Method for manufacturing embedded copper block circuit board for high efficiency thermal management module and circuit board

Abstract

The application discloses a manufacturing method of an embedded copper block circuit board for a high-efficiency thermal management module, takes a copper foil to adhere to the surface of a single-side adhesive film, forms a brown copper block adhesive film through pattern transfer and brownization, takes a release film to make a first windowing on the edge of the copper block to form a windowed release film, makes a core plate with a first groove corresponding to the copper block, and sequentially stacks the RCC plate, the windowed release film, the core plate and the brown copper block adhesive film with the copper block facing the core plate, removes the auxiliary materials after pressing, and finally forms the circuit board through a post-process, so that the technical difficulties of insufficient glue filling, cavities and poor copper block bonding caused by insufficient adhesive amount of the laminated glue when the thin circuit board is embedded with the copper block are solved through the effective cooperation of the technical features of electrolytic copper foil etching forming, single-side adhesive film whole transfer first copper block, windowed release film directional flow guiding and RCC resin pressing and filling.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing, and more particularly to a method for manufacturing an embedded copper block circuit board for a high-efficiency thermal management module, and a circuit board. Background Technology

[0002] With the rapid development of communication technology, artificial intelligence computing modules, and other fields, printed circuit boards (PCBs) are evolving towards higher integration, miniaturization, and higher frequencies. This has led to a dramatic increase in heat flux density per unit volume. Prolonged high-temperature operation not only degrades the electrical performance of components but also seriously threatens product lifespan and reliability. Therefore, efficient thermal management has become one of the core technological barriers in PCB design and manufacturing.

[0003] Currently, the commonly used heat conduction solutions mainly include two methods: heat conduction on metal-based circuit boards and heat conduction using embedded high thermal conductivity metal blocks. (1) With a high thermal conductivity of 380W / (m·K) to 400W / (m·K), copper blocks can significantly improve the thermal conductivity of circuit boards and have become the mainstream raw material in the field of embedded thermal conductivity. (2) The embedded copper block process is usually applied to circuit board products with a thickness of 1.0mm or more. This type of board is thicker and has sufficient prepreg and adhesive material in the stacked structure. During the pressing process, it can effectively flow and fill the gap between the copper block and the core board opening, thereby ensuring sufficient filling and good bonding of the copper block. The process is mature and the quality is controllable.

[0004] However, as electronic terminal products iterate towards thinner and lighter designs, requiring PCB board thickness to be reduced to 0.5 mm or less, the aforementioned mature processes face severe technical bottlenecks.

[0005] When the board thickness is reduced to ≤0.5mm, the total amount of colloid available for flow filling inside the board is significantly reduced. After lamination, the interlayer colloid's ability to fill the gap between the copper block and the slot is greatly weakened, which can easily lead to problems such as insufficient colloid filling, voids, and insufficient bonding force of the copper block. This results in a sharp increase in the processing difficulty of embedding the copper block, making it difficult to guarantee the yield of finished products and significantly increasing the risk of quality reliability. Furthermore, the miniaturization trend of high power density devices has also placed extreme demands on the size of embedded copper blocks (e.g., ultra-small sizes of ≤1.5 mm × 1.5 mm). The main technical challenges of embedding copper blocks in thin circuit boards are: on the one hand, in traditional processes, copper blocks are mostly obtained by machining copper sheets through mechanical milling. This method is limited by the minimum diameter of the cutting tool and the ductility of copper, making it difficult to mass-produce small copper blocks with a size of ≤1.5 mm × 1.5 mm; on the other hand, if densely filled thermally conductive vias are used to replace solid copper blocks as heat conduction channels, the longitudinal equivalent thermal conductivity of the vias is much lower than that of solid copper due to the extremely thin thickness of the electroplated copper layer. The heat dissipation effect is significantly different from that of the embedded copper block solution, and it cannot truly meet the thermal management requirements under high power conditions.

[0006] Therefore, based on the above background and problems, there is a need to provide a new method for manufacturing an embedded copper block circuit board for a high-efficiency thermal management module and the circuit board itself. Summary of the Invention

[0007] This invention aims to solve a series of problems in the fabrication process of thin circuit boards with embedded copper blocks for high-efficiency thermal management modules, including insufficient adhesive layering leading to incomplete filling of the narrow gap between the copper block and the groove, poor bonding strength, and the inability of traditional machining to meet the precision requirements of mass production of micro copper blocks. The invention provides a method for manufacturing a circuit board with embedded copper blocks for high-efficiency thermal management modules. The circuit board is manufactured according to design data, and the manufacturing method includes the following steps: S10: Take copper foil and single-sided adhesive film, attach the copper foil to the surface of the single-sided adhesive film, and then perform the first pattern transfer and browning in sequence. The copper foil forms several first copper blocks, and the whole forms a browned copper block adhesive film. S20: Take out the release film and make a first window corresponding to the edge position of several first copper blocks to form a windowed release film; S30: Fabricate a core board according to the design data, and the core board has a first groove corresponding to the copper block; S40: Take the RCC board, stack the RCC board, the windowed release film, the core board, and the copper-coated adhesive film in sequence to form a stacked structure, then press them together to form a press board, then remove the single-sided adhesive film, the RCC board, and the windowed release film in sequence, and then process them in subsequent processes to form the circuit board. The first copper block faces the core plate.

[0008] Furthermore, the method for manufacturing the first copper block includes: Take a copper foil, which is divided into a first side and a second side. Take a first dry film and attach the first dry film to the first side and the second side of the copper foil. Expose the entire surface of the first dry film on the first side; A first dry film pattern is made on the pattern of the second side corresponding to the first copper block, and then the first dry film on the first side and the second side is removed by the first etching. Then, a second single-sided adhesive film is attached to the second side, and a second dry film is taken and attached to the first side. The second dry film pattern is formed corresponding to the pattern of the first copper block. Then, a second etching is performed, and then the second dry film pattern is removed. After that, browning is performed to form several of the first copper blocks.

[0009] Furthermore, the thickness of the first etching is 1 / 3 to 2 / 5 of the thickness of the copper foil.

[0010] Furthermore, the pressing time is 1.5 to 2.5 hours, the heating rate is 1.4°C / min to 1.8°C / min, and the temperature is maintained at the highest temperature range for 30 minutes or more.

[0011] Furthermore, the stacked structure includes: A first release film and a first steel plate are sequentially disposed outward from one side of the RCC plate; A second release film and a second steel plate are sequentially disposed outward from one side of the copper-coated block adhesive film.

[0012] Further, the pressing includes aligning and stacking the core board and the brown copper block adhesive film before stacking, cold pressing to form a cold press plate, filling the edges of a plurality of the first copper blocks in the cold press plate with resin ink, and then baking to form a resin core board. The stacked structure is formed by sequentially stacking the RCC board, the windowed release film, and the resin core board.

[0013] Furthermore, the cold pressing is performed at a temperature of 20°C to 30°C, using a pressure value of 4.0MPa to 5.0MPa, and a pressing time of 10 to 15 seconds.

[0014] Furthermore, the thickness of the resin ink filling is 3 / 5 to 2 / 3 of the depth of the first tank.

[0015] Furthermore, the RCC board is replaced by a laminated structure of thin copper foil and high-flow prepreg; In the stacked structure, the high-flow adhesive semi-cured sheet faces the windowed release film.

[0016] The present invention also provides a circuit board, which is manufactured using the above-described method.

[0017] The main beneficial effects of this technical solution include: (1) By effectively combining the technical features of “electrolytic copper foil etching and forming + single-sided adhesive film overall transfer of the first copper block + windowed release film directional flow + RCC resin pressing and filling”, the technical problems such as insufficient glue filling, voids and poor bonding force of copper blocks caused by insufficient glue layering when embedding copper blocks in thin circuit boards with a thickness of ≤0.5mm are solved. In addition, a two-stage etching process is used to control the side etching of the copper block to replace traditional machining, making the cross-section of the copper block more rectangular. The excellent fluidity of RCC semi-cured resin ensures that the resin can fully penetrate into the narrow gap between the copper block and the tank, thus achieving a firm embedding of the copper block in the ultra-thin plate. (2) Electrolytic copper foil etching is used to replace the traditional mechanical milling of copper plates. Relying on the graphic transfer technology, the first copper block with a small size can be mass-produced, breaking through the technical limitation of traditional milling that is limited by the diameter of the tool and cannot process micro copper blocks below the millimeter level. At the same time, the first copper block after etching is left on the single-sided adhesive film without being removed, so that each copper block maintains its relative position and forms an integrated transfer unit. This realizes the one-time overall picking of dozens of micro copper blocks and the precise alignment of the core board slotting, which fundamentally solves the problem that micro copper blocks are easily lost, flipped or misplaced during discrete transfer, and greatly improves the assembly efficiency and positioning reliability.

[0018] (3) By adding resin ink pre-filling and vacuum degassing processes before RCC pressing and filling, a dual filling technology solution of "resin ink pre-filling + RCC resin supplementary filling" is formed. The resin ink, under the combined action of screen printing pressure and vacuum negative pressure, fully penetrates into the tiny dead corners at the bottom of the gap between the copper block and the tank and removes air bubbles. Then, it reaches a semi-cured state after low-temperature baking. The RCC resin fills the remaining space during high-temperature pressing, forming a synergistic effect of dual filling. This effectively avoids voids and interface delamination that may occur with a single filling method, significantly improves the fullness of filling and interlayer bonding, and ensures the mechanical reliability and thermal stability of the embedded copper block during subsequent processing and long-term use. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is a process flow diagram of an embodiment of the present invention; Figure 2 This is a cross-sectional schematic diagram of the copper-coated block adhesive film according to an embodiment of the present invention; Figure 3 This is a cross-sectional schematic diagram of the windowed release film according to an embodiment of the present invention; Figure 4 This is a cross-sectional schematic diagram of the windowed release film according to an embodiment of the present invention; Figure 5 This is a cross-sectional schematic diagram of the core plate according to an embodiment of the present invention; Figure 6 This is a cross-sectional schematic diagram of the stacked structure according to an embodiment of the present invention; Figure 7 This is a cross-sectional schematic diagram of the filling core plate according to an embodiment of the present invention; Figure 8 This is a cross-sectional schematic diagram of another stacked structure according to an embodiment of the present invention; Figure 9 This is a cross-sectional schematic diagram of another stacked structure according to an embodiment of the present invention; Figure 10 This is a cross-sectional schematic diagram of the pressing plate according to an embodiment of the present invention; Figure 11 This is a cross-sectional schematic diagram of the grinding plate according to an embodiment of the present invention; Figure 12 This is a micro-slice image of the cross-sectional structure of the circuit board according to an embodiment of the present invention; Figure 13 Thermal management imaging inspection diagram of existing through-hole thermal conductive circuit boards; Figure 14 for Figure 12 A magnified view of a portion of the image; Figure 15 Thermal management imaging inspection image of an embedded copper block circuit board fabricated for this embodiment; Figure 16 for Figure 14 A magnified view of a portion of the image.

[0021] Explanation of icon numbers: 10. Copper block adhesive film with brown coating; 1010. Single-sided adhesive film; 1020. First copper block; 1030. First dry film pattern; 1040. Second single-sided adhesive film; 1050. Second single-sided adhesive film; 20. Windowed release film; 2010. First window; 30. Core board; 3010. Second tank; 40. Stacked structure; 4010. RCC board; 4020. First release film; 4030. First steel plate; 4040. Second release film; 4050. Second steel plate; 40A. Another stacked structure; 50. Pressed plate; 60. Grinding plate; 70. Filler core board; 7010. Resin ink; 80. Resin core board; 40B. Yet another stacked structure; 410. Thin copper foil; 420. High-flow prepreg; 90. Circuit board.

[0022] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0025] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0026] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0027] To better understand the above technical solution, the following detailed explanation is provided in conjunction with the accompanying drawings.

[0028] Please see Figure 1 , Figure 1 This is a process flow diagram of an embodiment of the present invention.

[0029] The method for manufacturing an embedded copper circuit board for a high-efficiency thermal management module proposed in this embodiment includes the following steps: Please see Figure 2 , Figure 2 This is a cross-sectional schematic diagram of the copper-coated block adhesive film according to an embodiment of the present invention.

[0030] Step S10: Take copper foil and single-sided adhesive film 1010, attach the copper foil to the surface of single-sided adhesive film 1010, and then perform the first pattern transfer and browning in sequence. The copper foil forms several first copper blocks 1020, and the whole is formed into a browned copper block adhesive film 10.

[0031] Because the copper blocks formed after etching of electrolytic copper foil are thin and have tiny planar dimensions (less than 1.5 mm × 1.5 mm), if they are transferred in discrete individual form, the copper blocks are prone to being lost, flipped, or having their relative positions disordered, making it impossible to achieve precise alignment with the slots on the core board. Therefore, in this step, all the etched copper blocks are left on the single-sided adhesive film 1010 without being removed, so that each first copper block 1020 maintains its predetermined relative position formed in the etching process, thus forming an integrated transfer unit. Based on this, operators or automated equipment can pick up dozens of micro copper blocks at once and align them with the corresponding slots on the core board, greatly improving assembly efficiency and positioning accuracy.

[0032] Meanwhile, the single-sided adhesive film 1010 is made of high-temperature and corrosion-resistant material, which can maintain dimensional stability during etching and browning processes and will not deform due to chemical corrosion or temperature changes. Its single-sided adhesive design ensures that the first copper block 1020 is firmly attached during processing and is easy to peel off as a whole after processing, taking into account both the reliability of the processing process and the convenience of subsequent film removal.

[0033] It is worth noting that in step S10, the copper foil is selected with a thickness of ≤0.5mm, while the size of the single-sided adhesive film 1010 is ≥30mm larger than the copper foil on one side, to ensure that the adhesive film completely covers the copper foil and provides sufficient gripping margin.

[0034] During lamination, the rough side of the copper foil is aligned with the adhesive side of the single-sided adhesive film 1010. The foil is then pressed flat by a laminator to ensure complete adhesion between the copper foil and the single-sided adhesive film 1010, free from bubbles and wrinkles. This ensures that the chemical solution will not seep into the interface between the copper foil and the single-sided adhesive film 1010 during subsequent processing, preventing localized side etching. After lamination and the first pattern transfer are completed, the copper foil is etched using an acidic etching solution to form several independent first copper blocks 1020. Subsequently, a browning treatment is performed to form a browning film on the surface of the copper blocks, enhancing the reliability of the bonding interface between the copper foil and the subsequent interlayer filler resin.

[0035] Please see Figure 3 , Figure 3 This is a schematic cross-sectional view of one type of copper-coated block adhesive film.

[0036] Further, the method for manufacturing the first copper block 1020 includes: taking a copper foil, the copper foil being divided into a first side and a second side; taking a first dry film and attaching the first dry film to the first side and the second side of the copper foil; exposing the entire first dry film on the first side; creating a first dry film pattern 1030 on the second side corresponding to the pattern of the first copper block 1020; then etching for the first time to remove the first dry film on the first and second sides; then attaching a second single-sided adhesive film 1040 to the second side, and taking the second dry film, attaching it to the first side, creating a second dry film pattern 1050 corresponding to the pattern of the first copper block 1020; then etching for the second time, then removing the second dry film pattern 1050; and then browning to form several first copper blocks 1020.

[0037] Since the copper foil used in this embodiment is relatively thick (usually ≥175μm), if a single etching process is used, the sidewall of the copper block will be excessively eroded due to the lateral etching effect of the etching solution. This results in the first copper block 1020 having a significantly trapezoidal cross-section that is wider at the top and narrower at the bottom. When it is subsequently pressed into the core board groove, its bottom dimension is much smaller than its top dimension. This will not only create an irregular gap between the copper block and the groove wall, increasing the difficulty of resin filling, but may also lead to insufficient local heat conduction path cross-sectional area due to the reduced actual contact area between the first copper block 1020 and the groove, causing uneven heat conduction or heat bottleneck problems.

[0038] Therefore, this embodiment employs a two-stage etching process: the first etching is micro-etching, which forms a shallow groove outline on the second side of the copper foil; then, a single-sided adhesive film 1010 is attached to cover the micro-etched surface, and a second etching is performed from the first side of the copper foil until the copper foil is etched through to form an independent first copper block 1020. This step-by-step etching method effectively limits the lateral etching effect of the etching solution on the sidewall of the copper block, making the cross-section of several first copper blocks 1020 tend to be rectangular, thereby ensuring that the gap between the first copper block 1020 and the core board groove is uniform and consistent, which is conducive to the subsequent full filling of resin, while ensuring that the copper block has a uniform thermal conductivity cross-sectional area.

[0039] Furthermore, the thickness of the first etching is 1 / 3 to 2 / 5 of the copper foil thickness.

[0040] This can effectively prevent the single-sided adhesive film 1010 from being embedded in the micro-etched groove during lamination when the micro-etching depth is too deep. After lamination, this part of the adhesive film is difficult to completely peel off, and the residual adhesive film will occupy the gap space, forming a physical obstacle to resin filling.

[0041] It should be noted that conventional methods for improving side etching in the prior art usually focus on adjusting the composition of the etching solution or optimizing etching parameters (such as temperature, spray pressure, conveying speed, etc.). However, for thick copper foil with a thickness of ≥175μm, the improvement of side etching by simply relying on process parameter optimization is limited and the adjustment cost is high. Therefore, this embodiment achieves high-precision forming of micro copper blocks of thick copper foil by using two etching processes in conjunction with a single-sided adhesive film 1010 without increasing the cost of special chemicals.

[0042] It is worth noting that the dry film in the above steps can also be replaced by a wet film. That is, a wet film is applied to the second side of the copper foil at the positions corresponding to several first copper blocks. After preheating, exposure and development, the subsequent etching process is exactly the same as when using a dry film. The wet film has good filling and adhesion, and is especially suitable for scenarios where there are micro-roughness or slight scratches on the copper foil surface. It can achieve seamless bonding with the copper surface, further reducing the risk of micro-gap or plating during pattern transfer.

[0043] In the prior art, embedded copper blocks are usually obtained by machining copper plates using mechanical milling. In this embodiment, however, embedded copper blocks are made by electrolytic copper foil through pattern transfer and etching.

[0044] The differences between the two are shown in the table below:

[0045] As can be seen from the table above, the embedded first copper block 1020 that can be processed in this embodiment is smaller in size, thinner in thickness, and has higher precision, which is more advantageous for the processing of embedded copper blocks in thin plates.

[0046] In summary, this embodiment uses electrolytic copper foil etching to replace traditional mechanical processing of copper blocks, which has the advantage of overcoming the manufacturing bottleneck of micro copper blocks: (1) Traditional milling is limited by the diameter of the tool and the toughness of the material, and cannot process copper blocks that are small in size or thin in thickness; while etching process relies on the precision of pattern transfer, and can mass-produce first copper blocks 1020 that are small in size or thin in thickness, and the size consistency is good. (2) After the first copper block 1020 is etched, it is left on the single-sided adhesive film 1010 without being removed, forming the whole of the copper block adhesive film 10. This avoids the loss, flipping or misalignment that may occur during the transfer of the first copper block 1020 in the form of discrete individuals. At the same time, it provides a structural basis for the one-time overall alignment with the core board slotting in the later stage, which greatly simplifies the operation difficulty of the first copper block 1020.

[0047] Please see Figure 4 , Figure 4 This is a cross-sectional schematic diagram of the windowed release film according to an embodiment of the present invention.

[0048] Step S20: Take out the release film and make the first window 2010 corresponding to the edge position of several first copper blocks 1020 to form the windowed release film 20.

[0049] Specifically, the release film 20 with open window is made of a high temperature resistant material with a temperature resistance of ≥220℃ and a thickness of ≥200μm. The first window 2010 is located on the release film 20 corresponding to the edge of the first copper block 1020. Its opening size is 1 / 5 to 1 / 2 of the edge length of the first copper block 1020, and its opening width is 0.3mm to 0.6mm. The edge of the first window 2010 extends into the area of ​​the first copper block 1020 by 0mm to 0.1mm.

[0050] The thickness of the windowed release film 20 provides it with sufficient rigidity during high-temperature pressing to maintain the stability of the window shape and prevent resin flow from becoming uncontrolled due to window deformation. The opening size and width of the first window 2010 provide a smooth flow channel for the RCC resin, allowing the molten resin to flow directionally into the narrow gap between the first copper block and the tank, while also limiting the amount of resin overflow to prevent the resin from flowing onto the core board surface over a large area, making it difficult to peel off the windowed release film 20 after pressing. Furthermore, the edge of the first window 2010 extends 0 mm to 0.1 mm into the area of ​​the first copper block 1020, ensuring that the resin outlet precisely corresponds to the surrounding gaps of the first copper block 1020, allowing the resin to be directly injected into the area to be filled, reducing the flow path and filling resistance.

[0051] As a preferred embodiment, the windowed release film 20 is made of TPX, PTFE or ETFE. These materials have both excellent high temperature resistance and low thermal deformation characteristics. They can maintain good dimensional stability and release effect at the pressing temperature. After pressing, they can be cleanly peeled off from the board surface without any residue adhering to the surface of the core board 30.

[0052] Please see Figure 5 , Figure 5 This is a cross-sectional schematic diagram of the core board according to an embodiment of the present invention.

[0053] Step S30: The core board 30 is manufactured according to the design data, and the core board 30 has a first groove corresponding to the copper block.

[0054] Furthermore, the first tank is composed of several second tanks 3010, and each of the several second tanks 3010 corresponds to a first copper block 1020.

[0055] Specifically, a double-sided copper-clad laminate is selected to make the core board 30. The thickness of the core board and the copper foil are both ≤0.5mm. The thickness of the copper layer on the surface of the double-sided copper-clad laminate is 10μm to 75μm to reserve processing allowance for subsequent circuit fabrication. After positioning and drilling the core board 30 according to the design data, a first groove composed of several second grooves 3010 is made by milling. Several second grooves correspond one-to-one with several first copper blocks 1020. The planar dimension of each second groove 3010 is larger than the dimension of the corresponding first copper block 1020 by 0.08mm to 0.25mm on one side.

[0056] First, the thickness of the core board 30 is designed to be consistent with the thickness of the copper foil, ensuring that the upper surface of the copper block and the board surface of the core board 30 are at the same height after lamination. This provides a flat board surface base for the subsequent grinding process and avoids local depressions or protrusions caused by thickness differences from affecting the accuracy of subsequent circuit fabrication.

[0057] Secondly, the slot size of the core board 30 is designed to be 0.08mm to 0.25mm larger on each side than the size of the first copper block 1020. This is to avoid the molten resin from failing to fully penetrate during pressing due to excessive flow resistance when the gap is less than 0.08mm, which could easily create voids in the filling. On the other hand, it is to avoid the risk of the first copper block 1020 shifting position during pressing due to increased movement space within the second groove 3010 when the gap is greater than 0.25mm. Therefore, a gap range of 0.08mm to 0.25mm is preferred to effectively ensure the positioning accuracy and filling reliability of the first copper block 1020 after it is embedded.

[0058] Please see Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 and Figure 11 ; Figure 6 This is a cross-sectional schematic diagram of the stacked structure according to an embodiment of the present invention; Figure 7 This is a cross-sectional schematic diagram of the filling core plate according to an embodiment of the present invention; Figure 8 This is a cross-sectional schematic diagram of another stacked structure according to an embodiment of the present invention; Figure 9 This is a cross-sectional schematic diagram of another stacked structure according to an embodiment of the present invention; Figure 10 This is a cross-sectional schematic diagram of the pressing plate according to an embodiment of the present invention; Figure 11 This is a cross-sectional schematic diagram of the grinding plate according to an embodiment of the present invention.

[0059] Step S40: Take RCC board 4010, and stack RCC board 4010, windowed release film 20, core board 30 and copper-coated adhesive film 10 in sequence to form stacked structure 40. Then press them together to form a press board 50. Then remove single-sided adhesive film 1010, RCC board 4010 and windowed release film 20 in sequence. After subsequent processing, circuit board 90 is formed; wherein, the first copper block 1020 faces the core board 30.

[0060] This step uses RCC board 4010 as the filler medium. Its core advantage is that the semi-cured resin layer of RCC board 4010 does not contain glass fiber reinforcement. During high-temperature pressing, it has low melt viscosity and flowability far superior to traditional semi-cured sheets. It can fully penetrate into the narrow gap between the first copper block 1020 and the second tank 3010, effectively solving the problem of insufficient resin filling caused by insufficient total amount of semi-cured sheets in the stack of thin plates. At the same time, the absence of glass fiber also avoids fiber accumulation at the entrance of the narrow gap, forming bridging blockage, and ensuring unobstructed resin filling path.

[0061] In this embodiment, the calculation method for the amount of adhesive used in the pressing process is as follows: M=Vρw In the formula: V – Total void volume requiring adhesive filling, in cm³ 2 ; ρ—cured density of RCC resin, typically ranging from 1.22 to 1.26 g / cm³. 3 ; w—RCC resin utilization coefficient, generally ranging from 0.97 to 0.99.

[0062] Specifically, based on the glue filling amount M value calculated by the above formula, combined with the glue content per unit area of ​​the selected RCC board 4010, the required size and amount of RCC board 4010 can be determined to ensure that there is sufficient resin to fill all gaps during the pressing process, while avoiding excessive resin leading to serious glue overflow.

[0063] After the pressing in step S40 is completed, the single-sided adhesive film 1010 is removed, and the residual copper foil and semi-cured resin layer of the RCC board 4010 are removed. The window release film 20 is peeled off, and the board surface is then polished to remove excess adhesive and surface burrs, forming a flat polished board 60. After that, the polished board 60 is processed in sequence with drilling, electroplating, outer layer pattern transfer, surface treatment, solder mask, electrical testing and appearance inspection, and finally formed into the finished circuit board 90.

[0064] It is worth noting that the removal of the single-sided adhesive film 1010 is performed after the pressing is completed. At this time, the first copper block 1020 has been firmly fixed in the second groove 3010 of the core board by the resin of the RCC board 4010. The single-sided adhesive film 1010 only serves as a temporary positioning carrier during the pressing process and has completed its auxiliary function. When the single-sided adhesive film 1010 is peeled off in the subsequent process, the position of the first copper block 1020 will not be disturbed. At the same time, the single-sided adhesive film 1010 can be completely removed from the surface and has the possibility of being reused.

[0065] Furthermore, at this point, the semi-cured resin of the RCC board 4010 has fully filled the gaps around the copper block and completed curing during the pressing process, forming a dense filler layer; while the windowed release film 20, because it is pre-set with a first window 2010, plays a directional guiding and selective blocking role for the flow of resin in the RCC board 4010 during the pressing process, and only a small amount of controllable overflow glue adheres to its surface, so that it will not cause tearing or residual defects to the board surface when peeled off.

[0066] The final grinding process is used to remove residual burrs and minor resin protrusions from the board surface, ensuring that the board surface flatness meets the requirements of subsequent circuit fabrication. Since the thickness of the copper block is designed to be consistent with the thickness of the core board, the overall height of the board surface is uniform after lamination. Therefore, the amount of grinding can be controlled within a very small range, ensuring the thickness accuracy of the finished board and the reliability of the copper block embedding.

[0067] Optionally, the pressing time is 1.5 to 2.5 hours, the heating rate is 1.4℃ / min to 1.8℃ / min, and the temperature is maintained at the highest temperature range for ≥30 minutes.

[0068] This avoids the problems of premature resin flow and insufficient filling caused by excessively rapid heating, and also prevents the production efficiency from decreasing due to excessively slow heating. The high-temperature section (≥180℃) is maintained for no less than 30 minutes to ensure that the resin reaches sufficient curing degree, so that a reliable bonding interface is formed between the first copper block 1020 and the tank wall of the second tank 3010, ensuring the bonding strength and reliability of the first copper block 1020 in subsequent processing and use.

[0069] Optionally, the stacked structure 40 includes: a first release film 4020 and a first steel plate 4030 sequentially disposed outward from one side of the RCC plate 4010; and a second release film 4040 and a second steel plate 4050 sequentially disposed outward from one side of the coated copper block adhesive film.

[0070] During the pressing process, the first steel plate 4030 and the second steel plate 4050 provide uniform pressure to the stacked structure 40, ensuring that the resin flows and fills fully in the horizontal direction. At the same time, they constrain the stacked structure 40 to remain flat under high temperature and high pressure, preventing the plate from warping. After pressing, the first release film and the second release film allow the pressed plate 50 to be smoothly separated from the first steel plate 4030 and the second steel plate 4050, preventing the molten resin from sticking the steel plate to the plate, ensuring smooth demolding and cleanliness of the plate surface.

[0071] Please refer to it again. Figure 7 and Figure 8 .

[0072] Further, the pressing process includes aligning and cold-pressing the core board 30 and the copper-coated film 10 before stacking to form a cold-pressed plate, then filling the edges of several first copper blocks 1020 in the cold-pressed plate with resin ink 7010, and then baking to form a resin core board 70; thereby forming another stacking structure 40A, in which the RCC plate 4010, the windowed release film 20 and the resin core board 70 are stacked in sequence.

[0073] Furthermore, cold pressing is performed at a temperature of 20°C to 30°C, using a pressure of 4.0MPa to 5.0MPa, and a pressing time of 10 to 15 seconds; this allows the first copper block 1020 to be pre-embedded in the second groove 3010 and form a tight contact, ensuring that the relative position of the first copper block 1020 and the second groove 3010 does not shift in subsequent processes.

[0074] Subsequently, resin ink 7010 is filled into the edge gaps between several first copper blocks 1020 and the second groove 3010 in the cold press plate using screen printing to form a resin pre-filled plate. The resin pre-filled plate is placed in a vacuum chamber and left to stand while being vacuumed. The vacuum pressure is -0.06MPa to -0.1MPa, and the processing time is 5 to 10 minutes. Air bubbles trapped inside the resin ink 7010 are extracted. At the same time, the negative pressure environment is used to allow the resin ink 7010 to further penetrate into the corners and bottoms of the gaps, ensuring that the ink fully wets and fills the inner wall of the gaps.

[0075] After vacuum treatment, a low-temperature baking process is performed at a temperature of 70°C to 80°C for 20 to 45 minutes. This allows the filling resin ink 7010 to reach a semi-cured state, which enables it to react with the resin of the RCC board 4010 during the subsequent lamination process, enhancing the bonding force between the copper block and the core board. It also prevents the resin surface from becoming too dense and smooth after complete curing, thus avoiding interfacial delamination or new filling dead corners between the resin and the subsequent RCC board 4010 resin. This ensures the reliability of the interfacial bonding between the double filling layers. After the above pretreatment, the resin core board 70 is formed.

[0076] The final stacked structure is formed by stacking the RCC board 4010, the windowed release film 20 and the resin core board 70 in sequence, then pressing them together, and then processing them in subsequent processes to form another type of circuit board.

[0077] Optionally, an aluminum screen printing resin ink 7010 can be used. The aluminum screen has high rigidity and wear resistance, which can maintain the stability of the window shape during the screen printing process and ensure that the resin ink 7010 is accurately positioned in the gap between the edges of the copper block.

[0078] Optionally, the thickness of the filling resin ink is 3 / 5 to 2 / 3 of the depth of the first tank.

[0079] This is equivalent to forming a pre-filled layer of controllable thickness on the inner wall of the gap and in the bottom dead corner, forming a double filling of the gap by filling the gap with resin ink 7010 and supplementing the gap with RCC glue. This not only ensures the effective filling of the dead corner area, but also leaves enough space for the resin of RCC board 4010 to penetrate, so that the resin of RCC board 4010 can flow smoothly into and come into contact with the semi-cured pre-filled resin ink 7010 during pressing.

[0080] Please refer to it again. Figure 9 .

[0081] Furthermore, the RCC board 4010 is replaced by a laminated structure of thin copper foil 410 and high-flow prepreg 420; forming another stacked structure 40B in which the high-flow prepreg 420 faces the windowed release film 20.

[0082] Specifically, the thickness of the thin copper foil 410 is 5μm to 20μm. During the pressing process, it forms a physical constraint on the resin colloid flowing out after the high-flow-rate prepreg 420 melts, preventing the colloid from overflowing excessively. The high-flow-rate prepreg 420 is a resin colloid prepreg containing a glass fiber woven mesh, with a colloid content of 60% to 75%. At the pressing temperature, it can provide a more abundant resin flow, ensuring that after the gap between the first copper block 1020 and the second tank 3010 is pre-filled by the resin ink 7010, there is still enough colloid to fill the remaining gap.

[0083] When the overall plate is relatively thick, or the shape of the first copper block 1020 is more complex and has more corners, if it is not pre-filled, the first copper block 1020 and the second groove 3010 are filled by pressing the high-flow-rate prepreg 420 together once. Due to the large and narrow gap depth, the resin is difficult to completely penetrate to the dead corner at the bottom of the gap, which easily leads to incomplete filling and air bubble defects. However, after the resin ink 7010 pre-fills part of the gap, the remaining filling space depth is reduced and the filling path is shortened. The high-flow-rate prepreg 420 can effectively fill the remaining space with sufficient amount of glue during pressing, achieving a good filling effect.

[0084] In addition, thin copper foil 410 and high-flow prepreg 420 are both commonly used materials in PCB manufacturing. Compared with RCC board 4010, they have lower material costs and wider supply channels, making them easier to promote and apply in industrial production, thus reducing manufacturing costs while ensuring filling quality.

[0085] To further illustrate the technical effects of this embodiment, a comparison is made between the vacuum resin plugging method in the prior art and the RCC 4010 board lamination and glue filling method in this embodiment in terms of filling effect between copper blocks. The results are listed in the table below:

[0086] As shown in the table above, compared with the existing vacuum plugging resin solution, this embodiment 1 uses semi-cured resin of RCC plate 4010 without glass fiber for pressing and filling, which has a significant advantage in filling narrow gaps due to its excellent fluidity; this embodiment 2 adds a resin ink 7010 pre-filling and vacuum degassing process before RCC plate 4010 pressing and filling, which further eliminates filling dead corners and bubble defects, realizes complete and dense filling of the gap between the copper block and the tank, and significantly enhances the embedding bonding force of the copper block.

[0087] Please see Figure 12 ; Figure 12 This is a micro-slice image of the cross-sectional structure of the circuit board according to an embodiment of the present invention.

[0088] This embodiment also provides a circuit board 90, which is manufactured using the above-described method.

[0089] Please see Figure 13 , Figure 14 , Figure 15 and Figure 16 ; Figure 13 Thermal management imaging inspection diagram of existing through-hole thermal conductive circuit boards; Figure 14 for Figure 13 A magnified view of a portion of the image; Figure 15 Thermal management imaging inspection image of an embedded copper block circuit board fabricated for this embodiment; Figure 16 for Figure 15 A magnified view of a portion of the image.

[0090] To verify the thermal conductivity of the embedded copper block circuit board prepared in this embodiment, both a prior art through-hole thermally conductive circuit board and the embedded copper block circuit board of this embodiment were fabricated, and thermal management imaging tests were performed under the same conditions. The test conditions were: ambient temperature 30°C, still air with no wind, heating power 1W, and an infrared thermal imager was used to record the temperature distribution on the board surface. The test results are compared in the table below:

[0091] The test results above show that, compared to traditional via-type thermally conductive circuit boards, the highest temperature of the copper-embedded circuit board prepared in this embodiment decreased from 104.4℃ to 81.6℃, a reduction of 22.8℃; the surface temperature difference decreased from 37.3℃ to 9.4℃, a reduction of 27.9℃. Meanwhile, the heat of the via-type thermally conductive circuit board is significantly concentrated in the area directly below the heat-generating element, resulting in a large surface temperature gradient; whereas the surface temperature distribution of the copper-embedded circuit board is more uniform, the hot spot area is significantly reduced, and there is no obvious localized high-temperature concentration.

[0092] The above results show that the embedded copper block circuit board prepared by this embodiment has a significant advantage in thermal conductivity compared with the traditional via thermal conductivity solution, and can effectively meet the thermal management requirements of thin, high power density electronic products.

[0093] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made using the description and drawings of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for manufacturing an embedded copper block circuit board for a high-efficiency thermal management module, characterized in that, The circuit board is manufactured according to the design data, and the manufacturing method includes the following steps: S10: Take copper foil and single-sided adhesive film, attach the copper foil to the surface of the single-sided adhesive film, and then perform the first pattern transfer and browning in sequence. The copper foil forms several first copper blocks, and the whole forms a browned copper block adhesive film. S20: Take out the release film and make a first window corresponding to the edge position of several first copper blocks to form a windowed release film; S30: Fabricate a core board according to the design data, and the core board has a first groove corresponding to the copper block; S40: Take the RCC board, stack the RCC board, the windowed release film, the core board, and the copper-coated adhesive film in sequence to form a stacked structure, then press them together to form a press board, then remove the single-sided adhesive film, the RCC board, and the windowed release film in sequence, and then process them in subsequent processes to form the circuit board. The first copper block faces the core plate.

2. The manufacturing method as described in claim 1, characterized in that, The method for manufacturing the first copper block includes: Take a copper foil, which is divided into a first side and a second side. Take a first dry film and attach the first dry film to the first side and the second side of the copper foil. Expose the entire surface of the first dry film on the first side; A first dry film pattern is made on the pattern of the second side corresponding to the first copper block, and then the first dry film on the first side and the second side is removed by the first etching. Then, a second single-sided adhesive film is attached to the second side, and a second dry film is taken and attached to the first side. The second dry film pattern is formed corresponding to the pattern of the first copper block. Then, a second etching is performed, and then the second dry film pattern is removed. After that, browning is performed to form several of the first copper blocks.

3. The manufacturing method as described in claim 2, characterized in that, The thickness of the first etching is 1 / 3 to 2 / 5 of the thickness of the copper foil.

4. The manufacturing method as described in claim 1, characterized in that, The pressing time is 1.5 to 2.5 hours, the heating rate is 1.4°C / min to 1.8°C / min, and the temperature is maintained at the highest temperature range for 30 minutes or more.

5. The manufacturing method as described in claim 1, characterized in that, The stacked structure includes: A first release film and a first steel plate are sequentially disposed outward from one side of the RCC plate; A second release film and a second steel plate are sequentially disposed outward from one side of the copper-coated block adhesive film.

6. The manufacturing method as described in claim 1, characterized in that, The pressing process includes aligning and stacking the core board and the copper-coated film before stacking, then cold pressing to form a cold-pressed plate, filling the edges of several first copper blocks in the cold-pressed plate with resin ink, and then baking to form a resin core board. The stacked structure is formed by sequentially stacking the RCC board, the windowed release film, and the resin core board.

7. The manufacturing method as described in claim 6, characterized in that, The cold pressing is performed at a temperature of 20°C to 30°C, using a pressure of 4.0 MPa to 5.0 MPa, with a pressing time of 10 to 15 seconds.

8. The manufacturing method as described in claim 6, characterized in that, The thickness of the resin ink filling the tank is 3 / 5 to 2 / 3 of the depth of the first tank.

9. The manufacturing method as described in claim 1, characterized in that, The RCC board is replaced by a laminated structure of thin copper foil and high-flow adhesive prepreg; In the stacked structure, the high-flow adhesive semi-cured sheet faces the windowed release film.

10. A circuit board, characterized in that, The circuit board is manufactured using the manufacturing method described in any one of claims 1 to 9.

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