PPS resin with excellent tracking resistance
that shortens creepage distance under high voltage

Securing creepage distance becomes a constraint in the design of electrical components

Generally, electronic circuits are made by forming a circuit with conductors on an insulator substrate. However, triggered by the accumulation of dirt on the circuit, an electrical path (track) different from what was originally intended may be formed on the surface of the insulator. The phenomenon where the circuit is destroyed by this is tracking, and to avoid it, it is important to secure the creepage distance.
Creepage distance is the distance between conductors measured along the surface of the insulator existing between them. Because it is measured including the unevenness on the insulator surface, it can be extended to some extent by means such as digging grooves on the surface. However, basically, the finer the circuit becomes, the harder it is to secure the creepage distance, and tracking is especially likely to occur under high voltage. This hinders the downsizing and higher voltage of electrical components.

Realizing tracking resistance suitable for high-voltage components with PPS resin

To prevent tracking in small circuits, one method is to adopt a material that has a property that makes tracking unlikely to occur (tracking resistance) for the insulator.
One of the materials that has been adopted for many electrical components such as power modules so far is PPS resin, which excels in heat resistance and flammability. However, conventional PPS resins had a challenge in tracking resistance, making them unsuitable for use as insulators under high voltage. Therefore, we reviewed the material formulation design of PPS resin and developed two products, "Toray TORELINA™ PPS resin A660HV" and "Toray TORELINA™ PPS resin A676ES1B," equipped with high tracking resistance.

Among these, TORELINA™ A660HV utilizes the high heat resistance of PPS resin while realizing the highest level of tracking resistance of CTI 600V^*1 (Material Group I) through polymer technology. In addition, TORELINA™ A676ES1B improves Heat Cycle Resistance, which is important for use under high temperatures, in a well-balanced manner in addition to CTI.

1. CTI (Comparative Tracking Index): An index showing the tracking resistance of a substance. It is expressed by the maximum voltage that can be applied without causing tracking in a state where contamination exists on the insulating material.

Performance comparison

(〇: Excellent, △: Slightly inferior, ×: Inferior)

We can conduct simulations such as structural analysis, which are important for the shift to EVs, and various analyses. Upon the introduction of "Toray TORELINA™ PPS resin A660HV" and "Toray TORELINA™ PPS resin A676ES1B", we can also propose solutions based on these analyses. In particular, analysis of component behavior such as warpage and stress concentration under high-temperature environments is utilized by many customers.