A palladium-free activated chemical copper deposition process for resin substrates

Abstract

The present invention relates to a palladium-free activated chemical copper deposition process for a resin substrate, the process comprising the following steps: (1) sequentially performing a degreasing treatment and a roughening treatment on the resin substrate to obtain a pretreated resin substrate; (2) immersing the pretreated resin substrate in a pyrrole solution for a period of time, then immersing the resin substrate in a ferric chloride solution and allowing it to stand for a period of time to obtain a substrate with a polypyrrole film, placing the substrate with the polypyrrole film above boiling water so that water vapor fumigates the substrate with the polypyrrole film, and then washing to obtain an activated substrate; (3) immersing the activated substrate in a chemical copper deposition solution to perform chemical copper deposition to obtain a chemical copper plating layer. Compared with the prior art, the present invention uses pyrrole-loaded colloidal iron as a catalytic active site for chemical copper plating to achieve chemical copper deposition on the surface of a non-conductive plastic substrate, replacing the use of precious metals, solving the problem of difficult treatment of waste liquid from precious metal catalytic reactions, and reducing production costs.

Description

Technical Field

[0001] The invention belongs to the technical field of non-metal surface treatment and relates to a palladium-free activated chemical copper deposition process for a resin substrate. Background Art

[0002] With the continuous development of the information society, printed circuit boards (PCBs) have become essential components of modern electronic devices and are developing towards a trend of being light, thin, short and small. As a result, the integration of electronic products is increasing, and the application of high-density interconnected circuit boards and multilayer boards is becoming more and more extensive, and the technical requirements for interconnection between circuit board layers are also increasing. Hole metallization is a key technology for circuit board interconnection, and chemical copper deposition technology has become the mainstream of printed circuit board hole metallization due to its advantages such as excellent coating performance, high bonding strength, wear resistance, corrosion resistance and simple process. The metallization of the surface of traditional plastic substrates, i.e., chemical copper deposition, requires the use of precious metals such as gold and palladium to catalytically activate the surface of the non-conductive substrate, so that the copper ions in the copper deposition solution form a copper metal layer with autocatalytic ability on the substrate surface. The use of precious metals such as gold and palladium also increases production costs, and the waste liquid of the precious metal catalytic reaction is difficult to handle. Therefore, finding a new palladium-free activation method has become a research hotspot in the prior art. Summary of the Invention

[0003] The purpose of the present invention is to provide a palladium-free activated chemical copper deposition process for resin substrates to overcome the following defects in the prior art: chemical copper deposition on the surface of plastic substrates requires the use of precious metals such as gold and palladium to catalytically activate the surface of the non-conductive substrate, which increases production costs, or the waste liquid generated by the precious metal catalytic reaction is difficult to treat.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] A palladium-free activated chemical copper deposition process for a resin substrate comprises the following steps:

[0006] (1) performing degreasing treatment and roughening treatment on the resin substrate in sequence to obtain a pretreated resin substrate;

[0007] (2) immersing the obtained pretreated resin substrate in a pyrrole solution for a period of time, then immersing the resin substrate in a ferric chloride solution, and letting it stand for a period of time to obtain a substrate with a polypyrrole film, placing the substrate with the polypyrrole film above boiling water, allowing water vapor to fumigate the substrate with the polypyrrole film, and then washing to obtain an activated substrate;

[0008] (3) Immersing the activated substrate into a chemical copper plating solution to perform chemical copper plating to obtain a chemical copper plating layer.

[0009] Furthermore, in step (1), the specific process of oil removal is as follows:

[0010] Immerse the resin substrate in alkaline degreasing liquid for a period of time, and then wash it to complete the degreasing process.

[0011] Furthermore, during the soaking process, the temperature of the alkaline degreasing solution is 60°C.

[0012] Furthermore, the soaking time is 5 minutes.

[0013] Furthermore, the components of the alkaline degreasing solution include 30 g / L of sodium hydroxide, 50 g / L of sodium phosphate, 30 g / L of sodium carbonate and 10 ml / L of OP-10.

[0014] Furthermore, in step (1), the specific process of the roughening process is:

[0015] The degreased resin substrate is immersed in an acidic roughening liquid for a period of time and then washed to complete the roughening treatment.

[0016] Furthermore, during the soaking process, the temperature of the acidic roughening liquid is 70°C.

[0017] Furthermore, the soaking time is 3 minutes.

[0018] Furthermore, the components of the acidic coarsening solution include 80 g / L of potassium permanganate and 40 g / L of sodium hydroxide.

[0019] Furthermore, in step (2), the pyrrole solution is an ethanol solution of pyrrole, wherein the volume ratio of pyrrole to ethanol is 1:(1-3).

[0020] Furthermore, in step (2), the soaking time in the pyrrole solution is 1-10 minutes.

[0021] Furthermore, in step (2), the concentration of the ferric chloride solution is 0.5-2 mol / L.

[0022] Furthermore, in step (2), the standing time is 10-30 minutes, and a polypyrrole film is formed on the surface of the resin substrate after standing.

[0023] Furthermore, in step (2), the fumigation time is 0.5-2 hours. After fumigation, the resin substrate is loaded with colloidal iron, and then washed with deionized water for standby use.

[0024] Furthermore, in step (3), the components of the chemical copper precipitation solution include 80 g / L potassium sodium tartrate, 15 g / L sodium hydroxide, 7 g / L sodium carbonate, 8 g / L potassium sodium tartrate, 20 g / L copper sulfate pentahydrate, 2 g / L nickel chloride and 30 ml / L formaldehyde 37%.

[0025] Furthermore, in step (3), the chemical copper deposition time is 1-4 hours. A uniform copper layer with good bonding strength is obtained by chemical copper deposition. The copper layer has good conductivity and can be used as a conductive layer for subsequent copper electroplating.

[0026] The present invention provides a palladium-free activated chemical copper deposition process for a resin substrate, which solves the high cost and pollution problems caused by waste liquid discharge in the prior art of using precious metal palladium as an activation raw material, and at the same time covers a dense and continuous chemical copper plating layer on the surface of the substrate.

[0027] The present invention provides a palladium-free activated chemical copper plating process for resin substrates. This process uses trivalent iron (Fe) instead of traditional precious metal palladium (Pd) to catalytically activate the substrate surface. This eliminates the need for palladium-containing wastewater treatment and reduces production costs. The activation process employed by the present invention produces a high number of evenly distributed surface active sites, resulting in a smooth, dense coating after chemical copper plating.

[0028] By the implementation of the oil removal step of the present invention, the substrate surface is free of oil stains, which is conducive to the contact of subsequent chemical substances with the substrate surface. The implementation of the roughening process can increase the specific surface area of ​​the substrate to an appropriate degree, improve the contact area of ​​subsequent attachments with the substrate, and improve the bonding force of the subsequent film layer with the substrate. The substrate surface after oil removal and roughening process should have the ability to contact with the aqueous solution and the area in which the film layer contacts the substrate. This pre-treatment operation is conducive to the pyrrole molecule fully contacting with the substrate. Since the interaction between the molecule and the substrate is a kinetic process, it is necessary to have enough soaking times to realize the maximum adsorption of the molecule on the substrate surface to reach the effective quantity of subsequent reaction film formation. The film formation of pyrrole needs to be completed by the oxidation of ferric iron. Therefore, the concentration and time of ferric chloride determine the oxidation rate and oxidation degree of pyrrole oxide film. Only the appropriate time can allow pyrrole to complete effective oxidation and become a polypyrrole film with suitable molecular chain length to adsorb and accommodate ferric ions. The process of water molecule fumigation realizes the conversion of ferric iron colloidal state, making it more securely fixed in the framework of polypyrrole long-chain molecules, becoming the catalyst of subsequent chemical copper plating reaction. Since the process of chemical copper plating has the process of nucleation and nucleus growth, sufficient chemical copper deposition time is conducive to the formation and growth of copper nuclei, thereby forming a copper film with a continuous effect. Therefore, sufficient chemical copper deposition time is necessary, but excessive chemical copper deposition time can lead to excessive growth of copper, excessive grain size, rough coating, and even excessive coating thickness. The experimental parameters provided by the present invention achieve the purpose of uniform copper deposition and also achieve the purpose of obtaining an effectively uniform chemical copper deposition surface.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) The present invention directly uses pyrrole-loaded colloidal iron as the catalytic active site for chemical copper plating, thereby achieving chemical copper deposition on the surface of a non-conductive plastic substrate, replacing the use of precious metals such as palladium and silver, solving the problem of difficult treatment of waste liquid from precious metal catalytic reactions, and reducing production costs.

[0031] (2) The activation process provided by the present invention is stable in operation and does not suffer from process operation difficulties such as instability of the sensitizing solution (stannous ions). The activation process is stable and reliable, eliminating the problem of activation solution failure, improving process stability, facilitating production control, and helping to ensure product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a scanning electron microscope image of the surface morphology of the epoxy resin substrate after electroless copper deposition in Example 1;

[0033] Figure 2 This is the X-ray electron spectrum test diagram of copper deposition in Example 1;

[0034] Figure 3 This is a scanning electron microscope image of the surface morphology of the epoxy resin substrate after chemical copper deposition in Example 3. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0036] In the following examples, unless otherwise specified, the raw materials or processing techniques used are conventional commercially available raw materials or conventional processing techniques in the art.

[0037] Example 1:

[0038] 1) Degreasing treatment was performed on the FR-4 glass fiber epoxy resin board. The degreasing solution formula was as follows: sodium hydroxide 30g / L, sodium phosphate 50g / L, sodium carbonate 30g / L, OP-10 10ml / L. The epoxy resin substrate was immersed in the degreasing solution at 60°C for 5 minutes.

[0039] 2) The substrate was subjected to a roughening treatment. The formula of the roughening solution was: 80 g / L potassium permanganate and 40 g / L sodium hydroxide. The epoxy resin substrate was immersed in the roughening solution at a temperature of 70° C. for 3 minutes.

[0040] 3) Activate the substrate: Prepare a pyrrole solution (pyrrole: ethanol in a 1:2 volume ratio) and a 1 mol / L ferric chloride solution. Place the substrate in the pyrrole solution and let it sit for 5 minutes. Then, place it in the ferric chloride solution and let it sit for 30 minutes. After 30 minutes, remove the substrate and place it over boiling water vapor for 30 minutes. Then, rinse the substrate in deionized water.

[0041] 4) The substrate after the third cleaning step was subjected to electroless copper deposition. The electroless copper deposition solution contained 80 g / L potassium sodium tartrate, 15 g / L sodium hydroxide, 7 g / L sodium carbonate, 8 g / L potassium sodium tartrate, 20 g / L copper sulfate pentahydrate, 2 g / L nickel chloride, and 30 ml / L 37% formaldehyde. The electroless copper deposition process lasted 4 hours, resulting in a uniform red copper layer on the substrate. Figure 1 The scanning electron microscope image of the epoxy resin substrate after chemical copper deposition in Example 1 is shown in FIG. Figure 1 It can be seen that the copper unit cells of the chemical copper deposition are uniformly attached. Figure 2 This is the X-ray electron spectrum test diagram of copper deposition, which confirms that the obtained material is a copper plating layer.

[0042] Example 2:

[0043] 1) Degreasing treatment was performed on the FR-4 glass fiber epoxy resin board. The degreasing solution formula was as follows: sodium hydroxide 30g / L, sodium phosphate 50g / L, sodium carbonate 30g / L, OP-10 10ml / L. The epoxy resin substrate was immersed in the degreasing solution at 60°C for 5 minutes.

[0044] 2) The substrate was subjected to a roughening treatment. The formula of the roughening solution was: 80 g / L potassium permanganate and 40 g / L sodium hydroxide. The epoxy resin substrate was immersed in the roughening solution at a temperature of 70° C. for 3 minutes.

[0045] 3) Activate the substrate: Prepare a pyrrole solution with a 1:1 volume ratio of pyrrole to ethanol and a 0.5 mol / L ferric chloride solution. Place the substrate in the pyrrole solution and let it sit for 1 minute. Then, place it in the ferric chloride solution and let it sit for 20 minutes. After 20 minutes, remove the substrate and place it over boiling water vapor for 60 minutes. Then, rinse the substrate in deionized water.

[0046] 4) The substrate after the third cleaning step was subjected to electroless copper deposition. The electroless copper deposition solution contained 80 g / L potassium sodium tartrate, 15 g / L sodium hydroxide, 7 g / L sodium carbonate, 8 g / L potassium sodium tartrate, 20 g / L copper sulfate pentahydrate, 2 g / L nickel chloride, and 30 ml / L 37% formaldehyde. The electroless copper deposition process lasted 2 hours, resulting in a uniform red copper layer on the substrate.

[0047] Example 3:

[0048] 1) Degreasing treatment was performed on the FR-4 glass fiber epoxy resin board. The degreasing solution formula was as follows: sodium hydroxide 30g / L, sodium phosphate 50g / L, sodium carbonate 30g / L, OP-10 10ml / L. The epoxy resin substrate was immersed in the degreasing solution at 60°C for 5 minutes.

[0049] 2) The substrate is subjected to a roughening treatment. The formula of the roughening solution is: 80 g / L potassium permanganate and 40 g / L sodium hydroxide. The substrate is immersed in the roughening solution at an immersion temperature of 70° C. for 3 minutes.

[0050] 3) Activate the substrate: Prepare a pyrrole solution with a 1:3 volume ratio of pyrrole to ethanol and a 2 mol / L ferric chloride solution. Place the substrate in the pyrrole solution and let it sit for 10 minutes. Then, place the substrate in the ferric chloride solution and let it sit for 10 minutes. After 10 minutes, remove the substrate and place it over boiling water vapor for 2 hours. Then, rinse the substrate in deionized water.

[0051] 4) The substrate after the third step of cleaning is subjected to chemical copper deposition. The chemical copper deposition solution contains 80g / L potassium sodium tartrate, 15g / L sodium hydroxide, 7g / L sodium carbonate, 8g / L potassium sodium tartrate, 20g / L copper sulfate pentahydrate, 2g / L nickel chloride, and 30ml / L 37% formaldehyde. The chemical copper deposition time is 1 hour, and a uniform red copper layer is obtained on the substrate. Figure 3 As shown, the unit cells on the substrate surface are stacked.

[0052] Example 4:

[0053] 1) Degreasing treatment was performed on the FR-4 glass fiber epoxy resin board. The degreasing solution formula was as follows: sodium hydroxide 30g / L, sodium phosphate 50g / L, sodium carbonate 30g / L, OP-10 10ml / L. The epoxy resin substrate was immersed in the degreasing solution at 60°C for 5 minutes.

[0054] 2) The substrate is subjected to a roughening treatment. The formula of the roughening solution is: 80 g / L potassium permanganate and 40 g / L sodium hydroxide. The substrate is immersed in the roughening solution at an immersion temperature of 70° C. for 3 minutes.

[0055] 3) Activate the substrate: Prepare a pyrrole solution with a 1:3 volume ratio of pyrrole to ethanol and a 2 mol / L ferric chloride solution. Place the substrate in the pyrrole solution and let it sit for 10 minutes. Then, place the substrate in the ferric chloride solution and let it sit for 10 minutes. After 10 minutes, remove the substrate and place it over boiling water vapor for 2 hours. Then, rinse the substrate in deionized water.

[0056] 4) The substrate after the third cleaning step was subjected to electroless copper deposition. The electroless copper deposition solution contained 80g / L potassium sodium tartrate, 15g / L sodium hydroxide, 7g / L sodium carbonate, 8g / L potassium sodium tartrate, 20g / L copper sulfate pentahydrate, 2g / L nickel chloride, and 30ml / L 37% formaldehyde. The electroless copper deposition process lasted 4 hours, resulting in a uniform red copper layer on the substrate, with more pronounced unit cell stacking on the substrate surface.

[0057] Comparative Example 1:

[0058] Compared with Example 1, most of the steps are the same, except that the soaking step in the pyrrole solution is omitted in this comparative example.

[0059] 1) Degreasing treatment was performed on the FR-4 glass fiber epoxy resin board. The degreasing solution formula was as follows: sodium hydroxide 30g / L, sodium phosphate 50g / L, sodium carbonate 30g / L, OP-10 10ml / L. The epoxy resin substrate was immersed in the degreasing solution at 60°C for 5 minutes.

[0060] 2) The substrate was subjected to a roughening treatment. The formula of the roughening solution was: 80 g / L potassium permanganate and 40 g / L sodium hydroxide. The epoxy resin substrate was immersed in the roughening solution at a temperature of 70° C. for 3 minutes.

[0061] 3) Activate the substrate: Prepare a 1 mol / L ferric chloride solution. Place the substrate in the ferric chloride solution and let it sit for 30 minutes. After 30 minutes, remove the substrate and place it over boiling water vapor for 30 minutes. Then rinse the substrate in deionized water.

[0062] 4) The substrate after the third cleaning step was subjected to electroless copper deposition. The electroless copper deposition solution contained 80 g / L potassium sodium tartrate, 15 g / L sodium hydroxide, 7 g / L sodium carbonate, 8 g / L potassium sodium tartrate, 20 g / L copper sulfate pentahydrate, 2 g / L nickel chloride, and 30 ml / L 37% formaldehyde. The electroless copper deposition lasted 4 hours, and sporadic red spots appeared on the substrate surface, with no uniform red copper layer formed.

[0063] Comparative Example 2:

[0064] Compared with Example 2, most of the steps are the same, except that the steam fumigation step is omitted in this comparative example.

[0065] 1) Degreasing treatment was performed on the FR-4 glass fiber epoxy resin board. The degreasing solution formula was as follows: sodium hydroxide 30g / L, sodium phosphate 50g / L, sodium carbonate 30g / L, OP-10 10ml / L. The epoxy resin substrate was immersed in the degreasing solution at 60°C for 5 minutes.

[0066] 2) The substrate was subjected to a roughening treatment. The formula of the roughening solution was: 80 g / L potassium permanganate and 40 g / L sodium hydroxide. The epoxy resin substrate was immersed in the roughening solution at a temperature of 70° C. for 3 minutes.

[0067] 3) Activate the substrate: Prepare a pyrrole solution (pyrrole: ethanol in a 1:1 volume ratio) and a 0.5 mol / L ferric chloride solution. Place the substrate in the pyrrole solution and let it sit for 1 minute. Then, place the substrate in the ferric chloride solution and let it sit for 20 minutes. After 20 minutes, rinse the substrate in deionized water.

[0068] 4) The substrate after the third cleaning step was subjected to electroless copper plating. The electroless copper plating solution contained 80 g / L potassium sodium tartrate, 15 g / L sodium hydroxide, 7 g / L sodium carbonate, 8 g / L potassium sodium tartrate, 20 g / L copper sulfate pentahydrate, 2 g / L nickel chloride, and 30 ml / L 37% formaldehyde. The electroless copper plating time was 2 hours, and no uniform red copper layer was formed on the substrate surface.

[0069] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A palladium-free activated chemical copper deposition process for resin substrates, characterized in that: The following steps are involved: (1) performing degreasing treatment and roughening treatment on the resin substrate in sequence to obtain a pretreated resin substrate; (2) immersing the obtained pretreated resin substrate in a pyrrole solution for a period of time, then immersing the resin substrate in a ferric chloride solution, and letting it stand for a period of time to obtain a substrate with a polypyrrole film, placing the substrate with the polypyrrole film above boiling water, allowing water vapor to fumigate the substrate with the polypyrrole film, and then washing to obtain an activated substrate; (3) immersing the activated substrate into a chemical copper plating solution to perform chemical copper plating to obtain a chemical copper plating layer; In step (2), the pyrrole solution is an ethanol solution of pyrrole, wherein the volume ratio of pyrrole to ethanol is 1:(1-3); In step (2), the soaking time in the pyrrole solution is 1-10 minutes; In step (2), the concentration of the ferric chloride solution is 0.5-2 mol / L; In step (2), the standing time is 10-30 minutes; In step (2), the fumigation time is 0.5-2h; In step (3), the components of the chemical copper precipitation solution include 80 g / L potassium sodium tartrate, 15 g / L sodium hydroxide, 7 g / L sodium carbonate, 8 g / L potassium sodium tartrate, 20 g / L copper sulfate pentahydrate, 2 g / L nickel chloride and 30 ml / L formaldehyde 37%; In step (3), the chemical copper deposition time is 1-4 hours.

2. A palladium-free activated chemical copper deposition process for resin substrates according to claim 1, characterized in that: In step (1), the specific process of oil removal is as follows: Immerse the resin substrate in alkaline degreasing liquid for a period of time, and then wash it to complete the degreasing process.

3. The process for palladium-free activated chemical copper deposition on a resin substrate according to claim 1, characterized in that: In step (1), the specific process of the roughening treatment is: The degreased resin substrate is immersed in an acidic roughening liquid for a period of time and then washed to complete the roughening treatment.

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