Manufacturing method of stepped copper circuit board with through and blind holes in thin copper area

Abstract

The invention discloses a manufacturing method of a stepped copper circuit board with through and blind holes in a thin copper area, and belongs to the technical field of circuit board manufacturing. When the through and blind holes exist in the thin copper area, hole copper requirements of the through and blind holes are preferentially considered for electroplating; after electroplating is completed, the through blind hole is covered with a dry film, and surface copper is thinned to a required copper thickness value of a thin copper area; then, a boss, formed by dry film covering, of the through and blind hole opening is ground to be flat, and a thin copper area pattern is manufactured; covering the thin copper area with a dry film, and electroplating the remaining part to form a thick copper area; and finally, manufacturing a thick copper region pattern to complete the manufacturing of stepped copper. When the method is used for manufacturing the thin copper area, the copper thickness variation of the thin copper area is reduced, and the copper thickness uniformity can be improved; and secondly, after the pattern of the thin copper area is manufactured, the copper thickness of the thick copper area is increased through pattern electroplating, so that the risk of lateral erosion is avoided, and the precision of a finished product circuit is higher.

Description

Technical Field

[0001] The invention belongs to the technical field of circuit board manufacturing, and in particular relates to a manufacturing method of a stepped copper circuit board with through and blind holes in a thin copper area. Background Art

[0002] With the development of autonomous driving technology, the demand for sensor technology is increasing. The millimeter wave radar sensor is one of the most popular hardware at present. The structure of the millimeter wave radar includes an antenna, a receiving and transmitting system, and a signal processing system. The receiving and transmitting system chip and the antenna PCB are the hardware core of the millimeter wave radar. The present invention mainly studies the antenna PCB.

[0003] When designing the antenna part of the antenna PCB, the antenna size tolerance is usually controlled within 15μm. To ensure that the size tolerance of the entire board meets the requirements, the copper thickness of the antenna part often needs to be designed to be slightly thinner to reduce the impact of poor uniformity caused by changes in copper thickness. The non-antenna part is often relatively thicker according to normal design. Due to the difference in copper thickness, the graphics need to be produced separately and the production process needs to be designed to produce stepped copper on the same side to meet the design requirements.

[0004] Moreover, when there are through-holes and blind-holes in the antenna part, the hole copper needs to be plated to the required value before the pattern is made. After the electroplating is completed, the surface copper is often larger than the required value, and the surface copper needs to be thinned at this time, which will affect the hole copper thickness. In this case, how to make both the hole copper and the surface copper meet the design requirements becomes the key point.

[0005] To this end, we propose a method for manufacturing a stepped copper circuit board with through and blind holes in the thin copper area to solve the problems existing in the prior art, so that the copper thickness uniformity is better and the circuit accuracy is higher. Summary of the invention

[0006] The purpose of the present invention is to provide a method for manufacturing a stepped copper circuit board with through-blind holes in a thin copper area, so as to solve the problem that in the conventional stepped copper circuit manufacturing technology mentioned in the above background technology, the copper thickness is usually plated to the thick copper requirement first, and then thinned, and the copper thickness in the thin copper area is reduced to the target value and then the pattern is produced. The corresponding copper thickness variation of the thin copper area is large, which easily leads to poor copper thickness uniformity; secondly, when the thin copper area is thinned, the thick copper area will be eroded at the junction of the thick and thin copper, affecting the accuracy of the finished circuit.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for manufacturing a stepped copper circuit board with through and blind holes in a thin copper area comprises the following steps:

[0009] S1. Electroplating the thin copper area of ​​the circuit board where there are through and blind holes;

[0010] S2. After the circuit board is electroplated, the through and blind holes on the circuit board are covered with dry film, and the copper thickness on the circuit board surface is thinned to be consistent with the thickness of the thin copper area;

[0011] S3, grinding the bosses formed by the dry film covering the through and blind holes of the circuit board, and making thin copper area patterns;

[0012] S4, covering the thin copper area with a dry film, electroplating the remaining part to form a thick copper area, and after the electroplating of the thick copper area is completed, making a pattern of the thick copper area to complete the production of the stepped copper circuit board.

[0013] Preferably, the step S1 of electroplating the thin copper area of ​​the circuit board where the through and blind holes are present comprises the following processes:

[0014] S101. First, the circuit board surface is cleaned to remove the oil and oxide layer on the surface;

[0015] S102. Micro-etching the circuit board to increase the roughness of the copper surface and improve the adhesion of the electroplating layer;

[0016] S103. Perform pre-preg treatment to fully wet the surface of the circuit board so that the plating solution is evenly distributed on the surface of the circuit board;

[0017] S104. Performing an activation treatment to form an active copper layer on the surface of the circuit board to enhance the deposition effect of the electroplating layer on the surface of the circuit board;

[0018] S105. Performing electroplating treatment, immersing the circuit board in an electroplating solution, and depositing copper ions on the surface of the circuit board to form a copper layer through the action of electric current;

[0019] S106. After the electroplating is completed, the circuit board is cleaned to remove the residual electroplating solution;

[0020] S107. Heat-treating the electroplating layer to improve the bonding strength and electrical conductivity of the electroplating layer.

[0021] Preferably, when the circuit board is electroplated in step S105, the electroplating solution consists of copper sulfate, sulfuric acid and additives.

[0022] Preferably, when the circuit board is electroplated in step S105, the current density of the electroplating is 1-3A / dm 2 The electroplating time is 10-30 minutes, and the temperature of the electroplating solution is usually controlled at 25-35℃.

[0023] Preferably, after the circuit board is electroplated in step S2, the through and blind holes on the circuit board are covered with a dry film, and the covering process includes the following steps:

[0024] S201. Cleaning the surface of the circuit board, and after cleaning, micro-etching the surface to increase the roughness of the copper surface and enhance the bonding strength between the dry film and the copper layer;

[0025] S202. Spread the dry film on the surface of the circuit board, cover the through-blind holes with the dry film, use a laminating machine or a manual roller to push from the center outward to remove bubbles so that the dry film fits tightly to the surface of the circuit board;

[0026] S203. The dry film is exposed to UV light, and the exposed dry film is developed to remove the uncured portion and leave the hardened dry film pattern.

[0027] Preferably, in the process of exposing the dry film to UV light in step S203, a Mylar film is used to cover the dry film, and then the dry film is exposed to ultraviolet light for exposure.

[0028] Preferably, in step S3, grinding the bosses formed by the dry film covering at the through-blind holes of the circuit board comprises the following steps:

[0029] S301. Before grinding, an organic film stripper is used to remove the dry film, and a magnifying glass or microscope is used to determine the specific position and height of the boss;

[0030] S302. Use a parallel grinder or a flat grinder to grind the bosses formed by the dry film covering the blind holes of the circuit board;

[0031] S303. After grinding, use deionized water to clean the circuit board to remove copper chips and other residues generated during the grinding process, and use compressed air to blow dry or bake dry.

[0032] Preferably, in the process of grinding the bosses formed by the dry film covering at the through and blind holes of the circuit board in step S302, the pressure applied by the grinder to the circuit board is in the range of 0.5-1 kg / cm2, the grinding speed is 2000-3000 rpm, and the grinding time for each area is 1-3 minutes.

[0033] Preferably, the manufacturing of the thick copper area pattern in step S4 includes the following process flow:

[0034] S401. The copper surface is ground to increase its surface roughness, and then a photosensitive dry film is attached to the treated substrate. The circuit pattern is transferred to the substrate through UV light irradiation and developer treatment, and the uncured dry film portion is etched away to expose the copper surface where the circuit is to be made, and then the exposed dry film is removed to form an inner layer circuit pattern;

[0035] S402. The copper surface is formed into a microscopic roughness and an organic metal layer through chemical reaction to enhance the interlayer adhesion, and each layer of circuits is superimposed and pressed into an integral multilayer board with the prepreg and copper foil according to the process requirements;

[0036] S403. Drill through holes at designated locations to achieve electrical connectivity between layers, and deposit a thin layer of copper on the non-conductive hole wall through a chemical reaction, and then thicken the copper layer on the board surface and in the hole after copper deposition;

[0037] S404. Transferring the outer circuit pattern by laminating, exposing and developing, and adding a copper layer on the exposed copper surface to meet the electrical requirements of the final circuit board;

[0038] S405. Apply solder resist ink and protect the non-welding area through exposure and development to prevent short circuit during welding, and spray tin on the copper surface to maintain good solderability or electrical properties.

[0039] Technical effects and advantages of the present invention: The present invention provides a method for manufacturing a stepped copper circuit board with through and blind holes in a thin copper area, which has the following advantages over the prior art:

[0040] When there are through and blind holes in the thin copper area, the present invention gives priority to the copper requirements of the through and blind holes for electroplating; after the electroplating is completed, the through and blind holes are covered with dry film, and the surface copper is thinned to the required copper thickness value of the thin copper area; then the bosses formed by the through and blind hole openings due to the dry film covering are smoothed, and a thin copper area pattern is produced; then the thin copper area is covered with dry film, and the remaining part is electroplated to form a thick copper area; finally, a thick copper area pattern is produced to complete the step copper production; the thin copper area is produced by the method, the copper thickness variation of the thin copper area is reduced, and the copper thickness uniformity can be improved; secondly, after the thin copper area pattern is produced, the copper thickness of the thick copper area is thickened by pattern electroplating, the risk of side corrosion is avoided, and the finished product circuit has higher precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The present invention is a flow chart of a method for manufacturing a stepped copper circuit board having through and blind holes in a thin copper area. DETAILED DESCRIPTION

[0042] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0043] See also Figure 1The present invention discloses a method for manufacturing a stepped copper circuit board having through and blind holes in a thin copper area, comprising the following steps:

[0044] S1. Electroplating the thin copper area of ​​the circuit board where there are through and blind holes;

[0045] Specifically, the step S1 electroplating the thin copper area of ​​the circuit board where the through and blind holes are present includes the following processes:

[0046] S101. First, the circuit board surface is cleaned to remove the oil and oxide layer on the surface;

[0047] S102. Micro-etching the circuit board to increase the roughness of the copper surface and improve the adhesion of the electroplating layer;

[0048] S103. Perform pre-preg treatment to fully wet the surface of the circuit board so that the plating solution is evenly distributed on the surface of the circuit board;

[0049] S104. Performing an activation treatment to form an active copper layer on the surface of the circuit board to enhance the deposition effect of the electroplating layer on the surface of the circuit board;

[0050] S105. Performing electroplating treatment, immersing the circuit board in an electroplating solution, and depositing copper ions on the surface of the circuit board to form a copper layer through the action of electric current;

[0051] S106. After the electroplating is completed, the circuit board is cleaned to remove the residual electroplating solution;

[0052] S107. Heat-treating the electroplating layer to improve the bonding strength and electrical conductivity of the electroplating layer.

[0053] Furthermore, when the circuit board is electroplated in step S105, the electroplating solution is composed of copper sulfate, sulfuric acid and additives, and the electroplating current density is 1-3A / dm 2 The electroplating time is 10-30 minutes, and the temperature of the electroplating solution is usually controlled at 25-35℃.

[0054] S2. After the circuit board is electroplated, the through and blind holes on the circuit board are covered with dry film, and the copper thickness on the circuit board surface is thinned to be consistent with the thickness of the thin copper area;

[0055] Specifically, after the circuit board is electroplated in step S2, the through and blind holes on the circuit board are covered with a dry film, and the covering process includes the following steps:

[0056] S201. Cleaning the surface of the circuit board, and after cleaning, micro-etching the surface to increase the roughness of the copper surface and enhance the bonding strength between the dry film and the copper layer;

[0057] S202. Spread the dry film on the surface of the circuit board, cover the through-blind holes with the dry film, use a laminating machine or a manual roller to push from the center outward to remove bubbles so that the dry film fits tightly to the surface of the circuit board;

[0058] S203. The dry film is exposed to UV light, and the exposed dry film is developed to remove the uncured portion and leave the hardened dry film pattern.

[0059] Furthermore, in the process of exposing the dry film to UV light in step S203, a Mylar film is used to cover the dry film, and then the dry film is exposed to ultraviolet light for exposure.

[0060] S3, grinding the bosses formed by the dry film covering the through and blind holes of the circuit board, and making thin copper area patterns;

[0061] Specifically, the step S3 of grinding the bosses formed by the dry film covering the through and blind holes of the circuit board comprises the following steps:

[0062] S301. Before grinding, an organic film stripper is used to remove the dry film, and a magnifying glass or microscope is used to determine the specific position and height of the boss;

[0063] S302. Use a parallel grinder or a flat grinder to grind the bosses formed by the dry film covering the blind holes of the circuit board;

[0064] S303. After grinding, use deionized water to clean the circuit board to remove copper chips and other residues generated during the grinding process, and use compressed air to blow dry or bake dry.

[0065] Furthermore, in the process of grinding the bosses formed by the dry film covering at the through and blind holes of the circuit board in step S302, the pressure applied by the grinder to the circuit board is in the range of 0.5-1 kg / cm2, the grinding speed is 2000-3000 rpm, and the grinding time for each area is 1-3 minutes.

[0066] S4, covering the thin copper area with a dry film, electroplating the remaining part to form a thick copper area, and after the electroplating of the thick copper area is completed, making a pattern of the thick copper area to complete the production of the stepped copper circuit board.

[0067] Specifically, the manufacturing of the thick copper area pattern in step S4 includes the following process flow:

[0068] S401. The copper surface is ground to increase its surface roughness, and then a photosensitive dry film is attached to the treated substrate. The circuit pattern is transferred to the substrate through UV light irradiation and developer treatment, and the uncured dry film portion is etched away to expose the copper surface where the circuit is to be made, and then the exposed dry film is removed to form an inner layer circuit pattern;

[0069] S402. The copper surface is formed into a microscopic roughness and an organic metal layer through chemical reaction to enhance the interlayer adhesion, and each layer of circuits is superimposed and pressed into an integral multilayer board with the prepreg and copper foil according to the process requirements;

[0070] S403. Drill through holes at designated locations to achieve electrical connectivity between layers, and deposit a thin layer of copper on the non-conductive hole wall through a chemical reaction, and then thicken the copper layer on the board surface and in the hole after copper deposition;

[0071] S404. Transferring the outer circuit pattern by laminating, exposing and developing, and adding a copper layer on the exposed copper surface to meet the electrical requirements of the final circuit board;

[0072] S405. Apply solder resist ink and protect the non-welding area through exposure and development to prevent short circuit during welding, and spray tin on the copper surface to maintain good solderability or electrical properties.

[0073] In summary, when there are through and blind holes in the thin copper area, the present invention gives priority to the copper requirements of the through and blind holes for electroplating; after the electroplating is completed, the through and blind holes are covered with dry film, and the surface copper is thinned to the required copper thickness value of the thin copper area; then the bosses formed by the through and blind hole openings due to the dry film covering are smoothed, and a thin copper area pattern is produced; then the thin copper area is covered with dry film, and the remaining part is electroplated to form a thick copper area; finally, a thick copper area pattern is produced to complete the step copper production; the thin copper area is produced by the method, which reduces the variation of the copper thickness of the thin copper area and can improve the uniformity of the copper thickness; secondly, after the thin copper area pattern is produced, the copper thickness of the thick copper area is thickened by pattern electroplating, which avoids the risk of side corrosion and makes the finished circuit more accurate.

[0074] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for manufacturing a stepped copper circuit board with through and blind holes in a thin copper area, characterized in that: The following steps are involved: S1. Electroplating the thin copper area of ​​the circuit board where there are through and blind holes; S2. After the circuit board is electroplated, the through and blind holes on the circuit board are covered with dry film, and the copper thickness on the circuit board surface is thinned to be consistent with the thickness of the thin copper area; S3, grinding the bosses formed by the dry film covering the through and blind holes of the circuit board, and making thin copper area patterns; S4, covering the thin copper area with a dry film, electroplating the remaining part to form a thick copper area, and after the electroplating of the thick copper area is completed, making a pattern of the thick copper area to complete the production of the stepped copper circuit board.

2. The method for manufacturing a stepped copper circuit board with through and blind holes in a thin copper area according to claim 1, characterized in that: In step S1, the thin copper area of ​​the circuit board where the through and blind holes are present is electroplated, including the following processes: S101. First, the circuit board surface is cleaned to remove the oil and oxide layer on the surface; S102. Micro-etching the circuit board to increase the roughness of the copper surface and improve the adhesion of the electroplating layer; S103. Perform pre-preg treatment to fully wet the surface of the circuit board so that the plating solution is evenly distributed on the surface of the circuit board; S104. Performing an activation treatment to form an active copper layer on the surface of the circuit board to enhance the deposition effect of the electroplating layer on the surface of the circuit board; S105. Performing electroplating treatment, immersing the circuit board in an electroplating solution, and depositing copper ions on the surface of the circuit board to form a copper layer through the action of electric current; S106. After the electroplating is completed, the circuit board is cleaned to remove the residual electroplating solution; S107. Heat-treating the electroplating layer to improve the bonding strength and electrical conductivity of the electroplating layer.

3. The method for manufacturing a stepped copper circuit board with through and blind holes in a thin copper area according to claim 2, characterized in that: When the circuit board is electroplated in step S105, the electroplating solution is composed of copper sulfate, sulfuric acid and additives.

4. The method for manufacturing a stepped copper circuit board with through and blind holes in a thin copper area according to claim 3, characterized in that: When the circuit board is electroplated in step S105, the current density of the electroplating is 1-3A / dm 2 The electroplating time is 10-30 minutes, and the temperature of the electroplating solution is usually controlled at 25-35℃.

5. The method for manufacturing a stepped copper circuit board with through and blind holes in the thin copper area according to claim 4, characterized in that: After the circuit board is electroplated in step S2, the through and blind holes on the circuit board are covered with a dry film, and the covering process includes the following steps: S201. Cleaning the surface of the circuit board, and after cleaning, micro-etching the surface to increase the roughness of the copper surface and enhance the bonding strength between the dry film and the copper layer; S202. Spread the dry film on the surface of the circuit board, cover the through-blind holes with the dry film, use a laminating machine or a manual roller to push from the center outward to remove bubbles so that the dry film fits tightly to the surface of the circuit board; S203. The dry film is exposed to UV light, and the exposed dry film is developed to remove the uncured portion and leave the hardened dry film pattern.

6. The method for manufacturing a stepped copper circuit board with through and blind holes in the thin copper area according to claim 5, characterized in that: In the process of exposing the dry film to UV light in step S203, Mylar film is used to cover the dry film, and then the dry film is exposed to ultraviolet light for exposure.

7. The method for manufacturing a stepped copper circuit board with through and blind holes in the thin copper area according to claim 6, characterized in that: The step S3 of grinding the bosses formed by the dry film covering the through and blind holes of the circuit board comprises the following steps: S301. Before grinding, an organic film stripper is used to remove the dry film, and a magnifying glass or microscope is used to determine the specific position and height of the boss; S302. Use a parallel grinder or a flat grinder to grind the bosses formed by the dry film covering the blind holes of the circuit board; S303. After grinding, use deionized water to clean the circuit board to remove copper chips and other residues generated during the grinding process, and use compressed air to blow dry or bake dry.

8. The method for manufacturing a stepped copper circuit board with through and blind holes in the thin copper area according to claim 7, characterized in that: In the process of grinding the bosses formed by the dry film covering the through and blind holes of the circuit board in step S302, the pressure applied by the grinder to the circuit board is in the range of 0.5-1 kg / cm2, the grinding speed is 2000-3000 rpm, and the grinding time for each area is 1-3 minutes.

9. The method for manufacturing a stepped copper circuit board with through and blind holes in the thin copper area according to claim 8, characterized in that: The step S4 of making the thick copper area pattern includes the following process flow: S401. The copper surface is ground to increase its surface roughness, and then a photosensitive dry film is attached to the treated substrate. The circuit pattern is transferred to the substrate through UV light irradiation and developer treatment, and the uncured dry film portion is etched away to expose the copper surface where the circuit is to be made, and then the exposed dry film is removed to form an inner layer circuit pattern; S402. The copper surface is formed into a microscopic roughness and an organic metal layer through chemical reaction to enhance the interlayer adhesion, and each layer of circuits is superimposed and pressed into an integral multilayer board with the prepreg and copper foil according to the process requirements; S403. Drill through holes at designated locations to achieve inter-layer electrical connectivity, and deposit a thin layer of copper on the non-conductive hole wall through chemical reaction, and then thicken the copper layer on the board surface and in the hole after copper deposition; S404. Transferring the outer circuit pattern by laminating, exposing and developing, and adding a copper layer on the exposed copper surface to meet the electrical requirements of the final circuit board; S405. Apply solder resist ink and protect the non-welding area through exposure and development to prevent short circuit during welding, and spray tin on the copper surface to maintain good solderability or electrical properties.

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