Electroplating method and device for printed circuit board

Abstract

The invention discloses an electroplating method and device for a printed circuit board, and relates to the technical field of printed circuit board preparation. The electroplating method of the printed circuit board comprises the following steps: carrying out primary copper deposition after preparing a through hole; carrying out primary plate surface electroplating on the printed circuit board after primary copper deposition and carrying out resin filling; carrying out surface treatment on the printed circuit board filled with the resin and carrying out secondary copper deposition; cleaning the surface of the printed circuit board after secondary copper deposition and performing secondary board electroplating; a pulse electroplating process is adopted for secondary plate surface electroplating, and a composite pulse waveform is applied to at least one copper cylinder; one cycle period of the composite pulse waveform includes at least two sub-waveforms. According to the invention, the first direct current waveform is applied to the first copper cylinder, the composite pulse waveform is applied to at least one copper cylinder except the first copper cylinder, and the plurality of copper cylinders are controlled to sequentially carry out plate surface electroplating, so that the risk of copper plating layer deficiency in the electroplating process of the printed circuit board is reduced, and the performance and reliability of the printed circuit board are improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of printed circuit board preparation, and in particular to a method and device for electroplating a printed circuit board. Background Art

[0002] With the advent of the 5G era, electronic devices are developing towards high-performance and complex systems. As the foundation of electronic devices, the signal transmission performance and signal integrity of printed circuit boards have become key factors affecting the performance of electronic devices. In order to improve the circuit design flexibility of high-frequency circuit boards, solve the problem of excessive through holes, and enhance the reliability and resistance to cold and hot shocks of high-frequency circuit boards, high-frequency circuit boards use a resin plug hole electroplating filling process (Printed Over Filled Via, POFV) to meet the needs of high-performance applications.

[0003] In order to improve the electroplating capacity, the existing technology generally adopts the new vertical continuous plating (Vertical Continuous Plate, VCP) technology to replace the traditional DC plating method. However, in the VCP technology, when copper is plated on the resin surface covering the plug hole, there is a high proportion of copper plating layer missing problem, which is called "poor capping", such as Figure 1 As shown in the figure, there is a problem of missing copper plating layer at A in the printed circuit board. Poor capping will affect the overall electrical performance of the product and the mounting of components. Therefore, how to reduce the risk of missing copper plating layer during the electroplating process of printed circuit boards has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present invention provides a method and device for electroplating a printed circuit board, so as to reduce the risk of missing a copper plating layer during the electroplating process of the printed circuit board, thereby improving the performance and reliability of the printed circuit board.

[0005] A first aspect of the present invention provides a method for electroplating a printed circuit board, comprising:

[0006] After a through hole is prepared on the printed circuit board, copper is deposited on the through hole to metallize the through hole;

[0007] Performing a board surface electroplating on the printed circuit board after the copper deposition;

[0008] Filling the printed circuit board with resin after the first board surface electroplating;

[0009] Performing surface treatment on the printed circuit board after resin filling;

[0010] Performing secondary copper deposition on the printed circuit board after surface treatment;

[0011] Cleaning the surface of the printed circuit board after the secondary copper deposition;

[0012] The printed circuit board after surface cleaning is subjected to secondary surface electroplating; the secondary surface electroplating adopts a pulse electroplating process, in which a composite pulse waveform is applied to at least one copper cylinder;

[0013] Among them, one cycle period of the composite pulse waveform includes at least two sub-waveforms, and the durations of at least two of the sub-waveforms decrease successively.

[0014] Optionally, when the surface of the printed circuit board after the secondary copper deposition is cleaned, the cleaning solute used for the surface cleaning includes sulfuric acid of a first preset concentration;

[0015] The value range of the first preset concentration C1 is: 0.6%≤C1≤1.4%.

[0016] Optionally, when the surface of the printed circuit board after the secondary copper deposition is cleaned, the surface cleaning is carried out by spraying on both sides, and the flow rate of the spraying on both sides is a first preset flow rate;

[0017] The value range of the first preset flow rate Q1 is: 0.5m 3 / H≤Q1≤1.5m 3 / H.

[0018] Optionally, the printed circuit board after surface cleaning is subjected to secondary board surface electroplating, comprising:

[0019] Controlling the plurality of copper cylinders to sequentially perform secondary board electroplating on the printed circuit board after the surface cleaning;

[0020] When performing secondary board surface electroplating, a first DC waveform is applied to the first copper cylinder, and the composite pulse waveform is applied to at least one of the copper cylinders except the first copper cylinder.

[0021] Optionally, a current ratio between a current density of the first DC waveform and a preset current density is greater than or equal to 1.5:1.

[0022] Optionally, the at least two sub-waveforms include a first sub-waveform and a second sub-waveform in sequence;

[0023] The first sub-waveform includes a first forward pulse waveform and a first reverse pulse waveform;

[0024] The second sub-waveform includes a second forward pulse waveform and a second reverse pulse waveform;

[0025] A preset current ratio of the first forward pulse waveform to the first reverse pulse waveform is greater than a preset current ratio of the second forward pulse waveform to the second reverse pulse waveform.

[0026] Optionally, the at least two sub-waveforms include a first sub-waveform, a second sub-waveform and a third sub-waveform in sequence;

[0027] The first sub-waveform includes a first forward pulse waveform and a first reverse pulse waveform;

[0028] The second sub-waveform includes a second forward pulse waveform and a second reverse pulse waveform;

[0029] The third sub-waveform includes a third forward pulse waveform and a third reverse pulse waveform;

[0030] The preset current ratio of the first forward pulse waveform and the first reverse pulse waveform is greater than the preset current ratio of the second forward pulse waveform and the second reverse pulse waveform; the preset current ratio of the second forward pulse waveform and the second reverse pulse waveform is greater than the preset current ratio of the third forward pulse waveform and the third reverse pulse waveform.

[0031] A second aspect of the present invention provides an electroplating device for a printed circuit board, comprising:

[0032] A primary copper deposition module is used to deposit copper on a through hole after the through hole is prepared on the printed circuit board, so as to metalize the through hole;

[0033] A primary board surface electroplating module, used for performing a primary board surface electroplating on the printed circuit board after the primary copper deposition;

[0034] A resin filling module, used for performing resin filling on the printed circuit board after the board surface is electroplated once;

[0035] A surface treatment module, performing surface treatment on the printed circuit board after resin filling;

[0036] A secondary copper deposition module, used for performing secondary copper deposition on the printed circuit board after surface treatment;

[0037] A surface cleaning module, used for cleaning the surface of the printed circuit board after the secondary copper deposition;

[0038] A secondary board surface electroplating module is used to perform secondary board surface electroplating on the printed circuit board after surface cleaning; the secondary board surface electroplating adopts a pulse electroplating process, in which a composite pulse waveform is applied to at least one copper cylinder;

[0039] Among them, one cycle period of the composite pulse waveform includes at least two sub-waveforms, and the durations of at least two of the sub-waveforms decrease successively.

[0040] Optionally, the board surface electroplating module includes: a copper cylinder and a power generation module;

[0041] The power generation module is used to control the multiple copper cylinders to perform secondary board plating on the printed circuit board after surface cleaning in turn; when performing secondary board plating, the first DC waveform is applied to the first copper cylinder, and the composite pulse waveform is applied to at least one copper cylinder other than the first copper cylinder.

[0042] Optionally, the surface cleaning module is specifically used to clean the surface of the printed circuit board after the secondary copper deposition by spraying on both sides;

[0043] The surface cleaning module includes: a flow meter;

[0044] The flow meter is used to control the flow rate of the spraying on both sides to be a first preset flow rate when cleaning the surface of the printed circuit board after the secondary copper deposition, wherein the first preset flow rate Q1 satisfies 0.5m 3 / H≤Q1≤1.5m 3 / H.

[0045] In this embodiment, after preparing a through hole on the printed circuit board, copper is deposited once on the through hole to metalize the through hole, and the printed circuit board after the copper deposition is electroplated once to form a second conductive layer in the through hole, and the printed circuit board after the surface electroplating is filled with resin to improve the conductive performance and connection reliability of the through hole, and the printed circuit board after the resin filling is surface treated to roughen the surface of the resin plug hole and improve the bonding force between the copper deposition layer on the surface of the resin plug hole and the resin, and the printed circuit board after the surface treatment is subjected to secondary copper deposition to further improve the conductive performance and connection reliability of the through hole, and the surface of the printed circuit board after the secondary copper deposition is cleaned to remove the surface of the printed circuit board. The oil, pollutants and oxides on the surface of the printed circuit board are removed, the activity of the surface of the printed circuit board is improved, which is beneficial to the subsequent electroplating operation, and the printed circuit board after the surface cleaning is subjected to secondary board surface electroplating, wherein the secondary board surface electroplating adopts a pulse electroplating process, and a composite pulse waveform is applied to at least one copper cylinder in the pulse electroplating process, and one cycle of the composite pulse waveform includes at least two sub-waveforms, and the duration of at least two sub-waveforms decreases successively, thereby achieving a more uniform and accurate distribution of the plating thickness, ensuring the quality of the POFV layer formed on the chemical copper layer on the surface of the resin plug hole of the printed circuit board, thereby reducing the risk of missing copper plating layer during the electroplating process of the printed circuit board, and improving the performance and reliability of the printed circuit board.

[0046] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0048] Figure 1 It is a physical picture of the missing copper plating layer of the printed circuit board existing in the prior art;

[0049] Figure 2 It is a schematic flow chart of a method for electroplating a printed circuit board provided in the first embodiment of the present invention;

[0050] Figure 3 It is a schematic diagram of a process flow of an electroplating process for a printed circuit board provided in the first embodiment of the present invention;

[0051] Figure 4 It is a schematic diagram of a process for cleaning the surface of a printed circuit board provided in the first embodiment of the present invention;

[0052] Figure 5 It is a structural schematic diagram of an oil removal tank provided in Embodiment 1 of the present invention;

[0053] Figure 6 It is a schematic cross-sectional structure diagram of an oil removal tank provided in the first embodiment of the present invention;

[0054] Figure 7 is a structural schematic diagram of a composite pulse waveform provided in Embodiment 1 of the present invention;

[0055] Figure 8 It is a structural schematic diagram of a pulse waveform used in secondary plate surface electroplating provided by the related technology;

[0056] Fig. 9 is a structural schematic diagram of a first DC waveform provided in Embodiment 1 of the present invention;

[0057] Fig.10 It is a structural schematic diagram of a DC waveform used in secondary plate surface electroplating provided by the related technology;

[0058] Fig.11 is a schematic structural diagram of another composite pulse waveform provided in Embodiment 1 of the present invention;

[0059] Fig.12 It is a structural schematic diagram of a printed circuit board electroplating device provided in the second embodiment of the present invention;

[0060] Fig.13 It is a structural schematic diagram of a surface cleaning module provided in Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0061] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0062] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0063] Embodiment 1

[0064] Figure 2 is a schematic flow chart of a method for electroplating a printed circuit board provided in Embodiment 1 of the present invention, Figure 3 1 is a schematic diagram of a process flow of a printed circuit board electroplating process provided by the first embodiment of the present invention. This embodiment is applicable to the case of electroplating a printed circuit board. The method can be performed by an electroplating device for a printed circuit board. Figure 2 and Figure 3 As shown, the electroplating method of the printed circuit board may include:

[0065] S101, after preparing through holes on the printed circuit board, copper deposition is performed on the through holes to metallize the through holes.

[0066] Among them, through-holes can be specifically understood as holes formed on printed circuit boards by mechanical or laser drilling processes for connecting different layers of circuits. Primary copper plating can be specifically understood as a conductive layer formed by chemical reaction deposition on the surface of the insulating layer on the inner wall of the through-hole of the printed circuit board, making the inner wall of the through-hole of the circuit board conductive and ensuring the normal conduction of electrical signals.

[0067] Specifically, before the through hole is electroplated, a through hole can be formed on the printed circuit board by a process such as mechanical or laser drilling for subsequent circuit connection. After the through hole is formed, the inside of the through hole is metallized by a copper deposition process. For example, a chemical method or an electrochemical method can be used to deposit copper on the inner wall of the through hole to ensure that the through hole has good electrical conductivity and realize the connection between different circuit layers. The thickness-to-diameter ratio of the through hole in the printed circuit board can be 8:1-9:1, and the thickness of the conductive layer formed on the inner wall of the through hole by a single copper deposition can include 0.3um-0.5um, which can be determined according to actual conditions, and the present invention is not specifically limited here.

[0068] S102, performing a board surface electroplating on the printed circuit board after the copper deposition.

[0069] The first board surface electroplating can be specifically understood as a process of uniformly depositing a metal layer on the entire surface of the printed circuit board. Specifically, the printed circuit board after the first copper deposition is subjected to a first board surface electroplating to form a second conductive layer in the through hole, thereby enhancing the conductive performance of the through hole and improving the conductive performance and signal transmission efficiency of the printed circuit board.

[0070] S103, filling the printed circuit board with resin after the first board surface electroplating.

[0071] Among them, resin filling can be specifically understood as filling the through-holes on the printed circuit board after the board surface is electroplated once. Specifically, a layer of special plugging resin is coated inside the through-holes forming the conductive layer to fill the internal voids of the through-holes, prevent the electroplating solution from entering the through-holes, and keep the shape and structure of the through-holes intact. After that, the printed circuit board is placed in the electroplating tank containing the resin filling solution, and the plugging resin is filled with metal through appropriate current and process parameters to achieve the filling of the through-holes, improve the conductivity and connection reliability of the through-holes, and ensure the structural integrity of the through-holes.

[0072] S104, performing surface treatment on the printed circuit board after resin filling.

[0073] Among them, surface treatment can be specifically understood as roughening the surface of the printed circuit board after resin filling. Specifically, before the secondary copper deposition of the printed circuit board after the resin plugging, the focusing structure of the resin itself can be interrupted by a swelling agent to make the resin expand and soften, and the resin can be treated under high temperature alkaline conditions by the oxidation reaction of permanganate to roughen the surface of the resin plugging hole and improve the bonding force between the copper deposition layer on the surface of the resin plugging hole and the resin. However, the inconsistent roughness of the surface of the resin plugging hole will lead to uneven bonding between the resin and the copper deposition layer on the surface of the resin plugging hole, and the copper deposition layer may not be firmly attached, and it is easy to fall off and peel off locally, thereby affecting the conduction performance of the through hole and the stability and reliability of the printed circuit board.

[0074] S105, performing secondary copper deposition on the surface treated printed circuit board.

[0075] Among them, the secondary copper deposition can be specifically understood as depositing a copper layer on the surface of the resin plug hole on the printed circuit board after surface treatment. Specifically, the surface-treated printed circuit board is placed in an electrolyte containing copper ions, and a uniform copper layer is deposited on the surface of the resin plug hole through appropriate current and process parameters, so as to fill the gaps that are not completely filled inside the resin plug hole or the uneven surface of the resin plug hole, further improving the conductivity and connection reliability of the through hole.

[0076] S106, cleaning the surface of the printed circuit board after the secondary copper deposition.

[0077] like Figure 4As shown, the VCP electroplating line adopts an integrated steel belt return type transmission, and different tanks are separated by double gear water wheels and inlet and outlet reflux. The pre-treatment section process design is: board entry → (inlet reflux) → degreasing → (outlet reflux) → water washing * 1 (overflow) → water washing * 2 → pickling → copper tank reflux → copper plating entrance. Specifically, before the secondary board surface electroplating of the printed circuit board after the copper layer is deposited on the surface of the resin plug hole, the printed circuit board needs to be surface cleaned, and the printed circuit board is sent into the interior of the VCP equipment through the feeder, and then the linear pusher feeding mechanism inside the VCP equipment is used to sequentially send the PCB board into the degreasing tank, the water washing tank and the pickling prepreg tank to perform pre-treatment before the secondary board surface electroplating of the printed circuit board. Among them, surface cleaning can be specifically understood as using a solvent or a detergent to clean the surface of the printed circuit board in the degreasing tank to remove oil and pollutants on the surface of the printed circuit board. For example, the cleaning solute used for surface cleaning can be sulfuric acid and copper sulfate accumulated during the cleaning process. After that, the printed circuit board surface is washed in a water washing tank to thoroughly clean the surface of the printed circuit board and remove residual solvents and detergents. In the pickling prepreg tank, the acid solution is used to remove the oxide on the surface of the printed circuit board to improve the activity of the printed circuit board surface, which is beneficial to the subsequent electroplating operation. Figure 5 As shown, the degreasing tank adopts an upper and lower tank design to effectively save space, where the upper tank 01 is the main reaction tank and the lower tank 02 is the temporary storage tank. The main tank 01 flows back through the inlet and outlet and overflows from the side to the auxiliary tank 02, and the auxiliary tank 02 pumps the tank liquid back to the main tank through the spray pipe through the circulation pump 03. Figure 6 As shown, the degreasing, water washing and pickling pre-impregnation are designed as a two-side spraying method, the printed circuit board is in a suspended state, and the liquid medicine directly acts on the surface of the printed circuit board from the circulation pump 03 through the dense high-pressure nozzles 04 arranged vertically. It can be understood that the upper and lower trough reflux design may aggravate the corrosion of the chemical copper layer on the surface of the resin plug hole of the printed circuit board due to the large number of bubbles generated during the high drop impact, the strong spraying of the degreasing and pickling pre-impregnation on the surface of the printed circuit board, and the long stagnation time caused by the reflux and non-immersion design. The main components that corrode the chemical copper layer are oxygen, acid and copper ions in the air, which leads to the loss of the copper plating layer during the electroplating process of the printed circuit board.

[0078] Optionally, when performing surface cleaning on the printed circuit board after secondary copper deposition, the cleaning solute used for surface cleaning includes sulfuric acid of a first preset concentration;

[0079] The value range of the first preset concentration C1 is: 0.6%≤C1≤1.4%.

[0080] Specifically, the concentration C1 of sulfuric acid used for surface cleaning is in the range of 0.6%≤C1≤1.4%. Sulfuric acid of appropriate concentration can effectively control the acidic reaction in the medicine tank to reduce corrosion to the chemical copper layer, thereby ensuring effective cleaning of the surface of the printed circuit board while reducing the risk of missing copper plating layer during the electroplating process of the printed circuit board, thereby improving the performance and reliability of the printed circuit board.

[0081] Optionally, when performing surface cleaning on the printed circuit board after secondary copper deposition, the surface cleaning adopts a spraying method on both sides, and the flow rate of the spraying on both sides is a first preset flow rate;

[0082] The value range of the first preset flow rate Q1 is: 0.5m 3 / H≤Q1≤1.5m 3 / H.

[0083] Specifically, the surface is cleaned by spraying on both sides, wherein the spray flow rate Q1 of sulfuric acid on both sides is in the range of 0.5m 3 / H≤Q1≤1.5m 3 / H, appropriate sulfuric acid flow rate can help reduce the impact of surface cleaning treatment on the copper layer. In the pre-treatment before secondary surface electroplating of the printed circuit board, it can reduce the damage and peeling of the copper layer and protect the integrity of the copper layer. This ensures that the surface of the printed circuit board is effectively cleaned while reducing the risk of copper layer loss during the electroplating process of the printed circuit board, thereby improving the performance and reliability of the printed circuit board.

[0084] It is also understandable that after the copper layer is deposited on the surface of the resin plug hole on the printed circuit board, it needs to be transported and waited, and the deposited chemical copper layer will be oxidized to a certain extent, resulting in the loss of the copper plating layer, affecting the quality and stability of the printed circuit board. Therefore, the standing time between the copper layer deposited on the surface of the resin plug hole on the printed circuit board and the secondary surface electroplating of the printed circuit board is reduced to reduce the influence of the oxidation-reduction reaction of the chemical copper layer and reduce the corrosion of the chemical copper layer, thereby reducing the risk of the loss of the copper plating layer during the electroplating process of the printed circuit board. Exemplarily, the standing time between the copper layer deposited on the surface of the resin plug hole on the printed circuit board and the secondary surface electroplating of the printed circuit board is shortened from no more than 6 hours to no more than 4 hours to reduce the influence of the oxidation-reduction reaction of the chemical copper layer, thereby reducing the risk of the loss of the copper plating layer during the electroplating process of the printed circuit board.

[0085] S107, performing secondary board surface electroplating on the printed circuit board after surface cleaning.

[0086] The secondary plate surface electroplating adopts a pulse electroplating process, in which a composite pulse waveform is applied to at least one copper cylinder.

[0087] like Figure 7 As shown, one cycle of the composite pulse waveform 1 includes at least two sub-waveforms, and the durations of the at least two sub-waveforms decrease successively.

[0088] Specifically, the copper cylinder is used to perform secondary electroplating on the surface of the printed circuit board after surface cleaning, so as to form a POFV layer on the chemical copper layer on the surface of the resin plug hole of the printed circuit board, ensuring that both ends of the through hole form a flat welding surface, which not only realizes the internal conduction function of the through hole, but also allows the through hole to be directly used for welding various components such as ball grid array (BGA), rather than just being used as a simple through hole or plug-in hole. Among them, the secondary board surface electroplating adopts a pulse electroplating process. Pulse electroplating can be specifically understood as electroplating with a pulse power supply instead of a DC power supply. During the electroplating process, the electro-deposition process can be changed in a wide range by controlling parameters such as waveform, frequency, on-off ratio and average current density, so as to obtain a coating with certain characteristics in a certain plating solution.

[0089] Figure 8 It is a structural schematic diagram of a pulse waveform used in secondary board surface electroplating in the related technology. The specific parameters of the pulse waveform are shown in Table 1 below.

[0090] Table 1 Parameters of pulse waveform in related art

[0091] Cycle / Current Positive Reverse Cycle Ratio 40 2 Current ratio 100 -240

[0092] The inventor has discovered through research that in the pulse waveform used for secondary board surface electroplating in the related art, a reverse pulse is introduced after the forward pulse electroplating. The forward pulse lasts longer than the reverse pulse, and the reverse pulse amplitude is greater than the forward pulse. The highly uneven anode current distribution caused by the large-amplitude, short-time reverse pulse waveform can dissolve the protruding parts of the plating and make its surface smoother. However, when the current density of the reverse pulse waveform is too large, it will affect the chemical copper layer on the surface of the resin plug hole of the printed circuit board, resulting in the loss of the copper plating layer.

[0093] It can be understood that by applying the composite pulse waveform 1 to at least one copper cylinder, that is, the composite pulse waveform 1 can be applied to multiple copper cylinders respectively, and at least two sub-waveforms with decreasing durations in the composite pulse waveform 1 are combined into one cycle. For example, continue to refer to Figure 7The first sub-waveform 11 and the second sub-waveform 12 in the composite pulse waveform 1 are combined into a cycle, wherein the duration of the first sub-waveform is 84ms, and the duration of the second sub-waveform is 63ms. The secondary board surface electroplating is performed in sequence through multiple composite pulse waveforms, and the deposition process can be gradually regulated by the sub-waveform design with decreasing duration. By gradually reducing the duration of the sub-waveform, the deposition rate can be finely controlled to achieve a more uniform and accurate distribution of the coating thickness, ensuring that the copper layer thickness of the entire surface is uniform, thereby reducing the risk of missing copper plating during the electroplating process of the printed circuit board and improving the performance and reliability of the printed circuit board.

[0094] Optionally, the printed circuit board after surface cleaning is subjected to secondary surface electroplating, including: controlling multiple copper cylinders to sequentially perform secondary surface electroplating on the printed circuit board after surface cleaning; when performing the secondary surface electroplating, applying a first DC waveform to the first copper cylinder, and applying a composite pulse waveform to at least one copper cylinder other than the first copper cylinder.

[0095] Specifically, the printed circuit board after surface cleaning is subjected to secondary board electroplating in sequence through multiple copper cylinders, and the first copper cylinder is applied with the following Fig. 9 The first DC waveform 2 shown in FIG. 1 is helpful for fast and stable copper plating, ensuring that a uniform copper layer is formed in a short time. Figure 7 The composite pulse waveform 1 shown, that is, multiple composite pulse waveforms in multiple copper cylinders can be used in sequence to perform secondary board electroplating on the printed circuit board multiple times, so that after a uniform copper layer is formed by the first DC waveform 2, the surface of the copper layer is trimmed by at least one composite pulse waveform 1 to reduce the surface roughness and defects of the copper layer, so as to form a smoother and denser structure on the chemical copper layer on the surface of the resin plug hole of the printed circuit board, thereby improving the quality and performance of the copper plating layer.

[0096] Optionally, a current ratio of a current density of the first DC waveform to a preset current density is greater than or equal to 1.5:1.

[0097] Among them, the preset current density can be specifically understood as the initial current density value set according to specific process requirements and goals when performing secondary surface electroplating of the printed circuit board. For example, the preset current density can be 18ASF. During the electroplating process, the current density directly affects the thickness and quality of the coating. A larger current density means that more copper ions are deposited on the surface of the chemical copper layer on the surface of the resin plug hole of the printed circuit board, thereby forming a thicker copper layer.

[0098] Specifically, Fig.10 It is a structural schematic diagram of the DC waveform used in secondary board surface electroplating in the related art, and the specific parameters of the DC waveform are shown in Table 2 below.

[0099] Table 2 Parameters of DC waveform in related technology

[0100] Positive Reverse Cycle Ratio 100 0 Current ratio 100 0

[0101] The inventor has found that the current density of the DC waveform and the current density of the preset current density are 1:1. At this time, the current density of the DC waveform is 18ASF. The copper layer formed during the copper plating process is relatively thin. Therefore, when the copper plating layer is trimmed by the composite pulse waveform, it is easy to cause the copper plating layer to be missing, causing the capping problem. In order to improve the problem of the thin copper plating layer formed by DC waveform electroplating, the following method is used: Fig. 9 The first DC waveform 2 shown is used to electroplate the printed circuit board. The specific parameters of the first DC waveform 2 are shown in Table 3 below.

[0102] Table 3 Parameters of the first DC waveform 2

[0103] Positive Reverse Cycle Ratio 100 0 Current ratio 150 0

[0104] The current ratio of the current density of the first DC waveform 2 to the preset current density is 1.5:1. At this time, the current density of the first DC waveform 2 is 27ASF, and the maximum current density of the composite pulse waveform 1 is 18ASF. The current density of the first DC waveform 2 is relatively large, so a thicker copper layer will be formed during the copper plating process. The maximum current density of the composite pulse waveform 1 is relatively small, which avoids excessive current density during the trimming of the copper plating layer, thereby reducing the risk of missing copper plating layer. By setting the current ratio of the current density of the first DC waveform 2 to the preset current density to be greater than or equal to 1.5:1, the required copper layer thickness can be quickly formed, thereby improving production efficiency and reducing the risk of missing copper plating layer during the electroplating process of the printed circuit board, thereby improving the performance and reliability of the printed circuit board.

[0105] In an optional embodiment, continue to refer to Figure 7 , at least two sub-waveforms include a first sub-waveform 11 and a second sub-waveform 12 in sequence; the first sub-waveform 11 includes a first forward pulse waveform 111 and a first reverse pulse waveform 112; the second sub-waveform 12 includes a second forward pulse waveform 121 and a second reverse pulse waveform 122; the preset current ratio of the first forward pulse waveform 111 and the first reverse pulse waveform 112 is greater than the preset current ratio of the second forward pulse waveform 121 and the second reverse pulse waveform 122.

[0106] At this time, specific parameters of the composite pulse waveform 1 are shown in Table 4 below.

[0107] Table 4 Parameters of composite pulse waveform

[0108] Positive Reverse Positive Reverse Cycle Ratio 80 4 60 3 Current ratio 100 -200 100 -180

[0109] Specifically, the positive pulse waveform can be understood as a waveform in which the pulse current is a positive current, and the negative pulse waveform can be understood as a waveform in which the pulse current is a negative current. In the positive pulse waveform stage, copper is deposited normally on the printed circuit board by electroplating, and in the negative pulse waveform stage, the high current area is dissolved by anodic dissolution, thereby playing a leveling role to improve the distribution of the coating thickness and make the coating uniform. Continuing to refer to Table 4, the period ratio of the duration of the first forward pulse waveform 111 to the preset duration is 0.8:1, wherein the preset duration can be specifically understood as the duration of the initial pulse set according to specific process requirements and goals when the printed circuit board is subjected to secondary surface electroplating using the pulse electroplating process. Exemplarily, the preset duration can be 100ms, that is, the duration of the first forward pulse waveform 111 is 80ms, and the current density is 18ASF; the duration of the first reverse pulse waveform 112 is 4ms, and the current density is -36ASF; the duration of the second forward pulse waveform 121 is 60ms, and the current density is 18ASF; the duration of the second reverse pulse waveform 122 is 3ms, and the current density is -32.4ASF, wherein the forward pulse waveform in the same sub-waveform has a longer duration than the reverse pulse waveform, and the current density of the reverse pulse waveform is greater than the current density of the forward pulse waveform. It can be understood that the large amplitude , the highly uneven anode current distribution caused by the short-time reverse pulse waveform can dissolve the protruding parts of the plating layer to make its surface smoother. However, when the current density of the reverse pulse waveform is too large, it will affect the chemical copper layer on the surface of the resin plug hole of the printed circuit board, resulting in the loss of the copper plating layer. Therefore, by reducing the current density of the second reverse pulse waveform 122, the preset current ratio of the first forward pulse waveform 111 and the first reverse pulse waveform 112 is 2:1, and the preset current ratio of the second forward pulse waveform 121 and the second reverse pulse waveform 122 is 1.8:1, so that the preset current ratio of the first sub-waveform 11 is greater than the preset current ratio of the second sub-waveform 12, which effectively avoids the loss of the copper plating layer caused by the excessive current density of the reverse pulse waveform. At the same time, compared with the single pulse waveform, the composite pulse waveform prolongs the copper plating time, ensures the quality of the POFV layer formed on the chemical copper layer on the surface of the resin plug hole of the printed circuit board, thereby improving the performance and reliability of the printed circuit board.

[0110] In another optional embodiment, if Fig.11As shown, at least two sub-waveforms include a first sub-waveform 11, a second sub-waveform 12 and a third sub-waveform 13 in sequence; the first sub-waveform 11 includes a first forward pulse waveform 111 and a first reverse pulse waveform 112; the second sub-waveform 12 includes a second forward pulse waveform 121 and a second reverse pulse waveform 122; the third sub-waveform 13 includes a third forward pulse waveform 131 and a third reverse pulse waveform 132; the preset current ratio of the first forward pulse waveform 111 and the first reverse pulse waveform 112 is greater than the preset current ratio of the second forward pulse waveform 121 and the second reverse pulse waveform 122; the preset current ratio of the second forward pulse waveform 121 and the second reverse pulse waveform 122 is greater than the preset current ratio of the third forward pulse waveform 131 and the third reverse pulse waveform 132.

[0111] At this time, the specific parameters of the composite pulse waveform are shown in Table 5 below.

[0112] Table 5 Parameters of composite pulse waveform

[0113] Positive Reverse Positive Reverse Positive Reverse Cycle Ratio 80 4 60 3 40 2 Current ratio 100 -200 100 -180 100 -150

[0114] Specifically, referring to Table 5, the duration of the first forward pulse waveform 111 is 80ms, and the current density is 18ASF; the duration of the first reverse pulse waveform 112 is 4ms, and the current density is -36ASF; the duration of the second forward pulse waveform 121 is 60ms, and the current density is 18ASF; the duration of the second reverse pulse waveform 122 is 3ms, and the current density is -32.4ASF; the duration of the third forward pulse waveform 131 is 40ms, and the current density is 18ASF; the duration of the third reverse pulse waveform 132 is 2ms, and the current density is -27ASF. Therefore, the preset currents of the first forward pulse waveform 111 and the first reverse pulse waveform 112 are The preset current ratio of the second forward pulse waveform 121 and the second reverse pulse waveform 122 is 2:1, the preset current ratio of the third forward pulse waveform 131 and the third reverse pulse waveform 132 is 1.5:1, and by setting the preset current ratio of the first sub-waveform 11 to be greater than the preset current ratio of the second sub-waveform 12, and the preset current ratio of the second sub-waveform 12 to be greater than the preset current ratio 13 of the third sub-waveform, the loss of the copper plating layer caused by the excessive current density of the reverse pulse waveform is effectively avoided. At the same time, compared with the single pulse waveform, the composite pulse waveform prolongs the copper plating time, ensures the quality of the POFV layer formed on the chemical copper layer on the surface of the resin plug hole of the printed circuit board, thereby improving the performance and reliability of the printed circuit board.

[0115] In another optional embodiment, the printed circuit board is subjected to secondary surface electroplating after surface cleaning, and further includes: applying a second DC waveform to the last copper cylinder. Specifically, the copper layer surface formed after the first DC waveform electroplating and the composite pulse waveform trimming is electroplated again by the second DC waveform to make the copper layer surface smoother and more uniform, thereby improving its appearance.

[0116] In this embodiment, after preparing a through hole on the printed circuit board, copper is deposited once on the through hole to metalize the through hole, and the printed circuit board after the copper deposition is electroplated once to form a second conductive layer in the through hole, and the printed circuit board after the surface electroplating is filled with resin to improve the conductive performance and connection reliability of the through hole, and the printed circuit board after the resin filling is surface treated to roughen the surface of the resin plug hole and improve the bonding force between the copper deposition layer on the surface of the resin plug hole and the resin, and the printed circuit board after the surface treatment is subjected to secondary copper deposition to further improve the conductive performance and connection reliability of the through hole, and the surface of the printed circuit board after the secondary copper deposition is cleaned to remove the surface of the printed circuit board. The oil, pollutants and oxides on the surface of the printed circuit board are removed, the activity of the surface of the printed circuit board is improved, which is beneficial to the subsequent electroplating operation, and the printed circuit board after the surface cleaning is subjected to secondary board surface electroplating, wherein the secondary board surface electroplating adopts a pulse electroplating process, and a composite pulse waveform is applied to at least one copper cylinder in the pulse electroplating process, and one cycle of the composite pulse waveform includes at least two sub-waveforms, and the duration of at least two sub-waveforms decreases successively, thereby achieving a more uniform and accurate distribution of the plating thickness, ensuring the quality of the POFV layer formed on the chemical copper layer on the surface of the resin plug hole of the printed circuit board, thereby reducing the risk of missing copper plating layer during the electroplating process of the printed circuit board, and improving the performance and reliability of the printed circuit board.

[0117] Embodiment 2

[0118] Fig.12 Schematic diagram of the structure of a printed circuit board electroplating device provided in the second embodiment of the present invention, which can implement the printed circuit board electroplating method provided in the embodiment of the present invention. Fig.12 As shown, the device includes: a primary copper deposition module 201, a primary board electroplating module 202, a resin filling module 203, a surface treatment module 204, a secondary copper deposition module 205, a surface cleaning module 206 and a secondary board electroplating module 207. The specific structure of the device is as follows:

[0119] The primary copper deposition module 201 is used to perform a primary copper deposition after a through hole is prepared on a printed circuit board to metallize the through hole.

[0120] The primary board surface electroplating module 202 is used to perform a primary board surface electroplating on the printed circuit board after the primary copper deposition.

[0121] The resin filling module 203 is used to fill the printed circuit board with resin after the board surface is electroplated once.

[0122] The surface treatment module 204 performs surface treatment on the printed circuit board after resin filling.

[0123] The secondary copper deposition module 205 is used for performing secondary copper deposition on the printed circuit board after resin filling.

[0124] The surface cleaning module 206 is used to clean the surface of the printed circuit board after the secondary copper deposition.

[0125] The secondary board surface electroplating module 207 is used to perform secondary board surface electroplating on the printed circuit board after the surface cleaning.

[0126] The secondary plate surface electroplating adopts a pulse electroplating process, in which a composite pulse waveform is applied to at least one copper cylinder.

[0127] Among them, one cycle of the composite pulse waveform includes at least two sub-waveforms, and the durations of the at least two sub-waveforms decrease successively.

[0128] In an optional embodiment of the present invention, the secondary board surface electroplating module 207 includes: a copper cylinder and a power generation module; the power generation module is used to control multiple copper cylinders to sequentially perform secondary board surface electroplating on the printed circuit board after surface cleaning; when performing secondary board surface electroplating, a first DC waveform is applied to the first copper cylinder, and a composite pulse waveform is applied to at least one copper cylinder other than the first copper cylinder.

[0129] In an optional embodiment of the present invention, the surface cleaning module 206 is specifically used to clean the surface of the printed circuit board after the secondary copper deposition by spraying on both sides. Fig.13 As shown, the surface cleaning module 206 includes: a flow meter 2061; the flow meter 2061 is used to control the flow of the spray on both sides to be a first preset flow when cleaning the surface of the printed circuit board after the secondary copper deposition, wherein the first preset flow Q1 satisfies 0.5m 3 / H≤Q1≤1.5m3 / H.

[0130] The above-mentioned electroplating device for printed circuit boards can execute the electroplating method for printed circuit boards provided in any embodiment of the present invention, and has functional modules and beneficial effects corresponding to the execution method. For technical details not described in detail in this embodiment, please refer to the electroplating method for printed circuit boards provided in any embodiment of the present invention.

[0131] Since the electroplating device for printed circuit boards introduced above is a device that can perform the electroplating method for printed circuit boards in the embodiment of the present invention, based on the electroplating method for printed circuit boards introduced in the embodiment of the present invention, the technical personnel in the field can understand the specific implementation of the electroplating device for printed circuit boards in this embodiment and its various variations, so how the electroplating device for printed circuit boards implements the electroplating method for printed circuit boards in the embodiment of the present invention is not described in detail here. As long as the technical personnel in the field implement the device used by the electroplating method for printed circuit boards in the embodiment of the present invention, it belongs to the scope of protection of this application.

[0132] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0133] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for electroplating a printed circuit board, characterized in that: include: After a through hole is prepared on the printed circuit board, copper is deposited on the through hole to metallize the through hole; Performing a board surface electroplating on the printed circuit board after the copper deposition; Filling the printed circuit board with resin after the first board surface electroplating; Performing surface treatment on the printed circuit board after resin filling; Performing secondary copper deposition on the printed circuit board after surface treatment; Cleaning the surface of the printed circuit board after the secondary copper deposition; Performing secondary board surface electroplating on the printed circuit board after surface cleaning; The secondary plate surface electroplating adopts a pulse electroplating process, in which a composite pulse waveform is applied to at least one copper cylinder; Among them, one cycle period of the composite pulse waveform includes at least two sub-waveforms, and the durations of at least two of the sub-waveforms decrease successively.

2. The electroplating method of a printed circuit board according to claim 1, characterized in that: When the surface of the printed circuit board after the secondary copper deposition is cleaned, the cleaning solute used for the surface cleaning includes sulfuric acid of a first preset concentration; The value range of the first preset concentration C1 is: 0.6%≤C1≤1.4%.

3. The electroplating method of a printed circuit board according to claim 1, characterized in that: When the surface of the printed circuit board after the secondary copper deposition is cleaned, the surface cleaning is carried out by spraying on both sides, and the flow rate of the spraying on both sides is a first preset flow rate; The value range of the first preset flow rate Q1 is: 0.5m 3 / H≤Q1≤1.5m 3 / H.

4. The electroplating method for a printed circuit board according to claim 1, characterized in that: The printed circuit board after surface cleaning is subjected to secondary board surface electroplating, comprising: Controlling the plurality of copper cylinders to sequentially perform secondary board electroplating on the printed circuit board after the surface cleaning; When performing secondary board surface electroplating, a first DC waveform is applied to the first copper cylinder, and the composite pulse waveform is applied to at least one of the copper cylinders except the first copper cylinder.

5. The electroplating method for a printed circuit board according to claim 4, characterized in that: A current ratio of a current density of the first DC waveform to a preset current density is greater than or equal to 1.5:

1.

6. The electroplating method for a printed circuit board according to claim 1, characterized in that: The at least two sub-waveforms include a first sub-waveform and a second sub-waveform in sequence; The first sub-waveform includes a first forward pulse waveform and a first reverse pulse waveform; The second sub-waveform includes a second forward pulse waveform and a second reverse pulse waveform; A preset current ratio of the first forward pulse waveform to the first reverse pulse waveform is greater than a preset current ratio of the second forward pulse waveform to the second reverse pulse waveform.

7. The electroplating method of a printed circuit board according to claim 1, characterized in that: The at least two sub-waveforms include a first sub-waveform, a second sub-waveform and a third sub-waveform in sequence; The first sub-waveform includes a first forward pulse waveform and a first reverse pulse waveform; The second sub-waveform includes a second forward pulse waveform and a second reverse pulse waveform; The third sub-waveform includes a third forward pulse waveform and a third reverse pulse waveform; A preset current ratio of the first forward pulse waveform to the first reverse pulse waveform is greater than a preset current ratio of the second forward pulse waveform to the second reverse pulse waveform; A preset current ratio of the second forward pulse waveform to the second reverse pulse waveform is greater than a preset current ratio of the third forward pulse waveform to the third reverse pulse waveform.

8. A printed circuit board electroplating device, characterized in that: include: A primary copper deposition module is used to deposit copper on a through hole after the through hole is prepared on the printed circuit board, so as to metalize the through hole; A primary board surface electroplating module, used for performing a primary board surface electroplating on the printed circuit board after the primary copper deposition; A resin filling module, used for performing resin filling on the printed circuit board after the board surface is electroplated once; A surface treatment module, performing surface treatment on the printed circuit board after resin filling; A secondary copper deposition module, used for performing secondary copper deposition on the printed circuit board after surface treatment; A surface cleaning module, used for cleaning the surface of the printed circuit board after the secondary copper deposition; A secondary board surface electroplating module, used for performing secondary board surface electroplating on the printed circuit board after surface cleaning; The secondary plate surface electroplating adopts a pulse electroplating process, in which a composite pulse waveform is applied to at least one copper cylinder; Among them, one cycle period of the composite pulse waveform includes at least two sub-waveforms, and the durations of at least two of the sub-waveforms decrease successively.

9. The electroplating device for a printed circuit board according to claim 8, characterized in that: The secondary plate surface electroplating module comprises: a copper cylinder and a power generation module; The power generation module is used to control the multiple copper cylinders to perform secondary board plating on the printed circuit board after surface cleaning in turn; when performing secondary board plating, the first DC waveform is applied to the first copper cylinder, and the composite pulse waveform is applied to at least one copper cylinder other than the first copper cylinder.

10. The electroplating device for a printed circuit board according to claim 8, characterized in that: The surface cleaning module is specifically used to clean the surface of the printed circuit board after the secondary copper deposition by spraying on both sides; The surface cleaning module includes: a flow meter; The flow meter is used to control the flow rate of the spraying on both sides to be a first preset flow rate when cleaning the surface of the printed circuit board after the secondary copper deposition, wherein the first preset flow rate Q1 satisfies 0.5m 3 / H≤Q1≤1.5m 3 / H.

Images