CN108517522B - A kind of chemical deplating composition and deplating method for nickel-copper alloy layer of PCB/Sn/NiCu structure circuit board - Google Patents

Abstract

The invention discloses a nickel-copper alloy layer chemical deplating composition for a PCB/Sn/NiCu structure circuit board and a deplating method thereof. The deplating composition comprises 40-70 g/L of m-nitrobenzenesulfonate, 10-20 g/L of cyclohexanediaminetetraacetic acid, 2.5-5 g/L of cyclodextrin, 6-12g/L of ammonia water and water, and the pH value is 7.2-7.5. The deplating method comprises the following steps: (1) weighing sodium m-nitrobenzenesulfonate, cyclohexanediamine tetraacetic acid and cyclodextrin according to the content of each component, sequentially dissolving in water to obtain an aqueous solution, then adding ammonia water, and controlling the pH value of the deplating solution to be 7.2-7.5. (2) And (2) soaking the PCB/Sn/NiCu structure circuit board in the deplating solution prepared in the step (1). (3) And (3) taking out the circuit board in the step (2), ultrasonically cleaning with water and drying. (4) And (4) soaking the surface of the circuit board in the step (3) in a formic acid aqueous solution. (5) And (4) taking out the surface of the circuit board in the step (4), ultrasonically cleaning the circuit board by using water and drying the circuit board.

Description

A kind of chemical stripping composition of nickel-copper alloy layer for PCB/Sn/NiCu structure circuit board and its deplating method

technical field

The invention relates to a deplating composition and a deplating method thereof, in particular to a chemical deplating composition for a nickel-copper alloy layer of a circuit board with a PCB/Sn/NiCu structure and a deplating method thereof.

Background technique

Electroless metal plating is widely used for its excellent wear resistance, corrosion resistance, weldability and outstanding electromagnetic shielding properties, especially the uniform thickness of the coating and good profiling, which is especially suitable for workpieces with complex shapes. Although the PCB process adopts advanced technology and strictly controls the process operation, there will be defective products due to various reasons, such as surface oxidation, penetration plating, etc. If it is directly scrapped, the cost will be high; Strong corrosion resistance, while the difficulty is great. Although general hardware electroplating manufacturers have developed some methods of electroless nickel plating, it is often difficult to directly apply them to PCB production due to different substrates and process objects, such as higher requirements for corrosion inhibition due to temperature restrictions. In the traditional deplating solution, the main component is high-concentration nitric acid, which can easily cause serious corrosion to the substrate during deplating. In addition, due to the presence of strong oxidizing concentrated nitric acid, the nitric acid will react with the metal during deplating, releasing a large amount of smoke that seriously pollutes the atmosphere and causes serious injury to the workshop staff.

At the same time, since a layer of metal and/or alloy is not deposited on the surface of the PCB, there may be multiple layers of metal and/or alloy. When the deplating solution deplats the nickel-copper alloy layer on the surface of the PCB, the temperature of the deplating solution and the deplating soaking time can be optimized and adjusted according to the specific thickness of the nickel-copper alloy layer. However, most stripping solutions usually use strictly controlled stripping time to strip the nickel-copper alloy layer. Although the nickel-copper alloy layer can be effectively removed, it is also prone to incomplete stripping or excessive stripping, resulting in stripping of the underlying metal layer of the nickel-copper alloy layer.

Contents of the invention

The object of the invention is to provide a kind of chemical deplating composition and deplating method for nickel-copper alloy layer of circuit board with PCB/Sn/NiCu structure, to solve the technical problem of excessive corrosion tin layer of existing deplating composition, solve deplating simultaneously A technical problem with unstable rates.

The following technical solutions adopted by the present invention to solve its technical problems are:

A nickel-copper alloy layer chemical deplating composition for a PCB/Sn/NiCu structure circuit board, comprising 40-70 g/L of sodium m-nitrobenzenesulfonate, 10-20 g/L of cyclohexanediaminetetraacetic acid, Cyclodextrin 2.5-5 g/L, ammonia 6-12 g/L, and water, the pH value is 7.2-7.5.

Further, the chemical deplating composition for the nickel-copper alloy layer of the PCB/Sn/NiCu structure circuit board includes 50-60 g/L of sodium m-nitrobenzenesulfonate, 12-18 g of cyclohexanediaminetetraacetic acid /L, cyclodextrin 3-4 g/L, ammonia water 8-10 g/L, and water, the pH value is 7.2-7.5.

Further, the nickel-copper alloy layer chemical deplating composition for the PCB/Sn/NiCu structural circuit board also includes a penetrant 0.5-1.5 g/L.

Further, the penetrating agent is sodium butyl naphthalene sulfonate.

A kind of PCB/Sn/NiCu structural circuit board uses nickel-copper alloy layer chemical deplating composition deplating method, it comprises the following steps:

(1) According to the content of each component, weigh sodium m-nitrobenzenesulfonate, cyclohexanediaminetetraacetic acid, and cyclodextrin and dissolve them in water in turn to obtain an aqueous solution, and then add ammonia water to control the pH of the stripping solution Values are in the range of 7.2-7.5.

(2) Soak the PCB/Sn/NiCu structural circuit board in the deplating solution prepared in step (1).

(3) Take out the circuit board described in step (2), ultrasonically clean it with water and dry it.

(4) Soak the surface of the circuit board described in step (3) in formic acid aqueous solution.

(5) Take out the surface of the circuit board described in step (4), ultrasonically clean it with water and dry it.

Further, the soaking temperature in the step (2) is 35-60° C., and the soaking time is 3-10 minutes.

Further, the concentration of formic acid in the step (4) is 5-10 g/L.

Further, the soaking temperature in the step (4) is 20-40° C., and the soaking time is 2-10 minutes.

In the nickel-copper alloy layer chemical deplating composition for a PCB/Sn/NiCu structure circuit board of the present invention, the functions of the components involved are respectively: the sodium m-nitrobenzenesulfonate molecule contains an oxidation group—" NO ₂ ”, its oxidizing property is weaker than that of HNO ₃ . This feature enables it to oxidize metals into ions without being too oxidizing, thus avoiding excessive deplating rate and excessive corrosion of the underlying metal tin.

It is very important to select an appropriate complexing agent to accelerate the stripping speed. The role of the complexing agent is to form a stable complex with the oxidized coating metal ions, so that the activity of the coating metal ions in the solution decreases, the equilibrium potential shifts negatively, and the oxidation is accelerated. The present invention preferably has cyclohexanediaminetetraacetic acid with a special structure, which can dynamically adjust the concentration of divalent nickel and copper ions in the stripping solution, and can be regarded as a concentration regulator of divalent nickel and copper ions. By controlling the nickel and copper ions generated in the reaction process, it can avoid the uniformity of stripping rate. The process of cyclohexanediaminetetraacetic acid complexed with divalent nickel and copper ions is reversible, that is, cyclohexanediaminetetraacetic acid will realize dynamic equilibrium along with divalent nickel and copper ion concentrations in the stripping composition, for example When the concentration of divalent nickel and copper ions is too high, cyclohexane diamine tetraacetic acid "complexes" with divalent nickel and copper ions, which reduces the concentration of divalent nickel and copper ions. When the concentration is low, divalent nickel and copper ions are complexed before cyclohexanediaminetetraacetic acid is released, so that the concentration of divalent nickel and copper ions in the stripping composition increases. In addition, cyclohexanediaminetetraacetic acid, a complex compound with a ring structure, can adsorb and form a film on the surface of metal tin to inhibit the corrosion of tin by the stripping solution.

Because most of the components in the stripping solution can not only corrode nickel copper, but also corrode other metals, such as tin and zinc. In order to avoid corrosion of metal tin after the nickel-copper alloy layer is completely stripped due to poor time control, the present invention uses cyclodextrin to be adsorbed on the surface of tin hydroxide (Sn(OH) ₂ ) to form a dense film layer, thereby The metal tin is isolated from the stripping composition, thereby achieving the technical effect of non-corrosion and stripping the metal tin layer. for. The deplating solution contains weakly alkaline ammonia water components, which can react with metal tin to form a layer of tin hydroxide (Sn(OH) ₂ ) on the surface of metal tin. The chemical properties of tin hydroxide (Sn(OH) ₂ ) are unstable, and other substances are easily formed under strong alkaline conditions, so the pH value of the stripping composition is controlled within the range of 7.2-7.5. The ammonia water acts as a pH regulator, and at the same time, the ammonia water can also form stable complexes with nickel and copper metal ions in the stripping composition.

When the stripping composition corrodes the nickel-copper alloy layer, it will inevitably corrode the metal tin to generate tin ions, and due to the existence of cyclohexanediaminetetraacetic acid in the stripping composition, the tin ion is complexed and adsorbed on the surface of the metal tin , further preventing further corrosion of metal tin.

Sodium butylnaphthalene sulfonate, as an alkali-resistant penetrating agent, can significantly reduce the surface tension of water, has excellent penetrating power and wettability, and promotes the dissolution of the nickel-copper alloy layer and the chelation of nickel and copper ions.

Formic acid, as a weak acid, can react with tin hydroxide (Sn(OH) ₂ ) to generate tin chloride, thereby detaching cyclodextrin. And under weak acid environment, tin does not react with formic acid, avoiding the corrosion of tin.

The beneficial effects of the present invention are: the deplating composition of the present invention adopts sodium m-nitrobenzene sulfonate as nickel and copper to corrode into ions, and cyclohexanediaminetetraacetic acid is complexed with metal ions, and the mutual synergy between the two ensures a stable stripping rate. Cyclohexanediaminetetraacetic acid and cyclodextrin cooperate with each other to form a dense film on the surface of metal tin, which avoids excessive corrosion of metal tin. The deplating process does not produce harmful gas, reduces environmental pollution, and improves the working environment; the cost is reduced, the process is simple, and it is beneficial to actual production; the deplating is clean and the effect is good.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example 1

A nickel-copper alloy layer chemical deplating composition for a PCB/Sn/NiCu structural circuit board, comprising sodium m-nitrobenzene sulfonate 40g/L, cyclohexanediaminetetraacetic acid 10g/L, cyclodextrin 2.5g /L, ammonia water 6g/L, and water, the pH value is 7.2.

A method for deplating a nickel-copper alloy layer chemical deplating composition for a circuit board with a PCB/Sn/NiCu structure, comprising the following steps: (1) weighing sodium m-nitrobenzenesulfonate, cyclohexyl Alkane diamine tetraacetic acid and cyclodextrin are dissolved in water successively to obtain an aqueous solution, and then ammonia water is added to control the pH value of the deplating solution in the range of 7.2.

(2) Soak the PCB/Sn/NiCu structural circuit board in the deplating solution prepared in step (1), the immersion temperature is 35°C, and the immersion time is 3min.

(3) Take out the circuit board described in step (2), ultrasonically clean it with water and dry it.

(4) Soak the surface of the circuit board in step (3) in formic acid aqueous solution, the concentration of formic acid is 5g/L.

(5) Take out the surface of the circuit board described in step (4), ultrasonically clean it with water and dry it.

Example 2

A nickel-copper alloy layer chemical deplating composition for a PCB/Sn/NiCu structure circuit board, comprising sodium m-nitrobenzene sulfonate 50g/L, cyclohexanediaminetetraacetic acid 12g/L, cyclodextrin 3g/L L, ammonia water 8g/L, sodium butylnaphthalene sulfonate 0.5 g/L and water, the pH value is 7.5.

A method for deplating a nickel-copper alloy layer chemical deplating composition for a circuit board with a PCB/Sn/NiCu structure, comprising the following steps: (1) weighing sodium m-nitrobenzenesulfonate, cyclohexyl Alkanediaminetetraacetic acid, cyclodextrin and sodium butyl naphthalene sulfonate are dissolved in water successively to obtain an aqueous solution, and then ammonia water is added to control the pH value of the deplating solution in the range of 7.5.

(2) Soak the PCB/Sn/NiCu structural circuit board in the deplating solution prepared in step (1), the immersion temperature is 40°C, and the immersion time is 5min.

(3) Take out the circuit board described in step (2), ultrasonically clean it with water and dry it.

(4) Soak the surface of the circuit board in step (3) in formic acid aqueous solution, the concentration of formic acid is 7g/L.

(5) Take out the surface of the circuit board described in step (4), ultrasonically clean it with water and dry it.

Example 3

A nickel-copper alloy layer chemical deplating composition for a PCB/Sn/NiCu structure circuit board, comprising sodium m-nitrobenzene sulfonate 70g/L, cyclohexanediaminetetraacetic acid 20g/L, cyclodextrin 5g/L L, ammonia water 12g/L, sodium butyl naphthalene sulfonate 1.5 g/L and water, the pH value is 7.3.

A method for deplating a nickel-copper alloy layer chemical deplating composition for a circuit board with a PCB/Sn/NiCu structure, comprising the following steps: (1) weighing sodium m-nitrobenzenesulfonate, cyclohexyl Alkanediaminetetraacetic acid, cyclodextrin and sodium butylnaphthalene sulfonate are dissolved in water successively to obtain an aqueous solution, and then ammonia water is added to control the pH value of the deplating solution in the range of 7.3.

(2) Soak the PCB/Sn/NiCu structural circuit board in the deplating solution prepared in step (1), the immersion temperature is 50°C, and the immersion time is 7min.

(3) Take out the circuit board described in step (2), ultrasonically clean it with water and dry it.

(4) Soak the surface of the circuit board in step (3) in formic acid aqueous solution, the concentration of formic acid is 10g/L.

(5) Take out the surface of the circuit board described in step (4), ultrasonically clean it with water and dry it.

Example 4

A nickel-copper alloy layer chemical deplating composition for a PCB/Sn/NiCu structure circuit board, comprising sodium m-nitrobenzene sulfonate 60g/L, cyclohexanediaminetetraacetic acid 18g/L, cyclodextrin 4g/L L, ammonia water 10g/L, sodium butyl naphthalene sulfonate 1.5 g/L and water, the pH value is 7.2.

A method for deplating a nickel-copper alloy layer chemical deplating composition for a circuit board with a PCB/Sn/NiCu structure, comprising the following steps: (1) weighing sodium m-nitrobenzenesulfonate, cyclohexyl Alkanediaminetetraacetic acid, cyclodextrin and sodium butyl naphthalene sulfonate are dissolved in water successively to obtain an aqueous solution, and then ammonia water is added to control the pH value of the deplating solution in the range of 7.2.

(2) Soak the PCB/Sn/NiCu structural circuit board in the deplating solution prepared in step (1), the immersion temperature is 60°C, and the immersion time is 3min.

(3) Take out the circuit board described in step (2), ultrasonically clean it with water and dry it.

(4) Soak the surface of the circuit board in step (3) in formic acid aqueous solution, the concentration of formic acid is 10g/L.

(5) Take out the surface of the circuit board described in step (4), ultrasonically clean it with water and dry it.

It can be understood that, the above embodiments are only exemplary embodiments adopted for illustrating the principle of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims (6)

1. a kind of PCB/Sn/NiCu structural circuit plate nickel-copper alloy layer chemistry strip composition, which is characterized in that including nitre Base benzene sulfonic acid sodium salt 40-70 g/L, cyclohexanediamine tetraacetic acid 10-20 g/L, cyclodextrine 2.5-5 g/L, ammonium hydroxide 6-12 G/L, bleeding agent 0.5-1.5 g/L and water, pH value 7.2-7.5；The bleeding agent is sodium butylnaphthalenesulfonate.

2. PCB/Sn/NiCu structural circuit plate according to claim 1 nickel-copper alloy layer chemistry strip composition, special Sign is, including m-nitrobenzene sodium sulfonate 50-60 g/L, cyclohexanediamine tetraacetic acid 12-18 g/L, cyclodextrine 3-4 G/L, ammonium hydroxide 8-10 g/L, sodium butylnaphthalenesulfonate 0.5-1.5 g/L and water, pH value 7.2-7.5.

3. a kind of such as claim 1-2 described in any item PCB/Sn/NiCu structural circuit plates nickel-copper alloy layer chemistry strip Composition strip method comprising following steps:

(1) according to each component content, m-nitrobenzene sodium sulfonate, cyclohexanediamine tetraacetic acid, cyclodextrine, butyl naphthalene sulfonic acids are weighed Sodium is successively dissolved in water, obtains aqueous solution, then adds ammonium hydroxide, controls the pH value of decoating liquid in 7.2-7.5 range；

(2) PCB/Sn/NiCu structural circuit plate is soaked in the decoating liquid of step (1) preparation；

(3) circuit board described in step (2) is taken out, is cleaned by ultrasonic with water and is dried；

(4) step (3) described circuit board surface is dipped into aqueous formic acid；

(5) step (4) circuit board surface is taken out, is cleaned by ultrasonic with water and is dried.

4. PCB/Sn/NiCu structural circuit plate according to claim 3 nickel-copper alloy layer chemistry strip composition strip Method, which is characterized in that soaking temperature is 35-60 DEG C in the step (2), soaking time 3-10min.

5. PCB/Sn/NiCu structural circuit plate according to claim 3 nickel-copper alloy layer chemistry strip composition strip Method, which is characterized in that the concentration of formic acid is 5-10 g/L in the step (4).

6. PCB/Sn/NiCu structural circuit plate according to claim 3 nickel-copper alloy layer chemistry strip composition strip Method, which is characterized in that soaking temperature is 20-40 DEG C in the step (4), soaking time 2-10min.