High-current-carrying circuit board and manufacturing method thereof

Abstract

The invention provides a high-current-carrying circuit board and a manufacturing method thereof, and relates to the technical field of PCB manufacturing, and the high-current-carrying circuit board comprises a PCB substrate, at least one current-carrying component and a mechanical fastener. A first mechanical connection position is arranged on the PCB substrate; the current-carrying component is used for carrying current and is provided with a second mechanical connection position; the current-carrying component and the PCB substrate are fixedly connected by the mechanical fastener through the first mechanical connection position and the second mechanical connection position, and the current-carrying component is electrically connected with the PCB substrate. The first mechanical connection position is arranged on the PCB substrate, the second mechanical connection position is arranged on the current-carrying component, and the first mechanical connection position and the second mechanical connection position are fixedly connected through the mechanical fastener, so that the problem that in the prior art, a large-size current-carrying component is difficult to reliably fix and easy to fall off or loosen, and then the performance and reliability of a circuit are affected is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of PCB manufacturing, and in particular, to a high-current-carrying circuit board. Background Art

[0002] With the rapid development of the new energy industry, the demand for high-power electrical equipment in fields such as electric vehicles, solar power generation, wind power generation, LED lighting, and industrial power systems is increasing day by day. These devices usually have a relatively high voltage level and a large current-carrying capacity, posing stringent requirements on the current-carrying capacity and heat dissipation performance of the circuit board. Due to the limitation of the copper foil thickness, traditional printed circuit boards (PCBs) are difficult to meet the conductive and heat dissipation requirements of high-power electrical equipment, which greatly limits the application of PCBs in the strong electricity industry.

[0003] In order to solve the problem of insufficient current-carrying capacity of traditional PCBs, the industry has developed a variety of technical solutions, mainly including:

[0004] 1. Multi-layer thick copper foil technology: The current-carrying capacity is improved by increasing the number of copper foil layers and the thickness of the PCB. However, when the copper foil thickness is too large (such as ≥12 oz or even ≥16 oz), the PCB lamination process is extremely difficult, the yield is difficult to guarantee, and the cost is extremely high. In addition, for small-sized pads, even with thick copper foil, their current-carrying capacity is still limited, and they are prone to charring and peeling under instantaneous high temperature or large current impact.

[0005] 2. Copper substrate technology: Using copper-based materials to make PCBs to improve heat dissipation performance. However, copper substrates usually can only achieve single-sided wiring, the heat dissipation effect of double-sided copper substrates is also limited, and the processing cost is high, with reliability problems.

[0006] Therefore, it is necessary to improve the existing high-current-carrying circuit board technology to overcome the defects of the existing technology. Summary of the Invention

[0007] To overcome the problems existing in the related art, one of the objectives of the present invention is to provide a high-current-carrying circuit board. The circuit board is provided with a first mechanical connection position on the PCB substrate, a second mechanical connection position on the current-carrying member, and the two are fixedly connected by mechanical fasteners, so as to overcome the problems in the existing technology that large-sized current-carrying members are difficult to be reliably fixed, are prone to falling off or loosening, and thus affect the circuit performance and reliability.

[0008] A high-current-carrying circuit board, characterized by comprising:

[0009] A PCB substrate, on which a first mechanical connection position is provided;

[0010] At least one current-carrying member for carrying current, on which a second mechanical connection position is provided;

[0011] A mechanical fastener that fixedly connects the current-carrying component to the PCB substrate through the first mechanical connection position and the second mechanical connection position, and the current-carrying component is electrically connected to the PCB substrate.

[0012] Furthermore, the first mechanical connection position and the second mechanical connection position are through holes or blind holes.

[0013] The structural form of through holes or blind holes provides installation space for the mechanical fastener and can guide the installation direction of the fastener. Through holes can directly penetrate the PCB substrate or the current-carrying component, and the connection state can be directly observed; while blind holes can prevent the fastener from penetrating the entire structure, are suitable for application scenarios with requirements for the thickness of the circuit board, and can improve the integration of the circuit board.

[0014] Furthermore, the mechanical fastener is a screw;

[0015] The first mechanical connection position is a first threaded hole provided on the PCB substrate;

[0016] The second mechanical connection position is a second threaded hole provided on the current-carrying component;

[0017] The screw is in threaded engagement with the first mechanical connection position and the second mechanical connection position.

[0018] Screw connection is a mature and reliable mechanical connection method, which has the advantages of high connection strength, repeatable disassembly and assembly, and easy operation. Through threaded engagement, the screw can tightly fix the PCB substrate and the current-carrying component together and provide sufficient pre-tightening force to prevent relative displacement between the two.

[0019] Furthermore, the second threaded hole is a countersunk hole or a counterbored hole.

[0020] The design of the countersunk hole or the counterbored hole can make the head of the screw sink or be buried into the surface of the current-carrying component, avoiding the head of the screw protruding from the surface of the current-carrying component. It can reduce the overall thickness of the circuit board, which is beneficial to the thin design of the circuit board; at the same time, it can also prevent the head of the screw from interfering or colliding with other components, improving the safety of the circuit board. The flat surface is also more beautiful, which is beneficial to the subsequent surface mounting process.

[0021] Furthermore, the first threaded hole is a resin-filled hole with a threaded structure on the inner wall.

[0022] The strength of threaded holes directly processed on the PCB substrate is limited and may not be enough to withstand the tightening force of the screws and the weight of the current-carrying components. However, by using resin-filled holes and processing threads on the inner wall of the resin holes, the toughness of the resin and the bite force of the threads can be used to improve the load-bearing capacity and anti-pullout ability of the threaded holes. Since the resin has good insulation properties, the resin-filled holes can also play an insulating role, avoiding short circuits between the screws and the circuits on the PCB substrate.

[0023] Furthermore, the current-carrying component is an L-shaped copper bar.

[0024] Copper has excellent electrical and thermal conductivity and is a common current-carrying material in circuit boards. Using copper bars as current-carrying components can effectively carry large currents and quickly dissipate the heat generated by the current, reducing the operating temperature of the circuit board. Compared with other shapes of current-carrying components (such as copper foil), copper bars have a larger cross-sectional area and higher mechanical strength, and can carry larger currents.

[0025] Furthermore, the current-carrying components are provided in plurality, and the plurality of current-carrying components are arranged in parallel.

[0026] In some high-power circuits, a single current-carrying component may not be able to meet the needs of current transmission. By setting up multiple current-carrying components arranged in parallel, the current can be dispersed to multiple current-carrying paths, reducing the current density of a single current-carrying component, thereby reducing the heat generation and improving the reliability of the circuit board. The parallel current-carrying components can achieve the current balancing effect, improve the uniformity of current distribution, and reduce the risk of local overheating. At the same time, compared with the traditional embedded copper block solution, multiple groups of current-carrying components in parallel can significantly increase the overall heat dissipation area and further enhance the heat dissipation effect of the current-carrying components.

[0027] Furthermore, the surface of the current-carrying component is plated with a nickel layer and / or a gold layer.

[0028] Both the nickel layer and the gold layer have good corrosion resistance and oxidation resistance. Plating the nickel layer and / or the gold layer on the surface of the current-carrying component can effectively protect the copper substrate from environmental corrosion and oxidation, and extend its service life. In addition, the gold layer also has excellent electrical conductivity and solderability, which can improve the electrical connection performance between the current-carrying component and other components. The nickel layer can serve as a barrier layer between the gold layer and the copper substrate to prevent copper atoms from diffusing into the gold layer and affecting the performance of the gold layer.

[0029] A second object of the present invention is to provide a method for manufacturing a circuit board, which is used to manufacture the high current-carrying circuit board as described above, and is characterized in that it comprises the following steps:

[0030] Drilling a hole at a position on the PCB substrate where the first mechanical connection position is to be formed;

[0031] Resin plug the drilled positions on the PCB substrate;

[0032] Perform machining on the cured resin holes to form the first mechanical connection position;

[0033] Perform machining on the current-carrying member to form the second mechanical connection position;

[0034] Use the mechanical fastener to fixedly connect the current-carrying member and the PCB substrate through the first mechanical connection position and the second mechanical connection position.

[0035] By respectively setting mechanical connection positions on the PCB substrate and the current-carrying member and using mechanical fasteners to fixedly connect the two, reliable fixation between the current-carrying member and the PCB substrate is achieved. Compared with the traditional bonding method, this method has higher connection strength and better reliability, and can effectively prevent the current-carrying member from falling off or loosening. At the same time, this method also forms mechanical connection positions through resin plugging holes and machining, improving the strength and precision of the connection positions.

[0036] Further, the current-carrying member is a copper bar;

[0037] The mechanical fastener is a screw;

[0038] The first mechanical connection position is a threaded hole;

[0039] The second mechanical connection position is a countersunk threaded hole;

[0040] The manufacturing method includes the following steps:

[0041] Perform surface treatment on the copper bar and perform machining at a predetermined position on the copper bar to form the countersunk threaded hole;

[0042] Cut and bake the PCB substrate;

[0043] Manufacture the inner layer pattern of the PCB substrate and mill a square groove for embedding the copper bar on one layer of the substrate;

[0044] Punch and laser cut the prepreg;

[0045] Cut the mirror steel plate and open a window, and the window corresponds to the square groove;

[0046] Stack and press the treated prepreg, each layer of the PCB substrate, and the mirror steel plate;

[0047] Drill through holes at predetermined positions on the PCB board;

[0048] Manufacture resin plug holes at the through holes to form resin holes;

[0049] Tap the resin hole to form an internal thread to form the threaded hole;

[0050] Embed the copper bar into the square groove, and use screws to pass through the threaded hole and the countersunk threaded hole to fix the copper bar to the PCB substrate by threaded connection.

[0051] The beneficial effects of the present invention are:

[0052] A high-current-carrying circuit board provided by the present invention. This high-current-carrying circuit board fixes the current-carrying component to the PCB substrate by a mechanical connection method through the setting of a first mechanical connection position, a second mechanical connection position and a mechanical fastener, rather than the traditional bonding method. This mechanical connection method has higher connection strength and better reliability, is not easily affected by environmental factors such as temperature, humidity and vibration, will not have problems such as aging, degumming and cracking, and can ensure full contact between the current-carrying component and the PCB substrate, ensuring the reliability of electrical connection. Fundamentally solve the problems of insufficient connection strength and low reliability existing in the traditional bonding method, especially in the application scenario of large-size current-carrying components, its advantages are more obvious. Description of the Drawings

[0053] Figure 1 is a cross-sectional schematic diagram of the connection part of the high-current-carrying circuit board provided in Embodiment 1 of the present application;

[0054] Figure 2 is a cross-sectional schematic diagram of the connection part of the high-current-carrying circuit board provided in Embodiment 2 of the present application;

[0055] Figure 3 is a cross-sectional schematic diagram of the connection part of the high-current-carrying circuit board provided in Embodiment 3 of the present application;

[0056] Figure 4 is a schematic diagram of multiple copper bars arranged side by side provided in Embodiment 1 of the application.

[0057] Reference Numerals:

[0058] 100, PCB substrate; 101, first mechanical connection position;

[0059] 200, current-carrying component; 102, second mechanical connection position;

[0060] 300, mechanical fastener. Detailed Embodiments

[0061] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0062] In the field of new energy, especially in high-power applications such as electric vehicles and solar power generation, electrical equipment has put forward higher and higher requirements for the current-carrying capacity and heat dissipation performance of circuit boards. The inventor has been engaged in the research and development of related products for a long time and found in practice that the traditional printed circuit board (PCB) technology has many limitations and is difficult to meet the needs of these high-power applications.

[0063] For example, in order to improve the current-carrying capacity, traditional PCBs usually increase the copper foil thickness or use copper substrates. However, too thick copper foil will lead to difficulties in PCB lamination, reduced yield, and increased costs; while copper substrates, although having good heat dissipation performance, have problems such as high processing difficulty, high cost, and limited applications. In addition, for some scenarios that require local large currents, traditional embedded copper blocks cannot meet the requirements due to size limitations (usually less than 40mm×100mm).

[0064] To address these problems, the inventor realized that it was necessary to break through the design and manufacturing ideas of traditional PCBs in order to develop a circuit board that truly meets the needs of high-power applications. The inventor proposed a brand-new high-current-carrying circuit board solution: by means of mechanical connection, a large-sized current-carrying component (such as a copper bar) is firmly combined with the PCB substrate, and reliable electrical connection is achieved. This solution can not only make full use of the excellent electrical conductivity and thermal conductivity of copper, but also overcome the limitations of traditional processes, achieving the goals of high current-carrying capacity, high heat dissipation, and high reliability.

[0065] Example 1

[0066] As Figure 1 and Figure 4 shown, this embodiment provides a high-current-carrying circuit board and its manufacturing method, and this circuit board is mainly applied to high-power electrical equipment such as charging switches of new energy products.

[0067] This high-current-carrying circuit board includes a PCB substrate 100, a current-carrying component 200, and a mechanical fastener 300.

[0068] The PCB substrate 100 is the basic material for carrying circuits and components.

[0069] The current-carrying component 200 is a conductor for carrying the main current, usually made of copper.

[0070] The mechanical fastener 300 is a component for fixedly connecting the current-carrying member 200 to the PCB substrate 100, such as screws, rivets, etc.

[0071] In this embodiment, the PCB substrate 100 is made of FR-4 material. FR-4 is a commonly used epoxy resin glass fiber cloth substrate, which has good mechanical strength, electrical insulation performance and heat resistance, and high cost performance. It is a commonly used material for PCB manufacturing.

[0072] The PCB substrate 100 is a multilayer structure, including multiple layers such as L1, L2, L3, L4, etc. The multilayer board design can increase the wiring density and achieve more complex functions.

[0073] A square groove for embedding the current-carrying member 200 is provided on the L1 layer (top layer). The square groove is precisely machined by a CCD router (CNC milling machine) to ensure dimensional accuracy and position accuracy. The size of the square groove is slightly larger (0.25 mm) than the single side of the copper bar, leaving an appropriate gap to facilitate the embedding of the copper bar and allowing a certain space for thermal expansion. The depth of the square groove is 2.0 ± 0.1 mm, which is precisely controlled to ensure the height consistency after the copper bar is embedded.

[0074] In this embodiment, the first mechanical connection position 101 is a first threaded hole, specifically a resin-filled hole with a threaded structure on the inner wall.

[0075] The current-carrying member 200 is an L-shaped copper bar. Copper has excellent electrical conductivity and thermal conductivity, and is an ideal current-carrying material. The L-shaped design can increase the contact area with the PCB substrate 100, reduce the contact resistance, and improve the heat dissipation effect.

[0076] One or more L-shaped copper bars can be provided. As Figure 4 shown, in this embodiment, multiple L-shaped copper bars are provided, and the multiple L-shaped copper bars are arranged side by side. The multiple L-shaped copper bars arranged side by side can greatly increase the overall heat dissipation area, and the heat dissipation effect is more than twice that of the traditional embedded copper block solution.

[0077] In this embodiment, the size of the copper bar is 200 mm × 100 mm × 3 mm (length × width × height). It far exceeds the size limit of the traditional embedded copper block (usually less than 40 mm × 100 mm) and can carry a larger current.

[0078] The surface of the copper bar is pre-treated by browning. The browning treatment forms a dense oxide layer on the copper surface, which can increase the bonding force between the copper and the resin, prevent delamination, and improve the reliability.

[0079] In this embodiment, the second mechanical connection position 102 is a second threaded hole, specifically a countersunk threaded hole. There are two countersunk threaded holes on the copper bar. The design of the countersunk hole is to allow the head of the screw to sink completely into the hole without protruding from the surface of the copper bar. This reduces the overall thickness of the circuit board, which is beneficial for achieving the thin design of the product. It also avoids interference or collision between the screw head and other components on the circuit board. It makes the surface of the copper bar flat, facilitating subsequent surface mounting processes (such as soldering, chip mounting, etc.).

[0080] The orifice of the countersunk hole can be conical, and the hole diameter gradually decreases along the depth direction, matching the shape of the screw head.

[0081] In this embodiment, the orifice of the countersunk hole is stepped. The diameter of the countersunk hole is 0.3 mm larger than the head diameter of the M3 screw, slightly larger than the screw head, which is convenient for screw installation and does not generate too large a gap. The depth of the countersunk hole is 0.2 mm deeper than the screw length, ensuring that after the screw is tightened, the head completely sinks into the hole and is lower than the solder mask surface of the PCB substrate 100, avoiding affecting the integrity of the solder mask.

[0082] The thread specification in the countersunk threaded hole is M3 thread, with a pitch of 0.35 mm and a root diameter of 2.7 mm. The M3 thread is a commonly used standard thread with good universality and interchangeability.

[0083] The upper surface and side surface of the copper bar are plated with a nickel layer and a gold layer, but the countersunk hole is not plated. The nickel layer serves as a barrier layer to prevent the diffusion of copper atoms into the gold layer and affect the performance of the gold layer. The gold layer has good corrosion resistance, oxidation resistance, and solderability, improving the reliability of the copper bar in harsh environments and enhancing its electrical connection performance with other components.

[0084] In this embodiment, the mechanical fastener 300 is an M3 screw. The screw is a commonly used fastener with advantages such as high connection strength, repeatable disassembly and assembly, and easy operation. It cooperates with the countersunk threaded hole to firmly fix the copper bar in the square groove of the PCB substrate 100. The length of the screw is 0.1 mm shorter than the thickness of the PCB board (including the embedding depth of the copper bar). This ensures that after the screw is tightened, the tip does not protrude beyond the other side of the PCB substrate 100, avoiding interference with other components or causing safety hazards such as short circuits.

[0085] It should be noted that in the field of high-power and high-current applications, PCB design has always faced a severe challenge: how to achieve reliable integration of large-sized current carriers on circuit boards. Although traditional PCB manufacturing processes, such as etching, lamination and electroplating, can handle small-sized copper foils or embedded copper blocks, they will encounter a series of problems such as difficult pressing, mismatched thermal expansion coefficients, and poor connection reliability when facing large-sized current carriers (such as copper bars with a length and width of more than 40mm x 100mm), resulting in low yield, short product life, and great safety hazards. These technical bottlenecks have seriously hindered the application of PCBs in the high-power field, making it impossible for the industry to adopt large-sized current carriers to meet the growing high-performance requirements. In order to break through this dilemma, the inventors have taken a different approach and no longer stick to the traditional PCB manufacturing ideas, but have creatively proposed a new mechanical connection solution - "mechanical tapping + countersunk hole process + screw fixing". This innovative solution cleverly avoids all the drawbacks of traditional processes and uses mechanical fastening to achieve high-strength, high-reliability, and low-thermal resistance connections between large-size current carriers and PCBs. It can not only carry currents of 100A or even higher, but also significantly improves the long-term stability and safety of the product. It has opened up a new path for high-power PCB design, filled the gap in the industry, and is of great technological breakthrough significance.

[0086] The manufacturing process of the high current-carrying circuit board in this embodiment is as follows:

[0087] Cut the board → bake the board → drill the positioning hole → make the L2 layer graphics → CCD gong machine gongs out the square groove of the L1 layer → browning the copper strip → LOW FLOW PP punching → PP laser cutting → make graphics on the L3 layer, only make the board edge target on the L4 layer → PCB mirror steel plate cutting window processing → pressing → drilling → resin plugging holes + cutting overflow glue → drilling countersunk holes at the tapping position of the current-carrying copper strip → mechanical tapping → screw fixing → copper deposition + negative film whole board electroplating → outer layer LDI circuit graphics → acid etching → outer layer AOI → solder mask (spraying, no silk screen printing, LDI exposure) → character printing + baking board → whole board gold plating → CNC molding (laser cutting molding) → flying probe electrical measurement → FQC → FQA → packaging

[0088] The specific steps include:

[0089] Step S1: Processing of PCB substrate 100:

[0090] Step S1.1, cutting and baking: cutting the PCB substrate 100 made of FR-4 material into required sizes, and baking the boards to remove moisture and improve dimensional stability.

[0091] Step S1.2, L2 layer pattern production: through exposure, development, etching and other processes, the required circuit pattern is formed on the L2 layer.

[0092] Step S1.3, Machining the Square Groove on Layer L1: Use a CCD router (CNC milling machine) to precisely machine a square groove on Layer L1 for embedding the L-shaped copper bar. The CCD router features high precision and high efficiency, which can ensure the dimensional accuracy and positional accuracy of the square groove.

[0093] Step S1.4, Fabricating the Patterns on Layers L3 and L4: Fabricate the circuit pattern on Layer L3, and only fabricate the board edge targets (for positioning in subsequent processes) on Layer L4.

[0094] Step S2, Treatment of the Prepreg (PP):

[0095] Step S2.1, Punching: Punch the LOW FLOW PP (low fluidity prepreg). The function of PP is to fill the gaps between layers during the PCB lamination process and play the roles of bonding and insulation. The size of the punched hole is slightly larger than the single side of the L-shaped copper block (0.2 mm) to leave space for the thermal expansion of the copper bar.

[0096] Step S2.2, Laser Cutting: Perform laser cutting on the PP to further precisely control the shape and size of the PP, making it more compatible with the shape of the PCB substrate 100 and the copper bar.

[0097] Step S3, Treatment of the Mirror Steel Plate:

[0098] Step S3.1, Cutting and Windowing: Cut the mirror steel plate and open windows at the positions corresponding to the copper bars. The function of the mirror steel plate is to provide a flat surface during the PCB lamination process and prevent resin from overflowing. The size of the window is slightly larger than the single side of the L-shaped copper bar (0.1 mm).

[0099] Step S3.2, Additional Steel Plate: Prepare an additional steel plate with a thickness of 1.0 mm. Since the thickness of the copper bar (3.0 mm) is greater than the depth of the square groove on Layer L1 (2.0 mm), the copper bar will protrude 1.0 mm above the PCB board surface after being embedded. Therefore, an additional steel plate is needed to compensate for this height difference to ensure uniform stress during lamination.

[0100] Step S4, Lamination and Pressing:

[0101] Step S4.1, Lamination: Stack the prepreg (PP), each layer of the PCB substrate 100 (L1, L2, L3, L4), and the mirror steel plates (including an additional one) together in a specific order.

[0102] Step S4.2, Pressing: Place the stacked materials into a hot press and perform pressing under high temperature and high pressure. During the pressing process, the PP melts and flows, filling the gaps between layers and firmly bonding the layers together.

[0103] Step S5, Fixing the Copper Bar:

[0104] Step S5.1, Resin Plugging Holes and Tapping: Drill through holes at predetermined positions on the PCB board (the through holes corresponding to the countersunk holes of the copper bars); Make resin plugging holes at the through holes to form resin holes; Resin plugging holes can improve the reliability of threaded connections and avoid the problem of insufficient tapping strength directly on the PCB substrate. Tap the resin holes to form internal threads matching the screws.

[0105] Step S5.2, Drilling and Tapping Copper Bars: Drill and tap each copper bar to form two countersunk screw holes, and the distance between the two countersunk screw holes is 75 mm.

[0106] Step S5.3, Screw Fastening: Insert the L-shaped copper bar into the square groove, and use M3 screws to fix the copper bar to the PCB substrate 100 through threaded connections. The tightening torque of the screws needs to be appropriately controlled to ensure firm connection while avoiding damaging the PCB substrate 100 or the copper bar. The height of the inserted screws is 0.2 mm lower than the current-carrying copper bar, and there should be no protrusion. It needs to be confirmed by magnifying glass and hand touch feeling / slicing;

[0107] Step S6, Immersion Copper + Negative Film Whole-board Electroplating:

[0108] Step S6.1, Immersion Copper: Deposit a thin layer of chemical copper on the walls and surfaces of all holes on the PCB board to metallize the non-conductive surfaces (such as hole walls) and provide a conductive basis for subsequent electroplating.

[0109] Step S6.2, Negative Film Whole-board Electroplating: The surface copper thickness of the electroplated copper is more than 70 um, and the hole copper is greater than or equal to 50 um. The thick copper can better match the high-current-carrying and high-heat-dissipating copper bars.

[0110] Step S7, Outer-layer LDI Circuit Pattern Making:

[0111] Use laser direct imaging (LDI) technology to make fine circuit patterns on the outer layer. The LDI technology has the characteristics of high precision and high resolution and is suitable for the manufacture of high-density circuit boards. The circuit design is relatively sparse, with a line width / line pitch of 0.3 mm / 0.3 mm, and the distance between the circuit and the edge of the embedded copper bar is ≥50 mm or more. This is to avoid the circuit being too close to the copper bar and affecting the electrical performance and to leave enough safety distance.

[0112] Step S8, Acidic Etching:

[0113] Use acidic etching solution to etch away the unnecessary copper layers and leave the required circuit patterns.

[0114] Step S9, Outer-layer AOI (Automated Optical Inspection):

[0115] Use automated optical inspection equipment to check whether there are defects in the outer-layer circuit patterns, such as short circuits, open circuits, and notches.

[0116] Step S10, Solder Masking:

[0117] Apply a solder mask layer (usually green ink) on the surface of the PCB board to protect the circuit pattern from environmental influences and prevent bridging during soldering. Due to the presence of copper bars, the solder mask layer is made by spraying instead of the traditional screen printing method. The solder mask LDI is directly exposed without using a film.

[0118] Step S11, Character Printing + Baking the Board:

[0119] Print characters (such as product model, production date, etc.) on the surface of the PCB board and perform baking treatment to cure the character ink.

[0120] Step S12, Nickel-Gold Plating for the Whole Board:

[0121] The nickel thickness is greater than or equal to 5 μm, and the gold thickness is 0.1 μm, which improves the corrosion resistance in harsh environments (such as high temperature and high humidity - 40°C to +155°C) and enhances the solderability and contact reliability.

[0122] Step S13, CNC Milling:

[0123] Use a CNC milling machine or a laser cutting machine to cut the PCB board into the required shape. Laser cutting controls the position accuracy, achieving a dimensional tolerance of ±0.05 mm, which improves the dimensional accuracy requirements for assembly.

[0124] Step S14, Flying Probe Electrical Testing:

[0125] Use a flying probe tester to perform electrical performance testing on the PCB board to check for defects such as open circuits and short circuits.

[0126] Step S15, FQC (Final Quality Control):

[0127] Conduct a comprehensive quality inspection on the PCB board, including appearance inspection, dimensional measurement, performance testing, etc.

[0128] Step S16, FQA (Final Quality Assurance):

[0129] Perform sampling inspection on the PCB boards that have passed FQC to ensure that the product quality meets the requirements.

[0130] Step S17, Packaging:

[0131] Vacuum package the qualified PCB boards to prevent damage during transportation and storage.

[0132] The high-current-carrying circuit board provided in this embodiment realizes the combination of high current-carrying capacity and good heat dissipation performance through the mechanical fastening connection between the L-shaped copper bar and the PCB substrate 100. The design of the countersunk screw makes the surface of the circuit board flat, which is beneficial to the subsequent surface mounting process. The nickel-gold plating on the surface of the copper bar improves the corrosion resistance and reliability of the circuit board. The resin plug hole enhances the strength of the threaded connection. The entire solution takes into account the feasibility of the process and the reliability of the product while ensuring high performance, and is particularly suitable for high-power electrical equipment such as charging switches for new energy products.

[0133] Embodiment 2

[0134] As Figure 2 shown, this embodiment provides a high-current-carrying circuit board and its manufacturing method. The high-current-carrying circuit board includes a PCB substrate 100, a current-carrying member 200, and a mechanical fastener 300.

[0135] In this embodiment, the PCB substrate 100 is made of high-Tg (glass transition temperature) FR-4 material. The high-Tg FR-4 material has better heat resistance and can maintain stable mechanical and electrical properties at higher temperatures. The Tg value ≥ 170 °C, meeting the requirements of high-reliability applications.

[0136] The PCB substrate 100 is a multilayer board structure, such as a 6-layer board, including multiple layers such as L1, L2, L3, L4, L5, and L6. The multilayer board design can increase the wiring density, realize more complex functions, and improve signal integrity.

[0137] A U-shaped groove for embedding the current-carrying member 200 is provided on the L1 layer (top layer). The U-shaped groove is precision machined by a computer numerical control (CNC) milling machine to ensure dimensional accuracy and positional accuracy. The size and shape of the U-shaped groove match the current-carrying member 200.

[0138] In this embodiment, the first mechanical connection position 101 is a through hole provided on the PCB substrate 100. The through hole directly penetrates the PCB substrate 100 and is used for installing bolts.

[0139] The current-carrying member 200 is a U-shaped copper bar. The U-shaped design can increase the contact area with the PCB substrate 100, reduce the contact resistance, and improve the heat dissipation effect. At the same time, the U-shaped structure is also convenient for connecting with external connectors or wires.

[0140] In this embodiment, the size of the copper bar is customized according to the actual current demand.

[0141] The surface of the copper strip is subjected to electroless nickel immersion gold (ENIG) treatment. ENIG treatment involves first plating a layer of nickel (Ni) on the copper surface and then plating a layer of gold (Au). The nickel layer serves as a barrier layer to prevent the diffusion of copper atoms into the gold layer and affect the performance of the gold layer. At the same time, the nickel layer also improves the bonding strength between copper and gold. The gold layer has excellent corrosion resistance, oxidation resistance, and solderability, which can improve the reliability of the copper strip in harsh environments and enhance its electrical connection performance with other components. In this embodiment, the thickness of the nickel layer is 3 - 6 μm, and the thickness of the gold layer is 0.05 - 0.1 μm.

[0142] In this embodiment, the second mechanical connection position 102 is a through hole provided on the U-shaped copper strip. The diameter of the through hole matches that of the bolt.

[0143] In this embodiment, the mechanical fastener 300 is a stainless steel bolt and nut. Stainless steel has the characteristics of high strength, corrosion resistance, and oxidation resistance, and is suitable for high-reliability applications. The bolt passes through the through holes on the PCB substrate 100 and the U-shaped copper strip, and is tightened on the other side (usually the L6 layer) of the PCB substrate 100 by the nut. The specifications of the bolt and nut are selected according to actual requirements, for example, it can be M4 or M5.

[0144] The manufacturing process of the high-current-carrying circuit board in this embodiment is as follows:

[0145] Step S1, PCB substrate 100 processing:

[0146] Step S1.1, cutting and baking: Cut the PCB substrate 100 made of high-Tg FR-4 material into the required size and perform baking treatment to remove moisture and improve dimensional stability.

[0147] Step S1.2, inner layer pattern manufacturing: Through processes such as exposure, development, and etching, form the required circuit patterns on the inner layers (L2 - L5).

[0148] Step S1.3, U-shaped groove processing on L1 layer: Use a computer numerical control (CNC) milling machine to precisely machine a U-shaped groove on the L1 layer for embedding the U-shaped copper strip.

[0149] Step S1.4, drilling through holes: Drill through holes at predetermined positions on the L1 layer and the L6 layer for bolt fastening.

[0150] Step S2, prepreg (PP) treatment:

[0151] Step S2.1, punching / laser cutting: Punch or laser cut the prepreg (PP) to make its shape match that of the U-shaped copper strip. The role of PP is to fill the gaps between layers during the PCB lamination process and act as an adhesive and insulating layer.

[0152] Step S3, mirror steel plate treatment:

[0153] Step S3.1, Cutting and Windowing: Cut the mirror surface steel plate and open windows at the positions corresponding to the copper bars. The function of the mirror surface steel plate is to provide a flat surface during the PCB lamination process and prevent resin from overflowing.

[0154] Step S4, Laminating and Pressing:

[0155] Step S4.1, Laminating: Stack the prepreg materials (PP), each layer (L1 - L6) of the PCB substrate 100, and the mirror surface steel plate together in a specific order.

[0156] Step S4.2, Pressing: Put the laminated materials into a hot press and press them under high temperature and high pressure. During the pressing process, the PP melts and flows, filling the gaps between layers and firmly bonding the layers together.

[0157] Step S5, Copper Bar Processing and Fixing:

[0158] Step S5.1, Surface Treatment: Clean the surface of the U - shaped copper bar and perform electroless nickel immersion gold (ENIG) treatment.

[0159] Step S5.2, Drilling: Drill through - holes in the copper bar.

[0160] Step S5.3, Embedding and Fixing: Embed the U - shaped copper bar into the U - shaped groove. Use stainless steel bolts and nuts to fix the copper bar on the PCB substrate 100. The tightening torque of the bolts needs to be appropriately controlled to ensure firm connection while avoiding damage to the PCB substrate 100 or the copper bar.

[0161] Step S6, Subsequent Processing:

[0162] Step S6.1, Electroless Copper Plating + Electroplating: Deposit a thin layer of electroless copper on all the hole walls and the surface of the PCB board to metallize the non - conductor surfaces (such as hole walls) and provide a conductive basis for subsequent electroplating. Electroplating can use the positive - film or negative - film process. Through electroplating, connect the wires on the PCB substrate 100 with the copper bars to form electrical paths.

[0163] Step S6.2, Outer - layer Circuit Pattern Making: Use laser direct imaging (LDI) or other methods to make circuit patterns on the outer layer.

[0164] Step S6.3, Etching, AOI Inspection: Use etching solution to etch away the unnecessary copper layers, leaving the required circuit patterns. Use automatic optical inspection (AOI) equipment to check whether the circuit patterns are defective.

[0165] Step S6.4, Solder Mask and Character Printing: Apply a solder mask layer on the surface of the PCB board to protect the circuit pattern and prevent bridging during soldering. Print characters (such as product model, production date, etc.) on the surface of the PCB board.

[0166] Step S6.5, Surface Treatment: Perform surface treatment on the PCB board, such as full-board gold plating or selective electroless nickel immersion gold, to improve solderability and contact reliability.

[0167] Step S6.6, CNC Machining, Electrical Testing, FQC, FQA, Packaging: Cut the PCB board into the required shape, conduct electrical performance testing, perform final quality control and quality assurance, and finally carry out packaging.

[0168] The high-current-carrying circuit board of this embodiment adopts a combination of high-Tg FR-4 substrate, U-shaped copper bars, and stainless steel bolts and nuts, significantly improving the high-temperature resistance, mechanical strength, and connection reliability of the circuit board. The electroless nickel immersion gold (ENIG) surface treatment enhances the corrosion resistance of the copper bars and extends the service life. The via hole design simplifies the manufacturing process. These features make this solution particularly suitable for application scenarios with extremely high requirements for reliability and life, such as industrial control, aerospace, etc., and can work stably for a long time in harsh environments.

[0169] Embodiment 3

[0170] As Figure 3 shown, this embodiment provides a high-current-carrying circuit board and its manufacturing method. The high-current-carrying circuit board includes a PCB substrate 100, a current-carrying member 200, and a mechanical fastener 300.

[0171] In this embodiment, the PCB substrate 100 is made of standard FR-4 material (Tg≥170°C). FR-4 is a commonly used epoxy resin glass fiber cloth substrate, which has good mechanical strength, electrical insulation performance, and heat resistance, and has a low cost, suitable for mass production.

[0172] The PCB substrate 100 has a double-layer structure, including two layers L1 and L2.

[0173] On the L1 layer (top layer), there is a straight slot for embedding the current-carrying member 200. This slot can be processed by laser cutting or stamping processes. Laser cutting has the characteristics of high precision and high efficiency, and is suitable for small-batch and multi-variety production; the stamping process has higher production efficiency and is suitable for mass production of single varieties. The size of the slot is slightly larger than the single side of the aluminum bar (such as 0.2 mm), leaving an appropriate gap to facilitate the embedding of the aluminum bar.

[0174] In this embodiment, the first mechanical connection position 101 is a blind hole. A blind hole is a hole that is open only on one side and does not penetrate the entire PCB substrate 100. The design of the blind hole can simplify the manufacturing process and avoid additional processing on the other side of the PCB substrate 100.

[0175] The current-carrying member 200 is a straight aluminum bar. Aluminum has good electrical conductivity and low density, and its cost is lower than copper, making it an ideal low-cost current-carrying material. The straight bar design can simplify the processing and installation of the current-carrying member 200.

[0176] In this embodiment, the size of the aluminum strip is customized according to the actual current carrying requirement.

[0177] The surface of the aluminum strip is anodized. Anodizing is to form a dense oxide film on the surface of aluminum, which can improve the corrosion resistance, wear resistance and insulation of aluminum.

[0178] In this embodiment, the second mechanical connection position 102 is a through hole. The through hole is a hole that runs through the entire aluminum bar. The design of the through hole can facilitate the installation of self-tapping screws.

[0179] In this embodiment, the mechanical fastener 300 is a self-tapping screw. A self-tapping screw is a screw that can directly tap a thread on a material without pre-tapping, and is easy and quick to install. It cooperates with the blind hole and the through hole to fix the aluminum strip in the straight strip groove of the PCB substrate 100.

[0180] The manufacturing process of the high current-carrying circuit board in this embodiment is as follows:

[0181] Step S1, PCB substrate 100 processing:

[0182] Step S1.1, cutting and baking: cutting the PCB substrate 100 made of FR-4 material into required sizes, and baking the boards to remove moisture and improve dimensional stability.

[0183] Step S1.2, L1 layer groove processing: Use laser cutting or stamping technology to process grooves in the L1 layer for embedding straight aluminum bars.

[0184] Step S1.3, drilling blind holes: drilling blind holes at predetermined positions on the L1 layer (for fastening with self-tapping screws).

[0185] Step S2: Prepreg material (PP) processing:

[0186] Step S2.1, punching or laser cutting: punch or laser cut the PP (prepreg material) to make its shape match the aluminum strip. The role of PP is to fill the gap between layers during the PCB lamination process and play a role in bonding and insulation.

[0187] Step S3, Lamination and Pressing:

[0188] Step S3.1, Lamination: Stack the PP and the double - layer PCB (the mirror steel plate can be omitted to simplify the production process and reduce costs).

[0189] Step S3.2, Pressing: Put the stacked materials into a hot press and press them under high temperature and high pressure. During the pressing process, the PP melts and flows, filling the gaps between layers and firmly bonding each layer together.

[0190] Step S4, Aluminum Strip Treatment and Fixing:

[0191] Step S4.1, Surface Treatment: Clean and anodize the straight aluminum strip.

[0192] Step S4.2, Drilling Through - holes: Drill through - holes in the aluminum strip.

[0193] Step S4.3, Embedding and Fixing: Embed the aluminum strip into the straight - shaped groove and use self - tapping screws to fix the aluminum strip on the PCB substrate 100.

[0194] Step S5, Subsequent Processing:

[0195] Step S5.1, Copper Plating + Electroplating: Deposit a thin layer of chemical copper on all hole walls and the surface of the PCB board to metallize the non - conductor surface (such as hole walls) and provide a conductive basis for subsequent electroplating. Positive - film electroplating or negative - film VCP electroplating can be used.

[0196] Step S5.2, Outer - layer Circuit Pattern Making: Use conventional PCB pattern - making processes (such as exposure, development, etching, etc.) to make circuit patterns on the outer layer.

[0197] Step S5.3, Etching, AOI Inspection: Use etching solution to etch away the unnecessary copper layer, leaving the required circuit patterns. Use an automatic optical inspection device to check whether there are defects in the outer - layer circuit patterns.

[0198] Step S5.4, Solder Mask, Character Printing: Coat a solder mask layer on the surface of the PCB board (low - cost processes such as screen printing can be used) to protect the circuit patterns from the environment and prevent bridging during soldering. Print characters on the surface of the PCB board.

[0199] Step S5.5, Surface Treatment: Low - cost surface treatment processes such as spraying tin or OSP (organic solderability preservative film) can be used.

[0200] Step S5.6, CNC Milling, Electrical Testing, FQC, FQA, Packaging: Use a CNC milling machine or a punch press to cut the PCB board into the required shape. Use a tester to conduct electrical performance tests on the PCB board. Conduct final quality control and quality assurance, and finally package the qualified PCB boards.

[0201] The high-current-carrying circuit board of this embodiment adopts a combination of a standard FR-4 double-layer board, straight aluminum strips, and self-tapping screws. On the premise of ensuring basic performance, the production cost is greatly reduced. The aluminum strips replace the copper strips, and the anodic oxidation treatment simplifies the surface treatment process. The self-tapping screws and blind hole design improve the assembly efficiency. These improvements make this solution very suitable for mass production and can meet the application requirements that are sensitive to cost.

[0202] Unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present application. In all the examples shown and discussed herein, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that like reference numerals and letters denote like items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0203] In addition, it should be noted that the use of terms such as "first" and "second" is only for the convenience of distinction. Without otherwise stating, these terms have no special meaning and thus should not be construed as limiting the scope of protection of the present application.

[0204] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-current-carrying circuit board, characterized in that, Comprising: A PCB substrate, on which a first mechanical connection position is provided; At least one current-carrying member for carrying current, on which a second mechanical connection position is provided; A mechanical fastener, which fixes and connects the current-carrying member to the PCB substrate through the first mechanical connection position and the second mechanical connection position, and the current-carrying member is electrically connected to the PCB substrate.

2. The high-current-carrying circuit board according to claim 1, wherein: The first mechanical connection position and the second mechanical connection position are through holes or blind holes.

3. The high-current-carrying circuit board according to claim 1, wherein: The mechanical fastener is a screw; The first mechanical connection position is a first threaded hole provided on the PCB substrate; The second mechanical connection position is a second threaded hole provided on the current-carrying member; The screw is in threaded fit with the first mechanical connection position and the second mechanical connection position.

4. The high-current-carrying circuit board according to claim 3, wherein: The second threaded hole is a countersunk hole or a counterbore hole.

5. The high-current-carrying circuit board according to claim 3, wherein: The first threaded hole is a resin-filled hole with a threaded structure on the inner wall.

6. The high-current-carrying circuit board according to any one of claims 1-5, wherein: The current-carrying member is an L-shaped copper bar.

7. The high-current-carrying circuit board according to claim 1, wherein: There are multiple current-carrying members, and the multiple current-carrying members are arranged side by side.

8. The high-current-carrying circuit board according to claim 1, wherein: The surface of the current-carrying member is plated with a nickel layer and / or a gold layer.

9. A method for manufacturing a circuit board, characterized in that, A method for manufacturing the high-current-carrying circuit board according to any one of claims 1-8, comprising the following steps: Drilling holes at positions on the PCB substrate where the first mechanical connection position is to be formed; Performing resin plugging on the drilled positions on the PCB substrate; Performing mechanical processing on the cured resin holes to form the first mechanical connection position; Performing mechanical processing on the current-carrying member to form the second mechanical connection position; Using the mechanical fastener to fix and connect the current-carrying member to the PCB substrate through the first mechanical connection position and the second mechanical connection position.

10. The method for manufacturing a circuit board according to claim 9, wherein: The current-carrying member is an L-shaped copper bar; The mechanical fastener is a screw; The first mechanical connection position is a threaded hole; The second mechanical connection position is a countersunk threaded hole; The manufacturing method comprises the following steps: Performing surface treatment on the copper bar and performing mechanical processing at a predetermined position on the copper bar to form the countersunk threaded hole; Cutting and baking the PCB substrate; Manufacturing the inner layer pattern of the PCB substrate, and milling a square groove for embedding the copper bar on one layer of the substrate; Performing punching and laser cutting on the prepreg; Cutting the mirror steel plate and opening a window, and the window corresponds to the square groove; Stacking and laminating the treated prepreg, each layer of the PCB substrate, and the mirror steel plate; Drilling through holes at predetermined positions on the PCB board; A resin plug hole is made at the through hole to form a resin hole; The resin hole is tapped to form an internal thread to form the threaded hole; The copper bar is embedded in the square groove, and a screw is used to pass through the threaded hole and the countersunk threaded hole to fix the copper bar to the PCB substrate by threaded connection.

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