Alkaline etching solution with high etching factor and application thereof

Abstract

The invention discloses an alkaline etching solution with a high etching factor and application of the alkaline etching solution. The alkaline etching solution with the high etching factor is formed by mixing an alkaline etching basic solution and an etching additive. In the total mass concentration of the alkaline etching liquid with the high etching factor, the etching additive is prepared from the following components in mass concentration: 0.7 to 3g / l of amino-terminated hyperbranched polysiloxane, 0.05 to 0.4 g / l of I <-> and 0.01 to 0.05 g / l of Ni < 2 + >; in the total mass concentration of the alkaline etching solution with the high etching factor provided by the invention, the alkaline etching basic solution comprises the following components in mass concentration: 140-170g / l Cu < 2 + >, 80-120g / l ammonium chloride, 670-700ml / l ammonia water for adjusting the pH value of the alkaline etching solution with the high etching factor to 7.9-8.8, and the balance of solvent water. The alkaline etching solution provided by the invention has a relatively high etching factor, transverse etching is effectively inhibited while a longitudinal etching effect is ensured, and finally, the etching requirement of etching a fine circuit in a PCB subtractive process is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of PCB etching, and in particular to an alkaline etching solution with a high etching factor and application thereof. Background Art

[0002] In subtractive PCB fabrication, a line spacing of 50μm / 50μm is essentially the limit for circuit fabrication. This is primarily due to the unavoidable side erosion caused by lateral etching during the etching process. While semi-additive processes can address this challenge, they require additional equipment and production lines, which represents a significant financial investment for companies.

[0003] In the traditional subtractive method, many existing patents and documents have proposed that the etching factor can be increased and side etching can be reduced by adding some additives to the etching solution, thereby achieving the production of fine circuits. For example, Chinese patents CN103842554A and CN104870689A propose an etching additive selected from N-alkoxylated polyamide, N-alkylated iminodipropionic acid, salts of the above two substances, modified polyglycol ethers and quaternary urea polymers; Chinese patent CN110904456A provides an etching solution including acid, tetravalent cerium salt, imidazoles, sulfonic acids and polyamines; Chinese patent CN116120936A proposes an etching solution based on a sulfuric acid / hydrogen peroxide system, including Including organic acids, imidazole derivatives, and amino acids; Chinese patent CN116732520A invented an additive, which includes 0.2-2.0g / l wetting agent, 2-20g / l organic ligand, 4-26g / l metal complexing agent, 15-80g / L inorganic complexing agent, and water as solvent; wherein the wetting agent is propylene glycol block polyether, the organic complexing agent is at least one of picolinamide and its derivatives, the metal complexing agent is a crown ether with 4-6 oxygen atoms, and the inorganic complexing agent is a water-soluble molybdate.

[0004] However, these additives are primarily used in acidic etching solutions, which themselves cause relatively significant side etching, limiting their potential to improve the etching factor. Alkaline etching solutions etch faster and cause less side etching than acidic solutions, making them more suitable for producing fine circuits on the outer layers of PCBs. However, these outer layers require high-density designs that are "fine, small, narrow, and thin," placing higher demands on the etching factor of alkaline etching solutions. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides an alkaline etching solution, which has a high etching factor and meets the etching requirements of etching fine circuits in the PCB subtractive process.

[0006] The technical solution of the present invention is:

[0007] An alkaline etching solution with a high etching factor, characterized in that it is formed by mixing an alkaline etching base solution and an etching additive;

[0008] In the total mass concentration of the alkaline etching solution with a high etching factor, the etching additive includes the following components in terms of mass concentration: 0.7-3 g / l amino-terminated hyperbranched polysiloxane, 0.05-0.4 g / l - , 0.01~0.05g / lNi 2+ ;

[0009] The structure of the amino-terminated hyperbranched polysiloxane is shown in chemical formula (I):

[0010] Chemical formula (I) is

[0011] Furthermore, in the total mass concentration of the alkaline etching solution with a high etching factor, the alkaline etching base solution includes the following components in terms of mass concentration: 140-170 g / l Cu 2+ , 80-120 g / l ammonium chloride, 670-700 ml / l ammonia water and the balance water, and the pH value of the alkaline etching solution with a high etching factor is adjusted to 7.9-8.8 by the ammonia water.

[0012] The alkaline etching base liquid plays an etching role. Its main chemical reactions during the etching process of PCB copper clad board are:

[0013] Adding ammonia water to the copper chloride solution causes a complex reaction:

[0014] CuCl2+4NH3→Cu(NH3)4Cl2

[0015] During the etching process, the copper on the board surface is [Cu(NH3)4] 2+ Complex ion oxidation, the etching reaction is as follows:

[0016] Cu(NH3)4Cl2+Cu→2Cu(NH3)2Cl2

[0017] The generated [Cu(NH3)2] 1+ Cu + The complex ions have no etching ability. In the presence of excess NH3 and Cl - Under the condition of oxidizing, it can be quickly oxidized by O2 in the air to generate [Cu(NH3)4] 2+ :

[0018] 2Cu(NH3)2Cl2+NH4Cl+2NH3+1 / 2O2→2Cu(NH3)4Cl2+H2O

[0019] During the above etching process, the etching solution not only etches the copper vertically downward, but also diffuses laterally to both sides of the circuit, resulting in excessive erosion of the circuit edge, that is, side etching. Side etching narrows the actual line width and increases the line spacing, resulting in a decrease in circuit accuracy and ultimately impairing product performance.

[0020] In order to achieve the purpose of preventing lateral corrosion, existing etching additives generally all have the function of corrosion inhibitors, that is, they can be adsorbed on the copper surface, and to a certain extent suppress copper from being corroded. In most prior art disclosed etching additives all contain atoms such as N, O, S with lone pairs of electrons, which can be coordinated with the copper atoms containing empty orbitals, realize the adsorption with metal, thereby achieve the purpose of suppressing lateral corrosion. But from the actual application effect, the vast majority of existing corrosion inhibitors can not play the function of preventing lateral corrosion, because etching is not equivalent to corrosion, and the etching speed of PCB etching solution is much greater than common corrosion speed, and general existing corrosion inhibitors can not suppress the lateral corrosion of etching solution to copper at all. In addition, etching additives with anti-lateral corrosion are not only to suppress copper from being corroded, but more importantly, after they are adsorbed on the copper surface, it is necessary to make lateral etching and longitudinal etching form etching speed difference, so as to obtain the circuit pattern of ultra-high etching factor.

[0021] The etching additive provided by the present invention comprises amino-terminated hyperbranched polysiloxane, I - and Ni 2+ After hydrolysis, the siloxane in the amino-terminated hyperbranched polysiloxane rapidly adsorbs onto the metal surface through the shrinkage reaction between the SiOH group and the MeOH (M represents metal) on the metal surface. On the one hand, the siloxane forms a Si-O-Me covalent bond at the metal interface. The reaction mechanism is as follows:

[0022] Si(OR)3+H2O →Si(OH)+3ROH (1)

[0023] Si(OH)+MOH →SiOM+ H2O (2)

[0024] On the other hand, the amino-terminated hyperbranched polysiloxane can also adsorb to the copper surface due to the lone pair of electrons N. Furthermore, due to its hyperbranched structure, the amino-terminated hyperbranched polysiloxane has a strong steric effect, which can further prevent the etching solution from corroding the copper.

[0025] Furthermore, trace amounts of I - and Ni 2+ It may be that a complex complex is formed with amino-terminated hyperbranched polysiloxane and copper, which helps to further improve the etching factor.

[0026] Furthermore, the mass concentration of the amino-terminated hyperbranched polysiloxane is 1.5 to 2.5 g / l.

[0027] Further, the I - The mass concentration is 0.15-0.3 g / l.

[0028] Further, the I - One or more selected from sodium iodide, potassium iodide.

[0029] Further, the Ni 2+ The mass concentration is 0.02-0.04 g / l.

[0030] Further, the Ni 2+ One or more selected from nickel chloride, nickel sulfate.

[0031] The application of the high-etching-factor alkaline etching solution in the field of high-precision circuit boards, characterized in that it comprises the following steps:

[0032] The high-etching-factor alkaline etching solution is sprayed on the copper-clad substrate to be etched, the spraying pressure of the nozzle is 1.0-1.5 kg / cm 2 , and the etching temperature is 40-50 DEG C.

[0033] Further, the copper-clad substrate to be etched is placed in the etching tank, and the etching tank swings automatically forward and backward during the etching process, and the distance between the nozzle and the copper-clad substrate is 4.5-5.5 cm.

[0034] As preferred, the nozzle for spraying the high-etching-factor alkaline etching solution is fan-shaped.

[0035] The alkaline etching solution acts on the copper-clad substrate in a spraying manner, so that the longitudinal flow of the alkaline etching solution is strong, which is beneficial to the longitudinal etching of the copper-clad substrate, and the transverse flow of the alkaline etching solution is weak, thereby further slowing down the transverse etching of the copper-clad substrate by the alkaline etching solution.

[0036] The application has the following beneficial technical effects:

[0037] The alkaline etching solution provided by the application is mixed by an alkaline etching base solution and an etching additive, wherein, during the basic etching process of the alkaline etching base solution, under the synergistic action of the components in the etching additive, the alkaline etching base solution is adsorbed on the copper surface on one hand to inhibit the corrosion of copper, and on the other hand, under the synergistic action of the application method provided by the application, the alkaline etching base solution further makes the speed difference between the transverse etching and the longitudinal etching, and finally realizes the longitudinal etching effect while effectively inhibiting the transverse etching, thereby ensuring the etching requirements of fine lines in the PCB subtractive process. BRIEF DESCRIPTION OF DRAWINGS

[0038] The following drawings are all test pieces with a target line width of 50 μm / 50 μm, which are cut, filled with glue, polished, and then photographed by a metallographic microscope.

[0039] Figure 1 This is a metallographic photograph of the test piece after the etching solution corresponding to Example 1 acts on it;

[0040] Figure 2 This is a metallographic photograph of the test piece after the etching solution corresponding to Example 2 acts on the test piece;

[0041] Figure 3 This is a metallographic photograph of the test piece after the etching solution corresponding to Example 3 acts on it;

[0042] Figure 4 This is a metallographic photograph of the test piece after the etching solution corresponding to Example 4 acts on it;

[0043] Figure 5 This is a metallographic photograph of the test piece after the etching solution corresponding to Example 5 acts on it;

[0044] Figure 6 This is a metallographic photograph of the test piece after the etching solution corresponding to Example 6 acts on it;

[0045] Figure 7 This is a metallographic photograph of the test piece after the etching solution corresponding to Example 7 acts on it;

[0046] Figure 8 This is a metallographic photograph of the test piece after the etching solution corresponding to Example 8 acts on it;

[0047] Figure 9 This is a metallographic photograph of the test piece after the etching solution corresponding to Example 1 acts on it;

[0048] Figure 10 This is a metallographic photograph of the test piece after the etching solution corresponding to Comparative Example 2 acts on it;

[0049] Figure 11 This is a metallographic photograph of the sample after the etching solution corresponding to Example 3 acts on the sample;

[0050] Figure 12 This is a metallographic photograph of the test piece after the etching solution corresponding to Comparative Example 6 acts on it;

[0051] Figure 13 This is a metallographic photograph image of the test piece after the etching solution corresponding to Comparative Example 12 acts on the test piece. DETAILED DESCRIPTION

[0052] In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples. The following examples are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0053] The invention provides an alkaline etching solution with a high etching factor, which is prepared by mixing an alkaline etching base solution and an etching additive with a side etching prevention function.

[0054] In the total mass concentration of the alkaline etching solution with a high etching factor, the alkaline etching base solution includes, by mass concentration, 140 to 170 g / l copper chloride, 80 to 120 g / l ammonium chloride, and 670 to 700 ml / l ammonia water, and solvent water for preparation;

[0055] In the total mass concentration of the alkaline etching solution with a high etching factor, the etching additive includes 0.7 to 3 g / l amino-terminated hyperbranched polysiloxane, 0.05 to 0.4 g / l I - and 0.01~0.05g / l Ni 2+ ; and the alkaline etching solution of the present invention is adjusted with ammonia water so that the pH of the alkaline etching solution is 7.9 to 8.8;

[0056] The structure of amino-terminated hyperbranched polysiloxane is shown in chemical formula (I):

[0057] Chemical formula (I) is

[0058] The amino-terminated hyperbranched polysiloxane was prepared according to the reference “Niu Qiaoxuan. Preparation and Performance Study of Polysiloxane Waterborne Polyurethane. 2020. China Excellent Master's Thesis”;

[0059] I - One or more selected from sodium iodide and potassium iodide;

[0060] The Ni 2+ Selected from one or more of nickel chloride and nickel sulfate.

[0061] Examples 1-8 are alkaline etching solutions with high etching factors provided by the present invention, and their components and amounts (mass concentration g / l) are shown in Table 1; Comparative Examples 1-9 are based on Example 7 as a reference for comparison, and the components and amounts (mass concentration g / l) of the alkaline etching solutions of Comparative Examples 1-9 are shown in Table 2. Comparative Examples 10-11 are also based on Example 7 as a reference for comparison, and the components and amounts (mass concentration g / l) of the alkaline etching solutions of Comparative Examples 10-11 are shown in Table 3.

[0062] Table 1. Components and dosages of alkaline etching solutions with high etching factors in Examples 1-8

[0063]

[0064]

[0065] Table 2. Components and dosages of alkaline etching solutions in Comparative Examples 1-9

[0066]

[0067] Table 3. Components and dosages of alkaline etching solutions in comparative examples 10-11

[0068]

[0069] The present invention also provides an acidic etching solution comparative example 12 with reference to Chinese patent CN116732520 A. The acidic etching solution of comparative example 12 includes an acidic base etching solution (146 g / l Cu 2+ , 30g / l sodium chloride, hydrochloric acid (acid equivalent is 2mol / l, specific gravity 1.295) and a comparative additive, wherein the components and amounts of the comparative additive in Comparative Example 6 are as follows: 0.2g / lL44, 6g / l pyridine-3-carboxamide, 26g / l 18-crown ether-6, 60g / l potassium molybdate and the balance water; the comparative additive is added to the above-mentioned acidic base etching solution according to 3% of the total mass of the acidic base etching solution, and stirred evenly to form the acidic etching solution of Comparative Example 12.

[0070] The test methods and test items involved in the present invention are as follows:

[0071] 1. Test board production

[0072] Test board production process: copper clad substrate film lamination - exposure - development - water washing and drying, where the dry film thickness is 25μm, the copper thickness is 20μm, and the target line width spacing is 50μm / 50μm; each test board is cut into test pieces of size 10cm×8cm. To avoid test errors, the pattern on each test piece is consistent.

[0073] 2. Etching process

[0074] The etching process, i.e., the application method of the alkaline etching solution provided by the present invention in the field of high-precision circuit boards, specifically includes:

[0075] The test piece was fixed in the etching tank, and the etching solution of the above embodiment and comparative example was sprayed at a pressure of 1.0 kg / cm 2 , the nozzle is 5 cm away from the test plate and the etching temperature is 50 ° C. During the etching process, the swing function of the etching tank is started to make the test piece swing back and forth automatically to ensure the uniformity of etching, and the time is kept; after the preset time is up, it is taken out in time, washed with water and blown dry, and then soaked in 3% sodium hydroxide solution for 3 minutes to completely peel off the dry film, and then completely washed with water and blown dry;

[0076] Preferably, the nozzle for spraying the etching liquid in the present invention is fan-shaped.

[0077] 3. Etching factor test

[0078] The etched test pieces were sliced ​​and filled with glue. After polishing, the bottom and top widths of the lines were measured using a metallographic microscope, and the etching factor was calculated. Only the top surface of the test piece was used. Ten sets of data were collected for each embodiment and comparative example. The bottom width of the line was required to be 50±3μm for valid data, and the average etching factor was calculated. The etching factor was calculated using the industry standard: etching factor = copper thickness / [2×(bottom width - top width)].

[0079] The test performances of the etching solutions of Examples 1-8 and Comparative Examples 1-12 are shown in Table 4.

[0080] Table 4. Test performance of etching solutions of Examples 1-8 and Comparative Examples 1-12

[0081]

[0082]

[0083] The etching factor is a key parameter for measuring the quality of PCB etching process. It is used to describe the proportional relationship between the vertical etching depth and the lateral side etching width during the etching process. The larger the etching factor, the smaller the side etching, the steeper the line edge, and the closer the line shape is to a rectangle, which is more suitable for high-precision circuit production.

[0084] From the data in Table 4, it can be seen that Examples 1-8 all have relatively high average etching factors, with the average etching factors ranging from 10.6 to 15.5. Figures 1-8 It can also be seen that the line shape of the test piece etched by the alkaline etching solution of Examples 1-8 is close to a rectangle, which shows that the alkaline etching solution of the present invention has a high etching factor and can effectively suppress side etching during the etching process, ensuring the production of high-precision circuits.

[0085] Comparative Example 1 is compared with Example 7, which only has alkaline etching base liquid, and its average etching factor is only 2.9. Figure 9 As shown, the line shape of the test piece it has acted on corresponds to a trapezoid, that is, the accuracy of the circuit it has produced is poor.

[0086] Compared with Comparative Example 1, Comparative Example 2 is added with amino-terminated hyperbranched polysiloxane. Due to the rapid adsorption of the siloxane on the metal surface by the shrinkage reaction of the SiOH group and the copper surface after the hydrolysis of the amino-terminated hyperbranched polysiloxane, the adsorption of the lone pair electrons N of the amino group on the copper surface and the steric hindrance brought by its hyperbranched structure, the average etching factor of the comparative example 2 is improved relative to the average etching factor of the alkaline etching base solution in Comparative Example 1. The average etching factor is 9, which is 68% higher than that in Comparative Example 1, which also shows that the alkaline etching solution has a large room for improvement in anti-side corrosion. However, due to the lack of I - and Ni2+ A complex complex is further formed with amino-terminated hyperbranched polysiloxane and copper to further adjust the etching rate difference between the lateral etching and the vertical etching, so that the average etching factor is significantly lower than the average etching factor of Examples 1-8.

[0087] Similarly, in Comparative Examples 3-9, due to the lack of any component of the etching solution additive of the present invention, or the excessive or insufficient addition of a certain component, a good synergistic effect of preventing side corrosion cannot be formed with the alkaline etching base solution of the present invention, so the average etching factor is small. Figure 11-12 As shown, the line shape of the test piece after the action is similar to a trapezoid, that is, the line accuracy is also poor.

[0088] Although the average etching factor of Comparative Example 10 is improved compared to the average etching factor of Comparative Example 1, it is significantly lower than the average etching factor of Examples 1-8. The reason for this is that amino-terminated polydimethylsiloxane does not have the hyperbranched structural characteristics of amino-terminated hyperbranched polysiloxane, which results in its limited effect in improving the etching factor. Comparative Example 11 replaces amino-terminated hyperbranched polysiloxane with the more common corrosion inhibitor benzotriazole, and its average etching factor is only 2.8, which is comparable to the average etching factor of the alkaline etching base solution in Comparative Example 1. This also shows that existing general corrosion inhibitors are simply unable to suppress the lateral etching of copper by etching solutions.

[0089] Comparative Example 12 is an acidic etchant to which a comparative example additive is added, and its average etching factor is 5.8, which is higher than the alkaline etching base solution of Comparative Example 1, but it is also much lower than the average etching factor of Comparative Example 2 and any etching solution of Examples 1-8, which also illustrates that the extent to which the acidic etching solution improves its side corrosion resistance by the additive is relatively limited.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An alkaline etching solution with a high etching factor, characterized in that It is a mixture of alkaline etching base liquid and etching additives; In the total mass concentration of the alkaline etching solution with a high etching factor, the etching additive includes the following components in terms of mass concentration: 0.7-3 g / l amino-terminated hyperbranched polysiloxane, 0.05-0.4 g / l - , 0.01~0.05g / lNi 2+ ; The structure of the amino-terminated hyperbranched polysiloxane is shown in chemical formula (I): Chemical formula (I) is 2. The alkaline etching solution with a high etching factor according to claim 1, wherein In the total mass concentration of the alkaline etching solution with a high etching factor, the alkaline etching base solution includes the following components in terms of mass concentration: 140-170 g / l Cu 2+ , 80-120 g / l ammonium chloride, 670-700 ml / l ammonia water and the balance water, and the pH value of the alkaline etching solution with a high etching factor is adjusted to 7.9-8.8 by the ammonia water.

3. The alkaline etching solution with a high etching factor according to claim 1, wherein The mass concentration of the amino-terminated hyperbranched polysiloxane is 1.5 to 2.5 g / l.

4. The alkaline etching solution with a high etching factor according to claim 1, wherein I - The mass concentration is 0.15~0.3g / l.

5. The alkaline etching solution with a high etching factor according to claim 1, wherein I - Selected from one or more of sodium iodide and potassium iodide.

6. The alkaline etching solution with a high etching factor according to claim 1, wherein The Ni 2+ The mass concentration is 0.02~0.04g / l.

7. The alkaline etching solution with a high etching factor according to claim 1, characterized in that: The Ni 2+ Selected from one or more of nickel chloride and nickel sulfate.

8. An application of an alkaline etching solution with a high etching factor as claimed in any one of claims 1 to 7 in the field of high-precision circuit boards, characterized in that: The steps include: The copper-clad substrate to be etched is sprayed with the alkaline etching solution with a high etching factor, and the spray pressure of the nozzle is 1.0-1.5 kg / cm 2 , etching temperature 40~50℃.

9. Application of the alkaline etching solution with a high etching factor in the field of high-precision circuit boards according to claim 8, characterized in that: The copper-clad substrate to be etched is placed in the etching tank. During the etching process, the etching tank automatically swings back and forth, and the distance between the nozzle and the copper-clad substrate is 4.5 to 5.5 cm.

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