Micro-etching liquid for accurately etching copper surface of high-precision printed circuit board and coarsening method of micro-etching liquid

Abstract

The invention discloses a micro-etching solution for precise etching of a copper surface of a high-precision printed circuit board and a roughening method of the micro-etching solution. The micro-etching solution comprises the following components in percentage by mass: 5%-12% of sulfuric acid, 2%-10% of hydrogen peroxide, 0.05%-0.2% of a roughness control agent, 0.05%-0.2% of an inhibitor and the balance of deionized water. Through mutual cooperation of the roughness control agent and the inhibitor in the micro-etching liquid and combination of a specific coarsening operation method, the bonding strength of a dry film or resin on the copper surface can be effectively improved and kept stable under the low corrosion amount, and meanwhile the requirements of fine line processing and high-precision printed circuit signal transmission for the copper surface appearance are met.

Description

Technical Field

[0001] The present invention relates to a copper surface etching process for printed circuit boards. More specifically, the present invention mainly relates to a micro-etching solution for precisely etching the copper surface of high-precision printed circuit boards and its roughening method. Background Art

[0002] With the rapid development of electronic products towards being thinner, smaller, digital, and multi-functional, precise control of the overall thickness and line density of printed circuit boards poses challenges. Among them, the micro-etching process, as a key link in the manufacturing of high-precision circuit boards, plays a crucial role in the production of high-precision circuit boards such as IC substrates, high-density multilayer boards, and fine-line technology circuit boards. The micro-etching process runs through the pretreatment links of multiple core processes such as pattern transfer, electroless copper plating, solder mask (solder resist), and solder coating, and its process quality directly affects the performance of the final product.

[0003] An ideal micro-etching solution can not only efficiently clean the copper surface but also precisely control the micro-region morphology of the copper surface and increase the copper surface roughness to ensure effective bonding between the copper surface and substrates such as dry film. However, in high-frequency circuit applications, an increase in copper surface roughness will lead to an increase in transmission resistance, further exacerbating high-frequency signal attenuation; while in the manufacturing of fine lines, too low a roughness is difficult to ensure the bonding strength between the copper surface and the dry film. Therefore, precisely controlling the copper surface roughness within the optimal range after micro-etching has become the core challenge of the micro-etching process. Currently, the sulfuric acid / hydrogen peroxide system has become the most widely used system in the micro-etching process due to its advantages such as simple operation, environmental friendliness, low cost, and mature technology. However, this system has problems such as uneven micro-etching, easy oxidation of the copper surface, and generally low roughness, making it difficult to meet the manufacturing requirements of high-end products. Especially with the further miniaturization of the line width / line pitch and thickness of graphic circuits, modern printed circuit boards not only require a smaller micro-etching amount but also need to achieve good bonding between the copper surface and the dry film under low micro-etching amount conditions and form an ideal roughened morphology. Existing traditional roughening formulations and processes can no longer meet these increasingly stringent technical requirements.

[0004] Therefore, developing a micro-etching solution with low micro-etching amount and copper surface roughening for high-precision printed circuit boards has become an urgent technical problem to be solved. This new type of micro-etching solution needs to achieve a low micro-etching amount while forming a uniform honeycomb structure with a relatively high roughness on the copper surface, ensuring sufficient bonding strength between the copper surface and the dry film or resin, and minimizing signal loss during the transmission of printed circuits. This technological breakthrough will be of great significance for promoting the progress of high-end printed circuit board manufacturing technology. Summary of the Invention

[0005] One of the objectives of the present invention is to address the above deficiencies by providing a micro-etching solution for precise etching of the copper surface of high-precision printed circuit boards and its roughening method, with the expectation that using this micro-etching solution can achieve a low micro-etching amount on the copper surface while also having a relatively high roughness, thereby improving the bonding strength between the copper surface and the dry film.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions: On the one hand, the present invention provides a micro-etching solution for precise etching of the copper surface of high-precision printed circuit boards, characterized in that: the micro-etching solution comprises, by mass percentage, 5%-12% sulfuric acid, 2%-10% hydrogen peroxide, 0.05%-0.2% roughness control agent, 0.05%-0.2% inhibitor, and the balance is deionized water; the roughness control agent is a mixture of 4-methylpyrimidine, benzotriazole, 2-imidazolidinone, 2-aminobenzimidazole, 3-amino-1,2,4-triazine, and 3-amino-1H-1,2,4-triazine-5-carboxylic acid; the inhibitor is a mixture of magnesium sulfate, sodium tungstate, nickel sulfate, lanthanum sulfate, isobutylene glycol, diethylene glycol butyl ether, and 1,4-butanediol.

[0007] As a preference, a further technical solution is: the concentration of the sulfuric acid solution is 50-150 g / L, the concentration of the hydrogen peroxide solution is 10-50 g / L, the concentration of the roughness control agent solution is 0.5-5 g / L, and the concentration of the inhibitor solution is 0.5-5 g / L.

[0008] A further technical solution is: the mass ratio of the mixture of 4-methylpyrimidine, benzotriazole, 2-imidazolidinone, 2-aminobenzimidazole, 3-amino-1,2,4-triazine, and 3-amino-1H-1,2,4-triazine-5-carboxylic acid is 0-1.5:0.2-2.0:0-2.0:0.5-2.5:0.3-1.6:0-2.5.

[0009] A further technical solution is: the mass ratio of the inhibitor, which is a mixture of magnesium sulfate, sodium tungstate, nickel sulfate, lanthanum sulfate, isobutylene glycol, diethylene glycol butyl ether, and 1,4-butanediol, is 0.3-1.5:0-2.5:0-1.2:0-2.0:0.2-1.2:0-1.8:0.5-2.5.

[0010] On the other hand, the present invention provides a roughening method for precise etching of the copper surface of high-precision printed circuit boards, and the method comprises the following steps: Step A. Preparation of the micro-etching solution: Prepare the micro-etching solution according to the above-mentioned ratio of the micro-etching solution.

[0011] Step B. Alkaline washing: Spray the high-precision printed circuit board in a sodium hydroxide solution of 5-20 g / L for 10-60 s.

[0012] Step C. First water wash.

[0013] Step D. Acid pickling, spraying the high-precision printed circuit board in a sodium hydroxide solution of 40 - 80 g / L for 20 - 60 s.

[0014] Step E. Second water wash.

[0015] Step F. Micro-etching of the copper surface, spraying the micro-etching solution onto the copper surface of the high-precision printed circuit board and maintaining for 10 - 90 s.

[0016] Step G. Third water wash.

[0017] Step H. After the high-precision printed circuit board is completely dried, the roughening is completed.

[0018] The above first water wash, second water wash, and third water wash are all spraying the high-precision printed circuit board in deionized water for 20 - 60 s.

[0019] Preferably, a further technical solution is that the above method is carried out at a temperature of 20 - 40 °C.

[0020] A further technical solution is that the micro-etching of the copper surface sprays the micro-etching solution onto the copper surface of the high-precision printed circuit board in a horizontal spraying manner, and the spraying pressure is 0.5 - 2.0 kg / cm 2 .

[0021] A further technical solution is that the preparation method of the micro-etching solution is as follows: Weigh sulfuric acid, hydrogen peroxide, roughness control agent, and inhibitor according to the ratio of the above micro-etching solution; Add sulfuric acid to an appropriate amount of deionized water, stir and mix evenly, cool to room temperature, then add hydrogen peroxide solution, and stir and mix evenly; Then add the roughness control agent and inhibitor, stir well to completely dissolve, and then add deionized water to the standard volume to obtain the micro-etching solution.

[0022] Compared with the prior art, one of the beneficial effects of the present invention is that through the mutual cooperation between the roughness control agent and the inhibitor in the micro-etching solution, combined with the specific roughening operation method, it is possible to achieve a relatively high roughness at a low etching amount, effectively improve the bonding strength of the dry film or resin on the copper surface and maintain stability, while meeting the requirements of fine circuit processing and high-precision printed circuit signal transmission for the copper surface morphology. Brief Description of the Drawings

[0023] Figure 1a It is a white light interferometer diagram for illustrating Example 1 of the present invention.

[0024] Figure 1b It is a SEM diagram for illustrating Example 1 of the present invention.

[0025] Figure 2a It is a diagram of a white light interferometer for illustrating Embodiment 2 of the present invention.

[0026] Figure 2b It is a SEM diagram for illustrating Embodiment 2 of the present invention.

[0027] Figure 3a It is a diagram of a white light interferometer for illustrating Embodiment 3 of the present invention.

[0028] Figure 3b It is a SEM diagram for illustrating Embodiment 3 of the present invention.

[0029] Figure 4a It is a diagram of a white light interferometer for illustrating Embodiment 4 of the present invention.

[0030] Figure 4b It is a SEM diagram for illustrating Embodiment 4 of the present invention.

[0031] Figure 5a It is a diagram of a white light interferometer for illustrating Embodiment 5 of the present invention.

[0032] Figure 5b It is a SEM diagram for illustrating Embodiment 5 of the present invention. Detailed implementation manners

[0033] As the requirements for the thickness and line density accuracy of printed circuit boards are getting higher and higher, further improvement is needed in aspects such as micro-etching uniformity, surface roughness, and etching amount. The present invention focuses on and solves problems such as low copper surface roughness and large etching amount in the micro-etching of copper foils with the next-generation small line width and line spacing and low copper thickness.

[0034] Embodiment 1 Prepare a micro-etching solution. Since the specific masses of sulfuric acid, hydrogen peroxide, roughness control agent, and inhibitor cannot be accurately controlled in actual preparation, in this embodiment and the following embodiments, the foregoing components are controlled within the following ranges, that is, 5%-12% sulfuric acid, 2%-10% hydrogen peroxide, 0.05%-0.2% roughness control agent, 0.05%-0.2% inhibitor, and the balance is deionized water.

[0035] According to the above ratios, take the following raw materials: sulfuric acid 80 - 100 g / L, hydrogen peroxide 20 - 30 g / L, roughness control agent 0.5 - 2 g / L, inhibitor 0.5 - 2 g / L, and the solvent is deionized water; the aforementioned roughness control agent is a mixture of 4 - methylpyrimidine, benzotriazole, 2 - imidazolidinone, 2 - aminobenzimidazole, 3 - amino - 1,2,4 - triazine, and 3 - amino - 1H - 1,2,4 - triazine - 5 - carboxylic acid, and their mass ratio is 0.75:1.1:1.0:1.5:0.85:1.25; the aforementioned inhibitor is a mixture of magnesium sulfate, sodium tungstate, nickel sulfate, lanthanum sulfate, isooctyl glycol, diethylene glycol butyl ether, and 1,4 - butanediol, and their mass ratio is 0.9:1.25:0.6:1:0.7:0.9:1.5.

[0036] Prepare the micro - etching solution according to the following method: Add sulfuric acid to an appropriate amount of water, stir and mix evenly, cool to room temperature, then add hydrogen peroxide, stir and mix evenly, then add the roughness control agent and inhibitor, stir well to completely dissolve, and add deionized water to the standard volume to obtain the micro - etching solution for high - precision printed circuit boards with low etching amount and copper surface roughening.

[0037] Use the above micro - etching solution to perform micro - etching treatment on the circuit board. The micro - etching process is as follows: a. Alkaline washing; b. First water washing; c. Acid washing; d. Second water washing; e. Copper surface micro - etching; f. Third water washing; g. Drying the board.

[0038] The above copper surface micro - etching step is: Under the condition of a temperature of 30 °C, spray the micro - etching solution for high - precision printed circuit boards with low etching amount and copper surface roughening onto the circuit board. The spraying method is horizontal spraying, the spraying pressure is 1.5 kg / cm2, and the micro - etching time is 60 s. The alkaline washing step is: Under the condition of a temperature of 30 °C, spray a 10 g / L sodium hydroxide solution evenly onto the circuit board, and the alkaline washing time is 30 s. The acid washing step is: Under the condition of a temperature of 30 °C, spray a 50 g / L sulfuric acid solution evenly onto the circuit board, and the acid washing time is 30 s. The time for the first water washing, the second water washing, and the third water washing is 30 s each. The water washing method is to spray the high - precision printed circuit board in deionized water. The drying the board step is: After the third water washing, blow - dry the circuit board with a hair dryer until it is dry. After the copper surface roughening is completed, the circuit board of Example 1 is obtained. In this example, the white - light interferometer diagram of the micro - etching result of the circuit board is as Figure 1a shown, and the SEM diagram is as Figure 1b shown.

[0039] Example 2 In this embodiment, the mass ratio of the mixture of 4-methylpyrimidine, benzotriazole, 2-imidazolidinone, 2-aminobenzimidazole, 3-amino-1,2,4-triazine, and 3-amino-1H-1,2,4-triazine-5-carboxylic acid in the roughness control agent is 0:0.2:0:0.5:0.3:0, and the mass ratio of the mixture of magnesium sulfate, sodium tungstate, nickel sulfate, lanthanum sulfate, isooctyl glycol, diethylene glycol butyl ether, and 1,4-butanediol in the inhibitor is 0.3:0:0:0:0.2:0:0.5, which is the same as that in Example 1. The white light interferometer diagram of the micro-etching result of the circuit board in this embodiment is as shown in Figure 2a shown, and the SEM diagram is as shown in Figure 2b shown.

[0040] Example 3 In this embodiment, the mass ratio of the mixture of 4-methylpyrimidine, benzotriazole, 2-imidazolidinone, 2-aminobenzimidazole, 3-amino-1,2,4-triazine, and 3-amino-1H-1,2,4-triazine-5-carboxylic acid in the roughness control agent is 1.5:2.0:2.0:2.5:1.6:2.5, and the mass ratio of the mixture of magnesium sulfate, nickel sulfate, sodium tungstate, lanthanum sulfate, isooctyl glycol, diethylene glycol butyl ether, and 1,4-butanediol in the inhibitor is 1.5:2.5:1.2:2.0:1.2:1.8:2.5. It is the same as that in Example 1. The white light interferometer diagram of the micro-etching result of the circuit board in this embodiment is as shown in Figure 3a shown, and the SEM diagram is as shown in Figure 3b shown.

[0041] Example 4 In this embodiment, the mass ratio of the mixture of 4-methylpyrimidine, benzotriazole, 2-imidazolidinone, 2-aminobenzimidazole, 3-amino-1,2,4-triazine, and 3-amino-1H-1,2,4-triazine-5-carboxylic acid in the roughness control agent is 0:0.2:0:0.5:0.3:0, and the mass ratio of the mixture of magnesium sulfate, nickel sulfate, sodium tungstate, lanthanum sulfate, isooctyl glycol, diethylene glycol butyl ether, and 1,4-butanediol in the inhibitor is 1.5:2.5:1.2:2.0:1.2:1.8:2.5. It is the same as that in Example 1. The white light interferometer diagram of the micro-etching result of the circuit board in this embodiment is as shown in Figure 4a shown, and the SEM diagram is as shown in Figure 4b shown.

[0042] Example 5 In this embodiment, the mass ratio of the mixture of 4-methylpyrimidine, benzotriazole, 2-imidazolidinone, 2-aminobenzimidazole, 3-amino-1,2,4-triazine, and 3-amino-1H-1,2,4-triazine-5-carboxylic acid in the roughness control agent is 1.5:2.0:2.0:2.5:1.6:2.5, and the mass ratio of the mixture of magnesium sulfate, nickel sulfate, sodium tungstate, lanthanum sulfate, isobutyleneglycol, diethylene glycol butyl ether, and 1,4-butanediol in the inhibitor is 0.3:0:0:0:0.2:0:0.5. The rest is the same as in Example 1. The white light interferometer diagram of the micro-etching result of the circuit board in this embodiment is as shown in Figure 5a shown, and the SEM diagram is as shown in Figure 5b shown.

[0043] Perform performance tests on the micro-etching solutions prepared in Examples 1-5. The test methods are as follows: 1. Surface appearance: Visually observe that the surface appearance color of the copper surface treated with the micro-etching solution is uniform, not dull, the surface is flat, without pits or scratches, which is qualified.

[0044] 2. Micro-etching amount detection: Detect by measuring the weight change of copper before and after roughening, and control the micro-etching amount between 0.2-0.5 microns.

[0045] 3. Microscopic morphology: Use an SEM scanning electron microscope to test the microscopic morphology after micro-etching. A uniform distribution of concave and convex microporous morphology is qualified.

[0046] 4. Roughness: Detect the roughness after micro-etching with a white light interferometer, and control the Ra value of the roughness between 0.3-0.5.

[0047] The test results are shown in the following table: Example Surface appearance Etching amount Roughness Ra Roughness Sa 1 Qualified 0.3069 0.359 0.408 2 Qualified 0.4337 0.394 0.440 3 Qualified 0.5256 0.430 0.466 4 Unqualified 0.2516 0.265 0.308 5 Unqualified 0.2165 0.348 0.378 It can be seen from Figures 1-5 and the test results in Table 1 that the low-etching amount and the components of the copper surface roughening micro-etching solution provided by the present invention cooperate with each other. The micro-etching solution is stable and can control the copper surface roughness and micro-etching amount within an ideal range.

[0048] As can be seen from the above embodiments, a precise etching preparation process for the copper surface of a high-precision printed circuit board provided by the present invention can achieve a surface roughness of about 0.4 μm at a micro-etching rate of about 0.3 μm / min for the copper foil after treatment by this process, and has a uniform etching morphology. This can not only improve the bonding force between the copper foil and the dry film or resin, but also meet diverse production requirements.

[0049] In addition to the above, it should also be noted that the "one embodiment", "another embodiment", "embodiment", etc. mentioned in this specification refer to the specific features, structures or characteristics described in connection with that embodiment being included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in connection with any embodiment, it is intended that the implementation of such feature, structure or characteristic in combination with other embodiments also fall within the scope of the present invention.

[0050] Although the present invention has been described herein with reference to various illustrative embodiments of the invention, it should be understood that those skilled in the art can devise many other modifications and embodiments that will fall within the scope of the principles of this application as disclosed. More specifically, within the scope of the present application as disclosed, the drawings and the claims, various variations and improvements can be made to the components and / or the layout of the subject combination layout. In addition to the variations and improvements made to the components and / or the layout, other uses will also be apparent to those skilled in the art.

Claims

1. A micro-etching liquid for precise etching of the copper surface of a high-precision printed circuit board, characterized in that: The micro-etching solution comprises, by mass percentage, 5%-12% sulfuric acid, 2%-10% hydrogen peroxide, 0.05%-0.2% roughness control agent, 0.05%-0.2% inhibitor, and the balance is deionized water; The roughness control agent is a mixture of 4-methylpyrimidine, benzotriazole, 2-imidazolidinone, 2-aminobenzimidazole, 3-amino-1,2,4-triazine, and 3-amino-1H-1,2,4-tripyrimidine-5-carboxyl; The inhibitor is a mixture of magnesium sulfate, sodium tungstate, nickel sulfate, lanthanum sulfate, isohexanediol, diethylene glycol butyl ether and 1,4-butanediol.

2. The micro-etching liquid for high-precision copper surface etching of printed circuit boards according to claim 1, characterized in that: The concentration of the sulfuric acid solution is 50-150 g / L, the concentration of the hydrogen peroxide solution is 10-50 g / L, the concentration of the roughness control agent solution is 0.5-5 g / L, and the concentration of the inhibitor solution is 0.5-5 g / L.

3. The micro-etching liquid for high-precision copper surface etching of printed circuit boards according to claim 1, characterized in that: The mass ratio of the mixture of 4-methylpyrimidine, benzotriazole, 2-imidazolidinone, 2-aminobenzimidazole, 3-amino-1,2,4-triazine and 3-amino-1H-1,2,4-tripyrimidine-5-carboxyl is 0-1.5: 0.2-2.0: 0-2.0: 0.5-2.5: 0.3-1.6: 0-2.

5.

4. The micro-etching liquid for high-precision copper surface etching of printed circuit boards according to claim 1 or 3, characterized in that: The inhibitor is a mixture of magnesium sulfate, sodium tungstate, nickel sulfate, lanthanum sulfate, isohexanediol, diethylene glycol butyl ether, and 1,4-butanediol in a mass ratio of 0.3-1.5: 0-2.5: 0-1.2: 0-2.0: 0.2-1.2: 0-1.8: 0.5-2.

5.

5. A roughening method for high-precision printed circuit board copper surface precision etching, characterized in that The method comprises the following steps: The micro-etching solution is prepared according to the proportion of the micro-etching solution according to any one of claims 1 to 4; Alkaline washing: spray the high-precision printed circuit board in 5-20g / L sodium hydroxide solution for 10-60s; First wash; Pickling: spray the high-precision printed circuit board in 40-80g / L sulfuric acid solution for 20-60s; Second wash; Micro-etching the copper surface, spraying the micro-etching liquid onto the copper surface of the high-precision printed circuit board for 10-90 seconds; The third wash; When the high-precision printed circuit board is completely dry, the roughening is completed; The first water washing, the second water washing and the third water washing are all performed by spraying the high-precision printed circuit board in deionized water for 20-60 seconds.

6. The micro-etching liquid for high-precision copper surface etching of printed circuit boards according to claim 5, characterized in that: The method is carried out at a temperature of 20-40°C.

7. The micro-etching liquid for high-precision copper surface etching of printed circuit boards according to claim 5 or 6, characterized in that: The copper surface micro-etching is performed by spraying the micro-etching liquid onto the copper surface of the high-precision printed circuit board in a horizontal manner, and the spraying pressure is 0.5-2.0 kg / cm 2 .

8. The micro-etching liquid for high-precision copper surface etching of a printed circuit board according to claim 5, characterized in that The preparation method of the micro-etching solution is: Weigh sulfuric acid, hydrogen peroxide, a roughness control agent and an inhibitor according to the ratio of the micro-etching solution according to any one of claims 1 to 4; Add sulfuric acid to an appropriate amount of deionized water and stir to mix evenly. After cooling to room temperature, add hydrogen peroxide solution and stir to mix evenly. Then, the roughness control agent and the inhibitor are added, stirred sufficiently to be completely dissolved, and then deionized water is added to the standard volume to obtain the micro-etching solution.

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