Hole-filling copper plating method

Abstract

The invention discloses a hole-filling copper plating method which comprises the following steps: step 1, weighing a certain amount of copper sulfate, sulfuric acid and chloride ion solution according to a mass ratio, and mixing the certain amount of copper sulfate, sulfuric acid and chloride ion solution to obtain a basic solution; step 2, adding a certain amount of leveling agent, brightening agent and wetting agent into the basic solution, and then mixing the basic solution with the added leveling agent, brightening agent and wetting agent to obtain an acidic copper plating solution; step 3, removing drilling dirt from the punched substrate, then carrying out chemical copper plating through an acidic copper plating solution, and depositing a uniform conductive layer on the non-metal hole wall of the through hole, so that the conductive layer is gathered in a high-potential area, copper ion deposition in the area is inhibited, and the whole circuit board is electroplated to be flat and smooth; by adding a leveling agent, a brightening agent and a wetting agent, the uniform plating and deep plating performance is improved, the crystallization fineness of a plating layer is improved, and the copper plating method with the quaternary ammonium salt sulfur compound serving as the hole filling function is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of hole-filling copper plating on printed circuit boards, in particular to a hole-filling copper plating method. Background Art

[0002] Printed circuit boards are the support for electronic components and the carrier for electrical connections of electronic components. They are widely used in various electronic products. As electronic products gradually develop towards intelligence, miniaturization, convenience, and multi-functions, PCB boards are required to develop towards miniaturization and high density at the same time. Thus, printed circuit boards representing high-density interconnection technology came into being.

[0003] Copper has good electrical conductivity, thermal conductivity and good mechanical properties, and can form metal-to-metal bonding with other metals to obtain a strong interface, so electroplated copper is widely used in PCB manufacturing. In order to strengthen the connection between PCB layers and increase the connectable or mounting area on the hole, the hole electroplating copper filling technology is adopted, including copper plating for through-hole filling.

[0004] In the field of chemistry, quaternary ammonium salt-type substances or dye compounds are easily adsorbed on the surface of the plated component where the current density is high. Sulfur-containing compounds can reduce the precipitation potential of copper. In order to further effectively fill the holes with copper plating, we propose a method for filling the holes with copper plating using quaternary ammonium salt sulfur compounds. Summary of the invention

[0005] The object of the present invention is to provide a hole-filling copper plating method based on quaternary ammonium salt sulfur compounds to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A hole-filling copper plating method comprises the following steps:

[0008] Step 1: Weigh a certain amount of copper sulfate, sulfuric acid and chloride ion solution according to the mass ratio, and mix a certain amount of copper sulfate, sulfuric acid and chloride ion solution to obtain a base solution;

[0009] Step 2: adding a certain amount of leveling agent, brightener and wetting agent to the base liquid, and then mixing the base liquid with the added leveling agent, brightener and wetting agent to obtain an acid copper plating solution;

[0010] Step 3: After the punched substrate is decontaminated, it is chemically copper plated with an acid copper plating solution to deposit a uniform conductive layer on the non-metal hole wall of the through hole, thereby gathering in the high potential area to inhibit the deposition of copper ions in this area, so that the overall circuit board electroplating is flat and smooth.

[0011] As a further solution of the present invention: the leveling agent includes a quaternary ammonium salt type substance or a dye compound.

[0012] As a further embodiment of the present invention: the brightener comprises a sulfur-containing compound.

[0013] As a further solution of the present invention: the wetting agent includes polyoxyethylene polyoxypropylene compounds.

[0014] As a further solution of the present invention: in the hole filling copper plating method, the substrate also includes pre-treatment before drilling, and the pre-treatment steps include swelling and decontamination.

[0015] As a further solution of the present invention: the degreasing process includes a degreasing agent, and the degreasing agent includes the electroplating degreasing agent PP601plus.

[0016] As a further solution of the present invention: the source of the chloride ion solution is hydrochloric acid.

[0017] As a further scheme of the present invention: the synthesis method of the leveling agent comprises: adding an amine substance and glycidyl ether A into a reaction kettle, controlling the ambient temperature to 20°C-30°C, and stirring at a rate of 150-300 rpm for 12-36 hours; after the reaction is completed, rotary evaporating the mixture to obtain a yellow oily compound; adding a quaternary ammonium substance to the above oily compound solution, heating the oil bath to 82°C-125°C, stirring at a rate of 145-300 rpm for 9-12 hours, completing the quaternization reaction, and obtaining a quaternary ammonium salt type leveling agent.

[0018] As a further solution of the present invention: the brightener preparation method comprises: adding deionized water into a reactor, starting stirring, slowly adding sulfuric acid, and stirring evenly; adding polyether, polyethylene glycol 20000, and sodium polydisulfide propane sulfonate into the reactor in sequence and stirring until completely dissolved; adding formaldehyde into the reactor and stirring evenly; adding gallstones into the reactor and stirring until completely dissolved evenly, thereby obtaining the brightener.

[0019] As a further embodiment of the present invention: the polyether is any one of propylene glycol block polyether, polyether F-6, polyether NPE-108, polyether NPE-105 and random polyether.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] A hole-filling copper plating method using a quaternary ammonium salt sulfur compound phase is realized. The hole-filling copper plating method realizes that the acidic copper plating solution used has excellent negative high potential aggregation ability and certain polarity, and can be complexed with other ions in the acidic plating solution, thereby being aggregated in a high potential area, inhibiting the deposition of copper ions in this area, thereby making the electroplating of the entire circuit board flat and smooth; by adding a leveling agent, a brightener, and a wetting agent, the throwing and deep plating performances are improved, and the crystallization fineness of the coating is improved; the three additives of the leveling agent, the brightener, and the wetting agent cooperate with each other to realize the super-equi-area mode deposition of the hole-filling copper plating, and complete the hole filling; the leveling agent, the brightener, and the wetting agent are added to the base liquid and mixed evenly, the preparation process is simple, the reaction conditions are not harsh, and large-scale production is easy to achieve. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the process of the hole filling copper plating method of the present invention. DETAILED DESCRIPTION

[0023] In one embodiment, Figure 1 As shown, a via-filling copper plating method comprises the following steps:

[0024] Step 1: Weigh a certain amount of copper sulfate, sulfuric acid and chloride ion solution according to the mass ratio, and mix a certain amount of copper sulfate, sulfuric acid and chloride ion solution to obtain a base solution;

[0025] Step 2: adding a certain amount of leveling agent, brightener and wetting agent to the base liquid, and then mixing the base liquid with the added leveling agent, brightener and wetting agent to obtain an acid copper plating solution;

[0026] Step 3: After the punched substrate is decontaminated, it is electroplated with an acid copper plating solution to deposit a uniform conductive layer on the non-metal hole wall of the through hole, thereby gathering in the high potential area to inhibit the deposition of copper ions in this area, so that the overall circuit board electroplating is flat and smooth;

[0027] Step three specifically includes the following steps:

[0028] 1. Swelling: putting the substrate into a swelling solution for swelling treatment, wherein the temperature of the swelling solution is 65° C. to 75° C.; after the swelling treatment, the substrate needs to be washed with water to remove residual drugs;

[0029] 2. To remove the drilling dirt, put the expanded substrate into the ultrasonic solution, the sodium permanganate concentration in the ultrasonic solution is 50g / L-70g / L, the sodium manganate concentration is less than or equal to 20g / L, and the NaOH concentration is 30g / L-50g / L; the solution specific gravity of the ultrasonic solution is less than or equal to 1.28g / cm3, the solution temperature range is 70℃-80℃, the resin etching amount range is 0.2μm-1.0μm, and the ultrasonic efficiency is 70%-100%;

[0030] After removing the drilling contamination, the substrate needs to be processed through the following steps: recovery water washing → water washing → neutralization → water washing → cleaning → water washing → weak etching → water washing → pre-immersion → activation (palladium) → water washing → reduction → water washing; the above steps can clean the burnt debris in the laser drilling.

[0031] Copper sulfate: Mainly provides the Cu required for electroplating 2+ ;

[0032] Sulfuric acid: Its main function is to make the plating solution have sufficient conductivity and improve the uniformity of electroplating;

[0033] Chloride ion solution: Its main function is to control the dissolution of the anode and form the intermediates of brightener and wetting agent;

[0034] Leveling agents include quaternary ammonium salt-type substances or dye compounds, which are easily adsorbed on the surface of the plated part where the current density is high, competing with copper ions, making it difficult for copper ions to deposit at high potentials, but not affecting copper deposition in low current areas;

[0035] Leveling agent is a high-strength inhibitor. In the copper plating solution, due to the polarization phenomenon caused by electroplating, the leveling agent will move toward the cathode and adsorb on the cathode surface. Due to the existence of the tip discharge phenomenon, the charge on the cathode surface will be enriched in the protruding parts of the cathode surface. The microscopic peaks on the cathode surface are easier to adsorb the leveling agent than the valleys, so more leveling agent particles will be adsorbed, thereby increasing the reaction resistance of the high current intensive area and reducing the deposition of copper ions. After a certain period of time, the microscopic valleys are gradually filled with the coating, making the coating leveled.

[0036] The electrochemical behavior of the leveler during hole filling is not only related to the polarization and positively charged functional groups of the leveler itself, but also to the strong convection behavior of the electroplating solution. The blind holes on the electroplated parts are limited by processing conditions, and the aperture ratio is very different. In this case, the effect of the dispersant on the narrow aperture is poor. Therefore, when preparing the quaternary ammonium salt dispersant, the amine substances selected in the present invention are all short-chain, so that the prepared dispersant particle size is smaller and can play a certain role of a surfactant, further strengthening its transfer from the cathode surface to the dispersion in the plating solution, so that it can also play an excellent leveling effect in the blind hole environment with a large aperture ratio.

[0037] The electroplating levelers currently on the market all have a relatively limited scope of application, and have strict restrictions on the width and aperture ratio of the blind holes. The leveler prepared by the present invention contains a quaternary ammonium salt dispersant, which has a nitrogen-containing heterocycle inside and has a high positive charge. It will undergo polar adsorption with the cathode, thereby forming a reaction resistance on the surface of the cathode adsorption, reducing the deposition and solidification of copper ions. The leveler prepared by the present invention has a large molecular weight, carries more positive charges, and has a polyether structure with an inhibitor in its internal structure, which has a greater impact on the current on the cathode. Due to the increase in its molecular weight, the leveler prepared by the present invention is less affected by convection, and can improve the uniformity of the filling of the leveler while enhancing the filling ability of the leveler, prevent the filling defects caused by insufficient convection in the electroplating cell, and further improve the product yield.

[0038] Brighteners include sulfur-containing compounds; they can produce a depolarizing effect with the assistance of chloride ions, that is, they complex with copper ions, reduce the copper precipitation potential, and accelerate the deposition rate of copper plating;

[0039] Wetting agents include polyoxyethylene and polyoxypropylene compounds; they can reduce the surface tension of the plating solution, and under the synergistic effect of chloride ions, increase the discharge resistance of the surface copper, inhibit the growth of the surface copper thickness, and produce polarization. In addition, it has a certain wetting effect on small holes and can help the brightener go to the cathode depression.

[0040] By adding leveling agent, brightener and wetting agent, the throwing and deep plating performances are improved, and the crystal density of the coating is improved. The three additives of leveling agent, brightener and wetting agent cooperate with each other to achieve super equal volume deposition of hole filling copper plating and complete hole filling.

[0041] In the hole-filling copper plating method, the substrate also includes pre-treatment before drilling, and the pre-treatment steps include swelling and decontamination;

[0042] The degreasing process includes a degreasing agent, and the degreasing agent includes an electroplating degreasing agent PP601plus;

[0043] The source of the chloride ion solution is hydrochloric acid;

[0044] The synthesis method of the leveling agent comprises the following steps: adding an amine substance and glycidyl ether A into a reaction kettle, controlling the ambient temperature to be 20°C-30°C, and stirring at a rate of 150-300 rpm for 12-36 hours; after the reaction is completed, rotary evaporating the mixture to obtain a yellow oily compound; adding a quaternary ammonium substance to the above oily compound solution, heating the oil bath to 82°C-125°C, and stirring at a rate of 145-300 rpm for 9-12 hours to complete the quaternary ammonium reaction, thereby obtaining a quaternary ammonium salt type leveling agent;

[0045] The brightener preparation method comprises the following steps: adding deionized water into a reaction kettle, starting stirring, slowly adding sulfuric acid, and stirring evenly; sequentially adding polyether, polyethylene glycol 20000, and sodium polydisulfide propane sulfonate into the reaction kettle and stirring until completely dissolved; adding formaldehyde into the reaction kettle and stirring evenly; adding gallstones into the reaction kettle and stirring until completely dissolved evenly, thereby obtaining the brightener; the polyether is any one of propylene glycol block polyether, polyether F-6, polyether NPE-108, polyether NPE-105, and random polyether;

[0046] The hole-filling copper plating method of the invention comprises pretreatment, electroplating process and post-treatment, and the current density of the electroplating process is 15ASF-18ASF.

[0047] A hole-filling copper plating method using a quaternary ammonium salt sulfur compound is realized. The hole-filling copper plating method and the hole-filling copper plating liquid of the present invention cooperate to produce a good hole-filling effect, and 3, 4, and 5 mil laser holes are filled at the same time, and the dimple value is less than 15 μm.

[0048] Example 1

[0049] This embodiment prepares an acid copper plating solution, including a base solution, a leveling agent, a brightener and a wetting agent;

[0050] in:

[0051] The base solution includes: copper sulfate 245g / L-300g / L, sulfuric acid 18mL / L-25mL / L and chloride ion solution 42ppm-75ppm;

[0052] Leveling agent 28mL / L, brightener 1.3mL / L, wetting agent 22.5mL / L;

[0053] Example 2

[0054] This embodiment prepares an acid copper plating solution, including a base solution, a leveling agent, a brightener and a wetting agent;

[0055] in:

[0056] The base solution includes: copper sulfate 245g / L-300g / L, sulfuric acid 18mL / L-25mL / L and chloride ion solution 42ppm-75ppm;

[0057] Leveling agent 28mL / L, brightener 1.5mL / L, wetting agent 23mL / L;

[0058] Example 3

[0059] This embodiment prepares an acid copper plating solution, including a base solution, a leveling agent, a brightener and a wetting agent;

[0060] in:

[0061] The base solution includes: copper sulfate 245g / L-300g / L, sulfuric acid 18mL / L-25mL / L and chloride ion solution 42ppm-75ppm;

[0062] Leveling agent 28mL / L, brightener 1.6mL / L, wetting agent 24mL / L;

[0063] Example 4

[0064] This embodiment prepares an acid copper plating solution, including a base solution, a leveling agent, a brightener and a wetting agent;

[0065] in:

[0066] The base solution includes: copper sulfate 245g / L-300g / L, sulfuric acid 18mL / L-25mL / L and chloride ion solution 42ppm-75ppm;

[0067] Leveling agent 28mL / L, brightener 1.5mL / L, wetting agent 27mL / L;

[0068] Example 5

[0069] This embodiment prepares an acid copper plating solution, including a base solution, a leveling agent, a brightener and a wetting agent;

[0070] in:

[0071] The base solution includes: copper sulfate 245g / L-300g / L, sulfuric acid 18mL / L-25mL / L and chloride ion solution 42ppm-75ppm;

[0072] Leveling agent 28mL / L, brightener 1.7mL / L, wetting agent 29mL / L.

[0073] The acid copper plating solution prepared in Examples 1-5 was subjected to a blind hole filling test: a printed circuit board with a blind hole was used as a cathode and an insoluble titanium mesh was used as an anode, and the blind hole was electroplated for 35 minutes. The test results are shown in Table 1.

[0074] Table 1 Test results

[0075] sample Plate thickness / mm Aperture Hole filling defect Ductility Filling rate Example 1 0.8 3.5mil There are some defects 15.5％ 88.9％ Example 2 0.8 3.5mil none 20.8％ 89.8％ Example 3 0.8 3.5mil none 25.7％ 98.4％ Example 4 0.8 3.5mil none 26.4％ 100％ Example 5 0.8 3.5mil none 28％ 100％

[0076] It can be seen from Table 1 that the more additive components are contained in the acid copper plating solution of the present invention, the higher the performance of the hole-filling copper plating is. While ensuring the excellent physical properties of the hole-filling copper plating, the efficiency of the plating solution for hole-filling copper plating is greatly improved and the performance in various aspects is enhanced. Among them, Embodiment 4 and Embodiment 5 are the best, which make the hole-filling copper plating process better in quality, lower in cost, and more reliable.

[0077] The hole-filling copper plating method of the invention realizes a hole-filling copper plating method using a quaternary ammonium salt sulfur compound phase. The hole-filling copper plating method can improve electrical performance, is helpful for high-frequency design, improves connection reliability, increases operating frequency and avoids electromagnetic interference; hole plugging and electrical interconnection are completed in one step, avoiding defects caused by using resin and conductive glue to fill holes, and at the same time, also avoiding the CTE difference phenomenon caused by other materials to fill holes; electroplated copper is used to fill holes in blind holes, avoiding surface defects, which is conducive to the design and production of more sophisticated circuits; after electroplating hole filling, there is a copper column in the hole, which has better conductivity than conductive resin and can improve the heat dissipation performance of the board.

[0078] The present invention realizes that the acid copper plating solution used has excellent negative high potential aggregation ability and certain polarity, and can be complexed with other ions in the acid plating solution, thereby aggregating in the high potential area, inhibiting the deposition of copper ions in this area, so that the electroplating of the entire circuit board is flat and smooth; by adding a leveling agent, a brightener, and a wetting agent, the leveling and deep plating performances are improved, and the crystallization fineness of the coating is improved. The three additives of the leveling agent, the brightener, and the wetting agent cooperate with each other to realize the super equal volume mode deposition of the hole-filling copper plating, and complete the hole filling; the leveling agent, the brightener, and the wetting agent are added to the base liquid and mixed evenly, the preparation process is simple, the reaction conditions are not harsh, and large-scale production is easy to achieve.

[0079] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for filling a hole with copper plating, characterized in that: The following steps are involved: Step 1: Weigh a certain amount of copper sulfate, sulfuric acid and chloride ion solution according to the mass ratio, and mix a certain amount of copper sulfate, sulfuric acid and chloride ion solution to obtain a base solution; Step 2: adding a certain amount of leveling agent, brightener and wetting agent to the base liquid, and then mixing the base liquid with the added leveling agent, brightener and wetting agent to obtain an acid copper plating solution; Step 3: After the punched substrate is decontaminated, it is chemically copper plated with an acid copper plating solution to deposit a uniform conductive layer on the non-metal hole wall of the through hole, thereby gathering in the high potential area to inhibit the deposition of copper ions in this area, so that the overall circuit board electroplating is flat and smooth.

2. A via-filling copper plating method according to claim 1, characterized in that: The leveling agent includes a quaternary ammonium salt type substance or a dye compound.

3. A via-filling copper plating method according to claim 1, characterized in that: The brightener includes a sulfur-containing compound.

4. A via-filling copper plating method according to claim 1, characterized in that: The wetting agent includes polyoxyethylene polyoxypropylene compounds.

5. A via-filling copper plating method according to claim 1, characterized in that: In the hole-filling copper plating method, a pre-treatment is also performed before drilling holes in the substrate, and the pre-treatment steps include swelling and decontamination.

6. A via-filling copper plating method according to claim 5, characterized in that: The degreasing process includes a degreasing agent, and the degreasing agent includes an electroplating degreasing agent PP601plus.

7. A via-filling copper plating method according to claim 1, characterized in that: The source of the chloride ion solution is hydrochloric acid.

8. A via-filling copper plating method according to claim 1, characterized in that: The synthesis method of the leveling agent comprises the following steps: adding an amine substance and glycidyl ether A into a reaction kettle, controlling the ambient temperature to be 20°C-30°C, and stirring at a rate of 150-300 rpm for 12-36 hours; after the reaction is completed, rotary evaporating the mixture to obtain a yellow oily compound; adding a quaternary ammonium substance into the oily compound solution, heating the oil bath to 82°C-125°C, and stirring at a rate of 145-300 rpm for 9-12 hours to complete the quaternary ammonium reaction, thereby obtaining a quaternary ammonium salt type leveling agent.

9. A via-filling copper plating method according to claim 1, characterized in that: The brightener preparation method comprises the following steps: adding deionized water into a reaction kettle, starting stirring, slowly adding sulfuric acid, and stirring evenly; sequentially adding polyether, polyethylene glycol 20000, and sodium polydisulfide propane sulfonate into the reaction kettle and stirring until completely dissolved; adding formaldehyde into the reaction kettle and stirring evenly; adding gallstones into the reaction kettle and stirring until completely dissolved evenly, thereby preparing the brightener.

10. A via-filling copper plating method according to claim 9, characterized in that: The polyether is any one of propylene glycol block polyether, polyether F-6, polyether NPE-108, polyether NPE-105 and random polyether.

Images