A method for manufacturing a circuit board and a multilayer laminated dual-band antenna unit

Abstract

The application discloses a preparation method of a circuit board and a multilayer laminated double-frequency-band antenna unit, and relates to the technical field of mobile communication antennas. The multilayer laminated double-frequency-band antenna unit comprises two layers of circuit boards and a metal radiator arranged between the two layers of circuit boards. The circuit boards are integrally pressed by engineering plastic plates and pre-plated tin copper foils, and the metal radiator serves as a reflecting bottom plate and a main supporting structure of the antenna unit. The two layers of circuit boards and the metal radiator are bonded by a second adhesive film, and a whole laminated structure is formed under vacuum heat pressing. The outer sides of the two layers of circuit boards are provided with protective cover layers. The application decouples the forming of the circuit board of the antenna unit and the preparation of the metal radiator. High-precision circuits on the circuit board are prepared by an independent PCB photoetching process which does not involve the metal radiator at all, and the metal radiator does not need to contact any strong acid or strong alkali solution at all, so that process problems such as metal corrosion, excessive deposition and adhesion reduction are eliminated from the root.

Description

Technical Field

[0001] This invention discloses a method for fabricating a circuit board and a multi-layered dual-band antenna unit, relating to the field of mobile communication antenna technology. Background Technology

[0002] Currently, information technology is developing towards higher speeds, lower latency, and greater connectivity, driven by 5G massive MIMO technology. Traditional metal (such as aluminum alloy and copper) vibrators suffer from problems such as heavy weight, high processing costs, and low integration, making it difficult to meet the urgent needs of 5G antennas for lightweight, low cost, mass production, and high integration.

[0003] Chinese utility model patent CN220510248U discloses a 5GCPE combined antenna, comprising: a first substrate and a second substrate formed by injection molding; antenna circuits are deposited on the surfaces of the first substrate and the second substrate by selective metallization process; the main body of the first substrate and the second substrate are both semi-hexagonal prisms, and the two are combined to form a hexagonal prism-shaped substrate body; antenna circuits are deposited on the outer and inner planes of the substrate body; the first substrate and the second substrate are snapped together by snap-fit.

[0004] Therefore, in the traditional manufacturing process of metal radiator antennas, selective metallization after insert injection molding is an unavoidable step. However, after metal radiators are exposed to strong acids, strong alkalis, and various oxidation / reduction solutions, two drawbacks occur: First, metal ions may "over-deposit" in non-target areas (such as the surface of the metal insert or the sidewall of the injection molded part), forming an unwanted conductive layer and causing short circuits. Second, the surface activity of the metal insert decreases after solution corrosion, making it impossible to form a strong bonding interface with the subsequently deposited metal layer, resulting in poor adhesion of the metal pattern layer. These problems severely restrict the product yield, performance consistency, and long-term reliability.

[0005] Therefore, how to eliminate the corrosion risk of metal radiators during wet metallization and obtain high-precision, high-adhesion antenna circuits is a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to propose a method for fabricating a circuit board and a multi-layer stacked dual-band antenna unit. By decoupling the molding of the circuit board in the antenna unit from the fabrication of the metal radiator, the high-precision circuit on the circuit board is completed through an independent fabrication process that does not involve the metal radiator at all. The metal radiator does not need to come into contact with any strong acid or alkali solution from beginning to end, thus eliminating the traditional process problems such as metal corrosion, excessive deposition and decreased adhesion from the root.

[0007] In a first aspect, the present invention discloses a method for preparing a circuit board, comprising: determining an engineering plastic board as an insulating substrate, a first adhesive film as an adhesive layer, and a pre-plated tin copper foil as a conductive layer; drilling venting micropores in the non-patterned area of ​​the engineering plastic board and performing surface activation treatment on the engineering plastic board; stacking and assembling the layers in the order of lower steel plate-release film-pre-plated tin copper foil-first adhesive film-engineering plastic board-first adhesive film-pre-plated tin copper foil-release film-upper steel plate, and controlling the board thickness and flatness by using matching equal height limiting fixtures; placing the stacked assembly structure in a vacuum press, and obtaining a copper-clad laminate blank after vacuuming, hot pressing and programmed cooling; etching a preset antenna radiation circuit and / or feed network pattern on the copper-clad laminate blank to obtain a circuit board; wherein, the curing temperature of the first adhesive film and the highest temperature of the hot pressing stage are lower than the melting point of the tin layer on the surface of the pre-plated tin copper foil.

[0008] Furthermore, the pre-plated tin copper foil uses electrolytic copper foil as the substrate, the thickness of the pre-plated tin layer on the surface is 1.5 to 3.0 μm, and the surface roughness of the tin layer is 0.5 to 0.8 μm.

[0009] Furthermore, it also includes etching away the copper foil on the exhaust micropores.

[0010] Furthermore, the copper foil peel strength of the copper clad laminate is ≥1.5N / mm, and the warpage is ≤0.3%.

[0011] Furthermore, the cooling rate of the program is 1-3℃ / min, cooling down to below 60℃.

[0012] Furthermore, the parameters for vacuuming, hot pressing, and programmed cooling are set according to the first adhesive film. The first adhesive film is a modified medium-temperature curing epoxy adhesive film. The vacuuming, hot pressing, and programmed cooling include: vacuuming to -0.05 to -0.1 MPa, heating to 75 to 90°C at 3 to 5°C / min, increasing the pressure to 1.2 MPa, holding for 30 minutes, heating to 90 to 150°C at 1 to 3°C / min, increasing the pressure to 3.5 MPa, holding for 100 minutes, and cooling to 50°C at 1.5°C / min.

[0013] Secondly, the present invention discloses a multi-layered dual-band antenna unit, comprising two circuit boards and a metal radiator sandwiched between the two circuit boards; the circuit boards are manufactured using the method described in any one of claims 1-6; the metal radiator integrates a reflective cavity, mounting and positioning holes, and reinforcing ribs, serving as the reflective base plate and main support structure of the antenna unit; the two circuit boards and the metal radiator are bonded together by a second adhesive film, forming an integral laminated structure under vacuum hot pressing; a protective covering layer is provided on the outer side of each of the two circuit boards.

[0014] Furthermore, the protective cover layer is made of an engineering plastic sheet with the same coefficient of thermal expansion and dielectric constant as the circuit layer, and is bonded to the outer surface of the circuit layer by a second adhesive film; the protective cover layer is processed with corresponding connection windows by CNC technology or precision injection molding to form a sealed protection for the antenna radiation circuit and / or feed network below.

[0015] Furthermore, the protective coating is a sprayed fluorocarbon paint.

[0016] Furthermore, the second adhesive film is a thermosetting adhesive sheet with fluidity, and the loss after curing is lower than a preset value; its thickness is 0.04~0.08mm.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention decouples the forming of the antenna unit's circuit board from the fabrication of the metal radiator. The high-precision circuit on the circuit board is fabricated through an independent PCB-like photolithography etching process that does not involve the metal radiator at all. The metal radiator does not need to come into contact with any strong acid or alkali solutions from the beginning, thus eliminating a series of process problems such as metal corrosion, excessive deposition, and decreased adhesion. At the same time, in the circuit board fabrication method, this invention directly uses engineering plastic sheets with low thermal expansion coefficients to replace the traditional fiberglass cloth impregnated prepreg. Combined with the high internal stress release effect of the vacuum pressing process used in this invention, and the effective control of the board thickness tolerance by using equal height limit strips, the copper-clad laminate blank exhibits excellent dimensional stability in the subsequent etching process. This not only makes the line width, line spacing, and positional accuracy far exceed the process level of selective metallization on three-dimensional injection molded parts, but also greatly simplifies the process flow and significantly reduces equipment investment and manufacturing costs, making it especially suitable for large-scale production. 2. This invention provides a physical channel for gas to escape during the lamination process by setting venting micropores in the non-patterned area. Combined with high vacuum, it fundamentally eliminates bubbles and delamination defects caused by gas residue, thereby improving the peel strength of copper foil. 3. This invention solves the bottleneck problem of difficult adhesion of inert plastic surfaces through pretreatment methods such as plasma / chemical etching. It utilizes the melting and flow of the second adhesive film layer under vacuum hot pressing to fully wet and fill the microscopic gaps between the surface of the metal radiator and the copper foil of the circuit board. After curing, it forms a fully bonded and strong interface, which can not only effectively conduct and buffer thermal stress, but also avoid the contact nonlinearity problem that may occur in traditional connection methods, greatly improving the reliability of the antenna unit under vibration, shock and wide temperature environment. 4. The multi-layer stacked structure adopted in this invention allows complex feed networks, matching circuits, and even some passive components to be integrated in different circuit boards, and achieves physical and electrical isolation through a protective cover layer, providing great freedom for the miniaturization, multi-frequency, and high-performance design of antennas. Attached Figure Description

[0018] Figure 1 This is a flowchart of the circuit board fabrication method provided in Embodiment 1 of the present invention; Figure 2 This is an exploded view of the multi-layered dual-band antenna unit provided in Embodiment 2 of the present invention; Explanation of reference numerals in the attached drawings: 100, metal radiator; 200, second adhesive film; 301, first circuit board; 302, second circuit board; 400, protective covering layer. Detailed Implementation

[0019] To better understand the present invention, the following description, in conjunction with the accompanying drawings of the embodiments of the present invention, will further illustrate the present invention, but this is not intended to limit the present invention; various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the design concept of the present invention should fall within the protection scope of the present invention. Example 1

[0020] refer to Figure 1 This embodiment discloses a method for manufacturing a circuit board, including: Step 1: Determine the engineering plastic board as the insulating substrate, the first adhesive film as the bonding layer, and the pre-plated tin copper foil as the conductive layer.

[0021] In this embodiment, high-performance engineering plastic extrusion plates with low dielectric constant and low loss factor, such as PEEK, PPO, and PI, are used as insulating substrates. The copper foil uses THE electrolytic copper foil as the substrate and is electroplated with a matte pure tin layer using a full plating process. The thickness of the pre-plated tin layer is 1.5 to 3.0 μm, and the surface roughness of the tin layer is 0.5 to 0.8 μm. Modified medium-temperature curing epoxy film is then selected as the bonding layer between the engineering plastic extrusion plate and the copper foil.

[0022] It should be noted that the curing temperature of the first adhesive film should be lower than the melting point of the tin layer on the surface of the pre-plated tin copper foil.

[0023] Step 2: Drill venting micropores in the non-graphic area of ​​the engineering plastic sheet and perform surface activation treatment on the engineering plastic sheet.

[0024] In this embodiment, based on the distribution of the preset antenna radiation circuit and / or feed network pattern, a 0.5mm diameter through hole is drilled in the non-pattern area of ​​the engineering plastic extrusion plate as a venting microhole. The venting microhole can assist in venting and improve the interface bonding force. The copper foil on the hole is then removed by subsequent etching to avoid the hole position affecting the electrical performance.

[0025] In one embodiment, the engineering plastic sheet is surface activated by pretreatment methods such as plasma / chemical etching, which solves the bottleneck problem of difficult adhesion of inert plastic surfaces and ensures the adhesion reliability of the composite interface.

[0026] In one embodiment, before drilling the venting micropores, the process further includes: cleaning the pre-plated tin copper foil with a slightly alkaline cleaning agent by spraying, and then drying it with hot air at 60°C.

[0027] Step 3: In a clean environment, the plates are stacked in the following order: lower steel plate - release film - pre-tinned copper foil - first adhesive film - engineering plastic plate - first adhesive film - pre-tinned copper foil - release film - upper steel plate. The thickness and flatness of the plates are controlled by matching height limit fixtures.

[0028] It should be noted that for multi-layer structures, the "first adhesive film - engineering plastic board - first adhesive film" unit can be repeated, and equal height limit strips can be placed at the four corners of the board to control the final board thickness and flatness. Among them, the height of the equal height block limit fixture is dynamically matched according to factors such as the compression amount of the first adhesive film and the actual height of the parts to ensure the thickness accuracy of the copper clad laminate.

[0029] Step 4: Place the laminated structure in a vacuum press, start the vacuum system, and evacuate the vacuum level to below -0.096 to -0.1 MPa. Use a curing process of stepped heating, stepped pressurization, and slow cooling to press the laminate to obtain the copper-clad laminate blank.

[0030] In this embodiment, the cooling rate is 1-3℃ / min, cooling down to below 60℃.

[0031] It is important to note that the maximum temperature during the pressing and hot pressing stages must be lower than the melting point of the tin layer on the surface of the pre-plated tin copper foil. Furthermore, the process parameters for vacuuming, pressing and hot pressing, and programmed cooling must be set with reference to the physical properties of the first adhesive film.

[0032] In a preferred embodiment, the first adhesive film is a modified medium-temperature curing epoxy adhesive film. Correspondingly, the process parameters for vacuuming, hot pressing, and programmed cooling are set as follows: vacuuming to -0.05 to -0.1 MPa, heating to 75 to 90°C at 3 to 5°C / min, increasing the pressure to 1.2 MPa, holding for 30 minutes, heating to 90 to 150°C at 1 to 3°C / min, increasing the pressure to 3.5 MPa, holding for 100 minutes, cooling to 50°C at 1.5°C / min, and finally removing the vacuum and taking out the laminated assembly, disassembling the mold to obtain the copper-clad laminate blank.

[0033] In this embodiment, the copper foil peel strength of the copper clad laminate blank is ≥1.5N / mm, the warpage is ≤0.3%, and the solderability of the pads meets the IPC J-STD-003 Class2 standard.

[0034] Step 5: Etch the microstrip feed network corresponding to the frequency band on the copper-clad laminate blank to obtain the circuit board.

[0035] In this embodiment, when using the etching process to create printed circuit patterns, an alkaline etching solution is used, preferably a copper chloride ammonia etching solution.

[0036] The circuit board fabrication method provided in this embodiment decouples the forming of the antenna unit's circuit board from the preparation of the metal radiator 100. The metal radiator 100 does not need to come into contact with any strong acid or alkali solutions from the beginning, thus eliminating a series of process problems such as metal corrosion, excessive deposition, and decreased adhesion. At the same time, this embodiment directly uses engineering plastic sheets with low thermal expansion coefficients to replace traditional fiberglass cloth impregnated prepreg sheets. Combined with the high internal stress release effect of the vacuum pressing process used in this invention, and the effective control of board thickness tolerance by using equal height limit strips, the copper-clad laminate blank exhibits excellent dimensional stability during subsequent etching. This not only makes the line width, line spacing, and positional accuracy far exceed the process level of selective metallization on three-dimensional injection molded parts, but also greatly simplifies the process flow, significantly reduces equipment investment and manufacturing costs, and is suitable for large-scale production. Example 2

[0037] Based on Embodiment 1, this embodiment provides a multi-layered stacked dual-band antenna element, such as... Figure 2 As shown, it includes a first circuit board 301 and a second circuit board 302, and a metal radiator 100 sandwiched between the two circuit boards; wherein, the first circuit board 301 and the second circuit board 302 are both prepared by the circuit board preparation method described in Example 1.

[0038] The metal radiator 100 integrates a reflective cavity, mounting and positioning holes, and reinforcing ribs, serving as the reflective base plate and main support structure of the antenna unit. Its fabrication process is independent of the circuit board fabrication.

[0039] The first layer circuit board 301 and the metal radiator 100, as well as the metal radiator 100 and the second layer circuit board 302, are bonded together by the second adhesive film 200, forming an integral laminated structure under vacuum hot pressing.

[0040] In one embodiment, the metal radiator 100 is integrally formed by die casting aluminum alloy or by CNC technology. After forming, the plane that is bonded to the second adhesive film 200 is subjected to micro-etching treatment.

[0041] In this embodiment, the second adhesive film 200 is selected as a thermosetting adhesive sheet with good compatibility with the substrate, moderate fluidity, and low loss after curing. The preferred thickness is 0.04~0.08mm, which can ensure sufficient filling of the interface and precise control of the interlayer spacing.

[0042] Essential, such as Figure 2 As shown, a protective covering layer 400 is provided on the outer side of the first layer circuit board 301 and the second layer circuit board 302. The protective covering layer 400 is reliably connected to the outer surface of the first layer circuit board 301 and the second layer circuit board 302 through the second adhesive film 200, so as to protect the circuit and protect the environment.

[0043] In one embodiment, the protective cover layer 400 is made of an engineering plastic sheet with the same coefficient of thermal expansion and dielectric constant as the first circuit board 301, and is used to form a sealed protection for the underlying microstrip feed network. The protective cover layer 400 is machined with corresponding connection windows by CNC technology or precision injection molding for connector and wire soldering connections.

[0044] In another embodiment, a protective covering layer 400 structure is formed by spraying fluorocarbon paint over the entire area to provide comprehensive protection.

[0045] The multi-layered stacked dual-band antenna unit provided in this embodiment utilizes a multi-layered stacked structure that allows complex feed networks, matching circuits, and even some passive components to be integrated into different circuit boards, while achieving physical and electrical isolation through a protective cover layer. This provides great freedom for the miniaturization, multi-frequency, and high-performance design of antennas, and the antenna unit with this structure exhibits high performance, high consistency, and high reliability.

[0046] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing a circuit board, characterized in that, include: The engineering plastic board as the insulating substrate, the first adhesive film as the bonding layer, and the pre-plated copper foil as the conductive layer are determined. Venting micropores are drilled in the non-graphic area of ​​the engineering plastic sheet, and the engineering plastic sheet is then subjected to surface activation treatment. The layers are stacked in the following order: lower steel plate - release film - pre-tinned copper foil - first adhesive film - engineering plastic plate - first adhesive film - pre-tinned copper foil - release film - upper steel plate, and the thickness and flatness of the plates are controlled by matching equal height limit tooling. The laminated composite structure is placed in a vacuum press, and after vacuuming, hot pressing and programmed cooling, copper-clad laminate blank is obtained. A pre-defined antenna radiation circuit and / or feed network pattern is etched onto the copper-clad laminate blank to obtain a circuit board; The curing temperature of the first adhesive film and the highest temperature of the hot pressing stage are lower than the melting point of the tin layer on the surface of the pre-plated tin copper foil.

2. The method for preparing a circuit board according to claim 1, characterized in that, The pre-plated tin copper foil uses electrolytic copper foil as the substrate, with a pre-plated tin layer thickness of 1.5–3.0 μm and a tin layer surface roughness of 0.5–0.8 μm.

3. The method for preparing a circuit board according to claim 2, characterized in that, Also includes: Etching removes the copper foil from the exhaust micropores.

4. The method for preparing a circuit board according to claim 3, characterized in that, The cooling rate of the program is 1-3℃ / min, cooling down to below 60℃.

5. The method for preparing a circuit board according to claim 3, characterized in that, The first adhesive film is a modified medium-temperature curing epoxy adhesive film. The vacuuming, hot pressing and programmed cooling include: vacuuming to -0.05 to -0.1 MPa, heating to 75 to 90°C at 3 to 5°C / min, increasing the pressure to 1.2 MPa, holding for 30 minutes, heating to 90 to 150°C at 1 to 3°C / min, increasing the pressure to 3.5 MPa, holding for 100 minutes, and cooling to 50°C at 1.5°C / min.

6. The method for preparing a circuit board according to claim 3, characterized in that, The copper foil peel strength of the copper clad laminate blank is ≥1.5N / mm, and the warpage is ≤0.3%.

7. A multi-layered stacked dual-band antenna element, characterized in that, It includes two circuit boards and a metal radiator sandwiched between the two circuit boards; the circuit boards are manufactured using the circuit board manufacturing method as described in any one of claims 1-6; The metal radiator integrates a reflective cavity, mounting and positioning holes, and reinforcing ribs, serving as the reflective base plate and main support structure of the antenna unit; the two circuit boards are bonded to the metal radiator through a second adhesive film, forming an integral laminated structure under vacuum hot pressing; both circuit boards have a protective covering layer on their outer sides.

8. The multi-layered stacked dual-band antenna element according to claim 7, characterized in that, The protective covering layer is made of an engineering plastic board with the same coefficient of thermal expansion and dielectric constant as the circuit board, and is bonded to the outer surface of the two circuit boards by a second adhesive film. The protective covering layer is machined with corresponding connection windows using CNC technology or precision injection molding to form a sealed protection for the antenna radiation circuit and / or feed network below.

9. The multi-layered stacked dual-band antenna element according to claim 7, characterized in that, The protective coating is a sprayed fluorocarbon paint.

10. The multi-layered stacked dual-band antenna element according to claim 7, characterized in that, The second adhesive film is a thermosetting adhesive sheet with fluidity, and the loss after curing is lower than the preset value; its thickness is 0.04~0.08mm.

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