Last winter, I bought a brand-new foldable phone, excited about its sleek design and flexible screen. But after a month, I hit a problem: the wireless charger I’d used for my old phone wouldn’t work with it. The issue? My old phone was flat, so its rigid PCB-based wireless charging coil fit perfectly on the charger. But the foldable phone’s battery was curved, and its rigid coil couldn’t bend to match—so the charging connection was spotty at best.
I took it to a repair shop, and the technician showed me the fix: a replacement FPC (Flexible Printed Circuit) with an integrated charging coil. “FPC is the only way to make wireless charging work for curved or foldable devices,” he said, pointing to the thin, bendable circuit. “It follows the shape of the battery, so the coil stays aligned with the charger.” Within an hour, my phone charged perfectly again.
That experience made me realize: FPC isn’t just a “nice-to-have” in wireless charging—it’s a game-changer. Wireless charging devices come in all shapes and sizes now: curved phones, foldable tablets, smartwatch chargers, even wireless charging pads built into car dashboards. Traditional rigid PCBs can’t adapt to these varied scenarios, but FPC’s flexibility lets it fit, align, and work reliably where rigid boards fail.
In this article, we’ll dive into real-world wireless charging scenarios where FPC shines, share stories from engineers who design these devices, and break down how FPC’s flexible structure solves the biggest 适配 (adaptation) challenges.
Before we talk about FPC’s strengths, let’s understand why rigid PCBs are falling short. Wireless charging relies on two key things: coil alignment (the charging coil in the device must line up with the coil in the charger) and form factor compatibility (the circuit must fit the device’s shape). Rigid PCBs struggle with both:
Curved phones (like the Samsung Galaxy S23 Ultra’s slight curve) and curved wireless charging pads (built into furniture) need coils that bend with the surface. A rigid PCB’s coil is fixed—if the device curves even 5 degrees, the coil shifts out of alignment, and charging slows or stops.
“We tested rigid PCBs for our curved wireless charging pad,” said Lisa, an engineer at a U.S. home electronics company. “The coil on the rigid board stayed flat, so only devices with perfectly flat backs charged. We switched to FPC, and suddenly, curved phones and even rounded smartwatches worked.”
Foldable phones and tablets bend hundreds of times a day. A rigid PCB in the charging circuit would crack after a few folds—breaking the coil and killing charging. Even if it doesn’t crack, the rigid board pulls the coil out of alignment every time the device folds.
Raj, a design engineer at an Indian smartphone brand, learned this the hard way: “We prototype-tested a foldable phone with a rigid charging PCB. After 200 folds, the PCB cracked, and the wireless charging stopped working. FPC was the only solution—it bends with the device, no cracks, no alignment issues.”
Smartwatches, fitness trackers, and wireless earbud chargers are tiny—every millimeter of space counts. Rigid PCBs are thick and inflexible, so they take up valuable room that could be used for bigger batteries. FPC is thin (as little as 0.1mm) and can be folded or wrapped around components, saving space.
“We needed to fit a wireless charging coil into our smallest fitness tracker,” said Mike, an engineer at a European wearables company. “A rigid PCB would have made the tracker 3mm thicker—too bulky. FPC let us wrap the coil around the battery, keeping the tracker slim and still charging fast.”
FPC’s flexibility isn’t just about “bending”—it’s about solving specific problems in different charging scenarios. Below are three common scenarios where FPC is essential, with real examples from engineers.
Curved devices need charging coils that match their curve to stay aligned with the charger. FPC’s flexible base lets manufacturers print coils directly onto the film, creating a “curved coil” that follows the device’s shape.
Lisa’s U.S. company used this for their furniture-mounted wireless charger (built into a curved desk):
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They printed a wireless charging coil onto a 0.125mm-thick FPC.
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The FPC was glued to the desk’s curved surface, so the coil curved naturally.
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Result: Curved phones, flat phones, and even rounded smartwatches all charge seamlessly—no alignment issues.
“Before FPC, we had to make the desk’s charging area flat, which ruined the design,” Lisa said. “Now the charger follows the desk’s curve, and customers love it.”
Key FPC Advantage: Shape Matching—FPC coils can be custom-curved to fit any device, ensuring constant alignment with the charger.
Foldable devices need charging circuits that bend without breaking. FPC’s polyimide base is flexible and durable—most FPCs can withstand 10,000+ folds without cracking. Engineers also design FPCs with “stress relief” loops in the fold area to handle repeated bending.
Raj’s Indian smartphone brand used FPC for their foldable phone’s wireless charging:
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They placed the charging coil on an FPC with a small loop in the fold zone.
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The loop stretches slightly when the phone folds, taking stress off the coil and traces.
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Result: The phone folded 10,000 times (the equivalent of 3 years of use) with no charging issues.
“Rigid PCBs would crack after 200 folds,” Raj said. “FPC handles the bending like it’s nothing—our test phones still charge perfectly.”
Key FPC Advantage: Flex Durability—FPC survives repeated folds, keeping the charging circuit intact.
Compact wearables need to save space, and FPC’s thinness and flexibility let engineers fit charging coils in tight spots. FPC can be wrapped around batteries, folded under sensors, or even placed on the inside of the device’s case.
Mike’s European wearables company used FPC for their fitness tracker:
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They used a 0.075mm-thick FPC with a tiny charging coil (15mm diameter).
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The FPC was wrapped around the tracker’s battery, using space that would otherwise be empty.
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Result: The tracker stayed 8mm thick (vs. 11mm with a rigid PCB) and charged in 1.5 hours—same as bigger devices.
“We couldn’t have made the tracker this slim without FPC,” Mike said. “It’s the difference between a device people wear and one they leave at home.”
Key FPC Advantage: Space Efficiency—FPC’s thinness and flexibility let it fit in tiny spaces, keeping wearables compact.
Let’s look at a company that solved a big wireless charging problem with FPC. A Chinese automotive parts maker wanted to build a wireless charger for car dashboards—most dashboards are curved or have odd shapes, and rigid PCBs couldn’t fit. Here’s how they did it:
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Car dashboards are curved and have limited space—rigid PCBs either didn’t fit or forced the charger to be bulky.
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Drivers need to charge phones quickly, so alignment was critical—rigid coils often misaligned with phones.
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The charger needed to withstand vibration (from driving) and temperature changes (hot/cold cars)—rigid PCBs cracked under stress.
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FPC Coil Design: They printed a wireless charging coil onto a 0.1mm-thick FPC, which could be curved to match any dashboard shape.
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Stress Relief: They added small loops to the FPC to handle vibration and temperature-related expansion.
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Space-Saving Mounting: The FPC was glued directly to the dashboard’s inner surface, using no extra space.
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The charger fit 95% of car dashboards (vs. 40% with rigid PCBs).
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Phone alignment issues dropped by 80%—drivers just set their phones down, and charging started.
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After 1 year of testing, 0% of chargers failed (vs. 12% of rigid PCB chargers, which cracked from vibration).
“The FPC turned a product that barely worked into our bestseller,” said Wei, the company’s engineering director. “Car manufacturers now ask for it specifically.”
Wireless charging isn’t just for flat phones anymore—it’s for curved devices, foldables, wearables, and even cars. Rigid PCBs can’t keep up with these varied scenarios, but FPC’s flexibility, durability, and space efficiency make it the perfect solution.
The engineers I talked to all agreed: FPC doesn’t just “work” in wireless charging—it makes new charging scenarios possible. Whether it’s a curved desk charger, a foldable phone, or a tiny fitness tracker, FPC adapts to the device, not the other way around.
Next time you use a wireless charger that fits perfectly or works even when your device is curved, chances are there’s an FPC inside. And as wireless charging becomes more everywhere—on planes, in cafes, in your pocket—FPC will be the quiet force making it all work.
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Whether you are engaged in electronic manufacturing, smart device R&D, or any other field with circuit board needs, feel free to reach out to us via email at sales06@kbefpc.com. We look forward to addressing your inquiries, customizing solutions, and sincerely invite partners from all sectors to consult and collaborate, exploring new possibilities in the industry together.
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