Electrolytic etching process for circuit board

Abstract

An electrolytic etching process for a circuit board includes the following steps: S1, coating a layer of dielectric material on at least one side of a carrier material, and drying and curing to form a dielectric layer to obtain a composite board; S2, copper deposition on the surface of the dielectric layer of the composite board and then electroplating a layer of copper alloy to obtain a circuit substrate; S3, pasting a dry film on the copper alloy surface of the circuit substrate, exposing and developing to obtain a film-coated board; S4, placing the film-coated board in an electrolytic cell anode for electrolysis to obtain a preliminary engraving board; S5, immersing the preliminary engraving board in an etching solution to form a fine engraving board; S6, removing the dry film to obtain a circuit board. The present invention provides an electrolytic etching process for a circuit board. The present invention uses electroplated copper alloy as the circuit layer of the circuit board, which improves the etching difficulty of the circuit layer to a certain extent, reduces the corrosion of the side edges of the circuit lines on the circuit board, and improves the etching accuracy of the circuit board.

Description

Technical Field

[0001] The invention relates to the technical field of circuit board manufacturing, and in particular to an electrolytic etching process for a circuit board. Background Art

[0002] Circuit board is an indispensable part of an electronic product or electrical equipment. With the development of electronic and electrical technology, people's requirements for circuit boards are getting higher and higher. Especially as LED as a lighting device has entered people's lives, the requirements for the heat dissipation performance of circuit boards are getting higher and higher. At present, some circuit boards that require high heat dissipation performance are all made of aluminum-based circuit boards, which are provided with a layer of thermal conductive glue on the aluminum plate, which can play a role of heat conduction on the one hand, and also has an insulating function on the other hand. A layer of copper film circuit board circuit is attached to the thermal conductive glue, but the thermal conductivity of the thermal conductive glue is not very good, which will affect the thermal conductivity of the entire circuit board. As the circuit board is being etched, the etching liquid will corrode the circuit layer in all directions of the conductive line, and will continue to corrode the side of the circuit, seriously reducing the accuracy of circuit board etching.

[0003] For example, the Chinese invention patent application document with patent application number CN201610790296.0 discloses a method for etching a thick copper circuit board, including the following steps: providing an etching production line, a thick copper circuit board, a flipping device and a return device, the etching production line including a film stripping station, an etching station and a tin stripping station; the thick copper circuit board is arranged with one side facing upward and the other side facing downward and is horizontally conveyed along the etching production line; the flipping device is arranged on the etching production line, and the return device is used to reversely convey the thick copper circuit board along the etching production line; the thick copper circuit board is film stripped, and the surface of the thick copper circuit board is stripped with a film stripping liquid. The dry film is removed to expose the copper surface that has not been processed by the circuit; for the first etching, the thick copper circuit board is transferred to the etching station to complete the simultaneous etching of the upper and lower surfaces; flipping and returning, after the thick copper circuit board is transferred to the exit of the etching station, the flipping device flips the thick copper circuit board 180°, and the return device returns the thick copper circuit board to the entrance of the etching station; for the second etching, the flipped thick copper circuit board passes through the etching station again to complete the simultaneous etching of the upper and lower surfaces; the thick copper circuit board is tinned, and after the thick copper circuit board is transferred to the exit of the etching station, it enters the tinning station for the tinning process. The above technical problems exist in the preparation process of this circuit board, and the circuit lines that need to be retained on the circuit board will be corroded by the etching liquid on the sides, reducing the accuracy of circuit board etching. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides an electrolytic etching process for a circuit board. The present invention uses electroplated copper alloy as the circuit layer of the circuit board, which improves the etching difficulty of the circuit layer to a certain extent, reduces the corrosion of the side edges of the circuit lines on the circuit board, and improves the etching accuracy of the circuit board.

[0005] The specific contents of the present invention are as follows:

[0006] An electrolytic etching process for a circuit board comprises the following steps:

[0007] S1, coating a layer of dielectric material on at least one side of the carrier material, and drying and curing to form a dielectric layer to obtain a composite board;

[0008] S2, depositing copper on the surface of the dielectric layer of the composite board and then electroplating a layer of copper alloy to obtain a circuit substrate;

[0009] S3, sticking a dry film on the copper alloy surface of the circuit substrate, exposing and developing to obtain a laminated board;

[0010] S4, placing the film-coated board in an electrolytic cell for anode electrolysis to obtain a primary engraved board;

[0011] S5, soaking the primary engraved plate in an etching solution to form a fine engraved plate;

[0012] S6. Remove the dry film to obtain the circuit board.

[0013] In the prior art, a circuit board is obtained by laminating a copper foil on the surface of a carrier plate, exposing, developing, etching, and then removing the anti-corrosion film. During the preparation process of the circuit board, side etching of the conductive circuit is inevitable. The side etching usually causes the circuit with a rectangular cross section to be corroded into a conductive circuit with a trapezoidal cross section. It is also possible that a groove is etched on the side of the conductive circuit, and a side etching protrusion is formed on the upper side of the groove. In subsequent use, the side etching protrusion may break and overlap due to various reasons, resulting in errors such as short circuits.

[0014] In the above technical scheme of the present invention, a copper alloy is electroplated on the surface of the dielectric layer as a conductive layer, and then a finished circuit board is obtained through film lamination, exposure, development, etching and other steps; in the conductive layer of the circuit board, a certain amount of other metal elements are contained, which are more difficult to be etched, so firstly, an anodic etching is performed in an electrolytic cell to remove most of the unnecessary copper alloy, and then part of the copper alloy and part of the deposited copper are removed by chemical etching, so that in the second process, the conductive circuit can be prevented from being subjected to excessive corrosion during the chemical etching process, especially the corrosion occurring on the side of the conductive circuit; because the copper alloy is more corrosion-resistant, it takes more time during chemical etching, and the longer the time, the more convenient it is to operate and control the etching state; the combination of electrochemical etching and chemical etching avoids the side etching caused by the excessively fast electrochemical etching speed, and also avoids the inefficiency caused by the excessively slow chemical etching speed.

[0015] As a preferred embodiment of the above technical solution of the present invention, in step S2, the copper alloy contains at least one non-copper metal, and the non-copper metal is selected from one or more of tin and zinc.

[0016] As a preferred embodiment of the above technical solution of the present invention, in step S2, the copper alloy contains at least one non-copper metal, and the non-copper metal is selected from one or more of tin and zinc.

[0017] As a preferred embodiment of the above technical solution of the present invention, in step S2, the electroplating solution in the electroplating process includes sodium cyanide, cuprous cyanide, sodium stannate and sodium hydroxide; wherein, cyanide ions and cuprous ions are coordinated, and hydroxide ions and tetravalent tin ions are coordinated, and the deposition potentials of the two are controlled to be close to each other, so as to facilitate the deposition of the alloy.

[0018] As a preferred embodiment of the above technical solution of the present invention, in step S2, the content of cuprous cyanide is 30-50 g / L, and the content of sodium stannate is 5-15 g / L.

[0019] As a preferred embodiment of the above technical solution of the present invention, in step S2, the pH of the electroplating solution is 11-12.

[0020] As a preferred embodiment of the above technical solution of the present invention, in step S2, during the electroplating process, the current density of the cathode is 9-11A / dm 2 .

[0021] As a preferred embodiment of the above technical solution of the present invention, in step S2, the electroplating time is 1.5~2.5h.

[0022] As a preferred embodiment of the above technical solution of the present invention, in step S2, after electroplating for 1 hour, sodium stannate is added to the electroplating solution to make its content reach 20~30g / l; in this technical solution, during the electroplating process, the tin content in the electroplated alloy coating is controlled by adding an appropriate amount of sodium stannate to the electroplating solution, so that different parts of the electroplated alloy layer have certain differences, specifically, the tin content in the inner layer alloy plated first is lower, and the surface layer alloy plated later contains more tin; when chemically corroded in step S5, the surface layer alloy has better corrosion resistance, and the inner layer alloy is more easily corroded than the surface layer alloy, and the side of the circuit line etched out when the inner layer is corroded is not easily corroded, thereby improving the accuracy of etching of the surface circuit board.

[0023] As a preferred embodiment of the above technical solution of the present invention, in step S1, the carrier material is selected from one of polyimide film, glass fiber cloth or polyvinylidene fluoride film.

[0024] As a preferred embodiment of the above technical solution of the present invention, in step S1, the dielectric material comprises a polymer resin, a curing agent and a filler; the polymer resin is any one of epoxy resin, polyimide resin or phenolic resin or a mixture of at least two of them; the curing agent is any one of diamine, dianhydride or phenolic resin or a mixture of at least two of them; the filler is a ceramic filler; ceramic filler has good thermal conductivity and heat dissipation effects.

[0025] In summary, the beneficial effects of the present invention are as follows:

[0026] 1. The present invention electroplates a layer of copper alloy on the surface of the dielectric layer as a conductive layer, and then obtains a finished circuit board through film lamination, exposure, development, etching and other steps; the conductive layer of the circuit board is a copper alloy, which contains a certain amount of other metal elements and is more difficult to etch, so firstly an anodic etching is performed in an electrolytic cell to remove most of the unnecessary copper alloy, and then a part of the copper alloy and a part of the deposited copper are removed by chemical etching, so that the conductive circuit is prevented from being excessively corroded during the chemical etching process, especially the corrosion occurring on the side of the conductive circuit;

[0027] 2. The present invention combines electrochemical etching with chemical etching to avoid side etching caused by too fast electrochemical etching speed, and also avoids low efficiency caused by too slow chemical etching speed;

[0028] 3. In the present invention, during the electroplating process, an appropriate amount of sodium stannate is added to the electroplating solution to control the tin content in the electroplated alloy coating, so that different parts of the electroplated alloy layer have certain differences. Specifically, the tin content in the inner alloy plated first is lower, while the surface alloy plated later contains more tin. When chemically corroded in step S5, the surface alloy has better corrosion resistance. Compared with the surface alloy, the inner alloy is more easily corroded. When the inner layer is corroded, the side of the etched circuit line is not easily corroded, thereby improving the accuracy of etching the surface circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of side erosion. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0031] Example 1

[0032] An electrolytic etching process for a circuit board comprises the following steps:

[0033] S1. Coating a layer of dielectric material on one surface of the glass fiber cloth, and drying and curing to form a dielectric layer to obtain a composite board;

[0034] S2, depositing copper on the surface of the dielectric layer of the composite board and then electroplating a layer of copper-tin alloy to obtain a circuit substrate;

[0035] S3, sticking a dry film on the copper alloy surface of the circuit substrate, exposing and developing to obtain a laminated board;

[0036] S4, placing the film-coated board in an electrolytic cell for anode electrolysis to obtain a primary engraved board;

[0037] S5, soaking the primary engraved plate in an etching solution to form a fine engraved plate;

[0038] S6, removing the dry film to obtain the circuit board;

[0039] Wherein, the dielectric material comprises a polymer resin, a curing agent and a filler; the polymer resin is any one of epoxy resin, polyimide resin or phenolic resin or a mixture of at least two thereof; the curing agent is any one of diamine, dianhydride or phenolic resin or a mixture of at least two thereof; the filler is a high thermal conductivity ceramic filler.

[0040] In the above technical scheme of the present invention, a copper alloy is electroplated on the surface of the dielectric layer as a conductive layer, and then a finished circuit board is obtained through film lamination, exposure, development, etching and other steps; in the conductive layer of the circuit board, a certain amount of other metal elements are contained, which are more difficult to be etched, so firstly, an anodic etching is performed in an electrolytic cell to remove most of the unnecessary copper alloy, and then part of the copper alloy and part of the deposited copper are removed by chemical etching, so that in the second process, the conductive circuit can be prevented from being subjected to excessive corrosion during the chemical etching process, especially the corrosion occurring on the side of the conductive circuit; because the copper alloy is more corrosion-resistant, it takes more time during chemical etching, and the longer the time, the more convenient it is to operate and control the etching state; the combination of electrochemical etching and chemical etching avoids the side etching caused by the excessively fast electrochemical etching speed, and also avoids the inefficiency caused by the excessively slow chemical etching speed.

[0041] In step S2, the electroplating solution in the electroplating process includes sodium cyanide, cuprous cyanide, sodium stannate and sodium hydroxide.

[0042] In step S2, the content of cuprous cyanide is 50 g / L, and the content of sodium stannate is 15 g / L.

[0043] In step S2, the pH of the electroplating solution is 11.

[0044] In step S2, during the electroplating process, the current density of the cathode is 10.2~10.3A / dm2.

[0045] In step S2, the electroplating time is 2 hours.

[0046] In step S2, after electroplating for 1 hour, sodium stannate is added to the electroplating solution to make its content reach 30g / l; in the present technical scheme, during the electroplating process, the tin content in the electroplated alloy coating is controlled by adding an appropriate amount of sodium stannate to the electroplating solution, so that different parts of the electroplated alloy layer have certain differences, specifically, the tin content in the inner alloy plated first is lower, and the surface alloy plated later contains more tin; when chemically corroded in step S5, the surface alloy has better corrosion resistance, and the inner alloy is more easily corroded than the surface alloy, and the side of the circuit line etched out when the inner layer is corroded is not easily corroded, thereby improving the accuracy of etching of the surface circuit board.

[0047] Example 2

[0048] An electrolytic etching process for a circuit board comprises the following steps:

[0049] S1. Coating a layer of dielectric material on both sides of the glass fiber cloth, and drying and curing to form a dielectric layer to obtain a composite board;

[0050] S2, depositing copper on the surface of the dielectric layer of the composite board and then electroplating a layer of copper-tin alloy to obtain a circuit substrate;

[0051] S3, sticking a dry film on the copper alloy surface of the circuit substrate, exposing and developing to obtain a laminated board;

[0052] S4, placing the film-coated board in an electrolytic cell for anode electrolysis to obtain a primary engraved board;

[0053] S5, soaking the primary engraved plate in an etching solution to form a fine engraved plate;

[0054] S6, removing the dry film to obtain a double-layer circuit board;

[0055] Wherein, the dielectric material comprises a polymer resin, a curing agent and a filler; the polymer resin is any one of epoxy resin, polyimide resin or phenolic resin or a mixture of at least two thereof; the curing agent is any one of diamine, dianhydride or phenolic resin or a mixture of at least two thereof; the filler is a high thermal conductivity ceramic filler.

[0056] In the above technical scheme of the present invention, a copper alloy is electroplated on the surface of the dielectric layer as a conductive layer, and then a finished circuit board is obtained through film lamination, exposure, development, etching and other steps; in the conductive layer of the circuit board, a certain amount of other metal elements are contained, which are more difficult to be etched, so firstly, an anodic etching is performed in an electrolytic cell to remove most of the unnecessary copper alloy, and then part of the copper alloy and part of the deposited copper are removed by chemical etching, so that in the second process, the conductive circuit can be prevented from being subjected to excessive corrosion during the chemical etching process, especially the corrosion occurring on the side of the conductive circuit; because the copper alloy is more corrosion-resistant, it takes more time during chemical etching, and the longer the time, the more convenient it is to operate and control the etching state; the combination of electrochemical etching and chemical etching avoids the side etching caused by the excessively fast electrochemical etching speed, and also avoids the inefficiency caused by the excessively slow chemical etching speed.

[0057] In step S2, the electroplating solution in the electroplating process includes sodium cyanide, cuprous cyanide, sodium stannate and sodium hydroxide.

[0058] In step S2, the content of cuprous cyanide is 50 g / L, and the content of sodium stannate is 15 g / L.

[0059] In step S2, the pH of the electroplating solution is 11.

[0060] In step S2, during the electroplating process, the cathode current density is 10.2~10.3A / dm 2 .

[0061] In step S2, the electroplating time is 2 hours.

[0062] In step S2, after electroplating for 1 hour, sodium stannate is added to the electroplating solution to make its content reach 30g / l; in the present technical scheme, during the electroplating process, the tin content in the electroplated alloy coating is controlled by adding an appropriate amount of sodium stannate to the electroplating solution, so that different parts of the electroplated alloy layer have certain differences, specifically, the tin content in the inner alloy plated first is lower, and the surface alloy plated later contains more tin; when chemically corroded in step S5, the surface alloy has better corrosion resistance, and the inner alloy is more easily corroded than the surface alloy, and the side of the circuit line etched out when the inner layer is corroded is not easily corroded, thereby improving the accuracy of etching of the surface circuit board.

[0063] Comparative Example

[0064] An electrolytic etching process for a circuit board comprises the following steps:

[0065] S1. Coating a layer of dielectric material on one surface of the glass fiber cloth, and drying and curing to form a dielectric layer to obtain a composite board;

[0066] S2, depositing copper on the surface of the dielectric layer of the composite board and then electroplating copper to obtain a circuit substrate;

[0067] S3, sticking a dry film on the copper alloy surface of the circuit substrate, exposing and developing to obtain a laminated board;

[0068] S4, placing the film-coated board in an electrolytic cell for anode electrolysis to obtain a primary engraved board;

[0069] S5, soaking the primary engraved plate in an etching solution to form a fine engraved plate;

[0070] S6, removing the dry film to obtain the circuit board;

[0071] Wherein, the dielectric material comprises a polymer resin, a curing agent and a filler; the polymer resin is any one of epoxy resin, polyimide resin or phenolic resin or a mixture of at least two thereof; the curing agent is any one of diamine, dianhydride or phenolic resin or a mixture of at least two thereof; the filler is a high thermal conductivity ceramic filler.

[0072] For Examples 1-2 and Comparative Examples, the inventors conducted the following experiments:

[0073] Measurement of etching factor: Figure 1During the etching process, the etching solution will not only erode downwards, but also etch in all directions. Side etching is inevitable. We use the etching factor to reflect the size of the side etching. The side etching factor = side etching width / etching depth. The smaller the etching factor, the better the etching effect and the better the impedance control. The test results are as follows:

[0074]

[0075] It is not difficult to see from the above table that the etching production by the method of the present invention can significantly reduce the side etching of the conductive circuit during the etching process of the etching solution.

[0076] The above only expresses the preferred embodiments of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications, improvements and substitutions can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. An electrolytic etching process for a circuit board, comprising the following steps: S1, coating a layer of dielectric material on at least one side of the carrier material, and drying and curing to form a dielectric layer to obtain a composite board; S2, depositing copper on the surface of the dielectric layer of the composite board and then electroplating a layer of copper alloy to obtain a circuit substrate; after electroplating for 1 hour, adding sodium stannate to the electroplating solution to make its content reach 20-30 g / l; S3, sticking a dry film on the copper alloy surface of the circuit substrate, exposing and developing to obtain a laminated board; S4, placing the film-coated board in an electrolytic cell for anode electrolysis to obtain a primary engraved board; S5, soaking the primary engraved plate in an etching solution to form a fine engraved plate; S6. Remove the dry film to obtain the circuit board.

2. The electrolytic etching process of a circuit board according to claim 1, characterized in that: In step S2, the copper alloy contains at least one non-copper metal, and the non-copper metal is selected from one or more of tin and zinc.

3. The electrolytic etching process of a circuit board according to claim 2, characterized in that: In step S2, the electroplating solution in the electroplating process further includes sodium cyanide, cuprous cyanide and sodium hydroxide.

4. The electrolytic etching process of a circuit board according to claim 3, characterized in that: In step S2, the content of cuprous cyanide is 30-50 g / L, and the content of sodium stannate is 5-15 g / L.

5. The electrolytic etching process of a circuit board according to claim 3, characterized in that: In step S2, the pH of the electroplating solution is 11-12.

6. The electrolytic etching process of a circuit board according to claim 3, characterized in that: In step S2, during the electroplating process, the cathode current density is 9-11A / dm 2 .

7. The electrolytic etching process for a circuit board according to claim 3, characterized in that: In step S2, the electroplating time is 1.5 to 2.5 hours.

8. The electrolytic etching process of a circuit board according to claim 1, characterized in that: In step S1, the carrier material is selected from one of polyimide film, glass fiber cloth or polyvinylidene fluoride film.

9. The electrolytic etching process of a circuit board according to claim 1, characterized in that: In step S1, the dielectric material comprises a polymer resin, a curing agent and a filler; the polymer resin is any one of epoxy resin, polyimide resin or phenolic resin or a mixture of at least two thereof; the curing agent is any one of diamine, dianhydride or phenolic resin or a mixture of at least two thereof; the filler is a ceramic filler.

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