Processing method of thick copper plate printed circuit board

Abstract

The invention relates to a processing method of a thick copper plate printed circuit board, which comprises the following steps of: providing at least one layer of thick copper core plate and carrying out pattern processing, and the copper thickness of the thick copper core plate is not less than 6OZ; carrying out browning treatment on the thick copper core plate subjected to pattern processing; a layer of adhesive film is attached to each of the two surfaces of the thick copper core plate subjected to brownification treatment; stacking the thick copper core plate attached with the adhesive film, at least one layer of common core plate and an adhesive sheet, and pressing to form a multi-layer plate blank; and performing subsequent through hole, circuit and surface treatment processing on the multi-layer plate blank to obtain the thick copper printed circuit board. The method has the beneficial effects that the glue filling effect of the thick copper core board can be improved, the production process is simplified, and the overall quality and reliability of the thick copper board printed circuit board are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuit board processing, in particular to a processing method of thick copper plate printed circuit board. BACKGROUND

[0002] With the advent of the AI era, the use of thick copper plate to make circuit boards in the PCB industry can well meet the application requirements of high-power circuits and efficient heat dissipation. Under the condition of keeping the line width unchanged, the loadable current of the line is proportional to the thickness of the line, that is, the thicker the line, the greater the loadable current; at the same time, keeping the current, power-on time, line width and other conditions unchanged, the heat generated by the line is inversely proportional to the thickness of the line. Therefore, designing the circuit board as a thick copper plate can reduce the heat generated and thus reduce the thermal strain caused by heat, greatly reducing the risk of board burning.

[0003] By using thick copper plate and combining special pattern processing and manufacturing methods, electroplating processes, and pressing methods, the product's large current carrying capacity, heat dissipation efficiency, and mechanical strength are significantly improved, making it an important development direction in the fields of high-power power supply, automotive electronics, and new energy systems. However, thick copper plates also have some shortcomings, such as thick copper filling, thick copper processing or etching during the process of making thick copper plates. The thicker the copper thickness of the thick copper plate, the more obvious the effect of using PP filling glue will decrease. If ink tree plugs are used for filling, multiple filling operations are required, which is high in operation cost, complex in process, and long in time cycle. SUMMARY

[0004] The purpose of the present application is to provide a processing method of thick copper plate printed circuit board which can improve the filling effect of thick copper core plate, simplify the production process, and improve the overall quality and reliability of thick copper plate printed circuit board.

[0005] A processing method of thick copper plate printed circuit board, comprising the following steps: providing at least one thick copper core plate and performing pattern processing, the copper thickness of the thick copper core plate is not less than 60Z; performing brown oxidation treatment on the thick copper core plate after pattern processing; attaching a layer of adhesive film to each surface of the thick copper core plate after brown oxidation treatment; stacking the thick copper core plate with attached adhesive film, at least one ordinary core plate, and an adhesive sheet, and pressing to form a multi-layer board blank; performing subsequent through-hole, line and surface treatment processing on the multi-layer board blank to obtain a thick copper printed circuit board.

[0006] In the above scheme, pattern processing replaces traditional chemical etching, avoiding problems such as loss of pattern precision due to severe side etching, and creating conditions for subsequent flattening and filling. An adhesive film is applied to the thick copper core board after browning treatment. The browning layer increases the micro-roughness of the copper surface. During subsequent lamination, the adhesive film softens and flows at high temperature, forming a strong mechanical bond and chemical adhesion with the browning layer, reconstructing a completely new, adhesive, and flat interface. The adhesive film, as a pre-fabricated, thickness-controllable flow medium, can perfectly fill the height differences caused by the thick copper pattern during lamination, eliminating voids and achieving a localized flattening effect that is difficult to achieve with traditional PP or resin inks. The thick copper core board with the adhesive film is then bonded to the ordinary... In the core board stacking process, during lamination, the adhesive film and bonding sheet flow together under hot pressing, cross-link and cure, firmly bonding the thick copper core board with huge rigidity differences to the thin ordinary core board into a uniform and dense whole. In this process, the adhesive film acts as a filler, stress buffer layer and adhesion promoter layer, thus stably manufacturing high-performance and high-reliability thick copper printed circuit boards in an efficient and low-cost manner. This process overcomes the defects of traditional PP filler such as voids and incomplete filling caused by insufficient fluidity, and avoids the problems of complex process, long cycle, poor bonding force and easy shrinkage and cracking caused by multiple ink resin filling. The surface of the thick copper board after adhesive film filling is smooth and flat, providing an ideal interface for subsequent lamination and greatly reducing the risk of lamination delamination.

[0007] Furthermore, in the step of providing at least one thick copper core board and performing pattern processing, wherein the copper thickness of the thick copper core board is not less than 6OZ, the pattern processing method is a combination of laser cutting or mechanical drilling and milling.

[0008] In the above-mentioned solutions, during the traditional chemical etching process, the etching solution dissolves copper while simultaneously eroding laterally, resulting in severe lateral etching. This lateral etching narrows the line width and reduces the spacing, making it difficult to precisely control the pattern size and leading to a loss of pattern precision. In contrast, pattern processing methods such as laser cutting or a combination of mechanical drilling and milling can operate precisely according to a pre-designed path. Precise patterns lay a good foundation for subsequent flattening and filling processes. In the processing of thick copper printed circuit boards, subsequent filling materials are needed to ensure the flatness and stability of the circuit board. If the pattern precision is out of control, the filling material may not be able to fill evenly, leading to problems such as voids and protrusions. However, when using adhesive film for filling, the precise pattern obtained through pattern processing allows the adhesive film to better adhere to the lines, filling the height differences of the thick copper pattern, eliminating voids, and improving the filling effect.

[0009] Furthermore, in the step of attaching a layer of adhesive film to each of the two surfaces of the thick copper core board after browning treatment, the adhesive film is a high glass transition temperature material with a thickness of 80 μm to 120 μm.

[0010] In the above scheme, the glass transition temperature is the critical temperature at which a material transitions from a glassy state to a highly elastic state. A high glass transition temperature film means that even at higher temperatures, the film can still maintain its glassy rigidity and stability. In subsequent circuit board processing, such as the lamination process of multilayer boards, which needs to be carried out under high temperature and high pressure conditions, a high Tg film can withstand the high temperature during the lamination process without excessive deformation or decomposition. This ensures that the film can achieve controllable and moderate flow during the lamination process to complete the filling and effectively bond the layers of the board together to form a solid overall structure. This helps to improve the manufacturing quality and reliability of the circuit board. The circuit patterns on thick copper core boards usually have a certain height difference. Thinner films may not be able to completely fill these differences, easily forming voids. On the other hand, films that are too thick may lead to overfilling, increasing costs and potentially affecting the overall thickness and performance of the circuit board. A film thickness of 80μm to 120μm can flow fully during hot pressing, filling the gaps caused by the thick copper patterns, achieving local planarization, and providing a good foundation for subsequent lamination processes.

[0011] Furthermore, the adhesive film is a solid epoxy resin adhesive film.

[0012] In the above solution, during the bonding process, the solid epoxy film can be quickly and accurately bonded to the surface of the thick copper core board using automated equipment, improving production efficiency and bonding accuracy. Although the solid epoxy resin film is solid at room temperature, it exhibits good thermal fluidity when heated to a certain temperature. During the pressing process, heating softens and flows the film, which can fully fill the height differences caused by the thick copper pattern and achieve local flattening. This thermal fluidity allows the film to adhere tightly to various parts of the circuit board, eliminating voids and gaps, and ensuring the uniformity and integrity of the filling effect. Moreover, by controlling the heating temperature and time, the fluidity of the film can be precisely adjusted to adapt to different processing requirements.

[0013] Furthermore, the step of attaching a layer of adhesive film to each of the two surfaces of the thick copper core board after browning treatment further includes: after attaching the adhesive film, performing a false pressing treatment on the composite of the thick copper core board and the adhesive film, so that the adhesive film is initially softened and fills the pattern gaps on the surface of the thick copper core board.

[0014] In the above solution, after the surface of the thick copper core board is patterned, there will be various height differences and gaps. During the dummy pressing process, the adhesive film softens initially due to heat, and has a certain degree of fluidity, allowing it to flow better into these pattern gaps. Compared with proceeding directly to subsequent processes without dummy pressing, dummy pressing allows the adhesive film to fill the gaps more fully, avoiding defects such as voids and bubbles. During dummy pressing, the initially softened adhesive film can better contact the surface of the thick copper core board, increasing the contact area and adhesion between the two. In the subsequent formal lamination process, this good initial adhesion can be strengthened, making the adhesive film and the thick copper core board firmly bonded together, improving the interlayer bonding strength of the circuit board. This helps prevent interlayer separation during use, improving product reliability and service life. The complex process of multiple adhesive filling, baking, and grinding is simplified into a single film application and dummy pressing process, ensuring a smooth and flat surface of the thick copper printed circuit board while reducing production steps, thereby improving production efficiency.

[0015] Furthermore, in the step of stacking the thick copper core board with the adhesive film attached to it with at least one ordinary core board and adhesive sheet, and pressing them together to form a multilayer board blank, the pressing process uses a positioning pin system for interlayer alignment.

[0016] In the above-mentioned solution, the PINLAM positioning pin system uses precision mechanical pins that penetrate pre-drilled positioning holes in each layer to physically force positioning of all layers, including thick copper core boards with adhesive film, ordinary core boards, and adhesive sheets, before pressing. This process minimizes the offset of the interlayer pattern in the X and Y directions, which is significantly better than the traditional non-pin pressing method that relies on the natural flow of PP resin for positioning. Thick copper core boards and ordinary core boards have significant differences in thickness, rigidity, and coefficient of thermal expansion. Without forced mechanical positioning, under the high temperature and pressure of pressing, the interlayer is prone to slippage due to uneven material flow, resulting in serious layer misalignment. The positioning pin system can ensure precise alignment of interconnecting holes, thereby achieving high-density and high-reliability electrical interconnection between thick copper core boards and ordinary core boards.

[0017] Furthermore, the subsequent processing of the multilayer slab blank for through-holes, circuits, and surface treatment to obtain a thick copper printed circuit board includes the following steps: Drill holes in the laminated multilayer slab to form through holes; The via is filled with copper by electroplating; The multilayer slab blank after being filled with electroplated copper shall be subjected to at least one full-board electroplating. The outer layer pattern is made on the multi-layer slab blank after full-board electroplating and then the pattern is electroplated. The outer layer circuitry is formed by etching the multilayer slab blank after pattern electroplating. Solder resist, text printing, surface treatment and shape processing are performed on multilayer slab blanks with outer circuitry.

[0018] In the above scheme, the multi-layer board produced by laminating a thick copper core board with adhesive film can be seamlessly connected with subsequent standard processes such as drilling, copper plating, and full-board electroplating. The overall production process is simplified. By combining copper plating, full-board electroplating, pattern electroplating, and etching, highly reliable high-current vertical interconnection and high-precision surface signal lines are simultaneously achieved on the complex stack composed of thick copper layers and ordinary layers. This enables the final product to have both strong power carrying capacity and complete signal processing capabilities.

[0019] Furthermore, in the step of electroplating copper filling the via, the copper thickness of the exit hole is controlled between 16μm and 23μm. In the step of at least one full-board electroplating of the multilayer board blank after electroplating copper filling, a second full-board electroplating is performed, and the board surface is brushed and micro-etched before the second electroplating. Finally, the copper thickness of the exit board surface is controlled between 50μm and 59μm.

[0020] In the above scheme, controlling the copper thickness of the vias to 16μm to 23μm provides a stable and low-resistance electrical connection between the layers of the multilayer board. The appropriate copper thickness ensures smooth current transmission in the vias, reducing resistance loss and heat generation during signal transmission. For high-frequency signals, a stable copper thickness in the vias helps reduce signal attenuation and distortion, ensuring signal integrity and accuracy. Finally, controlling the copper thickness of the board surface to 50μm to 59μm meets the requirements of thick copper printed circuit boards for high current carrying capacity. A thicker copper layer on the board surface reduces the resistance of the circuit, resulting in less heat generated when the circuit carries a large current, avoiding circuit damage and performance degradation due to overheating, and improving the electrical stability of the circuit board in high-power application scenarios.

[0021] Furthermore, the copper thickness of the thick copper core plate is 12OZ and the thickness is 0.4mm.

[0022] In the above solution, the 12OZ copper thickness allows the thick copper core board to carry a large current without generating excessive heat. The thicker copper layer reduces the circuit resistance. According to Joule's law, lower resistance means less heat generated under the same current and time, thus avoiding circuit damage and performance degradation caused by overheating and ensuring the stable operation of electronic equipment under high power conditions. Lower resistance reduces signal attenuation and distortion during transmission, improving signal integrity. The 12OZ copper thickness and 0.4mm thickness specification of the thick copper core board can better adapt to manufacturing processes such as drilling, electroplating, and etching, improving production efficiency and product quality.

[0023] Furthermore, in the step of drilling holes in the multilayer slab after pressing to form through holes, the drilling includes mechanical through hole drilling and / or laser blind hole drilling, and the ratio of the lower diameter to the upper diameter of the laser blind hole is not less than 0.7.

[0024] In the above solutions, whether it is a mechanical through-hole or a laser blind hole, precise drilling can ensure the quality of the through-hole. For laser blind holes, a ratio of the lower diameter to the upper diameter of not less than 0.7 means that the shape of the blind hole is relatively regular and the conductive channel formed after internal copper plating is relatively uniform. This helps to reduce the resistance of the through-hole, reduce the energy loss of the signal during transmission, and ensure that the signal can be transmitted stably and efficiently between different layers. Especially for high-frequency signals, it can effectively reduce signal attenuation and distortion and improve signal integrity.

[0025] This invention provides a processing method for thick copper plate printed circuit boards, which has the beneficial effects of improving the glue filling effect of thick copper core boards, simplifying the production process, and improving the overall quality and reliability of thick copper plate printed circuit boards. Replacing traditional chemical etching with pattern processing avoids problems such as loss of pattern precision due to severe side etching, creating conditions for subsequent flattening and filling. After browning treatment, an adhesive film is attached to the thick copper core board. The browning layer increases the micro-roughness of the copper surface. During subsequent lamination, the adhesive film softens and flows at high temperature, forming a strong mechanical bond and chemical combination with the browning layer, reconstructing a new, adhesive, and flat interface. As a pre-made, thickness-controllable flow medium, the adhesive film can perfectly fill the height differences caused by the thick copper pattern during lamination, eliminating voids and achieving a localized flattening effect that is difficult to achieve with traditional PP or resin inks. Thick copper core boards coated with adhesive film are stacked with ordinary core boards via adhesive sheets. During lamination, the adhesive film and adhesive sheets flow together under hot pressing, cross-link and cure, firmly bonding the thick copper core board with its significant difference in rigidity to the thin ordinary core board into a uniform and dense whole. In this process, the adhesive film acts as a filler, stress buffer layer and adhesion promoter layer, thus stably manufacturing high-performance and high-reliability thick copper printed circuit boards in a high-efficiency and low-cost manner. This process overcomes the defects of traditional PP filler, such as voids and incomplete filling due to insufficient fluidity, and avoids the problems of complex processes, long cycles, poor adhesion, and easy shrinkage and cracking caused by multiple ink resin build-up. The surface of the thick copper board after adhesive film filling is smooth and flat, providing an ideal interface for subsequent lamination and greatly reducing the risk of lamination delamination. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating a method for processing a thick copper plate printed circuit board according to one embodiment.

[0027] Figure 2 A flowchart of step S5 in one embodiment. Figure 3This is a schematic diagram of a multilayer slab in one embodiment.

[0028] The following are the symbols in the attached diagram: 1. Thick copper core board; 2. Adhesive film. Detailed Implementation

[0029] The following will describe in further detail a method for processing thick copper plate printed circuit boards according to the present invention, with reference to specific embodiments and accompanying drawings.

[0030] like Figure 1 As shown in a preferred embodiment, a method for processing a thick copper plate printed circuit board according to the present invention includes the following steps: S1. Provide at least one thick copper core plate and perform pattern processing, wherein the copper thickness of the thick copper core plate is not less than 6OZ; S2. Perform browning treatment on the thick copper core board after completing the graphic processing; S3. A layer of adhesive film is attached to each of the two surfaces of the thick copper core board that has undergone browning treatment; S4. The thick copper core board with the adhesive film attached is stacked with at least one ordinary core board and adhesive sheet, and then pressed together to form a multi-layer board blank. S5. Perform subsequent through-hole, circuit and surface treatment processing on the multilayer board blank to obtain a thick copper printed circuit board.

[0031] In this embodiment, pattern processing replaces traditional chemical etching, avoiding problems such as loss of pattern precision due to severe side etching, and creating conditions for subsequent flattening and filling. An adhesive film is attached to the thick copper core board after browning treatment. The browning layer increases the micro-roughness of the copper surface. During subsequent lamination, the adhesive film softens and flows at high temperature, forming a strong mechanical bond and chemical adhesion with the browning layer, reconstructing a completely new, adhesive, and flat interface. As a pre-fabricated, thickness-controllable flow medium, the adhesive film perfectly fills the height differences caused by the thick copper pattern during lamination, eliminating voids and achieving a localized flattening effect that is difficult to achieve with traditional PP or resin inks. The thick copper core board with the adhesive film is then bonded to the ordinary... In the core board stacking process, during lamination, the adhesive film and bonding sheet flow together under hot pressing, cross-link and cure, firmly bonding the thick copper core board with huge rigidity differences to the thin ordinary core board into a uniform and dense whole. In this process, the adhesive film acts as a filler, stress buffer layer and adhesion promoter layer, thus stably manufacturing high-performance and high-reliability thick copper printed circuit boards in an efficient and low-cost manner. This process overcomes the defects of traditional PP filler such as voids and incomplete filling caused by insufficient fluidity, and avoids the problems of complex process, long cycle, poor bonding force and easy shrinkage and cracking caused by multiple ink resin filling. The surface of the thick copper board after adhesive film filling is smooth and flat, providing an ideal interface for subsequent lamination and greatly reducing the risk of lamination delamination.

[0032] In step S1, providing at least one thick copper core board and performing pattern processing, wherein the copper thickness of the thick copper core board is not less than 6 oz, the pattern processing method is a combination of laser cutting or mechanical drilling and milling. In traditional chemical etching, the etching solution dissolves copper while eroding laterally, resulting in severe lateral etching. Lateral etching narrows the line width and reduces the spacing, making it difficult to accurately control the pattern size, thus causing pattern accuracy to be out of control. However, pattern processing methods such as laser cutting or mechanical drilling combined with milling can operate precisely according to a pre-designed path. Precise patterns lay a good foundation for subsequent flattening and filling processes. In the processing of thick copper printed circuit boards, subsequent filling materials are needed to ensure the flatness and stability of the circuit board. If the pattern accuracy is out of control, the filling material may not be able to fill evenly, leading to problems such as voids and protrusions. The precise pattern obtained by pattern processing allows the adhesive film to better adhere to the circuit when using film filling, filling the height difference of the thick copper pattern, eliminating voids, and improving the filling effect.

[0033] In step S3, a layer of adhesive film is attached to each of the two surfaces of the browned thick copper core board. The adhesive film is a high glass transition temperature material with a thickness of 80 μm to 120 μm. The glass transition temperature (Tg) is the critical temperature at which a material transitions from a glassy state to a highly elastic state. A high Tg adhesive film means that it can maintain its glassy rigidity and stability even at higher temperatures. In subsequent circuit board manufacturing processes, such as the lamination of multilayer boards, which require high temperature and pressure, a high Tg adhesive film can withstand the high temperatures during lamination without excessive deformation or decomposition. This ensures controlled and appropriate flow of the film during lamination to complete the filling process and effectively bond the layers together to form a robust overall structure. This contributes to improving the manufacturing quality and reliability of the circuit board. Circuit patterns on thick copper core boards typically have height differences. Thinner adhesive films may not be able to completely fill these differences, easily creating voids. Conversely, excessively thick films may lead to overfilling, increasing costs and potentially affecting the overall thickness and performance of the circuit board. An adhesive film thickness of 80μm to 120μm allows for sufficient flow during hot pressing, filling the gaps created by the thick copper patterns and achieving localized planarization, providing a good foundation for subsequent lamination processes.

[0034] like Figure 1As shown, in some embodiments, the adhesive film is a solid epoxy resin adhesive film. During the bonding process, the solid adhesive film can be quickly and accurately bonded to the surface of the thick copper core board using automated equipment, improving production efficiency and bonding accuracy. Although the solid epoxy resin adhesive film is solid at room temperature, it exhibits good thermal fluidity when heated to a certain temperature. During the pressing process, heating softens and flows the adhesive film, which can fully fill the height differences caused by the thick copper pattern, achieving local flattening. This thermal fluidity allows the adhesive film to adhere tightly to various parts of the circuit board, eliminating voids and gaps, and ensuring the uniformity and integrity of the filling effect. Moreover, by controlling the heating temperature and time, the fluidity of the adhesive film can be precisely adjusted to adapt to different processing requirements.

[0035] In step S3, where an adhesive film is attached to each of the two surfaces of the thick copper core board after browning treatment, the process also includes: S31. After attaching the adhesive film, the composite of the thick copper core board and the adhesive film is subjected to a false pressing treatment so that the adhesive film is initially softened and fills the pattern gaps on the surface of the thick copper core board.

[0036] After patterning, the surface of a thick copper core board will have various height differences and gaps. During the dummy-press process, the adhesive film softens under heat and becomes more fluid, allowing it to flow better into these gaps. Compared to proceeding directly to subsequent processes without dummy-press, dummy-press allows the adhesive film to fill the gaps more fully, avoiding defects such as voids and bubbles. During dummy-press, the initially softened adhesive film can better contact the surface of the thick copper core board, increasing the contact area and adhesion between them. In the subsequent formal lamination process, this good initial adhesion can be strengthened, firmly bonding the adhesive film to the thick copper core board and improving the interlayer bonding strength of the circuit board. This helps prevent interlayer separation during use, improving product reliability and lifespan. The complex process of multiple adhesive filling, baking, and grinding is simplified into a single film application and dummy-press process, ensuring a smooth and flat surface on the thick copper printed circuit board while reducing production steps, thereby improving production efficiency.

[0037] In some embodiments, in step S4, the thick copper core board with the adhesive film attached is stacked with at least one ordinary core board and adhesive sheet, and then pressed to form a multilayer board blank. The pressing process uses a positioning pin system for interlayer alignment. Positioning pin systems like PINLAM use precision mechanical pins that penetrate pre-drilled positioning holes in each layer to physically force-position all layers, including the thick copper core board with adhesive film, the ordinary core board, and the adhesive sheet, before pressing. This process minimizes the offset of the interlayer pattern in the X and Y directions, which is significantly better than the traditional non-pin pressing method that relies on the natural flow of PP resin for positioning. The thick copper core board and the ordinary core board have significant differences in thickness, rigidity, and coefficient of thermal expansion. Without forced mechanical positioning, under the high temperature and pressure of pressing, the interlayer is prone to slippage due to uneven material flow, resulting in severe layer misalignment. The positioning pin system can ensure precise alignment of interconnect holes, thereby achieving high-density and high-reliability electrical interconnection between the thick copper core board and the ordinary core board.

[0038] like Figure 2 As shown, in step S5, the subsequent processing of the multilayer board blank for through holes, circuits, and surface treatment to obtain a thick copper printed circuit board includes the following steps: S51. Drill holes in the multilayer slab blank after pressing to form through holes; S52. Electroplating copper fills the through hole; S53. Perform at least one full-board electroplating on the multilayer slab blank after it has been filled with copper plating. S54. Create an outer layer pattern on the multi-layer slab blank after full-board electroplating and perform pattern electroplating. S55. Etch the multilayer board blank after pattern electroplating to form the outer layer circuit; S56. Perform solder resist, text printing, surface treatment and shape processing on multilayer slab blanks with outer layer circuits.

[0039] The multilayer board produced by laminating a thick copper core board with adhesive film can be seamlessly connected with subsequent standard processes such as drilling, copper plating, and full-board electroplating. The overall production process is simplified. By combining copper plating, full-board electroplating, pattern electroplating, and etching, highly reliable high-current vertical interconnection and high-precision surface signal lines are simultaneously achieved on the complex stack composed of thick copper layers and ordinary layers. This gives the final product both strong power carrying capacity and complete signal processing capabilities.

[0040] In step S52, when the through hole is filled with copper by electroplating, the copper thickness of the exit hole is controlled between 16μm and 23μm. In the process of at least one full-board electroplating step on the multilayer board blank after copper electroplating, a second full-board electroplating is performed. Before the second electroplating, the board surface is brushed and micro-etched. Finally, the copper thickness of the exit board surface is controlled between 50μm and 59μm.

[0041] Controlling the copper thickness of vias to between 16μm and 23μm provides a stable and low-resistance electrical connection between layers of a multilayer board. Appropriate copper thickness ensures smooth current transmission through the vias, reducing resistance loss and heat generation during signal transmission. For high-frequency signals, stable via copper thickness helps reduce signal attenuation and distortion, ensuring signal integrity and accuracy. Finally, controlling the copper thickness of the board surface to between 50μm and 59μm meets the requirements of thick copper printed circuit boards for high current carrying capacity. A thicker copper layer reduces circuit resistance, resulting in less heat generation when carrying high currents, preventing circuit damage and performance degradation due to overheating, and improving the electrical stability of the circuit board in high-power applications.

[0042] In this embodiment, the copper core board has a copper thickness of 12 oz and a thickness of 0.4 mm. The 12 oz copper thickness allows the thick copper core board to carry a large current without generating excessive heat. The thicker copper layer reduces circuit resistance. According to Joule's law, lower resistance means less heat generated under the same current and time, thus avoiding circuit damage and performance degradation due to overheating and ensuring stable operation of electronic equipment under high power conditions. Lower resistance reduces signal attenuation and distortion during transmission, improving signal integrity. The 12 oz copper thickness and 0.4 mm thickness specifications of the thick copper core board better adapt to manufacturing processes such as drilling, electroplating, and etching, improving production efficiency and product quality.

[0043] In step S51, drilling is performed on the laminated multilayer slab to form through holes. The drilling includes mechanical through-hole drilling and / or laser blind hole drilling, and the ratio of the lower diameter to the upper diameter of the laser blind hole is not less than 0.7. Whether it's a mechanical through-hole or a laser blind hole, precise drilling ensures the quality of the through hole. For laser blind holes, a lower diameter to upper diameter ratio of not less than 0.7 means the blind hole has a more regular shape, and the conductive channels formed after internal copper plating are more uniform. This helps reduce the resistance of the through hole, reduce energy loss during signal transmission, and ensure stable and efficient signal transmission between different layers. Especially for high-frequency signals, it effectively reduces signal attenuation and distortion, and improves signal integrity.

[0044] The following example, using the manufacture of an eight-layer thick copper printed circuit board for a high-power power module, illustrates the specific implementation of this invention: Reference Figure 3 In this embodiment, the product is an eight-layer board, with the stacking sequence being L1 / L2 / L3 / L4 / L5 / L6 / L7 / L8. Wherein: Layers L4 and L5 are power layers that need to carry large currents, and use FR-4 thick copper clad laminate with a copper thickness of 12OZ, corresponding to a thickness of about 0.4mm, as the thick copper core board.

[0045] Layers L2 / L3 and L6 / L7 are signal layers, using a standard FR-4 double-sided copper-clad laminate with a copper thickness of 1OZ as the ordinary core board.

[0046] The adhesive material used is high-TG prepreg (PP).

[0047] The filler material is a solid epoxy resin film with a high glass transition temperature (Tg≥170℃) and a thickness of 100μm.

[0048] Step 1: Creating the inner layer pattern (corresponding to the ordinary signal layer): The ordinary core boards of L2 / L3 and L6 / L7 are cut into blanks, followed by inner layer pattern transfer. After exposure, development, etching and film removal, the circuit pattern required by the design is formed, and a target for subsequent alignment is made. After inner layer optical inspection (AOI) is completed, the core boards are cleaned for later use.

[0049] Step 2: Thick copper layer pattern processing: For the L4 and L5 thick copper core boards, which are 0.4mm thick, the pattern processing is performed using a combination of internal mechanical drilling and forming milling. First, in the area where copper needs to be removed, a mechanical drill is used to drill a dense array of through holes, which significantly weakens the structural strength of the copper layer in that area. Then, a milling machine is used to mill along the outline of the design, removing the copper area that has been weakened by drilling, forming the required thick copper pattern, such as a large power block. During the processing, dimensional tolerances and burrs must be strictly controlled.

[0050] Step 3: Browning and Adhesive Film Application: The L2 / L3 and L6 / L7 ordinary core boards with pre-made patterns are subjected to conventional browning treatment. The L4 and L5 thick copper core boards that have completed the graphic processing are browned. Then, a 100μm thick high TG adhesive film is attached to each of the top and bottom surfaces. The size of the adhesive film is consistent with the size of the thick copper core board panel. After attachment, a dummy press is used for pre-pressing to soften the adhesive film and make it adhere tightly to the surface of the thick copper core board, so as to achieve filling and flatness.

[0051] Step 4: Stacking and Pressing: The boards are stacked in the following order: L2 / L3 ordinary core board, PP, L4 thick copper core board with adhesive film pre-applied on both sides, PP, L5 thick copper core board with adhesive film pre-applied on both sides, PP, and L6 / L7 ordinary core board. PP is used as the bonding medium between the layers. During the stacking process, the PINLAM positioning pin system is used to align the pins through the target holes on each layer to ensure precise alignment of the interlayer patterns. Then, vacuum hot pressing is performed. After pressing, the layer misalignment is confirmed by checking the offset of the four concentric circle targets.

[0052] Step 5: Drilling and Hole Metallization Laser drilling: Laser drilling is performed on the laminated board to form blind holes in layers L3-L4 and L5-L6, and the ratio of lower hole diameter to upper hole diameter (B / A) is controlled to be ≥0.7.

[0053] First copper plating for hole filling: Electroplating copper is applied to fill the blind holes, so that the copper thickness of the holes reaches 16μm to 23μm.

[0054] Second full-board electroplating: Before the second full-board electroplating, the board surface is brushed and micro-etched. Electroplating is then performed, controlling the process to increase the copper thickness of the holes by at least 10μm, with an average increase of 12μm; and to achieve a final copper thickness of 50μm to 59μm on the board surface. PTH slotting: According to the design, a milling machine is used to mill away the material between multiple PTH holes in a specific area to form a metallized slot. Third electroplating: Metallize the new wound surface created by the PTH milling groove and thicken the copper layer overall.

[0055] Step Six: Outer Layer Circuit Formation and Post-processing: Outer layer pattern and pattern electroplating: Outer layer pattern (L1 / L8) is made on the board surface and pattern electroplating is performed to thicken the copper layer of the circuit and solder pads, and tin is plated as an etching resist layer.

[0056] Etching: Unprotected copper is removed by alkaline etching (SES) to form the outer layer circuitry. The line width tolerance is controlled at ±20%, and the pad size tolerance is ±0.03mm.

[0057] Solder resist and text: Solder resist ink is applied by screen printing and exposed and developed to expose the solder pads, and then text markings are printed.

[0058] Surface treatment: The exposed pads are subjected to chemical nickel immersion gold (ENIG) treatment.

[0059] Molding and Testing: The final shape is milled out using a CNC milling machine, and electrical testing (E / T), four-wire testing and final appearance inspection (OQC) are carried out. After passing the inspection, the product is packaged.

[0060] Through the process described in this embodiment, an eight-layer printed circuit board with two 12OZ thick copper layers embedded in it was successfully manufactured. The thick copper plate has a smooth surface after being filled with adhesive film, and there are no voids or delamination during lamination. The thick copper layer and high-quality metallized holes enable the product to have both high current carrying capacity and high-precision signal transmission capability through the fine circuitry of the outer layer. The entire process simplifies the complex problem of thick copper filling into an efficient film lamination process, and is perfectly compatible with standard PCB post-processing, achieving high-quality and high-reliability production.

[0061] In the description of this invention, it should be understood that terms such as "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and 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. Therefore, they should not be construed as limiting this invention.

[0062] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0063] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0064] Although the description of the invention has been given in conjunction with the specific embodiments described above, it will be apparent to those skilled in the art that many substitutions, modifications, and variations can be made based on the foregoing. Therefore, all such substitutions, modifications, and variations are included within the spirit and scope of the appended claims.

Claims

1. A method for processing thick copper plate printed circuit boards, characterized in that, Includes the following steps: Provide at least one thick copper core plate and perform pattern processing, wherein the copper thickness of the thick copper core plate is not less than 6OZ; The thick copper core board after graphic processing is subjected to browning treatment; A layer of adhesive film is attached to each of the two surfaces of the thick copper core board that has undergone browning treatment; The thick copper core board with the adhesive film attached is stacked with at least one ordinary core board and adhesive sheet, and then pressed together to form a multi-layer board blank. The multilayer slab is then processed with through holes, wiring, and surface treatment to obtain a thick copper printed circuit board.

2. The processing method for thick copper plate printed circuit boards according to claim 1, characterized in that, In the step of providing at least one thick copper core board and performing pattern processing, wherein the copper thickness of the thick copper core board is not less than 6OZ, the pattern processing method is a combination of laser cutting or mechanical drilling and milling.

3. The processing method for thick copper plate printed circuit boards according to claim 2, characterized in that, In the step of attaching a layer of adhesive film to each of the two surfaces of the thick copper core board after browning treatment, the adhesive film is a high glass transition temperature material with a thickness of 80 μm to 120 μm.

4. The processing method for thick copper plate printed circuit boards according to claim 1, characterized in that, The adhesive film is a solid epoxy resin adhesive film.

5. The processing method for thick copper plate printed circuit boards according to claim 1, characterized in that, The step of attaching an adhesive film to each of the two surfaces of the thick copper core board after browning treatment further includes: after attaching the adhesive film, performing a dummy pressure treatment on the composite of the thick copper core board and the adhesive film, so that the adhesive film is initially softened and fills the pattern gaps on the surface of the thick copper core board.

6. The processing method for thick copper plate printed circuit boards according to claim 1, characterized in that, In the step of stacking the thick copper core board with the adhesive film attached to it with at least one ordinary core board and adhesive sheet, and pressing them together to form a multilayer board blank, the pressing process uses a positioning pin system for interlayer alignment.

7. The processing method for thick copper plate printed circuit boards according to claim 1, characterized in that, The process of subsequently processing the multilayer slab with through holes, circuits, and surface treatment to obtain a thick copper printed circuit board includes the following steps: Drill holes in the laminated multilayer slab to form through holes; The via is filled with copper by electroplating; The multilayer slab blank after being filled with electroplated copper shall be subjected to at least one full-board electroplating. The outer layer pattern is made on the multi-layer slab blank after full-board electroplating and then the pattern is electroplated. The outer layer circuitry is formed by etching the multilayer slab blank after pattern electroplating. Solder resist, text printing, surface treatment and shape processing are performed on multilayer slab blanks with outer circuitry.

8. The processing method for thick copper plate printed circuit boards according to claim 7, characterized in that, In the copper plating filling step of the via, the copper thickness of the exit hole is controlled between 16μm and 23μm. In the multilayer board blank after copper plating filling, at least one full-board electroplating step is performed, followed by a second full-board electroplating. Before the second electroplating, the board surface is brushed and micro-etched, and the final copper thickness of the exit board surface is controlled between 50μm and 59μm.

9. The processing method of the thick copper plate printed circuit board according to claim 1, wherein the copper thickness of the thick copper core board is 12OZ and the thickness is 0.4mm.

10. The processing method of thick copper plate printed circuit board according to claim 7, in the step of drilling holes in the multilayer board blank after lamination to form through holes, the drilling includes mechanical through hole drilling and / or laser blind hole drilling, and the ratio of the lower hole diameter to the upper hole diameter of the laser blind hole is not less than 0.7.

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