The structural design of hinges is closely related to screen creases, opening and closing feel, structural strength, and service life. From U-shaped solutions to water drop solutions, the advancement of hinge technology has effectively promoted the upgrade of foldable product experience.
The hinge is the core of foldable mobile phones and is closely related to screen creases, opening and closing feel, etc. The folding structure is the most common and creative structure in daily life, making it possible for products to integrate multiple functions into one. Folding structures can be seen everywhere in daily life. Household products such as doors/windows, daily necessities such as makeup boxes, and consumer electronic products such as laptops have cleverly utilized the characteristics of folding structures such as "one-piece multi-purpose" and "space saving" to meet the personalized needs of users. Foldable structures have the following advantages in product design:
1) Effective use of space;
2) Improve product portability;
3) Realize product conversion between different functions;
4) Reduce transportation and storage costs. Therefore, the trend of product structure design towards folding, saving and improving space efficiency is clear, and folding structure has become an important link in product structure design.
Unlike the folding structure of doors, windows, and laptops, foldable screen phones need to carry the screen with them when folding, so the hinge is one of the core components of foldable screen phones. The hinge is the core difference between foldable phones and non-foldable phones. The hinge of a foldable screen phone supports the two planes of the folding part of the phone, and folds the two planes in a natural state. Due to the different bending radius, the outer plane will be longer than the inner plane, but at the same time, the length of the two planes must remain flat after unfolding, which requires the hinge shaft to be able to telescope according to the folding angle. Therefore, the structural design of the hinge is a comprehensive problem that combines mathematics, materials science, physics, industrial design and other disciplines; the design of the hinge structure is closely related to the depth of the screen crease, the feel of folding and opening, the structural strength of the product, and the service life of the product. It is the core technology to solve the "pain points" of foldable screen phones.
From U-shaped to water drop, the advancement of hinge mechanical structure has effectively promoted the upgrade of foldable phone experience. The realization of screen folding in smartphones faces two major challenges. One is to leave as much bending space as possible for the screen, and the other is to avoid the dislocation of the screen and the hinge cover when bending.
First of all, folding the OLED screen directly in half will cause permanent damage, so the "folding screen" does not directly fold the screen 180°, but leaves enough space between the hinge and the body to bend the screen. In addition, in the folded form, the different bending radii of the screen and the hinge cover will cause "misalignment" between the screen and the hinge cover, and the two ends of the screen cannot be aligned with the two ends of the hinge cover, similar to the misalignment between the pages of an ordinary book when it is folded.
Huawei Mate X2 and OPPO Find N released in 2021 provide a more mature water drop hinge solution. Compared with Moto Razr, Huawei Mate X2 and OPPO Find N, which were released in February and December 2021 respectively, have realized a more perfect water drop hinge structure design, which is specifically manifested in:
1) A dual slide rail design is adopted, and a slide rail is also designed on the screen support cover, so that the screen support cover and the slide rail structure are combined together. When the screen is folded, the support plate swings backward to make room for bending. At the same time, the number of slide rails is doubled to ensure the folding accuracy.
2) Add multiple torque modules to the hinge to enhance the damping feeling of folding and opening. The torque module structure includes two upper and lower camshafts, springs and gears. The rotation of the screen will drive the upper camshaft to rotate. At the same time, the spring applies pressure, and the friction between the camshafts forms a damping feeling, making the opening and closing feel tighter. In addition, the gears are responsible for the precise bite at multiple angles to achieve multi-angle hovering when folding.
The water drop hinge designs of Huawei Mate X2 and OPPO Find N are also different, as shown in:
1) The water drop of Huawei Mate X2 is rounded, and the stress points are mainly concentrated in the head, while the tail is less stressed, so the crease is mainly concentrated in the middle of the screen; OPPO Find N widens the stress in the tail area, and the stress changes in the head and tail are more coherent, so the crease is wider but shallower;
2) The etching area in the middle of the OPPO Find N screen support cover is larger and does not stick to the screen. When bending, the deformation of the support cover will not involve the screen, effectively reducing the crease;
3) In the hinge frame, Huawei Mate X2 only has two upper and lower torque modules, while OPPO Find N has three upper, middle and lower torque modules. At the same time, the size of the cam, spring and gear of the single torque module of OPPO Find N is larger, achieving a better opening and closing feel and multi-angle hovering effect.
It can be seen that the hinge is one of the core components of foldable screen mobile phones, and the progress of hinge mechanical structure design has effectively promoted the experience upgrade of foldable screen mobile phones. On the whole, the water drop hinge with double slide rail design can effectively control the crease, and the screen can be completely closed when folded. At the same time, it has a good opening and closing feel, providing users with a better user experience.
The market size of foldable screen mobile phone hinges is expected to reach 18.754 billion yuan in 2026.
The hinge (hinge) products used in consumer electronic products such as smartphones and PCs are designed through mechanical structural parts and are assembled from stamping parts, car parts, MIM parts, die-casting parts, and common parts. Therefore, suppliers of stamping parts, MIM parts, die-casting parts and other parts are upstream suppliers of the NB/tablet/mobile phone hinge (hinge) industry chain; the assemblers of hinges (hinges) are in the middle of the industry chain. Generally, hinge (hinge) products require the collaborative design and development of midstream assemblers and downstream NB/tablet/mobile phone customers to produce finished products that meet the customer's requirements for tolerance, torque and life test.
MIM (metal injection molding) is the core component process for hinge manufacturing.
Powder injection molding is a branch of metallurgy and material science. This process mainly uses metal powder (including a small amount of non-metallic powder mixed in) as raw materials, and uses the "forming + sintering" method to manufacture materials and products. It is a near-net forming process for producing complex parts at a lower cost. According to the classification of materials, powder injection molding can be divided into two categories: MIM (Metal Injection Molding) and CIM (Ceramic Injection Molding). There are many process links required to complete the production of MIM products. The key links and core technologies of MIM process are mainly concentrated in injection, degreasing, sintering and other process links.
MIM process has obvious advantages in manufacturing high-complexity, high-precision, high-strength and exquisitely-looking precision structural parts and appearance parts.
MIM process is widely used in consumer electronics, automobiles, medical equipment, tools and other fields; in the consumer electronics industry, MIM products can be used in mobile phone metal card trays, volume buttons, mobile phone interfaces, camera frames, hinges, lifting camera precision parts, multi-camera precision parts, gears and other fields.
Considering that folding screen mobile phones need to be 14mm or even thinner, and the hinges have complex and high-precision mechanical structures, combined with the advantages of MIM process in the field of complex 3D modeling and high-precision products, we believe that MIM process has broad development space in the folding screen mobile phone market.
Aluminum structural parts materials can be used in the fields of folding screen mobile phone middle frames, card trays, hinges and other fields.
Aluminum structural parts have the advantages of good heat dissipation, strong resistance to compression and bending, and resistance to scratches. Consumer electronic products such as mobile phones and tablets using aluminum structural parts are more stylish and beautiful, thinner and have better texture. As folding screen mobile phones develop towards lightweight and thinness, the demand for aluminum alloy materials will gradually increase; since 2021, under the leadership of Samsung, the leader of folding screen mobile phones, many brands of new product projects will use 7 series aluminum alloy materials.
Liquid metal (amorphous alloy) as a metal material with excellent performance can be used in folding screen mobile phone hinges. Liquid metal, also known as amorphous alloy, refers to a metal in a non-crystalline state that is different from the periodicity and symmetry of the atomic arrangement of metal materials under normal circumstances. The long-range disordered structure of amorphous alloy materials gives them special properties, such as high strength, high hardness, high finish, corrosion resistance and wear resistance, etc. Its bending strength, tensile strength, elastic deformation, etc. are better than common materials.
Liquid metal has the characteristics of high strength, good formability and high dimensional accuracy, which can meet the requirements of thickness, strength and accuracy of folding screen hinge structural parts. At the same time, liquid metal has excellent elastic deformation ability, which makes the fatigue performance of the product better than other materials. Huawei's Mate X2 launched in February 2021 and P50 Pocket launched in December 2021 use zirconium-based liquid metal as hinge material for folding screen mobile phones, achieving seamless folding and ensuring the flatness of the screen after unfolding.
Suppliers of folding screen hinge assembly, MIM, aluminum alloy materials, and liquid metal are mainly concentrated in China and South Korea. At present, suppliers of folding screen hinge assembly include KH Vatec, S-Connect, AU Flex in South Korea, Jingyan Technology, Kosen Technology, Changying Precision, Zhaoli, Fushida, etc. in China.
The main suppliers of MIM parts for folding screen hinges are China's Jingyan Technology, Dongmu Co., Ltd., Xinwei Communication, and Xinrixing; the main suppliers of hinge aluminum alloy materials are China's Furong Technology; the main suppliers of hinge liquid metals are China's Yian Technology and Changzhou Shijing. Due to the complex structure of folding screen hinges, folding screen mobile phone brand manufacturers such as Samsung and Huawei have many design patents; in addition, Amphenol, an American company, as one of the world's leading connector manufacturers, has the ability to provide integrated solutions for folding screen hinges.
The global market size of folding screen mobile phone hinges and MIM parts is expected to grow rapidly. We estimate that the global folding screen mobile phone hinge market size will be 1.267 billion yuan in 2021, and is expected to increase by 136.8% year-on-year to 2.999 billion yuan in 2022, and is expected to grow to 18.754 billion yuan in 2026 (CAGR: 71.4%). We estimate that the global market size of foldable phone hinge MIM parts will be 317 million yuan in 2021, and is expected to grow by 152.9% year-on-year to 802 million yuan in 2022, and is expected to grow to 6.165 billion yuan in 2026 (CAGR: 81.0%).