Flexible circuit connection device, connection method and method for protecting flexible circuit board

Abstract

The present invention provides a flexible circuit connection device, which is connected to a device with a hard shell, and further includes a flexible substrate and a conductor layer; the local bending strength of the flexible circuit connection device at the location where the device with the hard shell is connected is greater than the local bending strength at the location away from the device with the hard shell. When the flexible circuit connection device provided by the present invention is fixedly connected to the device with the hard shell, it can bend with a uniform curvature under the action of an external force, without excessive bending points, thereby increasing the service life and reducing the rework rate. The present invention also provides a method for connecting a flexible circuit board and a method for protecting a flexible circuit board.

Description

Technical Field

[0001] The invention relates to a flexible circuit connection device, a connection method and a method for protecting a flexible circuit board. Background Art

[0002] Flexible printed circuit (FPC) is a type of printed circuit board that is flexible and is also called soft board. Flexible printed circuit boards are popular in the market for their high reliability and excellent flexibility. They are also lightweight and small in size. They can also be bent into various shapes and designed into complex three-dimensional structures, and are widely used.

[0003] Flexible circuit connection devices are used in situations where they must be bendable or where they need to remain bent for a long time. Before the invention of flexible circuit boards, people used wire interconnection to achieve this. Since flexible circuit boards include not only single-sided flexible circuits, but also double-sided and multi-layer flexible circuits, flexible circuit connection devices can combine several circuit components or devices with complex interconnections.

[0004] In the magnetic resonance system of large medical diagnostic equipment, the surface coil needs to cover or surround the surface of the human body during imaging, so a flexible circuit board must be used. The magnetic resonance surface coil is a tuning component welded on a flexible circuit board, and a corresponding hard shell is fixed on the flexible circuit board to protect the tuning component inside, and then the magnetic resonance signal is led out through a connecting cable. These tuning components need a flexible circuit connection device to connect.

[0005] In the practice of diagnosing magnetic resonance systems, it is found that the flexible circuit connection device is easily damaged at the local position of the hard shell that protects the tuning components, and the repair rate is relatively high. This is because the flexible circuit connection device is deformed by external forces during use, and the local deformation is greater at the fixed hard shell.

[0006] There are many uses for connecting rigid devices with flexible circuits in daily life, such as in printing heads and in virtual reality audio-visual equipment. Summary of the invention

[0007] In order to solve the existing problem of high rework rate, the present invention provides a flexible circuit connection device, a connection method and a method for protecting a flexible circuit board.

[0008] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0009] A flexible circuit connection device is connected to a device with a hard shell, further comprising a flexible substrate and a conductor layer; the bending strength of the flexible circuit connection device at a local position connected to the device with the hard shell is greater than the bending strength at a local position away from the device with the hard shell.

[0010] In one embodiment of the present invention, the thickness of the flexible circuit connection device at a local position connected to the device with a hard shell is greater than the thickness at a local position away from the device with a hard shell.

[0011] Preferably, the thickness of the flexible substrate varies in the length direction of the flexible circuit board, and is the thickest at a portion where the flexible circuit connection device connects to the device having a hard housing.

[0012] Preferably, the flexible substrate has multiple layers, and the number of layers of the substrate changes in the length direction of the flexible circuit connection device, with the largest number of layers at a location where the flexible circuit connection device is connected to the device with a hard housing.

[0013] Preferably, the flexible substrate is cut on a plane and a partial area is subtracted from a partial thickness, and the subtracted area is smallest at a portion connected to the device with a hard housing.

[0014] In one embodiment of the present invention, an insulating film component with adjustable thickness is attached to the surface of the flexible circuit connecting device, and the width of the insulating film component with adjustable thickness at a local position connecting the device with a hard shell is greater than the width at a local position away from the device with a hard shell.

[0015] Preferably, the thickness-adjustable insulating film component has a greater bending strength than the flexible circuit connection device.

[0016] Preferably, the planar shape of the thickness-adjustable insulating film component is a triangle, or more than one triangle arranged in parallel, and one side of the triangle is located at a position where the flexible circuit connecting device is connected to the device with a hard casing.

[0017] The present invention also provides a flexible circuit connection method, which uses any one of the above-mentioned flexible circuit connection devices and then fixes the device to a device with a hard shell.

[0018] The present invention also provides a method for protecting a flexible circuit board, which is used for connecting a device with a hard shell; the method comprises: firstly attaching an insulating film component with adjustable thickness on the surface of the flexible circuit board, and then fixing the device with the hard shell on the flexible circuit board; the insulating film component with adjustable thickness has the largest width at the portion connected to the device with the hard shell, and the width gradually decreases in the direction away from the device with the hard shell.

[0019] Preferably, the insulating film component with adjusted thickness has a greater bending strength than the flexible circuit connecting device.

[0020] The beneficial effects of the present invention are: providing a flexible circuit connection device, a connection method and a method for protecting a flexible circuit board, because the local position of the connection of the flexible circuit board has the greatest anti-bending strength, the curvature of the deformation in the working state is relatively uniform, and there is no excessive bending point, which reduces the rework rate of the flexible circuit connection device and increases the service life of the flexible circuit connection device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a schematic diagram of the structure of a flexible circuit board of a magnetic resonance surface coil.

[0022] Figure 2 The present invention is a schematic diagram of the cross-sectional structure of a flexible circuit connection device connected to a device with a hard housing.

[0023] Figure 3 and Figure 4 They are schematic cross-sectional views of embodiments of a flexible circuit connection device of the present invention connected to a device with a hard housing.

[0024] Figure 5 and Figure 6 , Figure 7 They are three-dimensional structural schematic diagrams of another embodiment of a device in which a flexible circuit connection device of the present invention is connected to a hard housing.

[0025] Figure 8 and Fig. 9 It is a schematic diagram of the design of the anti-bending test of the flexible circuit connection device of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings. The implementation of the present invention is not limited to the embodiments described below, and can also be implemented in many different forms. The purpose of providing the following embodiments is to facilitate a more thorough and comprehensive understanding of the content disclosed in the present invention.

[0027] It should be noted that, when the present specification describes an original being "fixed" to another original, it means that the original is directly on the other original, or there are other intermediate originals in between; when the present specification describes an element being "connected" to another element, it means that the original is directly connected to the other element, or there are intermediate elements in between.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. The terms used herein are only for describing specific embodiments and are not intended to limit the present invention.

[0029] Flexible circuit boards can be divided into single-sided boards, double-sided boards, multi-sided boards, etc. Taking a three-layer flexible copper-clad circuit board as an example, its structure includes copper metal foil, insulating foil and insulating film. Copper metal foil is attached to the surfaces of both sides of the insulating foil, and insulating film is attached to the surface of the copper metal foil, and is formed by hot pressing with an intermediate layer adhesive. Among them, copper foil generally includes rolled copper foil and electrolytic copper foil, and its elongation at break can reach about 10% and 4% respectively; in particular, copper foil prepared by the rolling method has good electrical and mechanical properties and good toughness. The flexural resistance of high-precision rolled copper foil (thickness size is generally below 20μm) can reach tens of thousands or even hundreds of millions of times. Insulating film and insulating foil generally use materials such as polyester film and polyimide film, and usually select materials with good dielectric properties, chemical resistance and low moisture absorption, as well as good dimensional stability and thermal stability. The main interlayer adhesives are epoxy resin, acrylate resin, etc. The intermediate layer adhesive is used to bond the conductive copper metal foil to the insulating film, and plays an important role in the heat resistance, chemical resistance and dielectric properties of the flexible version.

[0030] The flexible circuit connection device referred to in the present invention is an application mode of a flexible circuit board, which means that the flexible circuit board is used to connect between devices or components, especially between devices or components with a hard shell. The flexible substrate in this article refers to the middle layer of the flexible circuit board, that is, the insulating foil layer.

[0031] From the materials used to make flexible circuit boards, it can be seen that their plasticity and fatigue resistance are very good, but when the flexible circuit connection device is connected to a device or component with a hard surface, the rework rate is very high. This is because although the flexible circuit board has good plasticity, the deformation it bears cannot be less than its inherent minimum bending radius. When the deformation of the flexible circuit board is less than its inherent minimum bending radius, the flexible circuit board will be damaged or its performance will be degraded due to excessive bending. When the flexible circuit board is fixed to a device or component with a hard shell, the edge of the hard shell becomes the position where the flexible circuit board is most severely deformed by external force, and becomes the most severely bent part of the circuit board, causing the electrical performance of the flexible circuit board to be damaged and need to be returned to the factory for repair. The flexible circuit connection device and its hard shell device are often bent repeatedly during use, and the deformation borne by the hard shell often exceeds the minimum bending radius, resulting in bending damage, so the rework rate is very high.

[0032] Under the same external force, the plate material with high bending strength has a larger bending radius, and the plate material with low bending strength has a smaller bending radius. Therefore, the plate material with low bending strength is softer. For the same plate material, the greater the thickness, the greater the bending strength, and the smaller the thickness, the smaller the bending strength.

[0033] like Figure 1 The figure shows a schematic diagram of the structure of a flexible circuit board of a surface coil, wherein the flexible circuit board 20 is located on the surface coil housing 10, and the figure includes a hard housing 50 fixed on the flexible circuit board 20; the figure does not show the components contained in the hard housing 50 and electrically connected to the circuit board. Figure 1 As shown, the welding points of the lead-out cable 71 are also protected inside a hard shell.

[0034] like Figure 1 In the figure, the thickness of the surface coil housing 10 and the flexible circuit board 20 is thinner than that of the hard housing 50. The hard housing 50 fixed on the flexible circuit board is distributed on the flexible circuit board 20 and has a variety of different shapes; the part where the flexible circuit board and the hard housing are fixed together is no longer flexible. The flexible circuit board located between two adjacent hard housings is a flexible circuit connection device. The surface coil needs to be bent during use to attach to the patient's body part, wherein the repeated deformation of the local position of the flexible circuit board 20 relative to the hard housing 50 will affect the performance of the local area, causing the surface coil to malfunction and need to be returned to the factory for repair.

[0035] One solution is to place a flexible substrate between the contact surface of the hard shell and the flexible circuit board so that the hard shell does not directly contact the flexible circuit board. The cross-sectional structure diagram is as follows: Figure 2 As shown, in Figure 2In the figure, 201 is the cross section of the flexible circuit board, 501 is the cross section of the hard shell, and 901 is the flexible substrate added between the contact surface of the hard shell and the flexible circuit board. The flexible substrate 901 protects the contact surface between the hard shell and the flexible circuit board, but practice shows that the repair rate of the surface coil is still too high with such treatment.

[0036] When the flexible circuit connection device is connected to a device with a hard housing, the same problem of high repair rate will also occur. Therefore, we need a flexible circuit connection device that has a relatively uniform curvature and a large curvature when it is bent under force in the working state.

[0037] To this end, the thickness of the flexible circuit connection device of the present invention is the largest at the portion connected to the device with the hard shell, and decreases at the portion away from the device with the hard shell. The local anti-bending strength of the flexible circuit connection device can be changed by changing the local thickness. If the materials are the same, the greater the thickness, the greater the anti-bending strength. Therefore, the thickness of the flexible substrate in the flexible circuit board is changed, or a flexible substrate (insulating film) is attached to the surface of the flexible circuit board to change the thickness distribution of the flexible circuit board.

[0038] In one embodiment of the present invention, the thickness distribution of the flexible circuit board is changed by attaching an insulating film with adjustable thickness to one side surface of the flexible circuit connection device. Figure 3 The figure shows a cross-sectional structure diagram of an embodiment of a flexible circuit connection device of the present invention connected to a device with a hard shell. The flexible circuit board 203 is fixedly connected to the hard shell 503, and the flexible substrate 903 acts as an insulating film to increase the thickness of the flexible circuit board 203. Figure 3 It can be seen that in this embodiment of the present invention, the flexible substrate 903 and Figure 2 The flexible substrate 901 has a larger area than the hard shell 503 , and the entire plane of the flexible substrate 903 is evenly and flatly attached to the flexible circuit board; and its area is also attached to the part outside the hard shell 503 .

[0039] In one embodiment of the present invention, the thickness distribution of the flexible circuit board is changed by attaching insulating films to both sides of the flexible circuit board.

[0040] In one embodiment of the present invention, the thickness of the insulating film attached to the flexible circuit board gradually decreases in the length direction of the flexible circuit connection device, and the thickness is the largest at the location where the flexible circuit connection device is connected to the device or device with a hard surface. . The thickness of the flexible substrate changes in the length direction of the flexible circuit board, and the thickness is the largest at the location where the flexible circuit connection device is connected to the device with a hard shell. Figure 4The figure shows a cross-sectional structure diagram of an embodiment of a flexible circuit connection device of the present invention connected to a device with a hard shell. The flexible circuit board 204 is connected to the hard shell 504, and there is a flexible substrate 904 attached to the flexible circuit board 204. The flexible substrate 904 is an insulating film with the largest thickness at the location where the hard shell device 503 is fixed, and the thickness gradually decreases at the location away from the hard shell device 503. In this embodiment of the present invention, because the thickness of the flexible substrate 903 gradually decreases in the length direction of the flexible circuit board, its cross-sectional shape is similar to a triangle.

[0041] The above technical solution increases the local thickness of the flexible circuit board, thereby increasing the local bending strength. Under the same external force, the local deformation of the hard shell is reduced, and the probability of the deformation exceeding the minimum bending radius is reduced, thereby reducing the repair rate of the equipment.

[0042] However, in the application scenarios of flexible circuit boards, a relatively large thickness is often unacceptable. The actual demand for miniaturization calls for thinner circuit boards and more compact circuit designs.

[0043] The present invention selects an insulating film with a thickness of less than 1 mm and a specific shape to be attached to the surface of the flexible circuit board.

[0044] In one embodiment of the present invention, the insulating film attached to the surface of the flexible circuit board has a greater bending strength than that of the flexible circuit board.

[0045] In one embodiment of the present invention, the thickness distribution of the flexible circuit board is also changed by changing the ratio of the width of the insulating film attached to the surface to the width of the flexible circuit board; the plane shape of the insulating film is a triangle, or a plurality of triangles arranged in parallel (similar to a sawtooth shape), and one side of the triangle is located at the position where the flexible circuit connection device connects to the device or device with a hard surface. Therefore, when the shape of the insulating film changes in the length direction of the flexible circuit connection device, the average thickness of the flexible circuit board in the width direction gradually decreases in the length direction, and the average thickness is the largest at the position where the flexible circuit board connects to the device with a hard shell; here, the ratio of the width of the film component for adjusting the thickness to the width of the flexible circuit board is the largest at the position where the flexible circuit connection device connects to the device with a hard shell, and then gradually decreases in the length direction of the flexible circuit connection device.

[0046] like Figure 5The figure shows a three-dimensional structural schematic diagram of an embodiment of another flexible circuit connection device of the present invention connected to a device with a hard shell, wherein a flexible circuit board 205 is connected to a device 505 with a hard shell, and a flexible substrate 905 is attached to the flexible circuit board 205. In this embodiment of the present invention, the flexible substrate 905 is an insulating film shaped like a triangle, and one side of the triangle is located at the connection between the hard shell 505 and the flexible circuit board 205.

[0047] like Figure 6 The figure shows a three-dimensional structural schematic diagram of an embodiment of another flexible circuit connection device of the present invention connected to a device with a hard shell, wherein a flexible circuit board 206 is connected to a device 506 with a hard shell, and a flexible substrate 906 is attached to the flexible circuit board 206. In this embodiment of the present invention, the flexible substrate 906, as an insulating film, has a zigzag shape, similar to a plurality of triangles arranged in parallel.

[0048] exist Figure 5 or Figure 6 The angle of the triangle of the flexible substrate 905 or 906 away from the hard shell 505 or 506 is less than 60 degrees, for example, the side length of the triangle located at the hard shell is half of the height, or the side length is 3 mm and the height is 5 mm. And the corners of the triangle are rounded.

[0049] exist Figure 5 or Figure 6 The triangle of the flexible substrate 905 or the flexible substrate 906 may also be other gradually narrowing shapes, such as a funnel shape with both sides gradually narrowing and then continuing to extend for a distance, like a combination of a triangle and an elongated rectangle.

[0050] The shape of the insulating film attached to the surface of the flexible circuit board or the shape of the flexible substrate after cutting of the present invention is to change the minimum bending radius of the flexible circuit board, so that the minimum bending of the device or device attached with a hard shell is increased, while the minimum bending radius away from the device or device attached with the hard shell remains unchanged, so as to maintain its flexibility and flex resistance. The purpose of the technical solution is to change the thickness distribution of the flexible circuit connection device, change the average thickness of the flexible circuit connection device in the width direction to be the largest at the part where the flexible circuit connection device is connected to the device with a hard shell, and then gradually decrease in the length direction of the flexible circuit connection device. Therefore, cutting the shape of the flexible substrate or changing the shape of the insulating film attached to the surface of the flexible circuit board can achieve the above purpose and is within the protection scope of the present invention.

[0051] In one embodiment of the present invention, the flexible substrate has multiple layers, and the thickness distribution of the flexible circuit board is changed by changing the local number of layers of the flexible substrate; for example, the number of layers changes in the length direction of the flexible circuit board, and the number of layers is the largest at the location where the flexible circuit connection device connects to the device with a hard shell.

[0052] like Figure 7 The figure shows a three-dimensional structural schematic diagram of another embodiment of a device with a hard shell connected to a flexible circuit connection device of the present invention. The thickness distribution of the flexible circuit board is achieved by attaching an insulating film to the surface of one side of the flexible circuit board and cutting the insulating film. In the figure, 208 is an insulating film attached to the surface of the flexible circuit board, and 908 is a concave groove formed by cutting the insulating film 208. The concave groove 908 is a diamond shape, and the middle width of the concave groove 908 indicates that more insulating film 208 is cut and removed, and the two ends of the concave groove 908 gradually narrow, indicating that less insulating film 208 is cut and removed here. It can be seen that between the devices 508 with a hard shell, the average thickness of the flexible circuit board in the width direction becomes smaller, and the closer to the hard shell 508, the thicker the average thickness of the flexible circuit board in the width direction; the farther from the hard shell, the smaller the average thickness of the flexible circuit board in the width direction.

[0053] In one embodiment of the present invention, the flexible substrate of the flexible circuit board is cut and partially reduced in thickness, and the area cut and partially reduced in thickness is the smallest near the hard shell, and the farther away from the hard shell, the larger the area cut and partially reduced in thickness.

[0054] exist Figure 5 or Figure 6 The flexible substrate 905 or the flexible substrate 906 may be made of a material having a bending strength greater than that of a flexible circuit board.

[0055] Because the shape of the insulating film attached to the surface of the flexible circuit board or the shape of the flexible substrate after cutting of the present invention increases the anti-bending strength of the local position near the device fixed with the hard shell, when the flexible circuit board is subjected to the same external force, the deformation generated at the connection is reduced, and Figure 5 or Figure 6 Because the average thickness of the flexible substrate 905 or the end point of the flexible substrate 906 changes gradually (rather than suddenly), no new bending damage will be formed, and the probability of deformation exceeding the minimum bending radius on the entire flexible circuit board decreases, thereby reducing the return rate of the device. The flexible circuit board away from the device with a hard shell fixed thereon maintains its flexibility and flex resistance.

[0056] Since the average thickness of the flexible circuit board in the width direction is the largest at the portion where the flexible circuit board is connected to the device with the hard shell, and then gradually decreases in the length direction of the flexible circuit board, the thickness distribution of the flexible circuit board is changed, that is, the average thickness of the flexible circuit board at the local position of the hard shell is the thickest, and the average thickness away from the hard shell gradually decreases.

[0057] Any process of cutting the shape of the flexible substrate or changing the shape of the insulating film attached to the surface of the flexible circuit board that can achieve the above-mentioned purpose is within the protection scope of the present invention.

[0058] like Figure 8 and Fig. 9 The figure shows a schematic diagram of the bending resistance test device of the flexible circuit connection device of the present invention. In the figure, the device 500 with a hard shell connected to the end of the flexible circuit connection device 200 is fixed in position, and the end of the flexible circuit connection device 200 is connected to a counterweight 70, and the weight of the counterweight is 5KG. In the fatigue test, the counterweight 70 repeatedly falls freely, causing the flexible circuit board 200 to bend downward repeatedly.

[0059] like Figure 8 and Fig. 9 It can be seen that there are hard shell devices 500 on both sides of the flexible circuit connection device 200 , and there is a zigzag flexible substrate 906 on the flexible circuit board 200 and between the hard shells 500 .

[0060] During the project development process, the experimental data of the flexible circuit board without adding flexible substrate was compared as shown in Table 1:

[0061] Table 1:

[0062]

[0063] As an embodiment, the flexible circuit connection device of the present invention has a flexible substrate with a specific shape added at the connection between the hard shell and the flexible circuit board, so the bending strength is significantly improved. When applied to the magnetic resonance surface coil, the rework rate is greatly reduced.

[0064] When a component or device with a hard housing needs a flexible circuit connection, the method of the present invention:

[0065] First, prepare any one of the above-mentioned flexible circuit connection devices; and then fix and connect it to a device or equipment with a hard shell.

[0066] When the flexible circuit board is connected to a device or equipment with a hard shell, it is necessary to prepare any of the aforementioned flexible circuit connection devices, for example:

[0067] First, an insulating film component with adjustable thickness is attached to the surface of the flexible circuit board, and then a device with a hard shell is fixed on the flexible circuit board; the insulating film component with adjustable thickness has the largest width at the portion connected to the device with the hard shell, and its width gradually decreases in the direction away from the device with the hard shell.

[0068] or:

[0069] First, an insulating film component with adjustable thickness is attached to the surface of the flexible circuit board, and then a device with a hard shell is fixed on the flexible circuit board; the insulating film component with adjustable thickness has the largest thickness at the portion connected to the device with the hard shell, and the thickness gradually decreases in the direction away from the device with the hard shell.

[0070] The technical features of the above-mentioned embodiments can also be combined in other ways. For the sake of brevity, all possible combinations of technical features are not fully described here. It is hereby declared that as long as there is no contradiction in the combination of these technical features, they all fall within the scope of this specification.

[0071] The above embodiments specifically and in detail describe several implementation methods of the present invention, which is not a limitation on the scope of the invention patent. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention shall belong to the protection scope of the present invention, and the protection scope of the patent of the present invention shall be subject to its claims.

Claims

1. A flexible circuit connection device, connected to a device having a hard housing, further comprising a flexible substrate and a conductor layer; characterized in that: The bending strength of the flexible circuit connection device at a local position connected to the device with a hard shell is greater than the bending strength at a local position away from the device with a hard shell; The thickness of the flexible circuit connection device at a local position connected to the device with a hard shell is greater than the thickness at a local position away from the device with a hard shell; The flexible substrate has multiple layers, and the number of layers of the substrate changes in the length direction of the flexible circuit connection device, and the number of layers is the largest at the local position where the flexible circuit connection device is connected to the device with a hard shell; The flexible substrate is cut on a plane and a partial area is subtracted from a partial thickness, and the subtracted area is smallest at a local position where the device with the hard shell is connected.

2. A flexible circuit connection method, characterized in that: Using the flexible circuit connection device as claimed in claim 1; Fixedly connected to a device with a hard housing.

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