Circuit board processing method and circuit board

Abstract

The invention relates to the technical field of circuit board processing, and provides a circuit board processing method and a circuit board, and the method comprises the steps: drilling a blind hole in the circuit board; copper deposition is carried out on the blind holes, and hole filling electroplating is carried out; surface copper of the circuit board is thinned; drilling a through hole in the circuit board; copper deposition is carried out on the through hole, and primary electroplating is carried out, so that the surface copper thickness of the antenna area meets the requirement; covering and protecting the antenna area by using a dry film; carrying out secondary electroplating; and removing the dry film. According to the circuit board processing method, the blind hole and the through hole are processed separately, and the hole copper thickness of the blind hole filling and the hole copper thickness of the through hole do not need to be considered at the same time in the electroplating process, so that the blind hole filling, the through hole copper, the antenna area surface copper and the non-antenna area surface copper can meet the design requirements; moreover, the surface copper thickness of the antenna area can be stabilized at the target copper thickness precision, and the surface copper thickness of the non-antenna area can be stabilized at the target copper thickness precision, so that the uniformity requirement is met.

Description

Technical Field

[0001] The present application relates to the technical field of circuit board processing, and in particular to a circuit board processing method and a circuit board. Background Art

[0002] Currently, mainstream high-frequency millimeter-wave radar PCB (Printed Circuit Board) products all feature antennas for transmitting and receiving signals on their surfaces. To ensure antenna signal matching, some product designs differentiate between the surface copper areas of the antenna and non-antenna areas. Generally, the copper thickness in the antenna area is required to be thinner. This is known in the industry as "partially thinned antenna copper design."

[0003] The traditional manufacturing process for high-frequency millimeter-wave radar PCBs involves laser drilling blind vias, mechanical drilling through-holes, copper deposition and via-filling plating, dry film exposure and development, localized copper reduction, and film stripping to achieve thin copper thickness in the antenna area. However, this method fails to simultaneously ensure effective blind via filling, uniform copper thickness in through-holes, and uniform copper thickness in the surface copper (including both the antenna and non-antenna areas), impacting product yield. Summary of the Invention

[0004] In view of this, the embodiments of the present application provide a circuit board processing method and a circuit board to solve the problem that the traditional high-frequency millimeter-wave radar PCB product processing method cannot simultaneously take into account the blind hole filling effect, the through hole copper uniformity and the surface copper (including antenna area and non-antenna area) copper thickness uniformity.

[0005] The first aspect of the present application provides a circuit board processing method, comprising:

[0006] Drilling blind vias in circuit boards;

[0007] Plating copper in the blind holes and performing hole-filling electroplating;

[0008] Thinning the surface copper of the circuit board;

[0009] drilling through holes in the circuit board;

[0010] The through hole is copper-plated and electroplated once to ensure that the surface copper thickness of the antenna area meets the requirements;

[0011] Covering the antenna area with a dry film for protection;

[0012] Perform secondary electroplating;

[0013] The dried film is removed.

[0014] The beneficial effects of the circuit board processing method provided by the embodiment of the present application are as follows: during the hole filling electroplating, since only blind holes are drilled on the circuit board and no through holes are drilled, the electroplating parameters only need to consider the blind hole filling depression index requirements (hole filling effect), and there is no need to consider the through hole copper index; therefore, the electroplating parameters can reduce the current density to reduce the amount of thickening of the surface copper, thereby improving the uniformity of the surface copper after electroplating and reducing the surface copper range. Since the surface copper range generated during the surface copper thinning process is positively correlated with the amount of copper reduction, and the amount of thickening of the surface copper after the hole filling electroplating is reduced, the surface copper range generated during the surface copper thinning process is relatively small, reducing the impact of copper reduction on the surface copper range. After the through hole is electroplated once, the surface copper thickness of the antenna area meets the requirements. Compared with the copper reduction method to meet the requirements of the surface copper thickness of the antenna area, this method does not aggravate the problem of uneven copper thickness in the antenna area, thereby ensuring the uniformity of the antenna size and thus ensuring the yield of the product. Afterwards, the antenna area is covered with dry film, and only the surface copper and hole copper thickness are increased in the non-antenna area, so that the thickness and uniformity of the surface copper and hole copper in the non-antenna area meet the requirements; at the same time, the uniformity of the antenna area is not affected during the secondary electroplating, and the uniformity is better.

[0015] In some embodiments, when performing via filling electroplating, the current density is 14-16 ASF.

[0016] In some embodiments, the surface copper of both sides of the circuit board is thinned.

[0017] In some embodiments, the copper reduction solution used when thinning the surface copper of the circuit board includes sulfuric acid and hydrogen peroxide, wherein the concentration of sulfuric acid is 100-180 g / L and the concentration of hydrogen peroxide is 20-40 g / L.

[0018] In some embodiments, the copper-reducing solution further comprises copper ions, and the concentration of the copper ions is 0-50 g / L.

[0019] In some embodiments, the temperature used when thinning the surface copper of the circuit board is 30-35°C.

[0020] In some embodiments, the primary electroplating is flash plating; and / or the secondary electroplating is pulse plating.

[0021] In some embodiments, the blind hole is formed by laser drilling equipment; and / or the through hole is formed by mechanical drilling equipment.

[0022] In some embodiments, the surface copper thickness before drilling the blind hole on the circuit board is 10±1um; the surface copper thickness after filling the hole electroplating is 45±4um; the surface copper thickness of the circuit board after thinning is 20±5um; the surface copper thickness after one electroplating is 28±5um; the surface copper thickness of the antenna area after the second electroplating is 28±5um, and the surface copper thickness of the non-antenna area is 48±8um.

[0023] In some embodiments, after the dry film is removed, a vacuum laminating device is used to cover the dry film on the circuit board under vacuum and pressurized conditions and fill the intersection of the high and low thickness differences of the surface copper, and perform an "exposure-development-etching-film stripping" process to obtain a graphic circuit.

[0024] A second aspect of the present application provides a circuit board, which is processed by the circuit board processing method described in the first aspect.

[0025] The circuit board adopts any one or more embodiments of the above-mentioned circuit board processing method, and thus has the beneficial effects of the above-mentioned embodiments, which will not be described in detail here.

[0026] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or conventional technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1 This is a schematic diagram of the structure after blind holes and through holes are drilled on a circuit board in the prior art;

[0029] Figure 2 yes Figure 1 The schematic diagram of the structure of the circuit board after copper deposition and hole filling electroplating is shown;

[0030] Figure 3 yes Figure 2 The schematic diagram of the circuit board shown is a structural diagram of using dry film to cover the non-antenna area;

[0031] Figure 4 yes Figure 3 The schematic diagram of the structure of the circuit board shown is after the surface copper of the antenna area is thinned;

[0032] Figure 5 yes Figure 4 The schematic diagram of the structure of the circuit board after the dry film is removed is shown;

[0033] Figure 6 is a flow chart of a circuit board processing method provided by some embodiments of the present application;

[0034] Figure 7 This is a schematic diagram of the structure after blind holes are drilled on a circuit board provided in some embodiments of the present application;

[0035] Figure 8 yes Figure 7 The schematic diagram of the structure of the circuit board after copper deposition and hole filling electroplating is shown;

[0036] Figure 9 yes Figure 8 The schematic diagram of the structure of the circuit board after the surface copper is thinned is shown;

[0037] Figure 10 yes Figure 9 Schematic diagram of the structure after drilling through holes on the circuit board shown;

[0038] Figure 11 yes Figure 10 The schematic diagram of the structure of the circuit board shown is after copper deposition and primary electroplating;

[0039] Figure 12 yes Figure 11 The schematic diagram of the circuit board shown is a structural diagram of the antenna area covered with dry film;

[0040] Figure 13 yes Figure 12 The schematic diagram of the structure of the circuit board after secondary electroplating is shown;

[0041] Figure 14 yes Figure 13 The schematic diagram of the circuit board structure after the dry film is removed is shown.

[0042] The meanings of the marks in the figure are:

[0043] 10. Circuit board;

[0044] 11. Blind hole;

[0045] 12. Through hole;

[0046] 13. Surface copper;

[0047] 14. Dry film;

[0048] 15. Antenna area;

[0049] 16. Non-antenna area;

[0050] 17. Hole copper;

[0051] 20. Circuit board;

[0052] 21. Blind hole;

[0053] 22. Through hole;

[0054] 23. Surface copper;

[0055] 24. Dry film;

[0056] 25. Antenna area. DETAILED DESCRIPTION

[0057] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0059] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0060] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0061] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0062] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0063] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the embodiments of the present application.

[0064] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0065] The processing methods of traditional high-frequency millimeter-wave radar PCB products are as follows: Please refer to Figure 1 First, drill the blind hole 21 and the through hole 22 on the circuit board 20; then, refer to Figure 2 , uniformly perform copper sinking and hole filling electroplating, fill the blind hole 21 at one time (the depression is less than or equal to 30um), and plate the copper thickness of the through hole 22 and the surface copper 23 to meet the requirements; then, please refer to Figure 3 and Figure 4 , cover the surface copper 23 with dry film 24 and expose the antenna area 25, and use the copper reduction method to reduce the surface copper 23 of the antenna area 25 to the target copper thickness; finally, refer to Figure 5 , the dry film 24 is removed.

[0066] High-frequency millimeter-wave radar PCB products generally use a high-frequency core board with a dielectric thickness of 5 mil (0.127 mm) as the antenna surface material. Combined with the surface copper thickness before drilling the blind via (usually around 10 μm), the blind via depth is 0.137 mm and the aperture is designed to be 0.15 mm. At this time, the aspect ratio of the blind via reaches 0.9:1. The aperture, depth, and aspect ratio of the blind via all reach the maximum capacity of the industry for via-fill electroplating, making blind via filling electroplating difficult.

[0067] Due to the characteristics of the hole-filling electroplating solution and the processing mechanism, the copper plating ability of the hole-filling electroplating for through-holes is poor, especially when the aspect ratio of the through-hole is greater than 6:1 (the aspect ratio of the through-holes of radar PCB products is generally greater than 6:1). The hole-filling electroplating filling capacity is less than 50%, that is, the increase in the through-hole copper during the electroplating process is less than half of the surface copper. In order to plate the through-hole copper to the target copper thickness (greater than or equal to 23um), it is necessary to increase the current density or extend the electroplating time. This operation will lead to the following problems: 1) The surface copper exceeds the design upper limit. The surface copper control in the design process is 50±8um, and the actual surface copper is greater than 65um; 2) The uniformity of the surface copper is poor. The finished product requires the thin copper area (i.e., antenna area) to have a tolerance of ±5um (extreme difference 10um). The actual surface copper after electroplating has a range of 15um. Combined with the copper reduction process after electroplating, the copper thickness tolerance range of the finished thin copper area far exceeds the design requirements; 3) The hole copper uniformity is poor. The hole filling electroplating capacity is less than 50%, which will cause the through-hole copper to be thick at both ends and thin in the middle, resulting in a narrowing of the through-hole mouth, affecting the subsequent drying of the through-hole and the effect of resin / solder mask ink plugging.

[0068] Moreover, after the hole-filling electroplating, a thin copper area is obtained by locally reducing copper (such as etching). As a result, the surface copper extremes of the thin copper area are affected not only by the hole-filling electroplating but also by the copper reduction, exacerbating the problem of uneven copper thickness in the thin copper area, affecting the uniformity of the antenna size, and ultimately affecting the product yield.

[0069] In order to solve the problem that traditional high-frequency millimeter-wave radar PCB product processing methods cannot simultaneously take into account the blind hole filling effect, through-hole copper uniformity, and surface copper (including antenna area and non-antenna area) copper thickness uniformity. This application provides a circuit board processing method.

[0070] The embodiment of the first aspect of the present application provides a circuit board processing method. The circuit board processing method includes:

[0071] S1, please refer to Figure 6 and Figure 7 , a blind hole 11 is drilled on the circuit board 10.

[0072] Optionally, a laser drilling device is used to drill the blind hole 11 according to the matching laser drilling data.

[0073] The number of the blind hole 11 can be one or more.

[0074] Optionally, the circuit board 10 is a high-frequency millimeter-wave radar PCB.

[0075] S2, please refer to Figure 6 and Figure 8 , copper is deposited on the blind hole 11 and the hole is filled with electroplating.

[0076] Copper plating is mainly used to make the initial metallization of the hole wall in order to achieve interlayer conduction.

[0077] Optionally, a copper deposition device is used to deposit a 0.3-0.5um copper layer on the hole wall of the drilled blind hole 11. After copper deposition, the circuit board 10 is transferred to the hole filling electroplating device. The hole filling electroplating parameter setting only needs to consider the hole filling depression index requirement of the blind hole 11 (depression is less than or equal to 30um), and it is no longer necessary to consider the hole copper 17 index of the through hole 12 at the same time. Therefore, the current density can be reduced during hole filling electroplating to reduce the thickening amount of the surface copper 13, thereby improving the uniformity of the surface copper 13 after hole filling electroplating.

[0078] For example, the current density before optimization is 22-24ASF, and the thickness of the surface copper after via filling electroplating is greater than 55um. Adding the bottom copper thickness before via filling electroplating (10um), the overall surface copper thickness reaches more than 65um, and the range of the surface copper reaches 15um. As the aspect ratio of through hole 12 increases, the current density parameter setting will be larger, the thickness of the surface copper and the range of the range will also be larger, exacerbating the unevenness of the surface copper. Among them, the electroplating time can be 90 minutes.

[0079] The optimized current density is 14-16 ASF, which is 8 ASF lower than the original current density. Theoretically, the thickness of the surface copper 13 is only 35μm. As the thickness of the surface copper 13 decreases, the uniformity of the surface copper 13 after via-fill plating also improves, and the range of the surface copper 13 is less than or equal to 8μm. In other words, the thickness of the surface copper 13 after via-fill plating is stabilized at 45±4μm, effectively controlling the thickness and uniformity of the surface copper 13.

[0080] It should be noted that current density is a physical quantity used to describe the distribution of current per unit area. In the field of electroplating, current density is commonly used in amperes per square foot (ASF).

[0081] S3, please refer to Figure 6 and Figure 9 , thinning the surface copper 13 of the circuit board 10.

[0082] Optionally, after the via-filling electroplating, the circuit board 10 is subjected to double-sided surface copper reduction, using a horizontal immersion chemical copper reduction line to thin the surface copper 13 as a whole. The thickness of the thinned surface copper 13 is less than the thickness of the antenna in the antenna area 15.

[0083] In order to further reduce the range of surface copper 13 after copper reduction, a "sulfuric acid hydrogen peroxide system" copper reduction solution is used. The copper reduction solution includes sulfuric acid (H2SO4) and hydrogen peroxide (H2O2). The concentration and temperature control range of each component in the copper reduction solution are as follows:

[0084] a) Sulfuric acid: 100-180 g / L;

[0085] b) Hydrogen peroxide: 20-40g / L;

[0086] c) Temperature: 30-35°C.

[0087] Among them, when the copper reduction solution is used for the first time, the copper reduction solution does not contain copper ions (Cu 2+ ), as the circuit board 10 is immersed in the copper-reducing solution for copper reduction, the solution will contain a certain concentration of copper ions, and the concentration of copper ions is: 0-50g / L.

[0088] Since the range of surface copper 13 generated during the copper reduction process is positively correlated with the amount of copper reduction, before optimization, the surface copper is above 65um after the hole filling electroplating is completed. In order to meet the copper thickness requirements of the antenna area, the copper reduction amount needs to be greater than 37um. The immersion time in the horizontal copper reduction solution is greater than 7min, the copper reduction amount is large, and the surface copper range caused by copper reduction will reach more than 4um; after optimization, the copper reduction amount is reduced to 20um, the immersion time in the horizontal copper reduction solution is shortened to 4min, the copper reduction amount is small, and the surface copper range caused by copper reduction can be controlled to less than or equal to 2um. In addition, the surface copper range of 13 of the original hole filling electroplating is less than or equal to 8um, and the surface copper range of 13 after copper reduction is less than or equal to 10um.

[0089] S4, please refer to Figure 6 and Figure 10 , drilling a through hole 12 on the circuit board 10.

[0090] Optionally, a mechanical drilling device is used to drill the through holes 12 on the circuit board 10 .

[0091] The number of the through hole 12 can be one or more.

[0092] S5, please refer to Figure 6 and Figure 11 , copper is deposited on the through hole 12 and electroplated once to ensure that the surface copper 13 of the antenna area 15 reaches the required thickness.

[0093] A copper layer of 0.3 to 0.5 μm is deposited on the walls of the drilled through-holes 12 using a copper deposition device. After the copper deposition, the circuit board 10 is transferred to an electroplating device for a first electroplating operation to ensure that the surface copper 13 of the antenna area 15 reaches the required thickness.

[0094] During the electroplating process, the copper layer 17 (i.e., the copper layer on the hole wall) of the through hole 12 will also increase in thickness. Since the copper layer on the hole wall of the through hole 12 after copper deposition is relatively thin, the copper layer on the hole wall of the through hole 12 will increase in thickness during the electroplating process to avoid being affected by other factors and ensure interlayer conductivity.

[0095] Optionally, the electroplating equipment is a VCP (Vertical Continuous Plating) electroplating equipment.

[0096] Optionally, the first electroplating step is flash plating, which can quickly make the surface copper 13 of the antenna area 15 reach the required thickness and meet the uniformity requirement.

[0097] S6, please refer to Figure 6 and Figure 12 , the antenna area 15 is covered and protected with a dry film 14 .

[0098] Using a conventional circuit pattern transfer process (pre-treatment → lamination → exposure → development), the antenna area 15 is covered with a dry film 14 for protection, and the dry film 14 in the non-antenna area 16 (the remaining area) is developed away to expose the copper surface.

[0099] S7, please refer to Figure 6 and Figure 13 , and perform secondary electroplating.

[0100] Due to the deepness of through-hole 12, the secondary electroplating process utilizes VCP pulse plating equipment with enhanced filling capabilities and improved surface copper 13 uniformity. This ensures that both the through-hole copper 17 thickness and the surface copper 13 thickness in the non-antenna area 16 meet the required thickness, while minimizing the difference between the through-hole copper 17 and the surface copper 13 in the non-antenna area 16. Furthermore, the well-defined through-hole 12 shape, with no narrowing at the orifice, does not affect subsequent drying and plugging processes, ensuring that the resin / solder mask plug is fully filled and void-free.

[0101] Moreover, the extreme difference of the surface copper 13 in the antenna area 15 is not affected by the secondary electroplating, and the extreme difference of the surface copper 13 in the antenna area 15 is more uniform.

[0102] S8, please refer to Figure 6 and Figure 14 , remove the dry film 14.

[0103] The circuit board 10 after secondary electroplating is transferred to a film stripping level to remove the dry film 14 covering the antenna area 15 .

[0104] Afterwards, a dry film may be applied to the surface of the circuit board 10 and subjected to an “exposure-development-etching-stripping” process to obtain circuit patterns of the antenna area 15 and the non-antenna area 16 .

[0105] The beneficial effects of the circuit board processing method provided by the embodiment of the present application are as follows: during the hole filling electroplating, since only blind holes 11 are drilled on the circuit board 10 and no through holes 12 are drilled, the electroplating parameters only need to consider the hole filling depression index requirements of the blind holes 11, and do not need to consider the hole copper 17 index of the through holes 12; therefore, the electroplating parameters can reduce the current density to reduce the thickening amount of the surface copper 13, thereby improving the uniformity of the surface copper 13 after electroplating and reducing the range of the surface copper 13. Since the range of the surface copper 13 generated during the thinning process of the surface copper 13 is positively correlated with the amount of copper reduction, and the thickening amount of the surface copper 13 after the hole filling electroplating is reduced, the range of the surface copper 13 generated during the thinning process of the surface copper 13 is relatively small, reducing the impact of copper reduction on the range of the surface copper 13. After a primary electroplating of through-hole 12, the surface copper 13 in antenna area 15 reaches the required thickness. Compared to reducing copper thickness to achieve the required thickness, this method does not exacerbate the problem of uneven copper thickness in antenna area 15, thereby ensuring uniform antenna dimensions and, in turn, product yield. Subsequently, antenna area 15 is covered with dry film 14, while only the surface copper 13 and through-hole copper 17 thickness are increased in non-antenna area 16 to ensure that the thickness and uniformity of these areas meet the required thickness. Furthermore, the secondary electroplating process does not affect the uniformity of antenna area 15, resulting in improved uniformity.

[0106] Among them, the uniformity of the surface copper 13 has obvious advantages. The thickness of the surface copper 13 in the antenna area 15 is stable at the target copper thickness ±5um, and the thickness of the surface copper 13 in the non-antenna area 16 is stable at the target copper thickness ±8um.

[0107] Since the electroplating process does not require consideration of both the filling of the blind vias 11 and the thickness of the copper 17 of the through holes 12, the parameter adjustment window is large, the fault tolerance is high, and the requirements for the electroplating equipment capacity are reduced, which is more conducive to mass production and cost control.

[0108] The specific steps of the circuit board processing method provided in the embodiment of the present application are as follows:

[0109] For example, a 1.6mm-thick multilayer PCB requires a surface copper thickness of 25±5µm in the antenna area 15, 45±8µm in the non-antenna area 16, and 20µm or greater for the through-hole copper 17. After lamination and assembly, the board is ready for laser drilling. Before laser drilling, the surface copper thickness is controlled to 10±1µm.

[0110] The basic process is: drilling blind holes → copper plating + hole filling electroplating → copper reduction on the entire board → drilling through holes → copper plating + flash plating → dry film exposure and development → pulse electroplating → film stripping → graphic circuit. This new processing method achieves the purpose of local thin copper of the antenna.

[0111] 1) Drilling blind holes: Using laser drilling equipment, the blind hole 11 is drilled according to the supporting laser drilling data. The diameter of the blind hole 11 is designed to be 0.15 mm, the hole depth is designed to be 0.137 mm, and the aspect ratio of the blind hole 11 is designed to be 0.9:1.

[0112] 2) Copper deposition + hole filling electroplating: Use copper deposition equipment to deposit a 0.3-0.5um copper layer on the hole wall of the drilled blind hole 11; after copper deposition, transfer the circuit board 10 to the hole filling electroplating equipment, and fill the blind hole 11 by hole filling electroplating (depression ≤ 30um). The thickness of the surface copper 13 is increased by 35um. At this time, the theoretical thickness of the surface copper 13 is 45±4um.

[0113] 3) Whole-board copper reduction: The circuit board 10 after hole filling and electroplating is subjected to whole-board copper reduction, and the thickness of the surface copper 13 is controlled to be 20±5 μm.

[0114] 4) Drilling through holes: Use mechanical drilling equipment to drill through holes 12. The hole depth of the through holes 12 is 1.6 mm (consistent with the thickness of the circuit board 10). The minimum aperture of the through holes 12 is designed to be 0.225 mm, and the aspect ratio is 7.1:1.

[0115] 5) Copper deposition + flash plating: Using copper deposition equipment, a 0.3-0.5 μm copper layer is deposited on the walls of the drilled through-holes 12. Within 8 hours after copper deposition, the circuit board 10 is transferred to a VCP electroplating machine for flash plating (approximately 8 μm thickening). After flash plating, the thickness of the surface copper 13 is 28 ± 5 μm, meeting the thickness requirement for the surface copper 13 of the antenna area 15. Flash plating also thickens the copper layer deposited on the walls of the through-holes 12 by 3-5 μm to protect the deposited copper layer.

[0116] 6) Dry film exposure and development: Using a conventional circuit pattern transfer process (pre-treatment → film lamination → exposure → development), the antenna area 15 is covered with a dry film 14 for protection, and the dry film 14 in the non-antenna area 16 is developed away to expose the copper surface.

[0117] 7) Pulse Plating: Transfer the PCB, protected with dry film 14 in the antenna area 15, to a VCP pulse plating line to plate the through-hole copper 17 of the through-hole 12 and the surface copper 13 of the non-antenna area 16. The theoretical copper thickness after plating is: through-hole copper 17 of the through-hole 12 is 23-28 μm, and the surface copper 13 of the non-antenna area 16 is 48 ± 8 μm. The thickness of the surface copper 13 of the antenna area 15 remains unchanged at 28 ± 5 μm.

[0118] 8) Film stripping: The plated circuit board 10 is transferred to a film stripping level, and the dry film 14 on the antenna area 15 on the board surface is stripped off.

[0119] 9) Graphic circuit: Use vacuum laminating equipment to stick the dry film to the board surface under vacuum and pressurized conditions and fill the intersection of the copper thickness height difference. Then perform the "exposure-development-etching-film stripping" process to obtain the circuit patterns of the antenna area 15 and the non-antenna area 16.

[0120] After the above processing process, the "antenna local thin copper" circuit can be generated on the board surface of the circuit board 10. The antenna copper thickness of the antenna area 15 is 28±5um, and the circuit copper thickness of the non-antenna area 16 is 48±8um (3um of surface copper 13 loss is reserved for the subsequent process to ensure that the finished surface copper 13 meets the antenna copper thickness of 25±5um in the antenna area 15 and the circuit copper thickness of 45±8um in the non-antenna area 16).

[0121] The second aspect of the present application provides a circuit board 10 , which is processed by the circuit board processing method described in the first aspect.

[0122] The circuit board 10 adopts any one or more embodiments of the above-mentioned circuit board processing method, and thus has the beneficial effects of the above-mentioned embodiments, which will not be described in detail here.

[0123] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A circuit board processing method, characterized in that: include: Drilling blind vias in circuit boards; Plating copper in the blind holes and performing hole-filling electroplating; Thinning the surface copper of the circuit board; drilling through holes in the circuit board; The through hole is copper-plated and electroplated once to ensure that the surface copper thickness of the antenna area meets the requirements; Covering the antenna area with a dry film for protection; Perform secondary electroplating; The dried film is removed.

2. The circuit board processing method according to claim 1, wherein: When performing hole filling electroplating, the current density is 14-16ASF.

3. The circuit board processing method according to claim 1, wherein: The double-sided copper of the circuit board is thinned.

4. The circuit board processing method according to claim 3, wherein: The copper reducing solution used when thinning the surface copper of the circuit board includes sulfuric acid and hydrogen peroxide, wherein the concentration of the sulfuric acid is 100-180g / L and the concentration of the hydrogen peroxide is 20-40g / L.

5. The circuit board processing method according to claim 4, wherein: The copper-reducing solution also includes copper ions, and the concentration of the copper ions is 0-50 g / L.

6. The circuit board processing method according to claim 4, wherein: The temperature used when thinning the surface copper of the circuit board is 30-35°C.

7. The circuit board processing method according to any one of claims 1 to 6, characterized in that: The first electroplating is flash plating; and / or the second electroplating is pulse plating.

8. The circuit board processing method according to any one of claims 1 to 6, characterized in that: The blind holes are formed by laser drilling equipment; and / or the through holes are formed by mechanical drilling equipment.

9. The circuit board processing method according to any one of claims 1 to 6, characterized in that: After the dry film is removed, a vacuum laminating device is used to cover the dry film on the circuit board under vacuum and pressure conditions, filling the intersection of the high and low thickness differences of the surface copper, and performing the "exposure-development-etching-stripping" process to obtain a pattern circuit.

10. A circuit board, characterized in that: The circuit board is processed by the circuit board processing method according to any one of claims 1 to 9.

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