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The “Invisible Skeleton” of Foldable Screens: How Does Betely Flexible Silver Paste Enable Displays to Withstand 200,000 Repeated Folds Without Failure?

2026-04-02 14:36

Every day, when you unfold your foldable smartphone, close your laptop, or even adjust the strap on your flexible‑screen smartwatch, have you ever wondered—how do these screens withstand repeated bending? Why does the touch control never fail? Why is the signal always stable?

The answer lies within those “silver wires” inside the screen—thinner than a strand of hair.

They are Betely Flexible Circuit Board Silver Paste …printed onto a film thinner than paper; after drying, it becomes the screen’s “touch‑sensing nerve” and “signal pathway.”

So where exactly is it used? In foldable screens, there are two key areas where it’s indispensable:

● Touch layer: It’s the layer that detects your finger’s position as you swipe across the screen. This layer is densely patterned with fine silver‑paste circuits, each line thinner than a human hair, which transmit the “where you tapped” signal to the phone’s processor.

● Connection cable: Between the screen and the phone’s motherboard lies a very thin flex cable, whose traces are also printed with silver paste, responsible for transmitting touch and display signals from the screen to the motherboard.

Let a single diagram help you understand.

Cross-section of a foldable screen:

Top: Cover plate (foldable) Stacked glass or plastic)

↓

Second layer: Touch‑sensing layer ← This layer is printed with silver‑paste circuits (even finer than a human hair)

↓

Third layer: Display layer (OLED emissive layer)

↓

Bottom: Backboard (support)

Today, we’ll explore how this type of silver paste—specifically designed for foldable displays—maintains stable conductivity and pristine touch performance even after 200,000 repeated bends.

Foldable screens have presented three major challenges for silver paste.

The biggest difference between a foldable screen and a conventional smartphone lies in the fact that it… It can be folded, rolled, and repeatedly opened and closed without damage. This presents three major challenges for silver paste:

● Bend-resistant: The screen must withstand over 200,000 open-and-close cycles without failure, and the silver paste must exhibit excellent flexibility to prevent cracking.

● Low-temperature curing: The thin-film substrates (such as PET and PI) inside the screen are not heat‑resistant; they begin to deform at temperatures of 200–300°C. Therefore, the silver paste must be cured at around 135–150°C.

● High precision: The circuitry on foldable screens is thinner than a human hair—some are as fine as 20 microns. For silver paste to be printed at such a minuscule scale, it must not break the conductive lines.

Conventional silver pastes struggle to meet all three of these requirements simultaneously. Betely SF‑21XX and SF‑12XX series were specifically engineered to address these demanding specifications.

Make the silver paste “soft as boneless”

The internal substrates of foldable screens are mostly flexible materials such as PET (polyethylene terephthalate film), PI (polyimide film), and TPU (thermoplastic polyurethane). Their greatest advantage is their “softness,” but their biggest drawback is their susceptibility to heat.

SF-2196 employs a halogen-free, low-temperature curing system:

● Curing temperature: 150℃ × 10 minutes

● Adhesion after curing: ≥5B (highest level)

This temperature range falls squarely within the tolerance limits of PET and PI, ensuring complete curing and stabilization of the silver paste without compromising the substrate. The halogen-free formulation also meets the environmental standards of leading end‑user brands, guaranteeing long‑term stability and reliability.

How thin can the lines be? Even thinner than a strand of hair.

The touch-control circuitry of foldable screens demands extremely high precision. The smaller the screen and the higher the resolution, the finer the traces become.

Betely excels in this regard:

● SF-2196: Minimum trace width and spacing: 80 μm × 80 μm

● SF-2880: Minimum line width and spacing: 20 μm × 20 μm

For comparison: the diameter of a human hair is approximately 70 μm, and the line width of the SF‑1288K is even thinner—less than one-third that of a hair. To print tens of thousands of such fine silver lines on a screen no larger than the palm of your hand, while ensuring no breaks or short circuits, places extreme demands on both the printing performance and the electrical conductivity uniformity of the silver paste.

From a parameter perspective:

● SF-2196: Sheet resistance ≤ 17 mΩ

● SF-1288K: Sheet resistance <50 mΩ

● Hardness ≥ 2H: Adhesion ≥ 5B

The wire is sufficiently thin, offers stable conductivity, features a scratch‑resistant surface, and exhibits strong adhesion. —All of these key indicators have reached a high level.

Compatible with a wide range of substrates, offering flexible solutions to meet diverse requirements.

Foldable displays involve a wide variety of substrate materials. The display layer may be made of PET or PI, while the touch‑sensing layer could consist of ITO glass, ITO film, nano‑silver film, or carbon‑nanotube conductive film—each with significantly different requirements for adhesion to silver paste.

Betely has conducted targeted development in substrate compatibility:

● SF-2196: Suitable for flexible substrates such as PET, PI, and TPU.

● SF-2155B: Suitable for core touch-screen materials such as ITO glass, ITO films, nano-silver films, and carbon-nanotube conductive films.

● SF-2880: It is also applicable to ITO glass, thin films, and nano‑silver films, and can achieve ultra‑fine traces as narrow as 20 μm.

Regardless of whether foldable displays employ nano‑silver wire, metal mesh, or ITO technology, Betely can provide a tailored silver paste solution.

Additional application scenarios for flexible silver paste

Foldable displays are merely the starting point for the application of flexible silver paste. As flexible electronics technology continues to advance, the following fields will also emerge as key areas of application:

● Wearable devices: Electrocardiogram electrodes and body-temperature sensor circuitry embedded in the watch strap

● In-vehicle flexible display: Curved touchscreen for the instrument panel and center console area

Betely flexible circuit silver paste is a material solution specifically developed for these flexible electronics applications.

Conclusion

From the earliest metal‑plate antennas, through ITO conductive glass, to today’s… Flexible silver paste circuitry —The evolutionary history of screens and antennas is, at its core, a history of continuous breakthroughs in materials and manufacturing processes.

A tiny silver wire can withstand 200,000 bends—not thanks to some “magic formula,” but because of Betely… Halogen-free system, low-temperature curing, precision printing, substrate compatibility The result of sustained, in-depth efforts in these areas.

Next time you unfold your foldable smartphone, take a moment to consider this: those “silver wires” tucked deep within the screen—thinner than a strand of hair—are far more flexible and resilient than you might imagine.

Betely is dedicated to the research, development, production, and sales of core materials in the electronic chemicals sector, enabling flexible conductivity that goes beyond mere bending.

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