Meeting power demands of USB-C connectors while reducing risk of electrical arcing

Thermoplastics, such as LCP, are commonly used materials for charging cables and power adapters in early versions of USB connectors. Now the newest USB-C connectors have more than double the output of older charging cables and adapters. When designing new USB-C connectors, you need a material with a high CTI rating for tracking resistance and superior bonding strength, along with material properties that enable strong weld lines and thin walls, to minimize the risk of arcing and possible fire. We have a material solution that is well positioned to meet all these needs.

With the capability to deliver up to 240 watts of power at 48 V, USB-C connectors have more than double the output of older charging cables and adapters. They can power up a wider range of consumer electronic devices at much faster speeds. But along with higher voltages comes more electrical stress to wiring insulation materials, increasing the risk of electrical arcing and potential fire.

As a design engineer, you understand that insulation materials used for charging cables and power adapters need to withstand rising levels of electrical and mechanical strain, as well as environmental impacts, such as low-and-high temperatures and humidity. Additionally, damage can be caused by a buildup of dust, sweat or moisture. These stressors can accelerate and enlarge insulation materials and systems, increasing the risk of electrical failure caused by gaps between injection molding shots of Type C connectors—ultimately leading to a fire hazard risk.

As the European Union and other regulatory bodies are supporting the widespread adoption of USB-C as the new standard for charging small- and medium-sized electronic devices by 2024, it’s imperative for manufacturers to develop electrical insulation systems that minimize safety concerns.

Offering you superior bonding strength

A weak bonding force between insert-molded parts is one of the main reasons power adapters fail. The insert-molded parts of USB-C connectors have small features and thin walls. While insert molding generally results in a structurally stable part, electrical breakdowns can occur when gaps form between the molded parts.

To achieve tight tolerances and a proper fitting, you must use a material for insert molding that provides a strong bonding force between the resin layers of the molded parts. This material must also be able to resist high temperature and high humidity environments. Liquid crystal polymer (LCP) has been used to manufacture micro-USB connectors, but due to its chemical structure, this material doesn’t provide a strong enough bonding force.

Envalior scientists conducted an experiment to compare the bonding performance of LCP and PA10T against Stanyl®, a high-performance aliphatic polyamide with high crystallinity. USB-C connectors were developed using insert molding with the following materials: Stanyl HFX50S, LCP and PA10T. 

A cross-section of each connector was observed under an optical microscope. The results showed clear cracks and gaps with PA10T. Gaps were also observed with LCP. The Stanyl material grade showed very smooth and good bonding results that were much higher in quality. Our scientists concluded that the superior bonding strength of Stanyl proved to be much higher than competitive PPAs.

How you can prevent arc tracking

To minimize the risks of electrical breakdowns and potential fires caused by arc tracking, it’s essential you use an insulating material with a high comparative tracking index (CTI) rating. This rating defines the maximum measured voltage that a material can withstand before an electrical breakdown occurs.

The performance of an insulating material can be determined by following a common industry test. It involves placing 50 droplets of an electrolyte solution (i.e., 0.1% ammonium chloride) onto the insulating material (typically 3 mm thick) and then measuring the rate at which a tracking path is produced on the material’s surface.

Our scientists carried out this test to compare LCP insulating material against Stanyl. After being exposed to 12 saltwater droplets, the connector made from LCP showed significant burn marks and electrical breakdown. But after dropping 60 saltwater droplets on the connector made from Stanyl, the insulation material remained structurally intact. The test results showed that Stanyl was more effective than LCP at preventing tracking in testing.

Enabling you to design durable and thin USB-C connectors

Compared to previous generations, USB-C connectors are designed with a much tighter pitch to house its 24 connector pins. To prevent short circuits from forming between the pins, a thin-walled insulating material is required that can demonstrate superior resistance to electrical tracking in high voltage environments to prevent potentially serious fire hazards.

As the dimension and pitch of USB connectors are becoming smaller and smaller in every new generation, you are aware that USB-C connectors require insulating walls that are much thinner than previous generations.

The terminal pitch of the latest USB-C connector version is 0.5 mm (about 0.02 in), which means the insulation material width is only 0.3 mm (about 0.01 in) between the two metal terminals. The thinnest wall on both sides of the USB-C receptacle connector may go down to 0.1 mm in the over-mold process. For you to achieve this level of thinness, it is very critical to use a thermal plastic with good flowability.

Thin insulation walls can be achieved by using Stanyl. This an electro-friendly and flame-retarded high heat polyamide offers excellent creep resistance, strength, stiffness, and fatigue resistance, not only at ambient temperatures but especially at high temperatures, while at the same time providing cycle-time advantages and excellent flow.

You can avoid weak weld lines too

Over its lifetime, a USB-C connector has to withstand thousands of insertions and removals as devices are charged. This requires you to choose durable materials that strike the right balance between toughness and stiffness.

When USB-C plug housings are molded, a weld line is formed on the front of the receptacle. To help absorb the impact of plugging and unplugging devices, the inside of the receptacle is also molded with thin ribs. The requires a material with high-flow properties. If the weld line is weak, cracking can occur.

When comparing the strength of type C tensile bars made from different materials, Stanyl was shown to demonstrate the strongest weld lines.

Envalior continues to optimize our material solutions for manufacturing next-generation electronics that process higher power levels and meet thinnovation trends. With more than 300 million USB-C connectors made from our materials on the market today, we’re prepared to partner with you through every stage of developing electronic devices that give your customers peace of mind, outperform the competition, and help you drive new business.

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John Hsieh

Advanced Engineering Manager

John Hsieh, advanced engineering manager for Envalior, has 20 years of product management and technical marketing experience within the entire electronics value chain. He has been with Envalior since August 2013 and has a master’s degree in mechanical engineering.

Published on

29 August 2023


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