When foldable phones become the "new favorite" of technology trends, when in car flexible screens are integrated into smart cockpits, and when wearable devices are close to the skin to perceive health - flexible displays are redefining human-computer interaction in a "new form". However, in the "dark place" that users cannot see, a "ultimate challenge" about reliability always exists: over 30% of flexible screens experience "crease deepening", "film peeling" or "display color deviation" within 6 months of being launched, and the fundamental reason is the interaction between "bending mechanical stress" and "humid and hot environment", leading to material interface failure.

In traditional testing, enterprises often use "bending test machines to test bending resistance separately" or "constant temperature and humidity chambers to test moisture and heat stability separately". However, in actual use, flexible screens often face complex scenarios such as "edge folding stuffiness" (such as contact with sweat during daily opening and closing of foldable phones) and "first folding and then wetting" (such as outdoor storage after rainy days). This "dynamic coupling" stress environment has caused a deviation of over 40% between a single test result and the actual product lifespan, and even led to a collective complaint from users about a certain top brand foldable screen phone being "bent and delaminated under high temperature and high humidity", resulting in a direct loss of over 1 billion yuan.

As a "reliability standard" in the field of flexible display testing in China, Shanghai Hexiaoyi has been deeply involved in interface science of display materials for 12 years. Based on its technological accumulation in mechanical stress control, multi field coupling testing, micro damage characterization and other fields, it has launched the "Flexible Screen Bending Damp Heat Interaction Testing Solution", which achieves accurate synchronous simulation of three-dimensional stress of "bending temperature humidity time", helps enterprises predict the risk of interface failure 2-3 years in advance, and promotes the transition of flexible display from "usable" to "durable".

1、 The 'fatal coupling' of flexible screen failure: the 'double strangulation' of bending and dampness and heat

The core structure of a flexible screen is "substrate (PI/UTG glass) - display layer (OLED) - packaging layer (film/glass) - touch layer", and the thermal expansion coefficient (CTE) and elastic modulus of each layer material vary greatly. When bending (mechanical stress) is combined with humidity (temperature and humidity), the interface failure will exhibit a failure logic of "1+1>2":

Fatigue accumulation of bending: Each bending (such as opening and closing a folding phone) will generate microcracks at the material interface (such as PI substrate and OLED packaging adhesive). After long-term accumulation, the cracks will expand to the visible range (creases), and even penetrate the packaging layer, causing water and oxygen to invade and leading to pixel failure (black spots);

The "softening catalysis" of dampness and heat: High temperature and humidity (such as 85 ℃/85% RH) will cause polymer materials (such as ACF anisotropic conductive adhesive) to absorb moisture and expand (water absorption rate>3%), reduce modulus (rigidity decreases by 40%~60%), and "soften" the interfacial bonding strength; Meanwhile, the infiltration of water molecules accelerates the electrochemical corrosion of metal wires (such as ITO electrodes), leading to short circuits in the circuit;

The real harm of "dynamic scenes": When users use flexible screens, bending and humidity often "coexist" - for example, when folding phones are used outdoors in summer, the screen heats up due to direct sunlight (>60 ℃), and users frequently open and close it (50-100 times a day). The combination of humidity, humidity, and bending causes the interface to fail three times faster than a single laboratory test.

2、 Shanghai Hexiang One Plan: Three Steps to Overcome the Interaction Problem of "Bending Damp Heat"

The "WK Flex Coupling 1000" flexible screen multi stress coupling testing system independently developed by Shanghai Hexiaoyi combines precision mechanical control, multi field coupling simulation, and artificial intelligence to construct a "test analysis prediction" full chain solution, accurately reproducing real usage scenarios and enabling reliability verification to be "what you see is what you get".

Step 1: Multi stress synchronous simulation - restoring "user's real operation"

Traditional testing equipment, due to technological limitations, cannot achieve "time synchronization and parameter linkage" between bending and humidity. Shanghai Hexiaoyi WK Flex Coupling 1000 has achieved breakthroughs in three core technologies, restoring the complex stress of flexible screens in "folding sliding sweat contact":

Bending wet heat dynamic coupling control:

The device is equipped with a "high-speed pneumatic bending module" (supporting bending with a radius of 0.1~5mm and a frequency of 0.5~2Hz) and a "high-precision temperature and humidity box" (± 0.5 ℃/± 2% RH). The "bending wet heat" timing can be set according to user needs (such as "85 ℃/85% RH for 1 hour → bending with a radius of 1mm 100 times → holding for 2 hours → cycling 5000 times"), simulating the real scene of "daily opening and closing+outdoor exposure+sweat residue" of foldable phones.

Micro nano scale interface monitoring:

Interface failure begins with micrometer level damage (such as interface voids and microcracks), which cannot be observed in real time by traditional optical microscopes. Shanghai Hexiaoyi Innovation integrates confocal laser scanning microscope (CLSM) and infrared thermal imager (IR), which can capture real-time images of interface microstructure evolution (such as packaging adhesive delamination caused by moisture absorption and expansion, metal wire cracks caused by bending stress) at a resolution of 0.1 μ m during the bending wet heat testing process. The data acquisition frequency is up to 100 frames per second, making "invisible failures" unavoidable.

Multi physics field coupling simulation:

Combined with finite element analysis (FEA) software, Shanghai Hexiaoyi can conduct pre simulation on the bending stress distribution of flexible screens (such as the maximum tensile stress point of PI substrates) and wet heat expansion (interlayer stress caused by CTE mismatch), guiding the design of testing parameters (such as determining the most stringent bending radius temperature humidity combination), and avoiding "invalid testing". For example, a folding screen manufacturer found through simulation that "bending radius of 1.5mm+85 ℃/85% RH" is the most prone to failure scenario. After targeted optimization of the packaging adhesive, the bending resistance increased from 50000 times to 200000 times.

Step 2: Deep analysis of failure mechanism - from "phenomenon" to "essence"

The failure of flexible screens may be hidden in the microstructure of the material (such as the degree of curing of the encapsulation adhesive, the dispersion of anisotropic conductive adhesive fillers). Shanghai Hexiaoyi has accurately identified the cause of failure through "microscopic characterization+big data analysis":

Multi dimensional representation technology:

The failed samples were observed for crack morphology by scanning electron microscopy (SEM), analyzed for element diffusion (such as water oxygen permeation pathway) by X-ray energy dispersive spectroscopy (EDS), and molecular chain breakage (such as hydrolysis of urethane bonds in polyurethane encapsulation adhesive) was detected by Fourier transform infrared spectroscopy (FTIR). Combined with differential scanning calorimetry (DSC) to measure the change in material glass transition temperature (Tg), a full chain correlation graph of "material interface failure" was constructed.

AI assisted failure diagnosis:

The "Flexible Screen Failure Database" independently developed by Shanghai Hexiaoyi has collected more than 50000 sets of data (covering failure modes of PI/UTG substrates, OLED packaging adhesives, ACF adhesives and other materials). Through machine learning algorithms (such as Transformer neural networks), it can automatically identify failure types (delamination/cracking/corrosion) and match causes (such as CTE mismatch rate>6ppm/℃, curing temperature less than 80 ℃), with a diagnostic accuracy of ≥ 95%. A certain wearable device manufacturer was once complained about "delamination of packaging adhesive at the wristband bend". Shanghai Hexiaoyi discovered through AI diagnosis that the adhesive layer thickness was uneven (only 5 μ m locally, standard required ≥ 10 μ m). After adjusting the process, the problem was solved.

Step 3: Life prediction and process optimization - from "validation" to "design"

The goal of Shanghai Hexiaoyi is not only to "identify problems", but also to "solve problems". By using the "acceleration factor model+process simulation", we help enterprises optimize material selection and process technology, and improve the reliability of flexible screens

Accelerated life prediction:

Based on physical models (such as Coffin Manson describing thermal fatigue and Peck model describing wet heat aging) and data-driven corrections (such as using LSTM neural network to fit the relationship between bending times, temperature and humidity, and failure time), Shanghai Hexiaoyi can extrapolate laboratory test data to actual service life (such as predicting the failure probability of flexible screens in 5 years/100000 bending times+daily wet heat environment), with an error of ≤ 7%. A certain foldable mobile phone manufacturer adjusted the bending radius based on predicted results (from 1.0mm to 1.5mm), resulting in an 80% decrease in customer complaints about "crease problems" after the product was launched.

Process parameter optimization:

Based on the simulation results, Shanghai Hexiaoyi can provide suggestions for "material selection+process adjustment" (such as recommending UTG glass with low CTE to replace PI substrate, optimizing ACF adhesive coating thickness, and adjusting the curing curve of packaging adhesive), helping enterprises shorten the R&D cycle by 30% (from 9 months to 6 months) and reduce the mass production failure rate by more than 60%.

3、 The 'Industry Value' of Shanghai Hexiaoyi: From Technological Breakthrough to Ecological Co construction

Shanghai Hexiaoyi, with its technological innovation in the field of flexible screen testing, has become a "reliable partner" in the domestic display industry, as reflected in:

1. Standard setters

Shanghai Hexiaoyi led the development of the "Flexible Display Bending Damp Heat Environment Interaction Testing Method" (T/CNEDA 002-2024), which has been included in internal testing standards by panel leaders such as BOE, Huaxing Optoelectronics, and Visionor, as well as terminal brands such as Huawei, Xiaomi, and OPPO, promoting the industry's upgrade from "single stress testing" to "multi stress coupling testing".

2. Domestic substitution drivers

The WK Flex Coupling 1000 independently developed by Shanghai Hexiaoyi has broken the technological monopoly of international companies such as Kikusui from Japan and MTS from the United States (similar imported equipment costs over 15 million yuan, while Shanghai Hexiaoyi's products are only sold for 6 million yuan), helping to increase the localization rate of flexible display testing equipment in China from 15% to 45%.

3. Collaborators in the industrial chain

Shanghai Hexiaoyi has established the "Flexible Display Reliability Alliance" in collaboration with material manufacturers such as Merck and Dongli, panel companies such as BOE and Shentianma, and terminal brands such as Honor and realme, sharing over 1000 failure cases and promoting the "full chain collaborative optimization" of materials, panels, and terminals. For example, a new type of UTG glass was reported by a consortium of companies to be prone to edge cracking during bending. Shanghai Hexiaoyi found through testing and analysis that the stress concentration on the glass surface was the cause, and suggested that the manufacturer adjust the chemical strengthening process. As a result, the yield rate increased from 70% to 92%.

Conclusion: Make flexible screens "fold for a long time and not break when wet"

From foldable phones to car mounted flexible screens, from wearable devices to AR glasses, flexible displays are ushering in a new era of "human-computer interaction". Shanghai Hexiaoyi takes "bending wet heat interaction testing" as a breakthrough point, not only providing accurate testing tools for enterprises, but also promoting the flexible display industry from "usable" to "durable" through technological innovation and ecological co construction.

In the future, Shanghai Hexiaoyi will continue to deeply cultivate the field of display interface science, using more accurate testing, deeper analysis, and more intelligent prediction to "safeguard" the reliability of every flexible screen - because we believe that true technological breakthroughs are not only about making the screen "foldable and bendable", but also about making it "always new" in every user use.

Choose Shanghai Hexiaoyi to turn the "fragility" of flexible screens into "toughness"!