Automobile wiring board and method for manufacturing the same

Abstract

The application discloses a kind of automobile circuit board and its preparation method, preparation method includes: to insulating substrate is handled by inner layer circuit pattern transfer and vacuum etching, obtain inner layer circuit board;Several layers of the inner layer circuit board are alternately aligned by insulating adhesive layer and are laminated, by segmented preset temperature and preset pressure are laminated, obtain plate blank;To the plate blank is drilled and hole wall metallization processing, obtain conducting plate blank;To the conducting plate blank is handled by outer layer circuit pattern transfer and electroplating, obtain outer layer circuit plate blank;To the outer layer circuit plate blank is handled by several times printing and step curing, obtain finished product circuit board.The application is filled in the flat gap environment by vacuum etching and segmented lamination, combined with the differentiated control of temperature rising rate and pressure to segmented lamination, effectively improve the problem that resin is not uniform when thick copper plate is laminated, interlayer bonding force is insufficient.

Description

Technical Field

[0001] This application relates to the field of circuit board manufacturing technology, and in particular to an automotive circuit board and its preparation method. Background Technology

[0002] With the rapid development of the new energy vehicle industry, components such as on-board chargers, converters, and motor controllers are placing higher demands on the current carrying capacity and heat dissipation performance of printed circuit boards (PCBs). Thick copper circuit boards, with their excellent current carrying capacity and thermal conductivity, are widely used in high-power applications.

[0003] Competition in the new energy vehicle market is becoming increasingly fierce, and vehicle manufacturers are placing more stringent demands on the reliability and lifespan of core components. Lamination is a core process in the manufacturing of multilayer thick copper circuit boards, and its quality directly determines the interlayer bonding strength and long-term reliability of the product.

[0004] However, existing lamination processes still have shortcomings when processing thick copper plates. The significant height difference between thick copper lines and the substrate surface makes it difficult for the resin after the prepreg melts to fully fill the gaps between the lines within the limited lamination time, easily leading to localized missing adhesive or voids. The increased copper layer thickness causes a significant increase in interlayer stress during lamination, and the thermal expansion mismatch between different materials further exacerbates the deterioration of the interfacial bonding strength, resulting in insufficient interlayer bonding after lamination and quality problems such as delamination and voids, seriously affecting the service life of the product in automotive environments. Summary of the Invention

[0005] This application provides an automotive circuit board and its preparation method, which solves the technical problem of insufficient interlayer bonding in thick copper automotive circuit boards by synergistically combining vacuum etching, segmented lamination, hole metallization, outer layer circuit fabrication and solder mask printing.

[0006] The first aspect of this application provides a method for manufacturing an automotive circuit board, the method comprising:

[0007] The inner layer circuit pattern is transferred and vacuum etched onto the insulating substrate to obtain the inner layer circuit board. Several layers of the inner circuit board are alternately aligned and stacked through an insulating adhesive layer, and then pressed together at preset temperatures and pressures in segments to obtain a board blank; The slab blank is drilled and the hole walls are metallized to form a conductive path between the circuit boards of each layer, thus obtaining a conductive slab blank. The outer layer circuit pattern is transferred and electroplated on the conductive board blank to obtain the outer layer circuit board blank; The outer circuit board blank is subjected to several printing and step-by-step curing processes to cover the surface of the outer circuit board blank, thereby obtaining the finished circuit board.

[0008] Optionally, the step of alternately aligning and stacking several layers of the inner circuit board through an insulating adhesive layer, and pressing them together at preset temperatures and pressures in stages to obtain a board blank, includes: By performing alkaline cleaning and activation treatment on the surface of the inner circuit board, and then placing it in a browning solution for a browning reaction, an organometallic film is formed on the surface of the inner circuit board. Several layers of the inner circuit board, after browning treatment, are alternately aligned and stacked using an insulating adhesive layer to obtain a composite. The composite is placed in a pressing device for vacuuming, and then subjected to segmented temperature and pressure pressing.

[0009] Optionally, the segmented temperature and pressure pressing includes temperature control and pressure control; The temperature control is to raise the temperature to a first temperature at a first heating rate and then raise the temperature to a second temperature at a second heating rate, wherein the first heating rate is less than the second heating rate. The pressure control involves increasing the pressing pressure from the initial pressure to a preset pressure after the temperature reaches the first temperature, and then maintaining the temperature and pressure at the second temperature and the preset pressure.

[0010] Optionally, the drilling and hole wall metallization treatment of the slab blank to form conductive paths between the circuit board layers, resulting in a conductive slab blank, includes: After drilling holes in the slab to form through holes, the through holes are subjected to plasma degumming treatment to remove adhesive residue from the hole walls. The via is subjected to chemical copper plating treatment to deposit a conductive seed layer on the via wall; The conductive seed layer is electroplated by applying alternating positive and negative pulses, wherein the current density of the negative pulse is greater than the current density of the positive pulse.

[0011] Optionally, the step of transferring the outer layer circuit pattern and electroplating the conductive board blank to obtain the outer layer circuit board blank includes: A photosensitive film is attached to the surface of the conductive plate blank. After exposure and development, the non-circuit area in the conductive plate blank is covered by the photosensitive film, exposing the circuit area. Electroplating is performed on the circuit area to increase the copper layer thickness in the circuit area to a preset value; Remove the photosensitive film and then etch the outer copper layer after removing the photosensitive film to remove the copper layer outside the circuit area, thus obtaining the outer circuit board blank.

[0012] Optionally, the step of performing several printing and step-by-step curing processes on the outer circuit board blank to cover the surface of the outer circuit board blank and obtain the finished circuit board includes: Using solder resist as the printing medium, the outer circuit board blank is placed in a vacuum chamber, and the first solder resist printing is performed under vacuum conditions, so that the solder resist fills the surface of the exposed insulating substrate between adjacent circuits, and air bubbles in the solder resist are simultaneously discharged. Pre-curing treatment is performed on the solder resist material after the first printing. The pre-cured outer circuit board blank is placed in the vacuum chamber again, and a second solder resist printing is performed under vacuum conditions, so that the solder resist material is superimposed on the solder resist layer printed in the first printing to form a cover layer, and air bubbles in the solder resist material are simultaneously discharged. The solder resist material after the second printing is post-cured to form a solder resist layer, resulting in the finished circuit board.

[0013] Optionally, the pre-curing treatment is performed at a temperature of 70~90℃ for a time of 20~40 minutes. The post-curing treatment is performed at a temperature of 140~160℃ for a time of 40~80 minutes.

[0014] The second aspect of this application provides an automotive circuit board, which is prepared by any one of the preparation methods described in the first aspect to the first aspect.

[0015] Optionally, the automotive circuit board includes: several inner circuit board layers, an insulating adhesive layer, an outer circuit layer, a solder resist layer, and vias; The inner circuit boards of several layers each include an insulating substrate and an inner copper layer disposed on the surface of the insulating substrate; An insulating adhesive layer is disposed between two adjacent inner circuit boards to bond the inner circuit boards together as a whole; An outer circuit layer is disposed on the surface of the inner circuit board or the surface of the insulating adhesive layer; A solder resist layer covers the surface of the outer circuit layer and the surface of the insulating substrate exposed between adjacent outer circuit layers; The vias penetrate each of the inner circuit boards and the insulating adhesive layer. The walls of the vias are provided with a copper layer, so that the inner circuit boards of each layer are electrically interconnected.

[0016] Optionally, the copper layer thickness of the inner circuit board is 0.105~0.210mm; The thickness of the insulating adhesive layer is 0.05~0.30mm; The thickness of the outer circuit layer is 0.105~0.210mm; The thickness of the solder resist layer is 0.02~0.08mm.

[0017] As can be seen from the above technical solutions, this application has the following advantages: This application first uses vacuum etching to flatten the surface of the inner circuit board. When several inner circuit boards are alternately stacked with insulating adhesive layers and pressed together at preset temperatures and pressures in stages, this flat surface creates more uniform gap conditions for the flow and filling of the insulating adhesive layer. The insulating adhesive layer can thus penetrate more fully into the gaps between thick copper lines. The staged pressing process implements differentiated control of the heating rate—a lower heating rate is used when the temperature is in the melting range to ensure sufficient filling time; beyond this range, a higher heating rate is switched to balance production efficiency. Simultaneously, staged pressure increases suppress the expansion and contraction differences of the materials in each layer and release the internal stress of the board blank, ensuring that the pressed board blank meets the precision requirements of the drilling process in terms of dimensional stability and structural integrity. Based on this state, drilling and hole wall metallization, due to low board blank stress and high interlayer alignment, effectively reduces the risk of drill bit misalignment and hole wall roughness, allowing the metallized conductive path to continuously and uniformly penetrate each circuit board layer. The outer layer circuit pattern transfer and electroplating further constitute a complete electrical interconnection network between the inner and outer layers. Finally, the solder resist layer formed by multiple printing and step-by-step curing covers the surface of the outer circuit layer, encapsulating and protecting the electrical interconnection structure, thereby solving the problems of insufficient bonding force between lamination layers and easy delamination voids in the existing thick copper automotive circuit board manufacturing process. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic flowchart of an embodiment of the method for manufacturing an automotive circuit board provided in this application; Figure 2 A schematic flowchart of an embodiment of the method for manufacturing an automotive circuit board provided in this application, which involves laminating an inner circuit board. Figure 3 A schematic flowchart of an embodiment of the method for preparing an automotive circuit board provided in this application, which involves drilling holes in a board blank and metallizing the hole walls. Figure 4 This is a schematic flowchart of an embodiment of the method for preparing an automotive circuit board provided in this application, which involves transferring the outer layer circuit pattern and electroplating the conductive board blank. Figure 5 A schematic flowchart of an embodiment of the method for preparing an automotive circuit board provided in this application, which involves printing and curing an outer circuit board blank; Figure 6This is a schematic diagram of the layer structure of an embodiment of the automotive circuit board provided in this application. Detailed Implementation

[0020] It should be noted that the automotive circuit board provided in this application can be applied to core components of new energy vehicles, such as on-board chargers, DC / DC converters, motor controllers, and high-voltage boards for battery management systems. These components all need to withstand high current transmission and maintain reliability under strong vibration and long-term operating conditions. Taking an on-board charger as an example, a 6oz thick copper circuit board can withstand operating currents of tens to hundreds of amperes. The high thermal conductivity of the thick copper layer helps to quickly dissipate heat generated by power devices, reducing module temperature rise. Vacuum etching ensures the precision and consistency of the thick copper circuitry, reducing localized overheating caused by circuit defects. Segmented temperature and pressure bonding ensures the interlayer insulation reliability of multilayer boards under high-voltage conditions. The high Tg heat-resistant substrate enables the circuit board to maintain dimensional stability and reliable interlayer bonding over a wide temperature range. Furthermore, the automotive circuit board provided in this application can also be applied to high-power industrial equipment such as photovoltaic inverters and energy storage converters, as well as high-reliability electronic equipment in rail transit, medical high-power equipment, and aviation drones.

[0021] This application first provides an embodiment of a method for manufacturing an automotive circuit board; please refer to [link to embodiment]. Figure 1 , Figure 1 A schematic flowchart illustrating an embodiment of the method for manufacturing an automotive circuit board provided in this application, the embodiment including: S101. The inner layer circuit pattern is transferred and vacuum etched on the insulating substrate to obtain the inner layer circuit board. An insulating substrate is provided, which can be a high-Tg heat-resistant copper-clad laminate, such as a hydrocarbon substrate with a Tg ≥ 150℃. The inner layer circuit pattern transfer specifically includes three sub-steps: film application, exposure, and development. A photosensitive film is applied to the copper foil surface of the insulating substrate. Then, the photosensitive film is exposed using film or direct laser imaging to transfer the inner layer circuit pattern onto the photosensitive film. Finally, a developing solution is used to remove the unexposed areas of the photosensitive film, exposing the copper foil surface to be etched.

[0022] After the pattern transfer is completed, the board is placed in a vacuum etching apparatus for etching. The vacuum etching apparatus includes a sealed etching chamber and a vacuum pump connected to the chamber. During etching, the etching chamber is first evacuated to a preset negative pressure value, and then an etching solution is sprayed into the chamber. The etching solution can be acidic copper chloride etching solution or alkaline ammonia etching solution. Establishing a vacuum environment helps to promptly remove the heat and reaction byproducts generated by the etching reaction, reducing localized reaction stagnation caused by poor exchange in the narrow gaps between thick copper lines. By controlling etching parameters, including etching temperature, spray pressure, etching solution concentration, and etching time, the exposed copper foil can be etched away, preserving the circuit pattern covered by the photosensitive film. After etching, the remaining photosensitive film is removed to obtain the inner layer circuit board.

[0023] S102. Several inner circuit boards are alternately aligned and stacked through an insulating adhesive layer, and then pressed together by pre-set temperature and pre-set pressure in segments to obtain a board blank. The resulting inner layer circuit board undergoes a browning treatment. This browning treatment forms a micro-roughened organometallic film on the copper surface of the inner layer circuit board, enhancing the adhesion between the copper surface and the subsequent insulating adhesive layer. The specific steps include: cleaning the copper surface with an alkaline cleaner to remove oil and oxides; activating the cleaned copper surface; and then placing the activated inner layer circuit board in a browning solution for a chemical reaction, causing the copper surface to be micro-etched while simultaneously forming a brown organometallic film.

[0024] After browning, several inner circuit board layers and insulating adhesive layers are alternately stacked according to a preset stacking sequence. The insulating adhesive layer can be a prepreg, such as an epoxy resin fiberglass cloth prepreg. During stacking, an insulating adhesive layer is placed between adjacent inner circuit board layers; the outermost layer may or may not have an insulating adhesive layer, depending on requirements.

[0025] The stacked multi-layered structure is fed into a pressing device, which can be a vacuum press. Before pressing, the pressing chamber is evacuated to remove interlayer air and prevent air bubbles from forming after pressing. After evacuation, the pressing operation is performed according to preset segmented temperature and pressure curves. The preset segmented temperature and pressure mean that during the pressing process, the temperature and pressure are not constant, but gradually change according to preset time-temperature and time-pressure curves.

[0026] In an optional implementation, a low initial pressure is applied and the temperature is raised during the initial stage of pressing. As the temperature rises, the resin in the prepreg gradually melts and begins to flow. At this point, the pressure is increased to the main pressure, allowing the resin to fill the gaps between layers and the voids between thick copper lines under pressure. After reaching the target pressing temperature, the temperature and pressure are maintained for a period of time to allow the resin to fully crosslink and cure. Finally, the pressure is maintained while cooling to room temperature, and the pressing pressure is released to obtain a multilayer board blank.

[0027] S103. Drill holes and metallize the hole walls of the slab blank to form a conductive path between the circuit boards of each layer, and obtain a conductive slab blank. The laminated slab is drilled, using CNC mechanical drilling with a carbide drill bit to create through-holes penetrating each circuit board layer at predetermined locations on the slab. After drilling, the through-holes undergo adhesive removal. The high temperatures generated during drilling cause the resin in the insulating adhesive layer to melt at the hole walls, forming adhesive residue. If this residue is not removed, it will affect the adhesion of the subsequent metallization layer on the hole walls. Adhesive removal can be performed using plasma removal. The slab is placed in a vacuum plasma treatment device, and a mixture of oxygen and carbon tetrafluoride is introduced. Under the action of a high-frequency electric field, the gas is ionized to form plasma. The active particles in the plasma oxidize and decompose the adhesive residue on the hole walls into gaseous products, which are then removed. Another benefit of plasma removal is that it microscopically roughens the surface of the hole walls, which is beneficial for the adhesion of the chemical copper plating layer.

[0028] After the adhesive removal is completed, the vias are subjected to chemical copper plating treatment. Chemical copper plating involves immersing the board blank in a copper plating solution containing copper ions and a reducing agent. An oxidation-reduction reaction occurs on the catalytic surface of the hole wall, depositing a thin and uniform conductive copper layer as a seed layer for subsequent electroplating.

[0029] Electroplating is used to thicken the vias with a conductive seed layer deposited on them. Electroplating thickening involves placing the slab blank as the cathode in an electroplating bath, where an electric field causes copper ions to be further deposited on the conductive seed layer on the via wall, increasing the thickness of the copper layer on the via wall, thereby obtaining a conductive slab blank.

[0030] S104. The outer layer circuit pattern is transferred and electroplated on the conductive board blank to obtain the outer layer circuit board blank. Pattern transfer is performed on the outer copper foil surface of the obtained conductive board blank. The specific operation of outer layer pattern transfer is similar to that of inner layer pattern transfer, including film application, exposure and development steps. The difference is that the film or LDI data used for outer layer pattern transfer corresponds to the outer layer circuit pattern.

[0031] After development, electroplating is performed on the exposed circuit areas of the outer layer. A thicker copper layer is further electroplated onto the copper surface of the exposed circuit areas to achieve the preset copper thickness for the outer layer circuits. During electroplating, current is applied simultaneously to the hole walls and the outer circuit areas, thus causing the copper layer to thicken synchronously in all areas. After electroplating, the remaining photosensitive film on the surface of the outer copper foil is removed, and the exposed outer copper layer is etched. Etching can be performed using alkaline or acidic etching solutions to remove the outer copper foil from non-circuit areas, leaving the outer circuit pattern protected by the electroplated layer. At this point, the inner and outer circuits are electrically connected through the metallization layer on the hole walls of the vias.

[0032] S105. Perform several printing and step-by-step curing processes on the outer layer circuit board blank to cover the surface of the outer layer circuit board blank, and obtain the finished circuit board.

[0033] Solder resist material is provided, which can be liquid photosensitive solder resist ink. The outer circuit board blank is placed on the worktable of the printing equipment, and the solder resist ink is applied to the board surface using screen printing. Due to the significant step difference between the thick copper lines and the surface of the insulating substrate, multiple printing steps can be used to achieve good coverage. Specifically, a first printing is performed to cover the surface of the outer circuit and the area between adjacent lines with solder resist ink. After the first printing, the board blank is pre-cured to reduce the ink's fluidity but not completely cure it. Then, a second printing is performed to replenish the ink and fill any gaps in coverage that may have been missed in the first printing.

[0034] After each printing process, a curing process is required. Curing can be performed using a segmented baking method, for example, first baking at a lower temperature to evaporate the solvent in the ink, and then baking at a higher temperature to fully cross-link and cure the resin in the ink. The cured solder mask layer provides insulation protection for the outer circuitry, preventing oxidation, short circuits, or moisture-induced failure during subsequent use. After solder mask fabrication, surface treatments such as immersion tin, gold plating, or OSP treatment can be performed as needed, followed by shaping and milling, electrical performance testing, and visual inspection to obtain the final finished automotive circuit board.

[0035] In this embodiment, vacuum etching is used to flatten the surface of the inner circuit board. When several inner circuit boards are alternately stacked with insulating adhesive layers and pressed together at preset temperatures and pressures in stages, this flat surface creates more uniform gap conditions for the flow and filling of the insulating adhesive layer. The insulating adhesive layer can thus penetrate more fully into the gaps between thick copper lines. The staged pressing process implements differentiated control of the heating rate—a lower heating rate is used when the temperature is in the melting range to ensure sufficient filling time; beyond this range, a higher heating rate is switched to balance production efficiency. Simultaneously, staged pressure increases suppress the expansion and contraction differences of the materials in each layer and release the internal stress of the board blank, ensuring that the pressed board blank meets the precision requirements of the drilling process in terms of dimensional stability and structural integrity. Based on this state, drilling and hole wall metallization, due to low board blank stress and high interlayer alignment, effectively reduces the risk of drill bit misalignment and hole wall roughness, allowing the metallized conductive path to continuously and uniformly penetrate each circuit board layer. The outer layer circuit pattern transfer and electroplating further constitute a complete electrical interconnection network between the inner and outer layers. Finally, the solder resist layer formed by multiple printing and step-by-step curing covers the surface of the outer circuit layer, encapsulating and protecting the electrical interconnection structure, thereby solving the problems of insufficient bonding force between lamination layers and easy delamination voids in the existing thick copper automotive circuit board manufacturing process.

[0036] The following describes the lamination process for the inner circuit board. Please refer to [link / reference]. Figure 2 , Figure 2 This is a schematic flowchart illustrating an embodiment of the method for manufacturing an automotive circuit board according to this application, which involves laminating the inner circuit board. The embodiment includes: S201. By performing alkaline cleaning and activation treatment on the surface of the inner circuit board, and then placing it in a browning solution for browning reaction, an organometallic film is formed on the surface of the inner circuit board. The resulting inner layer circuit board undergoes a browning treatment. The purpose of browning is to chemically roughen the surface of the copper traces on the inner layer circuit board, thereby enhancing the adhesion between the copper surface and the insulating bonding layer. Specifically, the inner layer circuit board is sequentially fed into various treatment tanks of the browning treatment line for alkaline cleaning. The inner layer circuit board is immersed in an alkaline cleaning agent to remove contaminants such as oil, fingerprints, and oxides from the copper trace surface. The cleaning temperature is typically controlled at 40℃~60℃, and the time is 1 minute~5 minutes. After cleaning, it is rinsed with deionized water to remove residual cleaning agent. Next, an activation treatment is performed. The cleaned inner layer circuit board is immersed in an activation solution, which is typically an acidic solution containing organic additives and trace amounts of corrosion inhibitors. Its function is to clean the copper surface and bring it to a uniform chemical activation state, providing a uniform reaction interface for the subsequent browning reaction. The activation temperature is typically controlled at 25℃~40℃, and the time is 1 minute~3 minutes. After activation, it is also rinsed with water.

[0037] After activation, the inner layer circuit board is placed in a browning solution for a browning reaction. The browning solution typically contains sulfuric acid, hydrogen peroxide, and organic additives. During the browning reaction, hydrogen peroxide oxidizes the copper surface to cuprous oxide, sulfuric acid dissolves some of the copper oxide and releases copper ions, and the organic additives combine with the copper ions to form a brown to dark brown organometallic film on the copper surface in situ. This organometallic film has a micro-rough structure with an uneven surface, which can form a mechanical interlocking anchoring effect with the insulating adhesive resin during lamination. Simultaneously, the polar groups in the organometallic film can chemically bond with the resin, thereby synergistically enhancing the adhesion between the copper surface and the insulating adhesive layer. The browning reaction temperature is typically controlled between 30℃ and 50℃, and the time is 1 to 3 minutes. During the reaction, the uniformity of the browning solution composition is maintained through bath circulation and filtration. After the reaction is complete, the board is washed with water and dried to obtain the inner layer circuit board with the organometallic film formed on its surface.

[0038] S202. Several inner circuit boards after browning treatment are alternately aligned and stacked using an insulating adhesive layer to obtain a composite. Multiple inner circuit boards that have undergone browning treatment are alternately stacked with insulating adhesive layers according to a preset stacking sequence. The insulating adhesive layer can be a semi-cured sheet, i.e., fiberglass cloth impregnated with resin, which is semi-solid at room temperature but melts and flows under high temperature and pressure, eventually cross-linking and curing. During stacking, following the preset stacking sequence, one layer of insulating adhesive layer, one layer of inner circuit board, one layer of insulating adhesive layer, one layer of inner circuit board, and so on, from bottom to top, forming a multi-layer alternating stacked structure. An insulating adhesive layer is placed between two adjacent inner circuit boards to bond them together during subsequent lamination. After stacking, each layer is positioned using alignment fixtures to ensure the relative positional accuracy between the circuit patterns of each layer. The alignment fixture can use a pin positioning method: positioning holes are pre-machined in the non-circuit areas of the inner circuit boards and insulating adhesive layers, and each layer is fitted onto the positioning pins through the positioning holes to achieve alignment. After stacking and alignment, a composite body is obtained.

[0039] S203. Place the composite material in a pressing device for vacuuming, and then perform segmented temperature and pressure pressing.

[0040] The resulting composite is fed into the pressing equipment, placed on the press's worktable, and the cavity is closed. The vacuum pump is then activated to evacuate the cavity to a preset vacuum level, such as -0.06 MPa to -0.095 MPa. The purpose of evacuation is to remove air trapped between the layers of the composite, preventing the formation of interlayer bubbles or voids due to residual air during pressing. After evacuation, a segmented temperature and pressure pressing program is executed, which includes both temperature and pressure control.

[0041] In terms of temperature control, the temperature is raised to a first temperature at a first heating rate, and then raised to a second temperature at a second heating rate, wherein the first heating rate is less than the second heating rate. The first temperature is set according to the melting temperature range of the resin in the insulating adhesive layer, and the second temperature is set to a temperature higher than the first temperature but sufficient to allow the resin to cross-link and cure. This segmented heating method allows the composite to pass through the resin's melting temperature range at a slower rate during the heating process to the first temperature, ensuring that the resin, in a low viscosity state, has sufficient time to flow and fill the gaps between layers and between thick copper lines, reducing the risk of cross-linking and curing before the resin is fully filled due to excessively rapid heating. After reaching the first temperature, the temperature is then raised to the second temperature at a faster rate, allowing the resin to quickly complete cross-linking and curing at a higher temperature.

[0042] Regarding pressure control, the pressing pressure is increased from the initial pressure to the preset pressure simultaneously with or after the first temperature is reached. Pressure control is coordinated with temperature control: a lower initial pressure is used in the initial stage of pressing to facilitate the further expulsion of residual air between layers before the resin flows extensively; when the temperature reaches or approaches the first temperature, the resin has fully melted and possesses good fluidity, at which point the pressure is increased to the preset pressure, allowing the resin to fully fill the gaps between layers under higher pressure; heat and pressure are maintained at the second temperature and the preset pressure, allowing the resin to complete cross-linking and curing under pressure. After the heat and pressure maintenance stage, the temperature is lowered to room temperature while maintaining the preset pressure, and the pressure is released to obtain the pressed slab.

[0043] The specific operation of segmented temperature and pressure pressing can be carried out according to the following steps: heat the vacuum-sealed composite body from room temperature to a first temperature at a first heating rate; during the heating process or after reaching the first temperature, increase the pressing pressure from the initial pressure to the preset pressure; then heat the temperature from the first temperature to the second temperature at a second heating rate; maintain the temperature and pressure at the second temperature and the preset pressure; finally, reduce the temperature to room temperature while maintaining the preset pressure.

[0044] For example, the first temperature can be 90℃~130℃, and the second temperature can be 155℃~195℃. The first heating rate can be 0.8℃ / min~2.0℃ / min, and the second heating rate can be 4℃ / min~8℃ / min. The first temperature of 90℃~130℃ covers the softening initiation temperature and melt flow range of conventional prepreg resin. Using a heating rate of 0.8℃ / min~2.0℃ / min through this range allows the resin to obtain sufficient flow and filling time at a low viscosity, fully penetrating into the gaps between thick copper lines and the interlayer interface area. After the resin is fully filled, the temperature is increased to 155℃~195℃ at a rate of 4℃ / min~8℃ / min, allowing the resin to quickly complete cross-linking and curing at a higher temperature. It should be noted that the specific values ​​of the first and second temperatures can be adaptively adjusted according to the type and characteristics of the resin system used in the insulating adhesive layer. Based on the above temperature control, the initial pressure can be 50PSI~150PSI, and the preset pressure can be 280PSI~400PSI. In the initial stage of lamination, a relatively low initial pressure of 50 PSI to 150 PSI is used. This facilitates the further expulsion of residual air between layers before the resin has flowed significantly, while also reducing the risk of resin being squeezed out before it has fully flowed due to excessively high initial pressure. Once the temperature reaches or approaches the first temperature, the resin has fully melted and possesses good fluidity. At this point, the pressure is increased to 280 PSI to 400 PSI, allowing the resin to fully fill the gaps between layers and the voids between thick copper lines under higher pressure. At the second temperature and preset pressure, the holding time can be 40 to 90 minutes to ensure that the resin fully completes cross-linking and curing under pressure.

[0045] In this embodiment, alkaline cleaning and activation treatment bring the copper surface to a uniform activation state, and the browning reaction generates a micro-roughened organometallic film in situ on the copper surface. The polar groups in this organometallic film chemically bond with the insulating adhesive layer resin, effectively enhancing the adhesion between the copper surface and the insulating adhesive layer. During lamination, vacuuming removes interlayer air, preventing the formation of bubbles and voids. In segmented temperature-pressure lamination, the first heating rate is lower than the second heating rate, allowing the resin sufficient flow and filling time within the melting temperature range. This reduces the risk of the resin cross-linking and curing before complete filling due to excessively rapid heating. Combined with segmented pressure increases, the resin fully fills the gaps between layers under higher pressure. Finally, the pressure is maintained while cooling releases stress, effectively improving the interlayer adhesion of the multilayer board.

[0046] The slab blank undergoes drilling and hole wall metallization to create conductive paths between the circuit board layers, resulting in a conductive slab blank. The drilling and hole wall metallization processes are described in detail below. Please refer to [link to relevant documentation]. Figure 3 , Figure 3This is a schematic flowchart illustrating an embodiment of the method for manufacturing an automotive circuit board provided in this application, which involves drilling holes and metallizing the hole walls of the board blank. The embodiment includes: S301. After drilling holes in the slab to form through holes, the through holes are subjected to plasma degumming treatment to remove adhesive residue from the hole walls. Drilling is performed on the laminated slab. CNC drilling can be used, employing carbide drill bits to create through-holes penetrating each layer of the circuit board at predetermined locations on the slab. For thick copper plates, the drill bit wears relatively quickly due to the thicker copper layer, and the high temperatures generated during drilling can easily cause the resin in the insulating adhesive layer to melt and adhere to the hole wall, forming adhesive residue. Therefore, the drilling speed and feed rate must be appropriately controlled during drilling, for example, setting the drill bit speed to 12,000~15,000 rpm and the feed rate to 0.5~1 mm / s. After drilling, high-pressure water washing can be used to remove residual drill chips and dust from the holes.

[0047] After drilling, the through holes undergo plasma degumming. The principle of plasma degumming is to place the slab in the cavity of a vacuum plasma treatment device, introduce process gas, and ionize the gas under the action of a high-frequency, high-voltage electric field to form a plasma atmosphere containing free radicals, ions, and electrons. The active particles in the plasma react chemically with the resin residue on the hole wall, oxidizing and decomposing it into gaseous products such as CO2 and H2O. These gaseous products are then extracted from the cavity by a vacuum pump.

[0048] In addition to removing adhesive residue, plasma desmearing also has the effect of microscopic roughening of the via walls. The high-energy particles in the plasma physically bombard and chemically etch the via wall surface, creating micron-sized irregular bumps and ridges, increasing the surface area and roughness of the via walls, which is beneficial for the subsequent adhesion of the chemical copper plating layer. For high aspect ratio vias, plasma desmearing can effectively achieve uniform cleaning of the entire via wall area, reducing the problem of insufficient cleaning caused by difficulties in chemical exchange within the via.

[0049] S302. Perform chemical copper plating on the via to deposit a conductive seed layer on the via wall. The principle of chemical copper plating is to reduce copper ions to metallic copper using a reducing agent in the plating solution without an external power source, and then deposit the copper onto the surface of the via walls. The vias are pre-cleaned and micro-etched to remove residual contaminants and further clean the via walls. Then, a pre-immersion and activation treatment is performed, immersing the slab in an activation solution containing palladium ions or colloidal palladium, causing a layer of catalytically active palladium particles to adsorb onto the via wall surface. The uniformity and density of palladium adsorption, acting as a catalyst in the chemical copper plating reaction, determine the continuity and compactness of the copper layer. After activation, a desizing treatment is performed to remove the tin ion protective layer surrounding the colloidal palladium particles, exposing the palladium and restoring its catalytic activity. Finally, the slab is immersed in a chemical copper plating solution containing copper ions, a reducing agent, and a complexing agent. Under the catalytic action of the palladium particles, the reducing agent reduces copper ions to metallic copper, which is then deposited on the via wall surface. As the reaction proceeds, the newly deposited copper itself also possesses catalytic activity, thus the reaction continues on the already deposited copper layer, causing the copper layer to continuously thicken.

[0050] After chemical copper plating is completed, a thin and uniform conductive copper layer, known as the conductive seed layer, is formed on the hole wall. The thickness of this conductive seed layer is usually controlled between 0.5 μm and 1.5 μm. Its function is to make the originally insulating hole wall conductive, providing a conductive path for the electroplating thickening process.

[0051] S303. Apply alternating positive and negative pulses to the conductive seed layer for electroplating, wherein the current density of the negative pulse is greater than the current density of the positive pulse.

[0052] Electroplating is used to thicken vias with conductive seed layers. Electroplating thickening involves placing a slab as the cathode in an electroplating bath, where an external electric field causes copper ions to further deposit on the conductive seed layer on the via walls. Pulse electroplating is used for thickening; unlike traditional DC electroplating, pulse electroplating achieves copper layer deposition through periodically switching on and off or reversing current. The current waveform in pulse electroplating consists of alternating positive and negative pulses. During a positive pulse, the current is on, and copper ions migrate towards the cathode under the drive of the electric field and deposit on the conductive seed layer on the via walls. During the positive pulse's off period, copper ions at the bottom of the via diffuse from the solution to replenish the deposits, mitigating the concentration gradient of metal ions within the via. During a negative pulse, the current direction is reversed, selectively stripping the copper layer in the via opening region.

[0053] The reverse pulse current density is set higher than the forward pulse current density. During electroplating, due to the geometric limitations of the via, the current density in the via opening region is usually higher than that in the via interior region. This results in a much higher copper ion deposition rate in the via opening region compared to the interior region, easily leading to an excessively thick copper layer at the via opening and an insufficient copper layer inside the via. This problem is particularly pronounced for thick copper plates due to their greater thickness and higher thickness-to-diameter ratio. Setting the reverse pulse current density higher than the forward pulse current density makes the stripping effect of the reverse pulse on the copper layer at the via opening stronger than the deposition effect of the forward pulse, thus effectively inhibiting the excessive growth of the copper layer at the via opening. In the via interior region, due to the weaker current density distribution, the stripping effect of the reverse pulse is relatively limited, and the deposition effect of the forward pulse is preserved. For example, the current density of the forward pulse is 1.5~3.2 ASF, and the current density of the reverse pulse is 18~35 ASF, with the reverse pulse current density being 6~15 times that of the forward pulse; the pulse width of the forward pulse is 10~25 ms, and the pulse width of the reverse pulse is 0.5~2.5 ms, with a pulse width ratio of (5~20):1; the total electroplating time is 70~120 minutes. After electroplating, the total thickness of the copper layer on the hole wall reaches over 20 μm. Through this asymmetric design, the growth rate of the copper layer at the hole opening and inside the hole tends to be balanced, and the thickness distribution of the copper layer on the hole wall is more uniform.

[0054] In this embodiment, plasma desmearing oxidizes and decomposes the adhesive residue on the hole wall into gaseous products. Simultaneously, high-energy particles in the plasma physically bombard and chemically etch the hole wall, resulting in microscopic roughening of the hole wall surface and increasing the adhesion of the subsequent chemical copper plating layer. During pulse electroplating, copper ions are deposited on the hole wall during the forward pulse, and during the turn-off period, copper ions diffuse from the solution to replenish the bottom of the hole, alleviating the ion concentration gradient within the hole. During the reverse pulse, the copper layer at the hole opening is selectively stripped. Because the reverse pulse current density is greater than the forward pulse, the reverse stripping effect is stronger than the forward deposition effect, effectively suppressing excessive growth of the copper layer at the hole opening. Meanwhile, due to the weaker current density in the hole's interior, forward deposition is preserved, balancing the copper layer growth rate at the hole opening and inside the hole. This results in a more uniform copper layer thickness distribution on the hole wall, ensuring the stability of the conductive path of the via.

[0055] The following provides a detailed explanation of the outer layer circuit pattern transfer and electroplating process for the conductive board blank. Please refer to [link / reference]. Figure 4 , Figure 4 This is a schematic flowchart illustrating an embodiment of the method for preparing an automotive circuit board according to this application, which involves transferring outer layer circuit patterns and electroplating the conductive board blank. The embodiment includes: S401. A photosensitive film is attached to the surface of the conductive plate blank. After exposure and development, the non-circuit area in the conductive plate blank is covered by the photosensitive film, exposing the circuit area. The outer copper foil surface of the conductive board is ground and chemically cleaned to remove oxides, oil and other contaminants. At the same time, physical brushing is used to create a certain micro-roughness on the copper foil surface to enhance the adhesion between the photosensitive film and the copper foil surface.

[0056] After grinding and chemical cleaning, a photosensitive film is attached to the outer copper foil surface of the conductive board. The photosensitive film can be a dry film. During attachment, a hot roller is used to apply the dry film to the board surface, allowing the resin in the dry film to adhere evenly to the copper foil surface and bond tightly with the copper under heat and pressure. It is crucial to ensure that there are no air bubbles between the dry film and the copper foil surface during attachment; otherwise, it will affect pattern transfer during subsequent exposure and development.

[0057] Next, the designed outer circuit pattern film is placed on the photosensitive film, and a direct laser imaging method is used to selectively irradiate the photosensitive film with ultraviolet light. During the exposure process, the areas of the photosensitive film exposed to ultraviolet light undergo photopolymerization, and the molecular chains cross-link to form a polymer structure that is insoluble in the developing solution; the un-irradiated areas retain their original solubility.

[0058] The exposed conductive board blank is immersed in a developing solution or applied by spraying. The developing solution is usually a weakly alkaline aqueous solution. The developing solution dissolves and removes the photosensitive film in the unexposed areas, exposing the copper foil surface underneath. The photosensitive film in the exposed areas remains on the copper foil surface due to photopolymerization, forming an anti-plating mask. After development, the non-circuit areas are covered and protected by the photosensitive film, while the copper foil surface in the circuit areas is exposed.

[0059] S402. Electroplating is performed on the circuit area to increase the copper layer thickness in the circuit area to a preset value. The exposed circuit area of ​​the conductive blank after development undergoes patterned electroplating. Patterned electroplating involves placing the blank as the cathode in an electroplating bath, where an external electric field causes copper ions to be further deposited on the copper surface of the exposed circuit area, thereby increasing the copper layer thickness in the circuit area to a predetermined thickness. Before electroplating, the conductive blank undergoes pickling to remove oxides and passivation layers from the copper foil surface, ensuring adhesion between the electroplated layer and the base copper layer. The blank is then immersed in the electroplating bath, which typically uses a copper sulfate-sulfuric acid system containing copper ions, sulfuric acid, chloride ions, and organic additives. Under the influence of a direct current electric field, copper ions gain electrons at the cathode surface and are reduced to metallic copper. As electroplating progresses, the copper layer in the circuit area continuously thickens.

[0060] During the electroplating process, the copper layer deposition thickness is controlled by adjusting the current density and plating time. The plating duration is determined based on the target copper thickness. After plating, the copper layer thickness in the circuit area increases to the preset value. It should be noted that during the electroplating process, the copper layer on the hole wall thickens synchronously with the copper layer in the outer circuit area. Therefore, the copper layer thickness on the hole wall of the via also increases accordingly, ensuring the conductivity stability of the via.

[0061] S403. Remove the photosensitive film and etch the outer copper layer after removing the photosensitive film to remove the copper layer outside the circuit area, and obtain the outer circuit board blank.

[0062] To remove the remaining photosensitive film from the slab surface after electroplating, an alkaline solution, such as sodium hydroxide solution, is typically used. The slab is immersed in the sodium hydroxide solution or the solution is applied by spraying. Under alkaline conditions, the resin molecular chains in the photosensitive film hydrolyze or dissolve and peel off from the copper foil surface. The copper foil surface in non-circuit areas is exposed, while the copper layer in the circuit areas, thickened by electroplating, is retained.

[0063] Next, the slab is etched. Etching removes the copper foil layer in non-circuit areas, leaving only the copper circuit pattern in the circuit areas. The choice of etching solution depends on the thickness of the outer copper foil. During etching, the copper foil in non-circuit areas is dissolved and removed by the etching solution, exposing the surface of the underlying insulating substrate; the circuit areas are preserved due to the thicker copper layer. After etching, the slab is thoroughly washed and dried to remove residual etching solution and reaction products. At this point, the outer circuit pattern is formed, and the required circuit pattern is formed on the outer copper foil of the conductive slab. The inner and outer circuits are electrically interconnected through vias, thus obtaining the outer circuit slab.

[0064] In this embodiment, by applying a film, exposing, and developing, the non-circuit areas are covered by the photosensitive film, while the circuit areas are exposed, achieving precise transfer of the outer circuit pattern. Pattern electroplating increases the copper layer thickness in the circuit areas to a preset value, while the copper layer on the hole walls and the outer circuit copper layer thickens synchronously, ensuring the conductivity stability of the vias. After removing the photosensitive film, the copper foil in the non-circuit areas is removed by etching. The circuit areas are preserved due to the thicker copper layer, forming the outer circuit pattern. The inner and outer circuits are electrically interconnected through vias, forming a complete electrical conduction network.

[0065] The printing and curing process for the outer layer circuit board blank is described in detail below. Please refer to [link / reference]. Figure 5 , Figure 5 A schematic flowchart illustrating an embodiment of the method for preparing an automotive circuit board according to this application, comprising the printing and curing process of the outer circuit board blank, wherein the embodiment includes: S501. Using solder resist material as the printing medium, the outer circuit board blank is placed in a vacuum chamber, and the first solder resist printing is performed under vacuum conditions, so that the solder resist material fills the surface of the exposed insulating substrate between adjacent circuits, and the air bubbles in the solder resist material are simultaneously discharged. The outer circuit board blank is placed inside a vacuum chamber, a sealed structure housing a screen printing device, including a screen, squeegee, and corresponding transmission mechanism, enabling printing operations to be completed in a vacuum environment. A vacuum pump is connected to the vacuum chamber, reducing the internal pressure to a preset vacuum level. The vacuum pump is activated to evacuate the chamber, maintaining the preset vacuum level. Under these vacuum conditions, solder resist is used as the printing medium, and the screen printing device inside the chamber performs the first solder resist printing on the board surface. During printing, the squeegee applies pressure to the screen, forcing the solder resist through the mesh onto the board surface. Because the printing operation is performed in a vacuum environment, the tiny air bubbles trapped within the solder resist expand, rise, and burst simultaneously under the vacuum pressure, eliminating the need for post-printing degassing. Driven by both squeegee pressure and vacuum pressure, a portion of the solder resist flows into the exposed insulating substrate surface area between adjacent circuits, filling the stepped area between the thick copper circuitry and the insulating substrate. Because printing and vacuum processing are carried out simultaneously in the same cavity, the solder resist is in a vacuum environment before it is cured, and air bubbles are expelled during the process of being coated on the board surface.

[0066] S502. Pre-curing treatment is performed on the solder resist material after the first printing. The preform after the first printing is removed from the vacuum chamber and placed in an oven or tunnel furnace for heating and baking. The temperature and time of the pre-curing treatment are set according to the type and thickness of the solder resist. As an optional implementation, the pre-curing temperature is 70~90℃ and the time is 20~40min. During the pre-curing process, the organic solvent in the solder resist gradually evaporates under heating conditions, and the cross-linking reaction between the resin molecular chains begins but is not yet complete. The solder resist changes from a fluid liquid to a semi-solid with a certain hardness and viscoelasticity. After pre-curing, the solder resist no longer flows and can maintain the shape and thickness formed in the first printing.

[0067] S503. Place the pre-cured outer circuit board blank into the vacuum chamber again and perform a second solder resist printing under vacuum conditions. This allows the solder resist material to be superimposed on the first printed solder resist layer to form a cover layer, and simultaneously removes air bubbles from the solder resist material. The pre-cured outer circuit board blank is placed back into the vacuum chamber. The vacuum pump is started to evacuate the chamber, bringing the vacuum level to the preset value and maintaining it. Under the maintained vacuum condition, the same solder resist material is used as the printing medium, and the screen printing device in the chamber is started to perform a second solder resist printing on the board surface.

[0068] The second printing process involves layering a cover layer on top of the solder resist layer formed in the first printing. This covers the surface of the outer circuitry and the stepped areas filled in the first printing. The first printing primarily addressed the step filling issue between the thick copper traces and the insulating substrate; the second printing adds another layer of solder resist over the circuit surface and the filled stepped areas, forming a complete solder resist cover layer. This ensures that the top and sidewalls of the outer circuitry are fully encapsulated by the solder resist. The second printing is also performed under vacuum conditions, with air bubbles being simultaneously removed during the printing process to ensure that no air bubbles remain in the resulting cover layer.

[0069] S504. The solder resist material after the second printing is post-cured to form a solder resist layer, resulting in the finished circuit board.

[0070] The PCB blank, after the second printing is completed, is placed in an oven for heating and baking. The post-curing temperature is 140~160℃, and the time is 40~80 minutes. During the post-curing process, the resin in the solder resist undergoes a full cross-linking reaction under high temperature conditions, forming an irreversible cured layer. After post-curing, the solder resist layer has sufficient hardness, adhesion, and heat resistance, providing effective insulation protection and environmental protection for the outer circuitry, thus obtaining the finished circuit board.

[0071] In this embodiment, the first solder resist printing is performed under vacuum conditions. During the process of the solder resist material being extruded onto the board surface, the embedded microbubbles expand, rise, and burst simultaneously under vacuum negative pressure, achieving simultaneous printing and degassing, eliminating the need for post-printing transfer to vacuum equipment for degassing. Pre-curing transforms the solder resist material into a semi-solid state, providing a stable substrate for the second printing. The second printing layer is superimposed on the first printed solder resist layer to form a capping layer, ensuring that the top and sidewalls of the outer layer circuitry are fully encapsulated. Similarly, air bubbles are simultaneously expelled under vacuum conditions. Post-curing allows the resin to fully cross-link, forming a network structure with sufficient hardness, adhesion, and heat resistance, providing effective insulation protection for the outer layer circuitry.

[0072] This application also provides an automotive circuit board, which is manufactured using the preparation method of any of the above embodiments. Please refer to... Figure 6 , Figure 6 This is a schematic diagram of the layer structure of an embodiment of the automotive circuit board provided in this application.

[0073] The automotive circuit board includes several inner circuit boards 1, an insulating adhesive layer 2, an outer circuit layer 3, a solder mask layer 4, and vias 5. The inner circuit boards 1 are arranged sequentially along their thickness direction, with an insulating adhesive layer 2 separating adjacent inner circuit boards 1, bonding them together as a single unit. The vias 5 penetrate each inner circuit board 1 and the insulating adhesive layer 2, and the walls of the vias 5 are provided with a copper layer, creating electrical interconnections between the inner circuit boards 1. The outer circuit layer 3 is disposed on the surface of the outermost inner circuit board 1 or the surface of the outermost insulating adhesive layer 2, and the solder mask layer 4 covers the surface of the outer circuit layer 3 and the exposed insulating substrate surfaces between adjacent outer circuit layers 3.

[0074] Specifically, each of the several inner layer circuit boards 1 includes an insulating substrate and an inner copper layer disposed on the surface of the insulating substrate. The insulating substrate can be made of a high Tg heat-resistant material, such as FR-4 type glass fiber cloth reinforced epoxy resin substrate or hydrocarbon substrate. The inner copper layer is formed by the inner layer circuit pattern transfer and vacuum etching steps in the aforementioned preparation method, and its thickness is determined according to design requirements. The inner layer circuit boards 1 are bonded together by an insulating adhesive layer 2, which can be a prepreg, such as an epoxy resin glass fiber cloth prepreg.

[0075] The via 5 penetrates each inner layer circuit board 1 and the insulating adhesive layer 2. The via 5 has a copper wall layer, creating an electrical interconnection between the inner layer circuit boards 1. This copper wall layer is formed by the chemical copper plating and electroplating thickening steps described in the aforementioned preparation method, continuously and uniformly covering the via 5's wall to achieve electrical conductivity between the inner layer circuit boards 1. The outer layer circuit layer 3 is disposed on the surface of the outermost inner layer circuit board 1 or the outermost insulating adhesive layer 2, and is formed through the outer layer circuit pattern transfer and electroplating steps described in the aforementioned preparation method. The outer layer circuit layer 3 is electrically connected to the copper wall layer of the via 5, thereby achieving electrical interconnection with each inner layer circuit board 1. The solder resist layer 4 covers the surface of the outer circuit layer 3 and the surface of the exposed insulating substrate between adjacent outer circuit layers 3. The solder resist layer 4 is formed by multiple printing and step-by-step curing processes in the aforementioned preparation method. It covers the top and sidewalls of the outer circuit layer 3 and fills the gap area between adjacent outer circuit layers, thus forming insulation protection and environmental protection for the outer circuit layer 3.

[0076] In an optional embodiment, the inner copper layer of the inner circuit board 1 has a thickness of 0.105~0.210 mm. The insulating adhesive layer 2 has a thickness of 0.05~0.30 mm. This thickness range covers the thickness of a single sheet of conventional prepreg and the total thickness range of multiple prepreg layers stacked together. The outer circuit layer 3 has a thickness of 0.105~0.210 mm, the same as the thickness range of the inner copper layer 12 of the inner circuit board 1, ensuring that the inner and outer circuit layers have consistent current carrying capacity. The solder mask layer 4 has a thickness of 0.02~0.08 mm. This thickness range can fully cover the stepped area of ​​the thick copper circuit while ensuring the insulation performance of the solder mask layer. The combination of the above-mentioned layer thickness ranges enables the automotive circuit board to meet the requirements of high current carrying capacity and high heat dissipation while possessing good interlayer bonding and structural stability.

Claims

1. A method for manufacturing an automotive circuit board, characterized in that, The preparation method includes: The inner layer circuit pattern is transferred and vacuum etched onto the insulating substrate to obtain the inner layer circuit board. Several layers of the inner circuit board are alternately aligned and stacked through an insulating adhesive layer, and then pressed together at preset temperatures and pressures in segments to obtain a board blank; The slab blank is drilled and the hole walls are metallized to form a conductive path between the circuit boards of each layer, thus obtaining a conductive slab blank. The outer layer circuit pattern is transferred and electroplated on the conductive board blank to obtain the outer layer circuit board blank; The outer circuit board blank is subjected to several printing and step-by-step curing processes to cover the surface of the outer circuit board blank, thereby obtaining the finished circuit board.

2. The method for preparing an automotive circuit board according to claim 1, characterized in that, The process of alternately aligning and stacking several layers of the inner circuit board through an insulating adhesive layer, and then pressing them together at preset temperatures and pressures in stages to obtain a board blank, includes: By performing alkaline cleaning and activation treatment on the surface of the inner circuit board, and then placing it in a browning solution for a browning reaction, an organometallic film is formed on the surface of the inner circuit board. Several layers of the inner circuit board, after browning treatment, are alternately aligned and stacked using an insulating adhesive layer to obtain a composite. The composite is placed in a pressing device for vacuuming, and then subjected to segmented temperature and pressure pressing.

3. The method for preparing an automotive circuit board according to claim 2, characterized in that, The segmented temperature and pressure pressing includes temperature control and pressure control; The temperature control is to raise the temperature to a first temperature at a first heating rate and then raise the temperature to a second temperature at a second heating rate, wherein the first heating rate is less than the second heating rate. The pressure control involves increasing the pressing pressure from the initial pressure to a preset pressure after the temperature reaches the first temperature, and then maintaining the temperature and pressure at the second temperature and the preset pressure.

4. The method for preparing an automotive circuit board according to claim 1, characterized in that, The process of drilling and metallizing the hole walls of the slab to form conductive paths between the circuit board layers, resulting in a conductive slab, includes: After drilling holes in the slab to form through holes, the through holes are subjected to plasma degumming treatment to remove adhesive residue from the hole walls. The via is subjected to chemical copper plating treatment to deposit a conductive seed layer on the via wall; The conductive seed layer is electroplated by applying alternating positive and negative pulses, wherein the current density of the negative pulse is greater than the current density of the positive pulse.

5. The method for preparing an automotive circuit board according to claim 1, characterized in that, The process of transferring the outer layer circuit pattern and electroplating the conductive board blank to obtain the outer layer circuit board blank includes: A photosensitive film is attached to the surface of the conductive plate blank. After exposure and development, the non-circuit area in the conductive plate blank is covered by the photosensitive film, exposing the circuit area. Electroplating is performed on the circuit area to increase the copper layer thickness in the circuit area to a preset value; Remove the photosensitive film and then etch the outer copper layer after removing the photosensitive film to remove the copper layer outside the circuit area, thus obtaining the outer circuit board blank.

6. The method for preparing an automotive circuit board according to claim 1, characterized in that, The process of performing several printing and step-by-step curing processes on the outer circuit board blank to cover the surface of the outer circuit board blank and obtain the finished circuit board includes: Using solder resist as the printing medium, the outer circuit board blank is placed in a vacuum chamber, and the first solder resist printing is performed under vacuum conditions, so that the solder resist fills the surface of the exposed insulating substrate between adjacent circuits, and air bubbles in the solder resist are simultaneously discharged. Pre-curing treatment is performed on the solder resist material after the first printing. The pre-cured outer circuit board blank is placed in the vacuum chamber again, and a second solder resist printing is performed under vacuum conditions, so that the solder resist material is superimposed on the solder resist layer printed in the first printing to form a cover layer, and air bubbles in the solder resist material are simultaneously discharged. The solder resist material after the second printing is post-cured to form a solder resist layer, resulting in the finished circuit board.

7. The method for preparing an automotive circuit board according to claim 6, characterized in that, The pre-curing treatment is performed at a temperature of 70~90℃ for a time of 20~40 minutes. The post-curing treatment is performed at a temperature of 140~160℃ for a time of 40~80 minutes.

8. An automotive circuit board, characterized in that, It is prepared by any one of claims 1 to 7.

9. The automotive circuit board according to claim 8, characterized in that, The automotive circuit board includes: several inner circuit board layers, an insulating adhesive layer, an outer circuit layer, a solder mask layer, and vias; The inner circuit boards of several layers each include an insulating substrate and an inner copper layer disposed on the surface of the insulating substrate; An insulating adhesive layer is disposed between two adjacent inner circuit boards to bond the inner circuit boards together as a whole; An outer circuit layer is disposed on the surface of the inner circuit board or the surface of the insulating adhesive layer; A solder resist layer covers the surface of the outer circuit layer and the surface of the insulating substrate exposed between adjacent outer circuit layers; The vias penetrate each of the inner circuit boards and the insulating adhesive layer. The walls of the vias are provided with a copper layer, so that the inner circuit boards of each layer are electrically interconnected.

10. The automotive circuit board according to claim 9, characterized in that, The copper layer thickness of the inner circuit board is 0.105~0.210mm; The thickness of the insulating adhesive layer is 0.05~0.30mm; The thickness of the outer circuit layer is 0.105~0.210mm; The thickness of the solder resist layer is 0.02~0.08mm.

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