Ultra-thick copper product processing technology

Abstract

The invention discloses an ultra-thick copper product processing technology, which comprises the following steps of: before a multilayer board lamination process, carrying out graphical pre-etching treatment on an outer-layer thick copper plate, and accurately reducing the copper thickness of a specific area to a preset residual thickness (100-120 microns). After the treatment, the height difference between the circuit and the base material is obviously reduced after the subsequent etching of the outer circuit is completed, so that the IPC standard requirement can be met only through one-time printing in the anti-welding process. Meanwhile, the defects of alignment accumulation deviation, interlayer bubbles, curing internal stress and the like caused by multiple times of printing are avoided through one-time solder mask forming, the uniformity, compactness and adhesive force of the solder mask layer are fundamentally improved, and therefore the yield and long-term reliability of products are greatly improved. The technology is completely compatible with an existing PCB production line, expensive new equipment does not need to be invested, rapid introduction can be achieved with extremely low transformation cost, and the technology has extremely high market popularization value.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing technology, and in particular to a processing technology for ultra-thick copper products. Background Technology

[0002] With the development of power electronics, automotive electronics, and high-power power modules, the demand for printed circuit boards (PCBs) capable of carrying high currents is increasing. These applications require PCBs with ultra-thick copper foil in the circuit layers. However, in existing ultra-thick copper PCB manufacturing processes, after the outer circuit is etched, a huge height difference, up to 400μm, is formed between the copper conductor of the circuit and the substrate.

[0003] However, in existing ultra-thick copper PCB manufacturing processes, after the outer layer circuit pattern is etched, a significant height difference is created between the thick copper conductors and the copper-free substrate area, sometimes reaching the original thickness of the copper foil. This substantial height difference poses a significant challenge to the subsequent solder resist process. To ensure that the solder resist ink can reliably cover the towering circuit tops and completely fill the recessed substrate areas simultaneously, meeting IPC standards for ink thickness, adhesion, and insulation, production must rely on multiple solder resist ink printing and curing cycles. This multi-stage production model directly leads to a severe decrease in production efficiency, a significant increase in production costs (including ink, energy consumption, and labor costs), and an extended product delivery cycle. Furthermore, multiple printing cycles easily introduce a series of quality and reliability issues, such as misalignment, interlayer bubbles, and insufficient or excessive ink curing. A new ultra-thick copper PCB processing technology is urgently needed to solve the solder resist production problems caused by the excessive height difference.

[0004] Therefore, the processing technology for ultra-thick copper products proposed in this invention has significant practical implications. Summary of the Invention

[0005] The purpose of this invention is to provide a processing technology for ultra-thick copper products to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A processing technology for ultra-thick copper products, characterized by including the following steps:

[0008] S1. Preparation of inner core board: The core board is cleaned and its copper surface is roughened. Then, a liquid photosensitive wet film is covered on both sides of the core board and baked. The copper plate with film is exposed using an exposure machine and film pattern to complete the pattern transfer. Then, development is performed, and the exposed copper layer is removed by etching process. Film stripping is performed. Finally, the inner core board is obtained by scanning and inspection using automatic optical inspection equipment.

[0009] S2. Lamination: The inner core board and pre-etched copper plate are browned and then laminated with the prepreg to obtain a laminated structure. The laminated structure is pre-fixed using a riveting process. A steel plate is placed between each layer of the laminated structure and then fed into a hydraulic press for lamination. The heating rate during the lamination process is 1.76℃ / min and the high pressure point is 105-115℃ to obtain a multilayer board. The multilayer board is then subjected to X-ray target inspection and edge trimming to obtain the laminated board.

[0010] S3. Post-processing: Drilling holes in the laminated plate, electroplating with copper, then transferring and etching the outer layer pattern, followed by one-time solder resist printing, exposure, development and curing, and finally surface tin spraying, testing and shaping to obtain ultra-thick copper products.

[0011] As a preferred embodiment of the present invention, the pre-etched copper plate is prepared by the following steps:

[0012] Step 1, Pretreatment and lamination: Use a sandblasting line at a speed of 2.5-3.5 meters / minute to remove the surface oxide layer of the 400um thick copper plate. After cleaning, use a laminating machine to apply the dry film to the surface of the copper plate to obtain a laminated copper plate.

[0013] Step 2, Exposure and Development: Expose the copper plate with film using an exposure machine and film pattern to complete the pattern transfer. Then, develop the copper plate by using a sodium carbonate solution to remove the unexposed dry film on the surface of the copper plate, resulting in a developed copper plate.

[0014] Step 3, Etching and Film Removal: Place the developed copper plate in an etching machine containing hydrochloric acid oxidant solution and etch the developed copper plate at a speed of 1-2 meters / minute, controlling the residual etching thickness of the etched area to be 100-120um. Then, use sodium hydroxide solution to remove the residual dry film on the surface of the copper plate, and then wash and dry it to obtain a copper plate with controlled depth etching.

[0015] Step 4, Inspection and Decommissioning: Use automated optical inspection equipment to inspect the remaining thickness and pattern of the controlled-depth etched copper plate to obtain the pre-etched copper plate.

[0016] As a preferred embodiment of the present invention, the prepreg is composed of two 106-type epoxy resin prepregs with a resin content of 72% and one glass fiber cloth prepreg with a resin content of 92%.

[0017] As a preferred embodiment of the present invention, the film pressing temperature of the film pressing machine in step one is 110-130℃ and the speed is 2.2-3.2 meters / minute.

[0018] As a preferred embodiment of the present invention, the developing speed in step two is 3.5-4.5 meters per minute.

[0019] As a preferred embodiment of the present invention, the temperature of the hydrochloric acid oxidant solution in step three is 50-60°C.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. This invention, by introducing a copper pre-etching process, significantly reduces the height difference between the circuitry and the substrate, allowing the solder mask process to meet IPC standards with only one pass, completely eliminating the need for 3 to 4 solder mask passes required in existing processes. This significantly improves production efficiency and substantially saves on ink, energy, and labor costs, while significantly shortening product delivery time. Furthermore, this process relies entirely on existing PCB production line equipment (such as pre-processing, pattern transfer, and etching lines), eliminating the need for expensive new specialized equipment. This allows companies to quickly adopt this advanced process at extremely low modification costs, rapidly transforming technological advantages into market competitiveness.

[0022] 2. This invention, through a one-time solder resist printing technology, eliminates defects such as cumulative misalignment, interlayer bubbles, and internal stress caused by multiple printing processes. This fundamentally improves the uniformity, density, and adhesion of the solder resist layer, significantly enhancing product yield and long-term reliability. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the cross-section of the copper plate after pre-etching according to the present invention.

[0024] Figure 2 This is a schematic cross-sectional view of the core board after etching according to the present invention.

[0025] Figure 3 This is a schematic cross-sectional view of the laminated layers of the present invention.

[0026] Figure 4 This is a schematic cross-sectional view of the outer layer circuit after etching.

[0027] Figure 5 This is a schematic diagram of the cross-section of the final product after the anti-welding treatment of the present invention.

[0028] Figure 6 This is a schematic diagram comparing the structure of the ultra-thick copper product of the present invention with that before the improvement. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0031] The copper pre-etching process introduced in this invention fundamentally solves the bottleneck problem of existing ultra-thick copper PCB production processes: (1) It fundamentally achieves a significant improvement in production efficiency, while significantly saving ink consumables and energy consumption, and greatly compressing the production cycle. This process significantly reduces the stage height difference between the circuit and the substrate from the original thickness of the copper foil (400μm) to the target residual thickness after pre-etching (110μm). In the subsequent outer layer circuit etching process, it is only necessary to etch through this residual thickness layer to expose the substrate surface. This height difference is completely within the process window of conventional liquid photosensitive solder resist ink single printing. Accordingly, the solder resist process can be reduced from the original three to four repeated operations to one solder resist operation, which can meet the IPC standard. (2) It significantly enhances the consistency of product quality and long-term reliability. The single-pass solder resist printing process completely eliminates the risks of cumulative misalignment tolerances, interlayer bubble residues, and material thermal stress accumulation and ink aging and embrittlement caused by multiple printing processes. Furthermore, the solder resist layer achieves fundamental improvements in thickness uniformity, material density, and adhesion to the substrate and circuit surface. (3) Expanding the process window and improving process stability and circuit accuracy. After pre-etching, the outer layer pattern etching no longer faces a uniform, extremely thick copper layer, but rather a composite interface composed of a thin residual thickness area and the original thick copper circuit area. This structure allows for more precise control of over-etching during the etching process, effectively suppressing side etching and defects such as pad size distortion caused by it. The etching uniformity and dimensional accuracy of the outer layer circuit are guaranteed, providing a reliable process basis for achieving higher density circuit design on ultra-thick copper products. (4) The copper plate pre-etching process is based entirely on the existing pattern transfer and etching equipment system commonly used in PCB production lines. There is no need to add major new special equipment, which can reduce investment costs and quickly complete the technology introduction and mass production transformation of the new process, thereby rapidly transforming the technical advantages of the present invention into market competitive advantages.

[0032] One-time solder resist printing significantly reduces equipment downtime and energy consumption. It avoids the cumulative alignment errors caused by multiple printing processes. In multiple printing processes, small deviations in alignment at each step accumulate layer by layer, leading to a decrease in the final pattern accuracy. Single-pass molding fundamentally eliminates this source of error. It ensures the alignment accuracy of the solder resist window and solder pad positions, improving the electrical safety and soldering yield of the product. The solder resist layer obtained by one-pass molding has a monolithic structure with a continuous and uniform internal molecular structure, eliminating interlayer interface problems. This not only improves its dielectric strength and chemical resistance but also greatly enhances its reliability and lifespan in thermal stress testing. It improves surface flatness and appearance quality; single-flow curing results in a smoother and flatter surface compared to multiple layers. This improves the appearance quality of the finished board, facilitating subsequent high-density mounting and reducing various problems caused by surface unevenness during subsequent assembly.

[0033] A processing technology for ultra-thick copper products, characterized by including the following steps:

[0034] S1. Preparation of inner core board: The core board is cleaned and its copper surface is roughened. Then, a liquid photosensitive wet film is covered on both sides of the core board and baked. The copper plate with film is exposed using an exposure machine and film pattern to complete the pattern transfer. Then, development is performed, and the exposed copper layer is removed by etching process. Film stripping is performed. Finally, the inner core board is obtained by scanning and inspection using automatic optical inspection equipment.

[0035] S2. Lamination: The inner core board and pre-etched copper plate are browned and then laminated with the prepreg. The prepreg is composed of two 106 type epoxy resin prepregs with a resin content of 72% and one glass fiber cloth prepreg with a resin content of 92%, resulting in a laminated structure. The laminated structure is pre-fixed using a riveting process. A steel plate is placed between each layer of the laminated structure, and it is fed into a hydraulic press for lamination. The heating rate during the lamination process is 1.76℃ / min, and the high pressure point is 110℃, resulting in a multilayer board. The multilayer board is then subjected to X-ray target inspection and edge trimming to obtain the laminated board.

[0036] S3. Post-processing: Drilling holes in the laminated plate, electroplating with copper, then transferring and etching the outer layer pattern, followed by one-time solder resist printing, exposure, development and curing, and finally surface tin spraying, testing and shaping to obtain ultra-thick copper products.

[0037] The pre-etched copper plate is prepared by the following steps:

[0038] Step 1, Pretreatment and Lamination: Use a sandblasting line at a speed of 3.0 m / min to remove the surface oxide layer of the 400um thick copper plate. After cleaning, use a laminating machine at a lamination temperature of 120℃ and a speed of 2.7 m / min to apply the dry film to the surface of the copper plate to obtain the laminated copper plate.

[0039] Step 2, Exposure and Development: Expose the coated copper plate using an exposure machine and film pattern to complete the pattern transfer. Then, develop the copper plate by using a sodium carbonate solution at a speed of 4 meters per minute to remove the unexposed dry film from the surface of the copper plate, thus obtaining the developed copper plate.

[0040] Step 3, Etching and Film Removal: Place the developed copper plate in an etching machine containing a 55°C hydrochloric acid oxidant solution and etch the developed copper plate at a speed of 1.5 m / min, controlling the residual etching thickness of the etched area to be 100-120 μm. Then, use sodium hydroxide solution to remove the residual dry film on the surface of the copper plate, and then wash and dry it to obtain a copper plate with controlled depth etching.

[0041] Step 4, Inspection and Decommissioning: Use automated optical inspection equipment to inspect the remaining thickness and pattern of the controlled-depth etched copper plate to obtain the pre-etched copper plate.

[0042] Example 2:

[0043] A processing technology for ultra-thick copper products, characterized by including the following steps:

[0044] S1. Preparation of inner core board: The core board is cleaned and its copper surface is roughened. Then, a liquid photosensitive wet film is covered on both sides of the core board and baked. The copper plate with film is exposed using an exposure machine and film pattern to complete the pattern transfer. Then, development is performed, and the exposed copper layer is removed by etching process. Film stripping is performed. Finally, the inner core board is obtained by scanning and inspection using automatic optical inspection equipment.

[0045] S2. Lamination: The inner core board and pre-etched copper plate are browned and then laminated with the prepreg. The prepreg is composed of two 106-type epoxy resin prepregs with a resin content of 72% and one glass fiber cloth prepreg with a resin content of 92%, resulting in a laminated structure. The laminated structure is pre-fixed using a riveting process. A steel plate is placed between each layer of the laminated structure, and it is fed into a hydraulic press for lamination. The heating rate during the lamination process is 1.76℃ / min, and the high pressure point is 105℃, resulting in a multilayer board. The multilayer board is then subjected to X-ray target inspection and edge trimming to obtain the laminated board.

[0046] S3. Post-processing: Drilling holes in the laminated plate, electroplating with copper, then transferring and etching the outer layer pattern, followed by one-time solder resist printing, exposure, development and curing, and finally surface tin spraying, testing and shaping to obtain ultra-thick copper products.

[0047] The pre-etched copper plate is prepared by the following steps:

[0048] Step 1, Pretreatment and Lamination: Use a sandblasting line at a speed of 2.5 m / min to remove the surface oxide layer of the 400um thick copper plate. After cleaning, use a laminating machine at a lamination temperature of 110℃ and a speed of 2.2 m / min to apply the dry film to the surface of the copper plate to obtain the laminated copper plate.

[0049] Step 2, Exposure and Development: Expose the coated copper plate using an exposure machine and film pattern to complete the pattern transfer. Then, develop the copper plate by using a sodium carbonate solution at a speed of 3.5 meters per minute to remove the unexposed dry film from the surface of the copper plate, resulting in a developed copper plate.

[0050] Step 3, Etching and Film Removal: Place the developed copper plate in an etching machine containing a 50°C hydrochloric acid oxidant solution and etch the developed copper plate at a speed of 1 meter / minute, controlling the residual etching thickness of the etched area to be 100-120 μm. Then, use sodium hydroxide solution to remove the residual dry film on the surface of the copper plate, and then wash and dry it to obtain a copper plate with controlled depth etching.

[0051] Step 4, Inspection and Decommissioning: Use automated optical inspection equipment to inspect the remaining thickness and pattern of the controlled-depth etched copper plate to obtain the pre-etched copper plate.

[0052] Example 3:

[0053] A processing technology for ultra-thick copper products, characterized by including the following steps:

[0054] S1. Preparation of inner core board: The core board is cleaned and its copper surface is roughened. Then, a liquid photosensitive wet film is covered on both sides of the core board and baked. The copper plate with film is exposed using an exposure machine and film pattern to complete the pattern transfer. Then, development is performed, and the exposed copper layer is removed by etching process. Film stripping is performed. Finally, the inner core board is obtained by scanning and inspection using automatic optical inspection equipment.

[0055] S2. Lamination: The inner core board and pre-etched copper plate are browned and then laminated with the prepreg. The prepreg is composed of two 106 type epoxy resin prepregs with a resin content of 72% and one glass fiber cloth prepreg with a resin content of 92%, resulting in a laminated structure. The laminated structure is pre-fixed using a riveting process. A steel plate is placed between each layer of the laminated structure, and it is fed into a hydraulic press for lamination. The heating rate during the lamination process is 1.76℃ / min, and the high pressure point is 115℃, resulting in a multilayer board. The multilayer board is then subjected to X-ray target inspection and edge trimming to obtain the laminated board.

[0056] S3. Post-processing: Drilling holes in the laminated plate, electroplating with copper, then transferring and etching the outer layer pattern, followed by one-time solder resist printing, exposure, development and curing, and finally surface tin spraying, testing and shaping to obtain ultra-thick copper products.

[0057] The pre-etched copper plate is prepared by the following steps:

[0058] Step 1, Pretreatment and Lamination: Use a sandblasting line at a speed of 3.5 m / min to remove the oxide layer on the surface of the 400um thick copper plate. After cleaning, use a laminating machine at a lamination temperature of 130℃ and a speed of 3.2 m / min to apply the dry film to the surface of the copper plate to obtain the laminated copper plate.

[0059] Step 2, Exposure and Development: Expose the coated copper plate using an exposure machine and film pattern to complete the pattern transfer. Then, develop the copper plate by using a sodium carbonate solution at a speed of 4.5 meters per minute to remove the unexposed dry film on the surface of the copper plate, thus obtaining the developed copper plate.

[0060] Step 3, Etching and Film Removal: Place the developed copper plate in an etching machine containing a 60°C hydrochloric acid oxidant solution and etch the developed copper plate at a speed of 2 meters per minute, controlling the residual etching thickness of the etched area to be 100-120 μm. Then, use sodium hydroxide solution to remove the residual dry film on the surface of the copper plate, and then wash and dry it to obtain a copper plate with controlled depth etching.

[0061] Step 4, Inspection and Decommissioning: Use automated optical inspection equipment to inspect the remaining thickness and pattern of the controlled-depth etched copper plate to obtain the pre-etched copper plate.

[0062] Comparative Example 1:

[0063] The difference from Example 1 is that no pre-etched copper plate is used, that is, the copper plate is not etched.

[0064] Test method:

[0065] 1. Solder resist ink consumption: Weigh the total ink consumption per unit area of ​​the board during the solder resist process.

[0066] 2. Solder resist adhesion: Tested according to the tape test method of IPC-TM-6502.4.28.1. Results are evaluated using a grading system from 0 to 5: 5B: Completely smooth edges, no peeling at grid edges (0% peeling); 4B: Minor peeling at grid intersections, peeling area less than 5%; 3B: Peeling area at grid edges or intersections between 5% and 15%; 2B: Peeling area between 15% and 35%; 1B: Peeling area between 35% and 65%; 0B: Peeling area greater than 65%.

[0067] 3. Thermal shock resistance of the solder resist layer: Tested according to IPC-TM-6502.6.7.2 standard, 300 cycles at -55~125℃.

[0068] Table 1

[0069]

[0070] As shown in Table 1, compared with Examples 1, 2, and 3, Comparative Example 1 exhibited a significantly increased consumption of solder resist ink, decreased solder resist adhesion, and reduced thermal shock resistance. Figure 6 The cross-sectional structural diagram demonstrates that the present invention significantly reduces the interface height difference between the outer layer circuit and the substrate from 400μm to 110μm through the copper plate pre-etching process. This structural change fundamentally reduces the consumption of solder resist ink and improves the adhesion and thermal shock resistance of the solder resist layer.

[0071] like Figure 1 As shown, by pre-etching the copper plate before lamination, a recessed region with a precise residual thickness (100 μm) was formed; as Figure 2 As shown, this is the inner core board structure after pattern etching is completed; Figure 1 copper coin and Figure 2 The inner core board is formed after being pressed together. Figure 3 The multilayer interconnect structure shown; in subsequent outer layer etching, the thin copper in the pre-etched area is easily removed, forming... Figure 4 The fine lines shown, with their minute height differences, lay the foundation for subsequent processes; ultimately, as... Figure 5 As shown, a uniform and dense solder resist layer can be perfectly formed on the circuit in one go, achieving excellent insulation protection and welding reliability; as Figure 6 As shown, compared with the copper product prepared by the prior art (right), the height difference between the outer layer circuit and the substrate of the copper product prepared by the present invention (left) is reduced from 400μm to 110μm, which is a fundamental improvement.

[0072] In summary, this invention solves the manufacturing challenges of ultra-thick copper PCBs from the structural source by using the core technology of "pre-etching," achieving the triple benefits of cost reduction, efficiency improvement, and quality enhancement.

[0073] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A process for processing an ultra-thick copper product, characterized by, The process comprises the following steps: S1, preparing the inner core board: clean the core board and roughen the copper surface, then cover the core board with a layer of liquid photosensitive wet film on both sides, bake, expose the film-coated copper board using an exposure machine and a film pattern to complete the pattern transfer, then develop, remove the exposed copper layer by etching process, remove the film, and finally scan and inspect using an automatic optical inspection device to obtain the inner core board; S2, lamination: brown the inner core board and the pre-etched copper board, then laminate with the prepreg to obtain a laminated structure, pre-fix the laminated structure using riveting process, place a steel plate between each layer of the laminated structure, and send it to the oil press for lamination, the heating rate during lamination is 1.76℃ / min, the high pressure point is 105-115℃, to obtain a multi-layer board, and then perform X-ray target inspection and edge catching to obtain a laminated board; S3, post-process: drill holes in the laminated board, perform copper plating, then perform outer layer pattern transfer and etching, then perform one-time solder mask printing, exposure, development and curing, and finally perform surface tin spraying, testing and molding to obtain a super-thick copper product.

2. The process of claim 1 wherein, The pre-etched copper board is prepared by the following steps: Step one, pretreatment and film pressing: use a sandblasting line to remove the surface oxide layer of a copper board with a thickness of 400um at a speed of 2.5-3.5m / min, after cleaning, use a film press to attach a dry film to the surface of the copper board to obtain a film-coated copper board; Step two, exposure and development: expose the film-coated copper board using an exposure machine and a film pattern to complete the pattern transfer, then develop, use a sodium carbonate solution to remove the unexposed dry film on the surface of the copper board to obtain a developed copper board; Step three, etching and film removal: place the developed copper board in an etching machine containing a hydrochloric acid oxidizing agent solution, etch the developed copper board at a speed of 1-2m / min, and control the etching residual thickness of the etched area to be 100-120um, then use a sodium hydroxide solution to remove the residual dry film on the surface of the copper board, and then perform water washing and drying to obtain a controlled depth etched copper board; Step four, inspection and grouping: use an automatic optical inspection device to inspect the residual thickness and pattern of the controlled depth etched copper board to obtain a pre-etched copper board.

3. The process of claim 1, wherein the thickness of the copper product is greater than 100 microns. The prepreg is composed of two 106 type epoxy resin prepregs with a resin content of 72% and one glass fiber cloth prepreg with a resin content of 92%.

4. The process of claim 2, wherein the thickness of the copper is greater than 100 microns. The film pressing temperature of the film press in step one is 110-130℃, and the speed is 2.2-3.2m / min.

5. The process of claim 2, wherein the thickness of the copper is greater than 100 microns. The development speed in step two is 3.5-4.5m / min.

6. The process of claim 2, wherein the thickness of the copper is greater than 100 microns. The temperature of the hydrochloric acid oxidizing agent solution in step three is 50-60℃.

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