A semi-buried metal-based step groove PCB and a processing method thereof

Abstract

This invention discloses a semi-embedded metal-based stepped groove PCB and its processing method. The method includes milling grooves into a core board and a prepreg, embedding them into a metal substrate, and then laminating them to form a PCB sub-board. Electroplating is then used to make the copper layer conductive with the metal substrate and to fabricate the inner layer circuitry. Next, the outer core board is laminated to form a complete PCB structure. Laser processing is used to expose the upper surface of the metal substrate, which is then cleaned and coated to obtain the finished product. This processing method can form a stepped groove structure with a metal substrate at the bottom on the PCB surface. This stepped groove can be used for chip mounting, allowing chips to be directly mounted on the metal substrate surface, thereby shortening the heat conduction path between the chip and the heat dissipation metal and improving the overall heat dissipation performance of the PCB. Simultaneously, because the stepped groove is formed by laser processing, its bottom has a high flatness, which is beneficial for improving the mounting flatness after chip mounting.

Description

Technical Field

[0001] This invention relates to the field of metal-based heat dissipation PCB processing technology, and in particular to a semi-embedded metal-based stepped groove PCB and its processing method. Background Technology

[0002] As the core carrier of electronic components, the heat dissipation performance and assembly precision of PCBs have become key factors restricting the performance improvement of high-end electronic products. With the widespread use of high-power, highly integrated chips, the heat generation per unit area has increased significantly, placing higher demands on the heat dissipation capacity and mounting plane precision of PCBs.

[0003] Currently, the industry commonly uses the method of embedding a metal substrate inside the PCB to enhance heat dissipation. Typically, the metal substrate is directly conductive to the PCB surface. After the metal substrate is laminated to the board, deep milling is generally used to mill and recess the area above the metal substrate to create space for chip mounting. However, due to the precision limitations of traditional controlled-depth milling equipment, the surface flatness of the metal substrate after milling is poor, resulting in insufficient consistency in the depth of the stepped grooves. This directly affects the levelness and tightness of the chip after mounting, leading to reduced heat dissipation efficiency between the chip and the metal substrate. It also reduces assembly reliability, making it difficult to meet the dual requirements of high-precision assembly and efficient heat dissipation for high-end chips. Summary of the Invention

[0004] This invention provides a semi-embedded metal-based stepped groove PCB and its processing method, which partially solves or alleviates the above-mentioned deficiencies in the prior art.

[0005] Firstly, the technical solution proposed by this invention is as follows:

[0006] A PCB manufacturing method, characterized by comprising:

[0007] The core board and prepreg of the corresponding layer of the metal-based semi-embedded structure are milled.

[0008] The metal base is embedded in the core board after milling, and pressed together with the prepreg, so that the prepreg flows adhesive under heating and pressure, thereby bonding the core board and the metal base together to form a PCB sub-board.

[0009] The PCB sub-board is electroplated to form a conductive structure between the PCB copper layer and the metal substrate, and an inner layer circuit pattern is fabricated.

[0010] After electroplating and inner layer circuit pattern fabrication are completed, the outer core board is laminated onto the PCB sub-board to form a complete PCB structure.

[0011] The PCB structure is laser-processed to remove the material above the metal substrate, exposing the upper surface of the metal substrate;

[0012] The exposed metal substrate surface is cleaned to remove residual adhesive residue and drilling contaminants, so that the copper layer surface is clean.

[0013] The upper surface of the metal substrate with exposed clean copper layer is coated to form a semi-embedded metal substrate stepped groove PCB.

[0014] In the PCB processing method, the size of the milled groove is 0.1-0.2 mm larger than the size of one side of the metal base.

[0015] The PCB processing method wherein the PCB comprises eight copper layers, and the metal substrate is disposed between the third to the eighth copper layers.

[0016] In the PCB processing method, the laser processing is performed using a laser drilling machine. The laser processing is used to remove the dielectric layer above the metal substrate, so that the upper surface of the metal substrate and the PCB surface form a stepped groove.

[0017] In the PCB processing method, the bottom of the stepped groove is an exposed metal base surface, and the sidewalls of the stepped groove are formed by laser ablation.

[0018] In the PCB fabrication method, the stepped groove is used for chip mounting.

[0019] In the PCB processing method, the surface cleaning treatment is carried out using potassium permanganate solution to remove residual adhesive residue and drilling sludge.

[0020] In the PCB processing method, the surface coating treatment is performed by chemical deposition or displacement deposition.

[0021] In the PCB processing method, the metal substrate is electrically connected to at least one copper layer of the PCB through an electroplated conductive structure.

[0022] Secondly, the present invention also proposes a semi-buried metal-based stepped groove PCB, which is a PCB processed by any of the PCB processing methods described above.

[0023] The beneficial effects of this invention are as follows:

[0024] This processing method can form a stepped groove structure with a metal base on the PCB surface. This stepped groove can be used for chip mounting, allowing the chip to be directly mounted on the metal base surface, thereby shortening the heat conduction path between the chip and the heat dissipation metal and improving the overall heat dissipation performance of the PCB. At the same time, since the stepped groove is formed by laser processing, its bottom has a high degree of flatness, which helps to improve the mounting flatness of the chip. Attached Figure Description

[0025] Figure 1 This is a flowchart of a PCB manufacturing method provided for some embodiments of the present invention.

[0026] Figure 2 This is a schematic diagram of the structure of the core board a and the prepreg a provided in some embodiments of the present invention.

[0027] Figure 3 This is a schematic diagram of the structure of the core board a and the prepreg a after milling grooves, as provided in some embodiments of the present invention.

[0028] Figure 4 This is a schematic diagram showing the relative positions of the metal base and the milled groove according to some embodiments of the present invention.

[0029] Figure 5 This is a schematic diagram of the assembly of the metal substrate and the core board a according to some embodiments of the present invention.

[0030] Figure 6 This is a schematic diagram of the structure of core board a after electroplating, provided in some embodiments of the present invention.

[0031] Figure 7 This is a schematic diagram illustrating the fabrication of the core board a and the electroplated layer according to some embodiments of the present invention.

[0032] Figure 8 This is a plan view of a complete PCB structure provided for some embodiments of the present invention.

[0033] Figure 9 The diagram shows the complete PCB structure after laser processing, as provided in some embodiments of the present invention.

[0034] Component names and serial numbers in the diagram:

[0035] 1. Core board a; 11. Insulating substrate layer; 12. Copper foil layer; 2. Prepreg a; 3. Metal base; 4. Electroplating layer; 5. Groove; 6. Core board b; 7. Prepreg b; 8. Step groove. Detailed Implementation

[0036] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0037] Example

[0038] like Figure 1As shown, the present invention provides a processing method for a semi-embedded metal-based stepped groove PCB. The PCB in this embodiment is a multi-layer PCB structure, including eight copper layers and a prepreg disposed between adjacent copper layers, wherein the copper layers are arranged from top to bottom as the 1st copper layer to the 8th copper layer.

[0039] A metal base is disposed inside the PCB to enhance its heat dissipation capacity. In this embodiment, the metal base is disposed between the 3rd to 8th copper layers, so that the metal base is located in the lower region of the PCB, while the PCB still retains the 1st and 2nd copper layer structures above the metal base.

[0040] The fabrication method for this semi-embedded metal-based stepped groove PCB includes the following steps:

[0041] S1. Take the core board and prepreg of the corresponding layer of the metal-based semi-embedded structure and perform milling.

[0042] S2. Embed the metal base into the core board after milling the groove, and press it with the prepreg to make the prepreg flow under heating and pressure, thereby bonding the core board and the metal base into a PCB sub-board.

[0043] S3. Electroplating is performed on the PCB sub-board to form a conductive structure between the PCB copper layer and the metal base, and the inner layer circuit pattern is fabricated.

[0044] S4. After electroplating and inner layer circuit pattern fabrication are completed, the outer layer core board is pressed onto the PCB sub-board to form a complete PCB structure.

[0045] S5. Perform laser processing on the PCB structure to remove the material above the metal substrate, exposing the upper surface of the metal substrate;

[0046] S6. Perform surface cleaning treatment on the exposed metal base surface to remove residual adhesive residue and drilling sludge, so that the copper layer surface is clean.

[0047] S7. Apply a surface coating to the exposed clean copper layer of the metal substrate to form a semi-embedded metal substrate stepped groove PCB.

[0048] Specifically, in step S1, see Figure 2 and Figure 3 As shown, three core boards a1 and two prepreg sheets a2 are taken, and prepreg sheets a2 are set between adjacent core boards a1. The core boards a1 and prepreg sheets a2 used to form the corresponding layers of the metal-based semi-embedded structure are milled to form milled grooves.

[0049] For example, in a preferred embodiment, the milled groove is 0.1-0.2 mm larger on one side than the metal substrate to facilitate the embedding of the metal substrate and to provide filling space for the flow of adhesive in the prepreg a2 during subsequent lamination.

[0050] In this embodiment, the core board a1 is made of high-frequency microwave FR-4 substrate with a thickness of 0.2mm. In addition, the three core boards a1 are of the same specifications and are all double-sided copper-clad structures. The prepreg a2 (also known as PP sheet) uses a halogen-free flame-retardant resin system with a resin content of 65%-70% and a flowability controlled at 20-30mm / 150℃ to ensure uniform resin flow and dense filling during pressing.

[0051] In step S2, see Figure 4 and Figure 5 As shown, the metal substrate is embedded in the milled groove of the core board a1, and the metal substrate also passes through the milled groove of the prepreg a2. Then, the core board a1 and the prepreg a2 are heated and pressurized by a pressing device. Under the heating and pressurizing conditions, the prepreg flows and fills the gap between the core board a1 and the metal substrate, thereby bonding the core board a1 and the metal substrate together to form a PCB sub-board structure containing the metal substrate, so as to facilitate subsequent processes such as electroplating and outer layer lamination.

[0052] In step S3, see Figure 6 and Figure 7 As shown, the PCB sub-board is electroplated to form a conductive structure between the PCB copper layer and the metal substrate, and the inner layer circuit pattern is fabricated.

[0053] Specifically, the topmost copper layer of the PCB sub-board is the third copper layer, which is formed by combining the original copper foil layer 12 of the core board a1 with the electroplated layer 4. This design balances copper layer thickness and structural strength, meeting the current-carrying requirements of the inner layer circuits while enhancing the conductivity and adhesion with the metal substrate. When fabricating the inner layer circuit patterns using the third copper layer, interference between the conductive structure and the inner layer circuitry can be avoided. Under the premise of ensuring electrical performance, this design achieves coordinated adaptation between the metal substrate grounding and heat dissipation functions and the inner layer circuit transmission functions, thus completing the functional molding of the inner layers of the PCB sub-board.

[0054] In step S4, see Figure 8 As shown, the outer core board is laminated onto the PCB sub-board after electroplating and inner layer circuit pattern fabrication to form a complete PCB structure.

[0055] Specifically, after the inner layer circuitry of the PCB sub-board is fabricated, a prepreg (b7) and a core board (b6) are sequentially stacked on the upper surface of the PCB sub-board. The core board (b6) and the prepreg (b7) are then pressed together using a laminating device to form a complete PCB stack structure, thereby obtaining a complete PCB structure containing a metal substrate. Specifically, during the secondary lamination process, the prepreg (b7) undergoes adhesive flow under heating and pressure, filling the groove 5 area of ​​the underlying inner layer pattern and forming a tight bond with the PCB sub-board to ensure the integrity of the board structure.

[0056] It should be noted that in this embodiment, the core board a1 and core board b6, and the prepreg a2 and prepreg b7 are completely identical in material, thickness and performance, and are only marked differently for the convenience of layer sequence description.

[0057] In step S5, see Figure 9 As shown, after the PCB stack-up structure is completed, the PCB structure is laser-processed to remove the dielectric layer material located above the metal substrate, exposing the upper surface of the metal substrate. For example, in a preferred embodiment, the laser processing is performed using a laser drill. The laser processing is used to remove the dielectric layer above the metal substrate, forming a stepped groove between the upper surface of the metal substrate and the PCB surface. Specifically, the bottom of the stepped groove is the exposed metal substrate surface, while the sidewalls of the stepped groove are formed by laser ablation.

[0058] It is worth noting that the stepped groove is used for chip mounting.

[0059] Specifically, a preferred embodiment of the present invention employs a programmable laser drilling machine for processing. By adjusting the laser power, pulse frequency, spot size, and scanning path, the processing depth and range are precisely controlled, removing only the dielectric layer above the metal substrate, thereby forming a stepped groove with consistent size and depth on the PCB surface. The bottom of the stepped groove is the directly exposed metal substrate surface, exhibiting high flatness; the sidewalls of the stepped groove are formed by laser ablation, resulting in good verticality, neat edges, and no burrs or chipping.

[0060] Because the bottom of the stepped groove is a highly thermally conductive metal substrate surface, it can be directly used for chip mounting, allowing the bottom surface of the chip to fit tightly against the metal substrate, significantly shortening the heat conduction path and greatly improving heat dissipation efficiency. At the same time, the regular structure of the stepped groove can provide precise mounting positioning for the chip, improving chip assembly accuracy and reliability, making it particularly suitable for packaging precision devices with high power and high heat dissipation requirements.

[0061] In step S6, the exposed metal substrate surface is cleaned to remove residual adhesive residue and drilling sludge, making the copper layer surface clean and providing a good bonding interface for subsequent surface coating processes.

[0062] For example, a preferred embodiment is to use an alkaline potassium permanganate solution for descaling. The strong oxidizing effect of potassium permanganate efficiently decomposes and removes residual glue residue and drilling sludge without damaging the metal substrate and surrounding copper layer. After cleaning, the copper layer on the metal substrate surface is kept clean, uniform and active, effectively improving the adhesion of subsequent plating layers and the reliability of the finished product.

[0063] In step S7, the exposed clean copper layer on the upper surface of the metal substrate is finally coated to form a semi-buried metal substrate stepped groove PCB. For example, the surface coating process can be carried out by chemical deposition or displacement deposition to form a metal plating layer on the metal substrate surface, such as a chemical nickel-gold layer or a chemical nickel-palladium-gold layer, to protect the metal substrate surface and meet the requirements of chip assembly and long-term use.

[0064] For example, in some preferred embodiments, the metal base is a copper-based or aluminum-based heat dissipation metal plate, which can quickly dissipate the heat of the chip while achieving electrical conduction, greatly improving the overall heat dissipation capacity and service life of the PCB.

[0065] Through the above processing steps, a stepped groove structure with a metal base can be formed on the PCB surface. This stepped groove can be used for chip mounting, allowing the chip to be directly mounted on the metal base surface, thereby shortening the heat conduction path between the chip and the heat dissipation metal and improving the overall heat dissipation performance of the PCB. At the same time, since the stepped groove is formed by laser processing, its bottom has a high degree of flatness, which is beneficial to improving the mounting flatness of the chip after mounting.

[0066] Furthermore, such as Figure 8 and Figure 9 As shown, the PCB includes eight copper layers, with the metal substrate disposed between the 3rd to 8th copper layers.

[0067] Specifically, the first and second copper layers are located above the metal substrate and are isolated from the metal substrate by a dielectric layer. This dielectric layer includes a prepreg (b7) and a core board (b6). Relying on the substrate support of the core board (b6) and the adhesive sealing of the prepreg (b7), efficient electrical insulation can be achieved, and the overall structural strength of the board can be enhanced. Furthermore, the core board (b6), the prepreg (b7), and the inner core board (a1) and the prepreg (a2) are made of completely identical materials, ensuring that the overall thermal expansion coefficient of the PCB is consistent. This avoids defects such as warping, delamination, and cracking under high and low temperature conditions, thus improving the long-term reliability of the product.

[0068] Furthermore, such as Figure 8 and Figure 9 As shown, the metal substrate is electrically connected to at least one copper layer of the PCB through an electroplated conductive structure.

[0069] Specifically, the high heat generated by the chip can be quickly conducted to the embedded metal substrate. The metal substrate, relying on the tightly bonded electroplated conductive area (electroplated layer 4), efficiently transfers the heat to the copper layers of the PCB. By taking advantage of the overall heat dissipation of the large copper area of ​​the PCB, the heat is quickly dispersed and the local temperature rise is reduced, achieving rapid heat dissipation of the chip and the board, and preventing device failure and board deformation caused by high temperature heat accumulation.

[0070] At the same time, the electroplated conductive structure allows the metal substrate to be completely integrated into the PCB conductive network. This not only relies on the high conductivity of the metal substrate to significantly improve the overall current carrying capacity of the PCB and meet the power supply requirements of high-power devices, but also forms a stable ground reference surface, optimizes the quality of circuit signal transmission, and reduces signal interference and voltage drop loss.

[0071] like Figures 2 to 9 As shown, the present invention also provides a preferred embodiment of a semi-embedded metal-based stepped groove PCB, which is processed using the processing method described in any of the preceding claims, and has an overall eight-layer copper layer structure, with the specific structural features as follows:

[0072] The core inner layer of this PCB consists of three identical core boards a1. Each core board a1 has a symmetrical double-sided copper-clad structure, including an insulating substrate layer 11 in the middle and copper foil layers 12 tightly attached to both sides. A prepreg a2 is sandwiched between adjacent core boards a1. Matching milled grooves are opened at corresponding positions on the core board a1 and the prepreg a2, and a metal base 3 is embedded and fixed together. The metal base 3 is preferably a copper-based or aluminum-based heat dissipation metal plate. The gap between its outer wall and the milled groove wall is filled and sealed by the prepreg a2 through pressure bonding adhesive, realizing the integrated bonding of the metal base 3 and the inner core board assembly.

[0073] On the surface of the copper foil layer 12 closest to the metal substrate 3, the uppermost core board a1 has an integrally formed electroplated layer 4. This electroplated layer 4 constitutes the core part of the third copper layer of the PCB and forms a direct, low-resistance electrical connection with the upper surface of the metal substrate 3, becoming a key hub for the thermal and electrical conduction of the metal substrate 3. The electroplated layer 4 and the copper foil layer 12 connected to it are etched together to form a groove 5, which provides precise positioning and filling space for subsequent secondary lamination.

[0074] The topmost core board a1 is tightly bonded to the prepreg b7 via groove 5, and the gap between the prepreg b7 and the core board a1 is filled by pressure bonding adhesive. A core board b6 is bonded to the side of the prepreg b7 furthest from the core board a1. Core board b6 and prepreg b7 are made of the same material as the inner core board a1 and prepreg a2. Corresponding to the position of the metal substrate 3, core board b6 and prepreg b7 are laser-processed to form a stepped groove 8. The stepped groove 8 penetrates both the core board b6 and the prepreg b7, exposing the clean upper surface of the metal substrate 3 at the bottom. The sidewalls are a flat structure formed by laser ablation, precisely adapting to chip mounting, ultimately forming an integrated PCB structure with a partially embedded metal substrate and an exposed stepped groove.

[0075] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A PCB manufacturing method, characterized in that, include: The core board and prepreg of the corresponding layer of the metal-based semi-embedded structure are milled. The metal base is embedded in the core board after milling, and pressed together with the prepreg, so that the prepreg flows adhesive under heating and pressure, thereby bonding the core board and the metal base together to form a PCB sub-board. The PCB sub-board is electroplated to form a conductive structure between the PCB copper layer and the metal substrate, and an inner layer circuit pattern is fabricated. After electroplating and inner layer circuit pattern fabrication are completed, the outer core board is laminated onto the PCB sub-board to form a complete PCB structure. The PCB structure is laser-processed to remove the material above the metal substrate, exposing the upper surface of the metal substrate; The exposed metal substrate surface is cleaned to remove residual adhesive residue and drilling contaminants, so that the copper layer surface is clean. The upper surface of the metal substrate with exposed clean copper layer is coated to form a semi-embedded metal substrate stepped groove PCB.

2. The PCB processing method according to claim 1, characterized in that, The dimensions of the milled groove are 0.1-0.2 mm larger than the metal base on one side.

3. The PCB processing method according to claim 1, characterized in that, The PCB includes eight copper layers, and the metal substrate is disposed between the third to the eighth copper layers.

4. The PCB processing method according to claim 1, characterized in that, The laser processing is performed using a laser drilling machine. The laser processing is used to remove the dielectric layer above the metal substrate, so that the upper surface of the metal substrate and the PCB surface form a stepped groove.

5. The PCB processing method according to claim 4, characterized in that, The bottom of the stepped groove is an exposed metal base surface, and the sidewalls of the stepped groove are formed by laser ablation.

6. The PCB processing method according to claim 4, characterized in that, The stepped groove is used for chip mounting.

7. The PCB processing method according to claim 1, characterized in that, The surface cleaning treatment is carried out using potassium permanganate solution to remove residual glue residue and drilling sludge.

8. The PCB processing method according to claim 1, characterized in that, The surface coating process is performed using chemical deposition or displacement deposition.

9. The PCB processing method according to claim 1, characterized in that, The metal substrate is electrically connected to at least one copper layer of the PCB through an electroplated conductive structure.

10. A semi-embedded metal-based stepped groove PCB, characterized in that, It is a PCB processed using any of the PCB processing methods described in claims 1-9.

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