Long and short golden finger preparation method based on laser hollowing-out technology

Abstract

The invention relates to the technical field of surface treatment of printed circuit boards, and discloses a method for preparing long and short golden fingers based on a laser hollowing-out technology, which comprises the following steps of: performing solder mask treatment on a printed circuit board of which the outer circuit is manufactured, and reserving a windowing area at a position where a golden finger is to be formed, auxiliary conductive wires are arranged at the root positions of the long and short golden fingers to be connected with the golden fingers with different lengths, and the auxiliary conductive wires are covered by solder mask ink; and an electrogilding dry film is pressed in the windowing area and the in-board non-gilding area, so that the copper surface of the gold finger to be gilded is exposed, and the auxiliary conductive wire is protected by the solder mask ink and is not covered by the dry film. The long and short golden finger preparation method based on the laser hollowing-out technology aims at solving the problems that gold suspension residues exist at the front end of an existing long and short golden finger, the process is tedious, the working procedures are repeated, the production efficiency is low, and multiple times of solder mask and dry film treatment are needed in the auxiliary electric lead removing process in the preparation process.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board surface treatment technology, specifically a method for preparing long and short gold fingers based on laser hollowing technology. Background Technology

[0002] In the field of printed circuit board manufacturing, the long and short gold finger process is used to selectively plate gold fingers of different lengths to meet the electrical performance requirements of multi-segment pluggable connectors. Since the front end of the short gold finger and the middle of the long gold finger are at the same level, it is necessary to ensure that gold fingers of different lengths can pass through current for gold plating during electroplating. Therefore, temporary conductive paths need to be set between the gold fingers. Existing technologies mainly adopt two solutions: one is selective wet film printing process, which prints a wet film to protect the front end of the short gold finger. After electroplating, the wet film is peeled off and the conductive connection part at the front end of the short gold finger is etched away. The other is the in-board wire-drawing secondary solder mask process, which lays auxiliary conductive lines in the board to connect each gold finger. After electroplating, the auxiliary conductive line area is selectively exposed through secondary solder mask, secondary dry film lamination, exposure and development and other processes, and then etched away.

[0003] However, the aforementioned existing technologies suffer from technical problems such as lengthy process flow and low production efficiency. Selective wet film printing requires multiple steps, including wet film printing, exposure, development, and peeling. Furthermore, the accuracy of wet film printing is greatly affected by equipment and operation, which can easily lead to uneven gold plating at the tip of short gold fingers or defects such as suspended gold. Although the in-board wire-drawing secondary solder resist process avoids the process problems at the tip of short gold fingers, it requires secondary solder resist treatment and secondary dry film lamination, exposure, and development processes after electroplating to expose the auxiliary conductive lines for etching. The overall process flow has high repeatability and a long production cycle. Moreover, the registration accuracy between the secondary solder resist and the original solder resist layer is strictly required, which increases the difficulty of process control and production costs. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of suspended gold residue at the front end of the gold finger in the existing long and short gold finger manufacturing process, which is characterized by a long process, repetitive steps, low production efficiency, and the need for multiple solder resist and dry film treatments in the auxiliary conductive wire removal process. Therefore, a method for manufacturing long and short gold fingers based on laser hollowing technology is proposed.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A method for preparing long and short gold fingers based on laser hollowing technology includes the following steps: S1. Solder resist treatment is applied to the printed circuit board after the outer layer circuit is fabricated. A window area is reserved at the position where gold fingers are to be formed. Auxiliary conductive lines are set at the root position of gold fingers of different lengths to connect gold fingers of different lengths. The auxiliary conductive lines are covered with solder resist ink. S2. Press the electroplated gold dry film onto the windowed area and the non-gold-plated area inside the board to expose the copper surface of the gold fingers to be plated. The auxiliary conductive line is protected by solder resist ink and is not covered by the dry film. S3. Electroplating nickel-gold is performed on the exposed gold finger area to form gold-plated fingers of different lengths. S4. Use a laser scavenging process to remove the solder resist ink from the surface of the auxiliary conductive wire, exposing the copper surface of the auxiliary conductive wire; S5. Using the electroplated gold dry film from S2 as a resist layer, alkaline etching is performed on the exposed auxiliary conductive lines to remove them. S6. Remove the dry film of electroplated gold to complete the preparation of long and short gold fingers.

[0006] Based on the above technical solution, the present invention can be further improved as follows.

[0007] Furthermore, in S1, the auxiliary conductive line is set on the side of the gold finger root near the solder resist area inside the board. The circuit shape of the auxiliary conductive line is arranged perpendicularly or obliquely to the gold finger arrangement direction, so that the auxiliary conductive line can connect all the gold fingers of different lengths that need to be electroplated laterally, forming a unified current path.

[0008] Furthermore, the placement of the auxiliary conductive line in S1 enables the gold finger tip to form a three-sided gold-plated structure during electroplating. By controlling the relative position of the auxiliary conductive line and the gold finger tip, the phenomenon of suspended gold at the gold finger tip is avoided, ensuring the integrity and conductivity of the electroplated layer.

[0009] Furthermore, the solder resist ink used in S1 is a laser-removable ink, which can be selectively decomposed or vaporized under laser irradiation. The precise removal of the solder resist ink can be achieved by adjusting the laser wavelength, energy density, and scanning speed.

[0010] Furthermore, in S2, the gold-plated dry film is laminated using selective lamination, and solder resist ink provides primary protection.

[0011] Furthermore, the laser scouring process used in S4 is performed directly after the gold plating is completed, retaining the dry gold plating film without peeling it off. The laser beam only acts on the solder resist ink layer, and the layer removal is achieved through energy control. This allows the etching process in S5 to directly reuse the dry gold plating film as the anti-corrosion layer, avoiding the secondary lamination process.

[0012] Furthermore, the nickel-gold electroplating process in S3 includes first electroplating a nickel layer and then electroplating a gold layer. The nickel layer serves as a barrier layer to prevent the diffusion of copper, while the gold layer serves as a surface conductive layer and an anti-oxidation layer. The simultaneous electroplating of long and short gold fingers is achieved through the current path provided by the auxiliary conductive wire.

[0013] Furthermore, the alkaline etching in S5 uses an amino etching solution or other alkaline etching system. The auxiliary conductive lines are removed by selectively dissolving the exposed copper surface through the etching solution. During the etching process, the electroplated gold dry film and the gold plating layer provide etching protection for the covered area. After the etching is completed, a blank area flush with the solder resist layer is formed at the position of the auxiliary conductive lines.

[0014] Furthermore, the method replaces the traditional selective wet film printing process with laser hollowing technology, eliminating the processes of wet film printing, exposure, development, and peeling. At the same time, by reusing electroplated gold dry film as the resist layer for secondary etching, the repetitive processes of secondary solder resist, secondary dry film lamination, exposure, and development in the in-board wire drawing process are avoided.

[0015] Furthermore, selective removal of different protective layers can be achieved by laser-removing resin or ink. The design of auxiliary conductive lines is not limited by the original circuit network layout within the board, and no secondary solder resist and ink repair treatment is required after removing the auxiliary conductive lines.

[0016] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: This invention places the auxiliary conductive line at the root of the gold finger rather than its tip, allowing the gold finger tip to form a complete three-sided gold-plated structure during electroplating. This fundamentally avoids the suspended gold defects and uneven gold plating caused by short gold finger tip conductive connections in selective wet film printing, thus improving the electrical performance and reliability of the product. Secondly, laser removal technology is used to directly remove the solder resist ink covering the auxiliary conductive line. Selective removal of the solder resist ink is achieved through precise control of laser parameters, eliminating the need for cumbersome processes such as wet film printing, exposure, development, and stripping, significantly simplifying the process. The high precision of laser processing also avoids the instability problem of traditional wet film printing. More importantly, this invention directly reuses the already laminated electroplated gold dry film as an etching resist layer after laser removal, eliminating the need for repetitive processes such as secondary solder resist treatment, secondary dry film lamination, exposure, and development required in in-board wire-drawing secondary solder resist processes. This eliminates the difficulty of controlling the registration accuracy of secondary solder resist, significantly reducing the number of processes and production cycle, lowering process control difficulty and production costs, and achieving multiple technical effects of process simplification, efficiency improvement, and cost reduction. Attached Figure Description

[0017] Figure 1 This is the main production process for the product of this invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figure 1 As shown, this embodiment provides a method for preparing long and short gold fingers based on laser hollowing technology, which is applied to the surface treatment process of gold fingers on multilayer printed circuit boards. The specific process flow is as follows: Step S1: Solder shielding and setting up auxiliary conductive lines Solder resist is applied to the printed circuit board after the outer layer circuitry is fabricated. Photosensitive or thermosetting solder resist ink is applied to the board surface via screen printing or spraying. After exposure and development, an opening area is reserved at the location where the gold fingers will form, exposing the copper surface of the gold finger area. Simultaneously, auxiliary conductive lines are placed at the base of gold fingers of different lengths to connect them; these auxiliary conductive lines are covered with solder resist ink.

[0020] Specifically, the auxiliary conductive line is located at the root of the gold finger, near the solder resist area within the board. Unlike traditional processes where the conductive connection is located at the front end of the short gold finger, this invention moves the auxiliary conductive line to the root position. The auxiliary conductive line is arranged perpendicularly or obliquely to the gold finger arrangement direction, forming a horizontal strip structure that runs through all gold fingers. This allows the auxiliary conductive line to horizontally connect all gold fingers of varying lengths that require electroplating, forming a unified current path. In this embodiment, the line width of the auxiliary conductive line is set to 5 mil, and the width of the solder resist ink covering it is 6 mil. The edge of the solder resist ink maintains a 2.5 mil single-sided spacing with the edge of the adjacent gold finger, ensuring that the edge-to-edge spacing between adjacent gold fingers is not less than 8 mil, meeting the production process requirements.

[0021] The placement of the auxiliary conductive line ensures that the gold finger tip forms a three-sided gold-plated structure during electroplating, meaning the top and two sides of the gold finger are completely covered by the gold plating layer. By controlling the relative position of the auxiliary conductive line to the gold finger tip, the phenomenon of "floating gold" is avoided. Floating gold refers to an isolated plating area at the gold finger tip, which is not firmly connected to the main copper surface and is easily detached during insertion and removal. This invention ensures the integrity and conductivity of the plating layer by supplying power at the root. Current flows from the root auxiliary conductive line through the entire gold finger to the tip, forming a continuous and uniform plating layer.

[0022] Step S2: Lamination of electroplated gold dry film A dry film for electroplating is laminated onto the windowed area and the non-gold-plated areas within the board. A vacuum laminator or hot press rollers are used to attach the dry film to the board surface. The heating temperature is set to 100-120℃, and the pressure is controlled at 0.3-0.5MPa, exposing the copper surface of the gold fingers to be plated. Since the auxiliary conductive lines are protected by solder resist ink and not covered by the dry film, the dry film only covers the surface of the solder resist area at the base of the gold fingers and other non-gold-plated areas within the board.

[0023] The gold-plated dry film is laminated using a selective lamination method. Through a pre-designed window pattern, the dry film simultaneously covers the non-gold-plated areas within the board. In this dual-protection structure, the solder resist ink provides primary protection, directly covering the copper surface of the auxiliary conductive lines and exhibiting excellent chemical stability. The gold-plated dry film provides secondary protection, covering the surface of the solder resist ink and other areas within the board, preventing electroplating reactions in the non-gold-plated areas during subsequent electroplating. This dual-protection structure enhances the reliability of protection for the auxiliary conductive line areas, preventing electroplating solution penetration that could lead to abnormal gold plating.

[0024] Step S3: Nickel-gold plating treatment The exposed gold finger areas are electroplated with nickel-gold to form gold-plated fingers of varying lengths. The electroplating process is completed on a dedicated electroplating production line, with the sheet material used as the cathode immersed in the electroplating tank and connected to the negative terminal of the power supply via a hanger or flybar.

[0025] The nickel-gold electroplating process involves first electroplating a nickel layer, followed by electroplating a gold layer. A nickel layer is deposited on the surface of the gold fingers using either electroless or electroplating processes. This nickel layer acts as a barrier layer to prevent copper diffusion and avoids copper atoms migrating to the gold layer, which could lead to discoloration or performance degradation. The nickel layer thickness is controlled at 3-6 μm, preferably 5 μm. Subsequently, a gold layer is electroplated on the nickel layer. The gold layer serves as a conductive and antioxidant layer, providing excellent conductivity and corrosion resistance. The gold layer thickness is 0.05-0.3 μm, preferably 0.1 μm. The electroplating process parameters are: plating bath temperature 50-65℃, current density 0.5-2 A / dm³. 2 The pH value should be controlled between 4.0 and 5.5.

[0026] During the electroplating process, the synchronous electroplating of long and short gold fingers is achieved through a current path provided by an auxiliary conductive line. The current travels from the fixture through the circuitry within the board to the auxiliary conductive line, and is then distributed to each gold finger, ensuring that all gold fingers participate in the electroplating reaction simultaneously, resulting in a uniform plating thickness. This root-powered method solves the problem of uneven current distribution on short gold fingers due to their distance from the power source in traditional processes.

[0027] Step S4: Laser hollowing process The solder resist ink on the surface of the auxiliary conductive wire is removed using a laser hollowing process, exposing the copper surface of the auxiliary conductive wire. This step is a key innovative process of this invention.

[0028] The laser removal process is performed directly after gold plating, preserving the dry gold film without peeling it off. Unlike traditional processes that require removing the dry film before subsequent treatment, this invention utilizes the selective processing characteristics of lasers to treat localized areas while preserving the dry film. Using ultraviolet or CO2 laser equipment, the laser beam acts solely on the solder resist ink layer. The laser beam is focused on the solder resist ink surface above the auxiliary conductive line, achieving layered removal through energy control. The laser energy is absorbed by the ink and converted into heat, causing photochemical or thermal decomposition of the ink, generating gaseous small molecules that escape, thus achieving ink removal.

[0029] The laser processing parameters were set as follows: wavelength 355nm, pulse frequency 30-50kHz, scanning speed 200-500mm / s, with repeated scanning 2-3 times to ensure complete ink removal. A CCD vision system was used for positioning and alignment to ensure the laser path precisely covered the auxiliary conductive line area. After processing, the copper surface of the auxiliary conductive line was fully exposed, while the adjacent gold-plated layer of the gold fingers and the electroplated gold dry film remained intact, demonstrating the high precision characteristics of the laser process.

[0030] The S5 etching process can directly reuse the electroplated gold dry film as the resist layer, avoiding the secondary lamination process. This is an important advantage of the present invention compared with the prior art. The traditional in-board wire drawing process requires the removal of the dry film after electroplating, and then secondary solder resist or secondary lamination to protect other areas for selective etching. The present invention achieves the reuse of the resist layer through the optimization of the process sequence.

[0031] Step S5: Alkaline etching to remove auxiliary conductive lines Using the electroplated gold dry film from step S2 as a resist layer, the exposed auxiliary conductive lines are subjected to alkaline etching to remove them. The substrate is then fed into an alkaline etching apparatus, where the etching solution is brought into contact with the substrate surface via spraying or immersion.

[0032] Alkaline etching uses amino-based etching solutions or other alkaline etching systems. Common formulations include ammonia, ammonium carbonate, and ammonium chloride. The etching solution temperature is controlled at 40-50℃, and the pH value is 8.5-10.0. The auxiliary conductive lines are removed through the selective dissolution of the exposed copper surface by the etching solution. Copper reacts chemically with the etching solution to form a soluble copper-ammonia complex, which is carried away by the etching solution. During the etching process, the electroplated gold dry film and gold plating layer provide etching protection to the covered area. The electroplated gold dry film has good alkali resistance, and the gold plating layer itself does not react with the alkaline etching solution; therefore, the gold finger area and other circuits within the board are unaffected.

[0033] The etching time is determined based on the copper thickness of the auxiliary conductive line. For a 1oz copper thickness (35μm), the etching time is approximately 3-5 minutes. The etching progress is monitored visually or through an online inspection system to ensure complete removal of the auxiliary conductive line without over-etching. After etching, a blank area flush with the solder mask is formed at the location of the auxiliary conductive line. Because the underlying substrate is exposed, this area will exhibit a different color from the solder mask after subsequent cleaning and drying. However, since it is located at the root of the gold finger close to the board, it does not affect the appearance and function of the gold finger.

[0034] Step S6: Remove the dry film from the electroplated gold The electroplated gold dry film is removed to complete the preparation of long and short gold fingers. An alkaline or organic solvent-based stripping solution is used, and the dry film is swollen and peeled off by spraying or immersion. The stripping temperature is controlled at 50-60℃, and the processing time is 3-5 minutes. After stripping, the fingers are rinsed with clean water to remove residual stripping solution and dry film fragments. Finally, they are dried with hot air or in an oven to obtain long and short gold fingers with a clean surface and complete plating. At this point, the gold finger tip exhibits a complete three-sided gold-plated structure, the auxiliary conductive lines at the root have been completely removed, and there are no conductive connections between the gold fingers, meeting the electrical performance requirements.

[0035] This invention replaces the traditional selective wet film printing process with laser-based laser etching technology. The traditional process requires printing a protective wet film on the tip of the short gold fingers, involving wet film preparation, alignment printing, exposure, and development. This results in significant equipment investment and printing accuracy is affected by operational factors. This invention eliminates the wet film printing, exposure, development, and peeling processes, directly using laser equipment for digital processing. This shortens the process flow by approximately 12% and reduces the production cycle by 1-2 days. Furthermore, by reusing electroplated gold dry film as the resist layer for secondary etching, it avoids repetitive steps such as secondary solder resist, secondary dry film lamination, exposure, and development in the in-board wire drawing process, reducing the number of processes and material consumption, and lowering the difficulty of registration accuracy control.

[0036] This invention achieves selective removal of different protective layers by laser-removing resin or ink. It is applicable not only to solder resist inks but also to other organic protective layers such as dry film photoresists and resin-filled via materials, offering broad process compatibility. The design of the auxiliary conductive lines is not limited by the original circuit network layout on the board; only sufficient space needs to be reserved at the root of the gold fingers. Unlike traditional in-board wire drawing processes, it does not require consideration of the connection relationship with inner layer circuitry, allowing for high design freedom. After removing the auxiliary conductive lines, no secondary solder resist re-inking is needed because the auxiliary conductive lines are located at the root of the gold fingers near the in-board solder resist layer. This area does not affect the insertion and removal function of the gold fingers or aesthetic requirements, simplifying post-processing steps.

[0037] This invention is also applicable to printed circuit boards that simultaneously have stepped gold fingers and a mixed design of long and short gold fingers. Stepped gold fingers refer to gold fingers that are distributed in a stepped manner in the thickness direction. Multiple gold finger structures can be compositely processed on the same board surface through laser hollowing technology.

[0038] In another embodiment, the auxiliary conductive lines can be designed in a grid or segmented manner. Multiple thin auxiliary conductive lines are connected in parallel to the gold fingers to further improve the uniformity of current distribution. Each segment of the auxiliary conductive line is removed separately when the laser is removed, thereby improving the processing flexibility.

[0039] In another embodiment, for ultra-long gold fingers or high-density gold finger arrays, auxiliary conductive lines can be set at both ends of the gold finger array to form a dual-end power supply structure, which further improves the current distribution and enhances the uniformity of the coating.

[0040] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing long and short gold fingers based on laser hollowing technology, characterized in that, Includes the following steps: S1. Solder resist treatment is applied to the printed circuit board after the outer layer circuit is fabricated. A window area is reserved at the position where gold fingers are to be formed, and auxiliary conductive lines are set at the root position of gold fingers of different lengths to connect gold fingers of different lengths. The auxiliary conductive lines are covered with solder resist ink. S2. Press the electroplated gold dry film onto the windowed area and the non-gold-plated area inside the board to expose the copper surface of the gold fingers to be plated. The auxiliary conductive line is protected by solder resist ink and is not covered by the dry film. S3. Electroplating nickel-gold is performed on the exposed gold finger area to form gold-plated fingers of different lengths. S4. Use a laser scavenging process to remove the solder resist ink from the surface of the auxiliary conductive wire, exposing the copper surface of the auxiliary conductive wire; S5. Using the electroplated gold dry film from S2 as a resist layer, alkaline etching is performed on the exposed auxiliary conductive lines to remove them. S6. Remove the dry film of electroplated gold to complete the preparation of long and short gold fingers.

2. The method for preparing long and short gold fingers based on laser hollowing technology according to claim 1, characterized in that, In S1, the auxiliary conductive line is set on the side of the gold finger root near the solder resist area inside the board. The line shape of the auxiliary conductive line is arranged perpendicularly or obliquely to the gold finger arrangement direction, so that the auxiliary conductive line can connect all the gold fingers of different lengths that need to be electroplated laterally, forming a unified current path.

3. The method for preparing long and short gold fingers based on laser hollowing technology according to claim 2, characterized in that, The placement of the auxiliary conductive line in S1 enables the gold finger tip to form a three-sided gold-plated structure during electroplating. By controlling the relative position of the auxiliary conductive line and the gold finger tip, the phenomenon of suspended gold at the gold finger tip is avoided, ensuring the integrity and conductivity of the electroplated layer.

4. The method for preparing long and short gold fingers based on laser hollowing technology according to claim 3, characterized in that, The solder resist ink used in S1 is a laser-removable ink. This ink can be selectively decomposed or vaporized under laser irradiation. The precise removal of the solder resist ink can be achieved by adjusting the laser wavelength, energy density, and scanning speed.

5. The method for preparing long and short gold fingers based on laser hollowing technology according to claim 1, characterized in that, The electroplated gold dry film in S2 is laminated using selective lamination, and the solder resist ink provides primary protection.

6. The method for preparing long and short gold fingers based on laser hollowing technology according to claim 1, characterized in that, The laser scouring process used in S4 is performed directly after the gold plating is completed, retaining the dry gold plating film without peeling it off. The laser beam only acts on the solder resist ink layer, and the layer removal is achieved through energy control. This allows the etching process in S5 to directly reuse the dry gold plating film as the anti-corrosion layer, avoiding the secondary lamination process.

7. The method for preparing long and short gold fingers based on laser hollowing technology according to claim 1, characterized in that, The nickel-gold electroplating process in S3 includes first electroplating a nickel layer and then electroplating a gold layer. The nickel layer acts as a barrier layer to prevent the diffusion of copper, and the gold layer acts as a surface conductive layer and an anti-oxidation layer. The simultaneous electroplating of long and short gold fingers is achieved through the current path provided by the auxiliary conductive wire.

8. The method for preparing long and short gold fingers based on laser hollowing technology according to claim 1, characterized in that, The alkaline etching in S5 uses an amino etching solution or other alkaline etching system. The auxiliary conductive lines are removed by selectively dissolving the exposed copper surface through the etching solution. During the etching process, the electroplated gold dry film and the gold plating layer provide etching protection for the covered area. After the etching is completed, a blank area flush with the solder resist layer is formed at the position of the auxiliary conductive lines.

9. The method for preparing long and short gold fingers based on laser hollowing technology according to claim 1, characterized in that, The method replaces the traditional selective wet film printing process with laser hollowing technology, eliminating the processes of wet film printing, exposure, development, and peeling. At the same time, by reusing electroplated gold dry film as the resist layer for secondary etching, the repetitive processes such as secondary solder resist, secondary dry film lamination, exposure, and development in the in-board wire drawing process are avoided.

10. The method for preparing long and short gold fingers based on laser hollowing technology according to claim 1, characterized in that, Selective removal of different protective layers can be achieved by laser-removing resin or ink. The design of auxiliary conductive lines is not limited by the original circuit network layout on the board. No secondary solder resist and ink repair treatment is required after removing the auxiliary conductive lines.

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