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Increasing safety of the Virtual Link connector for AR/VR devices

29 November 2019
  • John HsiehAdvanced Engineering Manager

Artificial Intelligence (AI) will soon become intrinsically woven into the mobile experience and will touch our lives in many ways—just think of autonomous vehicles and how that will change the transportation industry and how we commute. Besides AI, there are two other mega computing platforms at the forefront of technology—Augmented Reality (AR) and Virtual Reality (VR). Both are based on graphics processing units (GPU), enabling GPU and real-time computing for very realistic computer graphics.

To give you an idea of how quickly the demand of these computing platforms is increasing, the AR/VR headset market hit 8.9 million units in 2018, and it is expected to reach 65.9 million units by 2022, fueled in large part by next generation headsets from Apple, Google and others, according to the International Data Corporation (IDC). And according to wikitude, mobile augmented reality reached an install base of 900 million in 2018 and is expected to cross 3.5 billion by 2022.


Reducing fire hazards

Although the quick growth of AR/VR technology is exciting, it does come along with a potential safety hazard. Just as there have been various reports of mobile devices catching fire during charging, there is the possibility of an AR/VR device catching on fire when charging via a Virtual Link connector.

Think of this real-life safety hazard example: When a consumer is using an AR/VR device connected to their PC, there can be a conductive contamination build up on the surface—this can be a pollutant, like dust, or condensation, etc. An electric field then generates a small current on the contaminated surface, which carbonizes the insulator material surface. The carbonized surface leads to a bigger current further degrading the surface, which then leads to arcing and a very high current, resulting in a fire hazard.

There are ways to decrease such a fire risk. Reducing environmental pollution as dust, sweat or moisture at the connector can be done via additional sealing. Also, using a high CTI insulator material is an efficient way to avoid fire hazards, thus increasing end-product safety. Creeping distance also plays a role in decreasing fire risk; however, the pitch size and minimum wall thickness of insulator plastics are defined and cannot be modified.

Keep in mind that the Virtual Link connector is based on the USB-C connector. The USB Type C has the thinnest wall receptacle at 0.12mm and the plug is 0.10mm thin. Liquid Crystal Polymer (LCP) or even regrind LCP are broadly used in the Micro USB connectors, but LCP is not the most suitable material for these connectors.

Balancing toughness and stiffness

Often, the detailed mechanical structures of Virtual Link connectors are different for companies, but across the board the biggest challenge is balancing toughness and stiffness in the material solution utilized.

For example, the weldline located in the front side of the plug needs high weldline strength materials and the very thin ribs require a material with a high flow and toughness. Plus, there are other properties that need to be considered too.

 

So, we did a mechanical test looking at the insertion force/extraction force; durability of insertion/extraction cycles (minimum 10,000 times); cable flexing; cable pull out; four-axis continuity test; and wrenching strength of different materials.

We found that materials used for Virtual Link connectors need to have the following requirements:

  • High flow, capable for 0.1mm wall thickness design
  • High stiffness, toughness and weldline strength
  • High retention force between contacts and plastic housing
  • High wear resistance (>10,000 times mating/unmating durability test)
  • Good process window, capable for second insert molding
  • Halogen free UL94-V0 and high CTI to support USB PD 2.0 and 3.0 standard (up to 54 Watt power)
  • Good colorability to support consumer electronics market needs
  • Lead free reflow soldering without blistering
  • Compatible with high speed signal transfer up to 20 Gbps

Regarding Virtual Link receptacles, there can be a concern about blistering. A very important factor of blistering is wall thickness, but there is no risk for blistering if the wall thicknesses in the tips are all below 0.2mm. Also, all wall thickness is usually in the back-seat, which is above 0.8mm, hence, an extremely low risk for blistering.

For various OEMs, we have a 1kt track record of the Stanyl grades used in Type C connectors, and no blistering complaints were ever received about USB-C type connectors. Plus, Stanyl has a high CTI and fails only after more than two times the number of salt solution droplets compared to low CTI LCP during the CTI test.

In real USB Type C application environments, an insulator with a high CTI can tolerate much higher voltage or much higher contamination levels. Thus, product reliability of a critical charging interface, such as USB Type C, is significantly increased by using a high CTI insulation material.

To learn more about Stanyl grades, or to request test samples, contact us or visit plasticsfinder.com for additional information, including technical data sheets.

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