CN115478266B

CN115478266B - Post-activation immersion liquid for carrier plate and method for chemically plating nickel and gold on carrier plate

Info

Publication number: CN115478266B
Application number: CN202210989906.5A
Authority: CN
Inventors: 邹佳祁; 廖润秋; 黄玲; 杨玉华; 曾伟雄
Original assignee: Victory Giant Technology Huizhou Co Ltd
Current assignee: Victory Giant Technology Huizhou Co Ltd
Priority date: 2022-08-18
Filing date: 2022-08-18
Publication date: 2024-01-05
Anticipated expiration: 2042-08-18
Also published as: CN115478266A

Abstract

The invention belongs to the field of preparation of printed circuit boards, and particularly relates to an activated immersion liquid for a carrier plate and a carrier plate chemical nickel-gold plating method. The activated immersion liquid used for the carrier plate comprises the following components: passivating agent, complexing agent, dispersing agent, inorganic salt and water; the passivating agent is thiourea and sodium sulfide, and the concentration of the passivating agent in the immersion liquid after the activation is 3-5g/L and 0.5-2g/L respectively. The activated immersion liquid can be used for cleaning the ink of a high-precision circuit (such as a carrier plate) and the ionic palladium adsorbed on a pp sheet area, and the invention can realize a better post-immersion effect, has a good removal effect on the ionic palladium and can realize no seepage plating and missing plating phenomenon after nickel plating and gold plating.

Description

Post-activation immersion liquid for carrier plate and method for chemically plating nickel and gold on carrier plate

Technical Field

The invention belongs to the field of preparation of printed circuit boards, and particularly relates to an activated immersion liquid for a carrier plate, and a carrier plate chemical nickel-gold plating method using the activated immersion liquid.

Background

A printed circuit board (Printed Circuit Board, PCB) is a functional substrate for connection between components formed by electronic printing of a pre-designed circuit on a surface of an insulating substrate. In order to ensure solderability, corrosion resistance, oxidation resistance, etc. of the printed circuit board during later assembly and use, a final surface treatment process is performed on the circuit surface. Electroless nickel/displacement gold (ENIG) plating is widely used as one of many surface treatment processes, with its good electrical conductivity and compatibility with high density packaging characteristics. In the chemical nickel plating process, sodium hypophosphite is used as a reducing agent in most cases, a nickel-phosphorus layer is continuously deposited on the surface with catalytic activity, the copper-based surface of the printed circuit board does not have self-catalytic activity, and the chemical nickel plating is initiated by depositing metal with catalytic activity on the surface of the printed circuit board, so that the production cost is increased due to the fact that the skip plating is easy to cause in the current process production.

For example, a palladium activation method for electroless nickel-gold of a PCB disclosed in chinese patent CN202110238810.0 and a double-layer nickel-gold process for surface treatment of a PCB disclosed in chinese patent CN201611270127.0, the surface treatment pretreatment of electroless nickel/displacement gold plating (ENIG) process generally comprises a series of treatment processes of degreasing, microetching, pickling, presoaking, activating, post-leaching, etc., wherein the purpose of the activating is to displace a layer of palladium on copper to catalyze electroless nickel plating. However, the plate surface after microetching does not only roughen the copper surface but also roughen the pp sheet and ink, thereby adsorbing a layer of ionic palladium on the pp sheet and ink. Both the displaced palladium and the ionic palladium have the effect of catalyzing nickel, which can lead to a plating-through phenomenon if left untreated. At present, palladium is usually removed by using post-immersion liquid in the process production of the PCB, and the prior post-immersion liquid generally adopts sulfuric acid solution to dissociate the ionic palladium adsorbed on the ink or pp sheet, but cannot corrode and replace the palladium. As the line width and the line distance of the carrier plate are narrowed, the rough area formed by the micro-etched ink or pp sheet is increased, so that the adsorption quantity of ionic palladium is greatly increased, and in addition, as the relatively firm palladium ions and chemical bond coordination compounds on high polymer materials such as the ink and the pp sheet are even generated in the adsorption process, the ionic palladium is difficult to separate. Therefore, the activated immersion liquid used for the stable and efficient carrier plate is provided, so that the technical problem that sulfuric acid solution cannot completely clean ink, pp sheets and other adsorbed ionic palladium of a high-precision circuit (such as the carrier plate) is solved, and the activated immersion liquid has great significance in the field.

Disclosure of Invention

The technical problems to be solved by the invention are as follows: the activated immersion liquid for the carrier plate can be used for removing ionic palladium adsorbed on pp sheets and printing ink after palladium plating activation in the preparation process of the carrier plate.

The second technical problem to be solved by the invention is to provide a method for plating nickel and gold on a carrier plate by using the activated immersion liquid for post-immersion.

The technical scheme for solving the technical problems is as follows:

the invention provides an activated immersion liquid for a carrier plate, which comprises the following components: passivating agent, complexing agent, dispersing agent, inorganic salt and water; the passivating agent is thiourea and sodium sulfide, and the concentration in the immersion liquid after the activation is 3-5g/L and 0.5-2g/L respectively.

Further, the complexing agent is N-nitrosophenylhydroxylamine and 3, 5-dinitrosalicylic acid, and the concentration in the immersion liquid after the activation is 0.1-0.5g/L and 0.5-2.5g/L respectively. The weight ratio of N-nitrosophenylhydroxylamine to 3, 5-dinitrosalicylic acid is 1:4-6. The ratio and the material combination can improve the stability of palladium ions under the acidic condition, can well solve the problem caused by acidity, and have good resistance to impurity metal ions such as iron, copper, zinc and the like.

Further, the dispersing agent is sodium 2,2' -methylenebis (4, 6-di-tert-butylphenyl) phosphate, and the concentration of the dispersing agent in the immersion liquid after the activation is 0.01-0.05g/L. Sodium 2,2' -methylenebis (4, 6-di-tert-butylphenyl) phosphate is used as a dispersing agent to disperse and wrap ionic palladium complexed by N-nitrophenylhydroxylamine and 3, 5-dinitrosalicylic acid, thereby preventing aggregation and re-adsorption on a substrate.

Further, the inorganic salt is sodium chloride, and the concentration in the immersion liquid after the activation is 0.2-0.8g/L, preferably 0.5g/L. The sodium chloride helps the adsorbed palladium ions to accelerate dissociation, thereby playing an auxiliary role.

The invention also provides a method for carrying out electroless nickel-gold plating on the support plate, which comprises the step of carrying out post-leaching treatment by using the activated immersion liquid. The remaining steps other than the post-leaching step may be any known and electroless nickel gold plating methods involving palladium activation steps, the specifics of which should also be known. For example, including but not limited to, copper surfaces of printed circuit boards, degreasing, microetching, pickling, presoaking, palladium activation, electroless nickel gold, and the like. The palladium activation refers to a process step of forming a palladium layer on the surface of a carrier plate part by using a physical or chemical means, and aims to catalyze electroless nickel plating.

Further, the post-leaching comprises the steps of:

s1, adding water into a passivating agent and inorganic salt to prepare an aqueous solution according to X times of the expected concentration, regulating the pH value to 3-4 to obtain a first solution, and adding water into a dispersing agent and complexing agent to prepare an aqueous solution according to X times of the expected concentration to obtain a second solution, wherein X is more than or equal to 5 and less than or equal to 25;

the first solution and the second solution are respectively prepared, and the thiourea can be prevented from dissociating by combining the pH value adjusting operation, so that the quality guarantee period is prolonged. The preparation is concentrated solution, which is favorable for storage, transportation and use.

S2, taking 1 part by volume of the first solution as 1 part by volume, taking 1/X part by volume of the first solution, injecting the first solution into a container, adding (2-5)/X parts by volume of pure water, adjusting the pH to 5-5.6, mixing with 1/X parts by volume of the second solution, and supplementing the mixture with pure water to reach the expected concentration of each component, thereby obtaining the activated immersion liquid;

s3, immersing the carrier plate which needs post-immersion into the activated immersion liquid at the temperature of 25-30 ℃ for 1-2 minutes.

Further, the above-described pH adjustment step may use a general pH adjuster, and in some embodiments the pH adjuster selected is sulfuric acid and sodium hydroxide.

Further, step S3 further includes: and titrating by adopting a zinc sulfate precipitation method, testing the concentration of the sodium sulfide, restarting the cylinder opening if the concentration is more than 2g/L, and supplementing the sodium sulfide to 0.5-2g/L if the concentration is less than 0.5g/L. On one hand, the high concentration of sodium sulfide can be adsorbed on the surface of a substrate together with the precipitate generated by palladium to cause poor quality of the plate surface, and on the other hand, too low concentration can lead to incomplete palladium dissociation and easy precipitation. The sulfur ions may be consumed by the board carry-over, and the adsorption capacity of the sulfur ions and palladium forming colloid groups is enhanced, so that analysis and control are required.

Further, step S3 further includes: immersing the carrier plate, and promoting the complex compound to separate from the surface of the substrate in a micro-vibration mode under the atmosphere of nitrogen, wherein the pressure of the nitrogen is 1.5-2.5kg/cm ³ . This method can prevent sulfur and thiourea from forming adsorption complex to palladium ion in the immersion liquid after activation, and increase the effect of releasing the complex from the surface of the substrate, and needs to be carried out under the condition of nitrogen charging, so as to promote the complex to release from the surface of the substrate in a micro-vibration mode.

Further, step S3 further includes: the pH value is controlled to 3-6. In some embodiments, the adjustment is made with 10% sulfuric acid at the higher level and with 10% sodium hydroxide solution at the lower level.

The beneficial effects of the invention are as follows:

the thiourea and sodium sulfide disclosed by the invention are passivating agents, and have strong pulling action on ionic palladium; sodium chloride improves the dissociation of ionic palladium; n-nitrosophenylhydroxylamine and 3, 5-dinitrosalicylic acid play a role in complexing palladium, prevent the formation of sediment accumulating excessive sulfur-containing palladium, and prolong the service life of the immersion liquid after activation; sodium 2,2' -methylenebis (4, 6-di-tert-butylphenyl) phosphate is used as a dispersing agent to disperse and wrap ionic palladium complexed by N-nitroaniline and 3, 5-dinitrosalicylic acid, so as to prevent aggregation and re-adsorption on a substrate.

Drawings

Fig. 1 is a SEM image of carrier hole ring (left) and PAD (right) nickel corrosion prepared in example 1 of the present invention.

Fig. 2 is a SEM image of carrier hole ring (left) and PAD (right) nickel corrosion prepared in example 2 of the present invention.

Fig. 3 is a SEM image of carrier hole ring (left) and PAD (right) nickel corrosion prepared in example 3 of the present invention.

Fig. 4 is a SEM image of carrier plate hole rings (left) and PAD (right) nickel corrosion prepared from the common post-activation immersion liquid of the market of comparative example 1.

Detailed Description

The present invention will be described in detail with reference to the following examples, which are only preferred embodiments of the present invention and are not limiting thereof.

And (3) taking a certain carrier plate with the same size as a test base material, comparing the immersion liquid after common activation with the immersion liquid after complete activation in the scheme in the market, plating nickel for 25min, plating gold for 10min, comparing the thickness difference of nickel and gold, and observing the situation of skip plating and diffusion plating by using the gold surface color difference and the nickel corrosion comparison difference.

The following examples and comparative examples were each carried out using the following electroless nickel gold pretreatment methods:

the pretreatment method for electroless nickel and gold plating comprises the well-known acid degreasing for 3-5min at 50-60 ℃, microetching for 2-3min, pickling for 1min25-30 ℃, presoaking for 1-2min25-30 ℃, activating for 30s-2min25-30 ℃ and then soaking for 1-2min25-30 ℃.

The post-dipping comprises the following steps:

s1, adding water into a passivating agent and inorganic salt according to 10 times of expected concentration to prepare an aqueous solution, adjusting the pH value to 3-4 to obtain a first solution, and adding water into a dispersing agent and complexing agent according to 10 times of expected concentration to prepare the aqueous solution;

s2, recording the volume of the first solution as 1 part, taking 1/10 of the volume of the first solution, injecting the first solution into a container, adding 1/10 of pure water, adjusting the pH to 5-5.6 by using sodium hydroxide, mixing with 1/10 of the volume of the second solution, and supplementing the mixture with pure water until the concentration of each component is equal to that of the activated immersion liquid, thereby obtaining the activated immersion liquid;

Step S3 further includes: and (3) titrating by adopting a zinc sulfate precipitation method, testing the concentration of the sodium sulfide, discarding the current activated immersion liquid if the concentration is more than 2g/L, returning to the step (S2) to reformulate the activated immersion liquid, and supplementing the sodium sulfide to 0.5-2g/L if the concentration is less than 0.5g/L.

Step S3 further includes: immersing the carrier plate, and promoting its complex to separate from the surface of the base material in the form of micro vibration under nitrogen atmosphere with nitrogen pressure of 1.5-2.5kg/cm ³ 。

Step S3 further includes: the pH value is controlled to be 3-6, the higher is regulated by 10% sulfuric acid, and the lower is regulated by 10% sodium hydroxide solution.

Example 1 consisted of the following components: thiourea 4g/L, sodium sulfide 1g/L, sodium chloride 0.5g/L, N-nitrophenylhydroxylamine 0.3/L, 2' -methylenebis (4, 6-di-tert-butylphenyl) phosphate sodium 0.03g/L, 3, 5-dinitrosalicylic acid 1.8g/L.

Example 2 consisted of the following components: thiourea 3g/L, sodium sulfide 0.5g/L, sodium chloride 0.5g/L, N-nitrophenylhydroxylamine 0.1g/L, 2' -methylenebis (4, 6-di-tert-butylphenyl) phosphate sodium 0.01g/L, 3, 5-dinitrosalicylic acid 0.4g/L.

Example 3 consisted of the following components: thiourea 5g/L, sodium sulfide 2g/L, sodium chloride 0.5g/L, N-nitrophenylhydroxylamine 0.5g/L, 2' -methylenebis (4, 6-di-tert-butylphenyl) phosphate sodium 0.05g/L, 3, 5-dinitrosalicylic acid 2.5g/L.

Comparative example 1 is a commercially available post-activation dip.

Comparative example 2 contains no dispersant sodium 2,2' -methylenebis (4, 6-di-t-butylphenyl) phosphate and the other components are the same as in example 1.

Comparative example 3 does not contain sodium sulfide and the other components are the same as in example 1.

Comparative example 4 does not contain thiourea and the other components have the same constitution as in example 1.

Comparative example 5 does not contain thiourea and sodium sulfide, and the other components are constituted the same as in example 1.

The same type and size of carrier plate is taken as a test base material, the activated immersion liquids of the examples 1-3 and the comparative examples 1-5 are compared, nickel is plated for 25min, gold is plated for 10min, the thickness difference of nickel and gold is compared, the chromatic aberration of gold surface and the nickel corrosion difference are compared, and the situation of skip plating and infiltration plating is observed.

From the following carrier plates treated with each activated dip example, 10 pieces of each group were taken to observe the number of carrier plates in which the dip plating occurred, and the dip plating rate= (number of carrier plates in which the dip plating occurred/number of carrier plates in each group) ×100%, and the results were recorded as the following table.

Activated immersion liquid	Example 1	Example 2	Example 3	Comparative example 1	Comparative example 2	Comparative example 3	Comparative example 4	Comparative example 5
									Rate of diffusion coating	0%	0%	0%	40%	50%	60%	40%	80%

As can be seen from the above table data, the immersion liquid after ordinary activation in the market of comparative example 1 causes the diffusion plating, and the lack of the dispersant in comparative example 2 causes the diffusion plating rate to reach 50%; comparative examples 3-5 were each free of sodium sulfide, thiourea and sodium sulfide only, and the plating penetration rates were higher than the activated immersion liquid claimed herein, indicating that thiourea and sodium sulfide have a synergistic effect.

After the activation of the scheme, the immersion liquid is treated in example 1 and then is treated in Ni ²⁺ The concentration was 4.9g/L, the P content was 8.64 and 8.35 at a temperature of 81℃and a pH of 4.6, and the deposition rate was 7.4. 7.4 u'/min. The SEM image of the nickel corrosion at the ring position is shown in fig. 1 (left), and the SEM image of the nickel corrosion at the ring position is shown in fig. 1 (right).

After the activation of the scheme, the immersion liquid is treated in example 2, and then is treated in Ni ²⁺ The concentration was 4.9g/L, the P content was 8.31 and 8.34 at a temperature of 81℃and a pH of 4.6, and the deposition rate was 7.4. 7.4 u'/min. The SEM image of the nickel corrosion at the ring position is shown in fig. 2 (left), and the SEM image of the nickel corrosion at the PAD position is shown in fig. 2 (right).

After the activation of the scheme, the immersion liquid is treated in example 3 and then is treated in Ni ²⁺ The concentration was 4.9g/L, the P content was 8.42 and 8.21 at a temperature of 81℃and a pH of 4.6, and the deposition rate was 7.4. 7.4 u'/min. Kong Huannie SEM of the corrosion is shown in FIG. 3 (left), and SEM of the PAD nickel corrosion is shown in FIG. 3 (right).

After the immersion liquid treatment after the common activation in the market of comparative example 1, the treatment is carried out on Ni ²⁺ The concentration was 4.9g/L, the P content was 7.7 and 8.24 at a temperature of 81℃and a pH of 4.6, and the deposition rate was 7.2 u'/min. The SEM image of the nickel corrosion at the ring position is shown on the left of fig. 4, and the SEM image of the nickel corrosion at the PAD position is shown on the right of fig. 4.

As can be seen from the experimental results and SEM images, the activated immersion liquid claimed by the invention can not influence the nickel deposition speed and nickel corrosion in the normal nickel plating process under the condition that the immersion liquid does not generate the immersion plating, and can form a nickel layer similar to the nickel plating after the immersion liquid treatment after the common activation in the market on the pore ring and PAD.

The carrier plate which is subjected to post-dipping by using the common post-activation immersion liquid in the market has no plating leakage and has a plating seepage phenomenon, and the carrier plate which is subjected to post-activation immersion liquid in the embodiments 1-3 has no plating leakage and plating seepage phenomenon. It can also be seen that nickel corrosion of the support plate, post-dip using commercially common post-activation dip, is more severe.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the scope of the technical concept of the present invention, and all the simple modifications belong to the protection scope of the present invention.

In addition, the specific features described in the above embodiments may be combined in any suitable manner without contradiction. The various possible combinations of the invention are not described in detail in order to avoid unnecessary repetition.

Moreover, any combination of the various embodiments of the invention can be made without departing from the spirit of the invention, which should also be considered as disclosed herein.

Claims

1. The activated immersion liquid for the carrier plate is characterized by comprising the following components: passivating agent, complexing agent, dispersing agent, inorganic salt and water; the passivating agent is thiourea and sodium sulfide, and the concentration in the immersion liquid after the activation is 3-5g/L and 0.5-2g/L respectively;

the complexing agent is N-nitrosoaniline and 3, 5-dinitrosalicylic acid, the concentration in the immersion liquid after activation is 0.1-0.5g/L and 0.5-2.5g/L respectively, and the weight ratio of N-nitrosoaniline to 3, 5-dinitrosalicylic acid is 1:4-6;

the inorganic salt is sodium chloride, and the concentration of the inorganic salt in the immersion liquid after the activation is 0.2-0.8g/L.

2. The post-activation dip according to claim 1, wherein the dispersant is sodium 2,2' -methylenebis (4, 6-di-t-butylphenyl) phosphate, and the concentration in the post-activation dip is 0.01-0.05g/L.

3. A method of electroless nickel plating of a carrier plate, comprising a post-dip step using the activated post-dip of any one of claims 1-2.

4. A method according to claim 3, wherein the post-leaching comprises the steps of:

s1, adding water into a passivating agent and inorganic salt to prepare an aqueous solution according to X times of an expected concentration, regulating the pH value to 3-4 to obtain a first solution, and adding water into a dispersing agent and complexing agent to prepare an aqueous solution according to X times of the expected concentration to obtain a second solution, wherein X is more than or equal to 5 and less than or equal to 25;

5. The method of claim 4, wherein step S3 further comprises: and (3) titrating by adopting a zinc sulfate precipitation method, testing the concentration of the sodium sulfide, discarding the current activated immersion liquid if the concentration is more than 2g/L, returning to the step (S2) to reformulate the activated immersion liquid, and supplementing the sodium sulfide to 0.5-2g/L if the concentration is less than 0.5g/L.

6. The method of claim 4, wherein step S3 further comprises: immersing the carrier plate, and promoting its complex to separate from the surface of the base material in the form of micro vibration under nitrogen atmosphere with nitrogen pressure of 1.5-2.5kg/cm ³ 。

7. The method of claim 4, wherein step S3 further comprises: the pH value of the carrier plate is controlled to be 3-6 after the carrier plate is immersed.