A lamination method for thick copper PCB with low dielectric thickness and a PCB board

Abstract

This invention relates to the field of PCB manufacturing technology, specifically to a method for laminating a thick copper PCB with a low dielectric thickness and a PCB board. The method includes: forming a first circuit pattern on the copper surface of a first copper-clad laminate, the first circuit pattern including an outer side and an inner side; forming a second circuit pattern surface on the copper surface of a second copper-clad laminate, the second circuit pattern surface being interlocked with the outer side of the first circuit pattern on the outermost core board; fabricating a release layer on the second circuit pattern surface; placing a prepreg between the core boards; and sequentially stacking the prepreg, copper foil, aluminum sheet, and tooling board from the inside out on the outer side of the first circuit pattern, the second circuit pattern surface on the tooling board being aligned with the outer side of the first circuit pattern on the outermost core board in the interlocking direction; heating and laminating the stacked core boards; removing rivets and adhesive resin from the laminating board; and removing the tooling board and aluminum sheet. This method produces a low-thickness dielectric layer on a thick copper PCB, offering advantages such as ease of operation and cost savings on resin.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, specifically to a lamination method and PCB board for thick copper PCB with low dielectric thickness. Background Technology

[0002] With the widespread adoption of new energy vehicles, the rise of high-power energy storage devices, and fast charging for mobile terminals, printed circuit boards (PCBs) often require copper thicknesses of 3 oz or more to meet the demands of high-current transmission. During the manufacturing process of thick copper PCBs, there is a gap of 105 μm or more between the circuitry and the substrate. Due to the significant height of the thick copper, voids or air bubbles are easily generated during lamination, leading to incomplete bonding between layers. This can cause the PCB to burst due to high-temperature expansion during component soldering. Existing technologies primarily address this issue through the following two methods for laminating thick copper PCBs: (Details are as follows:)

[0003] Option 1: Stacking multiple high-adhesion prepregs

[0004] The core board is made with corresponding circuit patterns. The amount of adhesive needed for lamination is calculated based on the copper layer thickness and the copper area of ​​the core board surface. Then, the number of prepreg sheets and the total resin content are calculated based on the amount of adhesive needed before lamination. The specific process is as follows: Figure 1 As shown in the diagram. Option 1 is relatively simple, allowing adjustment of the number of prepreg sheets and resin content based on different copper layer thicknesses and resin filling areas. However, Option 1 has certain drawbacks: due to the influence of the core board's circuit pattern, the copper coverage area of ​​the same circuit layer is unevenly distributed, restricting resin flow during the lamination process and easily leading to uneven resin thickness. Furthermore, to ensure resin saturation, the design often requires 2-3 times more resin than the filling area, resulting in higher costs.

[0005] Option 2: Resin for screen printing on the circuit board surface

[0006] The core board is fabricated using standard methods to create the circuit patterns for the corresponding layers. Then, liquid resin is screen-printed onto the core board surface with the circuit patterns. After the liquid resin dries, it is sanded to make the board surface smooth. The resin layer on the core board's circuit surface is sanded, while preserving the resin between the copper conductors. Finally, the core board, prepreg, and copper foil are laminated together according to standard procedures, specifically as follows: Figure 2 As shown.

[0007] Option 2 involves a complicated process, and the liquid resin screen printing process is prone to contamination with impurities, which can cause short circuits between lines. In addition, the resin sanding process can cause significant damage to the thin core board, and mechanical sanding can easily deform the core board, leading to reduced alignment between layers and creating a risk of short circuits. Summary of the Invention

[0008] One of the objectives of this invention is to overcome the shortcomings of the prior art by providing a lamination method for low dielectric thickness on thick copper PCBs. This lamination method can produce a low-thickness dielectric layer on thick copper PCBs, and has the advantages of easy operation, saving resin costs and high flexibility.

[0009] The second objective of this invention is to provide a PCB board.

[0010] To achieve one of the above objectives, the present invention provides the following technical solution:

[0011] A lamination method for thick copper PCBs with low dielectric thickness is provided, comprising the following steps:

[0012] Core board preparation:

[0013] Select a first copper-clad laminate and form a first circuit pattern on the copper surface of the first copper-clad laminate. The first circuit pattern includes an outer side and an inner side located on both sides of the core board. The outer side of the first circuit pattern faces the outside of the PCB, and the inner side of the first circuit pattern faces the inside of the PCB.

[0014] Preparation of tool plates:

[0015] Select a second copper-clad laminate, and form a second circuit pattern surface on the copper surface of the second copper-clad laminate. The second circuit pattern surface is embedded with the outer side of the first circuit pattern of the outermost core board.

[0016] Create a release layer on the second line pattern surface;

[0017] Stacking:

[0018] Cut copper foil, aluminum sheet and prepreg to fit the core board size, and drill positioning holes on the copper foil, aluminum sheet and prepreg respectively, corresponding to the positioning holes of the core board;

[0019] Several core boards are stacked, with a prepreg placed between adjacent core boards. From the inside out, the outer side of the first circuit pattern of the outermost core board is stacked with a prepreg, copper foil, aluminum sheet and tool board, so that the second circuit pattern surface on the tool board is aligned with the outer side of the first circuit pattern on the outermost core board in the fitting direction. At the same time, the positioning holes of each board are aligned. Then, rivets are driven into the aligned positioning holes to fix each board in alignment.

[0020] Pressing:

[0021] The core board after heating and stacking is pressed together to melt the prepreg and fill the gap on the outer side of the first circuit pattern to obtain a laminate.

[0022] Gong removal:

[0023] Use a cutting machine to remove the rivets and adhesive resin from the lamination board, remove the tool board and aluminum sheet, and obtain the PCB lamination board.

[0024] In some embodiments, the method for preparing the first circuit pattern and the second circuit pattern surface includes:

[0025] Image transfer is performed on the first copper-clad laminate and the second copper-clad laminate respectively. Then, etching and film removal are performed on the first copper-clad laminate and the second copper-clad laminate respectively to obtain the first circuit pattern and the second circuit pattern surface.

[0026] In some embodiments, when the outer side of the first circuit pattern is fitted with the surface of the second circuit pattern, the gap between the outer side of the first circuit board pattern and the surface of the second circuit board pattern is 0.01 to 0.08 mm.

[0027] In some embodiments, the step of creating a release layer on the second circuit pattern surface includes:

[0028] A release agent is applied to the surface of the second circuit pattern, followed by drying, so that a release layer is formed on the surface of the second circuit pattern.

[0029] In some embodiments, the prepreg is an adhesive sheet with a resin content greater than 90%, and the adhesive sheet further comprises type 2116 or type 1080 glass fiber.

[0030] In some embodiments, the step of heating and pressing the core board after stacking includes: heating the core board after stacking at 70°C to 90°C in a vacuum environment to melt the prepreg to fill the gaps in the first circuit pattern, and then heating it at 120°C to solidify the melted prepreg to obtain a dielectric layer located between the copper foil and the first circuit pattern.

[0031] In some embodiments, the thickness of the copper foil is 12–35 μm.

[0032] In some embodiments, the thickness of the aluminum sheet is 0.12 to 0.15 mm.

[0033] In some embodiments, the thickness of the dielectric layer is 0.05 to 0.2 mm.

[0034] The beneficial effects of the lamination method for thick copper PCBs with low dielectric thickness of the present invention are as follows:

[0035] The present invention discloses a lamination method for thick copper PCBs with low dielectric thickness. A tool board is employed, with a second circuit pattern surface on its surface that interlocks with the outer surface of the first circuit pattern on the outermost core board. During lamination, a prepreg, copper foil, and aluminum sheet are sequentially placed on the outermost core board, and finally the tool board is placed on top. Because the second circuit pattern surface on the tool board interlocks with the outer surface of the first circuit pattern on the outermost core board, under the pressure of the tool board, the second circuit pattern surface fully and precisely presses and fills the prepreg onto the non-copper surface of the first circuit pattern. This ensures that even with thick copper PCBs, the prepreg resin flows uniformly to the outer surface of the first circuit pattern, effectively guaranteeing the uniformity of the interlayer dielectric thickness and ensuring dielectric layer uniformity even with low dielectric thickness. An aluminum sheet is also added, which serves for heat dissipation and plasticity.

[0036] To achieve the second objective mentioned above, the present invention provides the following technical solution:

[0037] A PCB board is provided, which is manufactured by the above-described thick copper PCB low dielectric thickness lamination method. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the lamination method for thick copper PCB with low dielectric thickness in the prior art solution 1.

[0039] Figure 2 This is a schematic diagram of the lamination method for thick copper PCB with low dielectric thickness in the prior art solution 2.

[0040] Figure 3 This is a schematic diagram of a lamination method for thick copper PCBs with low dielectric thickness according to a specific embodiment of the present invention.

[0041] Figure 4 This is a schematic diagram of the interlocking gap between the tool plate and the core plate in a specific embodiment of the present invention.

[0042] Figure 5 This is a schematic diagram of the outer side of the first circuit pattern of the core board and the second circuit pattern surface of the tool board before they are interlocked in a specific embodiment of the present invention.

[0043] Figure 6 This is a schematic diagram of the preparation of the outer surface of the first circuit pattern or the surface of the second circuit pattern according to a specific embodiment of the present invention. Detailed Implementation

[0044] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0045] Example 1

[0046] Please see Figure 3 , 5 This embodiment discloses a lamination method for thick copper PCBs with low dielectric thickness, including the following steps:

[0047] Core board preparation:

[0048] Select a first copper-clad laminate and form a first circuit pattern on the copper surface of the first copper-clad laminate. The first circuit pattern includes an outer side and an inner side located on both sides of the core board. The outer side of the first circuit pattern faces the outside of the PCB, and the inner side of the first circuit pattern faces the inside of the PCB.

[0049] Specifically, please refer to Figure 6 According to product requirements, a first copper-clad laminate with the appropriate copper thickness is selected. A first circuit pattern is formed on the first copper-clad laminate through an image transfer → flash etching → film removal process. Copper surfaces that are not in the first circuit pattern position are removed to expose the corresponding substrate surface. Therefore, the copper surfaces in the positions where circuit patterns do not need to be formed are etched to expose the substrate.

[0050] Preparation of tool plates:

[0051] Select a second copper-clad laminate, and form a second circuit pattern surface on the copper surface of the second copper-clad laminate. The second circuit pattern surface is embedded with the outer side of the first circuit pattern of the outermost core board.

[0052] The steps for creating the second circuit pattern surface on the tool board are the same as those for preparing the circuit pattern, which is also through image transfer → flash etching → film removal process. However, the position of the second circuit pattern surface is exactly opposite to that of the first circuit pattern, so that the second circuit pattern surface of the tool board and the first circuit pattern of the core board are distributed in an interlocking manner.

[0053] Since the tool board only needs to press the core board with the second circuit pattern face on one side, in order to save production costs, improve production efficiency, and ensure the uniformity of the pressing force, the second circuit pattern face is only manufactured on one side of the tool board.

[0054] Furthermore, since the PCB has outermost core boards on both sides, two tool boards need to be made to correspond to the outer side of the first circuit pattern of the outermost core boards on both sides.

[0055] Furthermore, a release layer is made on the second circuit pattern surface. The main function of making a release layer on the second circuit board is to prevent the tool board from sticking to the board layer during the lamination process, which would affect the efficiency of subsequent board disassembly.

[0056] Stacking:

[0057] Cut copper foil, aluminum sheet and prepreg to fit the core board size, and drill positioning holes on the copper foil, aluminum sheet and prepreg respectively, corresponding to the positioning holes of the core board;

[0058] Several core boards are stacked, with a prepreg placed between adjacent core boards. From the inside out, the outer side of the first circuit pattern of the outermost core board is stacked with a prepreg, copper foil, aluminum sheet and tool board, so that the second circuit pattern surface on the tool board is aligned with the outer side of the first circuit pattern on the outermost core board in the fitting direction. At the same time, the positioning holes of each board are aligned. Then, rivets are driven into the aligned positioning holes to fix each board in alignment.

[0059] Specifically, copper foil, aluminum sheet, and prepreg are cut to the appropriate sizes. Then, positioning holes are drilled in the copper foil, aluminum sheet, and prepreg at the same positions as the core board. Generally, the positioning holes are distributed along the edges of the board layers to avoid affecting the function of the board. Subsequently, since there are usually multiple core boards, prepreg is first stacked on adjacent core boards. Then, copper foil is stacked on the outer side of the first circuit diagram of the outermost core board. Next, aluminum sheet is stacked on the copper foil. Finally, tool board is stacked on the aluminum sheet to align the positioning holes at each position. Rivets are driven into the positioning holes to prevent the board from shifting during the pressing process.

[0060] Furthermore, when there is only one core board, tool boards are respectively set on the outer side of the first circuit diagram and the inner side of the second circuit diagram on the core board.

[0061] Pressing:

[0062] The core board after heating and stacking is pressed together to melt the prepreg to fill the gaps on the outer side of the first circuit pattern, thus obtaining a laminate.

[0063] Under heating conditions, the prepreg melts and flows well onto the first circuit pattern. Then, under the corresponding pressure of the second circuit pattern surface of the tool plate, the melted prepreg can be evenly distributed on the second circuit pattern surface to form a uniform dielectric layer. Furthermore, through the pressing action, the layers are bonded together.

[0064] Gong removal:

[0065] The rivets and adhesive resin on the lamination board are removed using a cutting machine. The tool board and aluminum sheet are removed to obtain the PCB lamination board. After the PCB lamination board is obtained, the laminated substrate is drilled and the circuit is installed normally.

[0066] In this embodiment, please refer to Figure 4 When the outer side of the first circuit pattern is embedded with the surface of the second circuit pattern, the gap between the embedded positions of the first circuit board pattern and the second circuit board pattern is 0.01 to 0.08 mm, preferably 0.05 mm. This size can be adjusted according to actual needs and is not a unique limitation here.

[0067] The size of this gap can be adjusted according to actual needs, and there is no single limitation here. The purpose of this gap is to facilitate the resin to flow well to the non-copper surface of the second circuit pattern.

[0068] In this embodiment, the step of creating a release layer on the second circuit pattern surface includes:

[0069] A release agent is applied to the surface of the second circuit pattern, followed by drying, so that a release layer is formed on the surface of the second circuit pattern.

[0070] In this embodiment, the semi-cured sheet is an adhesive sheet with a resin content greater than 90%, and the adhesive sheet also contains type 2116 or type 1080 glass fiber.

[0071] In this embodiment, the step of heating and pressing the core board after stacking includes: heating the core board after stacking at 70°C to 90°C, preferably 80°C, in a vacuum environment to melt the prepreg to fill the gaps in the first circuit pattern, and then heating at 120°C to 150°C, preferably 140°C, to solidify the melted prepreg to obtain a dielectric layer located between the copper foil and the first circuit pattern.

[0072] Under the high temperature and high pressure of the prepreg in the vacuum environment of the press, the resin in the prepreg begins to melt and gradually fills the gaps in the first circuit pattern. The prepreg is a bonding sheet with a resin content of over 90%, containing 2116 or 1080 type glass fibers. The thin glass fibers help to accommodate the height difference of the copper surface on the curved core board during the pressing process. The resin melts and becomes fluid when heated to 80℃, and begins to cure upon further heating to 140℃. After curing, the core board and copper foil are bonded together.

[0073] In this embodiment, the thickness of the copper foil is 12–35 μm. The copper foil is a commonly used copper foil in the production of PCB multilayer boards, and the thickness of the copper foil can be selected according to the conductivity of the PCB product, often ranging from 12 μm, 18 μm, to 35 μm.

[0074] In this embodiment, the thickness of the aluminum sheet is 0.12 to 0.15 mm, and the aluminum sheet is a commonly used aluminum sheet in circuit board production.

[0075] In this embodiment, the thickness of the dielectric layer is 0.05–0.2 mm. Because the above-described lamination method is used, the required dielectric thickness of 0.05–0.2 mm for thick copper HDI products can be achieved.

[0076] The above lamination method allows the tool board to be obtained by etching the surface copper of a standard copper-clad laminate. Furthermore, the copper thickness specifications of the tool board can be selected according to different copper thicknesses, offering strong practicality and flexibility. It enables resin filling during the lamination of stepped copper thickness buried via boards, reducing circuit board manufacturing processes and lowering costs. It provides a new solution for the 0.05–0.2 mm dielectric thickness required for thick copper HDI products.

[0077] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0078] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0079] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0080] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this application.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lamination method for thick copper PCBs with low dielectric thickness, characterized in that, Includes the following steps: Core board preparation: Select a first copper-clad laminate and form a first circuit pattern on the copper surface of the first copper-clad laminate. The first circuit pattern includes an outer side and an inner side located on both sides of the core board. The outer side of the first circuit pattern faces the outside of the PCB, and the inner side of the first circuit pattern faces the inside of the PCB. Preparation of tool plates: Select a second copper-clad laminate, and form a second circuit pattern surface on the copper surface of the second copper-clad laminate. The second circuit pattern surface is embedded with the outer side of the first circuit pattern of the outermost core board. Create a release layer on the second line pattern surface; Stacking: Cut copper foil, aluminum sheet and prepreg to fit the core board size, and drill positioning holes on the copper foil, aluminum sheet and prepreg respectively, corresponding to the positioning holes of the core board; Several core boards are stacked, with a prepreg placed between adjacent core boards. From the inside out, the outer side of the first circuit pattern of the outermost core board is stacked with a prepreg, copper foil, aluminum sheet and tool board, so that the second circuit pattern surface on the tool board is aligned with the outer side of the first circuit pattern on the outermost core board in the fitting direction. At the same time, the positioning holes of each board are aligned. Then, rivets are driven into the aligned positioning holes to fix each board in alignment. Pressing: The core board after heating and stacking is pressed together to melt the prepreg and fill the gap on the outer side of the first circuit pattern to obtain a laminate. Gong removal: Use a cutting machine to remove the rivets and adhesive resin from the lamination board, remove the tool board and aluminum sheet, and obtain the PCB lamination board.

2. The lamination method for thick copper PCBs with low dielectric thickness according to claim 1, characterized in that, The method for preparing the first circuit pattern and the second circuit pattern includes: Image transfer is performed on the first copper-clad laminate and the second copper-clad laminate respectively. Then, etching and film removal are performed on the first copper-clad laminate and the second copper-clad laminate respectively to obtain the first circuit pattern and the second circuit pattern surface.

3. The lamination method for thick copper PCBs with low dielectric thickness according to claim 1, characterized in that, When the outer side of the first circuit pattern is fitted into the surface of the second circuit pattern, the gap between the outer side of the first circuit board pattern and the surface of the second circuit board pattern is 0.01 to 0.08 mm.

4. The lamination method for thick copper PCBs with low dielectric thickness according to claim 1, characterized in that, The step of creating a release layer on the second line pattern surface includes: A release agent is applied to the surface of the second circuit pattern, followed by drying, so that a release layer is formed on the surface of the second circuit pattern.

5. The lamination method for thick copper PCBs with low dielectric thickness according to claim 1, characterized in that, The prepreg is an adhesive sheet with a resin content greater than 90%, and the adhesive sheet also contains type 2116 or type 1080 glass fiber.

6. The lamination method for thick copper PCBs with low dielectric thickness according to claim 1, characterized in that, The step of heating and pressing the core board after stacking includes: heating the core board after stacking at 70°C to 90°C in a vacuum environment to melt the prepreg to fill the gaps in the first circuit pattern, and then heating it at 120°C to solidify the melted prepreg to obtain a dielectric layer located between the copper foil and the first circuit pattern.

7. The lamination method for thick copper PCBs with low dielectric thickness according to claim 1, characterized in that, The thickness of the copper foil is 12–35 μm.

8. The lamination method for thick copper PCBs with low dielectric thickness according to claim 1, characterized in that, The thickness of the aluminum sheet is 0.12 to 0.15 mm.

9. The lamination method for thick copper PCBs with low dielectric thickness according to claim 6, characterized in that, The thickness of the dielectric layer is 0.05–0.2 mm.

10. A PCB board, characterized in that, It is prepared by the lamination method of thick copper PCB with low dielectric thickness as described in any one of claims 1 to 9.

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