Method for fabricating circuit boards with through-holes having an aspect ratio greater than 8:1

Abstract

This invention discloses a method for fabricating a circuit board with through-holes having an aspect ratio greater than 8:1. The method includes the following steps: providing a substrate to be plated; sputtering metal onto the inner wall of the through-hole to form a first conductive layer; placing the substrate with the first conductive layer in a chemical plating apparatus to form 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 surface; placing the substrate in an electroplating apparatus to form a third conductive layer, the third conductive layer covering the second conductive layer and filling the through-hole; etching away all conductive layers in the areas of the substrate not covered by a patterned mask, and forming circuits in the conductive layer under the mask; wherein at least a portion of the circuits has a linewidth and line spacing of less than 35 μm. This invention enables the fabrication of fine circuits on a micro-via substrate with an aspect ratio greater than 8:1 at a lower cost, resulting in a high-density circuit board.

Description

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

[0002] This invention belongs to the field of circuit board manufacturing, and specifically relates to a method for manufacturing a circuit board with through holes having an aspect ratio greater than 8:1. Background Technology

[0003] Advanced packaging is playing a steadily increasing role in the semiconductor industry, and its development is closely related to the evolution of through-hole interconnect (TBV) technology and the improvement of processing precision. In the era of high-density, highly integrated advanced electronic systems, the interposers and substrates for high-performance SiP and AiP applications are crucial. Through-glass vias (TGVs) offer a lower-cost, lower-loss alternative to the challenging and expensive silicon technology. TGVs, or Through Glass Vias, are vertical electrical interconnects that pass through glass substrates and are considered a key technology for next-generation 3D integration. TGVs are microvias with diameters typically ranging from 10μm to 100μm. For various applications in advanced packaging, tens of thousands of TGV vias are typically applied to each substrate and metallized to achieve the required conductivity.

[0004] Currently, in the integrated circuit and printed circuit board industry, the line width / spacing (L / S) is often used to determine the suitable manufacturing process for a product. The L / S range for subtractive processes on rigid PCBs is 45-100μm, while for flexible PCBs it is 30-100μm. If an L / S of less than 30 / 30μm or between 2 / 2μm and 35 / 35μm is required, additive processes such as MSAP (semi-additive) or SAP (fully additive) are necessary. Currently, for substrates with an aspect ratio of 8:1 or higher, the industry generally believes that subtractive processes cannot fabricate fine lines (L / S: 2 / 2-30 / 30μm) on such substrates. Traditional TGV (Transformer Transformer) uses additive processes with borosilicate glass, quartz glass, etc., as substrates. It achieves 3D interconnection through seed layer sputtering, electroplating, chemical mechanical planarization, RDL rewiring, and bumping. However, the addition process has significantly higher equipment costs and is prone to low production yields.

[0005] Based on this, the applicant proposes a method for fabricating circuit boards with micro-deep vias using a subtractive process. This method uses a subtractive process to fabricate circuit boards with fine lines (L / S: 2 / 2-30 / 30μm), achieving a breakthrough in process technology and cost reduction. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for fabricating a circuit board with through-holes, which enables the fabrication of fine lines (L / S: 2 / 2-30 / 30μm) on a micro-via substrate with an aspect ratio greater than 8:1 at a lower cost, thereby obtaining a high-density circuit board.

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

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

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

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

[0011] S3. Place the substrate with the first conductive layer in a chemical plating apparatus and form 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. Place 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. Place the substrate processed in step S4 in an etching apparatus and etch away all conductive layers in the areas of the substrate not covered by the patterned mask to form gaps and lines separated by the gaps. The lines are formed by the conductive layer under the mask. At least a portion of the lines have a line width and line spacing of less than 35 μm.

[0014] In step S5, the substrate is suspended in the etching tank, and etching solution is uniformly sprayed onto the surface of the substrate through a spray disc opposite to the substrate to etch away all conductive layers in the areas not covered by the mask. The spray disc has an upper section and a bottom section arranged vertically, and the upper section and the bottom section are respectively equipped with multiple nozzles. The liquid flow rate and / or spraying time of the nozzles in the bottom section are controlled to be less than the liquid flow rate and / or spraying time of the nozzles in the upper section.

[0015] In a preferred embodiment, at least a portion of the lines have a line width and line spacing of 2 to 30 μm.

[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, a substrate is placed in a processing tank, and a first cavity and a second cavity are formed on both sides of the substrate; a chemical plating solution is introduced into the first cavity, and the chemical plating solution flows into the second cavity through a through-hole on the substrate by a pressure difference; a chemical plating solution is introduced into the second cavity, and the chemical plating solution flows into the first cavity through a through-hole on the substrate by a 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 the liquid level difference in 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 a 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, step S1 further includes cleaning the substrate with through holes.

[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; liquid is introduced into the first cavity, and the liquid flows into the second cavity through a 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 a through-hole on the substrate by a pressure difference; until a continuous second conductive layer is formed. The liquid is specifically a cleaning solution.

[0022] In a more preferred embodiment, in step S1, the pressure difference is applied by the liquid level difference in 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 fluid 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 conductive layers in the areas not covered by the mask.

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

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

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

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

[0029] In a specific and preferred embodiment, the spray disk has an upper section and a bottom section arranged vertically. The upper section includes a first section, a second section, and a third section arranged sequentially along a first direction. Multiple nozzles are evenly arranged in the first section, the second section, the third section, and the bottom section. Step S5 is specifically implemented as follows: the substrate is controlled to move back and forth at a constant speed along the first direction, passing through the first section, the second section, and the third section in sequence. The bottom of the substrate is always directly facing the bottom section, so that the nozzles in each section spray etching solution onto the substrate. The flow rate and / or spraying time of the nozzles in the second section are controlled to be less than the flow rate and / or spraying time of the nozzles in the first section and the third section. The flow rate and / or spraying time of the nozzles in the bottom section are controlled to be less than the flow rate and / or spraying time of the nozzles in the upper section.

[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 both surfaces.

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

[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 lines (with L / S ratios of 2 / 2 to 30 / 30 μm) on an insulating substrate at a lower cost. The fine lines on the two surfaces are connected by conductive material in through-holes with an aspect ratio greater than 8:1. The continuity of the conductive material in the through-holes is good, ensuring good conductivity, reducing the manufacturing cost of the substrate and broadening the application range of the substrate. Attached Figure Description

[0034] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used 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 those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

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

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

[0038] Figure 4 for Figure 3 The structural diagram of the swing mechanism in the image.

[0039] Figure 5 for Figure 3 Side view of the swing mechanism in the image.

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

[0041] Figure 7 for Figure 6 A magnified view of a section at point B in the middle.

[0042] Figure 8 for Figure 3 Exploded view of the central spray disc.

[0043] Figure 9 for Figure 3 Structural diagram of the central spray plate and liquid control module.

[0044] Figure 10 This 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, Circuit; 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 section; 312. Second section; 313. Third section; 314. Bottom section; 315. Pressure chamber; 32. Nozzle; 4. Chemical control mechanism; 41. Chemical inlet control module; 411. Chemical inlet control unit; 42. Chemical discharge control module; 421. Chemical discharge control unit; 5. Drainage mechanism; 51. Drainage valve; 6. Hanger. Detailed Implementation

[0048] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more readily understood by those skilled in the art. It should be noted that the description of these embodiments is for the purpose of aiding understanding the present invention, but does not constitute a limitation thereof.

[0049] In this document, the terms “upper,” “lower,” “front,” “rear,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0050] Figures 3 to 9 The diagrams are drawn to scale. To keep the instructions concise, the proportions of each component are not listed individually. However, the proportions and positions of each component should be considered part of the content of this instruction manual.

[0051] This embodiment relates to a method for fabricating circuit boards based on a subtractive process. Specifically, it involves fabricating a circuit layer on a substrate with one or more micro-deep vias, and filling the vias with conductive material to make both sides of the substrate electrically conductive. The depth of the via is generally consistent with the thickness of the substrate, while the width (diameter) of the via is closely related to the circuit density on the circuit board. In this article, "micro-deep vias" refers to vias with a depth-to-width ratio greater than 8:1, which is beneficial for forming high-density circuit boards and has good application prospects in AI servers or silicon photonics communication devices. In some preferred embodiments, the depth-to-width ratio of the via can be (15-20):1.

[0052] Figure 1 A flowchart of the fabrication method of this embodiment is shown, which fabricates circuits on a substrate with through holes through the following steps.

[0053] Step S1: As Figure 2a As shown, a substrate 100 to be plated is provided. The substrate has two surfaces 102 and a through-hole 101, which extends from one surface of the substrate 100 to the other surface. The depth-to-width ratio of the through-hole 101 is greater than 8:1. In this document, the “depth” of the through-hole 101 is the same as the thickness of the substrate 100, i.e., 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, the width is the length of the shorter 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: As Figure 2b As shown, metal is sputtered onto the inner wall 1011 of the via 101 to form a first conductive layer 200. Specifically, PVD technology can be used, in which the substrate 100 is placed in a sputtering apparatus, 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 both surfaces 102 of the substrate 100 and a portion of the inner wall 1011 of the via 101. However, for vias 101 with an aspect ratio greater than 8:1, metal atoms have difficulty reaching the deeper inner wall 1011 (middle part) of the via 101. That is, PVD technology cannot form a continuous conductive layer on the deeper inner wall 1011 of the via 101, and the first conductive layer 200 is broken inside the via 101 (middle part).

[0055] Step S3: As Figure 2c As shown, a substrate 100 with a first conductive layer 200 is placed in a chemical plating apparatus, and a second conductive layer 300 is formed on the substrate 100. 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. A catalyst layer needs to be pre-applied to the surface of the substrate 100, particularly on the inner wall 1011 of the through hole 101 that is not covered by the first conductive layer 200. During chemical plating, metal particles or conductive polymers can adhere to these surfaces to form a continuous plating layer, i.e., the second conductive layer 300.

[0056] Step S4: As Figure 2d As shown, the substrate 100 processed in step S3 is placed in an electroplating apparatus 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. Electroplating thickens the plating layer and fills the through-hole 101. Electroplating is less expensive than chemical plating, thus helping to reduce the overall manufacturing cost.

[0057] Step S5: As Figure 2eAs shown, the substrate 100 processed in step S4 is placed in an etching apparatus. All conductive layers (potentially including stacked first conductive layer 200, second conductive layer 300, and third conductive layer 400) in the areas of the substrate 100 not covered by the patterned mask are etched away, forming gaps 600. The conductive layers under the mask form lines 500 and pads (PADs). At least a portion of the lines 500 have a linewidth and line spacing of 35 μm or less. In this embodiment, L / S: 2 / 2-30 / 30 μm; the linewidth and line spacing of the lines 500 are 2 to 30 μm.

[0058] In step S4, a patterned mask is formed on the substrate 100, and the pattern of the mask is consistent with that of the circuit 500. The patterned mask can be formed on the substrate 100 using known mask processing methods, such as a photoresist patterned mask.

[0059] It should also be noted that, Figures 2a to 2d The fabrication of one through-hole 101 is only schematically shown. In practical applications, multiple through-holes 101 can be arranged on a substrate 100 as needed; by performing the above steps once, the substrate 100 and the multiple through-holes 101 on it are processed simultaneously.

[0060] Step S3 specifically includes the following steps:

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

[0062] S32. Liquid, specifically chemical plating solution, is introduced into the first cavity. The chemical plating solution flows into the second cavity through the through hole 101 on the substrate 100 by pressure difference.

[0063] S33. Chemical plating solution is introduced into the second cavity, and the chemical plating solution flows 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 and second chambers. For example, in step S32, the liquid level in the first chamber is higher than that in the second chamber. Under the influence of gravity, the electroless plating solution is forced to flow through the through-hole 101 from the first chamber with a higher liquid level into the second chamber with a lower liquid level. In step S33, the liquid level in the second chamber is higher than that in the first chamber. Under the influence of gravity, the electroless plating solution is forced to flow through the through-hole 101 from the second chamber with a higher liquid level into the first chamber with a lower liquid level. In another embodiment, a pressure difference can also be applied by evacuating the first or second chamber; evacuating the first or second chamber creates negative pressure, forcing the electroless plating solution to flow through the through-hole 101.

[0066] Furthermore, in steps S32 and S33, while applying the pressure difference, vibration or a pushing force towards the through-hole 101 is also applied to the electroless plating solution in the first or second cavity. For example, vibration is applied to the electroless plating solution in the first or second cavity using an ultrasonic generator; or a pusher plate in the first or second cavity is moved towards the substrate 100, thereby pushing the electroless plating solution. In this way, it is ensured that the electroless plating solution can penetrate deep into the through-hole 101 for chemical replacement, timely removal of reaction products, and ensure the continuity of the plating layer within the through-hole 101.

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

[0068] Similarly, a pressure difference is applied through the liquid level difference between the first and second chambers. For example, in step S12, if the liquid level in the first chamber is higher than that in the second chamber, the liquid is forced to flow through the through-hole 101 from the first chamber with a higher liquid level into the second chamber with a lower liquid level due to gravity. In step S13, if the liquid level in the second chamber is higher than that in the first chamber, the liquid is forced to flow through the through-hole 101 from the second chamber with a higher liquid level into the first chamber with a lower liquid level due to gravity. In another embodiment, a pressure difference can also be applied by evacuating the first or second chamber; by evacuating the first or second chamber, the cleaning liquid is forced to flow through the through-hole 101 under negative pressure.

[0069] Furthermore, in steps S12 and S13, while applying the pressure difference, vibration or a pushing force towards the through hole 101 is also applied to the cleaning fluid in the first or second cavity. For example, vibration is applied to the cleaning fluid in the first or second cavity using an ultrasonic generator; or a pusher plate in the first or second cavity is moved towards the substrate 100, thereby pushing the cleaning fluid. In this way, it is ensured that the cleaning fluid can penetrate deep into the through hole 101, carrying away impurities and ensuring excellent cleaning results.

[0070] In step S5, the substrate 100 is suspended in the etching tank of the etching equipment, and etching solution is uniformly sprayed onto the surface of the substrate 100 to etch away all conductive layers in the areas not covered by the mask, forming gaps 600 and lines 500 separated by gaps 600.

[0071] Figures 3 to 9 The etching equipment used in this embodiment is shown. (Refer to...) Figures 3 to 9 As shown, the etching equipment includes an etching tank 1, a swaying mechanism 2, a spray nozzle assembly 3, a chemical control mechanism 4, and a drainage mechanism 5. The etching tank 1 has a hollow tank body with an upward-facing opening. A substrate is mounted on a hanger 6, which is mounted on the swaying mechanism 2 and configured to vertically suspend the substrate in the etching tank 1. The spray nozzle assembly 3 and the hanger 6 are opposite each other and are used to controllably spray etching chemicals onto the substrate. The chemical control mechanism 4 is used to controllably supply etching chemicals to the spray nozzle assembly 3. The drainage mechanism 5 is used to drain waste liquid from the etching tank 1.

[0072] The swing mechanism 2 includes a frame 21, in which a hanger 6 is mounted. The frame 21 is movably disposed in the etching groove 1 along a first direction parallel to the substrate, the first direction corresponding to... Figure 6The left and right directions are defined. Further, a guide rail 11 extending along the first direction is fixedly disposed in the etching groove 1, and the frame 21 and the guide rail 11 are slidably engaged. Specifically, in this embodiment, the guide rail 11 is disposed at the bottom of the etching groove 1, and a roller 211 is mounted on the bottom of the frame 21, with the roller 211 and the guide rail 11 in rolling contact. The rocking 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 reciprocate through the power source 22 is not the inventive point of this application; a transmission mechanism known in the prior art that converts rotational motion into linear motion can be used. In another embodiment, the power source 22 can also be a cylinder, with the piston rod of the cylinder connecting the frame 21 to make it reciprocate linearly. Buffer components 212 are provided on both sides (left and right sides) of the frame 21, specifically including buffer springs, for buffering the inertia of the left and right movement of the hanger 6, preventing the frame 21 and the hanger 6 from colliding and causing damage to the substrate or plating, etc. After the substrate is installed in the mounting bracket 6, there are multiple buffer components 212 on the left and right sides of the substrate.

[0073] like Figure 8 As shown, the spray disk assembly 3 includes a spray disk 31, on which multiple nozzles 32 are disposed. The spray disk 31 has an upper section and a bottom section 314 arranged vertically. The upper section includes a first section 311, a second section 312, and a third section 313 arranged sequentially along a first direction. Multiple nozzles 32 are evenly distributed in the first section 311, the second section 312, the third section 313, and the bottom section. Each section has a hollow pressure chamber 315 located within the spray disk 31. The nozzles 32 are connected to the pressure chamber 315, and pressurized etching solution is supplied to the nozzles 32 through the pressure chamber 315.

[0074] The etching solution control mechanism 4 includes an etching solution inlet control module 41 and an etching solution outlet control module 42. The etching solution inlet control module 41 has multiple etching solution inlet control units 411, with at least one corresponding control unit 411 for each zone's pressure chamber 315, used to control the amount and pressure of the etching solution entering the zone's pressure chamber 315. The number of etching solution inlet control modules 41 can be multiple, each corresponding to different types or concentrations of etching solutions, allowing different etching solutions to be introduced into each zone's pressure chamber 315 as needed. The etching solution outlet control module 42 has multiple etching solution outlet control units 421, with one corresponding control unit 421 for each zone's pressure chamber 315, used to discharge residual etching solution from the zone. Both the etching solution inlet control unit 411 and the etching solution outlet control unit 421 include diaphragm valves.

[0075] The drainage mechanism 5 is located at the bottom of the etching tank 1 and is used to drain the residual chemical solution flowing down from the substrate from the etching tank 1. The drainage mechanism 5 specifically includes a drainage valve 51 and a vacuum pump, etc.

[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 disk 31 opposite to the substrate. The substrate moves back and forth relative to the spray disk 31 along a first direction, which is parallel to the substrate.

[0077] Furthermore, in step S5, by controlling one or more of the following: 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 solution received on the surface of the substrate tends to be consistent.

[0078] Specifically, the liquid flow rate and / or spraying duration of the nozzle 32 in the second zone 312 are controlled to be less than the liquid flow rate and / or spraying duration of the nozzle 32 in the first zone 311 and the third zone 313. The liquid flow rate and / or spraying duration of the nozzle 32 in the bottom zone 314 are controlled to be less than the liquid flow rate and / or spraying duration of the nozzle 32 in the upper zone.

[0079] In addition, in step S5, the 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 prototyped. The circuit board dimensions were 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 image of TGV as follows Figure 10 As shown, the copper layer thickness in the cross-section is approximately 9 μm, and the TGV hole depth is approximately 300 μm.

[0083] The above-described preparation method of this embodiment can prepare fine lines (L / S: 2 / 2-30 / 30μm) on an insulating substrate at a lower cost. The fine lines on the two surfaces are connected by conductive material in through holes with a depth-to-width ratio greater than 8:1. The continuity of the conductive material in the through holes is good, ensuring good conductivity, reducing the manufacturing cost of the substrate and broadening the application range of the substrate.

[0084] As indicated in this specification and claims, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, and these steps and elements do not constitute an exclusive list; the method or apparatus may also include other steps or elements. The term "and / or" as used herein includes any combination of one or more of the associated listed items.

[0085] It can be further understood that in this disclosure, "multiple" refers to two or more, and other quantifiers are similar.

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

[0087] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are preferred embodiments. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and they should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made according to the principles of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for fabricating a circuit board with through holes, characterized in that, Includes the following steps: S1. Provide a substrate to be plated, the substrate having two surfaces and a through hole, the through hole penetrating from one surface of the substrate to the other surface, the ratio of the depth to the width of the through hole being greater than 8:1; S2. Sputter metal onto the inner wall of the through hole to form a first conductive layer; S3. Place the substrate with the first conductive layer in a chemical plating apparatus and form 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. Place 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. Place the substrate processed in step S4 in an etching apparatus and etch away all conductive layers in the areas of the substrate not covered by the patterned mask to form gaps and lines separated by the gaps. The lines are formed by the conductive layer under the mask. At least a portion of the lines have a line width and line spacing of less than 35 μm. In step S5, the substrate is vertically suspended in the etching tank, and etching solution is uniformly sprayed onto the surface of the substrate through a spray disc opposite to the substrate to etch away all conductive layers in areas not covered by the mask. The spray disc has an upper section and a bottom section arranged vertically, and multiple nozzles are arranged in the upper section and the bottom section respectively. The flow rate and / or spraying duration of the nozzles in the bottom section are controlled to be less than the flow rate and / or spraying duration of the nozzles in the upper section. The substrate reciprocates relative to the spray disc along a first direction, which is parallel to the substrate. By controlling one or more of the following: the moving speed of the substrate, the flow rate of the nozzles on the spray disc, and the spraying duration of the nozzles, the amount of etching solution received on the surface of the substrate is made to tend to be uniform. Each partition has a pressure chamber located within the spray plate; in step S5, the flow rate of the nozzle is controlled by adjusting the pressure of the etching solution entering the pressure chamber.

2. The preparation method according to claim 1, characterized in that, At least some of the lines have a line width and line spacing of 2~30μm.

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 through holes is also cleaned; in step S1 or 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; liquid is introduced into the first cavity, the liquid being a chemical plating solution or a cleaning solution, and the liquid flows into the second cavity through the through holes 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 holes 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 the liquid level difference in the first cavity and the second cavity, or by evacuating 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, Lines are formed on both surfaces of the substrate, and the conductive layer in the through hole connects the lines on the two surfaces; the substrate is glass, the first conductive layer includes titanium and copper atoms, the second conductive layer is a copper plating or a conductive polymer plating, and the third conductive layer is a copper plating.

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