Manufacturing method of printed circuit board with ultrathin copper foil

Abstract

The invention relates to a method for manufacturing a printed circuit board with an ultrathin copper foil, which comprises the following steps of: in the process of pressing to form the printed circuit board, melting a prepreg on the outer layer into a semi-cured state; performing copper metal chemical deposition on the surface of the prepreg to deposit a first chemical copper layer; and curing the prepreg, punching the printed circuit board, depositing a second chemical copper layer, and curing the second chemical copper layer to obtain the printed circuit board with the ultrathin copper foil. According to the manufacturing method of the printed circuit board with the ultra-thin copper foil, chemical copper with the required thickness is deposited on the prepreg on the secondary outer layer of the printed circuit board in a chemical deposition mode, the chemical copper is manufactured into the outer layer copper foil of the printed circuit board, the thickness can be as low as 5-10 microns, the surface copper range is smaller, and the copper foil thickness is smaller. And a circuit board product with smaller line width spacing can be manufactured.

Description

Technical Field

[0001] The present invention relates to the field of electronic circuit boards, and particularly to a method for manufacturing a printed circuit board with an ultra-thin copper foil. Background Art

[0002] For the conventional outer copper foil of printed circuit boards, generally, a rolled copper foil with a corresponding thickness is directly purchased from a material manufacturer and bonded to the printed circuit board by means of lamination. The thinnest of such conventional outer copper foils is about 12 μm, which is actually relatively thick and has a large surface copper difference. The surface copper difference usually refers to surface defects or unevenness that appear on the surface of a copper ingot during the smelting and processing of copper, and here it refers to the surface defects or unevenness of the copper foil. For copper foils of this thickness, the outer copper foil generally has a minimum line width and pitch of 0.075 μm / 0.075 μm. If a smaller line width and pitch (which means a more complex circuit) is desired for the outer copper foil, the surface copper difference must be controlled to be smaller, and the average thickness of the outer copper foil must be further reduced. Summary of the Invention

[0003] Based on this, it is necessary to provide a method for manufacturing a printed circuit board with an ultra-thin copper foil for at least one of the above-mentioned problems.

[0004] The method for manufacturing a printed circuit board with an ultra-thin copper foil provided by the present invention includes the following steps:

[0005] During the process of laminating to form a printed circuit board, the outer prepreg is melted into a semi-cured state.

[0006] Copper metal chemical deposition is performed on the surface of the prepreg to deposit a first chemical copper layer.

[0007] The prepreg is cured, holes are drilled in the printed circuit board, and then a second chemical copper layer is deposited and cured to obtain a printed circuit board with an ultra-thin copper foil.

[0008] In one embodiment, melting the outer prepreg into a semi-cured state includes melting the prepregs of the two opposite outer layers of the printed circuit board into a semi-cured state.

[0009] In one embodiment, after the step of depositing the first chemical copper layer, the method further includes drying the first chemical copper layer.

[0010] In one embodiment, the step of curing the prepreg includes: completely curing the semi-cured prepreg at a temperature of 180°C to 220°C by a press.

[0011] In one embodiment, the step of depositing a second electroless copper layer on the printed circuit board after drilling and then curing it includes: depositing the second electroless copper layer on the inner wall of the hole.

[0012] In one embodiment, the step of depositing a second electroless copper layer on the printed circuit board after drilling and then curing it further includes: cleaning the surface of the printed circuit board with fine sandpaper of 8000 mesh or above after drilling.

[0013] In one embodiment, after the step of depositing a second electroless copper layer on the printed circuit board after drilling and then curing it, the following steps are further included: drying the second electroless copper layer, baking the surface of the printed circuit board and the second electroless copper layer in the hole at a temperature of 200 °C, and then performing sandblasting treatment.

[0014] The technical solutions provided in the embodiments of the present invention bring the following beneficial technical effects:

[0015] A method for manufacturing a printed circuit board with an ultra-thin copper foil provided by the present invention uses chemical deposition to deposit electroless copper with a required thickness on the prepreg of the second outermost layer of the printed circuit board, and makes the electroless copper into the outer copper foil of the printed circuit board. The thickness can be as low as 5-10 μm, and the surface copper difference is smaller, and a circuit board product with a smaller line width and pitch can be manufactured.

[0016] The additional aspects and advantages of the present application will be given in the subsequent parts and will be understood in detail from the subsequent description, or will be learned through the specific implementation of the present invention. Description of the Drawings

[0017] Figure 1 It is a schematic flow chart of a method for manufacturing a printed circuit board with an ultra-thin copper foil in an embodiment of the present invention;

[0018] Figure 2 It is a schematic structural diagram of a printed circuit board in an embodiment of the present invention;

[0019] Figure 3 It is a schematic diagram of the structural change of the ultra-thin copper layer of a printed circuit board in an embodiment of the present invention.

[0020] Description of the reference numerals:

[0021] 10 - Inner layer, 20 - Prepreg, 30 - Electroless copper layer. Detailed Description of the Embodiments

[0022] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The possible embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein with reference to the drawings. The embodiments described by referring to the drawings are exemplary and are used to make the understanding of the disclosure of the present invention more thorough and comprehensive, and should not be construed as a limitation to the present invention. In addition, if the detailed description of the known technology is non-essential technology for the features of the present invention shown, these technical details may be omitted.

[0023] Those skilled in the relevant art can understand that unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those of ordinary skill in the art to which the present invention pertains. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with their meaning in the prior art, and will not be interpreted with an idealized or overly formal meaning unless specifically defined as herein.

[0024] Those skilled in the art of the present technology can understand that unless specifically stated, the singular forms "a", "an", "the", and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of the present application means the presence of the described features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or their groups. It should be understood that the phrase "and / or" used herein includes all or any unit and all combinations of one or more of the associated listed items.

[0025] The technical solution of the present invention and how this technical solution solves the above technical problems will be described in detail below with specific embodiments.

[0026] The manufacturing method of a printed circuit board with an ultra-thin copper foil provided by the present invention, as Figure 1 shown, includes the following steps:

[0027] S100: During the process of laminating to form a printed circuit board, the outer prepreg is melted into a semi-cured state.

[0028] S200: Conduct chemical deposition of copper metal on the surface of the prepreg to deposit a first chemical copper layer.

[0029] S300: Cure the prepreg, drill holes in the printed circuit board, then deposit a second chemical copper layer and cure it to obtain a printed circuit board with an ultra-thin copper foil.

[0030] The manufacturing method of a printed circuit board with an ultra-thin copper foil provided by the present invention uses chemical deposition to deposit chemical copper with the required thickness on the prepreg of the second outermost layer of the printed circuit board, and makes the chemical copper into the outer copper foil of the printed circuit board. The thickness can be as low as 5-10um, and the surface copper difference is smaller, so that circuit board products with smaller line width and spacing can be manufactured.

[0031] Specifically, in one embodiment, melting the prepregs of the outer layer into a semi-cured state includes melting the prepregs of the two opposite outer layers of the printed circuit board into a semi-cured state.

[0032] Specifically, in one embodiment, after the step of depositing the first chemical copper layer, it further includes drying the first chemical copper layer.

[0033] Specifically, in one embodiment, the step of curing the prepreg includes: completely curing the semi-cured prepreg at a temperature of 180°C to 220°C by a press.

[0034] Specifically, in one embodiment, the step of depositing the second chemical copper layer and curing after drilling holes in the printed circuit board includes: depositing the second chemical copper layer on the inner wall of the holes.

[0035] Specifically, in one embodiment, the step of depositing the second chemical copper layer and curing after drilling holes in the printed circuit board further includes: cleaning the surface of the printed circuit board with fine sandpaper of 8000 mesh or more after drilling.

[0036] Specifically, in one embodiment, after the step of depositing the second chemical copper layer and curing after drilling holes in the printed circuit board, it further includes: drying the second chemical copper layer, baking the second chemical copper layer on the surface and in the holes of the printed circuit board at a temperature of 200°C until solid, and then performing sandblasting treatment.

[0037] The following are specific embodiments:

[0038] As Figure 2 shown, in the process of laminating the prepreg of the second outermost layer with the inner layer to form a printed circuit board semi-finished product, the prepreg of the second outermost layer is dissolved into a semi-cured state by low temperature and then taken out. The prepreg in the printed circuit board is bonded to the substrate together, which is convenient for subsequent deposition of thin copper. The prepreg will play a certain filling role in the circuit layer during the melting process, making the prepreg have a better bonding force with the substrate and better structural compactness, which is convenient for subsequent deposition of copper layer on the prepreg and not easy to fall off.

[0039] As Figure 3As shown, on the surface of the printed circuit board, specifically on the outer surfaces of the upper and lower prepregs, electroless copper deposition is carried out. After depositing an electroless copper layer with a thickness of 5 - 10 μm, it is taken out and dried. The obtained electroless copper layer, that is, the first electroless copper layer, serves the same function as the substrate copper of a normal board.

[0040] Then, the press cures the uncured sub - outer prepreg completely at a high temperature. The temperature varies according to different materials, generally around 200 °C, specifically 180 °C - 220 °C. After the outermost prepreg of the printed circuit board is completely cured, drilling operations are carried out, that is, normal drilling. After drilling, the board surface is cleaned with fine sandpaper of 8000 mesh and above. The main purpose of cleaning the board surface at this time is to clean the burrs at the hole openings caused by drilling, which is convenient for subsequent copper layer deposition and electroplating. After cleaning the board surface, electroless thin copper deposition is carried out on the board surface again. After depositing a second electroless copper layer with a thickness of 5 - 10 μm, it is taken out and dried. Then, the electroless copper layer on the surface and in the holes is baked solid at a high temperature (temperature at 200 ± 20 °C) to enhance the bonding force of the second electroless copper layer and reduce the surface copper difference. Then it is sent to the sandblasting line for light sandblasting. At this time, the sandblasting parameters and line speed are different from those of normal boards and need to be specially controlled and adjusted. In one solution, the pressure is 1.5 ± 0.5 kg / cm 2 , and the line speed is 2.8 ± 0.1 m / min. After sandblasting, it directly goes through the pre - treatment before patterning, then film laminating, exposure, and development, and finally normal pattern electroplating.

[0041] By depositing a thin electroless copper layer on the sub - outer semi - cured prepreg of the printed circuit board at a low temperature, then curing the sub - outer prepreg by hot pressing at a high temperature and depositing a thin layer of copper again on the board surface (mainly depositing copper in the holes) after drilling, and then compacting the electroless copper at a high temperature, followed by sandblasting and pre - treatment before pattern electroplating, the bonding force between the copper surface and the dry film is enhanced. The pre - treatment before pattern electroplating does not pass through the grinding and micro - etching sections, realizing a printed circuit board with a brand - new ultra - thin copper, which is more suitable for making fine outer - layer circuits.

[0042] Those skilled in the art of this technology can understand that the various operations, methods, steps, measures, and solutions in the processes discussed in this application can be alternated, changed, combined, or deleted. Further, the other steps, measures, and solutions in the various operations, methods, and processes discussed in this application can also be alternated, changed, rearranged, decomposed, combined, or deleted. Further, those in the prior art that have steps, measures, and solutions in the various operations, methods, and processes disclosed in this application can also be alternated, changed, rearranged, decomposed, combined, or deleted.

[0043] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0044] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any one or more embodiments or examples in a suitable manner.

[0045] It should be understood that although the steps in the flowcharts of the accompanying drawings are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction for the execution of these steps, and they can be executed in other orders. Moreover, at least some of the steps in the flowcharts of the accompanying drawings may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same moment but can be executed at different moments, and their execution order is not necessarily sequential but can be executed alternately or in turn with at least a part of other steps or sub-steps or stages of other steps.

[0046] The above are only some embodiments of this application. It should be noted that for those of ordinary skill in the art, without departing from the principle of this application, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of this application.

Claims

1. A method for manufacturing a printed circuit board with ultra-thin copper foil, characterized in that: The steps include: During the process of lamination to form a printed circuit board, the outer prepreg is melted into a semi-cured state; Performing copper metal chemical deposition on the surface of the prepreg to deposit a first chemical copper layer; The semi-cured sheet is cured, and a second chemical copper layer is deposited and cured after drilling holes on the printed circuit board, so as to obtain a printed circuit board with an ultra-thin copper foil.

2. The method for manufacturing a printed circuit board with an ultra-thin copper foil according to claim 1, characterized in that: The step of melting the outer prepreg into a semi-solidified state includes melting both of the outer prepregs of the two opposite layers of the printed circuit board into a semi-solidified state.

3. The method for manufacturing a printed circuit board with an ultra-thin copper foil according to claim 1, characterized in that: After the step of depositing the first chemical copper layer, the method further includes drying the first chemical copper layer.

4. The method for manufacturing a printed circuit board with an ultra-thin copper foil according to claim 1, characterized in that: The step of curing the prepreg comprises: completely curing the prepreg in a semi-cured state at a temperature of 180° C. to 220° C. through a press.

5. The method for manufacturing a printed circuit board with an ultra-thin copper foil according to claim 1, characterized in that: The step of depositing a second chemical copper layer and curing the layer after drilling a hole on the printed circuit board includes: depositing the second chemical copper layer on the inner wall of the hole.

6. The method for manufacturing a printed circuit board with ultra-thin copper foil according to claim 1, characterized in that: The step of depositing a second chemical copper layer and curing it after drilling holes on the printed circuit board also includes: using fine sandpaper of 8000 mesh or above to clean the board surface of the printed circuit board after drilling holes.

7. The method for manufacturing a printed circuit board with an ultra-thin copper foil according to claim 1, characterized in that: After the steps of depositing a second chemical copper layer and curing it after drilling holes on the printed circuit board, the method further includes: drying the second chemical copper layer, baking the surface of the printed circuit board and the second chemical copper layer in the hole at a temperature of 200° C., and then sandblasting.

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