A circuit board and its manufacturing process

Abstract

The present invention provides a circuit board and a preparation process thereof, the preparation process comprising the following steps: (1) after etching a first middle portion and a second middle portion respectively, pressing a top plate and the first middle portion into a first composite layer plate, and pressing a bottom plate and the second middle portion into a second composite layer plate; (2) after performing a first drilling process on the first composite layer plate and the second composite layer plate respectively to form a blind hole, respectively performing copper deposition, electroplating, etching and gold plating processes, stacking and pressing the first composite layer plate and the second composite layer plate to obtain a composite circuit board; (3) performing drilling, copper deposition, electroplating and etching processes on the composite circuit board to obtain a semi-finished circuit board, and performing pattern electroplating, alkaline etching, chemical nickel-gold and molding processes on the semi-finished circuit board to obtain a finished circuit board; wherein, after etching in step (1), the expansion and contraction pre-release coefficients of the top plate, the bottom plate, the first middle portion and the second middle portion are 1.0008 to 1.0010.

Description

Technical Field

[0001] The invention belongs to the technical field of PCB processing and relates to a circuit board and a preparation process thereof. Background Art

[0002] With the continuous development of electronic information, various electronic products tend to be miniaturized, integrated, high-frequency and high-speed, which puts forward higher requirements for printed circuit boards, requiring higher integration density, smaller line width and line spacing, higher layers and board thickness. Buried blind boards are widely used because they can improve the wiring density of circuit boards, have good thermal conductivity, and make high-speed signals have higher anti-interference ability.

[0003] Device holes are holes used for welding and fixing plug-in electronic components and connectors. They are usually metallized holes. Designing device holes as blind holes can increase the number of welded components and improve the integration density. Blind slots on printed circuit boards (PCB boards) are generally used to weld components and use blind slots for welding or fixing products. Therefore, there are strict requirements on the size, depth and shape of blind slots.

[0004] CN118973142A discloses a method for making a special metallized trapezoidal blind groove of a PCB, which includes the following steps: Step 1, providing a board, on which a plurality of spaced copper layers are arranged; Step 2, slotting, a groove is opened downward on the top copper layer; Step 3, copper deposition, a copper deposition layer is formed on the outer surface of the top copper layer and the side wall and bottom of the groove; Step 4, dry film pressing, a film layer is pressed on the outer side of the copper deposition layer; Step 5, exposure; Step 6, development; removing the film layer outside the exposure area, forming a bump in the exposure area. Step 7, electroplating copper on the outer surface of the top copper layer and the gap area to form an electroplated layer; Step 8, film stripping; forming a blind groove in the middle of the electroplated layer; Step 9, micro-etching.

[0005] CN118555763A discloses a method for electroplating blind holes with high dielectric thickness and large aperture, which forms a blind hole plate by preparing a blind hole structure to be electroplated on the surface of the plate; placing the blind hole plate in an electroplating tank to perform an electroplating operation, wherein the electroplating operation strategy includes electroplating hole filling, current regulation and electroplating monitoring, and the electroplating hole filling is used for filling the blind holes of the blind hole plate.

[0006] Controlling the amount of glue overflow and hole shape of the blind slot is a difficult point in processing. The above solution is prone to problems such as stepped holes, residual glue at the bottom of the slot, and slot hole deformation during the manufacturing process. Summary of the invention

[0007] The object of the present invention is to provide a circuit board and a preparation process thereof. The preparation process of the present invention can reduce the impact of the expansion and contraction changes caused by the circuit board during the processing, greatly reduce the alignment deviation caused by the problem of pattern or hole misalignment, and the amount of glue overflow in the blind hole of the obtained circuit board is small, which does not affect the subsequent welding and other operations on the circuit board.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a process for preparing a circuit board, the process comprising the following steps:

[0010] (1) After first etching the first middle portion and the second middle portion respectively, the top plate and the first middle portion are pressed into a first composite layer plate, and the bottom plate and the second middle portion are pressed into a second composite layer plate;

[0011] (2) performing a first drilling process on the first composite layer board and the second composite layer board to form a blind hole, performing a first copper plating process, a first electroplating process, a second etching process and a gold plating process on the first composite layer board and the second composite layer board, respectively, and stacking and pressing the first composite layer board and the second composite layer board to obtain a composite circuit board, wherein the first middle portion of the first composite layer board faces the second middle portion of the second composite layer board;

[0012] (3) performing a second drilling, a second copper deposition, a second electroplating, and a third etching process on the composite circuit board to obtain a semi-finished circuit board, and performing pattern electroplating, chemical nickel-gold and molding processes on the semi-finished circuit board to obtain a finished circuit board;

[0013] Among them, after the first etching in step (1), the expansion and contraction pre-release coefficients of the top plate, the bottom plate, the first middle part and the second middle part are 1.0008 to 1.0010, for example: 1.0008, 1.00085, 1.0009, 1.00095 or 1.0010, etc., not limited to the listed values, other values ​​not listed within the numerical range are also applicable.

[0014] In the present invention, the first etching, the second etching and the third etching are independently single-sided etching, and the first copper deposition, the second copper deposition, the first electroplating and the second electroplating are double-sided copper deposition and double-sided electroplating at the same time.

[0015] The present invention adopts a two-step pressing method, pre-etches each layer of the board with a suitable expansion and contraction pre-release coefficient, and then combines and presses them to form a composite layer. Then, blind holes are drilled on the composite layer, and the blind holes are protected by gold plating. This can improve the structural stability of the slot hole and avoid problems such as stepped holes and slot hole deformation.

[0016] Preferably, in step (1), the first etching is followed by acid etching.

[0017] Preferably, the acid etching agent of the acid etching treatment includes sulfuric acid and / or hydrochloric acid.

[0018] Preferably, before the pressing in step (1), the top plate, the bottom plate, the first middle part and the second middle part are subjected to automatic optical inspection (AOI), rivet hole punching and browning treatment respectively, and the top plate and the first middle part, and the bottom plate and the second middle part are riveted respectively.

[0019] The present invention uses a riveting method of punching rivet holes to press the layers of boards together respectively, thereby avoiding deviation between the layers of boards.

[0020] Preferably, in step (1), the first middle part and the second middle part independently include at least one layer of plywood.

[0021] Preferably, before the lamination in step (1), adhesive layers are respectively arranged between the top layer board and the first middle part, and between the bottom layer board and the second middle part.

[0022] Preferably, the material of the bonding layer includes ethyl cyanoacrylate (PP).

[0023] Preferably, in step (2), before the first drilling process, the first composite layer plate and the second composite layer plate are pressed and milled respectively.

[0024] Preferably, in step (2), tin plating, back drilling and tin stripping are performed after the first electroplating.

[0025] Preferably, in step (2), the second etching is followed by acid etching.

[0026] Preferably, the acid etching agent of the acid etching treatment includes sulfuric acid and / or hydrochloric acid.

[0027] Preferably, before the gold plating in step (2), the first composite layer plate and the second composite layer plate are subjected to automatic optical inspection respectively.

[0028] Preferably, the gold plating treatment in step (2) includes applying films to both side surfaces of the first composite layer board and the second composite layer board and then performing gold plating in the blind holes of the first composite layer board and the second composite layer board.

[0029] Preferably, after the gold plating in step (2), the first composite layer plate and the second composite layer plate are subjected to film stripping, rivet hole punching, browning and milling.

[0030] Preferably, in step (2), after a bare plate is arranged between the first composite layer plate and the second composite layer plate, they are riveted and pressed together.

[0031] In the present invention, after the first composite layer plate and the second composite layer plate are processed with rivet holes in advance, the displacement between the layers can be greatly reduced by riveting.

[0032] Preferably, a bonding layer is provided between the first composite layer and the second composite layer before the lamination in step (2).

[0033] Preferably, before the lamination in step (2), window opening treatment is performed at the blind holes on the first composite layer and the second composite layer.

[0034] The window opening process of the present invention outputs PP window opening data according to the expansion and contraction of the composite board, and then uses a laser forming machine for milling.

[0035] Preferably, the bonding layer comprises PP and low-flow adhesive PP, wherein the low-flow adhesive PP is arranged above the blind hole.

[0036] Before laminating the first composite layer and the second composite layer, the present invention changes the PP above the blind hole into a low-glue PP, performs a window opening process, and uses a bare plate as a dummy layer to reduce the amount of glue flow.

[0037] Preferably, the interlayer offset after lamination in step (2) is 0 μm to 50 μm, for example: 0 μm, 1 μm, 5 μm, 10 μm, 20 μm or 50 μm, etc., and is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] Preferably, the expansion / shrinkage pre-release coefficient of the composite circuit board in step (2) is 0.9997 to 1.0003, for example: 0.9997, 0.9998, 0.9999, 1, 1.0001, 1.0002 or 1.0003, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, in step (3), the copper thickness of the hole wall obtained by the second electroplating is 25 μm to 50 μm, for example, 20 μm, 25 μm, 30 μm, 40 μm or 50 μm, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the pattern electroplating in step (3) includes plating an anti-corrosion layer on the top layer of the semi-finished circuit board.

[0041] Preferably, the material of the anti-corrosion layer includes tin.

[0042] Preferably, in step (3), the pattern is electroplated and then alkali etched.

[0043] Preferably, the alkaline etching agent of the alkaline etching comprises a sodium hydroxide solution.

[0044] Preferably, the gold thickness formed by the chemical nickel gold in step (3) is 0.05 μm to 0.1 μm, for example: 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm or 0.1 μm, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] Preferably, the nickel thickness of the chemical nickel gold in step (3) is 3 μm to 5 μm, for example, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] In a second aspect, the invention provides a circuit board, which is manufactured by the manufacturing process described in the first aspect.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The preparation process of the present invention can reduce the impact of the expansion and contraction changes caused by the circuit board during the processing, and greatly reduce the alignment deviation caused by the problem of pattern or hole misalignment. The amount of glue overflow in the blind hole of the obtained circuit board is small, and it does not affect the subsequent welding and other operations of the circuit board.

[0049] (2) The longitudinal overflow height of the holes of the circuit board produced by the process of the present invention can be controlled within 0.3 mm, and the final expansion coefficient is within ±0.0001. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0051] The model of the PP used in the present invention is TU-87P SLK, and the model of the low-flow PP is VT-901LF.

[0052] Example 1

[0053] This embodiment provides a circuit board, which is manufactured by the following manufacturing process:

[0054] (1) The top plate (L1), the first middle part (including L2-L15), the second middle part (including L16-L23) and the bottom plate (L24) are etched to form a pattern according to the expansion and contraction pre-release coefficient of 1.0008, and then acid-etched with hydrochloric acid with a mass concentration of 10%. After AOI inspection of each layer of the plate, rivet holes and browning treatment are performed respectively. A PP adhesive layer is set between the top plate (L1) and each layer of the first middle part (including L2-L15), and after riveting, the plates are stacked and pressed to form a first composite layer. A PP adhesive layer is set between the bottom plate (L1) and each layer of the second middle part (including L16-L23), and after riveting, the plates are stacked and pressed to form a second composite layer.

[0055] (2) After laminating and milling the first composite board and the second composite board, the first composite layer board and the second composite layer board are drilled to form blind holes, and the first composite layer board and the second composite layer board are copper plated on the surface, and then the whole board is electroplated, tinned, back-drilled and tin-removed, and further etched to form a pattern. Then, hydrochloric acid with a mass concentration of 10% is used for acid etching. After AOI inspection of each layer board, after the surface of the first composite layer board and the second composite layer board is filmed, a layer of hard gold with a thickness of ≥3μm is plated in the blind hole, and the film is removed after gold plating. After film removal, the first composite layer and the second composite layer are respectively subjected to rivet holes and browning treatment, a PP bonding layer and a dummy layer (bright plate) are arranged between the first composite layer and the second composite layer, and PP milling treatment is performed on the blind hole, and the PP bonding layer on the blind hole is replaced with a low-flow glue PP, and a composite circuit board is obtained after lamination, wherein the interlayer offset of the composite circuit board is 5 μm, the expansion and contraction coefficient is 1.0000, and the longitudinal overflow height in the hole is ≤0.3 mm;

[0056] (3) After drilling holes in the composite circuit board with a new knife, copper is deposited by copper deposition, flash plating, and copper deposition again, and then the entire board is electroplated. The copper in the hole wall meets the military product hole copper requirement of ≥25μm. The composite circuit board is etched to form the outer layer graphic data, and then tin is plated on its surface to form an anti-corrosion layer. After alkaline etching treatment with 50g / L sodium hydroxide solution, the gold thickness of the composite circuit board is 0.08μm and the nickel thickness is 4μm after chemical nickel-gold treatment. After flying probe testing, the molding process is carried out, and the assembled product is milled into a finished circuit board. The expansion and contraction coefficient is tested again to be 0.9999.

[0057] Example 2

[0058] This embodiment provides a circuit board, which is manufactured by the following manufacturing process:

[0059] (1) The top plate (L1), the first middle part (including L2-L15), the second middle part (including L16-L23) and the bottom plate (L24) are etched to form a pattern according to the expansion and contraction pre-release coefficient of 1.0010, and then acid-etched with hydrochloric acid with a mass concentration of 10%. After AOI inspection of each layer of the plate, rivet holes and browning treatment are performed respectively. A PP adhesive layer is set between the top plate (L1) and each layer of the first middle part (including L2-L15), and after riveting, the plates are stacked and pressed to form a first composite layer. A PP adhesive layer is set between the bottom plate (L1) and each layer of the second middle part (including L16-L23), and after riveting, the plates are stacked and pressed to form a second composite layer.

[0060] (2) After laminating and milling the first composite board and the second composite board, the first composite layer board and the second composite layer board are drilled to form blind holes, and the first composite layer board and the second composite layer board are copper plated on the surface, and then the whole board is electroplated, tinned, back-drilled and tin-removed, and further etched to form a pattern. Then, hydrochloric acid with a mass concentration of 10% is used for acid etching. After AOI inspection of each layer board, after the surface of the first composite layer board and the second composite layer board is filmed, a layer of hard gold with a thickness of ≥3μm is plated in the blind hole, and the film is removed after gold plating. After film removal, the first composite layer and the second composite layer are respectively subjected to rivet holes and browning treatment, a PP bonding layer and a dummy layer (bright plate) are arranged between the first composite layer and the second composite layer, and PP milling treatment is performed on the blind hole, and the PP bonding layer on the blind hole is replaced with a low-flow glue PP, and a composite circuit board is obtained after lamination, wherein the interlayer offset of the composite circuit board is 10 μm, the expansion and contraction coefficient is 1.0002, and the longitudinal overflow height in the hole is ≤0.3 mm;

[0061] (3) After drilling holes in the composite circuit board with a new knife, copper is deposited by copper deposition, flash plating, and copper deposition again, and then the entire board is electroplated. The copper in the hole wall meets the military product hole copper requirement of ≥25μm. The composite circuit board is etched to form the outer layer graphic data, and then tin is plated on its surface to form an anti-corrosion layer. After alkaline etching treatment with 50g / L sodium hydroxide solution, the gold thickness of the composite circuit board is 0.05μm and the nickel thickness is 3μm after chemical nickel-gold treatment. After flying probe testing, the molding process is carried out, and the assembled product is milled into a finished circuit board. The expansion and contraction coefficient is tested again and is 1.0001.

[0062] Example 3

[0063] This embodiment provides a circuit board, which is manufactured by the following manufacturing process:

[0064] (1) The top plate (L1), the first middle part (including L2-L15), the second middle part (including L16-L23) and the bottom plate (L24) are etched to form a pattern according to the expansion and contraction pre-release coefficient of 1.0009, and then acid-etched with hydrochloric acid with a mass concentration of 10%. After AOI inspection of each layer of the plate, rivet holes and browning treatment are performed respectively. A PP adhesive layer is set between the top plate (L1) and each layer of the first middle part (including L2-L15), and after riveting, the plates are stacked and pressed to form a first composite layer. A PP adhesive layer is set between the bottom plate (L1) and each layer of the second middle part (including L16-L23), and after riveting, the plates are stacked and pressed to form a second composite layer.

[0065] (2) After laminating and milling the first composite board and the second composite board, the first composite layer board and the second composite layer board are drilled to form blind holes, and the first composite layer board and the second composite layer board are copper plated on the surface, and then the whole board is electroplated, tinned, back-drilled and tin-removed, and further etched to form a pattern. Then, hydrochloric acid with a mass concentration of 10% is used for acid etching. After AOI inspection of each layer board, after the surface of the first composite layer board and the second composite layer board is filmed, a layer of hard gold with a thickness of ≥3μm is plated in the blind hole, and the film is removed after gold plating. After film removal, the first composite layer and the second composite layer are respectively subjected to rivet holes and browning treatment, a PP bonding layer and a dummy layer (bright plate) are arranged between the first composite layer and the second composite layer, and PP milling treatment is performed on the blind hole, and the PP bonding layer on the blind hole is replaced with a low-flow glue PP, and a composite circuit board is obtained after lamination, wherein the interlayer offset of the composite circuit board is 2 μm, the expansion and contraction coefficient is 1.0001, and the longitudinal overflow height in the hole is ≤0.3 mm;

[0066] (3) After drilling holes in the composite circuit board with a new knife, copper is deposited by copper deposition, flash plating, and copper deposition again, and then the entire board is electroplated. The copper in the hole wall meets the military product hole copper requirement of ≥25μm. The composite circuit board is etched to form the outer layer graphic data, and then tin is plated on its surface to form an anti-corrosion layer. After alkaline etching treatment with 50g / L sodium hydroxide solution, the gold thickness of the composite circuit board is 0.1μm and the nickel thickness is 5μm after chemical nickel-gold treatment. After flying probe testing, the molding process is carried out, and the assembled product is milled into a finished circuit board. The expansion and contraction coefficient is tested again to be 1.0000.

[0067] Example 4

[0068] The only difference between this embodiment and embodiment 1 is that a PP adhesive layer is used on the blind hole in step (2) and low-flow glue PP is not replaced. Other conditions and parameters are exactly the same as those in embodiment 1. The expansion and contraction coefficient is 0.9999, and the longitudinal overflow height in the hole is ≤1.5 mm.

[0069] Example 5

[0070] The only difference between this embodiment and embodiment 1 is that no dummy layer is provided in step (2), and other conditions and parameters are exactly the same as those in embodiment 1, the expansion and contraction coefficient is 0.9999, and the longitudinal overflow height in the hole is ≤0.5 mm.

[0071] Comparative Example 1

[0072] The only difference between this comparative example and Example 1 is that after the first etching, the expansion and contraction pre-release coefficients of the first middle portion and the second middle portion are controlled to be 1.0005, and other conditions and parameters are exactly the same as those in Example 1. The expansion and contraction coefficient of the finished circuit board is 0.9995, and the longitudinal overflow height in the hole is ≤0.3 mm.

[0073] Comparative Example 2

[0074] The only difference between this comparative example and Example 1 is that after the first etching, the expansion and contraction pre-release coefficients of the top plate, the bottom plate, the first middle portion and the second middle portion are controlled to be 1.0015, and the other conditions and parameters are exactly the same as those in Example 1. The expansion and contraction coefficient of the finished circuit board is 1.0006, and the longitudinal overflow height in the hole is ≤0.3 mm.

[0075] It can be seen from Table 1 that according to Examples 1-3, the longitudinal overflow height of the holes of the circuit board produced by the process of the present invention can be controlled within 0.3 mm, and the final expansion coefficient is within ±0.0001.

[0076] By comparing Example 1 and Example 4, it can be seen that before laminating the first composite layer and the second composite layer, the present invention changes the PP above the blind hole into a low-flow PP, performs a window opening process, and uses a bare board as a fake layer to reduce the amount of glue overflow.

[0077] By comparing Example 1 with Example 5, it can be seen that the present invention uses a dummy layer as an intermediate isolation layer, which can prevent the holes in the upper and lower parts from being filled with glue in the opposite part.

[0078] By comparing Example 1 and Comparative Examples 1-2, it can be seen that in the preparation process of the circuit board described in the present invention, the expansion and shrinkage pre-release coefficients of the top board, the bottom board, the first middle part and the second middle part set by the first etching will affect its performance. The expansion and shrinkage pre-release coefficient is set to 1.0008-1.0010, and the performance of the obtained circuit board is better. If the expansion and shrinkage pre-release coefficient is set too high, the expansion and shrinkage of the finished circuit board will be too high. If the expansion and shrinkage pre-release coefficient is set too low, the expansion and shrinkage of the finished circuit board will be too low. Excessive or low expansion and shrinkage will affect the insertion or mounting of components.

[0079] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A process for preparing a circuit board, characterized in that: The preparation process comprises the following steps: (1) After first etching the first middle portion and the second middle portion respectively, the top plate and the first middle portion are pressed into a first composite layer plate, and the bottom plate and the second middle portion are pressed into a second composite layer plate; (2) performing a first drilling process on the first composite layer board and the second composite layer board to form a blind hole, performing a first copper plating process, a first electroplating process, a second etching process and a gold plating process on the first composite layer board and the second composite layer board, respectively, and stacking and pressing the first composite layer board and the second composite layer board to obtain a composite circuit board, wherein the first middle portion of the first composite layer board faces the second middle portion of the second composite layer board; (3) performing a second drilling, a second copper deposition, a second electroplating, and a third etching process on the composite circuit board to obtain a semi-finished circuit board, and performing pattern electroplating, chemical nickel-gold and molding processes on the semi-finished circuit board to obtain a finished circuit board; Among them, after the first etching in step (1), the expansion and contraction pre-expansion coefficients of the top plate, the bottom plate, the first middle part and the second middle part are 1.0008 to 1.0010.

2. The preparation process according to claim 1, characterized in that: Step (1) performing acid etching after the first etching; Preferably, the acid etching agent of the acid etching treatment includes sulfuric acid and / or hydrochloric acid.

3. The preparation process according to claim 1 or 2, characterized in that: Before the pressing in step (1), the top plate, the bottom plate, the first middle portion and the second middle portion are respectively subjected to automatic optical inspection, rivet hole punching and browning treatment, and the top plate and the first middle portion, and the bottom plate and the second middle portion are respectively riveted; Preferably, in step (1), the first middle portion and the second middle portion independently include at least one layer of laminate; Preferably, before the lamination in step (1), adhesive layers are respectively provided between the top plate and the first middle portion, and between the bottom plate and the second middle portion; Preferably, the material of the adhesive layer includes PP.

4. The preparation process according to any one of claims 1 to 3, characterized in that: Step (2) before the first drilling process, the first composite layer plate and the second composite layer plate are pressed and milled respectively; Preferably, in step (2), tin plating, back drilling and tin stripping are performed after the first electroplating; Preferably, in step (2), the second etching is followed by acid etching; Preferably, the acid etching agent of the acid etching treatment includes sulfuric acid and / or hydrochloric acid.

5. The preparation process according to any one of claims 1 to 4, characterized in that: Before the gold plating process in step (2), the first composite layer plate and the second composite layer plate are respectively subjected to automatic optical inspection process; Preferably, the gold plating treatment in step (2) includes plating gold in the blind holes of the first composite layer board and the second composite layer board after laminating the surfaces of both sides of the first composite layer board and the second composite layer board; Preferably, after the gold plating in step (2), the first composite layer plate and the second composite layer plate are subjected to film stripping, rivet hole punching, browning and milling.

6. The preparation process according to any one of claims 1 to 5, characterized in that: Step (2) after arranging a bare plate between the first composite layer plate and the second composite layer plate, riveting and pressing them together; Preferably, a bonding layer is provided between the first composite layer and the second composite layer before lamination in step (2); Preferably, before the lamination in step (2), window opening treatment is performed at the blind holes on the first composite layer and the second composite layer; Preferably, the bonding layer comprises PP and low-flow adhesive PP, wherein the low-flow adhesive PP is arranged above the blind hole; Preferably, the interlayer offset after lamination in step (2) is 0 μm to 50 μm; Preferably, the expansion / contraction pre-release coefficient of the composite circuit board in step (2) is 0.9997 to 1.0003.

7. The preparation process according to any one of claims 1 to 6, characterized in that: Step (3) The copper thickness of the hole wall obtained by the second electroplating is 25 μm to 50 μm.

8. The preparation process according to any one of claims 1 to 7, characterized in that: The pattern electroplating in step (3) includes plating an anti-corrosion layer on the top layer of the semi-finished circuit board; Preferably, the material of the anti-corrosion layer includes tin; Preferably, in step (3), the pattern is electroplated and then alkali etched; Preferably, the alkaline etching agent of the alkaline etching comprises a sodium hydroxide solution.

9. The preparation process according to any one of claims 1 to 8, characterized in that: The thickness of gold formed by the chemical nickel-gold in step (3) is 0.05 μm to 0.1 μm; Preferably, the nickel thickness of the chemical nickel-gold in step (3) is 3 μm to 5 μm.

10. A circuit board, characterized in that: The circuit board is manufactured by the manufacturing process according to any one of claims 1 to 9.