Better materials for wireless charging coils key R&D objective

Wireless charging coil makers look to switch to amorphous alloys such as iron-based and nanocrystalline types for higher magnetic conductivity and efficiency.

China suppliers of wireless charging coils are exploring options to improve product performance as wireless charging technology finds increasing adoption in the latest electronics devices. The last includes smartphones and wearables such as iPhone X, iPhone 8, iPhone 8 Plus and Apple Watch. Current trends spurring makers' initiatives are for high power and reliability to realize enhanced charging efficiency and fast charging.

These attributes are achieved using different magnetic materials. At present, ferrites such as NiZn and MnZn are widely employed. Amorphous alloys, however, are gaining the attention of local companies. In particular, iron-based and nanocrystal kinds are being considered, which are seen to replace conventional ferrites. The alloys boast greater magnetic conductivity, enabling power transfer at a higher efficiency, in addition to having thinner profiles.

Developing slim wireless charging coils has always been on the agenda in the line in China. Releases such as those from Shenzhen Hoholot, which are designed for wearable devices, measure 25x0.75mm. The units have 12.5µH±10 percent inductance, 100V rated voltage and 500mA rated current.

Customization remains a highlighted capability, which accounts for as much as 80 percent of business for some companies. On their own, however, makers will sustain R&D work to sharpen competitive edge in the face of growing demand.

The global shipments of wireless charging receivers hit 325 million units by the end of 2017, rising 40 percent YoY, according to IHS Markit. It is expected the market will have a CAGR of up to 50 percent within the next two years and exceed $10 billion in scale by 2019. Besides smartphones and wearable devices, the key catalysts include tablet PCs, electric vehicles, smart home products and robotics.

Anticipating the benefit to the wireless charging coils manufacturing sector from the local and export markets, most China companies plan to raise their output by 20 to 50 percent in the year or two ahead.

There are approximately 300 makers of wireless charging coils in China and about 80 percent are local enterprises. The line accounts for 20 to 50 percent of shipments, and coils, transformers and other components the rest.

More than half of the suppliers are in Guangdong province's cities such as Shenzhen and Dongguan, where most electronics manufacturers are based. A number operate in Suzhou and Yueqing in the provinces of Jiangsu and Zhejiang, respectively.

Typical selection

Wireless charging coils in round and rectangular configurations make up the common range in China. These come in variants with single, double or triple coils with an output voltage of 5, 7 or 10V and power transfer efficiency surpassing 70 percent.

The key applications include wearable devices, smartphones, tablet PCs, gaming devices and flashlights.

The main components and materials used in manufacturing wireless charging coils are ferrite cores, aluminum heat sinks, enameled wires and PET. All come from the domestic supply, although some companies accommodate requests for imported versions.

Input costs rose in the past year but most makers kept their prices steady to cope with intense competition as more players venture into the line. This trend will persist through 2018.

The products in this gallery have been handpicked by our China-based market analyst for representing current trends in wireless charging coils from China makers.

3-coil wireless charging coil meets CE, FCC, RoHS

Anhui Shirui Electronic Technology Co. Ltd's wireless charging coil, Shirui-WM-16171 model, has three coils and suits Qi-compliant devices. It bears CE and FCC approval and follows RoHS requirements. The minimum order is 500 units for delivery within 7 days.

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UL-listed wireless charging coil uses NiMn ferrite

From Meisongbei Electronics Co. Ltd, this UL-listed wireless charging coil for Qi devices, MDWT-50-6 model, adopts NiMn ferrite. It operates in -20 to 105 C. A flexible sheet variant is available. Delivery of a 500-unit minimum order is within 3 days.

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Wireless charging coil with 7 to 15µH inductance

Designed for mobile phones, Shenzhen Qinxinlong Electronic Co. Ltd's model QXL-018 wireless charging coil has 7 to 15µH inductance and 70 to 80Mohm DC resistance. This 44x52x1.2mm unit uses a self-adhesive wire in 0.02 to 4mm diameter.

The maker requires a minimum order of 5,000 units. Delivery lead time is 7 days.

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Wireless charging coil has ≥70% transfer efficiency

This wireless charging coil from Zhongshan Kingrong Electronics Co. Ltd, KRE-Q01 model, has 5VDC, 2A or 9VDC, 1.7A input and 9VDC, 1A output. The output power is 5 to 10W and the standby power <100mW.

The WPC 1.2-compliant unit operates on 110 to 205kHz and has ≥70 percent transfer efficiency. It measures 70x65x6mm.

The minimum order is 500 units and delivered within 15 days.

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