Rigid-flex printed circuit board with electromagnetic shielding film and preparation method of rigid-flex printed circuit board

Abstract

The invention provides a rigid-flex printed circuit board with an electromagnetic shielding film and a preparation method of the rigid-flex printed circuit board. The rigid-flexible combined board comprises a flexible area and a rigid area connected with the flexible area; the rigid area comprises a rigid sub-board, a bonding sheet, a flexible sub-board, a bonding sheet and a rigid sub-board which are stacked in sequence; the flexible area comprises an electromagnetic shielding film, a covering film, a flexible daughter board, a covering film and an electromagnetic shielding film which are stacked in sequence; the electromagnetic shielding film comprises a conductive adhesive layer, a metal layer and an insulating layer which are sequentially stacked. The metal layer has a concave-convex structure. According to the invention, by adjusting the selection of the electromagnetic shielding film material, the interlayer binding force of the rigid-flexible combined board is improved, and the erosion phenomenon possibly occurring after the flexible area is laminated with the electromagnetic shielding film is avoided; and the preparation method avoids the problems of burrs, electromagnetic shielding film breakage and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of printed circuit boards and relates to a rigid-flexible board, in particular to a rigid-flexible board with an electromagnetic shielding film and a preparation method thereof. Background Art

[0002] With the rapid development of the electronics industry, electronic products are further developing towards miniaturization, lightness, and high-density assembly, which has greatly promoted the development of flexible circuit boards, thereby realizing the integration of component devices and wire connections. Circuit boards (circuit boards, PCB boards) can be widely used in mobile phones, LCD displays, communications, aerospace and other industries.

[0003] Driven by the international market, functional circuit boards dominate the circuit board market, and an important indicator of functional circuit boards is electromagnetic (wave) shielding (EMI Shielding). With the integration of functions of mobile phones and other communication devices, components are rapidly becoming high-frequency and high-speed. For example, in addition to the original audio transmission function, the camera function has become a necessary function of mobile phones. WLAN, GPS and Internet functions have become popular. With the integration of future sensor components, the trend of rapid high-frequency and high-speed components is even more inevitable. Under the drive of high frequency and high speed, the electromagnetic interference inside and outside the components, as well as the attenuation of signals during transmission, that is, insertion loss and jitter problems, will gradually become more serious.

[0004] The shielding effect of existing circuit boards, especially rigid-flex circuit boards, cannot meet the requirements of product functions. Most of the existing electromagnetic shielding methods are bonding shielding of copper foil or aluminum foil: the dedicated electromagnetic wave shielding film needs to be laid separately by the final processor, resulting in low efficiency and high cost.

[0005] CN 102378470A discloses a flexible circuit board with an electromagnetic shielding layer, comprising a shielding layer, a separation layer, and a flexible printed circuit board; the separation layer is arranged between the shielding layer and the flexible printed circuit board; the flexible circuit board provided by the patent can shield electromagnetics and resist electromagnetic interference, the circuit of the printed circuit board is not easy to break, and the bending times of the printed circuit board can be increased; at the same time, a separation layer is arranged between the flexible circuit board and the shielding layer, which can prevent the shielding layer from damaging the flexible circuit board during the bending process. However, the patent is only applicable to flexible circuit boards, and it is difficult to ensure the shielding effect for rigid-flexible circuit boards.

[0006] CN 1774959A discloses an electromagnetic interference shield for a printed circuit board, which may include an internal network of grounded conductive elements that may be coupled to an EMI shield mounted on the printed circuit board. The network of grounded conductive elements may be coupled to a ground layer and an EMI shield, and improved EMI shielding is provided by the volume of the printed circuit board below the electronic components mounted on the printed circuit board. The electromagnetic interference shield for a printed circuit board disclosed in the patent requires a final processor to perform separate laying, resulting in the defects of low efficiency and high cost.

[0007] At present, the rigid-flex PCB with electromagnetic shielding film still has the problem of height difference between the flexible board and other parts after covering the shielding film during the preparation process. After pressing according to the conventional process, there is a risk of pressure loss and delamination. If conventional mechanical molding is used, the shielding film is prone to burrs, cracks, and falling off. Compared with conventional rigid-flex PCB, the process is more complicated and the production cost is higher.

[0008] In summary, it is necessary to provide a preparation method to improve the processing capability of shielding film products on the flexible area of ​​rigid-flex boards, so as to facilitate market promotion and development. Summary of the invention

[0009] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a rigid-flexible board with an electromagnetic shielding film and a preparation method thereof. The present invention improves the interlayer bonding strength of the rigid-flexible board by adjusting the selection of the electromagnetic shielding film material, avoiding the erosion phenomenon that may occur after the flexible area is laminated with the electromagnetic shielding film; and the preparation method avoids the problems of burrs, electromagnetic shielding film rupture, etc.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a rigid-flexible board with an electromagnetic shielding film, wherein the rigid-flexible board comprises a flexible region and a rigid region connected to the flexible region;

[0012] The rigid region includes a rigid sub-board, a bonding sheet, a flexible sub-board, a bonding sheet and a rigid sub-board stacked in sequence;

[0013] The flexible region includes an electromagnetic shielding film, a cover film, a flexible sub-board, a cover film and an electromagnetic shielding film stacked in sequence;

[0014] The electromagnetic shielding film comprises a conductive adhesive layer, a metal layer and an insulating layer stacked in sequence;

[0015] The metal layer has a concavo-convex structure.

[0016] In the present invention, the adhesion between the layers of the electromagnetic shielding film is further improved by providing a metal layer with a concave-convex structure, thereby avoiding the erosion problem that may occur in the subsequent lamination process.

[0017] As a preferred technical solution of the present invention, the thickness of the conductive adhesive layer is 2 to 3 μm, for example, it can be 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm or 3 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0018] Preferably, the resistance of the conductive adhesive layer is ≤1Ω, for example, it can be 1Ω, 0.9Ω, 0.8Ω, 0.7Ω, 0.6Ω, 0.5Ω or 0.4Ω, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, the thickness of the metal layer is 0.5-1.5 μm, for example, 0.5 μm, 0.7 μm, 0.9 μm, 1.1 μm, 1.3 μm or 1.5 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] Preferably, the material of the metal layer includes copper or nickel.

[0021] Preferably, the thickness of the insulating layer is 8-10 μm, for example, 8 μm, 8.4 μm, 8.8 μm, 9.2 μm, 9.6 μm or 10 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0022] Preferably, the insulating layer is made of epoxy resin or polyurethane resin.

[0023] As a preferred technical solution of the present invention, the flexible sub-board includes a single-layer flexible board or a multi-layer flexible board.

[0024] Preferably, the rigid sub-board includes a single-layer rigid board or a multi-layer rigid board.

[0025] Preferably, the conductive adhesive layer of the electromagnetic shielding film is close to the flexible sub-board.

[0026] In a second aspect, the present invention provides a method for preparing a rigid-flexible board having an electromagnetic shielding film as provided in the first aspect, the preparation method comprising the following steps:

[0027] (1) Pasting a cover film on the flexible area of ​​the flexible sub-board, pasting an electromagnetic shielding film after one lamination and one baking, and performing a slitting process, a hole opening process, a browning process, a baking process, and a third lamination in sequence after a second lamination and a second baking;

[0028] (2) The adhesive sheet and the rigid sub-board are sequentially attached to the rigid area of ​​the flexible sub-board, and then lamination and post-processing are sequentially performed to obtain the rigid-flexible board with the electromagnetic shielding film.

[0029] In the present invention, the flexible region is firstly manufactured to achieve the bonding of the electromagnetic shielding film; and then the rigid region is manufactured to achieve the final lamination of each layer to obtain a rigid-flexible board with an electromagnetic shielding film. The preparation method provided by the present invention has a simple process, and by optimizing the preparation method, the problems of burrs, electromagnetic shielding film rupture, etc. that may occur during the preparation process are avoided.

[0030] As a preferred technical solution of the present invention, the difference between the single-sided dimension of the electromagnetic shielding film in step (1) and the single-sided dimension of the rigid-flexible bonding baseline is 0.15 to 0.25 mm, for example, it can be 0.15 mm, 0.17 mm, 0.19 mm, 0.21 mm, 0.23 mm or 0.25 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] Preferably, the rigid-flexible combination reference line is the coincidence line of the rigid area and the flexible area.

[0032] It is worth noting that the single-side dimension of the electromagnetic shielding film in the present invention is smaller than the single-side dimension of the rigid-flexible bonding reference line.

[0033] Preferably, the spacing between the ground welding pad and the adjacent wire body in the flexible sub-board is ≥0.3mm, for example, it can be 0.3mm, 0.32mm, 0.34mm, 0.36mm, 0.38mm or 0.4mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the single board overlapping size of the window area of ​​the covering film and the ground welding pad in the flexible sub-board is ≥0.2mm, for example, it can be 0.2mm, 0.21mm, 0.22mm, 0.23mm, 0.24mm, 0.25mm or 0.26mm, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] It is worth noting that the present invention avoids the short circuit phenomenon of the circuit board caused by sticking the electromagnetic shielding film by strictly controlling the size design of the window area of ​​the electromagnetic shielding film and the covering film in step (1) during the preparation process, thereby improving the yield of the rigid-flexible board with the electromagnetic shielding film.

[0036] Preferably, the distance between the anti-foolproof alignment point of the electromagnetic shielding film in step (1) and the boundary line of the flexible area is ≥1mm, for example, it can be 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm or 1.5mm, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the spacing between the anti-mistake alignment point of the electromagnetic shielding film in step (1) and the rigid-flex bonding baseline is ≥0.6mm, for example, it can be 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm or 1.1mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] It is worth noting that the rigid-flexible combination reference line described in the present invention is: the boundary line between the rigid area and the flexible area, which is used to distinguish the rigid area from the flexible area.

[0039] As a preferred technical solution of the present invention, the temperature of the secondary pressing is 175-185°C, for example, it can be 175°C, 177°C, 179°C, 181°C, 183°C or 185°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] Preferably, the secondary pressing time is 160 to 200 seconds, for example, 160 seconds, 170 seconds, 180 seconds, 190 seconds or 200 seconds, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, the secondary pressing pressure is 16-20 kg / cm 2 , for example, it can be 16kg / cm 2 、17kg / cm 2 、18kg / cm 2 、19kg / cm 2 or 20kg / cm 2 , but not limited to the listed values, other values ​​not listed within the numerical range are also applicable.

[0042] In the present invention, the purpose of the secondary pressing is to fix the flexible sub-board and the electromagnetic shielding film; wherein, if the temperature of the secondary pressing is too high, it will make it difficult to tear off the release film of the shielding film, and if the temperature is too low, it will cause insufficient bonding between the conductive adhesive in the shielding film and the flexible sub-board; if the pressure of the secondary pressing is too high, it will make it difficult to tear off the release film of the shielding film, and if the pressure is too low, it will cause insufficient bonding between the conductive adhesive in the shielding film and the flexible sub-board.

[0043] It is worth noting that the release film on the surface of the electromagnetic shielding film can be torn off after the secondary baking in step (1) of the present invention.

[0044] As a preferred technical solution of the present invention, the cutting speed of the slitting process in step (1) is 800 to 1200 mm / s, for example, it can be 800 mm / s, 900 mm / s, 1000 mm / s, 1100 mm / s or 1200 mm / s, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] Preferably, the pulse frequency of the slitting process in step (1) is 1000-1500kHz, for example, it can be 1000kHz, 1100kHz, 1200kHz, 1300kHz, 1400kHz or 1500kHz, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0046] Preferably, the power coefficient of the slitting process in step (1) is 15 to 30 W, for example, 15 W, 18 W, 21 W, 24 W, 27 W or 30 W, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0047] Preferably, the number of cutting times for the slitting process in step (1) is 6 to 15 times, for example, 6 times, 8 times, 10 times, 12 times, 14 times or 15 times, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] It is worth noting that the purpose of the slitting process in step (1) of the present invention is to shape the flexible daughter board to obtain the appearance of the circuit board to be used; wherein, if the cutting speed of the slitting process is too fast, the flexible board cannot be completely cut through, and if the cutting speed is too slow, the carbon powder on the edge of the board will be serious;

[0049] In addition, the device used for the slit processing of the present invention includes a laser machine.

[0050] As a preferred technical solution of the present invention, the temperature of the lamination treatment in step (2) is 210-230°C, for example, it can be 210°C, 214°C, 218°C, 222°C, 226°C or 230°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0051] Preferably, the pressure of the lamination treatment in step (2) is 400-500 psi, for example, 400 psi, 420 psi, 440 psi, 460 psi, 480 psi or 500 psi, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0052] Preferably, the lamination treatment time in step (2) is 3 to 4 hours, for example, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0053] As a preferred technical solution of the present invention, polytetrafluoroethylene material is provided between adjacent flexible layers in the flexible sub-board in the lamination process in step (2).

[0054] Preferably, the thickness of the polytetrafluoroethylene material is 0.1-0.15 mm, for example, 0.1 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm or 0.15 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0055] As a preferred technical solution of the present invention, in the lamination process of step (2), the sample to be laminated is arranged between the buffer materials.

[0056] Preferably, the cushioning material comprises a three-in-one cushioning material.

[0057] It is worth noting that the purpose of the lamination process in step (2) of the present invention is to achieve the combination of the rigid sub-board and the flexible sub-board to obtain a rigid-flexible composite board blank. Among them, the polytetrafluoroethylene material with a thickness of 0.1 to 0.15 mm is arranged between adjacent flexible layers to reduce the height difference between the flexible area and the rigid area, has a glue blocking effect, controls PP glue overflow, and can also protect the board surface in the flexible area, facilitating the subsequent cover removal process;

[0058] In addition, the three-in-one buffer material is provided for the purpose of: blocking glue, releasing and averaging lamination pressure, so as to improve the yield rate of the rigid-flexible board.

[0059] Preferably, the post-process production in step (2) includes acid etching, drilling treatment, plasma activation treatment, copper plating treatment, electroplating treatment, pattern plating treatment, alkaline etching treatment, outer layer AOI treatment, four-wire micro-resistance test, solder mask treatment, surface treatment, uncovering treatment, slitting treatment, glue dispensing treatment and flying probe treatment performed in sequence.

[0060] The glue spotting area of ​​the glue spotting treatment is a transition zone, the purpose of which is to improve the mechanical strength of the transition zone and increase the service life of the rigid-flexible board;

[0061] The purpose of the needle splitting process is to test the connectivity and insulation of the rigid-flexible board.

[0062] As a preferred technical solution of the present invention, the method for preparing a rigid-flexible board with an electromagnetic shielding film provided in the second aspect of the present invention comprises the following steps:

[0063] (1) Pasting a cover film on the flexible area of ​​the flexible sub-board, pasting an electromagnetic shielding film after one lamination and one baking, and performing a slitting process, a hole opening process, a browning process, a baking process, and a third lamination in sequence after a second lamination and a second baking;

[0064] In the process of pasting the electromagnetic shielding film, the difference between the single-side size of the electromagnetic shielding film and the single-side size of the rigid-flexible combination reference line is 0.15-0.25mm, the spacing between the grounding welding pad and the adjacent wire body in the flexible sub-board is ≥0.3mm; the single-board overlap size of the window area of ​​the cover film and the grounding welding pad in the flexible sub-board is ≥0.2mm;

[0065] The secondary pressing process is performed at a temperature of 175-185°C, a time of 160-200s, and a pressure of 16-20kg / cm 2 ;

[0066] The cutting speed of the slitting process is 800-1200 mm / s, the pulse frequency is 1000-1500 kHz, the power coefficient is 15-30 W, and the number of cutting times is 6-15 times;

[0067] (2) sequentially pasting an adhesive sheet and a rigid sub-board on the rigid area of ​​the flexible sub-board, and then sequentially performing lamination treatment and post-processing to obtain the rigid-flexible board with the electromagnetic shielding film;

[0068] The lamination process is performed at a temperature of 210 to 230°C, a pressure of 400 to 500 psi, and a time of 3 to 4 hours.

[0069] In the lamination process, polytetrafluoroethylene material with a thickness of 0.1 to 0.15 mm is arranged between adjacent flexible layers in the flexible sub-plate; in the lamination process, the samples to be laminated are arranged between the buffer materials.

[0070] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] (1) The present invention improves the interlayer bonding strength of the rigid-flexible board by adjusting the selection of the electromagnetic shielding film material, thereby avoiding the erosion phenomenon that may occur after the flexible area is laminated with the electromagnetic shielding film;

[0073] (2) The preparation method provided by the present invention avoids problems such as burrs and electromagnetic shielding film rupture, thereby improving the yield of the obtained product. DETAILED DESCRIPTION

[0074] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0075] Example 1

[0076] This embodiment provides a rigid-flexible board with an electromagnetic shielding film, wherein the rigid-flexible board includes a flexible region and a rigid region connected to the flexible region;

[0077] The rigid region includes a rigid sub-board, a bonding sheet, a flexible sub-board, a bonding sheet and a rigid sub-board stacked in sequence;

[0078] The flexible region includes an electromagnetic shielding film, a cover film, a flexible sub-board, a cover film and an electromagnetic shielding film stacked in sequence;

[0079] The electromagnetic shielding film comprises a conductive adhesive layer, a metal layer and an insulating layer which are stacked in sequence; the metal layer has a concave-convex structure.

[0080] The thickness of the conductive adhesive layer is 2.5 μm, and the resistance is 0.8Ω; the thickness of the metal layer is 1 μm, and the material is copper; the thickness of the insulating layer is 9 μm, and the material is epoxy resin;

[0081] The flexible sub-board is a multi-layer flexible board, the rigid sub-board is a single-layer rigid board, and the conductive adhesive layer of the electromagnetic shielding film is close to the flexible sub-board.

[0082] The method for preparing a rigid-flexible board with an electromagnetic shielding film provided in this embodiment comprises the following steps:

[0083] (1) Pasting a cover film on the flexible area of ​​the flexible sub-board, pasting an electromagnetic shielding film after one lamination and one baking, and performing a slitting process, a hole opening process, a browning process, a baking process, and a third lamination in sequence after a second lamination and a second baking;

[0084] In the process of pasting the electromagnetic shielding film, the difference between the single-side size of the electromagnetic shielding film and the single-side size of the rigid-flexible combination baseline is 0.1mm, and the spacing between the grounding welding pad and the adjacent wire body in the flexible sub-board is 0.35mm; the single-board overlap size of the window area of ​​the cover film and the grounding welding pad in the flexible sub-board is 0.2mm;

[0085] The secondary pressing temperature is 180°C, the time is 180s, and the pressure is 18kg / cm 2 ;

[0086] The cutting speed of the slitting process is 1000 mm / s, the pulse frequency is 1250 kHz, the power coefficient is 25 W, and the number of cutting times is 10;

[0087] (2) sequentially pasting an adhesive sheet and a rigid sub-board on the flexible region of the flexible sub-board, and then sequentially performing lamination and post-processing to obtain the rigid-flexible board with the electromagnetic shielding film;

[0088] The lamination process was performed at a temperature of 220°C, a pressure of 450 psi, and a time of 3.5 h.

[0089] In the lamination process, a polytetrafluoroethylene material with a thickness of 0.125 mm is arranged between adjacent flexible layers in the flexible sub-plate; in the lamination process, the samples to be laminated are arranged between the buffer materials.

[0090] Example 2

[0091] This embodiment provides a rigid-flexible board with an electromagnetic shielding film, wherein the rigid-flexible board includes a flexible region and a rigid region connected to the flexible region;

[0092] The rigid region includes a rigid sub-board, a bonding sheet, a flexible sub-board, a bonding sheet and a rigid sub-board stacked in sequence;

[0093] The flexible region includes an electromagnetic shielding film, a cover film, a flexible sub-board, a cover film and an electromagnetic shielding film stacked in sequence;

[0094] The electromagnetic shielding film comprises a conductive adhesive layer, a metal layer and an insulating layer which are stacked in sequence; the metal layer has a concave-convex structure.

[0095] The conductive adhesive layer has a thickness of 2 μm and a resistance of 1Ω; the metal layer has a thickness of 0.5 μm and is made of nickel; the insulating layer has a thickness of 8 μm and is made of polyurethane resin;

[0096] The flexible sub-board is a multi-layer flexible board, the rigid sub-board is a single-layer rigid board, and the conductive adhesive layer of the electromagnetic shielding film is close to the flexible sub-board.

[0097] The method for preparing a rigid-flexible board with an electromagnetic shielding film provided in this embodiment comprises the following steps:

[0098] (1) Pasting a cover film on the flexible area of ​​the flexible sub-board, pasting an electromagnetic shielding film after one lamination and one baking, and performing a slitting process, a hole opening process, a browning process, a baking process, and a third lamination in sequence after a second lamination and a second baking;

[0099] In the process of pasting the electromagnetic shielding film, the difference between the single-side size of the electromagnetic shielding film and the single-side size of the rigid-flexible combination baseline is 0.15mm, and the spacing between the grounding welding plate in the flexible sub-board and the adjacent wire body is 0.3mm; the single-board overlap size of the window area of ​​the cover film and the grounding welding plate in the flexible sub-board is 0.22mm;

[0100] The secondary pressing was performed at a temperature of 175°C, a time of 200 seconds, and a pressure of 16 kg / cm 2 ;

[0101] The cutting speed of the slitting process is 800m / s, the pulse frequency is 1000kHz, the power coefficient is 15W, and the number of cutting times is 15 times;

[0102] (2) sequentially pasting an adhesive sheet and a rigid sub-board on the flexible region of the flexible sub-board, and then sequentially performing lamination and post-processing to obtain the rigid-flexible board with the electromagnetic shielding film;

[0103] The lamination process was performed at a temperature of 210°C, a pressure of 400 psi, and a time of 4 hours.

[0104] In the lamination process, a polytetrafluoroethylene material with a thickness of 0.1 mm is arranged between adjacent flexible layers in the flexible sub-plate; in the lamination process, the samples to be laminated are arranged between the buffer materials.

[0105] Example 3

[0106] This embodiment provides a rigid-flexible board with an electromagnetic shielding film, wherein the rigid-flexible board includes a flexible region and a rigid region connected to the flexible region;

[0107] The rigid region includes a rigid sub-board, a bonding sheet, a flexible sub-board, a bonding sheet and a rigid sub-board stacked in sequence;

[0108] The flexible region includes an electromagnetic shielding film, a cover film, a flexible sub-board, a cover film and an electromagnetic shielding film stacked in sequence;

[0109] The electromagnetic shielding film comprises a conductive adhesive layer, a metal layer and an insulating layer which are stacked in sequence; the metal layer has a concave-convex structure.

[0110] The thickness of the conductive adhesive layer is 3 μm, and the resistance is 0.4Ω; the thickness of the metal layer is 1.5 μm, and the material is copper; the thickness of the insulating layer is 10 μm, and the material is epoxy resin;

[0111] The flexible sub-board is a single-layer flexible board, the rigid sub-board is a single-layer rigid board, and the conductive adhesive layer of the electromagnetic shielding film is close to the flexible sub-board.

[0112] The method for preparing a rigid-flexible board with an electromagnetic shielding film provided in this embodiment comprises the following steps:

[0113] (1) Pasting a cover film on the flexible area of ​​the flexible sub-board, pasting an electromagnetic shielding film after one lamination and one baking, and performing a slitting process, a hole opening process, a browning process, a baking process, and a third lamination in sequence after a second lamination and a second baking;

[0114] In the process of pasting the electromagnetic shielding film, the difference between the single-side size of the electromagnetic shielding film and the single-side size of the rigid-flexible combination baseline is 0.25mm, and the spacing between the grounding welding pad and the adjacent wire body in the flexible sub-board is 0.4mm; the single-board overlap size of the window area of ​​the cover film and the grounding welding pad in the flexible sub-board is 0.25mm;

[0115] The secondary pressing temperature is 185°C, the time is 160s, and the pressure is 20kg / cm 2 ;

[0116] The cutting speed of the slitting process is 1200 mm / s, the pulse frequency is 1500 kHz, the power coefficient is 30 W, and the number of cutting times is 6;

[0117] (2) sequentially pasting an adhesive sheet and a rigid sub-board on the flexible region of the flexible sub-board, and then sequentially performing lamination and post-processing to obtain the rigid-flexible board with the electromagnetic shielding film;

[0118] The lamination process was performed at a temperature of 230°C, a pressure of 500 psi, and a time of 3 hours.

[0119] In the lamination process, a polytetrafluoroethylene material with a thickness of 0.15 mm is arranged between adjacent flexible layers in the flexible sub-plate; in the lamination process, the samples to be laminated are arranged between the buffer materials.

[0120] Analysis of Examples 1-3 shows that the rigid-flexible board with an electromagnetic shielding film obtained by the preparation method provided by the present invention has good power supply conditions, and no burrs or electromagnetic shielding film cracks occur, and the yield of the obtained product is high.

[0121] Example 4

[0122] This embodiment provides a rigid-flexible board with an electromagnetic shielding film. The method for preparing the rigid-flexible board with an electromagnetic shielding film is different from that of Embodiment 1 only in that:

[0123] In this embodiment, the difference between the single-side dimension of the electromagnetic shielding film in step (1) and the single-side dimension of the rigid-flexible bonding baseline is adjusted to 0.1 mm.

[0124] Compared with Example 1, the rigid-flexible board provided in this embodiment has a larger single-side size during the preparation process, which causes a short circuit on the circuit board and significantly reduces the yield of the obtained product.

[0125] Example 5

[0126] This embodiment provides a rigid-flexible board with an electromagnetic shielding film. The method for preparing the rigid-flexible board with an electromagnetic shielding film is different from that of Embodiment 1 only in that:

[0127] In this embodiment, the distance between the grounding welding pad and the adjacent wire body in the flexible daughter board is adjusted to 0.1 mm.

[0128] Compared with Example 1, the spacing between the grounding welding pad and the adjacent wire body in the flexible daughter board provided in this embodiment is too small, resulting in a short circuit phenomenon in the circuit board, which greatly reduces the yield of the obtained product.

[0129] Example 6

[0130] This embodiment provides a rigid-flexible board with an electromagnetic shielding film. The method for preparing the rigid-flexible board with an electromagnetic shielding film is different from that of Embodiment 1 only in that:

[0131] In this embodiment, the temperature of the secondary pressing in step (1) is adjusted to 150°C and the pressure is adjusted to 15 kg / cm 2 .

[0132] Compared with Example 1, the temperature and pressure of the secondary pressing in the preparation method provided in this example are relatively low, resulting in insufficient bonding force between the shielding film and the flexible sub-board.

[0133] Example 7

[0134] This embodiment provides a rigid-flexible board with an electromagnetic shielding film. The method for preparing the rigid-flexible board with an electromagnetic shielding film is different from that of Embodiment 1 only in that:

[0135] In this embodiment, the temperature of the secondary pressing in step (1) is adjusted to 200°C and the pressure is adjusted to 22 kg / cm 2 .

[0136] Compared with Example 1, the temperature and pressure of the secondary pressing in the preparation method provided in this embodiment are relatively high, which makes it difficult to tear off the release film of the shielding film, thereby affecting the yield of the rigid-flex board.

[0137] Example 8

[0138] This embodiment provides a rigid-flexible board with an electromagnetic shielding film. The method for preparing the rigid-flexible board with an electromagnetic shielding film is different from that of Embodiment 1 only in that:

[0139] This embodiment omits the provision of buffer material during the lamination process described in step (2).

[0140] Compared with Example 1, the preparation method provided in this example omits the provision of a buffer material during the lamination process, resulting in delamination during the lamination process, making the resulting rigid-flex board unqualified.

[0141] Example 9

[0142] This embodiment provides a rigid-flexible board with an electromagnetic shielding film. The method for preparing the rigid-flexible board with an electromagnetic shielding film is different from that of Embodiment 1 only in that:

[0143] In this embodiment, the thickness of the polytetrafluoroethylene material disposed between adjacent flexible layers in the flexible sub-board during the lamination process is adjusted to 0.2 mm.

[0144] Example 10

[0145] This embodiment provides a rigid-flexible board with an electromagnetic shielding film. The method for preparing the rigid-flexible board with an electromagnetic shielding film is different from that of Embodiment 1 only in that:

[0146] In this embodiment, the thickness of the polytetrafluoroethylene material disposed between adjacent flexible layers in the flexible sub-board during the lamination process is adjusted to 0.05 mm.

[0147] Compared with Example 1, when the thickness of the polytetrafluoroethylene material set between adjacent flexible layers is too high (such as Example 9), delamination will occur in the overlapping area of ​​the flexible area and the rigid area, thereby affecting the yield of the rigid-flexible composite board; when the thickness of the polytetrafluoroethylene material set between adjacent flexible layers is too low (such as Example 10), the soft board in the flexible area will break.

[0148] Comparative Example 1

[0149] This comparative example provides a rigid-flexible board with an electromagnetic shielding film, and the rigid-flexible board with an electromagnetic shielding film is different from Example 1 only in that:

[0150] In this comparative example, the structure of the metal layer is adjusted to a flat plate structure, that is, the metal layer has no concave-convex structure.

[0151] The preparation method of the rigid-flex board with the electromagnetic shielding film is the same as that of Example 1.

[0152] Compared with Example 1, the structure of the metal layer is adjusted in this comparative example, resulting in erosion of the shielding film, which not only fails to achieve the shielding effect, but also affects the yield of the rigid-flexible board.

[0153] In summary, the present invention improves the interlayer bonding strength of the rigid-flexible board by adjusting the selection of the electromagnetic shielding film material, avoiding the erosion phenomenon that may occur after the flexible area is laminated with the electromagnetic shielding film; and the preparation method avoids problems such as burrs and electromagnetic shielding film rupture.

[0154] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A rigid-flex board with an electromagnetic shielding film, characterized in that: The rigid-flex board includes a flexible region and a rigid region connected to the flexible region; The rigid region includes a rigid sub-board, a bonding sheet, a flexible sub-board, a bonding sheet and a rigid sub-board stacked in sequence; The flexible region includes an electromagnetic shielding film, a cover film, a flexible sub-board, a cover film and an electromagnetic shielding film stacked in sequence; The electromagnetic shielding film comprises a conductive adhesive layer, a metal layer and an insulating layer stacked in sequence; The metal layer has a concavo-convex structure.

2. The rigid-flex board with electromagnetic shielding film according to claim 1, characterized in that: The thickness of the conductive adhesive layer is 2 to 3 μm; Preferably, the resistance of the conductive adhesive layer is ≤1Ω; Preferably, the thickness of the metal layer is 0.5 to 1.5 μm; Preferably, the material of the metal layer includes copper or nickel; Preferably, the thickness of the insulating layer is 8 to 10 μm; Preferably, the insulating layer is made of epoxy resin or polyurethane resin.

3. The rigid-flex board with electromagnetic shielding film according to claim 1, characterized in that: The flexible sub-board includes a single-layer flexible board or a multi-layer flexible board; Preferably, the rigid sub-board comprises a single-layer rigid board or a multi-layer rigid board; Preferably, the conductive adhesive layer of the electromagnetic shielding film is close to the flexible sub-board.

4. A method for preparing a rigid-flex board with an electromagnetic shielding film as claimed in any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: (1) Pasting a cover film on the flexible area of ​​the flexible sub-board, pasting an electromagnetic shielding film after one lamination and one baking, and performing a slitting process, a hole opening process, a browning process, a baking process, and a third lamination in sequence after a second lamination and a second baking; (2) The adhesive sheet and the rigid sub-board are sequentially attached to the rigid area of ​​the flexible sub-board, and then lamination and post-processing are sequentially performed to obtain the rigid-flexible board with the electromagnetic shielding film.

5. The preparation method according to claim 4, characterized in that: The difference between the single-side dimension of the electromagnetic shielding film in step (1) and the single-side dimension of the rigid-flexible bonding reference line is 0.15 to 0.25 mm; Preferably, the rigid-flexible combination reference line is the coincidence line of the rigid area and the flexible area; Preferably, the distance between the ground welding pad and the adjacent wire body in the flexible sub-board is ≥0.3mm; Preferably, the single board overlap size of the window area of ​​the cover film and the grounding welding pad in the flexible sub-board is ≥0.2 mm.

6. The preparation method according to claim 4 or 5, characterized in that: The temperature of the secondary pressing is 175-185°C; Preferably, the secondary pressing time is 160 to 200 seconds; Preferably, the secondary pressing pressure is 16-20 kg / cm 2 .

7. The preparation method according to any one of claims 4 to 6, characterized in that: The cutting speed of the slitting process in step (1) is 800 to 1200 mm / s; Preferably, the pulse frequency of the slitting process in step (1) is 1000-1500 kHz; Preferably, the power coefficient of the slitting process in step (1) is 15 to 30 W; Preferably, the number of cutting times in the slitting process in step (1) is 6 to 15 times.

8. The preparation method according to any one of claims 4 to 7, characterized in that: The temperature of the lamination process in step (2) is 210-230° C. Preferably, the pressure of the lamination process in step (2) is 400 to 500 psi; Preferably, the lamination treatment time in step (2) is 3 to 4 hours.

9. The preparation method according to any one of claims 4 to 8, characterized in that: In the lamination process of step (2), polytetrafluoroethylene material is provided between adjacent flexible layers in the flexible sub-plate; Preferably, the thickness of the polytetrafluoroethylene material is 0.1-0.15 mm.

10. The preparation method according to any one of claims 4 to 9, characterized in that: In the lamination process of step (2), the sample to be laminated is arranged between the buffer materials; Preferably, the cushioning material comprises a three-in-one cushioning material.