Shielding film pressing method for high-step rigid-flex board and application

Abstract

The invention relates to a shielding film pressing method for a high-step rigid-flex board and application, and relates to the technical field of circuit boards. The shielding film pressing method comprises the following steps: carrying out laser uncovering on a rigid-flex board after ink printing, and carrying out dispensing, curing, shielding film bonding, vacuum rapid pressing and curing on a junction area of a flexible board and a rigid board to obtain a high-step rigid-flex board. The shielding film pressing method can ensure that the shielding film is not easy to break in the pressing process, and can also ensure the signal shielding effect of the soft and hard combined area.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit boards, and in particular to a shielding film lamination method for a high-step rigid-flexible board and its application. Background Art

[0002] As consumer electronic products have increasingly stringent requirements for quality, lightness, and compactness, the application of rigid-flex boards in circuit boards is becoming more and more widespread. At present, the shielding film (including the metal layer) is laminated to the cover area of ​​the rigid-flex board. Due to the large step difference between the flexible board area and the hard board area, and the thin adhesive layer and metal layer of the shielding film material itself, there is a risk of damage to the shielding film itself during the lamination process. At the same time, after the processes of pressing, punching, baking, etc., micro cracks will appear in the metal layer of the shielding film, which will affect the shielding effect of the signal during the subsequent use of the product, thereby causing signal distortion and product failure.

[0003] Secondly, the hard-soft junction of the hard-soft combination board is prone to cracks and water vapor intrusion, which can easily cause signal leakage, leading to signal distortion and product failure.

[0004] The main structures of shielding films at present (such as Figure 1 As shown in the figure, there are: protective film, adhesive film (3-10μm), metal layer (0.2-3.5μm), insulating layer (3-20μm), carrier film, of which the protective film and carrier film will be removed during the processing, leaving only the adhesive film, metal layer and insulating layer. In general, in the high-step soft-rigid combination board, the step height between the soft board area and the hard board area will be at least ≥200μm, and the thickness of the adhesive film is only 3-10μm, which is generally impossible to completely fill and cover, to ensure that there are no bubbles after lamination (specifically as shown in the figure, the protective film and carrier film will be removed during the processing, leaving only the adhesive film, metal layer and insulating layer. Figure 2 shown).

[0005] In addition, when the silver paste conductive cloth shielding film is pasted on the cover area at the junction of the traditional soft and hard combination board, the gap between the soft board area and the hard board area is large. In the process of pasting the shielding film, there is a risk of damage to the shielding film (for example, Figure 3 As shown in the figure, and due to the demand for high-frequency products, the frequency of electromagnetic signals is getting higher and higher, resulting in higher and higher requirements for shielding. Some researchers have proposed to use a method of changing the stacking structure to achieve the shielding method of the soft-rigid combination board, specifically using the soft board layer as the shielding layer in the inner layer area. However, this special product design is not applicable to soft-rigid combination boards with board thickness requirements or high steps. Summary of the invention

[0006] In view of the above problems, the present invention provides a shielding film pressing method for a high-step soft-hard combination board, which can ensure that the shielding film is not prone to breakage during the pressing process, while also ensuring the signal shielding effect of the soft-hard combination area.

[0007] In order to achieve the above-mentioned purpose, the present invention provides a shielding film lamination method for a high-step soft-hard combination board, comprising the following steps: laser peeling the soft-hard combination board after ink printing, dispensing glue on the interface area between the soft board and the hard board, curing, laminating the shielding film, vacuum fast pressing, curing, and obtaining a high-step soft-hard combination board.

[0008] In view of the above technical problems, the inventors propose to introduce the glue dispensing and curing process into the shielding film pressing process. By precisely controlling the position and uniformity of the glue dispensing, the glue can fill the characteristic positions and solidify, thereby providing support and cushioning for the subsequent bonding of the shielding film, ensuring that the shielding film is not prone to breakage. Moreover, because the soft and hard junctions are filled and sealed with glue, it is ensured that water vapor cannot enter and signals cannot leak.

[0009] In one embodiment, the boundary area between the soft board and the hard board is a transition area from a rigid section to a flexible section.

[0010] In one embodiment, the high step is a step formed by the soft board and the hard board in the boundary area.

[0011] In one of the embodiments, in the glue dispensing step, the glue coverage area includes the side walls of the step, the ink window area of ​​the hard board, and the contour area of ​​the cover film opening of the soft board.

[0012] In order not to affect the grounding effect of the shielding film, the glue output needs to be accurately controlled within the above range.

[0013] In one embodiment, the copper exposed area of ​​the cover film opening of the flexible board is exposed in the glue.

[0014] In one of the embodiments, in the glue dispensing step, the amount of glue is 0.1-0.2 mg, the accuracy is within ±50 μm, and the overflow amount is ≤0.6 mm.

[0015] In one of the embodiments, the high step is ≥ 200 μm.

[0016] The present invention also provides a method for preparing a high-step hard-flex board, comprising the following steps: preparing an inner-layer soft board, laminating the inner-layer soft board, a PP sheet, and a copper-clad laminate, drilling, copper plating, circuit production, ink printing, and shielding film lamination to obtain a high-step hard-flex board; the shielding film lamination step is implemented using the shielding film lamination method.

[0017] The present invention also provides a high-step hard-soft combination board obtained by the preparation method.

[0018] The present invention also provides application of the high-step rigid-flex board in the preparation of electronic products.

[0019] The present invention also provides an electronic product, which is prepared by using the high-step hard-flex board.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention provides a shielding film lamination method and application for a high-step hard-soft combination board. The shielding film lamination method can ensure that the shielding film is not prone to breakage during the lamination process, while also ensuring the signal shielding effect of the hard-soft combination area. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the main structure of the shielding film;

[0023] Figure 2 This is a schematic diagram of the presence of cavities and bubbles in the product before vacuum rapid pressing during the preparation of a rigid-flexible board using a conventional process;

[0024] Figure 3 This is a schematic diagram of the product shielding film breaking after vacuum rapid pressing during the preparation of a rigid-flex board using a conventional process;

[0025] Figure 4 This is a schematic diagram of a product obtained by vacuum rapid pressing after glue dispensing in the embodiment;

[0026] Among them, 1 is a protective film, 2 is an adhesive film layer (3-10μm), 3 is a metal layer (0.2-3.5μm), 4 is an insulating layer (3-20μm), 5 is a carrier film, 6 is a shielding film, 7 is a hard board area, 8 is a soft board area, 9 is a cavity, 10 is a resin, 11 is a side wall of the step, 12 is an ink window area of ​​the hard board, 13 is a contour area of ​​the opening of the covering film of the soft board, and 14 is an exposed copper area of ​​the opening of the covering film of the soft board. DETAILED DESCRIPTION

[0027] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

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

[0029] source:

[0030] Unless otherwise specified, the reagents, materials, and equipment used in this example are all commercially available; the experimental methods are all conventional experimental methods in the art unless otherwise specified.

[0031] Example

[0032] A method for preparing a high-step rigid-flex board.

[0033] In this embodiment, the high step is ≥200 μm, and the method for preparing the high-step rigid-flex board comprises the following steps:

[0034] Prepare the inner soft board, press the inner soft board, PP sheet and copper clad laminate, drill holes, copper plate, make circuits, print inks and press shielding films to obtain a high-step hard-soft board.

[0035] The original process of the above-mentioned shielding film laminating process is: laser uncovering - laminating shielding film - vacuum quick pressing - curing. In this embodiment, glue dispensing and curing are introduced into the shielding film laminating process, that is, the process is: laser uncovering - glue dispensing - curing - laminating shielding film - vacuum quick pressing - curing.

[0036] In this embodiment, the high step refers to a step formed by the soft board and the hard board in the transition area from the rigid section to the flexible section.

[0037] The above-mentioned dispensing steps are implemented by a dispensing machine. The glue coverage area includes the side walls of the steps, the ink window area of ​​the hard board, and the contour area of ​​the cover film opening of the soft board, but does not include the exposed copper at the cover film opening of the flexible board.

[0038] In this embodiment, the glue is selected from resin. In the glue dispensing step, the glue amount is 0.1-0.2 mg, the accuracy is within ±50 μm, and the overflow amount is ≤0.6 mm. The cured glue can provide certain support and cushioning when the shielding film is pressed (such as Figure 4 As shown in the figure, the shielding film is not easy to break. At the same time, the glue fills the junction of the soft and hard boards, making it closed, ensuring that water vapor cannot enter and signals cannot leak, thus ensuring the signal shielding effect of the soft and hard combined area.

[0039] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0040] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A shielding film lamination method for a high-step rigid-flex board, characterized in that: The following steps are involved: The hard-flex board after ink printing is laser uncovered, the interface area between the hard and soft board is glued, cured, attached with shielding film, vacuum pressed and cured to obtain a high-step hard-flex board.

2. The shielding film lamination method according to claim 1, characterized in that: The high step is a step formed by the soft board and the hard board in the boundary area.

3. The shielding film lamination method according to claim 2, characterized in that: In the glue dispensing step, the glue coverage area includes the side walls of the step, the ink window area of ​​the hard board, and the contour area of ​​the cover film opening of the soft board.

4. The shielding film lamination method according to claim 3, characterized in that: The copper exposed area of ​​the cover film opening of the flexible board is exposed in the glue.

5. The shielding film lamination method according to claim 4, characterized in that: The high step is ≥200 μm.

6. A method for preparing a high-step rigid-flex board, characterized in that: The following steps are involved: Prepare an inner layer soft board, press the inner layer soft board, PP sheet, and copper clad laminate, drill holes, copper plate, make circuits, print ink, and press shielding films to obtain a high-step soft-hard combination board; the shielding film pressing step is implemented by the shielding film pressing method described in any one of claims 1-5.

7. The high-step rigid-flex board obtained by the preparation method according to claim 6.

8. Use of the high-step rigid-flex board according to claim 7 in the preparation of electronic products.

9. An electronic product, characterized in that: It is prepared by using the high-step hard-flex board described in claim 7.

Images