Preparation method of circuit board with through hole with depth-to-width ratio greater than 8: 1

Abstract

The invention discloses a preparation method of a circuit board with a through hole with the depth-to-width ratio larger than 8: 1. The preparation method comprises the following steps: providing a substrate to be plated; sputtering metal to the inner wall of the through hole to form a first conductive layer; the substrate on which the first conducting layer is formed is placed in chemical plating equipment, a second conducting layer is formed on the substrate, and the second conducting layer is a continuous layer covering the first conducting layer, the area, not covered by the first conducting layer, of the inner wall of the through hole and at least one surface; the substrate is placed in electroplating equipment to form a third conductive layer, and the third conductive layer covers the second conductive layer and fills the through hole; etching and removing all the conductive layer in an area which is not covered by the patterned mask on the substrate, wherein the conductive layer below the mask forms a circuit; wherein the line width and the line spacing of at least a part of the lines are respectively less than 35 [mu] m. According to the manufacturing method, the thin circuit can be manufactured on the micro-through-hole substrate with the depth-to-width ratio larger than 8: 1 at low cost, and the high-density circuit board is obtained.

Description

[0001] This application is a divisional application of the invention with application number 2024104941370 filed on April 24, 2024. Technical Field

[0002] The invention belongs to the field of circuit board preparation, and in particular relates to a method for preparing a circuit board having a through hole with a depth-to-width ratio greater than 8:1. Background Art

[0003] The proportion of advanced packaging in the semiconductor industry has been steadily increasing, and its development is closely related to the evolution of through-hole interconnect technology and the improvement of processing accuracy. In the era of high-density, high-integration advanced electronic systems, interposers and substrates are essential to achieve high-performance SiP and AiP applications. Through-glass vias (TGVs) provide a lower-cost, lower-loss alternative to challenging and expensive silicon technology. TGV, Through Glass Via, is a vertical electrical interconnect through a glass substrate and is considered a key technology for the next generation of three-dimensional integration. TGVs are micro-vias with a diameter of typically 10μm-100μm. For various applications in the field of advanced packaging, tens of thousands of TGV vias are usually applied and metalized on each substrate to obtain the required conductivity.

[0004] At present, in the integrated circuit and printed circuit board industry, L / S (line width / line spacing) is mostly used to determine the process technology suitable for the product. The L / S range of the subtractive process of PCB hard board is 45-100μm, and the L / S range of the subtractive process of PCB soft board is 30-100μm. If L / S: below 30 / 30μm or L / S: between 2 / 2μm and 35 / 35μm is required, it is necessary to select additive processes such as MSAP process (semi-additive process) and SAP process (full additive process). At present, for substrate packaging with a depth-to-width ratio of more than 8:1, it is generally believed in the industry that the subtractive process cannot make fine lines on such substrates (L / S: 2 / 2-30 / 30μm). The additive process used by traditional TGV uses glass such as borosilicate glass and quartz glass as the substrate, and realizes 3D interconnection through seed layer sputtering, electroplating filling, chemical mechanical planarization, RDL rewiring, and bump process. However, the equipment cost of the additive process is significantly higher and is prone to low production yield problems.

[0005] Based on this, the applicant proposed a method for preparing a circuit board with micro-deep through holes based on a subtractive method, and used a subtractive process to produce a circuit board with fine circuits (L / S: 2 / 2-30 / 30μm), achieving a process breakthrough and cost reduction. Summary of the invention

[0006] In view of the above technical problems, the present invention provides a method for preparing a circuit board with through holes, which can prepare fine circuits (L / S: 2 / 2-30 / 30μm) on a micro-through hole substrate with an aspect ratio greater than 8:1 at a relatively low cost to obtain a high-density circuit board.

[0007] The present invention adopts the following technical solution:

[0008] A method for preparing a circuit board with through holes comprises the following steps:

[0009] S1. Provide a substrate to be plated, wherein the substrate has two surfaces and a through hole, wherein the through hole penetrates from one surface of the substrate to the other surface, and a ratio of the depth to the width of the through hole is greater than 8:1;

[0010] S2, sputtering metal onto the inner wall of the through hole to form a first conductive layer;

[0011] S3, placing the substrate formed with the first conductive layer in a chemical plating device, and forming a second conductive layer on the substrate, wherein the second conductive layer is a continuous layer covering the first conductive layer, the area of ​​the inner wall of the through hole not covered by the first conductive layer, and at least one of the surfaces;

[0012] S4, placing the substrate processed in step S3 in an electroplating device to form a third conductive layer, wherein the third conductive layer covers the second conductive layer and fills the through hole;

[0013] S5, placing the substrate processed in step S4 in an etching device, etching and removing all the conductive layers in the area on the substrate not covered by the patterned mask, to form gaps and circuits separated by the gaps, wherein the circuits are formed by the conductive layer under the mask; wherein the line width and line spacing of at least part of the circuits are respectively less than 35 μm;

[0014] In step S5, the substrate is suspended in the etching tank, and the etching solution is evenly sprayed onto the surface of the substrate through a spray plate opposite to the substrate to etch and remove all the conductive layers in the area not covered by the mask; wherein the spray plate has an upper partition and a bottom partition arranged up and down, and the upper partition and the bottom partition are respectively provided with a plurality of nozzles, and the liquid flow rate and / or the spraying time of the nozzle of the bottom partition are controlled to be smaller than the liquid flow rate and / or the spraying time of the nozzle of the upper partition.

[0015] In a preferred embodiment, the line width and line spacing of at least part of the lines are 2-30 μm respectively.

[0016] In a preferred embodiment, the ratio of the depth to the width of the through hole is (15-20):1.

[0017] In a preferred embodiment, in step S3, the substrate is placed in a processing tank, and a first cavity and a second cavity are formed on both sides of the substrate respectively; a chemical plating solution is introduced into the first cavity, and the chemical plating solution flows into the second cavity through the through hole on the substrate by pressure difference; a chemical plating solution is introduced into the second cavity, and the chemical plating solution flows into the first cavity through the through hole on the substrate by pressure difference; until a continuous second conductive layer is formed. Further, the chemical plating solution contains metal ions or conductive polymers.

[0018] In a more preferred embodiment, in step S3, the pressure difference is applied by a liquid level difference between the first cavity and the second cavity, or by evacuating the first cavity or the second cavity.

[0019] In a more preferred embodiment, in step S3, while applying the pressure difference, vibration or thrust toward the through hole is also applied to the chemical plating solution in the first cavity or the second cavity.

[0020] In a preferred embodiment, in step S1, the substrate having the through-hole is also cleaned.

[0021] In a further preferred embodiment, in step S1, a substrate is placed in a processing tank, and a first cavity and a second cavity are formed on both sides of the substrate respectively; a liquid is introduced into the first cavity, and the liquid flows into the second cavity through the through hole on the substrate by pressure difference; the liquid is introduced into the second cavity, and the liquid flows into the first cavity through the through hole on the substrate by pressure difference; until a continuous second conductive layer is formed. The liquid is specifically a cleaning liquid.

[0022] In a more preferred embodiment, in step S1, the pressure difference is applied by a liquid level difference between the first cavity and the second cavity, or by evacuating the first cavity or the second cavity.

[0023] In a more preferred embodiment, in step S1, while applying the pressure difference, vibration or thrust toward the through hole is also applied to the cleaning liquid in the first cavity or the second cavity.

[0024] In a preferred embodiment, in step S5, the substrate is suspended in an etching tank, and etching solution is uniformly sprayed onto the surface of the substrate to etch away all the conductive layers in the area not covered by the mask.

[0025] In a more preferred embodiment, in step S5, the substrate is vertically suspended in the etching groove, and etching solution is sprayed toward the substrate through a spray plate opposite to the substrate, wherein the substrate reciprocates relative to the spray plate along a first direction, and the first direction is parallel to the substrate.

[0026] In a more preferred embodiment, in step S5, the amount of etching liquid received on the surface of the substrate is made consistent by controlling one or more of the moving speed of the substrate, the liquid flow rate of the nozzle on the spray plate, and the spraying time of the nozzle.

[0027] In a more preferred embodiment, the spray disc has a first partition, a second partition and a third partition arranged in sequence along a first direction, and the first partition, the second partition and the third partition are respectively provided with a plurality of nozzles; in step S5, the liquid flow rate and / or the spraying duration of the nozzle of the second partition is controlled to be smaller than the liquid flow rate and / or the spraying duration of the nozzle of the first partition and the third partition.

[0028] In a more preferred embodiment, each partition has a pressure chamber located in the spray plate; in step S5, the liquid flow rate of the nozzle is controlled by adjusting the pressure of the etching solution entering the pressure chamber.

[0029] In a specific and preferred embodiment, the spray plate has an upper partition and a bottom partition arranged up and down, the upper partition includes a first partition, a second partition and a third partition arranged in sequence along a first direction, and the first partition, the second partition, the third partition and the bottom are respectively evenly provided with a plurality of nozzles; step S5 is specifically implemented as follows: the substrate is controlled to move back and forth at a uniform speed along the first direction, passing through the first partition, the second partition and the third partition in sequence, the bottom of the substrate is always facing the bottom partition, so that the nozzles in each partition spray etching solution to the substrate, and the liquid flow rate and / or spraying time of the nozzle of the second partition is controlled to be smaller than the liquid flow rate and / or spraying time of the nozzle of the first partition and the third partition, and the liquid flow rate and / or spraying time of the nozzle of the bottom partition is controlled to be smaller than the liquid flow rate and / or spraying time of the nozzle of the upper partition.

[0030] In a preferred embodiment, circuits are formed on both surfaces of the substrate, and the conductive layer in the through hole connects the circuits on the two surfaces.

[0031] In a preferred embodiment, the substrate is glass, the first conductive layer includes titanium copper atoms, the second conductive layer is a copper plating layer or a conductive polymer plating layer, and the third conductive layer is a copper plating layer.

[0032] The present invention adopts the above solution, which has the following advantages compared with the prior art:

[0033] The preparation method of the present invention can prepare fine circuits (which may be L / S: 2 / 2-30 / 30 μm) on an insulating substrate at a relatively low cost, and connect the fine circuits on two surfaces through the conductive material in a through hole with a depth-to-width ratio greater than 8:1. The conductive material in the through hole has good continuity, which ensures good conductivity, reduces the production cost of the substrate, and broadens the application range of the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0035] Figure 1 A flow chart of a preparation method according to an embodiment of the present invention is shown.

[0036] Figure 2a to Figure 2e The substrates in steps S1 to S5 are shown in sequence.

[0037] Figure 3 A structural diagram of an etching device according to an embodiment of the present invention is shown.

[0038] Figure 4 for Figure 3 Structural diagram of the swing mechanism in .

[0039] Figure 5 for Figure 3 Side view of the rocking mechanism in FIG.

[0040] Figure 6 for Figure 5 Sectional view along AA direction.

[0041] Figure 7 for Figure 6 A partial enlarged view of point B in the middle.

[0042] Figure 8 for Figure 3 Exploded view of the center spray plate.

[0043] Fig. 9 for Figure 3 Structural diagram of the center spray disc and liquid control module.

[0044] Fig.10 is an X-ray image of the circuit board prepared according to this embodiment.

[0045] in:

[0046] 100, substrate; 101, through hole; 1011, inner wall; 102, surface; 200, first conductive layer; 300, second conductive layer; 400, third conductive layer; 500, line; 600, gap;

[0047] 1. Etching groove; 11. Guide rail; 2. Swing mechanism; 21. Frame; 211. Roller; 212. Buffer assembly; 22. Power source; 3. Spray disc assembly; 31. Spray disc; 311. First partition; 312. Second partition; 313. Third partition; 314. Bottom partition; 315. Pressure chamber; 32. Nozzle; 4. Liquid control mechanism; 41. Liquid entering control module; 411. Liquid entering control unit; 42. Liquid discharging control module; 421. Liquid discharging control unit; 5. Drainage mechanism; 51. Drain valve; 6. Hanger. DETAILED DESCRIPTION

[0048] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0049] In this document, the directions or positional relationships indicated by the terms "upper", "lower", "front", "rear", etc. are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present application and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on the present application.

[0050] Figures 3 to 9 The drawings are drawn in true proportion. To keep the specification concise, the proportions of each component are not listed one by one. However, the proportions and positions of each component should be regarded as part of the content of this specification.

[0051] The present embodiment relates to a method for manufacturing a circuit board based on a subtractive process, specifically, manufacturing a circuit layer on a substrate having one or more micro-deep through holes, and filling the through holes with conductive materials to electrically connect the two sides of the substrate. The depth of the through hole is generally consistent with the thickness of the substrate, and the width (diameter) of the through hole is closely related to the circuit density on the circuit board; the "micro-deep through hole" in this article refers to a through hole with a depth-to-width ratio greater than 8:1, which is conducive to the formation of high-density circuit boards and has good application prospects in AI servers or silicon photonic communication equipment. In some preferred schemes, the depth-to-width ratio of the through hole can be (15-20):1.

[0052] Figure 1 The flowchart of the preparation method of this embodiment is shown. The preparation method prepares a circuit on a substrate with a through hole through the following steps.

[0053] Step S1: Figure 2a As shown, a substrate 100 to be plated is provided. The substrate has two surfaces 102 and a through hole 101. The through hole 101 passes through one surface of the substrate 100 to the other surface, and the ratio of the depth to the width of the through hole 101 is greater than 8:1. Herein, the "depth" of the through hole 101 is consistent with the thickness of the substrate 100, that is, the distance between the two surfaces 102; the "width" of the through hole 101 refers to the size of the opening of the through hole 101 on the two surfaces 102. If it is a circular hole, the width is equal to the diameter of the opening; if it is a square hole, it is the length of the short side of the opening. The substrate 100 is an insulating substrate; in this embodiment, the substrate is glass; in other embodiments, the substrate can be other insulating substrates.

[0054] Step S2: Figure 2b As shown, metal is sputtered onto the inner wall 1011 of the through hole 101 to form the first conductive layer 200. Specifically, the PVD technology can be used to place the substrate 100 in a sputtering device, and titanium copper atoms or other metals are sputtered onto the substrate 100 to form the first conductive layer 200. The first conductive layer 200 covers the two surfaces 102 of the substrate 100 and covers a portion of the inner wall 1011 of the through hole 101. However, for the through hole 101 with an aspect ratio greater than 8:1, it is difficult for the metal atoms to reach the deeper inner wall 1011 (middle part) of the through hole 101, that is, the PVD technology cannot form a continuous conductive layer on the deeper inner wall 1011 of the through hole 101, and the first conductive layer 200 is disconnected inside the through hole 101 (middle part).

[0055] Step S3: Figure 2c As shown, the substrate 100 formed with the first conductive layer 200 is placed in a chemical plating device to form a second conductive layer 300 on the substrate 100, wherein the second conductive layer 300 is a continuous layer covering the first conductive layer 200, the area of ​​the inner wall 1011 of the through hole not covered by the first conductive layer 200, and at least one surface. It is necessary to pre-dispose a layer of catalyst on the surface of the substrate 100, especially on the inner wall 1011 deep in the through hole 101 not covered with the first conductive layer 200; during chemical plating, metal particles or conductive polymers can be attached to these surfaces to form a continuous plating layer, namely, the second conductive layer 300.

[0056] Step S4: Figure 2d As shown, the substrate 100 processed in step S3 is placed in an electroplating device to form a third conductive layer 400, wherein the third conductive layer 400 covers the second conductive layer 300 and fills the through hole 101. The plating layer is thickened by electroplating and the through hole 101 is filled. The cost of electroplating is lower than that of chemical plating, so it is helpful to reduce the overall manufacturing cost.

[0057] Step S5: Figure 2eAs shown, the substrate 100 processed in step S4 is placed in an etching device, and all the conductive layers (which may include the stacked first conductive layer 200, the second conductive layer 300 and the third conductive layer 400) in the area not covered by the patterned mask on the substrate 100 are etched away to form a gap 600, and the conductive layer under the mask forms a circuit 500 and a soldering pad (PAD). The line width and line spacing of at least part of the circuit 500 are less than 35μm respectively. In this embodiment, L / S: 2 / 2-30 / 30μm; the line width and line spacing of the circuit 500 are 2-30μm respectively.

[0058] After step S4, a patterned mask is disposed on the substrate 100, and the pattern of the mask is consistent with the circuit 500. A known mask processing method can be used to form a patterned mask on the substrate 100, such as a photoresist patterned mask.

[0059] It should also be noted that Figure 2a to Figure 2d Only the manufacturing of one through hole 101 is schematically shown. In actual application, a plurality of through holes 101 can be arranged on a substrate 100 as required; after the above steps are performed once, the substrate 100 and the plurality of through holes 101 thereon are processed at the same time.

[0060] Step S3 specifically includes the following steps:

[0061] S31, placing the substrate 100 in a processing tank (specifically, a chemical plating tank of a chemical plating device in step S3), and forming a first cavity and a second cavity on both sides of the substrate 100 respectively;

[0062] S32, introducing liquid, specifically chemical plating solution, into the first cavity, and causing the chemical plating solution to flow into the second cavity through the through hole 101 on the substrate 100 by pressure difference;

[0063] S33 , introducing chemical plating solution into the second cavity, and causing the chemical plating solution to flow into the first cavity through the through hole 101 on the substrate 100 by pressure difference.

[0064] Steps S32 and S33 are performed sequentially and cyclically until a continuous second conductive layer 300 is formed.

[0065] The pressure difference is applied through the liquid level difference between the first cavity and the second cavity. For example, in step S32, the liquid level of the first cavity is higher than the liquid level of the second cavity, and under the action of the gravity of the liquid itself, the chemical plating solution is forced to flow from the first cavity with a higher liquid level to the second cavity with a lower liquid level through the through hole 101; in step S33, the liquid level of the second cavity is higher than the liquid level of the first cavity, and under the action of the gravity of the liquid itself, the chemical plating solution is forced to flow from the second cavity with a higher liquid level to the first cavity with a lower liquid level through the through hole 101. In another embodiment, the pressure difference can also be applied by evacuating the first cavity or the second cavity; evacuating the first cavity or the second cavity, under the action of negative pressure, the chemical plating solution is forced to flow through the through hole 101.

[0066] Furthermore, in steps S32 and S33, while applying the pressure difference, vibration is also applied to the chemical plating solution in the first cavity or the second cavity or a thrust is applied toward the through hole 101. For example, vibration is applied to the chemical plating solution in the first cavity or the second cavity by an ultrasonic generator; or a push plate in the first cavity or the second cavity is moved toward the substrate 100, thereby pushing the chemical plating solution. In this way, it is ensured that the chemical plating solution can enter the depth of the through hole 101, replace the liquid, and bring out the reaction product in time, thereby ensuring the continuity of the plating layer in the through hole 101.

[0067] It should also be noted that in the preferred solution, in step S1, after the through hole 101 is opened on the substrate 100, it is first cleaned using a device and method similar to the device and method of step S3. The inventors have found that, compared with not cleaning or using a conventional cleaning method (such as immersion), the plating effect obtained by pre-cleaning the substrate 100 using this method and then performing step S2 is better, because impurities such as hair scraps deep in the through hole 101 can be cleaned and removed to the greatest extent. Specifically, step S1 specifically includes: S10, opening a through hole 101 on the substrate 100; S11, placing the substrate 100 in a processing tank (specifically a cleaning tank in step S1), and forming a first cavity and a second cavity on both sides of the substrate 100 respectively; S12, introducing a liquid, specifically a cleaning liquid, into the first cavity, and causing the chemical plating liquid to flow into the second cavity through the through hole 101 on the substrate 100 through a pressure difference; S13, introducing a chemical plating liquid into the second cavity, and causing the chemical plating liquid to flow into the first cavity through the through hole 101 on the substrate 100 through a pressure difference.

[0068] Similarly, the pressure difference is applied through the liquid level difference in the first cavity and the second cavity. For example, in step S12, the liquid level in the first cavity is higher than the liquid level in the second cavity, and under the action of the liquid's own gravity, the cleaning liquid is forced to flow through the through hole 101 from the first cavity with a higher liquid level to the second cavity with a lower liquid level; in step S13, the liquid level in the second cavity is higher than the liquid level in the first cavity, and under the action of the liquid's own gravity, the cleaning liquid is forced to flow through the through hole 101 from the second cavity with a higher liquid level to the first cavity with a lower liquid level. In another embodiment, the pressure difference can also be applied by vacuuming the first cavity or the second cavity; vacuuming the first cavity or the second cavity, and under the action of negative pressure, forcing the cleaning liquid to flow through the through hole 101.

[0069] Furthermore, in steps S12 and S13, while applying the pressure difference, vibration is also applied to the cleaning liquid in the first cavity or the second cavity or a thrust is applied toward the through hole 101. For example, vibration is applied to the cleaning liquid in the first cavity or the second cavity by an ultrasonic generator; or a push plate in the first cavity or the second cavity is moved toward the substrate 100, thereby pushing the cleaning liquid. In this way, it is ensured that the cleaning liquid can enter the depth of the through hole 101, take out the impurities, and ensure an excellent cleaning effect.

[0070] In step S5 , the substrate 100 is suspended in an etching tank of an etching device, and etching solution is evenly sprayed onto the surface of the substrate 100 to remove all conductive layers in areas not covered by the mask, thereby forming a gap 600 and circuits 500 separated by the gap 600 .

[0071] Figures 3 to 9 FIG. 2 shows the etching equipment used in this embodiment. Figures 3 to 9 As shown, the etching device includes an etching tank 1, a swing mechanism 2, a spray plate assembly 3, a solution control mechanism 4 and a drainage mechanism 5. The etching tank 1 has a tank body, which is hollow and has a notch facing upward. The substrate is mounted on a hanger 6, which is mounted on the swing mechanism 2 and is configured to vertically suspend the substrate in the etching tank 1. The spray plate assembly 3 and the hanger 6 are opposite to each other and are used to controllably spray etching solution onto the substrate. The solution control mechanism 4 is used to controllably provide etching solution to the spray plate assembly 3. The drainage mechanism 5 is used to discharge the waste liquid in the etching tank 1.

[0072] The swing mechanism 2 includes a frame 21, and the hanger 6 is installed in the frame 21. The frame 21 is movably arranged in the etching groove 1 along a first direction, which is parallel to the substrate and corresponds to Figure 6In the left and right directions. Further, a guide rail 11 extending in the first direction is fixedly provided in the etching groove 1, and the frame 21 and the guide rail 11 are slidably matched. Specifically in this embodiment, the guide rail 11 is arranged at the bottom of the etching groove 1, and a roller 211 is installed at the bottom of the frame 21, and the roller 211 and the guide rail 11 are in rolling contact. The swing mechanism 2 further includes a power source 22 for driving the frame 21 to move along the first direction. Specifically in this embodiment, the power source 22 includes a motor. How to drive the frame 21 to move back and forth through the power source 22 is not the main point of the invention of this application, and a transmission mechanism known in the prior art for converting rotary motion into linear motion can be used. In another embodiment, the power source 22 can also be a cylinder, and the frame 21 is connected to make it reciprocate and move linearly through the piston rod of the cylinder. Buffer components 212 are provided on both sides (left and right sides) of the frame 21, specifically including buffer springs, which are used to buffer the inertia of the left and right movement of the hanger 6 to avoid the collision between the frame 21 and the hanger 6 and cause damage to the substrate or the coating. When the substrate is installed in the hanger 6 , there are a plurality of buffer components 212 on the left and right sides of the substrate respectively.

[0073] like Figure 8 As shown, the spray plate assembly 3 includes a spray plate 31, and a plurality of nozzles 32 are arranged on the spray plate 31. The spray plate 31 has an upper partition and a bottom partition 314 arranged up and down, and the upper partition includes a first partition 311, a second partition 312, and a third partition 313 arranged in sequence along a first direction, and a plurality of nozzles 32 are evenly arranged in the first partition 311, the second partition 312, the third partition 313 and the bottom. Each partition has a hollow pressure chamber 315 located in the spray plate 31, and the nozzle 32 is connected to the pressure chamber 315, and the pressure chamber 315 provides pressurized etching solution to the nozzle 32.

[0074] The liquid medicine control mechanism 4 includes a liquid medicine entry control module 41 and a liquid medicine discharge control module 42. The liquid medicine entry control module 41 has a plurality of liquid medicine entry control units 411, and each partitioned pressure chamber 315 corresponds to at least one liquid medicine entry control unit 411, which is used to control the amount and pressure of the etching liquid medicine entering the partitioned pressure chamber 315. The number of liquid medicine entry control modules 41 can be multiple, corresponding to etching liquid medicines of different types or concentrations, and different etching liquid medicines can be introduced into the pressure chamber 315 of each partition as needed. The liquid medicine discharge control module 42 has a plurality of liquid medicine discharge control units 421, and each partitioned pressure chamber 315 corresponds to one liquid medicine discharge control unit 421, which is used to discharge the residual liquid medicine in the partition. The liquid medicine entry control unit 411 and the liquid medicine discharge control unit 421 respectively include diaphragm valves.

[0075] The liquid discharge mechanism 5 is disposed at the bottom of the etching tank 1, and is used to discharge the residual liquid medicine flowing down from the substrate from the etching tank 1. The liquid discharge mechanism 5 specifically includes a liquid discharge valve 51 and a vacuum pump.

[0076] In step S5, the substrate is vertically suspended in the etching tank 1, and etching solution is sprayed onto the substrate through the spray plate 31 opposite to the substrate, wherein the substrate reciprocates relative to the spray plate 31 along a first direction parallel to the substrate.

[0077] Furthermore, in step S5, by controlling one or more of the moving speed of the substrate, the liquid flow rate of the nozzle 32 on the spray plate 31, and the spraying time of the nozzle 32, the amount of etching liquid received on the surface of the substrate is made consistent.

[0078] The liquid flow rate and / or liquid spraying duration of the nozzle 32 of the second partition 312 is controlled to be smaller than the liquid flow rate and / or liquid spraying duration of the nozzle 32 of the first partition 311 and the third partition 313. The liquid flow rate and / or liquid spraying duration of the nozzle 32 of the bottom partition 314 is controlled to be smaller than the liquid flow rate and / or liquid spraying duration of the nozzle 32 of the upper partition.

[0079] In addition, in step S5 , the liquid flow rate of the nozzle 32 is controlled by adjusting the pressure of the etching solution introduced into the pressure chamber 315 .

[0080] The circuit board obtained by the above preparation method was sampled, the circuit board specification was 800×800mm, and the line width was 11.5~12.5μm. Some test results are as follows:

[0081] The uniformity of the copper layer on the substrate is 3-5%;

[0082] X-ray images of TGV Fig.10 As shown, the copper layer thickness in the cross section is about 9 μm and the TGV hole depth is about 300 μm.

[0083] The above-mentioned preparation method of this embodiment can prepare fine circuits (L / S: 2 / 2-30 / 30μm) on an insulating substrate at a relatively low cost, and connect the fine circuits on the two surfaces through the conductive material in the through hole with a depth-to-width ratio greater than 8:1. The continuity of the conductive material in the through hole is good, which ensures good conductivity, reduces the production cost of the substrate, and broadens the application range of the substrate.

[0084] As shown in this specification and claims, the terms "comprises" and "include" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list, and the method or device may also include other steps or elements. The term "and / or" as used herein includes any combination of one or more of the relevant listed items.

[0085] It is further understood that in the present disclosure, "plurality" refers to two or more than two, and other quantifiers are similar thereto.

[0086] It should be noted that, unless otherwise specified, when a feature is referred to as being “fixed” or “connected” to another feature, it may be directly fixed or connected to the other feature, or it may be indirectly fixed or connected to the other feature.

[0087] The above embodiment is only for illustrating the technical concept and features of the present invention, and is a preferred embodiment. Its purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a circuit board with through holes, characterized in that: The steps include: S1. Provide a substrate to be plated, wherein the substrate has two surfaces and a through hole, wherein the through hole penetrates from one surface of the substrate to the other surface, and a ratio of the depth to the width of the through hole is greater than 8:1; S2, sputtering metal onto the inner wall of the through hole to form a first conductive layer; S3, placing the substrate formed with the first conductive layer in a chemical plating device, and forming a second conductive layer on the substrate, wherein the second conductive layer is a continuous layer covering the first conductive layer, the area of ​​the inner wall of the through hole not covered by the first conductive layer, and at least one of the surfaces; S4, placing the substrate processed in step S3 in an electroplating device to form a third conductive layer, wherein the third conductive layer covers the second conductive layer and fills the through hole; S5, placing the substrate processed in step S4 in an etching device, etching and removing all the conductive layers in the area on the substrate not covered by the patterned mask, to form gaps and circuits separated by the gaps, wherein the circuits are formed by the conductive layer under the mask; wherein the line width and line spacing of at least part of the circuits are respectively less than 35 μm; In step S5, the substrate is suspended in the etching tank, and the etching solution is evenly sprayed onto the surface of the substrate through a spray plate opposite to the substrate to etch and remove all the conductive layers in the area not covered by the mask; wherein the spray plate has an upper partition and a bottom partition arranged up and down, and the upper partition and the bottom partition are respectively provided with a plurality of nozzles, and the liquid flow rate and / or the spraying time of the nozzle of the bottom partition are controlled to be smaller than the liquid flow rate and / or the spraying time of the nozzle of the upper partition.

2. The preparation method according to claim 1, characterized in that: The line width and line spacing of at least part of the lines are 2-30 μm respectively.

3. The preparation method according to claim 1, characterized in that: The ratio of the depth to the width of the through hole is (15-20):

1.

4. The preparation method according to claim 1, characterized in that: In step S1, the substrate with the through hole is also cleaned; in step S1 or S3, the substrate is placed in a processing tank to form a first cavity and a second cavity on both sides of the substrate respectively; a liquid is introduced into the first cavity, the liquid is a chemical plating liquid or a cleaning liquid, and the liquid flows into the second cavity through the through hole on the substrate by a pressure difference; the liquid is introduced into the second cavity, and the liquid flows into the first cavity through the through hole on the substrate by a pressure difference; until a continuous second conductive layer is formed.

5. The preparation method according to claim 4, characterized in that: In step S1 or S3, the pressure difference is applied by a liquid level difference between the first cavity and the second cavity, or by vacuuming the first cavity or the second cavity.

6. The preparation method according to claim 4 or 5, characterized in that: In step S1 or S3, while applying the pressure difference, vibration or thrust toward the through hole is also applied to the liquid in the first cavity or the second cavity.

7. The preparation method according to claim 1, characterized in that: In step S5, the substrate is vertically suspended in the etching tank, and etching solution is sprayed onto the substrate, wherein the substrate reciprocates relative to the spray plate along a first direction, and the first direction is parallel to the substrate.

8. The preparation method according to claim 7, characterized in that: In step S5, the amount of etching liquid received on the surface of the substrate is made consistent by controlling one or more of the moving speed of the substrate, the liquid flow rate of the nozzle on the spray plate, and the spraying time of the nozzle.

9. The preparation method according to claim 1, characterized in that: Each partition has a pressure chamber located in the spray plate; in step S5, the liquid flow rate of the nozzle is controlled by adjusting the pressure of the etching solution entering the pressure chamber.

10. The preparation method according to claim 1, characterized in that: Circuits are formed on both surfaces of the substrate, and the conductive layer in the through hole connects the circuits on the two surfaces; the substrate is glass, the first conductive layer includes titanium copper atoms, the second conductive layer is a copper plating layer or a conductive polymer plating layer, and the third conductive layer is a copper plating layer.

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