product safety, and smaller, more compact product designs.
Red phosphorus-free flame Flame retardance Materials that suppresses ion migrationFlame retardance grade
Asahi Kasei offers a range of products that are suitable for use in electric and electronic applications including flame retardant resin materials such as LEONA™ and XYRON™ , which eliminate ion migration triggered by flame retardants or slow progression compared to products that use red phosphorous.
Ion migration resistance evaluation methods
This section covers testing methods for evaluating the ion migration resistance of resin materials.
As shown in Figure 1, copper electrodes are affixed to plates of various resin materials and high voltage is applied under high temperature and high humidity conditions.
Ion migration occurs in the following way in this test:
The flame retardant breaks down under high temperature, high humidity conditions, forming corrosive substances 2:
Copper electrodes dissolve, generating copper ions 3:
Copper ions receive an electron and are deposited as a metal 4:
Steps 1 to 3 above are repeated, and the deposited copper is gradually extended to the other electrode
After exposure to the above testing conditions for a certain period of time, the copper distributed across the electrodes was researched using elemental analysis. When ion migration occurs, the copper element is gradually extended from one electrode to the other as shown in Figure 2.
Ion migration resistance evaluation results
The evaluation results for the product using red phosphorus and the XYRON™ flame retardant series are shown in Figure 3. There is no ion migration in the
XYRON™ flame retardant series, confirming the excellent results compared to the general product made using red phosphorus.
Next, the evaluation results for the LEONA™ flame retardant series are shown in Figure 4.
It was confirmed that there is no ion migration with the FR370. Although ion migration was confirmed to have occurred in the SN11B, the extension of copper was less than half that of the general product made using red phosphorus, confirming its slow progres
The above evaluation results confirm that Asahi Kasei’s LEONA™ and XYRON™ flame retardant series are resistant to ion migration. And because progression is slowed compared to products using red phosphorous, these materials are suitable for use in electric and electronic applications.
Principles of ion migration occurrence and case studies
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.
Flame retardant resin market trends
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.