Heated flexible circuit board and manufacturing method thereof

Abstract

The present invention discloses a heatable flexible circuit board and a manufacturing method thereof, the method comprising: forming a circuit layer on at least one surface of a flexible substrate; printing a diene adhesive layer onto the surface of the circuit layer on at least one surface of the flexible substrate to form a first flexible circuit board; pre-treating a ceramic sheet, and pressing the pre-treated ceramic sheet onto the surface of the diene adhesive layer on at least one surface of the first flexible circuit board to form a second flexible circuit board; curing the second flexible circuit board; pressing a protective layer onto at least one surface of the cured second flexible circuit board to form a target flexible circuit board. Based on the corrosion resistance of the diene adhesive layer and the high thermal conductivity of the ceramic sheet, the present invention can prevent the copper material on the circuit layer of the flexible board from being oxidized and chemically reacting with the liquid; it can also exhibit good thermal conductivity, can be immersed in liquid, has good and stable heating function, and has a wide range of applications.

Description

Technical Field

[0001] The invention relates to the technical field of flexible circuit board manufacturing, and in particular to a heatable flexible circuit board and a manufacturing method thereof. Background Art

[0002] With the birth and development of flexible printed circuit boards (FPCs), heating functions are needed in many specific environments, such as preheating devices on cars or heating functions in liquid environments. Although the current flexible boards use copper as the substrate and can also achieve local heating, the heating element is copper after all, and there are many unstable factors, such as copper surface oxidation, chemical reaction with liquid, unstable heating, and temperature that cannot meet requirements. Based on this, it is urgent to develop a flexible board that can solve the above problems well and has a good thermal conductivity, so as to expand the application range of flexible circuit boards. Summary of the invention

[0003] In view of this, the present invention provides a heatable flexible circuit board and a manufacturing method thereof to solve the problems of the existing flexible circuit board, such as copper surface oxidation, chemical reaction with liquid, unstable heating and temperature failure to meet the requirements.

[0004] The present invention provides a method for manufacturing a heatable flexible circuit board, comprising:

[0005] Providing a flexible substrate, and forming a circuit layer on at least one surface of the flexible substrate;

[0006] Providing a diene adhesive layer, and printing the diene adhesive layer on the surface of the circuit layer on at least one surface of the flexible substrate to form a first flexible circuit board; wherein the diene adhesive layer has a conjugated diene structure and a dienophilic structure;

[0007] Providing a ceramic sheet, pre-treating the ceramic sheet, and pressing the pre-treated ceramic sheet onto a surface of the diene adhesive layer on at least one surface of the first flexible circuit board to form a second flexible circuit board;

[0008] performing a curing process on the second flexible circuit board;

[0009] A protective layer is provided, and the protective layer is pressed on at least one surface of the second flexible circuit board after the curing process to form a target flexible circuit board.

[0010] Optionally, the flexible substrate is any one of a single-layer board, a double-layer board and a multi-layer board.

[0011] Optionally, forming a circuit layer on at least one surface of the flexible substrate includes:

[0012] The circuit layer is formed on at least one surface of the flexible substrate by sequentially adopting the processes of dry film lamination, exposure, development and etching.

[0013] Optionally, the diene adhesive layer has a thickness of 0.19 to 0.21 mm.

[0014] Optionally, the pre-treating the ceramic sheet includes:

[0015] Cutting the ceramic sheet according to a preset size;

[0016] The cut ceramic sheets are etched by a plasma etching method.

[0017] Optionally, the curing of the second flexible circuit board includes:

[0018] The second flexible circuit board is baked according to preset baking parameters, so that the diene adhesive layer in the second flexible circuit board is cured.

[0019] Optionally, the preset baking parameters include a first baking time, a first baking temperature, a second baking time and a second baking temperature.

[0020] Optionally, baking the second flexible circuit board according to preset baking parameters includes:

[0021] baking the second flexible circuit board once according to the first baking temperature and the first baking time;

[0022] The second flexible circuit board is baked for a second time according to the second baking temperature and the second baking time.

[0023] Optionally, laminating the protective layer on at least one surface of the second flexible circuit board after the curing process to form a target flexible circuit board comprises:

[0024] According to preset hot pressing parameters, the protective layer is pressed onto the four sides of the ceramic sheet on at least one surface of the second flexible circuit board after baking by hot pressing to form the target flexible circuit board.

[0025] Optionally, the preset hot pressing parameters include hot pressing temperature, pre-pressing pressure and molding pressure.

[0026] Optionally, each of the circuit layers is two straight lines arranged in parallel.

[0027] In addition, the present invention also provides a heatable flexible circuit board, which is manufactured using the aforementioned manufacturing method.

[0028] The beneficial effects of the present invention are as follows: the circuit layer of the flexible board is usually made of copper material. By sequentially manufacturing a stack of a diene adhesive layer and a ceramic sheet on the circuit layer on the flexible substrate, based on the corrosion resistance of the diene adhesive layer and the high thermal conductivity of the ceramic sheet, the copper material on the circuit layer of the flexible board can be prevented from being oxidized and chemically reacting with the liquid; a better thermal conductivity coefficient can also be obtained, showing better thermal conductivity performance; the target flexible circuit board finally formed by the present invention can be immersed in liquid and has a good and stable heating function, and has a wider range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the present invention in any way. In the accompanying drawings:

[0030] Figure 1 A flow chart showing a method for manufacturing a heatable flexible circuit board in Embodiment 1 of the present invention is shown;

[0031] Figure 2-1 A schematic diagram of the cross-sectional structure of a single-layer board in the first embodiment of the present invention is shown;

[0032] Figure 2-2 A schematic diagram of the cross-sectional structure of a double-layer plate in the first embodiment of the present invention is shown;

[0033] Figure 2-3 A schematic cross-sectional structure diagram of a multilayer board in Embodiment 1 of the present invention is shown;

[0034] Figure 3-1 A schematic diagram of the top view structure of the first target flexible circuit board or the third target flexible circuit board in the first embodiment of the present invention is shown;

[0035] Figure 3-2 A schematic cross-sectional structure diagram of a first target flexible circuit board in Embodiment 1 of the present invention is shown;

[0036] Figure 3-3 A schematic diagram of the top view structure of a second target flexible circuit board in the first embodiment of the present invention is shown;

[0037] Figure 3-4 A schematic cross-sectional structure diagram of a second target flexible circuit board in the first embodiment of the present invention is shown;

[0038] Figure 3-5 A schematic cross-sectional structure diagram of a third target flexible circuit board in the first embodiment of the present invention is shown;

[0039] Figure 4-1 A schematic diagram showing the design of the first circuit layer in the first embodiment of the present invention is shown;

[0040] Figure 4-2A schematic diagram showing the design of the second circuit layer in the first embodiment of the present invention is shown;

[0041] Figure 5 A schematic diagram of a top view structure of a plurality of flexible plates connected in series in the first embodiment of the present invention is shown;

[0042] Figure 6 A schematic diagram of a top view structure of a plurality of flexible plates connected in parallel in the first embodiment of the present invention is shown.

[0043] Description of reference numerals:

[0044] 1. Copper foil, 2. PI layer, 3. Adhesive layer, 4. Diolefin adhesive layer, 5. Ceramic sheet, 6. Protective film. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0046] Embodiment 1

[0047] A method for manufacturing a heatable flexible circuit board, such as Figure 1 As shown, the following steps are included:

[0048] S1, providing a flexible substrate, and forming a circuit layer on at least one surface of the flexible substrate.

[0049] Specifically, the flexible substrate is any one of a single-layer board, a double-layer board and a multi-layer board.

[0050] The single-layer board is specifically a single-sided copper-clad substrate composed of a single layer of copper foil and a flexible insulating base film (PI layer), such as Figure 2-1 As shown; the double-layer board is specifically a double-sided copper-clad substrate composed of a double-layer copper foil and a PI layer, and the double-layer copper foil is located on both sides of the PI layer, such as Figure 2-2 As shown; the multilayer board is specifically a combination of a single-sided board and a double-sided board, such as Figure 2-3 shown in Figure 2-1 , Figure 2-2 and Figure 2-3 In the figure, 1 represents copper foil, 2 represents PI layer, and 3 represents adhesive layer. For the convenience of explanation, this embodiment takes single-layer board and double-layer board as examples for explanation, and the subsequent production process of multi-layer board is the same, which will not be described in detail in this embodiment.

[0051] Preferably, in S1, forming a circuit layer on at least one surface of the flexible substrate includes:

[0052] The circuit layer is formed on at least one surface of the flexible substrate by sequentially adopting the processes of dry film lamination, exposure, development and etching.

[0053] Through the above process, it is convenient to form the required circuit layer on at least one surface of the flexible substrate, and then it is convenient to achieve electrical connectivity between the various layers of the target flexible circuit board in accordance with the personalized design.

[0054] It should be noted that the circuit layer is made of copper foil on the flexible substrate, and its material is copper. When the flexible substrate is a single-layer board, according to the personalized design, the copper foil on the single-layer board is made into a circuit layer by sequentially adopting the processes of laminating dry film, exposure, development and etching, such as Figure 3-1 , Figure 3-2 , Figure 3-3 and Figure 3-4 When the flexible substrate is a double-layer board, according to the personalized design, the processes of laminating dry film, exposure, development and etching are adopted in sequence, and the copper foil on any surface of the double-layer board can be made into a circuit layer, or the copper foil on both surfaces of the double-layer board can be made into a circuit layer, such as Figure 3-1 and Figure 3-5 As shown, it depends on the actual needs. Figure 3-1 to Figure 3-5 1 represents copper foil, 2 represents PI layer, 4 represents diene adhesive layer, 5 represents ceramic sheet, and 6 represents protective layer. The specific operation methods of the above-mentioned dry film lamination, exposure, development and etching processes all adopt conventional operation methods, which will not be repeated here.

[0055] Preferably, each circuit layer is two straight lines arranged in parallel.

[0056] The design of two parallel straight lines can increase the area ratio of the lines, thereby facilitating the improvement of the heating performance of the final target flexible circuit board.

[0057] Specifically, in this embodiment, two parallel straight lines are respectively as follows: Figure 4-1 and Figure 4-2 As shown. Among them, Figure 4-1 The wiring layer shown can facilitate the formation of series connections between multiple flexible boards, such as Figure 5 More specifically, in Figure 4-1 and Figure 5 In the embodiment, when multiple flexible boards are connected in series, the circuit layer in each target flexible circuit board is two parallel straight lines with a spacing of 0, that is, it is expressed as two disconnected straight lines on a straight line; of course, there can be a certain spacing between these two straight lines, that is, two parallel straight lines that are not on a straight line, as long as the series connection between the flexible boards can be achieved. Figure 4-2 The wiring layer shown can facilitate the formation of parallel connections between multiple flexible boards, such as Figure 6 shown in Figure 4-2 and Figure 6 In the embodiment, there is a certain distance between two parallel straight lines. The specific size and specific distance (if there is a certain distance) of the straight lines depend on the specific design, for example, the length of the straight line is designed to be 19.9 mm and the width is designed to be 5 mm.

[0058] Specifically, in this embodiment, the thickness of the PI layer in the flexible substrate is 85 μm, and the thickness of the formed circuit layer is 35 μm.

[0059] like Figure 1 As shown, S2, providing a diene adhesive layer, and printing the diene adhesive layer onto the surface of the circuit layer on at least one surface of the flexible substrate to form a first flexible circuit board.

[0060] Specifically, the diene adhesive layer in this embodiment has a conjugated diene structure and a dienophilic structure. Based on the above structure, it is convenient to subsequently press the ceramic sheet and the circuit layer together to form a stacked structure with high corrosion resistance and high thermal conductivity; it can also further improve the thermal conductivity and further help improve the heating performance of the target flexible circuit board that is finally formed.

[0061] It should be noted that when a circuit layer is formed on any surface of the flexible substrate in S1, a diene adhesive layer is printed on the surface of the circuit layer in S2, as shown in FIG. Figure 3-2 and Figure 3-4 When circuit layers are formed on both surfaces of the flexible substrate in S2, the diene adhesive layers are printed on the surfaces of the two circuit layers in S2, as shown in FIG. Figure 3-5 shown.

[0062] Preferably, the thickness of the diene adhesive layer is 0.19-0.21 mm.

[0063] The diene glue layer within the above-mentioned thickness range can ensure the pressing effect between the ceramic sheet and the circuit layer, and can also achieve good corrosion resistance and thermal conductivity.

[0064] Specifically, the thickness of the diene adhesive layer in this embodiment is 0.2 mm.

[0065] like Figure 1 As shown, S3, providing a ceramic sheet, pre-treating the ceramic sheet, and pressing the pre-treated ceramic sheet onto the surface of the diene adhesive layer on at least one surface of the first flexible circuit board to form a second flexible circuit board.

[0066] Preferably, in S3, the ceramic sheet is pretreated, including:

[0067] Cutting the ceramic sheet according to a preset size;

[0068] The cut ceramic sheets are etched by a plasma etching method.

[0069] By cutting the ceramic sheet, the ceramic sheet can be designed according to a specified size (i.e., a preset size); by etching the ceramic sheet using a plasma etching method, organic impurities on the ceramic sheet can be removed, thereby ensuring high thermal conductivity of the ceramic sheet.

[0070] Specifically, the thickness of the ceramic sheet in this embodiment is 20 μm.

[0071] It should be noted that when a circuit layer is formed on any surface of the flexible substrate in S1, a ceramic sheet is pressed onto the surface of the diene adhesive layer on the surface of the circuit layer in S3. Figure 3-1 , Figure 3-2 , Figure 3-3 and Figure 3-4 As shown; when the circuit layers are formed on both surfaces of the flexible substrate in S2, the ceramic sheets are printed on the surfaces of the diene adhesive layers on the surfaces of the two circuit layers in S3, as shown Figure 3-1 and Figure 3-5 shown.

[0072] like Figure 1 As shown, S4, the second flexible circuit board is cured.

[0073] Preferably, S4 includes:

[0074] The second flexible circuit board is baked according to preset baking parameters, so that the diene adhesive layer in the second flexible circuit board is cured.

[0075] Preferably, the preset baking parameters include a first baking time, a first baking temperature, a second baking time and a second baking temperature.

[0076] Preferably, baking the second flexible circuit board according to preset baking parameters includes:

[0077] baking the second flexible circuit board once according to the first baking temperature and the first baking time;

[0078] The second flexible circuit board is baked for a second time according to the second baking temperature and the second baking time.

[0079] Through the above two specific baking steps, it is possible to ensure that the diene adhesive layer obtains a good curing effect.

[0080] Specifically, in this embodiment, the first baking temperature is 80° C., and the first baking time is 2 hours; the second baking temperature is 100° C., and the second baking time is 2 hours.

[0081] like Figure 1 As shown, S5, providing a protective layer, and laminating the protective layer on at least one surface of the second flexible circuit board after the curing process to form a target flexible circuit board.

[0082] Specifically, the protective layer is composed of a PI layer and a bonding glue layer.

[0083] Preferably, in S5, laminating the protective layer on at least one surface of the second flexible circuit board after the curing process to form a target flexible circuit board comprises:

[0084] According to preset hot pressing parameters, the protective layer is pressed onto the four sides of the ceramic sheet on at least one surface of the second flexible circuit board after baking by hot pressing to form the target flexible circuit board.

[0085] Preferably, the preset hot pressing parameters include hot pressing temperature, pre-pressing pressure and molding pressure.

[0086] Through the above method, the protective layer can be pressed onto the four sides of the ceramic sheet to ensure that the protective layer plays a good protective role on the entire second flexible circuit board to form a target flexible circuit board; and the curing effect of the diene adhesive layer can be further improved.

[0087] Specifically, in this embodiment, the hot pressing temperature is 120° C., the pre-pressing pressure is 10KG / 5S, and the molding pressure is 120KG / 200S.

[0088] Specifically, the thickness of the protective layer in this embodiment is 75 μm.

[0089] Specifically, in the present embodiment S5, after the protective layer is pressed onto at least one surface of the second flexible circuit board after the curing treatment, the method further includes:

[0090] The second flexible circuit board after the protective layer is laminated is subjected to electrical testing, flatness testing and impedance testing.

[0091] Through electrical testing and flatness testing, it is ensured that the final target flexible circuit board meets the requirements.

[0092] Specifically, the flatness test requires that there should be no bubbles, the impedance test requires a resistance value of 4 to 6Ω, the electrical test requires 5V / 0.1A, and the test temperature is 90 to 100°C.

[0093] In the manufacturing method of the above-mentioned heatable flexible circuit board of this embodiment, the circuit layer of the flexible board is usually made of copper material. By sequentially manufacturing a diene adhesive layer and a ceramic sheet stack on the circuit layer on the flexible substrate, based on the corrosion resistance of the diene adhesive layer and the high thermal conductivity of the ceramic sheet, the copper material on the circuit layer of the flexible board can be prevented from being oxidized and chemically reacting with the liquid; a better thermal conductivity coefficient can also be obtained, showing better thermal conductivity performance; the target flexible circuit board finally formed by the present invention can be immersed in liquid and has a good and stable heating function, and has a wider range of applications.

[0094] Embodiment 2

[0095] A heatable flexible circuit board is manufactured by adopting the manufacturing method of the first embodiment.

[0096] The flexible circuit board manufactured in this embodiment can be immersed in liquid and has a good and stable heating function, and has a wider range of applications.

[0097] Similarly, the flexible circuit board described in this embodiment is manufactured by the manufacturing method described in the first embodiment. Therefore, for the details not provided in this embodiment, please refer to the first embodiment and the second embodiment. Figures 1 to 6 The specific description is omitted here.

[0098] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for manufacturing a heatable flexible circuit board, characterized in that: include: Providing a flexible substrate, and forming a circuit layer on at least one surface of the flexible substrate; Providing a diene adhesive layer, and printing the diene adhesive layer on the surface of the circuit layer on at least one surface of the flexible substrate to form a first flexible circuit board; wherein the diene adhesive layer has a conjugated diene structure and a dienophilic structure; Providing a ceramic sheet, pre-treating the ceramic sheet, and pressing the pre-treated ceramic sheet onto a surface of the diene adhesive layer on at least one surface of the first flexible circuit board to form a second flexible circuit board; performing a curing process on the second flexible circuit board; A protective layer is provided, and the protective layer is pressed on at least one surface of the second flexible circuit board after the curing process to form a target flexible circuit board.

2. The method for manufacturing a heatable flexible circuit board according to claim 1, characterized in that: The flexible substrate is any one of a single-layer board, a double-layer board and a multi-layer board.

3. The method for manufacturing a heatable flexible circuit board according to claim 1, characterized in that: The forming of a circuit layer on at least one surface of the flexible substrate comprises: The circuit layer is formed on at least one surface of the flexible substrate by sequentially adopting the processes of dry film lamination, exposure, development and etching.

4. The method for manufacturing a heatable flexible circuit board according to claim 1, characterized in that: The thickness of the diene adhesive layer is 0.19-0.21 mm.

5. The method for manufacturing a heatable flexible circuit board according to claim 1, characterized in that: The pre-processing of the ceramic sheet comprises: Cutting the ceramic sheet according to a preset size; The cut ceramic sheets are etched by a plasma etching method.

6. The method for manufacturing a heatable flexible circuit board according to claim 1, characterized in that: The curing process of the second flexible circuit board includes: The second flexible circuit board is baked according to preset baking parameters, so that the diene adhesive layer in the second flexible circuit board is cured.

7. The method for manufacturing a heatable flexible circuit board according to claim 6, characterized in that: The preset baking parameters include a first baking time, a first baking temperature, a second baking time and a second baking temperature.

8. The method for manufacturing a heatable flexible circuit board according to claim 7, characterized in that: The step of baking the second flexible circuit board according to preset baking parameters includes: baking the second flexible circuit board once according to the first baking temperature and the first baking time; The second flexible circuit board is baked for a second time according to the second baking temperature and the second baking time.

9. The method for manufacturing a heatable flexible circuit board according to claim 6, characterized in that: The step of laminating the protective layer on at least one surface of the second flexible circuit board after the curing process to form a target flexible circuit board comprises: According to preset hot pressing parameters, the protective layer is pressed onto the four sides of the ceramic sheet on at least one surface of the second flexible circuit board after baking by hot pressing to form the target flexible circuit board.

10. The method for manufacturing a heatable flexible circuit board according to claim 9, characterized in that: The preset hot pressing parameters include hot pressing temperature, pre-pressing pressure and molding pressure.

11. The method for manufacturing a heatable flexible circuit board according to any one of claims 1 to 9, characterized in that: Each of the circuit layers consists of two straight lines arranged in parallel.

12. A heatable flexible circuit board, characterized in that: The invention is manufactured by the manufacturing method according to any one of claims 1 to 11.

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