Ion palladium activation solution for electroless copper plating and preparation method thereof

Abstract

This invention relates to the field of ionic palladium activation solution technology, and discloses an ionic palladium activation solution for electroless copper plating and its preparation method. The ionic palladium activation solution comprises palladium sulfate, carbon nanoparticles, emulsifier, stabilizer, pH adjuster, and deionized water. This invention uses carbon nanoparticles instead of traditional complexing agents, which have a large specific surface area, strong adsorption performance, and numerous active sites, enabling the adsorption of more palladium ions and stronger adhesion to the substrate, thereby achieving a better activation effect and improving the backlighting effect and adhesion of the electroless copper plating layer.

Description

Technical Field

[0001] This invention relates to the field of ionic palladium activation solution technology, specifically to an ionic palladium activation solution for chemical copper plating and its preparation method. Background Technology

[0002] Chemical copper plating is a common process in the production of printed circuit boards (PCBs), often referred to as immersion copper plating. Before chemical copper plating, the plastic substrate must undergo activation treatment to adsorb a layer of catalytically active particles onto its surface. Typically, palladium particles are used. Copper ions are first reduced to copper atoms on these catalytically active palladium particles. The reduced copper atoms themselves then become catalytic centers for the copper ions, causing continuous reduction reactions on the surface of newly formed copper atoms. This process leads to the continuous deposition of a copper layer, ultimately forming a uniform conductive copper layer on the substrate surface. The activation process plays a crucial role in chemical copper plating, directly determining the quality of the plated copper layer. Currently, ionic palladium activation solutions are most commonly used in production to activate the substrate surface. With the development of high-density interconnect technology in PCBs and the integration and miniaturization of electronic components, the circuitry in PCBs is becoming increasingly complex, and the apertures are becoming smaller. This places higher demands on the activation performance of ionic palladium activation solutions.

[0003] The patent application number CN202010783640.X discloses an ionic palladium activation solution for horizontal copper plating. The problem with the ionic palladium activation solution in this patent is that the palladium ion concentration is too low, which can easily cause incomplete plating, and the activation time is too long, resulting in low production efficiency.

[0004] Therefore, it is very important to develop an ionic palladium activation solution with good activation effect, high efficiency and long service life. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an ionic palladium activating solution for electroless copper plating and its preparation method. The ionic palladium activating solution of this invention has good activation performance, low surface tension, and strong wettability on the hole walls. During the electroless copper plating process, it enables the copper layer to be uniformly deposited on the hole walls, resulting in a high backlight rating on the obtained circuit board, good copper layer adhesion, and the activating solution has good stability and a long service life.

[0006] To achieve the above objectives, the technical solution of the present invention is: an ionic palladium activation solution for chemical copper plating, wherein the ionic palladium activation solution comprises palladium sulfate, carbon nanoparticles, emulsifier, stabilizer, pH adjuster, and deionized water.

[0007] Furthermore, each liter of palladium-activated solution comprises the following components: 30–100 mg palladium sulfate, 0.1–1 g carbon nanoparticles, 10–30 mg emulsifier, 5–50 mg stabilizer, and the remainder is deionized water, with the pH value adjusted to 9–11 using a pH adjuster.

[0008] Furthermore, the average particle size of the carbon nanoparticles is 20 nm.

[0009] Furthermore, the emulsifier is selected from one or a combination of two of alkylphenol polyoxyethylene ether, sodium isooctyl sulfate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate.

[0010] Furthermore, the stabilizer is selected from one or a combination of at least two of vitamin C, boric acid, and cinnamaldehyde.

[0011] Furthermore, the pH adjuster is selected from one or a combination of at least two of ammonia, sodium hydroxide, potassium hydroxide, sulfuric acid, and phosphoric acid.

[0012] Another technical solution of the present invention is: a method for preparing the ionic palladium activation solution for chemical copper plating, comprising the following steps: mixing palladium sulfate, carbon nanoparticles and deionized water, stirring for 1 to 2 hours, adding emulsifier and stabilizer, continuing to stir for 1 to 2 hours, adding pH adjuster to adjust the pH value to 9 to 11, continuing to stir for 2 to 3 hours, and letting it stand for 12 to 24 hours to obtain the ionic palladium activation solution.

[0013] The beneficial effects of this invention are as follows: This invention uses carbon nanoparticles instead of traditional complexing agents, resulting in a larger specific surface area, stronger adsorption performance, and more active sites. This allows for the adsorption of more palladium ions and stronger adhesion to the substrate, thus achieving a better activation effect and improving the backlighting effect and adhesion of the electroless copper plating layer. The emulsifier used in this invention reduces surface tension, increases solution activity, and ensures that the carbon nanoparticles are uniformly dispersed in the solution, preventing sedimentation. Detailed Implementation

[0014] The present invention will now be described in detail with reference to specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0015] Example 1:

[0016] An ionic palladium activation solution for electroless copper plating comprises the following components per liter: 50 mg palladium sulfate, 0.1 g carbon nanoparticles, 10 mg alkylphenol polyoxyethylene ether, 50 mg cinnamaldehyde, and the remainder being deionized water. The pH is adjusted to 10 using sodium hydroxide as the pH adjuster. The carbon nanoparticles have an average particle size of 20 nm.

[0017] A method for preparing an ionic palladium activating solution for electroless copper plating includes the following steps:

[0018] Palladium sulfate, carbon nanoparticles, and deionized water were mixed and stirred for 1 hour. Alkylphenol polyoxyethylene ether and cinnamaldehyde were then added. After stirring for another hour, sodium hydroxide was added to adjust the pH to 10. Stirring was continued for 2.5 hours, and the mixture was allowed to stand for 18 hours to obtain an ionic palladium activated solution. The stirring speed was 150 rpm.

[0019] Example 2:

[0020] An ionic palladium activation solution for electroless copper plating comprises the following components per liter: 80 mg palladium sulfate, 0.5 g carbon nanoparticles, 30 mg alkylphenol polyoxyethylene ether, 25 mg cinnamaldehyde, and the remainder being deionized water. The pH is adjusted to 9 using sodium hydroxide. The carbon nanoparticles have an average particle size of 20 nm.

[0021] A method for preparing an ionic palladium activating solution for electroless copper plating includes the following steps:

[0022] Palladium sulfate, carbon nanoparticles, and deionized water were mixed and stirred for 1.5 hours. Alkylphenol polyoxyethylene ether and cinnamaldehyde were added, and stirring was continued for another 1.5 hours. Sodium hydroxide was added to adjust the pH to 9. After stirring for another 3 hours, the mixture was allowed to stand for 24 hours to obtain an ionic palladium activated solution. The stirring speed was 200 rpm.

[0023] Example 3:

[0024] An ionic palladium activation solution for electroless copper plating comprises the following components per liter: 30 mg palladium sulfate, 1 g carbon nanoparticles, 20 mg alkylphenol polyoxyethylene ether, 15 mg cinnamaldehyde, and the remainder being deionized water. The pH adjuster is sodium hydroxide, and the pH value is 11. The carbon nanoparticles have an average particle size of 20 nm.

[0025] A method for preparing an ionic palladium activating solution for electroless copper plating includes the following steps:

[0026] Palladium sulfate, carbon nanoparticles, and deionized water were mixed and stirred for 0.5 hours. Alkylphenol polyoxyethylene ether and cinnamaldehyde were added, and stirring was continued for another 0.5 hours. Sodium hydroxide was added to adjust the pH value to 11. Stirring was continued for another 2 hours, and the mixture was allowed to stand for 12 hours to obtain an ionic palladium activated solution. The stirring speed was 100 rpm.

[0027] Example 4:

[0028] An ionic palladium activation solution for electroless copper plating comprises the following components per liter: 100 mg palladium sulfate, 0.8 g carbon nanoparticles, 15 mg alkylphenol polyoxyethylene ether, 5 mg cinnamaldehyde, and the remainder being deionized water. The pH is adjusted with sodium hydroxide, and the pH value is 10. The carbon nanoparticles have an average particle size of 20 nm.

[0029] A method for preparing an ionic palladium activating solution for electroless copper plating includes the following steps:

[0030] Palladium sulfate, carbon nanoparticles, and deionized water were mixed and stirred for 2 hours. Alkylphenol polyoxyethylene ether and cinnamaldehyde were added, and stirring was continued for another 2 hours. Sodium hydroxide was added to adjust the pH to 10, and stirring was continued for another 3 hours. After standing for 24 hours, an ionized palladium activated solution was obtained. The stirring speed was 180 rpm.

[0031] Comparative Example 1:

[0032] The difference from Example 1 is that carbon nanoparticles are absent in the composition.

[0033] Comparative Example 2:

[0034] The difference from Example 1 is that the alkylphenol polyoxyethylene ether is missing from the composition.

[0035] Reference Example 3:

[0036] The difference from Example 1 is that cinnamaldehyde is missing from the components.

[0037] Comparative example:

[0038] Example 1 of Chinese Patent Application No. CN202010783640.X.

[0039] Experiment 1: Stability Test

[0040] Take 50 mL of the palladium ion activation solution from Examples 1-4, Reference Examples 1-3, and the comparative example, and add them to a 50 mL colorimetric tube. Use a glass tube to introduce air into the bottom of the solution at a flow rate of 20 L / hour. Record the time elapsed from the start of air introduction until the palladium ion activation solution becomes colorless; this is the stabilization time. A longer stabilization time indicates better stability. The test results are shown in Table 1.

[0041] Table 1

[0042]

[0043]

[0044] As shown in Table 1, the stabilization times of Examples 1-4 of the present invention are significantly longer than those of the comparative examples, indicating that the present invention has better stability, with Example 1 exhibiting the longest stabilization time. Some components of the comparative examples 1-3 differ from those of Example 1, and the stabilization times of both comparative examples 1 and 3 are significantly shorter, indicating that both carbon nanoparticles and cinnamaldehyde can effectively improve the stability of the ionic palladium activation solution.

[0045] Activation performance experiment

[0046] Experimental method: The PCB drilled panel was cut into 5cm×5cm samples for chemical copper plating. The process was as follows: hole preparation (50℃, 1 minute); micro-etching (room temperature, 1 minute); pre-immersion (room temperature, 1 minute); activation (50℃, 1 minute, using the ionic palladium activation solution obtained in Examples 1-4, Reference Examples 1-3, and Comparative Examples); reduction (room temperature, 1 minute); chemical copper plating (30℃, 5 minutes).

[0047] Experimental Example 2: Activity Test

[0048] The time elapsed from the moment the sample is immersed in the electroless copper plating solution until the first bubble appears on the sample surface is recorded as the plating start-up time. A shorter start-up time indicates better activity. The test results are shown in Table 2.

[0049] Table 2

[0050]

[0051]

[0052] As can be seen from Table 2, the plating start time of Examples 1-4 of the present invention is shorter than that of the comparative examples, indicating that the ionic palladium activating solution of the present invention has better activity. Some components of the comparative examples 1-3 are different from those of Example 1. The plating start time of the comparative example 1 is significantly increased, indicating that carbon nanoparticles are the main reason for improving the activity of the ionic palladium activating solution.

[0053] Test Example 3: Copper Layer Adhesion Test

[0054] After drying the electroless copper-plated sample, place it flat on a table. Use a cross-cutting tool to draw 100 1mm × 1mm squares on the sample surface. Apply 3M 600 transparent tape smoothly to the squares, pressing it down to ensure complete adhesion without gaps. After 30 seconds, forcefully peel off the tape at a 60° angle and observe the extent of copper plating loss. Record the adhesion level according to the following standards:

[0055] No detachment is recorded as 5B; detachment area of ​​0-5% of the total grid area is recorded as 4B; detachment area of ​​5-15% of the total grid area is recorded as 3B; detachment area of ​​15-35% of the total grid area is recorded as 2B; detachment area of ​​35-65% of the total grid area is recorded as 1B; and detachment area of ​​more than 65% of the total grid area is recorded as 0B. The test results are shown in Table 3.

[0056] Table 3

[0057] Example Adhesion rating Example 1 5B Example 2 5B Example 3 5B Example 4 5B Reference Example 1 4B Reference Example 2 4B Reference Example 3 5B Comparative Example 4B

[0058] As shown in Table 3, the adhesion grades of Examples 1-4 of the present invention are all 5B, which are higher than those of the comparative examples, indicating that the copper plating layer of the present invention has good adhesion. Some components of the comparative examples 1-3 are different from those of Example 1. The adhesion grades of the comparative examples 1 and 2 are both reduced by one grade, indicating that carbon nanoparticles and alkylphenol polyoxyethylene ether can effectively improve the adhesion of the copper plating layer of the ionic palladium activation solution.

[0059] Experiment Example 4: Backlight Effect Test

[0060] After electroless copper plating, the sample was cut and ground using a slicing machine. The slicing hole was ground to half its diameter, and the other side of the slice was ground to 2 mm from the edge of the hole. After grinding, copper shavings and other impurities inside the hole were wiped clean. The inside of the hole was examined under a microscope at 50x magnification. The uniformity of the deposited copper layer inside the hole was detected using the backlight principle. The backlight level was divided into 10 levels, with a higher backlight level indicating a better backlight effect. The test results are shown in Table 4.

[0061] Table 4

[0062] Example Backlight level Example 1 10 Example 2 10 Example 3 10 Example 4 10 Reference Example 1 7 Reference Example 2 8 Reference Example 3 10 Comparative Example 6

[0063] As shown in Table 4, the backlight levels of Examples 1-4 of the present invention are all higher than those of the comparative examples, indicating that the backlight effect of the electroless copper plating of the present invention is better. Some components of the comparative examples 1-3 are different from those of Example 1. The backlight levels of the comparative examples 1 and 2 are lower than those of Examples 1-4, indicating that carbon nanoparticles and alkylphenol polyoxyethylene ether can effectively improve the backlight effect of electroless copper plating of the ionic palladium activation solution.

[0064] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. An ionic palladium activating solution for chemical copper plating, characterized in that: Each liter of palladium-activated solution comprises the following components: 50 mg palladium sulfate, 0.1 g carbon nanoparticles, 10 mg alkylphenol polyoxyethylene ether, 50 mg cinnamaldehyde, and the remainder is deionized water. The pH value is adjusted to 10 with sodium hydroxide as a pH adjuster. The average particle size of the carbon nanoparticles is 20 nm.

2. The method for preparing the ionic palladium activating solution for electroless copper plating according to claim 1, characterized in that, The process includes the following steps: Palladium sulfate, carbon nanoparticles, and deionized water are mixed and stirred for 1-2 hours. Then, alkylphenol polyoxyethylene ether and cinnamaldehyde are added. After stirring for another 1-2 hours, sodium hydroxide is added to adjust the pH to 10. After stirring for another 2-3 hours, the mixture is allowed to stand for 12-24 hours to obtain an ionized palladium activated solution.

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