Thin stretchable flexible circuit board and method of making same

Abstract

The application discloses a thin stretchable flexible circuit board and a manufacturing method thereof. The method comprises the following steps: adhering a tack-reducing protective film to a first side of a flexible circuit substrate with a circuit layer and two protective film layers to form a first circuit substrate; the tack-reducing protective film has a first preset adhesion; the first circuit substrate is cut to form a meandering circuit, and waste tearing is performed to form a second circuit substrate; a first elastomer composite film is adhered to a second side of the second circuit substrate, and tack-reducing operation is performed on the tack-reducing protective film, so that the tack-reducing protective film has a second preset adhesion, and a third circuit substrate is formed; the second preset adhesion is smaller than the first preset adhesion; the tack-reducing protective film is torn from the third circuit substrate to form a target circuit board. The application can improve the yield of mass-produced products based on the tack-reducing protective film, and can also encapsulate the meandering circuit based on the elasticity of the composite structure of the polymer film, and adapt to different pressing processes to realize lightness, thinness and miniaturization.

Description

Technical Field

[0001] This invention relates to the field of flexible circuit board manufacturing, specifically to a thin, stretchable flexible circuit board and its manufacturing method. Background Technology

[0002] As an emerging technology, flexible and stretchable electronics are gaining popularity and widespread application due to their ability to be compressed, twisted, and conformed to complex non-planar surfaces. Currently, wearable electronics applications are positively impacting all aspects of daily life, driving economic growth and the rapid development of stretchable electronic devices and related manufacturing technologies. The flexible, soft, and stretchable forms of electronic devices enable next-generation wearable electronics applications, opening up various applications for healthcare, energy, and military purposes.

[0003] A crucial component of flexible and stretchable electronic products is the stretchable conductor circuitry, ensuring both stretchability and the ability to transmit signals and power. Currently, there are many methods for manufacturing stretchable conductor circuitry. One mainstream method involves creating flexible, elongated wires from metal conductors such as copper or aluminum, then encapsulating them in a highly elastic polymer (also known as an elastomer). This method requires pre-fabricating the stretchable circuitry on a carrier film, then bonding it to the elastomer before peeling off the carrier film. To ensure high yield rates in mass production, the bonding strength between the carrier film and the stretchable circuitry needs to be high before bonding to the elastomer to prevent separation during the removal (peeling) of unwanted waste areas. After bonding, the bonding strength must be sufficiently low to allow for peeling off the carrier film while maintaining the continuity of the circuitry. However, this current mass production method is challenging, resulting in low yield rates for mass-produced products.

[0004] On the other hand, the method of combining meandering lines with elastomers currently usually involves casting. However, this method requires the design of complex molds, and the resulting stretchable conductor lines are relatively thick, typically greater than 1 mm, which is not conducive to the miniaturization and lightness of flexible and stretchable electronic products. Summary of the Invention

[0005] In view of this, the present invention provides a thin, stretchable flexible circuit board and a method for manufacturing the same, in order to solve the problems of low mass production yield and large circuit thickness in existing stretchable circuit boards, which are not conducive to the thinning and miniaturization of products.

[0006] This invention provides a method for manufacturing a thin, stretchable, flexible circuit board, comprising:

[0007] A flexible circuit board with a circuit layer and two protective film layers is provided. A non-adhesive protective film is laminated to a first side of the flexible circuit board to form a first circuit board. The two protective film layers are respectively located on both sides of the circuit layer. The non-adhesive protective film has a first preset adhesion force.

[0008] From the second side of the first circuit board, the two protective film layers in the first circuit board are cut to form a meandering circuit, and the cut first circuit board is then ripped to remove waste material, forming a second circuit board; wherein the meandering circuit has at least one stretching direction.

[0009] A first elastomeric composite film is provided, the first elastomeric composite film is adhered to the second side of the second circuit substrate, and the anti-adhesion protective film on the first side of the second circuit substrate is subjected to an anti-adhesion operation, so that the anti-adhesion protective film has a second preset adhesion force, thereby forming a third circuit substrate; wherein, the second preset adhesion force is less than the first preset adhesion force.

[0010] The anti-adhesion protective film is peeled off the third circuit board to form the target circuit board.

[0011] Optionally, the anti-adhesion protective film includes either a UV anti-adhesion film or a thermal anti-adhesion film.

[0012] Optionally, when the anti-adhesion protective film is the UV anti-adhesion film, the anti-adhesion operation on the anti-adhesion protective film on the first side of the second circuit substrate includes:

[0013] The anti-adhesion protective film on the first side of the second circuit board is subjected to UV irradiation;

[0014] When the anti-adhesion protective film is the heat-resistant anti-adhesion film, the anti-adhesion operation on the anti-adhesion protective film on the first side of the second circuit substrate includes:

[0015] The anti-adhesion protective film on the first side of the second circuit board is heated.

[0016] Optionally, the first preset adhesive force is greater than 500 gf / inch, and the second preset adhesive force is less than 100 gf / inch.

[0017] Optionally, the first elastomeric composite film includes a first polymer film layer having a first melting point and a second polymer film layer having a second melting point, wherein the second polymer film layer is disposed on one side of the first polymer film layer; wherein the first melting point is lower than the second melting point.

[0018] Optionally, the provision of a first elastomeric composite film, the bonding of the first elastomeric composite film to a second side of the second circuit substrate, and the de-adhesion protective film on the first side of the second circuit substrate are subjected to a de-adhesion operation, so that the de-adhesion protective film has a second preset adhesion force to form a third circuit substrate, includes:

[0019] The adhesive-reducing protective film on the first side of the second circuit board is subjected to an adhesive-reducing operation, so that the adhesive-reducing protective film has the second preset adhesive force;

[0020] Provide the first elastomer composite film;

[0021] The first side of the first elastomer composite film with the first polymer film layer is attached to the second side of the second circuit substrate after the de-adhesion operation to form the third circuit substrate.

[0022] Optionally, the provision of a first elastomeric composite film, the bonding of the first elastomeric composite film to a second side of the second circuit substrate, and the de-adhesion protective film on the first side of the second circuit substrate are subjected to a de-adhesion operation, so that the de-adhesion protective film has a second preset adhesion force to form a third circuit substrate, includes:

[0023] Provide the first elastomer composite film;

[0024] The side of the first elastomer composite film having the first polymer film layer is attached to the second side of the second circuit substrate.

[0025] The adhesive-reducing protective film on the first side of the second circuit board is subjected to an adhesive-reducing operation, so that the adhesive-reducing protective film has the second preset adhesive force, thereby forming the third circuit board.

[0026] Optionally, after peeling off the anti-adhesion protective film from the third circuit board, the process further includes:

[0027] A second elastomeric composite film identical to the first elastomeric composite film is provided;

[0028] The side of the second elastomer composite film with the first polymer film layer is attached to the first side of the third circuit board after the anti-adhesion protective film is peeled off.

[0029] Optionally, the difference between the second melting point and the first melting point is in the range of 20 to 100°C.

[0030] Optionally, the difference between the second melting point and the first melting point is in the range of 30 to 60°C.

[0031] Optionally, the thickness of the first polymer film layer ranges from 30 to 100 μm, and / or the thickness of the second polymer film layer ranges from 25 to 150 μm.

[0032] Optionally, the meandering route includes:

[0033] Substrate layer;

[0034] At least one conductive layer is laminated to one or both sides of the substrate layer; and

[0035] Two protective film layers, cut to their respective shapes, are bonded to the outermost conductor layer or the substrate layer using adhesive layers.

[0036] Optionally, each of the aforementioned conductor layers contains one or more conductors.

[0037] In addition, the present invention also provides a thin, stretchable flexible circuit board, which is manufactured using the aforementioned manufacturing method.

[0038] The beneficial effects of this invention are as follows: Since the circuit layer and two protective film layers are present, when forming a meandering circuit, it is necessary to cut the two protective film layers to make the circuit layer a stretchable meandering circuit. Furthermore, a first elastomer composite film needs to be bonded after the meandering circuit is formed. Therefore, a non-adhesive protective film is bonded to the first side of the flexible circuit substrate with the circuit layer and two protective film layers. This non-adhesive protective film can serve as a carrier film during the formation of the meandering circuit, providing support for the entire first circuit substrate during cutting, thus facilitating better fabrication of the meandering circuit. It also provides support during subsequent waste removal and bonding of the first elastomer composite film to form a thin, stretchable flexible circuit board. This non-adhesive protective film has non-adhesive properties, meaning that adhesion can be reduced through certain non-adhesive operations (i.e., reducing adhesive force). Therefore, after the meandering circuit is fabricated, the subsequent... When removing waste material, the strong adhesion before the de-adhesion operation ensures a strong bond between the winding circuit and the de-adhesion protective film, guaranteeing that the winding circuit will separate from the de-adhesion protective film during waste removal. Then, after bonding the first elastomer composite film, the weaker adhesion after the de-adhesion operation ensures that the de-adhesion protective film can be easily peeled off while preventing the winding circuit from separating from the first elastomer composite film. This enables mass production of stretchable flexible circuit boards and improves production yield. Furthermore, the first elastomer composite film has a composite structure with multiple polymer films, which can encapsulate the winding circuit based on the elasticity of the polymer films and adapt to different lamination processes by utilizing the characteristics of different polymer films. This facilitates the reduction of the thickness of the stretchable flexible circuit board, enabling the thinning and miniaturization of flexible stretchable electronic products. Attached Figure Description

[0039] The features and advantages of the invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the invention in any way. In the drawings:

[0040] Figure 1 A flowchart of a method for manufacturing a thin, stretchable, flexible circuit board according to Embodiment 1 of the present invention is shown;

[0041] Figure 2A and Figure 2B The cross-sectional structural diagrams of the first circuit board in Embodiment 1 of the present invention before and after external cutting are shown respectively.

[0042] Figure 3 A cross-sectional structural diagram of the meandering line in Embodiment 1 of the present invention is shown;

[0043] Figure 4 A schematic diagram of a U-shaped meandering route in Embodiment 1 of the present invention is shown;

[0044] Figure 5 A schematic diagram of a horseshoe-shaped meandering route in Embodiment 1 of the present invention is shown;

[0045] Figure 6 This shows a top view of the circuit layer after it has been fabricated into a meandering circuit according to Embodiment 1 of the present invention.

[0046] Figure 7 A cross-sectional view of the first elastomeric composite film in Embodiment 1 of the present invention is shown.

[0047] Figure 8 This shows a front view structural diagram of the target circuit board in Embodiment 1 of the present invention;

[0048] Figure 9 A cross-sectional view of the target circuit board in Embodiment 1 of the present invention is shown.

[0049] The labels in the attached figures are explained as follows:

[0050] 1. Flexible board; 2. First elastomer composite film; 3. Second elastomer composite film; 11. Winding line; 12. Transition zone; 13. Non-stretchable zone; 111. Substrate layer; 112. Conductor layer; 113. Protective film layer; 114. Adhesive layer; 21. First polymer film layer; 22. Second polymer film layer; 4. Anti-adhesion protective film. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Example 1

[0053] This embodiment provides a method for manufacturing a thin, stretchable, flexible circuit board, such as... Figure 1 As shown, it includes:

[0054] S1: A flexible circuit board with a circuit layer and two protective film layers is provided. A non-adhesive protective film is attached to a first side of the flexible circuit board to form a first circuit board. The two protective film layers are respectively located on both sides of the circuit layer. The non-adhesive protective film has a first preset adhesion force.

[0055] S2: From the second side of the first circuit substrate, cut the two protective film layers in the first circuit substrate so that the circuit layer and the cut two protective film layers form a meandering circuit, and tear off the waste material from the cut first circuit substrate to form a second circuit substrate; wherein the meandering circuit has at least one stretching direction.

[0056] S3: Provide a first elastomeric composite film, attach the first elastomeric composite film to the second side of the second circuit substrate, and perform an anti-adhesion operation on the anti-adhesion protective film on the first side of the second circuit substrate, so that the anti-adhesion protective film has a second preset adhesion force, forming a third circuit substrate; wherein, the second preset adhesion force is less than the first preset adhesion force.

[0057] S4: Peel off the anti-adhesion protective film from the third circuit board to form the target circuit board.

[0058] In this embodiment, since the circuit board has a circuit layer and two protective film layers, when forming the meandering circuit, it is necessary to cut the two protective film layers to make the circuit layer into a stretchable meandering circuit. Furthermore, it is necessary to laminate the first elastomer composite film after forming the meandering circuit. Therefore, a non-adhesive protective film is laminated to the first side of the flexible circuit board with the circuit layer and two protective film layers. This non-adhesive protective film serves as a carrier film during the formation of the meandering circuit, providing support for the entire first circuit board during cutting, thus facilitating the fabrication of the meandering circuit. It also provides support during subsequent waste removal and lamination of the first elastomer composite film to form a thin, stretchable flexible circuit board. This non-adhesive protective film has non-adhesive properties, meaning that adhesion can be reduced through certain non-adhesive operations (i.e., reducing adhesive force). Therefore, after the meandering circuit is fabricated... When the waste material is torn off, the strong adhesion before the de-adhesion operation ensures a strong bond between the winding circuit and the de-adhesion protective film, guaranteeing that the winding circuit will separate from the de-adhesion protective film when the waste material is torn off. Then, after the first elastomer composite film is laminated, the weaker adhesion after the de-adhesion operation ensures that the de-adhesion protective film can be easily torn off while ensuring that the winding circuit does not separate from the first elastomer composite film. This enables the mass production of stretchable flexible circuit boards and improves the mass production yield. In addition, the first elastomer composite film is a composite structure with multiple polymer films. It can encapsulate the winding circuit based on the elasticity of the polymer films and adapt to different lamination processes by utilizing the characteristics of different polymer films. This makes it easier to reduce the thickness of the stretchable flexible circuit board and realize the thinning and miniaturization of flexible stretchable electronic products.

[0059] The following provides a detailed explanation of each step in the fabrication process of thin, stretchable, flexible circuit boards.

[0060] In this embodiment S1, the flexible circuit board with a circuit layer and two protective film layers refers to a circuit board that has undergone the DES process, including dry film development and exposure, etching, film removal, chemical cleaning, application of protective film layers, lamination, etc. After these processes, a circuit layer conforming to the product design is formed on the flexible circuit board, and protective film layers are applied to both sides of the circuit layer.

[0061] In this embodiment S1, the main components of the anti-adhesion protective film include polyester film (PET) and special acrylic adhesive. It possesses good adhesion and protective properties, and can reduce adhesion and friction under certain conditions to achieve specific applications. Anti-adhesion protective films are often used in wafer dicing applications, but in this embodiment, they are used in the fabrication of thin, stretchable, flexible circuit boards as a carrier film. On one hand, this provides support for the shape cutting of the protective film layer; on the other hand, it ensures a strong bond between the winding lines and the anti-adhesion protective film during waste removal after the winding lines are fabricated, ensuring that the winding lines do not separate from the anti-adhesion protective film during waste removal. Furthermore, after bonding the first elastomer composite film, the reduced adhesion after the anti-adhesion operation ensures that the anti-adhesion protective film can be easily torn off while preventing the winding lines from separating from the first elastomer composite film. This overcomes the mass production difficulties of flexible, stretchable electronic products in traditional technologies and improves mass production yield.

[0062] It should be noted that the circuit layer in this embodiment includes circuits that already have a meandering shape (the formation of the meandering shape can be achieved using conventional methods, which will not be described in detail here). Because the protective film layer is applied as a single sheet onto the circuit layer during the actual application process, the meandering circuits cannot stretch or contract, and therefore cannot become truly stretchable meandering circuits. Therefore, it is necessary to subsequently cut the protective film layer to allow the circuits to stretch or contract at the meandering points.

[0063] Before the external cutting in this embodiment S2, the cross-sectional structure of the first circuit board is as follows: Figure 2A As shown; in this embodiment S2, there are various methods for shape cutting, such as laser pattern cutting or punching with a mold of a specific pattern. In these methods, it is necessary to cut the protective film layer where the circuit needs to be curved, and to ensure that it does not affect the anti-adhesion protective film, so as to ensure the integrity and continuity of the anti-adhesion protective film. The cross-sectional structure of the first circuit board after shape cutting is shown in the figure. Figure 2B As shown. In Figure 2A and Figure 2B In the diagram, 111 is the substrate layer, 112 is the conductor layer, 113 is the protective film layer, 114 is the adhesive layer, and 4 is the anti-adhesion protective film.

[0064] Preferably, such as Figure 2B , Figures 3-5 As shown, the meandering line 11 manufactured in this embodiment S2 includes:

[0065] Substrate layer 111;

[0066] At least one conductive layer 112 is formed on one or both sides of the substrate layer 111;

[0067] Two protective film layers 113, after being cut to their outer shape, are respectively bonded to the outermost conductor layer 112 or the substrate layer 111 by an adhesive layer 114.

[0068] The aforementioned winding circuit structure has both good stretchability and excellent circuit protection performance, ensuring the functionality of the entire stretchable flexible circuit board. It can guarantee that the metal in the circuit layer will not develop cracks or fissures that affect functionality during stretching and springback, thus improving service life.

[0069] Specifically, the substrate layer 111 is made of any one or a mixture of several of polyimide (PI), polyester resin (PET), LCP, and polybutylene phthalate (PBT). Among them, LCP is a liquid crystal polymer, and its raw materials include polyphenylene terephthalate (PBT), polymethyl methacrylate (PMMA), and polycarbonate (PC), etc.

[0070] The conductor layer 112 is a metal conductor layer, and its material is copper or aluminum.

[0071] The material of the protective film layer 113 may also include any one or a mixture of several of polyimide (PI), polyester resin (PET), LCP, and polybutylene phthalate (PBT), used to protect the conductor layer and substrate layer of the inner layer of the winding circuit.

[0072] The adhesive layer 114 is made of any one or a mixture of epoxy resin, acrylic resin, and polyolefin resin.

[0073] In a meandering circuit, the number of conductor layers can be one, two, or more. When it is one layer, it is formed only on one side of the substrate layer; when it is two or more layers, it can be formed on one side of the substrate layer or on both sides of the substrate layer (usually on both sides).

[0074] In the meandering circuit, there are two protective film layers, each bonded to the outermost layer of the meandering circuit by an adhesive layer (therefore, there are also at least two adhesive layers). Specifically, when the substrate layer has conductor layers on only one side, one of the two protective film layers is bonded to the outermost conductor layer by an adhesive layer, and the other of the two protective film layers is bonded to the outermost substrate layer by an adhesive layer. When conductor layers are distributed on both sides of the substrate layer, one of the two protective film layers is bonded to the outermost conductor layer on the first side of the meandering circuit by an adhesive layer, and the other of the two protective film layers is bonded to the outermost conductor layer on the second side of the meandering circuit by an adhesive layer.

[0075] In a winding route, each conductor layer contains one or more conductors.

[0076] By using one or more wires, it is possible to adapt to the design of different flexible and stretchable electronic products.

[0077] The number of conductor layers and the number of conductors in each conductor layer depend on the specific product design and are not limited here.

[0078] This embodiment Figure 2B , Figures 3-5 The exhibited meandering circuit 11 comprises a substrate layer 111, two conductor layers 112, two protective film layers 113 (cut into shape), and two adhesive layers 114. The two conductor layers 112 are located on either side of the substrate layer 111, and the two protective film layers 113 (cut into shape) are bonded to the outer sides of the conductor layers 112 by adhesive layers 114, forming a double-layer circuit structure. Figure 4 The winding route in the middle is U-shaped. Figure 5 The winding route in the middle is horseshoe-shaped (in Figure 4 and Figure 5 (The two adhesive layers 114 are not shown). In each conductor layer, there are two conductors.

[0079] In this embodiment, the number of winding lines is greater than or equal to 1.

[0080] By varying the number of winding lines, different flexible and stretchable electronic product designs can be accommodated. The specific number and shape of the winding lines depend on the specific product design and are not limited here.

[0081] In this embodiment S2, the meandering line 11 is a stretchable region of the circuit layer. When the circuit layer is fabricated as the meandering line 11, the circuit layer on the first circuit substrate also includes a transition region 12 connected to both ends of the meandering line 11 and a non-stretchable region 13 connected to the transition regions 12 at both ends, such as... Figure 6 As shown (where, Figure 6 Four meandering lines 11 are shown. The transition zone 12 consists of a circuit board structure that gradually thickens, allowing for a gradual change in stress during stretching, making it less prone to breakage. The non-stretchable zone 13 consists of a circuit board structure of fixed dimensions, which does not change size during stretching. It can be equipped with functional components or components with different functions connected to different meandering lines, depending on the specific requirements. Figure 6 In the middle, the four transition zones 12 at each end are all connected to the same non-stretchable zone 13.

[0082] Preferably, in this embodiment S3, as Figure 7As shown, the first elastomeric composite film 2 includes a first polymer film layer 21 having a first melting point and a second polymer film layer 22 having a second melting point, wherein the second polymer film layer 22 is disposed on one side of the first polymer film layer 21; wherein the first melting point is lower than the second melting point.

[0083] Using a first polymer film layer with a lower melting point (i.e., the first melting point) and a second polymer film layer with a higher melting point (i.e., the second melting point) as the first elastomer composite film provides both good elasticity to encapsulate winding circuits and the ability to adapt to different lamination processes by utilizing the properties of different polymer films. The first polymer film layer with the lower melting point flows during lamination, serving to bond the entire first elastomer composite film to the flexible circuit board (specifically, the second circuit board substrate), and can reduce the overall thickness of the first elastomer composite film, which is beneficial for the miniaturization and thinning of flexible circuit board electronic products. The second polymer film layer with the higher melting point does not flow during lamination, ensuring the elasticity of the entire first elastomer composite film while also guaranteeing its strength, thus protecting the flexible circuit board electronic product.

[0084] In a first alternative embodiment, S3 includes:

[0085] S3A1: Perform an anti-adhesion operation on the anti-adhesion protective film on the first side of the second circuit board, so that the anti-adhesion protective film has the second preset adhesion force;

[0086] S3A2: Provides the first elastomer composite film;

[0087] S3A3: The first side of the first elastomer composite film with the first polymer film layer is attached to the second side of the second circuit substrate after the de-adhesion operation to form the third circuit substrate.

[0088] The first optional embodiment described above uses a method of first reducing adhesion and then bonding the first elastomeric composite film to form the third circuit substrate. This method reduces the adhesion of the anti-adhesion protective film through the anti-adhesion operation, ensuring that the anti-adhesion protective film can be easily peeled off when the third circuit substrate is formed, while also ensuring that the winding circuit does not separate from the first elastomeric composite film. The side of the first elastomeric composite film with the first polymer film layer is used as the inner layer and bonded to the second side of the second circuit substrate. This utilizes the carrier film function of the anti-adhesion protective film, which facilitates the bonding operation, and does not affect the subsequent peeling off of the anti-adhesion protective film. At the same time, it also makes it easier to utilize the low melting point of the first polymer film layer to achieve a good adhesion effect between the entire first elastomeric composite film and the flexible board (specifically the second circuit substrate), thereby achieving the purpose of encapsulating the winding circuit.

[0089] In a second alternative embodiment, S3 includes:

[0090] S3B1: Provides the first elastomer composite film;

[0091] S3B2: The side of the first elastomer composite film having the first polymer film layer is attached to the second side of the second circuit substrate;

[0092] S3B3: Perform an anti-adhesion operation on the anti-adhesion protective film on the first side of the second circuit substrate, so that the anti-adhesion protective film has the second preset adhesion force, thereby forming the third circuit substrate.

[0093] The second optional embodiment described above uses a method of first bonding the first elastomeric composite film and then reducing adhesion to form the third circuit board. Similar to the first optional embodiment, the adhesion reduction operation can reduce the adhesive force of the adhesion reduction protective film, so that when the adhesion reduction protective film is peeled off after the third circuit board is formed, it can be easily peeled off while ensuring that the winding circuit does not separate from the first elastomeric composite film. The side of the first elastomeric composite film with the first polymer film layer is used as the inner layer and bonded to the second side of the second circuit board. This facilitates the bonding operation and does not affect the subsequent peeling off of the adhesion reduction protective film. At the same time, it achieves a good adhesion effect between the entire first elastomeric composite film and the flexible board (specifically the second circuit board), thus achieving the purpose of encapsulating the winding circuit.

[0094] In addition, compared with the first optional embodiment, the second optional embodiment can also avoid the effects caused by the flexible board separating from the de-adhesion protective film due to movement and handling after the de-adhesion operation, and the adhesive on the de-adhesion protective film reacting with the first elastomer composite film during the de-adhesion operation, thereby further improving the mass production yield of flexible and stretchable electronic products.

[0095] Of course, if the flexible board will not separate from the anti-adhesion protective film due to movement or handling after the anti-adhesion operation, and the adhesive on the anti-adhesion protective film will not react with the first elastomer composite film during the anti-adhesion operation, then the first optional embodiment or the second optional embodiment can be selected to form the third circuit board according to the actual situation.

[0096] Preferably, the anti-adhesion protective film includes either a UV anti-adhesion film or a thermal anti-adhesion film.

[0097] Preferably, when the anti-adhesion protective film is the UV anti-adhesion film, in S3, an anti-adhesion operation is performed on the anti-adhesion protective film on the first side of the second circuit substrate, including:

[0098] The anti-adhesion protective film on the first side of the second circuit board is subjected to UV irradiation;

[0099] When the anti-adhesion protective film is the heat-resistant anti-adhesion film, in S3, an anti-adhesion operation is performed on the anti-adhesion protective film on the first side of the second circuit substrate, including:

[0100] The anti-adhesion protective film on the first side of the second circuit board is heated.

[0101] Both UV anti-adhesion films and thermal anti-adhesion films have good adhesion and protective properties, and can reduce adhesion through simple anti-adhesion operations (including UV irradiation and heating), thereby reducing the difficulty of mass production of flexible and stretchable electronic products.

[0102] Preferably, the first preset adhesive force is greater than 500 gf / inch, and the second preset adhesive force is less than 100 gf / inch.

[0103] The first preset adhesion force within the aforementioned range ensures that, when removing waste material after the winding circuit is fabricated, a strong bond between the winding circuit and the anti-adhesion protective film is maintained based on this larger adhesion force, ensuring that the winding circuit separates from the anti-adhesion protective film when the waste material is removed. The second preset adhesion force within the aforementioned range ensures that, after the first elastomer composite film is bonded, the anti-adhesion protective film can be easily removed based on this smaller adhesion force, while also ensuring that the winding circuit does not separate from the first elastomer composite film. This enables the mass production of stretchable flexible circuit boards and improves the mass production yield.

[0104] Both UV anti-tack membranes and thermal anti-tack membranes can be selected according to the actual situation. For example, the UV anti-tack membrane model SL-9715UV-3 can be selected, and the thermal anti-tack membrane model SL-9900J can be selected.

[0105] In this embodiment, both the bonding of the anti-adhesion protective film and the bonding of the first elastomer composite film can be performed using conventional bonding methods. Similarly, both the removal of waste material and the removal of the anti-adhesion protective film can be performed using conventional removal methods. The specific details of the bonding and removal methods are not elaborated here.

[0106] Preferably, in step S4, after removing the anti-adhesion protective film from the third circuit board, the process further includes:

[0107] A second elastomeric composite film identical to the first elastomeric composite film is provided;

[0108] The side of the second elastomer composite film with the first polymer film layer is attached to the first side of the third circuit board after the anti-adhesion protective film is peeled off.

[0109] By attaching a second elastomeric composite film identical to the first elastomeric composite film to the first side of the third circuit board after the anti-adhesion protective film has been peeled off, both sides of the entire third circuit board can be encapsulated, further enhancing the protection of the winding lines and improving product quality.

[0110] The specific operation method for bonding the second elastomer composite film is the same as that for bonding the first elastomer composite film, and the specific details will not be repeated here.

[0111] Preferably, in the first elastomeric composite film and the second elastomeric composite film, the difference between the second melting point and the first melting point is in the range of 20 to 100°C.

[0112] Preferably, the difference between the second melting point and the first melting point is in the range of 30 to 60°C.

[0113] The aforementioned difference in melting points better meets the requirements of different lamination processes, ensuring that the first polymer film layer with a lower melting point flows during lamination, thus bonding the entire first elastomer composite film to the flexible board (specifically the second circuit board), and facilitating the miniaturization and thinning of flexible board electronic products; it also ensures that the second polymer film layer with a higher melting point does not flow during lamination, thus ensuring the strength of the entire first elastomer composite film while maintaining its elasticity.

[0114] Preferably, in the first elastomeric composite film and the second elastomeric composite film, the thickness of the first polymer film layer ranges from 30 to 100 μm, and / or the thickness of the second polymer film layer ranges from 25 to 150 μm.

[0115] The first and second polymer film layers within the aforementioned thickness range can ensure that both polymer film layers fully utilize their own characteristics, while maximizing the reduction of the overall thickness of the first and second elastomer composite films, which helps to make flexible and stretchable electronic products thinner and smaller.

[0116] Preferably, in the first elastomer composite film and the second elastomer composite film, the tensile modulus of the first polymer film layer and the tensile modulus of the second polymer film layer are both less than 10 MPa; and / or, the elongation at break of the first polymer film layer and the tensile modulus of the second polymer film layer are both greater than or equal to 200%.

[0117] The tensile modulus and elongation at break within the above range can effectively ensure the good stretchability of the entire target circuit board.

[0118] In an optional embodiment, both the first polymer film layer and the second polymer film layer are made of one or more copolymers selected from polyesters, polyimides, polyamides, polyolefins, polyurethanes, polycarbonates, and polyacrylonitrile-butene-styrene copolymers.

[0119] The first and second polymer film layers of the aforementioned materials can provide elasticity after stretching. Unlike new conductive materials such as conductive polymers, composite materials of conductive particles and elastomers, and liquid metals (usually alloys containing gallium and indium), their conductivity will not decrease with the increase of stretch elongation. Their tensile properties are stable, which is beneficial for manufacturing flexible and stretchable electronic products with excellent tensile properties.

[0120] Preferably, after bonding the second elastomer composite film, the method further includes:

[0121] The third circuit board, after being laminated with the second elastomer composite film, is baked.

[0122] Baking can further solidify the first polymer film layer with a lower melting point in the first elastomeric composite film and the second elastomeric composite film, resulting in better bonding between the first elastomeric composite film and the flexible plate, as well as between the second elastomeric composite film and the flexible plate.

[0123] The final front view structure of the target circuit board produced in this embodiment is as follows: Figure 8 As shown, the cross-sectional structure is as follows Figure 9 As shown, it includes a flexible plate 1 with a meandering line 11 and a first elastomeric composite film 2 and a second elastomeric composite film 3 located on both sides of the flexible plate 1.

[0124] It should be understood that, in actual production, the target circuit board is manufactured in batches. Figure 9 The flexible board 1 has multiple meandering lines (specifically four); and when the second elastomeric composite film 3 is pressed onto the third circuit substrate, the first polymer film layer in the second elastomeric composite film 3 flows due to the pressing, and fuses with the first polymer film layer in the first elastomeric composite film 2 and the first polymer film layer in the second elastomeric composite film 3 on the adjacent flexible board, thus becoming one with them. Figure 9 The first polymer film layer 21 is actually an integral structure of the first polymer film layer in the first elastomer composite film 2 and the first polymer film layer in the second elastomer composite film 3.

[0125] To further illustrate this solution, four embodiments were fabricated, each producing a sample of the target circuit board described in this solution (the cross-sectional structure of each sample is as shown in the diagram). Figure 8 (as shown), and the maximum elongation and number of stretching cycles of each sample were compared.

[0126] The cross-section of the meandering line 11 in the sample prepared in Example 1 is as follows: Figure 4 As shown, the first polymer film layer in the first elastomer composite film and the second elastomer composite film is a TPU (i.e., polyurethane) film with a first melting point of 100°C, a tensile modulus of 0.4 MPa, and a thickness of 60 μm; the second polymer film layer in the first elastomer composite film and the second elastomer composite film is also a TPU (i.e., polyurethane) film with a second melting point of 150°C, a tensile modulus of 4 MPa, and a thickness of 60 μm.

[0127] The cross-section of the meandering line 11 in the sample prepared in Example 2 is as follows: Figure 5 As shown, the first polymer film layer and the second polymer film layer in the first elastomer composite film and the second elastomer composite film are the same as in Example 1, and will not be listed here again.

[0128] The cross-section of the meandering line 11 in the sample prepared in Example 3 is as follows: Figure 4 As shown, the first polymer film layer in the first elastomer composite film and the second elastomer composite film is a PDMS (polydimethylsiloxane) film, with a first melting point of 120°C, a tensile modulus of 0.1 MPa, and a thickness of 60 μm; the second polymer film layer in the first elastomer composite film and the second elastomer composite film is also a PDMS (polydimethylsiloxane) film, with a second melting point of 170°C, a tensile modulus of 0.4 MPa, and a thickness of 100 μm.

[0129] The cross-section of the meandering line 11 in the sample prepared in Example 4 is as follows: Figure 5 As shown, the first polymer film layer and the second polymer film layer in the first elastomer composite film and the second elastomer composite film are the same as in Example 3, and will not be listed here again.

[0130] After the samples in each embodiment were prepared, the maximum elongation and the number of tensile cycles of each sample were evaluated and compared. The evaluation method is as follows:

[0131] The evaluation process for maximum elongation is as follows:

[0132] (1) Measure the length L0 of the stretchable area of ​​the sample, clamp the non-stretchable areas at both ends of the sample on the tensile testing machine fixture, and keep the sample in its natural shape.

[0133] (2) Stretch the sample at a stretching speed of 500 mm / min until the sample breaks. At this time, the elongation of the stretchable area of ​​the sample is L.

[0134] (3) Calculate the maximum elongation of the sample. The calculation formula is: L / L0×100%.

[0135] The evaluation process for the number of stretching cycles is as follows:

[0136] (1) Measure the length L0 of the tensile zone of the sample, and then fix both ends of the sample on the tensile fatigue testing machine fixture to maintain the natural shape of the sample.

[0137] (2) Connect the resistance test electrodes to both ends of the winding line to test whether the metal wires in the winding line are broken.

[0138] (3) Circularly stretch the sample, each stretching making the stretchable area of ​​the sample extend by 100% of its length, stretching 45 times per minute, until the test fails or the wire breaks.

[0139] The maximum elongation and number of stretching cycles of the samples in each embodiment were evaluated according to the above evaluation method. The comparison results of the maximum elongation and number of stretching cycles of each sample after evaluation are shown in Table 1 below.

[0140] Table 1. Maximum elongation and number of stretching cycles for each sample in the four examples.

[0141] Maximum elongation 224 234 176 188 stretching cycles 2000 2000 3000 3000

[0142] Based on the above comparison results, the thin, stretchable, flexible circuit board manufactured using the method described in this solution has excellent stretchability.

[0143] Example 2

[0144] This embodiment provides a thin, stretchable, flexible circuit board, which is manufactured using the method described in Embodiment 1.

[0145] The thin, stretchable flexible circuit board manufactured in this embodiment, compared with traditional stretchable circuit boards, can reduce the difficulty of mass production and improve the yield of mass-produced products based on the anti-adhesion protective film; it can also encapsulate the winding circuit based on the elasticity of the composite structure of polymer film and adapt to different pressing processes, thereby making it easier to reduce the thickness of the stretchable flexible circuit board and realize the thinning and miniaturization of flexible stretchable electronic products.

[0146] The fabrication method used for the thin, stretchable flexible circuit board in this embodiment is the same as the method described in Embodiment 1. Therefore, for details not covered in this embodiment, please refer to Embodiment 1 and... Figures 1-9 The specific description will not be repeated in this embodiment.

[0147] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for manufacturing a thin, stretchable, flexible circuit board, characterized in that, include: A flexible circuit board with a circuit layer and two protective film layers is provided. A non-adhesive protective film is laminated to a first side of the flexible circuit board to form a first circuit board. The two protective film layers are respectively located on both sides of the circuit layer. The non-adhesive protective film has a first preset adhesion force. From the second side of the first circuit board, the two protective film layers in the first circuit board are cut to form a meandering circuit, and the cut first circuit board is then ripped to remove waste material, forming a second circuit board; wherein the meandering circuit has at least one stretching direction. A first elastomeric composite film is provided, the first elastomeric composite film is adhered to the second side of the second circuit substrate, and the anti-adhesion protective film on the first side of the second circuit substrate is subjected to an anti-adhesion operation, so that the anti-adhesion protective film has a second preset adhesion force, thereby forming a third circuit substrate; wherein, the second preset adhesion force is less than the first preset adhesion force. The anti-adhesion protective film is peeled off the third circuit board to form the target circuit board.

2. The method according to claim 1, characterized in that, The anti-adhesion protective film includes either a UV anti-adhesion film or a thermal anti-adhesion film.

3. The method according to claim 2, characterized in that, When the anti-adhesion protective film is the UV anti-adhesion film, the anti-adhesion operation on the anti-adhesion protective film on the first side of the second circuit substrate includes: The anti-adhesion protective film on the first side of the second circuit board is subjected to UV irradiation; When the anti-adhesion protective film is the heat-resistant anti-adhesion film, the anti-adhesion operation on the anti-adhesion protective film on the first side of the second circuit substrate includes: The anti-adhesion protective film on the first side of the second circuit board is heated.

4. The method according to claim 1, characterized in that, The first preset adhesive force is greater than 500 gf / inch, and the second preset adhesive force is less than 100 gf / inch.

5. The method according to claim 1, characterized in that, The first elastomeric composite film includes a first polymer film layer having a first melting point and a second polymer film layer having a second melting point, wherein the second polymer film layer is disposed on one side of the first polymer film layer; wherein the first melting point is lower than the second melting point.

6. The method according to claim 5, characterized in that, The process of providing a first elastomeric composite film, attaching the first elastomeric composite film to the second side of the second circuit substrate, and performing an anti-adhesion operation on the anti-adhesion protective film on the first side of the second circuit substrate to give the anti-adhesion protective film a second preset adhesion force, thereby forming a third circuit substrate, includes: The adhesive-reducing protective film on the first side of the second circuit board is subjected to an adhesive-reducing operation, so that the adhesive-reducing protective film has the second preset adhesive force; Provide the first elastomer composite film; The first side of the first elastomer composite film with the first polymer film layer is attached to the second side of the second circuit substrate after the de-adhesion operation to form the third circuit substrate.

7. The method according to claim 5, characterized in that, The process of providing a first elastomeric composite film, attaching the first elastomeric composite film to the second side of the second circuit substrate, and performing an anti-adhesion operation on the anti-adhesion protective film on the first side of the second circuit substrate to give the anti-adhesion protective film a second preset adhesion force, thereby forming a third circuit substrate, includes: Provide the first elastomer composite film; The side of the first elastomer composite film having the first polymer film layer is attached to the second side of the second circuit substrate. The adhesive-reducing protective film on the first side of the second circuit board is subjected to an adhesive-reducing operation, so that the adhesive-reducing protective film has the second preset adhesive force, thereby forming the third circuit board.

8. The method according to claim 5, characterized in that, After removing the anti-adhesion protective film from the third circuit board, the process further includes: A second elastomeric composite film identical to the first elastomeric composite film is provided; The side of the second elastomer composite film with the first polymer film layer is attached to the first side of the third circuit board after the anti-adhesion protective film is peeled off.

9. The method according to claim 5, characterized in that, The difference between the second melting point and the first melting point is in the range of 20 to 100°C.

10. The method according to claim 5, characterized in that, The difference between the second melting point and the first melting point is in the range of 30 to 60°C.

11. The method according to claim 5, characterized in that, The thickness of the first polymer film layer ranges from 30 to 100 μm, and / or the thickness of the second polymer film layer ranges from 25 to 150 μm.

12. The method according to any one of claims 1 to 11, characterized in that, The winding route includes: Substrate layer; At least one conductive layer is formed on one or both sides of the substrate layer; and The two protective film layers, after being cut to their respective shapes, are bonded to the outermost conductor layer or the substrate layer using adhesive layers.

13. The method according to claim 12, characterized in that, Each of the aforementioned conductor layers contains one or more conductors.

14. A thin, stretchable, flexible circuit board, characterized in that, It is manufactured using the manufacturing method described in any one of claims 1 to 13.

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