Multilayer printed circuit board for power circuit and preparation method

Abstract

The invention discloses a multi-layer printed circuit board for a power circuit and a preparation method, the multi-layer printed circuit board comprises at least two double-sided copper-clad plates and two single-layer copper sheets, the two double-sided copper-clad plates are stacked in the height direction, an insulating layer is arranged between the two double-sided copper-clad plates, and the two single-layer copper sheets are stacked in the height direction. Wherein one single-layer copper sheet is laminated above the upper double-sided copper-clad plate, the other single-layer copper sheet is laminated below the lower double-sided copper-clad plate, an insulating layer is arranged between each single-layer copper sheet and the corresponding double-sided copper-clad plate, and an anti-welding layer is arranged on the outer side of each single-layer copper sheet. Through a composite insulation structure design, FR-4 solder mask layer innovation and a gradient lamination process, the problems of heat dissipation bottleneck and interlayer reliability in a high-power scene are systematically solved, and the composite insulation structure is especially suitable for the high-end fields of new energy automobile electric control, 5G base station power supplies and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of printed circuit board manufacturing, and particularly to a multi-layer printed circuit board for power circuits and a preparation method thereof. Background Art

[0002] Traditional power circuit boards mostly use epoxy resin ink as the solder mask layer, which has insufficient high-temperature resistance and mechanical strength, and is prone to interlayer delamination or pad oxidation. In addition, in the existing process, bubbles are often caused by uneven filling during multi-layer lamination, affecting heat dissipation and electrical performance. For example, Patent CN87107023 proposes a method for manufacturing a metal core multi-layer printed circuit board, but it does not solve the problems of interlayer isolation and heat dissipation optimization in high-power scenarios. Especially for multi-layer printed circuit boards used in planar transformers, which require higher electrical performance and need to have high stability and good voltage resistance. Therefore, there is an urgent need for a multi-layer circuit board solution that takes into account voltage resistance, heat dissipation efficiency, and process stability. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a multi-layer printed circuit board for power circuits and a preparation method thereof, which can solve the problems of poor voltage resistance and poor heat dissipation effect in the past by improving the interlayer structure and preparation process of the multi-layer printed circuit board.

[0004] To solve the above technical problems, the present invention discloses a multi-layer printed circuit board for power circuits, including at least two double-sided copper clad laminates and two single-sided copper sheets. The two double-sided copper clad laminates are stacked in the height direction, and an insulating layer is provided between the two double-sided copper clad laminates. One of the single-sided copper sheets is stacked above the upper double-sided copper clad laminate, and the other single-sided copper sheet is stacked below the lower double-sided copper clad laminate. An insulating layer is provided between the single-sided copper sheet and the double-sided copper clad laminate, and a solder mask layer is provided on the outside of each single-sided copper sheet.

[0005] Among them, the insulating layer includes a first filling adhesive layer, an intermediate isolation layer, and a second filling adhesive layer stacked in sequence from top to bottom.

[0006] Among them, both the first filling adhesive layer and the second filling adhesive layer are semi-cured epoxy resin adhesive films.

[0007] Among them, the intermediate isolation layer is a FR-4 isolation layer.

[0008] Among them, the solder mask layer is a FR-4 solder mask layer.

[0009] Among them, a semi-cured epoxy resin adhesive film is also provided between the single-sided copper sheet and the solder mask layer.

[0010] Among them, the double-sided copper clad laminate includes a first copper foil, a PP semi-cured sheet, and a second copper foil stacked in sequence from top to bottom.

[0011] The present application also provides a method for preparing a multilayer printed circuit board for a power circuit, including the following steps. Step 1, prefabricate a double-sided copper clad laminate. Select two T2 copper foils with a thickness range of 0.1 mm to 0.5 mm and a surface roughness ≤ 1.5 μm. Select a PP semi-cured sheet with a thickness before curing of 0.05 mm to 0.2 mm. Press and laminate according to the lamination method of the first copper foil, the PP semi-cured sheet, and the second copper foil. The pressing temperature is 120°C to 180°C, the pressing pressure is 10 MPa to 30 MPa. After pressing and cooling and curing, cut to obtain a prefabricated double-sided copper clad laminate. Step 2, first patterning. Perform drilling, copper deposition, exposure, and etching processes on the double-sided copper clad laminate in step 1 in sequence, so that the double-sided copper clad laminate in step 1 forms a preset circuit and hole positions. Step 3, multilayer pressing. First, use a semi-cured epoxy resin film to fill each copper surface of the double-sided copper clad laminate after etching in step 2. Then stack multiple double-sided copper clad laminates, and place an FR-4 isolation layer between adjacent two semi-cured epoxy resin films to form a copper clad laminate assembly. Select two single-sided copper sheets. After filling the bottom surface of one single-sided copper sheet with a semi-cured epoxy resin film, stack it above the copper clad laminate assembly. After filling the top surface of the other single-sided copper sheet with a semi-cured epoxy resin film, stack it below the copper clad laminate assembly. During the process of stacking the two single-sided copper sheets, place an FR-4 isolation layer between the single-sided copper sheet and the two semi-cured epoxy resin films of the copper clad laminate assembly. Finally, position each single-sided copper sheet and the double-sided copper clad laminate through rivets or jigs, and press and form through a press to obtain a multilayer pressed circuit board. Step 4, second patterning. Perform the drilling, copper deposition, exposure, and etching processes in step 2 on the multilayer pressed circuit board in step 3, so that the single-sided copper sheets located above and below the copper clad laminate assembly form a preset circuit and hole positions. Step 5, press an FR-4 solder mask layer and a text layer on the outside of the single-sided copper sheet. Step 6, process the outer shape of the multilayer pressed circuit board.

[0012] Preferably, in step 5, first use a semi-cured epoxy resin film to fill the copper surface of the single-sided copper sheet, and then press the FR-4 solder mask layer.

[0013] Compared with the prior art, the multilayer printed circuit board for power current in the embodiment of the present invention has the following beneficial effects:

[0014] By setting an insulating layer, stress buffering and dielectric strength improvement can be achieved. Using FR-4 material to replace traditional ink, the heat resistance is increased to above 260°C, there is no delamination in the thermal cycle test, the anti-mechanical shock strength is increased by 3 times, and the composite insulation structure can effectively improve the thermal conductivity, solving the problems of poor voltage resistance and poor heat dissipation effect in the past.

[0015] The preparation method of the multi-layer printed circuit board for the power circuit of the present application can reduce the waste of copper materials by adopting the secondary patterning process, improve the yield rate to 98.5%, make the bubble rate of the product after lamination <0.1% with the filling of the semi-cured adhesive film, and the dielectric strength ≥ 40 kV / mm. The process design is reasonable, which can effectively improve the electrical performance of the multi-layer printed circuit board and improve the production efficiency. Brief Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a schematic structural diagram of the multi-layer printed circuit board for the power circuit in the embodiment;

[0018] Figure 2 It is a schematic structural diagram of the double-sided copper clad laminate in the embodiment. Detailed Embodiments

[0019] In order to enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0020] The terms "first", "second", etc. in the specification and claims of the present invention and the above drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, device, product or terminal including a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or terminals.

[0021] Referring to "embodiment" in this article means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of the present invention. The appearance of this phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0022] The present invention discloses a specific implementation manner of a multilayer printed circuit board for a power circuit. Please refer to Figure 1 A multilayer printed circuit board includes two double-sided copper clad laminates and two single-sided copper sheets. The two double-sided copper clad laminates are stacked in the height direction, and an insulating layer is provided between the two double-sided copper clad laminates. One of the single-sided copper sheets is stacked above the upper double-sided copper clad laminate, and the other single-sided copper sheet is stacked below the lower double-sided copper clad laminate. An insulating layer is provided between the single-sided copper sheet and the double-sided copper clad laminate, and a solder mask layer is provided on the outer side of each single-sided copper sheet. It should be noted that the number of double-sided copper clad laminates can be selectively set according to actual needs, and can be three, four, five, etc.

[0023] As a preferred solution, the insulating layer includes a first filling adhesive layer, an intermediate isolation layer, and a second filling adhesive layer that are stacked in sequence from top to bottom. A semi-cured epoxy resin film is also provided between the single-sided copper sheet and the solder mask layer. Specifically, both the first filling adhesive layer and the second filling adhesive layer are semi-cured epoxy resin films, and the intermediate isolation layer is an FR-4 isolation layer. Using FR-4 to replace traditional ink can effectively improve the heat resistance, thereby further improving the electrical performance of the multilayer printed circuit board. Using a semi-cured epoxy resin film as the filling adhesive to fill each copper sheet can achieve flat filling of the etching depression, ensuring the stability and flatness of the interlayer structure.

[0024] Optionally, the double-sided copper clad laminate includes a first copper foil, a PP semi-cured sheet, and a second copper foil that are stacked in sequence from top to bottom. In this embodiment, the solder mask layer is an FR-4 solder mask layer, and FR-4 can further improve the mechanical strength and high-temperature resistance of the product.

[0025] For the multilayer printed circuit board of this embodiment, by setting the insulating layer, stress buffering and dielectric strength improvement can be achieved. Using FR-4 material to replace traditional ink, the temperature resistance is increased to above 260 °C, there is no delamination in the thermal cycle test, and the anti-mechanical shock strength is increased by 3 times. The composite insulation structure can effectively improve the thermal conductivity coefficient, solving the problems of poor voltage resistance and poor heat dissipation effect in the past. The temperature resistance of the FR-4 solder mask layer is increased to above 200 °C, and the adhesion is increased by 30%. The uniformity of the filling adhesive improves the heat dissipation efficiency by 15% - 20%. The multilayer lamination structure reduces the parasitic inductance and is suitable for MHz-level high-frequency power circuits.

[0026] The present invention discloses a preparation method of a multilayer printed circuit board for a power circuit, including the following steps.

[0027] Step 1: Prepare a double-sided copper clad laminate. Select two T2 copper foils with a thickness ranging from 0.1 mm to 0.5 mm and a surface roughness of ≤ 1.5 μm. Select a PP prepreg with a thickness before curing of 0.05 mm to 0.2 mm. Press them in the lamination sequence of the first copper foil, PP prepreg, and the second copper foil at a pressing temperature of 120°C to 180°C and a pressing pressure of 10 MPa to 30 MPa. After pressing, cool and cure, and then cut to obtain the prefabricated double-sided copper clad laminate. The thickness of the T2 copper foil is 0.1 mm to 0.5 mm, which can reduce the line resistance and the skin effect loss. The PP prepreg is mainly used to bond the copper layers, provide good insulation, and ensure electrical performance.

[0028] Step 2: First patterning. Perform drilling, electroless copper plating, exposure, and etching processes on the double-sided copper clad laminate in Step 1 in sequence to form a preset circuit and hole positions on the double-sided copper clad laminate in Step 1. This step is a traditional process. After drilling, electroless copper plating is carried out to form a conductive layer inside the holes, and the exposure and etching define the circuit.

[0029] Step 3: Multilayer lamination. First, use a semi-cured epoxy resin film to fill each copper surface of the double-sided copper clad laminate after etching in Step 2; then stack multiple double-sided copper clad laminates, and place FR-4 isolation layers between adjacent two semi-cured epoxy resin films to form a copper clad laminate assembly; select two single-sided copper sheets, stack one single-sided copper sheet on top of the copper clad laminate assembly after filling the bottom surface with a semi-cured epoxy resin film, stack the other single-sided copper sheet on the bottom of the copper clad laminate assembly after filling the top surface with a semi-cured epoxy resin film, and place FR-4 isolation layers between the single-sided copper sheet and the two semi-cured epoxy resin films of the copper clad laminate assembly during the stacking process of the two single-sided copper sheets; finally, position each single-sided copper sheet and the double-sided copper clad laminate through rivets or jigs, and press and form them with a press to obtain a multilayer laminated circuit board.

[0030] Among them, the filling adhesive (semi-cured epoxy resin film) can cover the depressions on the etched copper surface to ensure a flat surface. In addition, it can also cooperate with vacuum pressing to eliminate bubbles and ensure flatness. The FR-4 isolation layer is inserted between the films to provide interlayer insulation and mechanical strength. Positioning is carried out using rivets or jigs to ensure that the interlayer offset is < 5 μm.

[0031] Step 4: Second patterning. Perform the drilling, electroless copper plating, exposure, and etching processes in Step 2 on the multilayer laminated circuit board in Step 3 to form a preset circuit and hole positions on the single-sided copper sheets located above and below the copper clad laminate assembly. Repeating drilling and electroless copper plating after the first lamination can ensure the reliability of interlayer interconnection. The two patterning processes reduce copper material waste, and the yield rate is increased to 98.5%.

[0032] Step 5: Press and laminate the FR-4 solder mask layer and the legend layer on the outer side of the single-sided copper sheet. Preferably, in Step 5, first fill the copper surface of the single-sided copper sheet with a semi-cured epoxy resin film, and then press and laminate the FR-4 solder mask layer, which can further improve the insulation performance and flatness.

[0033] Step 6: Machine the outer shape of the multilayer laminated circuit board.

[0034] In the preparation method of the multilayer printed circuit board for power circuits in this embodiment, the secondary patterning process can reduce the waste of copper materials and increase the yield rate to 98.5%. The filling of the semi-cured film makes the bubble rate of the laminated product <0.1%, and the dielectric strength ≥40 kV / mm. The process design is reasonable, which can effectively improve the electrical performance of the multilayer printed circuit board and improve the production efficiency. Through the composite insulation structure design, the innovation of the FR-4 solder mask layer and the gradient lamination process, the heat dissipation bottleneck and the interlayer reliability problem in high-power scenarios are systematically solved, and it is especially suitable for high-end fields such as new energy vehicle electronic control and 5G base station power supply.

[0035] Finally, it should be noted that: What is disclosed in the preparation method of the multilayer printed circuit for power circuits disclosed in the embodiments of the present invention is only the preferred embodiments of the present invention, which are only used to illustrate the technical solutions of the present invention, rather than to limit it; Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: They can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; And these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multilayer printed circuit board for a power circuit, characterized in that, It includes at least two double-sided copper clad laminates and two single-sided copper sheets. The two double-sided copper clad laminates are stacked in the height direction, and an insulating layer is provided between the two double-sided copper clad laminates. One of the single-sided copper sheets is stacked above the upper double-sided copper clad laminate, and the other single-sided copper sheet is stacked below the lower double-sided copper clad laminate. An insulating layer is provided between the single-sided copper sheet and the double-sided copper clad laminate, and a solder mask layer is provided on the outer side of each single-sided copper sheet.

2. The multilayer printed circuit board for a power circuit according to claim 1, wherein, The insulating layer includes a first filling adhesive layer, an intermediate isolation layer, and a second filling adhesive layer that are stacked in sequence from top to bottom.

3. The multilayer printed circuit board for a power circuit according to claim 2, wherein, Both the first filling adhesive layer and the second filling adhesive layer are semi-cured epoxy resin adhesive films.

4. A multilayer printed circuit board for a power circuit according to claim 2, wherein, The intermediate isolation layer is an FR-4 isolation layer.

5. A multilayer printed circuit board for a power circuit according to claim 1, wherein, The solder mask layer is an FR-4 solder mask layer.

6. A multilayer printed circuit board for a power circuit according to claim 1, wherein A semi-cured epoxy resin adhesive film is also provided between the single-sided copper sheet and the solder mask layer.

7. A multilayer printed circuit board for a power circuit according to claim 1, characterized in that, The double-sided copper clad laminate includes a first copper foil, a PP semi-cured sheet, and a second copper foil that are stacked in sequence from top to bottom.

8. A method for preparing a multilayer printed circuit board for a power circuit, characterized in that, It includes the following steps Step 1, prefabricate the double-sided copper clad laminate. Select two T2 copper foils with a thickness range of 0.1 mm to 0.5 mm and a surface roughness ≤ 1.5 μm. Select a PP semi-cured sheet with a thickness of 0.05 mm to 0.2 mm before curing. Press them in the stacking manner of the first copper foil, the PP semi-cured sheet, and the second copper foil. The pressing temperature is 120 °C to 180 °C, the pressing pressure is 10 MPa to 30 MPa, and after pressing, it is cooled and cured and cut to obtain the prefabricated double-sided copper clad laminate. Step 2, primary patterning. Perform drilling, copper plating, exposure, and etching processes on the double-sided copper clad laminate in Step 1 in sequence to form a preset circuit and hole positions on the double-sided copper clad laminate in Step 1. Step 3, multi-layer pressing. First, use a semi-cured epoxy resin adhesive film to fill each copper surface of the double-sided copper clad laminate etched in Step 2; then stack multiple double-sided copper clad laminates, and place an FR-4 isolation layer between adjacent two semi-cured epoxy resin adhesive films to form a copper clad laminate assembly; select two single-sided copper sheets, fill the bottom surface of one single-sided copper sheet with a semi-cured epoxy resin adhesive film and stack it above the copper clad laminate assembly, fill the top surface of the other single-sided copper sheet with a semi-cured epoxy resin adhesive film and stack it below the copper clad laminate assembly. During the process of stacking the two single-sided copper sheets, place an FR-4 isolation layer between the single-sided copper sheet and the two semi-cured epoxy resin adhesive films of the copper clad laminate assembly; finally, position each single-sided copper sheet and the double-sided copper clad laminate through rivets or jigs, and press and form them by a press to obtain a multi-layer pressed circuit board. Step 4, secondary patterning. Perform the drilling, copper plating, exposure, and etching processes in Step 2 on the multi-layer pressed circuit board in Step 3 to form a preset circuit and hole positions on the single-sided copper sheets located above and below the copper clad laminate assembly. Step 5, press an FR-4 solder mask layer and a text layer on the outer side of the single-sided copper sheet. Step 6, process the outer shape of the multi-layer pressed circuit board.

9. The manufacturing method of a multilayer printed circuit board for a power circuit according to claim 8, characterized in that, In Step 5, first use a semi-cured epoxy resin adhesive film to fill the copper surface of the single-sided copper sheet, and then press the FR-4 solder mask layer.

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