CN117979563A - A high-precision circuit processing method - Google Patents

Abstract

The application discloses a processing method of a high-precision circuit, which comprises the following steps: copper deposition electroplating is carried out on the core plate; depositing a metal film on the copper layer; forming a metal pattern by laser etching the metal film, wherein the shape of the metal pattern is matched with the shape of the circuit pattern; etching the copper layer outside the metal pattern to form a circuit pattern covered by the metal pattern; and removing the metal film. According to the processing method of the high-precision circuit, provided by the application, the metal film is adopted to replace a mask layer of a dry film or a wet film in the prior art, so that dust interference in an exposure environment is avoided, and the circuit etching precision is improved.

Description

A high-precision circuit processing method

Technical Field

The present invention relates to the field of circuit molding in a PCB board or a carrier board, and in particular to a processing method for a high-precision circuit.

Background technique

In the prior art, a method for forming a circuit pattern in a PCB core board is to first form a global electroplated copper layer, then attach a dry film or a wet film to the copper layer, and then sequentially expose and develop to form a mask layer of the circuit pattern; after etching away the exposed copper layer, the dry film is removed, and the portion covered by the dry film is etched away to form a circuit pattern.

The photosensitive dry film or wet film used in the existing circuit pattern forming process needs to be formed by a specific coating and laminating equipment. The cost of the coating and laminating equipment also needs to be calculated in the circuit pattern forming process, resulting in increased costs. Limited by the operating accuracy of the coating and laminating settings, the thickness of the applied dry film or wet film is above 15um. When the circuit pattern is a small-pitch and small-size pattern, there are blind grooves between the dry films, and the etching liquid is not easy to enter, which affects the etching speed and effect, and manifests as a large amount of side etching and a small etching factor, which affects the accuracy of the circuit pattern. During the etching process, the etching liquid not only etches downward but also in all directions to the left and right, so side etching is inevitable. The ratio of etching depth to side etching width is called the etching factor.

The existing circuit pattern forming process uses an exposure process, which has a great impact on the environment. Dust in the environment will block the light path, directly leading to poor photocuring of the photosensitive material, resulting in circuit gaps or open circuit defects. In order to avoid environmental impact, a clean room is required for exposure operations, and a clean room cannot eliminate the presence of impurities such as dust in the air, which not only increases costs, but also cannot completely eliminate the impact of the environment on the exposure of the photosensitive film. The existing circuit pattern forming process requires the use of organic liquid to remove the dry film, and the organic liquid after the dry film is removed cannot be recycled, which increases the discharge of organic liquid and the difficulty of treatment.

Patent CN202111002461.9 discloses coating an organic masking material on the surface of a workpiece covered with copper foil, and after drilling and copper deposition, removing the polymer film layer in the non-circuit area by laser, exposing the copper surface in the non-circuit area, and then preparing a conductive pattern by chemical etching. In this technical solution, the hardness of the organic masking material is relatively small and the wear resistance is relatively poor. During the subsequent drilling and copper deposition and deposition of the metal protective layer, the mask material is easily worn and damaged, and it is impossible to ensure that the masking material layer remains intact when preparing the conductive pattern. At the same time, when the organic masking layer is removed by laser, due to the poor thermal conductivity of the organic masking layer, the laser energy cannot be conducted in time, and the heat generated by the laser cannot be dissipated in time, which may cause the organic masking layer or the underlying copper foil to deform at high temperature, resulting in accuracy deviation of the circuit pattern.

Summary of the invention

The present invention aims to solve at least one of the problems in the related art to a certain extent. To this end, the purpose of the present invention is to provide a method for processing a high-precision circuit, using a metal film as a masking layer, the metal film is an alloy layer, has good thermal conductivity, can dissipate the heat generated by the laser in time, avoid deformation of the metal film and the copper layer at high temperature, and at the same time, the metal film has greater hardness and oxidation resistance, and can be used as a protective layer for the copper layer, thereby improving the accuracy and efficiency of circuit pattern preparation.

In order to achieve the above purpose, this application adopts the following technical solutions:

A high-precision circuit processing method, comprising:

Copper electroplating on the core board;

Depositing a metal film on the copper layer; the metal film comprises the following components in weight ratio: 99 parts of tin, 0.02-0.05 parts of gold, and 0.7-0.9 parts of copper;

Laser etching the metal film to form a metal pattern, the shape of the metal pattern being matched to the shape of the circuit pattern;

Etching the copper layer outside the metal pattern to form a circuit pattern covered by the metal pattern;

Remove the metal film.

The present application uses a metal film to replace the dry film or wet film in the traditional process, and patterns the metal film by a laser etching method. During the laser etching of the metal film, the dust in the environment is directly penetrated by the laser to avoid defects such as openings or gaps. The density of the metal film in the present application is relatively high, and the porosity is less than 0.1%. The metal film in the present application has good thermal conductivity, which is about 210W/(m·k), and has good thermal conductivity. In the subsequent laser etching of the metal film, the good thermal conductivity can enable the heat energy in the laser processing process to be quickly transferred to other parts through the metal film itself, and at the same time dissipated into the air by convection, thereby effectively preventing abnormalities such as material deformation caused by heat accumulation.

Furthermore, the thickness of the metal film is less than or equal to 1 micron.

The thickness of the metal film is thinner than that of the dry film or the wet film. When etching the exposed copper layer, the etching solution can easily enter the copper layer, making the etching process have a higher etching factor and a smaller side etching amount, thereby obtaining a circuit pattern with better precision; it is especially suitable for small-size circuit patterns.

Furthermore, depositing a metal film on the copper layer includes: coating a film-forming liquid on the copper layer to form a metal film by chemical deposition; the film-forming liquid includes a gold ion complexing agent, a tin ion complexing agent, a tin antioxidant, a copper ion complexing agent, a divalent tin compound, a gold compound, a copper compound and an additive.

Furthermore, the additives include a gold stabilizer, a masking agent, a brightener, a grain refiner and a pH buffer.

Furthermore, the film-forming temperature of the chemical deposition method is 60-70° C. During the film-forming process, the core board where the copper layer is located is immersed in a film-forming liquid, and an inert gas is filled into the film-forming liquid.

The heating temperature in the film-forming process of the chemical deposition method is generally selected between 50C-80°C. The preferred heating temperature is 60C-70°C. The temperature value during the solvent volatilization process will affect the composition of the metal film finally formed. Too high a temperature will increase the thermal stress of the metal film, which may affect the etching effect during the subsequent etching of the copper layer. Too low a temperature will limit the growth rate of the metal film in disguise. The present application can fill the film-forming liquid with an inert gas and stir the film-forming liquid to increase the formation speed of the metal film, increase the bonding force between the metal film and the copper layer, and reduce the porosity of the metal film. When the copper-containing core board is immersed in the film-forming liquid, an inert gas can be filled into the film-forming liquid and the film-forming liquid can be stirred.

Furthermore, the hardness of the metal film is greater than or equal to 92HRA.

The surface hardness of the metal film of the present application is relatively high, and it has the characteristics of wear resistance, oxidation resistance, etc. The high hardness of the metal film can prevent scratches and abrasions on the metal film during transportation.

Furthermore, when the metal film is laser-etched to form a metal pattern, the laser over-etches the metal film.

In the present application, the metal film is located above the copper layer. During the laser etching process, the processing depth can be monitored in real time by the difference in laser reflection time. In the present application, the thickness of the metal film is about 1 micron. During the laser etching process, it is necessary to ensure that the etching depth is greater than or equal to the thickness of the metal film. For example, when the thickness of the metal film is 1 micron, when the laser etching depth is 2 microns monitored by the difference in laser reflection time, the laser spot moves toward the next position. This causes over-etching in the laser etching process. Since the exposed copper layer needs to be etched away later, the over-etching here does not affect the subsequent etching of the copper layer, and since the laser etching speed is much greater than the etching speed of the etching solution, the present application can also accelerate the etching of the copper layer. At the same time, over-etching can also ensure that the metal film is completely removed to avoid affecting the subsequent copper layer etching process. The speed of laser etching is fast. By removing the metal film through over-etching, it can not only ensure that the metal film above the circuit pattern is completely removed, but also speed up the etching speed of the circuit pattern.

Furthermore, the wavelength band of the laser is 230-260nm.

The laser in this application uses a circular or matrix spot, and the spot size is in the range of 10-50um, which can be specifically designed through regional formulation. Tin has excellent absorption of 220-286nm violet waves, so the laser band uses a beam of 230-260nm to etch metal films. This application uses nanosecond laser (10ns per shot) to etch metal films, and the laser spot overlap rate during the etching process is 1/2.

Furthermore, a stripping solution is used to remove the metal film; the stripping solution comprises the following components in parts by weight: 1-9 parts of boric acid, 45-55 parts of hydrofluoric acid, 8-12 parts of nitric acid; and 30-35 parts of deionized water.

At room temperature, soak the core board after etching to form the circuit pattern in the stripping liquid for a period of time, take it out and wipe it to remove the metal film. Or directly apply the stripping liquid on the surface of the metal film and soak it for a period of time, then wipe it to remove the metal film. The removal method does not produce organic waste liquid, avoiding the subsequent waste liquid treatment process.

The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art: the method for preparing the circuit pattern of the present application comprises: copper electroplating on the core board; depositing a metal film on the copper layer, the metal film comprising the following components in weight ratio: 99 parts of tin, 0.02-0.05 parts of gold, and 0.7-0.9 parts of copper; laser etching the metal film to form a metal pattern, the shape of the metal pattern being adapted to the shape of the circuit pattern; etching the copper layer outside the metal pattern to form a circuit pattern covered by the metal pattern; removing the metal film. As an alloy, the metal film of the present application has a large surface hardness and good oxidation resistance, and can be used as a protective layer during the transportation of the core board, providing a protective shielding effect for the copper layer, ensuring that during the transportation and movement of the core board, even if it undergoes multiple processes in the middle, the copper layer and the metal film still have good conformality, ensuring the accuracy of subsequent circuit pattern preparation.

At the same time, the metal film of the present application has good thermal conductivity. When the metal film is subsequently laser-etched, the good thermal conductivity can enable the heat energy in the laser processing process to be quickly transferred to other parts through the metal film itself, and dissipated into the air by convection, thereby effectively preventing abnormalities such as material deformation caused by heat accumulation, avoiding deformation of the masking layer or copper layer caused by laser processing in the prior art, and ensuring the accuracy of the size and shape of the metal graphics and circuit graphics.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

In the attached figure:

FIG1 is a flow chart of the preparation of small-sized circuits in Example 2.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the directions or positional relationships indicated by "front", "back", "up", "down", "left", "right", "longitudinal", "horizontal", "vertical", "horizontal", "top", "bottom", "inside", "outside", "head", "tail", etc. are based on the directions or positional relationships shown in the accompanying drawings, are constructed and operated in a specific direction, and are only for the convenience of describing the present technical solution, rather than indicating that the mechanism or element referred to must have a specific direction, and therefore cannot be understood as a limitation to the present invention.

It should also be noted that, unless otherwise clearly specified and limited, the terms such as "installed", "connected", "connected", "fixed", "set" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. When an element is referred to as being "on" or "under" another element, the element can be "directly" or "indirectly" located on the other element, or there may be one or more intermediate elements. The terms "first", "second", "third", etc. are only for the convenience of describing the present technical solution, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", "third", etc. can explicitly or implicitly include one or more of the features. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, mechanisms, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

Example 1

A high-precision circuit processing method, comprising:

Copper electroplating on the core board;

depositing a metal film on the copper layer;

Laser etching the metal film to form a metal pattern, the shape of the metal pattern being matched to the shape of the circuit pattern;

Etching the copper layer outside the metal pattern to form a circuit pattern covered by the metal pattern;

Remove the metal film.

The metal film of the present application includes the following components in weight ratio: 99 parts of tin, 0.02-0.05 parts of gold, and 0.7-0.9 parts of copper; laser etching the metal film to form a metal pattern, the shape of the metal pattern is adapted to the shape of the circuit pattern; etching the copper layer outside the metal pattern to form a circuit pattern covered by the metal pattern; removing the metal film. As an alloy, the metal film of the present application has a large surface hardness and good oxidation resistance. It can be used as a protective layer during the transportation of the core board, providing a protective shielding effect for the copper layer, ensuring that during the transportation and movement of the core board, even if it undergoes multiple processes in the middle, the copper layer and the metal film still have good conformality, ensuring the accuracy of subsequent circuit pattern preparation.

At the same time, the metal film of the present application has good thermal conductivity. When the metal film is subsequently laser-etched, the good thermal conductivity can enable the heat energy in the laser processing process to be quickly transferred to other parts through the metal film itself, and dissipated into the air by convection, thereby effectively preventing abnormalities such as material deformation caused by heat accumulation, avoiding deformation of the masking layer or copper layer caused by laser processing in the prior art, and ensuring the accuracy of the size and shape of the metal graphics and circuit graphics.

Example 2

As shown in FIG1 , the present application provides a high-precision circuit processing method, comprising:

S1: Copper electroplating on the core board.

The core board here refers to the surface of the core board where a circuit pattern needs to be formed; specifically, the copper layer can be formed by electroplating copper.

Specifically, when copper is deposited, the initial copper layer is first deposited horizontally. The initial copper layer can be formed by chemical deposition and other methods, and the purpose is to have a good bonding force with the surface of the core board; then the initial copper layer is electroplated to form a complete copper layer, and the electroplated copper layer at this time can better bond with the initial copper layer. The two-step copper deposition method can ensure that the copper layer has a good bonding force with the surface of the core board and ensure the firmness of the copper layer; it can also increase the deposition rate of the copper layer and improve the efficiency of circuit pattern preparation.

The thickness of the copper layer formed in the present application can be limited according to the application scenario and design requirements of the circuit pattern. After the portion of the copper layer that does not need to form the circuit pattern is etched, the remaining copper layer portion forms the circuit pattern.

S2: depositing a metal film on the copper layer. The metal film comprises the following components in weight ratio: 99 parts of tin, 0.02-0.05 parts of gold, and 0.7-0.9 parts of copper. The material of the metal film is a gold-tin alloy containing copper. As a special alloy layer, the metal film has the characteristics of strong acid and weak alkali resistance.

It should be noted that the metal film in this application is formed by chemical deposition, electroplating, etc., and the alloy layer finally formed is not a mixture, but an alloy element with a changed lattice stacking form. The metal film in this application is relatively thin, which can improve the deposition efficiency of the metal film and also improve the subsequent laser removal efficiency and accuracy.

Compared with non-metallic masking films, the metal film in this application can be used as a masking layer for circuit patterns and as a protective layer for the core board during transportation. Compared with the carbon chain connection structure in the polymer masking film, the metal film in this application is formed by metal lattice stacking and has greater hardness and wear resistance.

In the present application, the metal film is an alloy containing copper and gold with poor chemical activity. The gold and copper are filled in the tin lattice, which can greatly improve the oxidation resistance of the metal film, so that the metal film can protect the copper layer and the core board during the core board transportation process.

The thickness of the metal film in the present application is less than or equal to 1 micron, and it only needs to protect the remaining copper layer during the etching process of the copper layer. And the thickness of the metal film deposited in the present application is relatively small. Under this thickness condition, after the metal film is removed by laser, due to its small thickness, the etching solution can easily enter the copper layer for etching, so that the etching process of the copper layer has a higher etching factor and a smaller amount of side etching, thereby obtaining a circuit pattern with better precision. At the same time, the thickness of the metal film is relatively small, which will make the metal film more uniform. In a thinner metal film, the extreme difference in thickness at various locations is smaller, so that the uniformity tolerance is smaller. In the subsequent laser processing to remove the metal film, the laser parameters with fixed parameters can be used to uniformly remove the metal film at one time, avoiding the defect of different laser etching effects at different positions due to the large uniformity tolerance of the metal film, and also avoiding the need to frequently change the laser parameters for metal films with different uniformity, or even the defect of rework after one laser etching.

The metal film in the present application has a high density, a porosity of <0.1%, a surface hardness of greater than or equal to 92HRA, and has the characteristics of wear resistance and oxidation resistance. The high hardness of the metal film can prevent scratches and abrasions on the metal film during transportation.

In this application, the metal film is an alloy containing copper and gold with high thermal conductivity. Gold and copper are filled in the tin lattice, which can greatly improve the thermal conductivity of the metal film. Therefore, the metal film in this application has good thermal conductivity, which is about 210W/(m·k), and has good thermal conductivity. In the subsequent laser etching of the metal film, the good thermal conductivity can make the heat energy in the laser processing process quickly transferred to other parts through the metal film itself, and dissipated into the air by convection, thereby effectively preventing abnormalities such as material deformation caused by heat accumulation.

The metal film in the present application includes the following components in weight ratio: 99 parts of tin, 0.02-0.05 parts of gold, 0.7-0.9 parts of copper, and 0.1 parts of other impurities, where other impurities refer to other conductive metals or semiconductor doping impurities, etc.

The metal film deposition method in this application can be formed by chemical deposition, electroplating, etc. Chemical deposition specifically refers to CBD (chemical bath deposition), which is a technology that deposits a film on the surface of a substrate material using chemical reactions or electrochemical principles.

As a specific embodiment, the chemical deposition method for forming a metal film specifically includes: immersing the core board after the copper layer is deposited in a film-forming liquid, and heating the container containing the film-forming liquid in a water bath so that the film-forming liquid grows and precipitates on the surface of the copper layer to form a metal film.

Specifically, the heating temperature during the film formation process of the chemical deposition method is generally selected between 50°C and 80°C. The preferred heating temperature is 60°C-70°C. The temperature value during the solvent volatilization process will affect the composition of the metal film finally formed. Too high a temperature will increase the thermal stress of the metal film, which may affect the etching effect in the subsequent etching of the copper layer. Too low a temperature will in turn limit the growth rate of the metal film.

The present application can fill the film-forming liquid with inert gas and stir the film-forming liquid to increase the formation speed of the metal film, increase the bonding force between the metal film and the copper layer, reduce the porosity of the metal film, etc. When the copper-containing core board is immersed in the film-forming liquid, the film-forming liquid can be filled with inert gas and stirred.

The film-forming liquid in the present application includes a gold ion complexing agent, a tin ion complexing agent, a tin antioxidant, a copper ion complexing agent, a divalent tin compound, a gold compound, a copper compound and an additive. Based on the components of the film-forming liquid, a chemical deposition temperature of 50°C-80°C is selected, and an inert gas is filled into the film-forming liquid during the chemical deposition process, and the film-forming liquid is stirred. Under the action of the above-mentioned film-forming liquid components and film-forming conditions, the bonding force between the metal film and the copper layer can be improved and the porosity of the metal film can be reduced; finally, a metal film with a high density, a porosity of less than 0.1%, a surface hardness greater than or equal to 92HRA, and wear resistance, oxidation resistance and other characteristics is formed.

As another specific embodiment, a metal film can also be formed on the copper layer by electroplating a film-forming liquid. Specifically, the core board on which the copper layer is deposited is used as a cathode, so that the metal ions in the film-forming liquid are electroplated on the outside of the copper layer. During the electroplating process, the copper layer can be clamped at various positions by multiple conductive clamps, so that the potential at each position is equal, and the metal film is uniformly electroplated at various positions on the surface of the copper layer to form a metal film layer with uniform thickness.

The film-forming liquid in the present application comprises a gold ion complexing agent, a tin ion complexing agent, a tin antioxidant, a copper ion complexing agent, a divalent tin-containing compound, a gold-containing compound, a copper-containing compound and an additive.

Gold ion complexing agent: Sulfurous acid, thiosulfate, pyrophosphoric acid, citric acid and their potassium, sodium, ammonia and alkaline earth metal salts can be selected as gold ion complexing agents. Gold ion complexing agents can not only improve the stability of the film-forming solution, but also buffer the pH value, increase the brightness of the metal film layer, and improve the adhesion between the metal and the copper layer.

Tin ion complexing agent: The amphoteric acid or base of elemental tin can react with tin to form a complexing reaction. Specifically, oxalic acid, citric acid, ascorbic acid, glucose, malonic acid, and iminodiacetic acid can be selected as complexing agents for divalent tin ions. In an acidic solution, divalent tin reacts with water to form a hydration reaction, while tetravalent tin is unstable. Under alkaline conditions, tetravalent tin is stable, while divalent tin is prone to undergo a disproportionation reaction. Tin complexes are relatively stable in neutral solutions. Therefore, the present application can adjust the pH value of the film-forming solution to about 7.

Tin antioxidant: Since divalent tin is oxidized to tetravalent tin in the solution, which causes the problem that tin cannot be deposited, an antioxidant or a reducing agent needs to be added to the solution to improve the stability of divalent tin. The tin antioxidant selected in this application is a hydroxybenzene compound.

Copper ion complexing agent: Sulfuric acid can be selected as a copper ion complexing agent to form copper sulfate for stable existence.

Additives: Other additives should be appropriately added to the film-forming solution to ensure the electroplating performance of the plating solution and the quality of the coating, including alloy stabilizers, masking agents, brighteners, grain refiners, pH buffers, conductive salts and nitrogen-doped graphene oxide.

The film-forming liquid of the present application contains nitrogen-doped graphene oxide. Nitrogen-doped graphene oxide serves as a catalyst, which can make the potentials of tin, gold, and copper ions in the film-forming liquid similar. Combined with the content of each metal ion in the film-forming liquid, it is ensured that each metal ion is uniformly deposited in a certain proportion, ensuring that the metal film is in the form of an alloy with a consistent lattice, thereby ensuring that the metal film has specific thermal conductivity, uniformity, hardness, and oxidation resistance.

The components of the film-forming liquid of the present application can ensure that the potential difference of tin ions, copper ions and gold ions is small during the film-forming process, and the three metal ions can be evenly deposited on the surface of the copper layer in a certain proportion, finally forming a metal film layer with thin thickness, good thermal conductivity, good uniformity, high hardness and good oxidation resistance in the present application.

S3: Laser etching the metal film to form a metal groove, the shape of which matches the shape of the circuit pattern, and the metal groove exposes the copper layer. The shape of the circuit pattern and the size of the copper layer can be input into the controller of the laser etching machine, and the controller automatically calculates the moving path of the laser beam during the laser etching process; the core board with the copper layer and the metal film deposited is fixed in the laser etching machine, and the laser beam etches the metal film along the preset moving path, so that the copper layer without forming a circuit pattern is exposed.

The laser parameters used in this application are as follows: the laser uses a circular or matrix spot, and the spot size is in the range of 10-50um, which can be specifically designed through regional formulation. Tin has excellent absorption of 220-286nm violet waves, so the laser band uses a beam of 230-260nm to etch the metal film.

The present application uses nanosecond laser (10ns per shot) to etch the metal film, and the laser spot overlap rate is 1/2 during the etching process.

In this application, the thickness of the metal film is about 1 micron, and the nanosecond laser can complete the etching of the metal film in one time, avoiding multiple laser etchings that cause the laser energy to diffuse to the surroundings multiple times. The one-time laser etching method can ensure the uniformity of the exposed copper layer, which helps to form a circuit pattern with better uniformity and precision.

In the present application, the metal film is located above the copper layer. During the laser etching process, the processing depth can be monitored in real time by means of the difference in laser reflection time. The thickness of the metal film in the present application is about 1 micron, and it is necessary to ensure that the etching depth is greater than or equal to the thickness of the metal film during the laser etching process. For example, when the thickness of the metal film is 1 micron, when the laser etching depth is monitored to be 2 microns (or any other value less than or equal to the thickness of the metal film and the copper layer) by means of the difference in laser reflection time, the laser spot moves toward the next position. This causes over-etching during the laser etching process.

Since the exposed copper layer needs to be etched away later, the over-etching here will not affect the subsequent etching of the copper layer, and since the laser etching speed is much greater than the etching speed of the etching solution, the present application can also accelerate the etching of the copper layer. At the same time, over-etching can also ensure that the metal film is completely removed to avoid affecting the subsequent copper layer etching process. The speed of laser etching is relatively fast, and removing the metal film by over-etching can not only ensure that the metal film above the circuit pattern is completely removed, but also speed up the etching speed of the circuit pattern.

S4: etching the copper layer outside the metal pattern to form a circuit pattern covered by the metal pattern. Specifically, an etching solution for the copper layer may be used to etch the exposed copper layer.

The metal film in the present application has properties such as acid resistance, and its density is better than that of a dry film. It can avoid the penetration and etching effect of the etching solution on the metal film to the greatest extent, ensuring that a thinner metal film can also achieve a good masking effect.

Chemical etching is used to ensure uniformity during etching. The etching line speed is designed according to the thickness of the copper layer. When the copper layer thickness is 10um, the etching line speed can be set to 6m/min.

In the present application, the circuit pattern can be formed on one side of the core board, or the copper layer can form the circuit pattern on both sides of the core board. When the circuit pattern needs to be formed on both sides of the core board, the copper layer and the metal film can be deposited on both sides of the core board at the same time, and the copper layer outside the circuit pattern can be removed by laser respectively. Then, the copper layer outside the circuit pattern is removed by chemical etching to form the circuit pattern on both sides of the core board.

In order to ensure that the redundant copper layers on both sides of the core board are etched at the same time, the placement direction of the core board in the etching machine used in this application is perpendicular to the transmission line of the transmission core board. When the transmission line is a horizontal transmission line, nozzles are respectively arranged on both sides of the horizontal transmission line, and the core board is placed vertically on the horizontal transmission line. That is, the upper surface and the lower surface of the core board where the circuit pattern needs to be formed are placed vertically, facing the nozzles on both sides of the horizontal transmission line, and the nozzles on both sides are used to spray etching liquid to both sides of the core board.

Specifically, the present application can set the nozzles located on the same vertical line to gradually increase the spray flow rate from top to bottom, and the excess etching liquid sprayed above the core board will fall under the action of weight, thus ensuring the uniformity of copper layer etching at various positions.

S5: removing the metal film.

The present application uses a stripping liquid to remove the metal film. The stripping liquid refers to a solution that can react with the metal film to generate soluble salts. The stripping liquid will not dissolve the copper layer and will not affect the size and accuracy of the circuit pattern.

As a specific embodiment, the main component of the stripping solution of the present application is a solution containing chloride and an oxidant. When the stripping water comes into contact with metallic tin, the chloride ions react with the metallic tin to generate soluble stannous chloride and release electrons.

As another specific embodiment, the film stripping solution of the present application includes the following components in parts by weight: 1-9 parts of boric acid, 45-55 parts of hydrofluoric acid, 8-12 parts of nitric acid; and 30-35 parts of deionized water.

At room temperature, soak the core board after etching to form the circuit pattern in the film stripping liquid for a period of time, take it out and wipe it to remove the metal film. Or directly apply the film stripping liquid on the surface of the metal film and soak it for a period of time, then wipe it to remove the metal film.

The present application uses a metal film to replace the dry film or wet film in the traditional process, and patterns the metal film through a laser etching method. During the laser etching of the metal film, dust in the environment is directly penetrated by the laser, avoiding defects such as openings or gaps.

The thickness of the metal film of the present application is thinner than that of a dry film or a wet film. When etching the exposed copper layer, the etching solution can easily enter the copper layer, so that the etching process has a higher etching factor and a smaller side etching amount, thereby obtaining a circuit pattern with better precision; it is especially suitable for small-size circuit patterns.

In the present application, the metal film is formed by electroplating or chemical deposition, which does not require the coating and laminating equipment in the traditional process, and does not require the use of a clean room for exposure, thereby simplifying the steps of the circuit pattern formation process, reducing equipment costs, and increasing the speed of circuit pattern formation.

In the present application, the metal film can be removed by wiping with a film stripping solution at room temperature. The removal method does not generate organic waste liquid, thus avoiding subsequent waste liquid treatment processes.

It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the scope covered by the claims of the present invention.

Claims (9)

1. The processing method of the high-precision circuit is characterized by comprising the following steps of:

Copper deposition electroplating is carried out on the core plate;

depositing a metal film on the copper layer; the metal film comprises the following components in parts by weight: 99 parts of tin, 0.02-0.05 part of gold and 0.7-0.9 part of copper;

Forming a metal pattern by laser etching the metal film, wherein the shape of the metal pattern is matched with the shape of the circuit pattern;

etching the copper layer outside the metal pattern to form a circuit pattern covered by the metal pattern;

And removing the metal film.

2. The method of claim 1, wherein the metal film has a thickness of 1 μm or less.

3. The method of claim 1, wherein depositing a metal film on the copper layer comprises: coating film forming liquid on the copper layer, and forming a metal film by a chemical deposition method; the film forming liquid comprises a gold ion complexing agent, a tin antioxidant, a copper ion complexing agent, a divalent tin-containing compound, a gold-containing compound, a copper-containing compound and an additive.

4. A method of processing high precision wire according to claim 3, wherein the additives include gold stabilizers, masking agents, brightening agents, grain refiners and pH buffers.

5. A method of manufacturing a high precision circuit according to claim 3, wherein the film formation temperature of the chemical deposition process is 60-70 ℃; in the film forming process, the core plate where the copper layer is positioned is soaked in film forming liquid, and inert gas is filled into the film forming liquid.

6. The method of claim 1, wherein the metal film has a hardness of 92HRA or more.

7. The method of claim 1, wherein the laser overetching the metal film is performed while the laser etching the metal film to form the metal pattern.

8. The method for processing high-precision lines according to claim 1, wherein the wavelength band of the laser is 230-260nm.

9. The method for processing a high-precision circuit according to claim 1, wherein the metal film is removed by using a film removing liquid; the film removing liquid comprises the following components in parts by weight: 1-9 parts of boric acid, 45-55 parts of hydrofluoric acid and 8-12 parts of nitric acid; 30-35 parts of deionized water.