Boss etching method of circuit board

Abstract

The invention relates to a boss etching method of a circuit board, which comprises the following steps of: pre-treating a substrate, and pasting a photoresist dry film on an area, which needs to form a boss, of the substrate; etching for the first time: enabling the etching surface of the substrate to face upwards, horizontally placing the substrate and etching the substrate; the etching method comprises the following steps: continuously spraying etching liquid on two surfaces of the substrate by adopting an up-and-down spraying system, and controlling the substrate to move at a constant speed from a starting end to a terminal along a horizontal conveying direction; s2, turning over the substrate subjected to the first-time etching by 180 degrees, enabling the etching surface to face downwards and be horizontally arranged, and then etching the substrate by adopting an etching mode which is the same as that in the step S2; and post-processing: removing the photoresist dry film, cleaning and drying to obtain the circuit board with the preset boss. According to the invention, two times of step-by-step etching are combined with a symmetrical spraying mode of an upper spraying system and a lower spraying system, so that the etching liquid is uniformly distributed on the two surfaces of the substrate, and the etching depth deviation caused by a pool effect in a single-surface etching process is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the field of circuit boards, and more particularly to a method for etching bosses on a circuit board. Background Art

[0002] At present, some circuit boards are designed with bosses to support electronic components and improve heat dissipation efficiency. Most bosses are formed by etching. Among them, bosses with a depth greater than 0.4 mm are generally recognized as ultra-deep bosses. In related technologies, the etching method for ultra-deep bosses is usually to place the etching plate surface upward and complete the etching of ultra-deep bosses by reducing the speed and increasing the etching amount. Usually, the etching time is greater than ten minutes.

[0003] However, after the etching solution remains on the plate surface, there will be a pool effect. Where the solution accumulates, the exchange of fresh solution is slow, the etching amount is small. When the etching plate surface is upward, the solution accumulates in the middle area of the plate. When the substrate advances, the solution accumulates at the rear side of the substrate. The pool effect of the etching solution will result in less etching amount in the middle area and the rear side area of the plate, shallower bosses, and a larger etching amount in the edge area of the plate. The depth difference of the bosses on the whole plate is greater than 50 μm, and the uniformity is poor, resulting in a height difference between the finished bosses and the plate surface. Summary of the Invention

[0004] In view of this, the present invention provides a method for etching bosses on a circuit board that can improve the depth uniformity of the bosses on the whole board.

[0005] The purpose of the present invention is achieved by the following technical solutions: A method for etching bosses on a circuit board, comprising the following steps: S1: Substrate pretreatment, laminating a photosensitive dry film on the area of the substrate where bosses need to be formed; S2: First etching, placing the etching surface of the substrate upward and horizontally and performing etching; the etching method is: continuously spraying the etching solution on both sides of the substrate by using an up-and-down spraying system, and at the same time controlling the substrate to move uniformly from the starting end to the terminal along the horizontal conveying direction; S3: Second etching, turning the substrate that has completed the first etching by 180°, making the etching surface downward and horizontally arranged, and then etching the substrate by using the same etching method as in step S2; S4: Post-treatment, removing the photosensitive dry film, performing cleaning and drying to obtain a circuit board with predetermined bosses.

[0006] In the above technical solution, through the 180° flipping operation of the substrate in two etching steps, combined with the symmetric spraying mode of the upper and lower spraying systems, the etching solution is evenly distributed on both sides of the substrate, effectively reducing the etching depth deviation caused by the pool effect during the single-sided etching process. By adding a second etching process, the convex platform that is relatively shallow in the middle of the substrate during the first etching can be quickly etched, and the etching effects in the two flipping and etching processes are neutralized, thereby improving the etching uniformity.

[0007] In addition, through the cooperation of double-sided synchronous spraying and the horizontal and uniform transmission of the substrate, combined with the two flipping operations, the problem of etching lag in the middle area caused by solution retention in the traditional horizontal spraying process is effectively avoided. The secondary etching after flipping can balance the etching rate differences in each area of the board surface and ensure the double-sided etching uniformity.

[0008] Optionally, in a possible implementation manner, the upper and lower spraying systems include two spraying units respectively arranged above and below the substrate, and the spraying units continuously spray the etching solution along the surface normal direction of the substrate.

[0009] In the above technical solution, the spraying units continuously spray along the surface normal direction of the substrate, so that the etching solution impacts the surface of the copper foil in a flat fan-shaped mode, maximizing the contact efficiency between the solution and the substrate. This method can reduce the lateral etching effect and significantly improve the etching factor.

[0010] Optionally, in a possible implementation manner, the spraying unit includes a plurality of nozzles arranged in a linear array or a rectangular array.

[0011] In the above technical solution, the nozzles arranged in a linear or rectangular array can form a dense and regularly distributed spraying grid on the surface of the substrate, eliminating possible coverage blind spots, and through the array arrangement mode, the flow rate distribution of each nozzle can be flexibly adjusted according to the substrate size and the characteristics of the etching area.

[0012] Optionally, in a possible implementation manner, in the spraying unit, the distance between adjacent nozzles is 15 - 25 mm, and the distance between the nozzles and the surface of the substrate is 50 - 80 mm.

[0013] In the above technical solution, by limiting the distance between adjacent nozzles to 15 - 25 mm, it is ensured that the etching solution forms a continuous and gapless covering layer on the surface of the substrate, avoiding local under-etching or over-etching phenomena caused by too large a distance. The nozzles maintain a vertical distance of 50 - 80 mm from the surface of the substrate, which can not only ensure that the etching solution impacts the surface of the copper foil with sufficient kinetic energy to improve the reaction efficiency, but also avoid problems such as excessive droplet splashing or dry film damage caused by too close a distance.

[0014] Optionally, in a possible implementation, the etching depth of the first etching in step S2 is 60%-70% of the total depth of the boss; the second etching in step S3 completes the etching of the remaining 30%-40% of the boss depth.

[0015] In the above technical solution, the first etching completes 60%-70% of the total depth, quickly forms the main structure through a large etching amount, reduces the overall processing time; the second etching supplements the remaining 30%-40%, and finely adjusts the boss morphology using a low etching amount to improve the fineness of the boss.

[0016] Optionally, in a possible implementation, when the substrate is flipped during the second etching, it is flipped 180° around an axis perpendicular to the moving direction of the substrate.

[0017] The flipping method in the above technical solution enables the middle and rear parts with a shallower etching amount during the first etching to be etched first during the second etching, so that the etching time can be more precisely controlled, ensuring sufficient reaction time for the second etching, ensuring complete etching of the boss, and also facilitating flexible adjustment.

[0018] Optionally, in a possible implementation, the substrate is provided with marking holes, the marking holes are located at any one or more of the four corners of the substrate, and the number of the marking holes is 1-3.

[0019] In the above technical solution, the marking holes play an anti-fooling role, provide a reliable space coordinate system for the flipping operation during the double-sided etching process, facilitate positioning, can effectively prevent the operator from making a wrong direction during the flipping, and improve the consistency of batch substrate etching.

[0020] Optionally, in a possible implementation, in step S1, before laminating the dry film photoresist, the substrate is first subjected to a surface cleaning treatment, and the surface cleaning treatment can adopt water washing, chemical solvent cleaning or plasma cleaning.

[0021] In the above technical solution, through water washing, chemical solvent or plasma cleaning technology, the grease, oxides and organic residues on the substrate surface can be effectively stripped, realizing molecular-level cleaning. After the pretreatment, the surface energy of the substrate is significantly improved. Especially, plasma cleaning can form a micro-roughened structure on the copper foil surface, improve the bonding strength between the dry film and the substrate, and effectively prevent pattern distortion caused by the penetration of the etching solution.

[0022] Optionally, in a possible implementation, between steps S2 and S3, an artificial loading process is further included. The artificial loading process is to pick up the substrate after the first etching from the terminal and place it on a movable plug-in board rack, and then move the plug-in board rack to the starting end.

[0023] In the above technical solution, by setting an artificial transfer link between two etching processes, segmented process control is achieved, avoiding equipment idle waiting in continuous automated production. And the artificial operation of the plug-in board rack can accurately adjust the placement posture of the substrate, avoiding surface scratches or stress deformation that may be caused by the robotic arm grasping.

[0024] Optionally, in a possible implementation manner, the steps S2 and S3 further include an inspection process, in which a laser rangefinder is used to measure the etching depth.

[0025] In the above technical solution, based on the non-contact measurement principle, the laser rangefinder can obtain depth data in real time during the etching process. Based on the real-time measured etching depth data, key parameters such as the spraying intensity and time of the etching solution can be automatically adjusted to eliminate depth deviations caused by equipment fluctuations or material batch differences, ensuring that the depth ratio in the two etching stages is strictly controlled within the ranges of 60%-70% and 30%-40%. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 It is a schematic diagram of the overall process of an embodiment.

[0028] Figure 2 It is a schematic diagram of the structure of the first etching of an embodiment.

[0029] Figure 3 It is a schematic diagram of the structure of the second etching of an embodiment.

[0030] Reference numerals: 1 - substrate; 2 - nozzle; 3 - boss; 4 - accumulated liquid. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Usually, the components of the embodiments of the present application described and illustrated in the drawings here can be arranged and designed in various different configurations.

[0032] Accordingly, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but merely represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts fall within the scope of protection of the present application.

[0033] Please refer to Figure 1 , this embodiment provides a method for etching the boss 3 of a circuit board, including the following steps: S1: Pretreatment of the substrate 1, laminating a photosensitive dry film on the area of the substrate 1 where the boss 3 needs to be formed; S2: First etching, placing the etching surface of the substrate 1 facing up and horizontally and performing etching; the etching method is: continuously spraying the etching solution on both sides of the substrate 1 using an up-and-down spraying system, while controlling the substrate 1 to move uniformly from the starting end to the terminal along the horizontal conveying direction; wherein, the etching solution is an acidic copper chloride etching solution, its pH value is controlled within the range of 1.8 - 2.3, the copper ion concentration is maintained at 120 - 160 g / L, and the substrate 1 starts etching from the starting end of the etching line and leaves from the end of the etching line; S3: Second etching, flipping the substrate 1 that has completed the first etching by 180°, making the etching surface face down and horizontally arranged, and then etching the substrate 1 using the same etching method as in step S2; S4: Post-treatment, removing the photosensitive dry film, performing cleaning and drying to obtain a circuit board with a predetermined boss 3. Specifically, an alkaline solution can be used to strip and remove the photosensitive dry film, and after performing ultrasonic cleaning, deionized water rinsing, and hot air drying in sequence, a circuit board is obtained.

[0034] In this embodiment, through the 180° flipping operation of the substrate 1 in the two etching steps, combined with the symmetric spraying mode of the up-and-down spraying system, the etching solution is evenly distributed on both sides of the substrate 1, effectively reducing the etching depth deviation caused by the pool effect during the single-sided etching process. By adding the second etching process, the boss 3 that is relatively shallow in the middle of the substrate 1 during the first etching can be quickly etched, and the etching effects are neutralized by the two-sided flipping etching, thereby improving the etching uniformity.

[0035] In addition, through the cooperation of double-sided synchronous spraying and the horizontal uniform conveying of the substrate 1, combined with the two flipping operations, the problem of etching lag in the middle area caused by solution retention in the traditional horizontal spraying process is effectively avoided. The secondary etching after flipping can balance the etching rate differences in each area of the board surface and ensure the uniformity of double-sided etching.

[0036] In this embodiment, the upper and lower spraying systems include two spraying units respectively arranged above and below the substrate 1, and the spraying units continuously spray the etching solution along the normal direction of the surface of the substrate 1. Among them, the spraying unit includes a plurality of nozzles 2 arranged in a linear array or a rectangular array.

[0037] The spraying unit continuously sprays along the normal direction of the surface of the substrate 1, so that the etching solution impacts the surface of the copper foil vertically in a flat fan-shaped mode, maximizing the contact efficiency between the solution and the substrate 1. This method can reduce the lateral etching effect and significantly improve the etching factor. In addition, the continuous liquid supply mechanism of the upper and lower two spraying units maintains the dynamic balance of the concentration, temperature and fluidity of the etching solution, preventing the local solution from failing due to the accumulation of reaction products.

[0038] The nozzles 2 arranged in a linear or rectangular array can form a dense and regularly distributed spraying grid on the surface of the substrate 1, eliminating possible coverage blind spots, and through the array arrangement mode, the flow distribution of each nozzle 2 can be flexibly adjusted according to the size of the substrate 1 and the characteristics of the etching area.

[0039] It should be noted that in the spraying unit of this embodiment, the distance between adjacent nozzles 2 is 15 - 25 mm, and the distance between the nozzle 2 and the surface of the substrate 1 is 50 - 80 mm.

[0040] By limiting the distance between adjacent nozzles 2 to 15 - 25 mm, it is ensured that the etching solution forms a continuous and gapless covering layer on the surface of the substrate 1, avoiding local under-etching or over-etching phenomena caused by too large a distance. The nozzle 2 maintains a vertical distance of 50 - 80 mm from the surface of the substrate 1, which can not only ensure that the etching solution impacts the surface of the copper foil with sufficient kinetic energy to improve the reaction efficiency, but also avoid problems such as excessive splashing of droplets or damage to the dry film caused by too close a distance.

[0041] In the first etching in step S2 of this embodiment, the etching depth is 60% - 70% of the total depth of the boss 3; in step S3, the second etching completes the etching of the remaining 30% - 40% of the depth of the boss 3. For example, in this embodiment, the first etching is 70% of the total depth of the boss 3, and the second etching is 30% of the total depth of the boss 3.

[0042] The first etching completes 60% - 70% of the total depth, quickly forming the main structure through a large etching amount, reducing the overall processing time; the second etching supplements the remaining 30% - 40%, using a low etching amount to finely adjust the morphology of the boss 3 and improve the fineness of the boss 3. And the staged decreasing of the etching amount can reduce the side etching effect of a single etching, and the side wall profile generated by the first etching is symmetrically compensated by flipping the spraying during the second etching.

[0043] In this embodiment, when the substrate 1 is flipped during the second etching, it is flipped by 180° around an axis perpendicular to the moving direction of the substrate 1. That is to say, during the first etching, one end of the substrate 1 first enters the upper and lower spraying system for spraying, and during the second etching, the other end of the substrate 1 first enters the upper and lower spraying system for spraying, thereby improving the etching uniformity.

[0044] This flipping method enables the middle and rear parts with relatively shallow etching amounts during the first etching to be etched first during the second etching, so that the etching time can be more precisely controlled, ensuring sufficient reaction time for the second etching, ensuring complete etching of the boss 3, improving the etching uniformity, and also facilitating flexible adjustment.

[0045] Marking holes are provided on the substrate 1 of this embodiment. The marking holes are located at any one or more of the four corners of the substrate 1, and the number of marking holes is 1 - 3. The marking holes play an anti-fooling role, providing a reliable space coordinate system for the flipping operation during the double-sided etching process, facilitating positioning, effectively avoiding the wrong direction of the operator during flipping, and improving the consistency of batch etching of the substrate 1.

[0046] In step S1 of this embodiment, before laminating the photosensitive dry film, the surface of the substrate 1 is first subjected to surface cleaning treatment. The surface cleaning treatment can be carried out by water washing, chemical solvent cleaning or plasma cleaning.

[0047] Through water washing, chemical solvents or plasma cleaning technology, the grease, oxides and organic residues on the surface of the substrate 1 can be effectively stripped, achieving molecular-level cleaning. After pretreatment, the surface energy of the substrate 1 is significantly improved. In particular, plasma cleaning can form a micro-roughened structure on the surface of the copper foil, improving the bonding strength between the dry film and the substrate 1, and effectively preventing pattern distortion caused by the penetration of the etching solution. The three cleaning methods form a gradient treatment plan - water washing quickly removes particulate pollutants, chemical solvents specifically dissolve organic residues, and plasma treatment realizes ultimate surface modification, which can be combined and optimized according to different substrate 1 materials and pollutant types.

[0048] Between steps S2 and S3 of this embodiment, an artificial loading process is further included. The artificial loading process is to pick up the substrate 1 after the first etching from the terminal and place it on a movable plug-in board rack, and then move the plug-in board rack to the starting end.

[0049] By setting an artificial transfer link between the two etching processes, segmented process control is realized, avoiding equipment idle waiting in continuous automated production. And the operator can precisely adjust the placement posture of the substrate 1 by operating the plug-in board rack, avoiding surface scratches or stress deformation that may be caused by the mechanical arm grasping.

[0050] It should be noted that the detection process is also included in steps S2 and S3. In the detection process, a laser rangefinder is used to measure the etching depth. Based on the non-contact measurement principle, the laser rangefinder can obtain the depth data in real time during the etching process. Based on the real-time measured etching depth data, key parameters such as the spraying intensity and time of the etching solution can be automatically adjusted to eliminate the depth deviation caused by equipment fluctuations or material batch differences, and ensure that the depth ratio in the two etching stages is strictly controlled within the range of 60%-70% and 30%-40%.

[0051] In this embodiment, by optimizing the etching process for the formation of the boss 3, the depth range difference of the bosses 3 on the entire board is reduced, and the uniformity of the depth of the bosses 3 is improved. Specifically, through two-step etching. During the first etching, the board is placed with the etching surface facing up. At this time, the marking hole is located in the upper right corner of the etching surface with the etching surface as the reference, and the etching depth is 70% of the total depth. The etching solution is continuously sprayed on the two board surfaces through the nozzle 2. The solution keeps flowing, but the solution in the middle area of the board cannot flow away quickly, forming a solution pool 4. The substrate 1 advances in the etching line, that is, the upper and lower spraying systems. The solution pool 4 moves backward. The solution on the edge of the board surface flows through the board edge and then accumulates in the lower edge area of the substrate 1 and then detaches from the board surface. In the area of the solution pool 4 on the board surface, the fresh solution cannot be quickly sprayed onto the board surface for the copper etching reaction, and the etching rate in the middle area is slower than that in the edge area of the board, that is, the pool effect. After the substrate 1 is etched upward, the depth of the bosses 3 in the middle and rear sections of the board surface is shallower than that in the edge area. Therefore, if the over-deep bosses 3 are etched in one go, the depth range difference between the middle area and the edge area of the board will increase, resulting in poor uniformity of the depth of the bosses 3.

[0052] After the first upward etching is completed, the board is manually picked up from the end of the etching line, placed centrally using a board rack, and transferred to the board placement area at the starting section of the etching line for the second etching. During the second etching, the etching surface faces down, and the etching direction is reversed front and back. At this time, with the etching surface as the reference, the marking hole is in the lower right corner, and the remaining 30% of the depth etching is completed. When etching with the etching surface facing down, the solution accumulates at the lower edge position of the substrate 1 to form a solution pool 4, and there is no solution pool 4 in the middle area under the substrate 1. Therefore, when the substrate 1 is etched downward, the pool effect occurs in the edge area of the board, and the solution exchange speed at the board edge is slower than that in the middle of the board, that is, the etching speed at the board edge is slower than that in the middle of the board, which is opposite to the upward etching. When the first etching is completed, the depth of the bosses 3 in the edge area of the board is greater than that in the middle area of the board. When etching downward for the second time, the etching effect in the middle of the board is stronger than that at the board edge. Therefore, the height range difference of the bosses 3 caused by the upward etching is neutralized, and the depth range difference of the bosses 3 on the entire board after adjustment ≤ 30um.

[0053] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by terms such as "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0054] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0055] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for etching bosses on a circuit board, characterized in that It includes the following steps: S1: Substrate pretreatment, laminating a dry photoresist film on the area of the substrate where bosses need to be formed; S2: First etching, placing the etched surface of the substrate upward and horizontally and performing etching; the etching method is: continuously spraying the etching solution on both sides of the substrate by using an upper and lower spraying system, and at the same time controlling the substrate to move uniformly from the starting end to the terminal along the horizontal conveying direction; S3: Second etching, flipping the substrate that has completed the first etching by 180°, making the etched surface face downward and horizontally setting it, and then etching the substrate by using the same etching method as in step S2; S4: Post-treatment, removing the dry photoresist film, performing cleaning and drying to obtain a circuit board with predetermined bosses.

2. The method for etching the boss of the circuit board according to claim 1, characterized in that, The upper and lower spraying system includes two spraying units respectively arranged above and below the substrate, and the spraying units continuously spray the etching solution along the normal direction of the surface of the substrate.

3. The method for etching the boss of the circuit board according to claim 2, characterized in that, The spraying unit includes a plurality of nozzles arranged in a linear array or a rectangular array.

4. The method for etching the boss of the circuit board according to claim 3, characterized in that, In the spraying unit, the distance between adjacent nozzles is 15 - 25 mm, and the distance between the nozzle and the substrate surface is 50 - 80 mm.

5. The method for etching the boss of the circuit board according to claim 1, wherein In the first etching in step S2, the etching depth is 60% - 70% of the total depth of the bosses; in the second etching in step S3, the remaining 30% - 40% of the boss depth is etched.

6. The method for etching the boss of the circuit board according to claim 1, wherein, When the substrate is flipped in the second etching, it is flipped by 180° around an axis perpendicular to the moving direction of the substrate.

7. The method for etching the boss of the circuit board according to claim 6, wherein Marking holes are provided on the substrate, the marking holes are located at any one or more of the four corners of the substrate, and the number of the marking holes is 1 - 3.

8. The method for etching the boss of the circuit board according to claim 1, wherein In step S1, before laminating the dry photoresist film, the surface of the substrate is first subjected to surface cleaning treatment, and the surface cleaning treatment can be carried out by water washing, chemical solvent cleaning or plasma cleaning.

9. The method for etching the boss of the circuit board according to claim 1, wherein, Between step S2 and S3, an artificial loading process is further included, and the artificial loading process is to centrally pick up the substrate that has completed the first etching from the terminal and place it on a movable plug-in board rack, and then move the plug-in board rack to the starting end.

10. The method for etching the boss of the circuit board according to claim 1, wherein A detection process is also included in step S2 and step S3. In the detection process, a laser rangefinder is used to measure the etching depth.

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