A method for manufacturing a stretchable and curved electronic product and the product

Abstract

The application discloses a manufacturing method and product of stretchable and curved surface electronic products, and the manufacturing method comprises the following steps: preparing matrix circuits on a flexible circuit board; cutting the flexible circuit board to form a folding area between two adjacent matrix circuits; encapsulating LED chips and the flexible circuit board; folding the flexible circuit board along the folding area; and encapsulating the folding area. The application uses the folding area to replace the rigid node connection rotating unit and combines with rigid functional devices to manufacture self-adapting curved surface electronic products, the folding area overcomes the problems of stress concentration on the rigid node and the inability to lay circuit, and the neutral position of the folding area allows the expansion structure to stretch and compress.

Description

Technical Field

[0001] This invention belongs to the field of electronic product manufacturing technology, specifically relating to a method and product for manufacturing stretchable and curved electronic products. Background Technology

[0002] Stretchable and curved electronics offer high spatial adaptability, allowing their shape to be adjusted to fit various objects. They are widely used in conformal circuits, wearable sensors, curved optoelectronics, artificial smart skin, and curved displays, among others. To expand the application of electronics in curved objects and wearable devices, electronics manufacturing technology has evolved towards greater conformality, significantly improving manufacturing processes. However, most electronic devices and sensors are manufactured on two-dimensional substrates. While rigid or brittle substrates are satisfactory in many applications across various fields, they are inherently incompatible with complex curved surfaces, such as for animal health monitoring and treatment, integrating conformal antennas / circuits on irregular curved surfaces, or large-area adaptive curved displays.

[0003] Gauss's Egregium Theorem proves the constancy of the Gaussian curvature (GC, K) of an unstretched surface under locally isometric transformations. Therefore, stretchability is indispensable for realizing curved electronic devices. For decades, researchers have developed various conformal manufacturing processes to overcome the limitations of traditional semiconductor technology in directly fabricating stretchable materials or structures. Based on the required functional structure or deformability of the curved electronic device, conformal manufacturing techniques can be broadly classified into two categories: those based on planar structures and then geometrically transformed into the shape required for the curved electronic device, and those that directly fabricate or assemble materials, devices, structures, and components on the target curved surface.

[0004] Geometric transformation methods first fabricate electronic devices on a planar substrate, then spontaneously or artificially transfer the original planar substrate to a target curved surface through external stimuli such as pressure, temperature, light, magnetism, and electricity, or directly deform the planar substrate into a curved surface (bending or rolling), thereby realizing the fabrication of curved electronic products. Taking typical curved optoelectronic devices or curved displays as examples, a common approach is to mount or embed rigid devices into an elastic substrate, or connect island-type small devices with stretchable link structures, and then manually transfer the devices to the target curved surface. However, due to the low stiffness and short fatigue life of stretchable materials (such as polydimethylsiloxane (PDMS), Eco-flex, dragonskin, PEDOT, etc.), the light-emitting or conductive materials embedded in them are easily damaged under high pressure. Another feasible solution for manufacturing curved electronic products is to connect island-type rigid light-emitting components with geometrically stretchable links. Inspired by the eyes of arthropods, Song et al. developed a curved digital imaging system based on serpentine links. Rogers et al. developed a technique using serpentine links to connect micro-LED pixel arrays, which were then transferred to a pre-stretched 400-micrometer-thick PDMS slice, achieving a biaxial stretchability of 48%. However, such stretchable link-based electronics typically rely on elastic materials as substrates, resulting in limitations similar to those described above. Furthermore, stretchable links exhibit drawbacks such as structural complexity, manufacturing difficulty, and high cost, hindering large-scale production.

[0005] Unlike geometric transformation methods, direct manufacturing methods, including surface lithography, inkjet printing, 3D printing, and laser direct writing, exhibit unique and irreplaceable advantages. Surface lithography can be well applied to high-resolution curved surfaces, but it presents challenges in deposition, etching, or material growth / doping on large-area curved surfaces. Therefore, when high precision requirements or simple electronic structures are not necessary, directly fabricating electronic devices on arbitrary surfaces via conformal inkjet printing, 3D printing, or laser direct writing is ideal, but not suitable for large-scale production of inexpensive products. Summary of the Invention

[0006] To overcome the aforementioned technical deficiencies, the first aspect of this invention provides a method for manufacturing stretchable and curved electronic products, comprising the steps of:

[0007] Constructing a matrix circuit on a flexible circuit board;

[0008] The flexible circuit board is pre-processed to form a folded area between two adjacent matrix circuits;

[0009] Fold the flexible circuit board along the folding area;

[0010] The folded area is encapsulated.

[0011] As a further improvement of the present invention, the folding area includes: a fence section, a cutting section, and a preset crease section;

[0012] The fence segment is arranged around the matrix circuit;

[0013] The contact point between the fence section and the matrix circuit is the preset crease section;

[0014] The cut segment is located on one of the extension lines of the preset crease, and the cut segment is located beside the preset crease.

[0015] As a further improvement of the present invention, one end of the folded area is flush with one side edge of the matrix circuit, and the other end of the folded area is flush with one side edge of another matrix circuit, wherein one side edge of the matrix circuit and one side edge of the other matrix circuit are two sides that are far apart from each other.

[0016] As a further improvement of the present invention, the matrix circuits are connected by metal circuits on the two surfaces of the flexible circuit board, and the step of pre-processing the flexible circuit board includes:

[0017] Solder resist is applied to the surface of a flexible circuit board, the surface including: the remaining area after removing the matrix circuit and the metal circuit;

[0018] The cut segment is laser-cut.

[0019] As a further improvement of the present invention, SMT is used to package the LED chip.

[0020] As a further improvement of the present invention, the flexible circuit board is folded along the folding area by means of mold group guidance, so that the fence segment is perpendicular to the matrix circuit.

[0021] As a further improvement of the present invention, the mold assembly includes: a first mold, a second mold, and a third mold arranged sequentially from top to bottom;

[0022] The first mold is provided with a first push plate that matches the matrix circuit;

[0023] The second mold is provided with several pressure plates, the shape and position of which match the folding area;

[0024] The third mold is equipped with a second push plate that matches the matrix circuit.

[0025] As a further improvement of the present invention, the step of folding the flexible circuit board along the folding area by means of mold group guidance includes:

[0026] The flexible circuit is placed on the second mold, and the folded area is placed on the pressure plate;

[0027] The first push plate is aligned with the matrix circuit and pressed towards the direction of the third mold, causing the preset crease segment to fold, and the fence segment to be perpendicular to the matrix circuit.

[0028] The second pusher plate is aligned with the matrix circuit, and the third mold pushes the flexible circuit board upward.

[0029] A second aspect of the present invention provides a stretchable and curved electronic product, manufactured by the above-described manufacturing method, comprising a plurality of interconnected LED devices;

[0030] The LED device includes: a functional area and a fence;

[0031] LED chip circuits are soldered onto the functional area;

[0032] The fence surrounds the functional area, and the fence extends in one direction to form a connecting part;

[0033] Several of the LED devices are connected via the connecting part.

[0034] As a further improvement of the present invention, the LED chip circuit is covered with epoxy resin to connect the LED chip to the fence.

[0035] Compared with the prior art, the present invention has the following advantages: by replacing rigid nodes with folded areas to connect rotating units and combining them with rigid functional devices to manufacture adaptive curved electronic products, the folded areas overcome the problems of stress concentration and inability to lay circuits on rigid nodes, and the neutral position of their folding allows the expansion structure to stretch and compress. Attached Figure Description

[0036] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, wherein:

[0037] Figure 1 This is a flowchart of the manufacturing method described in this invention;

[0038] Figure 2 This is an exploded view of the flexible circuit board and metal circuit described in this invention.

[0039] Figure 3 This is a schematic diagram of the structure of the flexible circuit board described in this invention;

[0040] Figure 4 This is a schematic diagram of the manufacturing process of step S4 of the present invention. Figure 1 ;

[0041] Figure 5 This is a schematic diagram of the manufacturing process of step S4 of the present invention. Figure 2 ;

[0042] Figure 6 This is a schematic diagram of the manufacturing process of step S4 of the present invention. Figure 3 ;

[0043] Figure 7 This is a schematic diagram of the structure of the electronic product described in this invention;

[0044] Figure 8 This is a rendering of the electronic product described in this invention installed on a cylindrical surface;

[0045] Figure 9 This is a rendering of the electronic product described in this invention installed on a spherical surface.

[0046] Figure 10 This is a rendering of the electronic product described in this invention mounted on any surface;

[0047] Figure 11 This is a rendering of the electronic product described in this invention installed on a saddle surface;

[0048] Figure 12 This is a schematic diagram of the LED device described in this invention.

[0049] Explanation of reference numerals in the attached figures:

[0050] 1. Flexible circuit board; 11. Polyimide film; 12. Functional area; 13. Solder resist; 14. Metal circuit; 2. LED chip; 3. Folding area; 31. Fence section; 311. Fence; 312. Connecting part; 32. Cutting section; 33. Pre-set crease section; 4. First mold; 41. First push plate; 5. Second mold; 51. Pressure plate; 6. Third mold; 61. Second push plate; 7. Epoxy resin;

[0051] 101. Dispensing machine; 102. Ultraviolet light. Detailed Implementation

[0052] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0053] This invention provides a method for manufacturing stretchable and curved electronic products, such as... Figure 1 As shown, the steps include:

[0054] S1. Construct a matrix circuit on the flexible circuit board 1, such as... Figure 2 and Figure 3As shown, the flexible circuit board 1 includes a polyimide film 11. The polyimide film 11 is pre-divided so that its upper surface has a matrix distribution of several functional areas 12. A 40x40mil LED chip 2 is encapsulated on a 17µm epoxy resin 7 solder resist film and disposed on the functional areas 12. Two 12µm thick metal circuits 14 are formed on two different surfaces of the 30µm polyimide film 11. Through the metal circuits 14, multiple LED chips 2 are electrically connected. The metal circuits 14 are also used for connection with external circuits. The bottom solder resist 13 is used to protect the remaining area of ​​the flexible circuit board 1. At the same time, the positions of the top solder resist 13 correspond one-to-one with the positions of the bottom solder resist 13.

[0055] S2, such as Figure 3 As shown, the flexible circuit board 1 is pre-processed to form a folded area 3 between two adjacent matrix circuits. The folded area 3 includes: a fence segment 311, a cutting segment 32, and a preset crease segment 33. The fence segment 311 surrounds the matrix circuit. The contact point between the fence segment 311 and the matrix circuit is the preset crease segment 33. The cutting segment 32 is located on one extension line of the preset crease and is located on the side of the preset crease.

[0056] One end of the folded region 3 is flush with one side edge of the matrix circuit, and the other end of the folded region 3 is flush with one side edge of another matrix circuit. The side edge of the matrix circuit and the side edge of the other matrix circuit are two sides that are far apart from each other.

[0057] The pretreatment process includes: applying a top solder resist 13 to the remaining area on the upper surface of the polyimide film 11 (i.e., the area excluding the functional area 12 and the metal circuit 14) to protect the remaining area of ​​the flexible circuit board 1 and enhance its rigidity. This creates a pre-defined crease segment 33 at the connection between the top solder resist 13 and the LED chip 2, making it easier to fold. The exposed creases are then more easily folded. The cutting segment 32 is obtained using laser cutting.

[0058] S3. Fold the flexible circuit board 1 along the folding area 3.

[0059] To achieve rapid folding of the flexible circuit board 1, this invention designs a mold assembly. The flexible circuit board 1 is folded along the folding area 3 by the mold assembly, so that the fence segment 311 is perpendicular to the matrix circuit. The mold assembly includes: a first mold 4, a second mold 5, and a third mold 6 arranged sequentially from top to bottom; the first mold 4 is provided with a first push plate 41 matching the matrix circuit; the second mold 5 is provided with several pressure plates 51, the shape and position of which match the folding area 3; the third mold 6 is provided with a second push plate 61 matching the matrix circuit.

[0060] The steps of folding the flexible circuit board 1 along the folding area 3 by means of mold group guidance include:

[0061] S31. Place the flexible circuit on the second mold 5 and place the folded area 3 on the pressure plate 51.

[0062] S32, such as Figure 4 , Figure 5 As shown, the first push plate 41 is aligned with the matrix circuit and pressed towards the third mold 6, causing the preset crease segment 33 to fold, and the fence segment 311 31 is perpendicular to the matrix circuit.

[0063] S33, such as Figure 6 As shown, the second pusher plate 61 is aligned with the matrix circuit, and the third mold 6 pushes the flexible circuit board 1 upward.

[0064] After folding, the fence segment 311 is flipped along the direction of the LED chip 2. At this time, the fence segment 311 is divided into a fence 311 that surrounds the LED chip 2 and a link 312 that is connected to the fence 311. The link 312 is located in one of the extension directions of the fence 311 and is used to connect two adjacent LED chips 2.

[0065] S4. Encapsulate the folded area 3 by using a dispensing machine 101 to fill the area above the LED chip 2 (i.e., within the fence 311 area) with epoxy resin 7, and then use ultraviolet light to dry the epoxy resin 7, so that the fence and epoxy resin are bonded together and vertically surround the LED chip. It should be noted that the encapsulation step of the folded area 3 can be performed simultaneously with step S42, or it can be performed separately after all the folded areas have been folded.

[0066] Through the above steps, as Figure 7 As shown, a stretchable and curved electronic product is obtained. The performance of this invention is tested using an electronic product composed of 400 pixels (i.e., containing 400 matrix circuits). This electronic product is used as a curved display. The curved display is matched with cylinders, spheres, saddle surfaces, and arbitrary surfaces respectively, verifying the compatibility and working performance of the curved display with different curved surfaces. Figure 8 As shown in Figure a, the display is mounted on a cylindrical mold with a radius of 5 cm. The first principal curvature (k1 = 0.2 cm⁻¹) and the second principal curvature (k2 = 0) are represented by the red and blue envelopes, respectively. Figure 8 As can be seen in b, since the cylinder is a developable surface, the pixel spacing does not need to be changed, resulting in a uniform arrangement. In contrast, the pixels on the sphere and the saddle surface are arranged through stretching and contraction. The envelope curvature at the vertex of the sphere (k1=k2=0.2cm⁻¹) and the saddle point of the saddle surface (k1=-k2=0.2cm⁻¹) (e.g.) Figure 9 (as shown in a and 10a) is consistent with the shape. The Gaussian curvature of any surface varies with the undulating shape (as shown in a and 10a). Figure 11 a) The layout of pixels also expands and contracts accordingly. Figure 11 b). A passive line scanning control system consisting of a shift register (74HC595) circuit drives the curved display. Optical images show the display's state at different angles and fields of view during operation. Figure 8 c, 9c, and 10c display the letter pattern "ust". Figure 11 c displays the word "HELLO". Results show that the curved display has considerable stretchability (from compressed to stretched), and due to the distortion of the fence 311 and the link 312, the display can achieve spatial concave-convex deformation, thereby adaptively matching surfaces with different Gaussian curvatures. Specifically, the distortion of the link 312 refers to twisting, which occurs when subjected to opposite torques. The two ends of the link 312 twist in opposite directions, forming a spiral shape. When used to adapt to curved surfaces (such as spheres), the link 312, because the material itself cannot be stretched or compressed, will twist to conform to the surface. In this case, the glued portion of the link 312 remains vertical, while the flexible middle section will droop down to fit closer to the surface.

[0067] Meanwhile, the present invention provides a stretchable and curved electronic product, manufactured by the aforementioned manufacturing method, comprising a plurality of interconnected LED devices; the LED devices include: a functional area 12 and a fence 311; an LED chip 2 circuit is soldered on the functional area 12; the fence 311 surrounds the functional area 12, and the fence 311 extends in one direction to form a connecting portion 312. The LED chip circuit includes: an LED chip 2 and its metal circuit 14, the metal circuit 14 can be laid on two surfaces of the functional area 12, the fence 311, and two sides of the connecting portion 312; the plurality of LED devices are connected through the connecting portion 312 and the metal circuit 14.

[0068] Furthermore, the LED chip 2 circuit is covered with epoxy resin 7 to connect the LED chip 2 to the fence 311.

[0069] For details on the implementation process and beneficial effects of stretchable and curved electronic products, please refer to the previous text, which will not be repeated here.

[0070] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for manufacturing stretchable and curved electronic products, characterized in that, Including the following steps: Constructing a matrix circuit on a flexible circuit board; The flexible circuit board is pre-processed to form a folded area between two adjacent matrix circuits; Fold the flexible circuit board along the folding area; Encapsulate the folded area; The folding area includes: a fence section, a cutting section, and a pre-set crease section; The fence segment is arranged around the matrix circuit; The contact point between the fence section and the matrix circuit is the preset crease section; The cut segment is located on one of the extension lines of the preset crease, and the cut segment is located beside the preset crease.

2. The manufacturing method according to claim 1, characterized in that, One end of the folded area is flush with one side edge of the matrix circuit, and the other end of the folded area is flush with one side edge of another matrix circuit, wherein one side edge of the matrix circuit and one side edge of the other matrix circuit are two sides that are far apart from each other.

3. The manufacturing method according to claim 1, characterized in that, The matrix circuits are connected by metal circuits on both surfaces of the flexible circuit board. The preprocessing step of the flexible circuit board includes: Solder resist is applied to the surface of a flexible circuit board, the surface including: the remaining area after removing the matrix circuit and the metal circuit; The cut segment is laser-cut.

4. The manufacturing method according to claim 1, characterized in that, SMT is used to package LED chips.

5. The manufacturing method according to claim 1, characterized in that, The flexible circuit board is folded along the folding area by means of a mold group, so that the fence segment is perpendicular to the matrix circuit.

6. The manufacturing method according to claim 5, characterized in that, The mold assembly includes: a first mold, a second mold, and a third mold arranged sequentially from top to bottom; The first mold is provided with a first push plate that matches the matrix circuit; The second mold is provided with several pressure plates, the shape and position of which match the folding area; The third mold is equipped with a second push plate that matches the matrix circuit.

7. The manufacturing method according to claim 6, characterized in that, The step of folding the flexible circuit board along the folding area by means of a mold group includes: The flexible circuit is placed on the second mold, and the folded area is placed on the pressure plate; The first push plate is aligned with the matrix circuit and pressed towards the direction of the third mold, causing the preset crease segment to fold, and the fence segment to be perpendicular to the matrix circuit. The second pusher plate is aligned with the matrix circuit, and the third mold pushes the flexible circuit board upward.

8. A stretchable and curved electronic product, characterized in that, The device is manufactured by the manufacturing method according to any one of claims 1 to 7 and comprises a plurality of interconnected LED devices. The LED device includes: a functional area and a fence; LED chip circuits are soldered onto the functional area; The fence surrounds the functional area, and the fence extends in one direction to form a connecting part; Several of the LED devices are connected via the connecting part.

9. The stretchable and curved electronic product according to claim 8, characterized in that, The LED chip circuit is covered with epoxy resin to connect the LED chip to the fence.

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