A flexible circuit board for wireless charging and its manufacturing method and application

Abstract

The present invention provides a flexible circuit board for wireless charging and a manufacturing method and application thereof, the manufacturing method comprising: (1) drilling a via hole at a predetermined position of a double-sided flexible copper-clad board, performing a black hole treatment on the via hole, and then copper-plating the hole wall of the via hole to connect the front and back sides of the double-sided flexible copper-clad board, and then copper-plating the front and back sides of the double-sided flexible copper-clad board once respectively; (2) etching coils on the front and back sides of the double-sided flexible copper-clad board respectively through an etching process, and making the coils on the front and back sides conduct through the via hole; (3) copper-plating the coils on the front and back sides respectively; (4) pressing an insulating film on the outside of the product obtained in step (3) and then processing it through a later process to obtain the flexible circuit board. The manufacturing method achieves the high requirement of low copper plating tolerance by slowly plating copper multiple times (reducing current density), and the efficiency of the etching process is improved by 2.5-3 times compared with the conventional etching method.

Description

Technical Field

[0001] The present invention relates to a flexible circuit board for wireless charging and a manufacturing method and application thereof, belonging to the technical field of printed circuit board manufacturing. Background Art

[0002] With the rapid development of electronic devices, the trend of terminal products being light, thin, short and small is irreversible. More dense wiring and more stringent volume requirements have brought new challenges to the entire circuit board industry. Flexible printed circuits (FPC) are in line with the future development direction of the circuit board industry. They have the characteristics of high wiring density, small size, light weight, and resistance to bending, so they are favored by emerging electronic products, and wireless chargers for mobile phones are one of them.

[0003] Currently, wireless charging of mobile phones is mainly achieved through electromagnetic induction, and the induction coil used to transmit electrical energy is made of flexible circuit boards. The resonance of the primary and secondary coils is the main principle for achieving wireless charging, so the coil is the main carrier. There are two forms of coils: one is made by directly winding copper wire, but the winding coil is highly dependent on equipment. At present, the relevant technology is mainly monopolized by foreign countries, which is not conducive to practical application in China; the other is made through FPC etching process.

[0004] The main issue to be considered in FPC wireless charging is charging efficiency, i.e. fast charging. In order to achieve fast charging requirements, there must be stricter requirements on the relevant performance of the coil, such as high inductance, low resistance, low tolerance (about ±15um) and ultra-thin (current trend of lightweight requirements). In order to achieve the requirements of high inductance and low resistance, the flexible circuit board itself needs to be thicker, and the thickness of the copper plate is generally required to be above 50μm. Such a thick copper plate will cause the following problems in the production of the coil:

[0005] 1) The traditional production method requires large electroplating equipment as an aid, and such a thick copper plate will make the later copper plating tolerance difficult to control and it is easy to exceed the tolerance requirements;

[0006] 2) The etching efficiency is seriously reduced. Specifically, copper itself is thick and needs to be etched very slowly. Compared with the conventional FPC etching efficiency, the production efficiency of the coil board is reduced by about 2.5-3 times;

[0007] 3) Ultra-thinness and low resistance are contradictory to each other, and both requirements must be met just right, which is another manifestation of strict tolerance requirements.

[0008] Therefore, providing a new type of flexible circuit board for wireless charging and its manufacturing method and application has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0009] In order to solve the above-mentioned shortcomings and deficiencies, an object of the present invention is to provide a method for manufacturing a flexible circuit board for wireless charging.

[0010] Another object of the present invention is to provide a flexible circuit board for wireless charging, which is manufactured by the manufacturing method of the flexible circuit board for wireless charging described above.

[0011] Another object of the present invention is to provide an application of the above-mentioned flexible circuit board for wireless charging in wireless charging power supply.

[0012] Another object of the present invention is to provide an electronic device comprising the above-mentioned flexible circuit board for wireless charging.

[0013] In order to achieve the above objectives, on the one hand, the present invention provides a method for manufacturing a flexible circuit board for wireless charging, wherein the manufacturing method comprises:

[0014] (1) drilling a via hole at a predetermined position of the double-sided flexible copper clad laminate, performing a black hole treatment on the via hole so that the middle insulating substrate layer of the double-sided flexible copper clad laminate forms a conductor layer, then copper plating is performed on the hole wall of the via hole so that the front and back sides of the double-sided flexible copper clad laminate are connected, and then copper plating is performed once on the front and back sides of the double-sided flexible copper clad laminate respectively;

[0015] (2) etching the coils on the front and back sides of the double-sided flexible copper-clad laminate respectively through an etching process, and making the coils on the front and back sides conduct electricity through the conductive holes;

[0016] (3) copper plating is then performed on the front and back sides of the coils for a second time;

[0017] (4) After pressing an insulating film on the outside of the product obtained in step (3), the product is processed through a subsequent process to obtain the flexible circuit board for wireless charging.

[0018] As a specific implementation of the above-mentioned manufacturing method of the present invention, in step (1), the thickness of the single-sided copper foil of the double-sided flexible copper clad laminate is 9-18 μm, preferably 18 μm.

[0019] As a specific embodiment of the above-mentioned manufacturing method of the present invention, in step (1), the copper plating and the primary copper plating are slow copper plating, and the copper plating rate is 20-40 micro-inches / min.

[0020] As a specific implementation of the above-mentioned manufacturing method of the present invention, in step (1), the thickness of the single-sided copper layer plated by the first copper plating is in the range of 3-5 μm.

[0021] As a specific embodiment of the above-described production method of the present invention, in step (1), during the black hole treatment process, the carbon powder in the black hole liquid used can adhere to the intermediate insulating substrate layer (such as a polypropylene layer or a polyimide layer, etc.) of the double-sided flexible copper clad laminate, thereby forming a conductor layer in the intermediate insulating substrate layer.

[0022] As a specific implementation of the above-mentioned manufacturing method of the present invention, in step (1), copper plating can thicken the hole wall of the via hole, thereby meeting the requirement of conductive connection on both sides of the double-sided flexible copper clad laminate.

[0023] As a specific implementation of the manufacturing method described above, in step (2), the shape and parameters of the coil can be reasonably adjusted according to actual needs. In addition, the coils on both sides are connected through the conductive holes, which is equivalent to increasing the number of turns of the coil. In this way, the inductance value of the obtained flexible circuit board for wireless charging will become larger, which is more conducive to improving the charging efficiency.

[0024] As a specific embodiment of the above-mentioned production method of the present invention, in step (3), the secondary copper plating is carried out in multiple times so that the single-sided copper thickness of the product obtained in step (3) reaches 65 μm.

[0025] As a specific embodiment of the above-mentioned manufacturing method of the present invention, in step (3), the thickness of the single-sided copper layer plated each time during the secondary copper plating process is in the range of 8-20 μm.

[0026] Among them, the present invention does not make specific requirements on the specific number of secondary copper plating, and the thickness of the copper layer plated each time during the secondary copper plating process depends on the size of the residual etching area. The larger the residual copper area, the lower the single copper thickness. Using low current to slowly plate copper can ensure that there is basically no error.

[0027] As a specific embodiment of the above-mentioned manufacturing method of the present invention, in step (3), the secondary copper plating is slow copper plating, and the copper plating rate is 20-40 micro-inches / min.

[0028] As a specific embodiment of the above-mentioned manufacturing method of the present invention, the single-sided total thickness tolerance of the first copper plating in step (1) and the second copper plating in step (3) is ±2μm; the total thickness tolerance of the flexible circuit board for wireless charging is ±4μm.

[0029] Among them, the copper layer plated by the secondary copper plating in step (3) can increase the overall copper thickness, thereby meeting the resistance requirement of the flexible circuit board for wireless charging.

[0030] In addition, after the etching in step (2) is completed, half of the copper layer in the coil is etched away. In this way, after the second copper plating, the plated area is reduced by half, so that the copper plating can be completed with a lower current, and the amount of copper used for copper plating is reduced while reducing the copper plating tolerance. Although the copper plating thickness is relatively thick, the reduction in the plated area caused by the previous etching makes the final copper plating cost decrease instead of increase.

[0031] As a specific implementation of the above-mentioned manufacturing method of the present invention, the insulating film is a black insulating film.

[0032] As a specific implementation of the above-mentioned manufacturing method of the present invention, wherein the insulating film includes a polyimide film or the like.

[0033] In the present invention, the drilling of via holes, black hole processing, copper plating, etching process (or pattern transfer) and post-processing are all conventional technical means in the field, and can be reasonably operated according to actual needs on site and the raw materials used in each process and the process parameters used can be reasonably selected. For example, in some embodiments of the present invention, the etching process (or pattern transfer) can be implemented using an existing conventional etching station.

[0034] On the other hand, the present invention also provides a flexible circuit board for wireless charging made by the method for making the flexible circuit board for wireless charging described above.

[0035] On the other hand, the present invention also provides the application of the above-mentioned flexible circuit board for wireless charging in wireless charging power supply.

[0036] On the other hand, the present invention further provides an electronic device, wherein the electronic device includes the above-mentioned flexible circuit board for wireless charging.

[0037] As a specific implementation of the electronic device described above in the present invention, the electronic device includes a mobile phone and the like.

[0038] The flexible circuit board for wireless charging provided by the present invention realizes wireless charging through the energy conversion principle of electric generation of magnetism and magnetic regeneration of electricity, and can be applied to the fields of wireless charging of electronic devices such as mobile phones and radio frequency.

[0039] The existing conventional method for manufacturing flexible circuit boards usually uses a thicker copper plate, drills holes in the copper plate, copper-plates it, and then etches it. This method is costly and inefficient. Compared with the existing conventional manufacturing method, the method for manufacturing a flexible circuit board for wireless charging provided by the present invention uses a thinner double-sided flexible copper-clad laminate, drills holes in the copper plate, copper-plates it, and then etches it, and then copper-plates the etched coil for the second time. This method has high etching efficiency, low cost, and low equipment requirements, but very high manufacturing efficiency.

[0040] In summary, the beneficial technical effects that can be achieved by the method for manufacturing a flexible circuit board for wireless charging provided by the present invention include:

[0041] 1) The present invention abandons the conventional material selection method and uses thin copper to make a flexible circuit board for wireless charging, which reduces material consumption and reduces costs;

[0042] 2) The present invention optimizes the manufacturing process, that is, through slow and multiple copper plating, while not using large-scale electroplating equipment to assist in manufacturing. On the one hand, the thickness of the thin copper foil substrate is increased to meet the resistance requirements, and on the other hand, the current density is reduced, and the high requirements for low copper plating tolerance are achieved, and the thickness tolerance is more precisely controlled; specifically, the thickness tolerance of the traditional manufacturing method of thick copper plus one-time electroplating is ±15μm, while the thickness tolerance of the optimized process of thin copper plus multiple electroplating provided by the present invention can be accurate to ±4μm, and the coil performance is more superior;

[0043] 3) The present invention completes the etching process without adding etching lines, and the overall efficiency is not affected at all. However, compared with conventional etching methods, the efficiency of the etching process is improved by 2.5-3 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 It is a schematic diagram of drilling a via hole in Embodiment 1 of the present invention.

[0046] Figure 2 It is a schematic diagram of copper plating on the hole wall of the via hole in Example 1 of the present invention.

[0047] Figure 3 Schematic diagram of a coil obtained after etching the coil on both the front and back sides of a double-sided flexible copper clad laminate through an etching process in Example 1 of the present invention.

[0048] Figure 4 This is a schematic diagram of the second copper plating in Example 1 of the present invention.

[0049] Figure 5 This is a schematic diagram of pressing a black polyimide film on the outside of the product obtained in step (3) in Example 1 of the present invention.

[0050] Figure 6 This is a schematic diagram of the finished flexible circuit board for wireless charging prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0051] It should be noted that the term "comprises" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0052] In the present invention, the terms "upper", "front", "reverse", "middle", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit the indicated devices, elements, or components to have a specific orientation, or to be constructed and operated in a specific orientation. Moreover, in addition to being used to indicate orientations or positional relationships, some of the above terms may also be used to indicate other meanings. For example, the term "upper" may also be used to indicate a certain dependency or connection relationship in certain circumstances. For those of ordinary skill in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0053] "Scope" disclosed in the present invention is given in the form of lower limit and upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges defined in this way are combinable, i.e. any lower limit can be combined with any upper limit to form a range. For example, for a specific parameter, a range of 60-120 and 80-110 is listed, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​listed are 1 and 2, and the maximum range values ​​listed are 3, 4 and 5, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0054] In the present invention, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in the present invention, and "0-5" is just an abbreviation of these numerical combinations.

[0055] In the present invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0056] In the present invention, unless otherwise specified, all technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0057] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment. The following described embodiment is a part of the present invention, rather than all embodiments, and is only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the embodiment, it is carried out according to the normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0058] Example 1

[0059] This embodiment provides a method for manufacturing a flexible circuit board for wireless charging, wherein the manufacturing method specifically includes:

[0060] (1) Drill multiple via holes at predetermined positions on a double-sided flexible copper-clad laminate (outer layer is copper foil, middle layer is polyimide substrate, and middle layer thickness is 12.5 μm) with a copper foil thickness (single side) of 18 μm. The size range of via holes is 0.15-0.2 mm, specifically 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, and 0.2 mm, etc. Figure 1 As shown, the via hole is black-hole treated to form a conductor layer on the middle insulating substrate layer of the double-sided flexible copper-clad laminate, and then copper is plated on the hole wall of the via hole to connect the front and back sides of the double-sided flexible copper-clad laminate. Figure 2 As shown, copper plating is performed on both the front and back sides of the double-sided flexible copper clad laminate;

[0061] In step (1), the black hole treatment liquid contains carbon powder (such as graphite) and the solid concentration is 3wt%;

[0062] In step (1), the copper plating and the first copper plating are both slow copper plating, and the copper plating rate is 30 microinches / min;

[0063] In step (1), the thickness of the single-sided copper layer plated by the copper plating is in the range of 5 μm;

[0064] (2) Etching the coils on both sides of the double-sided flexible copper clad laminate by etching process, such as Figure 3 As shown, the coils on the front and back sides are connected through the conducting holes;

[0065] (3) Then perform secondary copper plating on the front and back sides of the coil, such as Figure 4 As shown, the secondary copper plating is performed in four steps, and the thickness of the single-sided copper layer plated each time is 15 μm, 17 μm and 10 μm respectively, so that the single-sided copper thickness of the product obtained in step (3) reaches 65 μm;

[0066] In step (3), the secondary copper plating is also slow copper plating, and the copper plating rate is 30 microinches / min;

[0067] The single-sided total thickness tolerance of the primary copper plating in step (1) and the secondary copper plating in step (3) is ±2 μm; the total thickness tolerance of the flexible circuit board for wireless charging is ±4 μm, that is, the total thickness of the product obtained in step (3) is 142.5±4 μm;

[0068] (4) Pressing a black polyimide film (such as Figure 5 As shown in FIG. 1 ), the finished product of the flexible circuit board for wireless charging is obtained by a subsequent process, such as Figure 6 As shown;

[0069] The thickness of the black polyimide film is 7.5 μm, and the thickness of the adhesive layer used to bond the black polyimide film and the copper material is 5 μm.

[0070] Comparative Example 1

[0071] This comparative example provides a method for manufacturing a conventional flexible circuit board, wherein the manufacturing method specifically includes:

[0072] (1) Drilling a plurality of via holes at predetermined positions of a double-sided flexible copper-clad laminate (outer layer is copper foil, middle layer is polyimide substrate, and middle layer thickness is 12.5 μm) with a copper foil thickness (single side) of 50 μm, with a size range of 0.15-0.2 mm, specifically 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, and 0.2 mm, etc.;

[0073] (2) copper plating is performed on the front and back sides of the double-sided flexible copper-clad laminate by a conventional direct copper plating method, and the thickness of the plated single-layer copper is 15±5 μm, so that the total copper thickness of the single side of the product obtained in step (2) reaches 65 μm±5 μm, and the total copper thickness of the double sides is 130±10 μm. The total thickness of the product obtained in step (2) is 142.5±10 μm;

[0074] (3) Then, patterns are made on the front and back sides of the double-sided flexible copper-clad laminate by means of coating-development-etching (collectively referred to as DES), and then the excess copper is etched away;

[0075] (4) pressing a black polyimide film on the outside of the product obtained in step (3) and then subjecting the product to a subsequent process to obtain the conventional flexible circuit board product;

[0076] The thickness of the black polyimide film is 7.5 μm, and the thickness of the adhesive layer used to bond the black polyimide film and the copper material is 5 μm.

[0077] Test Example 1

[0078] In this test example, the charging device equipped with the flexible circuit boards prepared in Example 1 and Comparative Example 1 was used to test the charging of the mobile phone. The test results showed that:

[0079] For the charging device installed with the traditional flexible circuit board, that is, the flexible circuit board prepared in comparative example 1, the charging efficiency obtained by wireless charging at a distance of 5V self-flowing voltage and 0 is generally 150 mA, and the current obtained at a distance of 5mm is 109-120 mA; while when the mobile phone is charged by the charging device installed with the flexible circuit board for wireless charging prepared in embodiment 1 of the present invention, the charging efficiency obtained by wireless charging at a distance of 5V self-flowing voltage and 0 can reach 150.6-151.3 mA, and the current obtained at a distance of 5mm reaches 118-130 mA, which indicates that the performance of the flexible circuit board coil for wireless charging provided in the embodiment of the present invention is more superior.

[0080] The existing conventional method for manufacturing flexible circuit boards usually uses a thicker copper plate, drills holes in the copper plate, copper-plates it, and then etches it. This method is costly and inefficient. Compared with the existing conventional manufacturing method, the method for manufacturing a flexible circuit board for wireless charging provided by the present invention uses a thinner double-sided flexible copper-clad laminate, drills holes in the copper plate, copper-plates it, and then etches it, and then copper-plates the etched coil for the second time. This method has high etching efficiency, low cost, and low equipment requirements, but very high manufacturing efficiency.

[0081] In summary, the beneficial technical effects that can be achieved by the method for manufacturing a flexible circuit board for wireless charging provided by the present invention include:

[0082] 1) The present invention abandons the conventional material selection method and uses thin copper to make a flexible circuit board for wireless charging, which reduces material consumption and reduces costs;

[0083] 2) The present invention optimizes the manufacturing process, that is, through slow and multiple copper plating, while not using large-scale electroplating equipment to assist in manufacturing. On the one hand, the thickness of the thin copper foil substrate is increased to meet the resistance requirements, and on the other hand, the current density is reduced, and the high requirements for low copper plating tolerance are achieved, and the thickness tolerance is more precisely controlled; specifically, the thickness tolerance of the traditional manufacturing method of thick copper plus one-time electroplating is ±15μm, while the thickness tolerance of the optimized process of thin copper plus multiple electroplating provided by the present invention can be accurate to ±4μm, and the coil performance is more superior;

[0084] 3) The present invention completes the etching process without adding etching lines, and the overall efficiency is not affected at all. However, compared with conventional etching methods, the efficiency of the etching process is improved by 2.5-3 times.

[0085] The above is only a specific embodiment of the present invention, and cannot be used to limit the scope of the invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the protection scope of the patent of the present invention, should still fall within the scope of this patent. In addition, the technical features of the present invention can be freely combined with each other, with each other and with each other, and with each other.

Claims

1. A method for manufacturing a flexible circuit board for wireless charging, characterized in that: The production method comprises: (1) drilling a via hole at a predetermined position of the double-sided flexible copper clad laminate, performing a black hole treatment on the via hole so that the middle insulating substrate layer of the double-sided flexible copper clad laminate forms a conductor layer, then copper plating is performed on the hole wall of the via hole so that the front and back sides of the double-sided flexible copper clad laminate are connected, and then copper plating is performed once on the front and back sides of the double-sided flexible copper clad laminate respectively; In step (1), the thickness of the single-sided copper foil of the double-sided flexible copper-clad laminate is 18 μm, the copper plating and the first copper plating are slow copper plating, the copper plating rate is 20-40 microinches / min, and the thickness of the single-sided copper layer plated by the first copper plating is in the range of 3-5 μm; (2) etching the coils on the front and back sides of the double-sided flexible copper-clad laminate respectively through an etching process, and making the coils on the front and back sides conduct electricity through the conductive holes; (3) performing secondary copper plating on the front and back sides of the coil respectively; the secondary copper plating is performed in multiple times so that the single-sided copper thickness of the product obtained in step (3) reaches 65 μm, and the thickness of the single-sided copper layer plated each time during the secondary copper plating process ranges from 8 to 20 μm. In step (3), the secondary copper plating is slow copper plating, and the copper plating rate is 20 to 40 microinches / min; (4) pressing an insulating film on the product obtained in step (3) and then subjecting the product to subsequent processing to obtain the flexible circuit board for wireless charging; The single-sided total thickness tolerance of the primary copper plating in step (1) and the secondary copper plating in step (3) is ±2 μm; the total thickness tolerance of the flexible circuit board for wireless charging is ±4 μm.

2. The method according to claim 1, characterized in that: The insulating film is a black insulating film.

3. The method according to claim 2, characterized in that: The insulating film includes a polyimide film.

4. A flexible circuit board for wireless charging made by the method for making a flexible circuit board for wireless charging according to any one of claims 1 to 3.

5. Application of the flexible circuit board for wireless charging as claimed in claim 4 in wireless charging power supply.

6. An electronic device, characterized in that: The electronic device includes the flexible circuit board for wireless charging according to claim 5.

7. The electronic device according to claim 6, characterized in that: The electronic device includes a mobile phone.

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