CN114016098A

CN114016098A - Copper-clad plate electroplating Ni-Co-Ce film plating solution for PCB and film preparation method

Info

Publication number: CN114016098A
Application number: CN202111226368.6A
Authority: CN
Inventors: 王守绪; 李嘉琦; 何为; 陈苑明; 周国云; 王翀; 吴宜骏; 倪修任; 张东明
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2021-10-21
Filing date: 2021-10-21
Publication date: 2022-02-08
Anticipated expiration: 2041-10-21
Also published as: CN114016098B

Abstract

The invention provides a plating solution formula and a preparation method for electrodepositing a Ni-Co-Ce alloy film on the copper surface of a printed circuit copper-clad plate, and a method for manufacturing the Ni-Co-Ce alloy film on the surface of the copper-clad plate by using the plating solution. The plating solution formula comprises: 0.03-0.05 mol/L of nickel chloride, 0.03-0.05 mol/L of cobalt sulfate, 0.1-0.2 mol/L of conductive additive, 0.1-0.2 mol/L of buffering agent, 0.1-0.2 mol/L of electroplating additive, 0.005-0.03 mol/L of ceric sulfate, deionized water and the like, and the Ni-Co-Ce alloy film obtained by electroplating can be used for protecting electronic circuits of multilayer printed circuit boards, improving interlayer binding force, improving high-frequency signal integrity and the like. Meanwhile, the formula of the plating solution is simple and convenient to prepare, the printed circuit substrate is not corroded, the compatibility of the electroplating process and equipment and the existing conditions in the field of printed circuit manufacturing is good, and the technical transformation investment and the product manufacturing cost are greatly reduced.

Description

Copper-clad plate electroplating Ni-Co-Ce film plating solution for PCB and film preparation method

Technical Field

The invention belongs to the technical field of surface modification of printed circuit boards, and particularly relates to a Ni-Co-Ce film electroplating solution for a copper-clad plate for a PCB (printed circuit board) and a film preparation method.

Background

The printed circuit board is a basic component for manufacturing electronic equipment, the FR-4 copper-clad plate is one of the substrate materials with the largest use amount at present, and the surface protection treatment of the printed circuit board is one of the important processes in the field of printed circuit board manufacturing in order to avoid the problems of oxidation, pollution and the like of the printed circuit board before components are packaged.

The surface treatment techniques commonly used in the industry at present include hot air leveling, chemical immersion of nickel gold/silver/tin, coating of organic protective film, electroplating of tin/nickel gold and the like. For example, Gaoban is introduced in the treatise on the research and application of the tin plating technology for the copper surface of the printed circuit board, and the tin plating layer prepared by adopting the technology can improve the etching quality of an electronic circuit and the welding reliability of components and parts, enhance the interlayer bonding force of a multilayer board and the like. The method for improving the surface performance of the prepared circuit board by adopting the nickel electroplating layer in the field of printed circuits is based on the fact that a nickel simple substance has better corrosion resistance and high temperature resistance, a nickel plating layer can be easily passivated in the air and can effectively play a role in protecting copper electronic circuits by the characteristics of slow action with common strong base, strong acid, hydrochloric acid and sulfuric acid, and the like, and the patent 'a method for electroplating nickel on the surface of the printed circuit board by using ionic liquid' (application publication No. CN105018975A) realizes the preparation of the nickel electroplating layer on the surface of the printed circuit board by using the ionic liquid as electrolyte, but a pure nickel plating layer on the surface of copper has the defects of poor stability, easy peeling of the plating layer, non-bright surface and the like. Therefore, the development of the technique for manufacturing the alloy coating on the surface of the printed circuit board becomes an industrial research hotspot. The patent 'production process of nickel-cerium alloy plated annealed copper wire' (publication number CN101556846A) proposes a production process of nickel-cerium alloy plated annealed copper wire on the surface of copper wire, and the obtained nickel-cerium alloy plated coating has the characteristics of good adhesiveness, good toughness, excellent extensibility and the like on the surface of annealed copper wire, and is suitable for manufacturing aviation wire and cable and special installation conductive cores; the patent 'a printed circuit board electroplating nickel gold technology' (application publication No. CN101835346A) adopts the design of electroplating connecting line to conduct the electric brush position on the edge of the printed circuit board technology and the non-edge region to be electroplated with nickel and gold, thus realizing the electroplating of nickel and gold on the non-edge region on the printed circuit board, ensuring the reliability of the electroplating nickel layer on the printed circuit board, effectively reducing the waste of precious metal nickel and gold resources, reducing the cost and being more environment-friendly; the patent 'plating solution for electroplating a nickel-cobalt-iron alloy layer on a crystallizer copper plate' (application publication No. CN105442002A) discloses a plating solution for electroplating a nickel-cobalt-iron alloy layer on a crystallizer copper plate, which comprises 240g/L of nickel sulfate 220-.

In order to solve the corrosion resistance problem of the copper foil, some copper foil manufacturers develop ternary and quaternary alloy corrosion resistant processes of metals such as zinc, nickel, cobalt, tin, iron, arsenic, tungsten and the like, so that the corrosion resistance of the copper foil is greatly improved, but the processes are complex, the process parameter range is narrow, and the problems of difficult operation, high cost, difficult plating solution recovery and wastewater treatment, environmental protection and the like exist. Based on the cerium atom structure with 4f unfilled electrons and small electronegativity, the copper-based electroplating technology added with cerium salt has attracted attention. The patent 'surface treating agent for improving the corrosion resistance of electrolytic copper foil' (application publication No. CN 111304709A) realizes the improvement of the corrosion resistance of the copper foil by electroplating the surface of the copper foil to form a uniform and fine tin-zinc-cerium ternary alloy composite plating layer, and the hydrochloric acid cracking resistance of the copper foil can be realized to be less than 2%; the patent 'a rare earth cerium-copper-zinc alloy electroplating solution and an electroplating method thereof' (application publication number CN105483772A) discloses a rare earth cerium-copper-zinc alloy electroplating solution and an electroplating method thereof, wherein the electroplating solution comprises 10-80g/L of copper sulfate, 4-60g/L of zinc sulfate, 0.1-1g/L of dioxide decorations, 4-40g/L of amino acid, 100 g/L of sodium pyrophosphate and 200g/L of brightener, and a cerium-copper-zinc alloy coating electroplated by using the electroplating solution has the advantages of beautiful color, compactness and corrosion resistance. The document results in further improvement of the stability of electronic circuits in the environment, but the core problems of interlayer bonding force, electromagnetic compatibility and the like in the manufacture of multilayer printed circuit boards are not involved. The existing interlayer bonding force is mostly improved by treatments such as browning, and the treatment means can improve the roughness of the copper surface and increase the insertion loss. With the development of high density and multi-layer circuit boards, especially the development of high frequency signal transmission of electronic products in recent years, the production of metal coatings on copper-based surfaces of printed circuits not only needs to consider the improvement of corrosion resistance and wear resistance of copper electronic circuits, but also needs to consider the improvement of interlayer bonding force of multilayer boards, and the problems of signal loss, electromagnetic interference and the like of protected electronic circuits during high frequency signal transmission. In addition, in practice, it is found that some alloy layers obtained by electroplating are not fine and uniform enough in crystallization, and the corrosion resistance of the alloy layers does not achieve an ideal effect, so that the edge corrosion phenomenon occurs when a copper foil circuit board is etched on a high-precision circuit, and the quality of a manufactured finished product is seriously affected.

Therefore, developing a new plating solution formula and realizing good protection of the protective coating of the copper-clad plate of the printed circuit become research hotspots.

Disclosure of Invention

Aiming at the problems of weak bonding force between a protective coating prepared by the prior coating formula and a printed circuit copper-clad plate, influence on signal transmission and the like in the prior art, the invention aims to provide a coating solution for electroplating a Ni-Co-Ce film on the copper-clad plate for a PCB and a film preparation method. According to the formula of the plating solution, cerium ions are added into the plating solution to increase the cathode polarization effect in the copper surface electroplating process of the copper-clad plate, the electrodeposition speed of nickel ions and cobalt ions on the copper surface is controlled, the regulation and control of the composition, the surface compactness and other properties of the prepared Ni-Co-Ce alloy are realized, the peel strength of high polymer materials such as epoxy resin on the surface of the prepared alloy layer is effectively improved, and the improvement of the interlayer bonding force of the multilayer printed circuit board is facilitated. In addition, the compact alloy plating layer is very beneficial to high-frequency electronic signal transmission, so that the interlayer bonding force is improved and the insertion loss of high-frequency transmission signals is reduced in the manufacturing process of the multilayer high-frequency printed circuit board. Meanwhile, the formula of the plating solution does not contain precious metals such as gold and the like and highly toxic substances and the like, the plating solution is simple and convenient to prepare and does not corrode organic materials of the printed circuit substrate, equipment for manufacturing an alloy layer on the surface of the copper-clad plate by using the plating solution has better compatibility with the existing electroplating equipment in the field of printed circuit manufacturing, the technical transformation investment is less, and the production and manufacturing cost is low.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a plating solution for electroplating a Ni-Co-Ce film on a copper-clad plate for a PCB comprises the following components: 0.03-0.05 mol/L of nickel chloride, 0.03-0.05 mol/L of cobalt sulfate, 0.1-0.2 mol/L of conductive additive, 0.1-0.2 mol/L of pH buffering agent, 0.1-0.2 mol/L of electroplating additive, 0.005-0.03 mol/L of ceric sulfate and deionized water.

Further, the conductive additive may be sodium chloride, sodium sulfate, potassium chloride or potassium sulfate, preferably sodium chloride.

Further, the pH buffer may be a weak acid, which is acetic acid, citric acid, boric acid, or the like, a weak acid salt, which is oxalate, tartrate, phosphate, or the like, preferably boric acid, or an ammonium salt.

Further, the plating additive is sodium lauryl sulfate, thiourea, sodium polydithio-dipropyl sulfonate (SPS), and the like, preferably thiourea and sodium polydithio-dipropyl sulfonate (SPS).

The method for preparing the Ni-Co-Ce ternary alloy film based on the plating solution comprises the following steps:

step 1, preparing plating solution: putting a certain amount of deionized water into a container, sequentially adding a pH buffering agent, a conductive additive, a nickel salt, a cobalt salt, an electroplating additive and a rare earth cerium compound under continuous stirring, then adjusting the pH value of the system to a preset pH value by using dilute sulfuric acid or a dilute NaOH solution, and finally performing constant volume by using the deionized water with the preset pH value to obtain a plating solution; wherein, nickel chloride is 0.03-0.05 mol/L, cobalt sulfate is 0.03-0.05 mol/L, ceric sulfate is 0.005-0.03 mol/L, conductive additive is 0.1-0.2 mol/L, pH buffer agent is 0.1-0.2 mol/L, electroplating additive is 0.1-0.2 mol/L, and pH value is 5-7;

step 2, pretreatment of the plated part: removing surface stains such as surface oxide layers and dirt from a printed circuit copper-clad plate to be electroplated by using a brush plate, then soaking and washing the printed circuit copper-clad plate in 5% dilute sulfuric acid for 1-10 min, taking out the printed circuit copper-clad plate, washing the printed circuit copper-clad plate by using deionized water, carrying out microetching treatment by using a mixed solution of 5% dilute sulfuric acid and 5% sodium persulfate for 1-50 s, finally cleaning the printed circuit copper-clad plate by using deionized water, and blow-drying the cleaned printed circuit copper-clad plate for later use;

step 3, preparing the Ni-Co-Ce alloy film: putting the pretreated plating piece into an electroplating bath, preparing the alloy film by adopting a constant potential deposition method at room temperature, keeping the pH value of the solution at 5-7 in the electroplating process, and keeping the electroplating time at 10-40 min and the current density at 15-20 mA/cm²And continuously stirring the electroplating solution at the temperature of 15-40 ℃ in the electroplating process to reduce concentration polarization, thus preparing the Ni-Co-Ce alloy film covering the copper surface of the copper-clad plate.

The invention also provides the application of the Ni-Co-Ce alloy film obtained by the method as a surface protective layer of an electronic circuit in the manufacture of a printed board, and the Ni-Co-Ce alloy film can be used for manufacturing an anti-corrosion layer, an anti-corrosion layer and the like.

Due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. the Ni-Co-Ce alloy plating layer can be obtained by adding cerium salt into the plating solution, the electrodeposition speed of nickel and cobalt on the surface of the copper-clad plate and the microstructure of the plating layer are changed by the characteristic adsorption of cerium ions on the copper surface, the formation of the plating layer with compact surface and good binding force with matrix copper is facilitated, and the technical problem of poor binding force of the plating layer in the prior art is broken through. The existence of the simple substance cerium in the plating layer can not only improve the binding force between the alloy plating layer and the substrate copper surface, but also improve the corrosion resistance of the prepared alloy plating layer because the active metal cerium generates passivation in the air. In addition, under the condition that the surface roughness of an electronic circuit and a coating is not increased, the wettability (or affinity) of an alloy layer to organic materials special for manufacturing printed circuit boards such as epoxy resin is increased by using an extremely thin layer of high-oxidation-state substances generated by elementary cerium passivation, and the peel strength of the organic resin materials for manufacturing the printed circuit on the surface of the coating is effectively improved, so that the three aims of electronic circuit protection, multi-layer board interlayer bonding force improvement and high-frequency signal transmission insertion loss reduction (signal integrity improvement) are fulfilled.

2. The plating solution provided by the invention does not contain precious metals such as Au and the like, cyanide and the like, is easy to obtain the plating solution raw materials, has good stability, is convenient to maintain, saves the cost and is environment-friendly. Meanwhile, the plating solution provided by the invention belongs to a weak acid system, does not generate a corrosion effect with a substrate organic material of a copper-clad plate, simplifies the preparation operation of an alloy film, reduces the controllability of the process and the complexity of the process, simplifies the requirements of equipment and process, and can better realize large-scale application.

3. The Ni-Co-Ce ternary alloy film prepared based on the plating solution formula has excellent electromagnetic performance and cerium specific chemical performance, and can realize better compatibility of interlayer bonding force and signal integrity improvement in the manufacture of multilayer high-frequency printed circuit boards. The bonding force between the plating layer and the copper-clad plate substrate is as high as 57.47N/cm²And is far higher than the technical standard of the industry.

Drawings

FIG. 1 is an SEM image of a copper substrate prior to alloy plating after pretreatment in accordance with the present invention.

FIG. 2 is an SEM image of the copper-based Ni-Co-Ce alloy film prepared by the invention.

FIG. 3 is an EDS diagram of the copper-based Ni-Co-Ce alloy film prepared by the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the following embodiments and accompanying drawings.

The invention provides electroplating solution prepared by electroplating ternary Ni-Co-Ce alloy on the copper surface of a copper-clad plate of a printed circuit and a method for preparing an alloy layer by using the electroplating solution, according to the characteristic that nickel-cobalt alloy is a typical magnetic metal alloy and has a synergistic effect and the characteristic that cerium ions are adsorbed on the surface of copper and contribute to negative displacement of the deposition potential of nickel and cobalt cathodes. The nickel source of the electroplating solution is selected from nickel chloride, the cobalt source is selected from cobalt sulfate, the cerium source is selected from cerium sulfate with the oxidation number of +4, and then a conductive substance containing chloride ions and sulfate ions is added to control the ratio of the concentration of the chloride ions to the concentration of the sulfate ions in the solution, so that the aim of controlling the conductivity of the electroplating solution system is fulfilled, and the Ni-Co-Ce sulfate-chloride electroplating solution system for electroplating the copper surface of the copper-clad plate has the advantages of high deposition speed, low coating stress and the like, so that the coating quality can be improved, and the electroplating efficiency can be improved.

The substrate of the electrodeposited Ni-Co-Ce alloy film is selected to be a copper-clad plate for manufacturing the printed circuit board. Firstly, the printed circuit copper-clad plate needs to be cleaned in advance, so that the copper surface of a plated part is clean. In the electroplating process, the printed circuit copper-clad plate after pretreatment is used as a negative electrode and placed in a plating solution, metal ions in the plating solution are deposited on the surface of a matrix through electroplating, an alloy plating layer is formed on the copper surface of the copper-clad plate, and EDS proves that the alloy becomes a Ni-Co-Ce alloy film.

If the copper clad laminate is a flexible copper clad laminate, reinforcement treatment needs to be carried out in advance.

Example 1

A method for electroplating a Ni-Co-Ce film on a copper-clad plate for a PCB comprises the following steps:

step 1: preparing a plating solution: putting a certain amount of deionized water into a container, sequentially adding boric acid, sodium chloride, nickel chloride, cobalt sulfate, thiourea, sodium polydithio-dipropyl sulfonate and ceric sulfate under continuous stirring, fully stirring to dissolve all components, then adjusting the pH value of the system to 6 by using dilute sulfuric acid or dilute NaOH solution, and finally performing constant volume by using the deionized water with the pH value of 6 to obtain a plating solution; wherein, nickel chloride is 0.04mol/L, cobalt sulfate is 0.035mol/L, sodium chloride is 0.1mol/L, boric acid is 0.2mol/L, thiourea is 0.1mol/L, sodium polydithio-dipropyl sulfonate is 0.1mol/L, and ceric sulfate is 0.005 mol/L;

step 2: pretreatment of a plated part: cutting the FR-4 copper-clad plate into a size of 1cm multiplied by 1cm, removing surface stains such as surface oxidation layers, dirt and the like by using a brush plate, then washing with tap water, airing, soaking in 5% dilute sulfuric acid for 5min, taking out, washing, drying, then carrying out micro-etching for 5 seconds by using a mixed solution of 5% dilute sulfuric acid and 5% sodium persulfate, finally cleaning with deionized water, and drying for later use;

and step 3: preparing a Ni-Co-Ce ternary alloy film: preparing an alloy film by using an AUT85266 electrochemical workstation and adopting a constant potential deposition method, electroplating in the plating solution prepared in the step 1 by using the copper-clad plate cleaned in the step 2 as a working electrode, a pure platinum electrode as a counter electrode and a saturated potassium sulfate electrode as a reference electrode, keeping the temperature at 25 ℃, the pH value of the solution at 6, the electroplating time at 5min and the current density at 20mA/cm in the electroplating process²(ii) a And continuously stirring in the electroplating process to reduce concentration polarization, thus preparing the required Ni-Co-Ce ternary alloy film.

The peel strength of the resin layer on the surface of the copper-clad plate prepared by the embodiment is 47.02N/cm²。

Example 2

A Ni-Co-Ce ternary alloy film was prepared according to the procedure of example 1, with only the bath formulation of step 1 adjusted to: 0.04mol/L of nickel chloride, 0.035mol/L of cobalt sulfate, 0.1mol/L of sodium chloride, 0.2mol/L of boric acid, 0.1mol/L of thiourea, 0.1mol/L of sodium polydithio-dipropyl sulfonate, 0.01mol/L of ceric sulfate, pH value of 6 and other steps are not changed.

The peel strength of the resin layer on the surface of the copper-clad plate prepared by the embodiment is 49.21N/cm²。

Example 3

A Ni-Co-Ce ternary alloy film was prepared according to the procedure of example 1, with only the bath formulation of step 1 adjusted to: 0.04mol/L of nickel chloride, 0.035mol/L of cobalt sulfate, 0.1mol/L of sodium chloride, 0.2mol/L of boric acid, 0.1mol/L of thiourea, 0.1mol/L of sodium polydithio-dipropyl sulfonate, 0.02mol/L of ceric sulfate, pH value of 6 and other steps are not changed.

The peel strength of the resin layer on the surface of the copper-clad plate prepared by the embodiment is 57.47N/cm²。

FIG. 1 is an SEM image of a copper substrate prior to alloy plating after pretreatment in accordance with the present invention. As can be seen from the figure, the surface of the substrate is very rough with many faults and gaps.

FIG. 2 is an SEM image of the copper-based Ni-Co-Ce alloy film prepared by the invention. As can be seen from the figure, the alloy film prepared by the method has the advantages of smooth and compact surface, refined crystal grains, reduced granular sensation, improved coating brightness, easily changed surface pH value and chemical properties, and the surface modification is favorable for improving the corrosion resistance of the alloy layer and reducing the surface roughness.

FIG. 3 is an EDS diagram of the copper-based Ni-Co-Ce alloy film prepared by the invention. As can be seen from the figure, the effective components of the alloy film prepared by the method comprise Co, Ni and Ce, wherein the ratio of Co is 41.45%, the ratio of Ni is 50.13% and the ratio of Ce is 8.42%.

While the invention has been described with reference to specific embodiments, any feature disclosed in this specification may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise; all of the disclosed features, or all of the method or process steps, may be combined in any combination, except mutually exclusive features and/or steps.

Claims

1. The plating solution for electroplating the Ni-Co-Ce film on the copper-clad plate for the PCB is characterized by comprising the following components: 0.03-0.05 mol/L of nickel chloride, 0.03-0.05 mol/L of cobalt sulfate, 0.1-0.2 mol/L of conductive additives, 0.1-0.2 mol/L of pH buffering agents, 0.1-0.2 mol/L of electroplating additives, 0.005-0.03 mol/L of ceric sulfate and deionized water;

the plating solution is prepared according to the following preparation process: and (2) putting a certain amount of deionized water into a container, sequentially adding a pH buffering agent, a conductive additive, nickel chloride, cobalt sulfate, an electroplating additive and a ceric sulfate compound under continuous stirring, then adding an acid solution or an alkali solution to adjust the pH value of the system to 5-7, and finally performing constant volume by using the deionized water with the same pH value as the system to obtain the required plating solution.

2. The plating solution of claim 1, wherein the conductive additive is sodium chloride, sodium sulfate, potassium chloride, or potassium sulfate.

3. The plating solution of claim 1, wherein the pH buffering agent is a weak acid, a weak acid salt, or an ammonium salt.

4. The plating solution of claim 3, wherein the weak acid is acetic acid, citric acid, or boric acid and the salt of the weak acid is an oxalate, tartrate, or phosphate.

5. The plating solution of claim 1, wherein the plating additives are sodium dodecyl sulfate, thiourea, and sodium polydithio dipropane sulfonate.

6. A preparation method of a Ni-Co-Ce alloy film electroplated on a copper-clad plate for a PCB is characterized by comprising the following steps:

step 1: copper matrix pretreatment: removing surface stains on the printed circuit copper-clad plate to be electroplated, soaking and washing the printed circuit copper-clad plate in 5% dilute sulfuric acid for 1-10 min, taking out the printed circuit copper-clad plate, washing the printed circuit copper-clad plate with deionized water, carrying out microetching treatment on the copper-clad plate with a mixed solution of 5% dilute sulfuric acid and 5% sodium persulfate for 1-50 s, finally cleaning the copper-clad plate with deionized water, and blow-drying the copper-clad plate for later use;

step 2: preparing a Ni-Co-Ce ternary alloy film: taking the printed circuit copper-clad plate to be electroplated cleaned in the step 1 as a cathode and a platinum or titanium net as an anode, and electroplating the copper surface of the copper-clad plate at room temperature by adopting a constant potential deposition method to prepare an alloy film, wherein the electroplating time is 10-40 min, and the current density is 15-20 mA/cm²Continuously stirring the electroplating solution at the temperature of 15-40 ℃ in the electroplating process; wherein, the electroplating solution comprises the following components: 0.03-0.05 mol/L of nickel chloride, 0.03-0.05 mol/L of cobalt sulfate, 0.1-0.2 mol/L of conductive additive, 0.1-0.2 mol/L of pH buffering agent, 0.1-0.2 mol/L of electroplating additive, 0.005-0.03 mol/L of ceric sulfate and deionized water.