Reinforcing method of FPC (Flexible Printed Circuit) and application of reinforcing method

Abstract

The invention relates to an FPC reinforcing method and application thereof, and relates to the technical field of FPCs. The reinforcing method comprises the following steps of: setting a windowing area in a waste area of the FPC pasted with a protective film, removing a copper layer and the protective film in the windowing area, laminating the protective film and the FPC, printing solder paste, pasting a reinforcing piece, and passing through a furnace. According to the reinforcement method, a local windowing mode is ingeniously utilized, the reinforcement offset is controlled, and the problem that reinforcement offset is prone to exceeding tolerance when a small-size reinforcement piece is adopted in the past is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of FPC, and particularly to a reinforcement method for FPC and its application. Background Art

[0002] Since flexible printed circuit (abbreviated as FPC) has the characteristics of high wiring density, light weight, thin thickness, and good bendability, it has been widely used in the fields of electronics, automotive, medical, aerospace, etc. In the actual application process, reinforcement design is often required. The usual reinforcement design is carried out according to the outer dimension of the FPC. However, due to the problem of space utilization rate, there are often products with reinforcement exceeding the outer shape of the FPC.

[0003] For the reinforcement of steel sheets with such an over-sized shape, there are usually two lamination methods: (1) Using a machine lamination method. However, for this kind of lamination method, there are requirements for the size of the reinforced steel sheet, and the outer width is at least ≥ 0.8 mm. (2) For the steel sheet used for reinforcement with an outer width less than 0.8 mm, a method similar to component pasting is adopted, that is, solder paste is printed and then the steel sheet is laminated.

[0004] For the lamination method in (2), when the lamination position of the steel sheet used for reinforcement exceeds the outer dimension of the FPC, there are often large reinforcement offset problems in the lamination of the steel sheet, and the accuracy does not meet the customer requirements. Summary of the Invention

[0005] In view of the above problems, the present invention provides a reinforcement method for FPC. By cleverly using the method of local window opening, the reinforcement offset amount is controlled, and the problem of reinforcement offset exceeding the tolerance that is likely to occur when using small-sized reinforcement parts in the past is solved.

[0006] To achieve the above object, the present invention provides a reinforcement method for FPC, including the following steps: setting a window opening area in the waste area of the FPC after pasting the protective film, removing the copper layer and the protective film in the window opening area, laminating the protective film with the FPC, printing solder paste, laminating the reinforcement part, and passing through the furnace.

[0007] In the present invention, the waste area refers to the area other than the part pattern. The steps of removing the copper layer and the protective film in the window opening area can be realized by laser cutting.

[0008] In one embodiment, the reinforcement part is divided into an FPC outer shape area and an over-sized area, and the over-sized area is the area where the reinforcement part exceeds the outer shape of the FPC.

[0009] In one embodiment, the contour of the window opening area matches the contour of the over-sized area.

[0010] In the process of researching the above-mentioned problem of reinforcement offset, the inventor found that the reason for the occurrence of reinforcement offset is that after printing solder paste on the board surface, the solder paste will flow on the copper surface during reflow soldering, and the flowing solder paste will synchronously drive the attached reinforcement to shift. Moreover, since the shape of the reinforcement exceeds the board edge, there are no other components to block the displacement of the reinforcement. Therefore, the inventor proposed the above technical solution. First, the area where the reinforcement exceeds the FPC shape and the overlapping part with the scrap area are windowed, and the copper layer and protective film in the windowed area are removed to create a step height difference and form a groove. Then, the reinforcement is attached. The step height difference around the groove can fix the position of the part of the reinforcement that exceeds the FPC shape, so as to ensure that when the solder paste flows, it will not affect the original position of the steel sheet, and further control the reinforcement offset amount through the height difference formed by windowing, thus solving the problem of reinforcement offset exceeding the tolerance for the type of reinforcement that exceeds the shape. At the same time as removing the protective film layer, the copper layer is also removed, which can ensure high-precision graphic windowing, provide a better reference for the protective film layer, form a higher step here, and have a higher benefit in preventing reinforcement offset.

[0011] In one embodiment, the single side of the windowed area is 0.15 mm - 0.2 mm larger than the single side of the exceeded area.

[0012] In one embodiment, the width of the reinforcement ≤ 0.8 mm.

[0013] The present invention also provides a method for preparing an FPC, including the following steps: blanking, drilling, electroplating, circuit manufacturing, attaching a protective film, and performing reinforcement using the above-mentioned reinforcement method.

[0014] The present invention also provides the application of the above-mentioned reinforcement method in the preparation of an FPC.

[0015] The present invention also provides the FPC obtained by the above-mentioned preparation method.

[0016] In one embodiment, the occurrence probability of reinforcement offset of the FPC ≤ 0.2%.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] A reinforcement method for FPC and its application. In this reinforcement method, the overlapping part of the area where the reinforcement piece extends beyond the FPC outline and the waste area is pre-opened, the copper layer and the protective film in the opened area are removed to create a step height difference and form a groove, and then the reinforcement piece is adhered. The step height difference around the groove can fix the position of the part of the reinforcement piece that extends beyond the FPC outline, so as to ensure that when the solder paste flows, it will not affect the original position of the steel sheet. Furthermore, by controlling the height difference formed by the opening, the reinforcement offset amount is controlled, and the problem of reinforcement deviation beyond the tolerance for the type exceeding the outline is solved. Using this reinforcement method, the occurrence probability of reinforcement deviation of FPC is reduced from the original 20% to 0.2%, the defective rate is significantly decreased, and the improvement effect is remarkable. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FIG. is a schematic structural diagram of the changes before and after adhering the reinforcement piece by the conventional reinforcement method and the reinforcement method of the present invention in the embodiment. Among them, Figure 1 The left side of the dashed line in is the conventional reinforcement method, Figure 1 The right side of the dashed line in is the reinforcement method of the present invention; Figure 1 ① in is the protective film of the FPC, ② is the copper layer of the FPC, ③ is the steel sheet for reinforcement, and ④ is the PI in the waste area;

[0020] Figure 2 FIG. is a schematic diagram of the product after the implementation of the conventional reinforcement method;

[0021] Figure 3 FIG. is the electron microscope image of the product after the implementation of the conventional reinforcement method;

[0022] Figure 4 FIG. is the electron microscope image of the product after the implementation of the reinforcement method of the present invention;

[0023] Figure 5 FIG. is a cross-sectional view of the changes before and after adhering the reinforcement piece by the conventional reinforcement method and the reinforcement method of the present invention in the embodiment. Among them, Figure 5 The left side is the conventional reinforcement method, Figure 5 The right side is the reinforcement method of the present invention; Figure 5 ① in is the protective film layer in the waste area, ② is the copper layer in the waste area, ③ is the dielectric layer in the waste area, ④ is the steel sheet for reinforcement, ⑤ is the solder paste before passing through the furnace, ⑥ is the state of the solder paste after passing through the furnace, ⑦ is the outline area of the FPC (excluding the steel sheet), ⑧ is the outline area of the FPC including the steel sheet, and the steel sheet for reinforcement extends beyond the outline area of the FPC, ⑨ is the protective film under the adhered steel sheet, and ⑩ is the copper layer under the adhered steel sheet. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant accompanying drawings. Preferred embodiments of the present invention are shown 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, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0026] Source:

[0027] Unless otherwise specified, the reagents, materials, and equipment used in this embodiment are all commercially available; unless otherwise specified, the experimental methods are all conventional experimental methods in this field.

[0028] Embodiment

[0029] I. A method for reinforcing an FPC.

[0030] The reinforcing member is divided into an FPC outer shape area and an excess area. The excess area overlaps with the waste area. A window area is set in the waste area. The contour of the window area matches the contour of the excess area, and the unilateral side of the window area is 0.15 - 0.2 mm larger than the unilateral side of the excess area.

[0031] The copper layer and the protective film in the window area are removed by grooving. The grooving can be specifically achieved by laser cutting. The protective film is laminated with the FPC main board, solder paste is printed, the reinforcing member is SMT - attached, and then passed through the furnace.

[0032] II. Technical effects after using the conventional reinforcing method and the reinforcing method of the present invention.

[0033] 1. Figure 1 It is a top view before and after passing through the furnace when laminating a steel sheet for reinforcement under the conventional reinforcing method and the reinforcing method of the present invention.

[0034] Among them, ① is the protective film of the FPC, ② is the copper layer of the FPC, ③ is the steel sheet for reinforcement, and ④ is the PI in the waste area.

[0035] In this embodiment, the steel sheet for reinforcement exceeds the outer dimension of the FPC, and the width of the steel sheet for reinforcement ≤ 0.8 mm. Under the operation of the conventional reinforcing method, after passing through the furnace, the steel sheet undergoes left - right displacement. The structural schematic diagram is as shown in the left figure of Figure 1 The product schematic diagram and the electron microscope image after implementing the conventional reinforcing method are respectively as shown in Figure 2 、 3 shown.

[0036] Under the operation of the reinforcement method of the present invention, after passing through the furnace, the steel sheet will not shift left and right. The structural schematic diagram is as shown in the right figure of Figure 1 . The electron microscope image of the product after implementing the reinforcement method of the present invention is as shown in Figure 4 .

[0037] Among them, compared with the exceeding area, the unilateral size of the windowed area is 0.15 - 0.2 mm larger: X1: 0.15 - 0.2 mm, X2: 0.15 - 0.2 mm, Y1: 0.15 mm - 0.2 mm, Y2: 0.15 - 0.2 mm.

[0038] 2. Figure 5 are the cross-sectional views before and after passing through the furnace when bonding the steel sheet for reinforcement under the conventional reinforcement method and the reinforcement method of the present invention.

[0039] Among them, ① is the protective film layer in the waste area, ② is the copper layer in the waste area, ③ is the dielectric layer in the waste area, ④ is the steel sheet for reinforcement, ⑤ is the solder paste before passing through the furnace, ⑥ is the state of the solder paste after passing through the furnace, ⑦ is the outer shape area of the FPC (excluding the steel sheet), ⑧ is the outer shape area of the FPC including the steel sheet, and the steel sheet for reinforcement exceeds the outer shape area of the FPC, ⑨ is the protective film under the bonding of the steel sheet, and ⑩ is the copper layer under the bonding of the steel sheet.

[0040] As can be seen from Figure 5 , the protective film and copper layer under the bonding of the steel sheet are removed in advance. When bonding, the steel sheet is inclined and can just be restricted in position by the groove in the windowed area. After passing through the furnace, the solder paste melts and collapses, causing one end of the steel sheet to move up and down rather than left and right, ensuring the bonding position of the steel sheet.

[0041] The technical features of the above-mentioned embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification.

[0042] The above-mentioned embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it cannot be understood as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A reinforcing method for an FPC, characterized in that, Including the following steps: Set a windowing area in the waste area of the FPC after applying the protective film, remove the copper layer and the protective film in the windowing area, press the protective film and the FPC together, print solder paste, bond a reinforcing member, and pass through the furnace.

2. The reinforcing method according to claim 1, characterized in that The reinforcing member is divided into an FPC outer shape area and an overhanging area, and the overhanging area is the area where the reinforcing member extends beyond the FPC outer shape.

3. The reinforcing method according to claim 2, wherein, The contour of the windowing area matches the contour of the overhanging area.

4. The reinforcement method according to claim 2, characterized in that, One side of the windowing area is 0.15 mm - 0.2 mm larger than one side of the overhanging area.

5. The reinforcing method according to any one of claims 1-4, characterized in that, The width of the reinforcing member ≤ 0.8 mm.

6. A method for preparing an FPC, characterized in that, Including the following steps: Cutting the material, drilling, electroplating, circuit manufacturing, applying the protective film, and reinforcing using the reinforcing method described in any one of claims 1 - 5.

7. Use of the reinforcing method described in any one of claims 1 - 5 in the preparation of FPC.

8. FPC obtained by the preparation method described in claim 6.

9. The FPC according to claim 8, wherein The occurrence probability of the reinforcing offset of the FPC ≤ 0.2%.

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