CN113445033A

CN113445033A - Reducing liquid and using method thereof

Info

Publication number: CN113445033A
Application number: CN202110723054.0A
Authority: CN
Inventors: 孙宇曦; 曾庆明
Original assignee: Guangdong Shuocheng Technology Co ltd
Current assignee: Guangdong Shuocheng Technology Co ltd
Priority date: 2021-06-28
Filing date: 2021-06-28
Publication date: 2021-09-28
Anticipated expiration: 2041-06-28
Also published as: CN113445033B

Abstract

The invention discloses a reducing liquid and a using method thereof, which are mainly applied to the field of chemical plating and comprise a solvent, a reducing agent of 100ppm-3000ppm, a cosolvent and a pH regulator, wherein the reducing agent is selected from a composition of an organic reducing agent and an inorganic reducing agent, and the organic reducing agent is a nitrogen-containing compound. The base plate treated by the reducing liquid can keep higher copper deposition rate in a later copper deposition process, but the phenomenon of copper layer scorching can not occur, the generated plating layer has better adhesive force with the base plate, the phenomenon of bubbles can not be generated, and the base plate also has higher backlight grade, wherein the backlight grade reaches more than 9 grades.

Description

Reducing liquid and using method thereof

Technical Field

The invention relates to a reducing solution which is mainly applied to chemical plating, in particular to a chemical copper plating and copper deposition process.

Background

Electroless plating is a process of forming a plating layer by reducing and depositing metal ions in a solution on the surface of a substrate having catalytic activity by using a suitable reducing agent under the condition of no external current. Electroless copper plating is widely applied in the industry of printed electronic equipment, and along with the increasing lightening, thinning and shortening of electronic equipment, the process requirements for depositing a metal layer on an electronic circuit board and performing hole metallization are increasing, so that the electroless copper plating process needs to be further improved, and the stability, the deposition speed and the physical and chemical properties of a plating layer are improved.

The chemical copper plating process is complex and comprises the working procedures of oil removal, micro-etching, activation, glue dissolution, copper deposition and the like, and the reaction of each step can generate great influence on the final plating working procedure. Especially, the reduction pretreatment step before the copper deposition process is very important for the selection of the reduction solution. The existing reducing liquid uses a single reducing agent, the generated reducing effect is not ideal, the generated copper plating layer has insufficient adhesive force, the peeling phenomenon can occur after the reducing liquid is used for a long time, the deposition rate of the copper plating layer needs to be controlled, and the integral reaction time is prolonged.

Disclosure of Invention

In order to solve the problems of weak adhesion of a copper plating layer and slow deposition rate of the plating layer in the prior art, the invention provides a reducing solution in a first aspect, which comprises a solvent and 0.5-5 wt% of a reducing agent; the reducing agent is selected from a combination of an organic reducing agent and an inorganic reducing agent, and the organic reducing agent is a nitrogen-containing compound.

As a preferred embodiment, the nitrogen-containing compound has the structure

Wherein R1, R2 and R3 are independently selected from C_1-6One of alkyl, hydrogen and boryl; r4, R5 and R6 are independently selected from C_1-6Alkyl, hydrogen, one of boryl, and at least one of R4, R5, R6 is boryl.

As a preferred embodiment, the inorganic reducing agent is selected from one or more of phosphite, borohydride, borane in combination.

In a preferred embodiment, the reducing agent is 0.5 to 5 wt% of the reducing solution.

As a preferable embodiment, the reducing solution also comprises 0.001-0.1 wt% of cosolvent and pH regulator.

In a preferred embodiment, the cosolvent is selected from one or a combination of several of aminoalkanes, furans, ethers, alcohols and ketones.

In a preferred embodiment, the furan-like substance is selected from one of alkyl furan, phenyl furan and 2-methyl furan.

As a preferred embodiment, the weight ratio of the reducing agent to the co-solvent is 1: (50-1000).

In a preferred embodiment, the pH of the reducing solution is 9 to 11.

The second aspect of the invention provides a method for using a reducing solution, which comprises the following steps:

(1) placing the substrate treated in the activation step in tap water at the temperature of 20-25 ℃, and soaking for 1-5 min;

(2) mixing a reducing agent, an auxiliary agent and a solvent according to a weight ratio, and adding a pH regulator to regulate the pH to 9-11 to obtain a reducing solution;

(3) and (3) placing the substrate obtained in the step (1) in a reducing solution, wherein the reaction temperature is 32-36 ℃, and the reaction time is 33-37s, so as to obtain the substrate subjected to reduction treatment.

Compared with the prior art, the invention has the following beneficial effects:

(1) after the reduction solution and the use method thereof are treated, a higher copper deposition rate can be kept in a later copper deposition process, a stable copper coating film is formed on the surface, the formed coating is compact, the internal stress is eliminated in the copper deposition process, and the peeling strength is improved.

(2) According to the reducing solution and the use method thereof, after treatment, the surface of the prepared plating layer is more uniform, the formation of plating layer holes is avoided, the generated copper plating layer can achieve a 9-level backlight effect, and the effect is more excellent.

(3) The reducing solution and the use method thereof can further improve the copper deposition rate in the later copper deposition process after the treatment, but the phenomenon of copper layer scorching due to the faster deposition rate can not occur.

(4) The reducing solution and the use method thereof have good adhesive force between the prepared plating layer and the material base material, and can ensure that the plating layer keeps good stability.

(5) According to the reducing liquid and the use method thereof, after treatment, the prepared plating layer and the substrate are tightly combined without generating gaps, the problem of copper deposition expansion and foaming is avoided, and the flatness of the plating layer can be improved.

Drawings

FIGS. 1 to 10 are the backlight effect diagrams of the copper deposition after the reduction solution treatment in examples 1 to 10, respectively.

Detailed Description

As a preferred embodiment, the nitrogen-containing compound has the structure

More preferably, the organic reducing agent of formula 2 is an alkyl borohydride selected from one of dimethylamine borane, ethylamine borane, propylamine borane, methylamine borane and diethylborane.

More preferably, the phosphite is selected from one of sodium phosphite, potassium phosphite, magnesium phosphite, and phosphite.

Further preferably, the borohydride is selected from one of sodium borohydride, potassium borohydride, magnesium borohydride, lithium borohydride, manganese borohydride and lithium aluminum borohydride.

Further preferably, the borane is selected from one of borane, diborane, proparaborane, borane and pentaborane.

In a preferred embodiment, the reducing agent is selected from one or a combination of phosphites, borohydrides and alkyl borohydrides.

Further preferably, the reducing agent is selected from one or a combination of several of sodium phosphite, sodium borohydride and dimethylamine borane.

More preferably, the reducing agent accounts for 2.5-4.5 wt% of the reducing solution.

In a preferred embodiment, in the subsequent copper deposition process, the copper deposition temperature is 30-35 ℃, the copper deposition time is 20-40min, and the type of the activating solution is SCC-A06H.

The formaldehyde reduction is a reagent used in the traditional electroless copper plating, has the characteristics of low plating speed and unstable plating solution property, and simultaneously the formaldehyde gas threatens the health of human bodies, sodium hypophosphite is used for reduction at the present stage, the higher the temperature is in the copper deposition process, the faster the copper deposition rate is, and if the temperature is too high, some unnecessary byproducts influence the peeling strength, the copper deposition temperature lower than 65-70 ℃ in the prior art and the copper deposition time of 20-40min are used in the copper deposition process, the applicant finds in experiments that the activating solution with the model of SCC-A06H is used at the same time, the copper deposition rate at the later stage is too low, and the applicant finds in experiments that when the reducing agent is selected from one or more of phosphite, borohydride and alkyl borohydride, the reducing agent accounts for 0.5-5 wt%, especially 2.5-4.5 wt% of the reducing solution, the applicant believes that the possible reason is that when the phosphite ions, the borohydride ions and the dimethylamine borane are reduced under the action of the reducing agent with a specific concentration and are unevenly distributed in the substrate material, the palladium ions may slightly migrate in the reduction process, so that the reduced palladium is more uniformly distributed on the surface of the substrate, and in the later copper deposition process at a temperature, the copper deposition with a higher rate is maintained to form a stable crystalline phase structure, crystal plane parameters and unit cell parameters are similar to those of standard copper powder, the plating density is higher, the internal stress is eliminated in the copper deposition process, and the peel strength is improved.

In a preferred embodiment, the pH adjuster is one selected from sulfuric acid, boric acid, sodium hydroxide, sodium ethoxide, picoline, lutidine, 2-vinylpyridine, 2-methyl-5-ethylpyridine, and caffeine.

More preferably, the aminoalkane is one selected from ethylamine, diethylamine, triethylamine, n-propylamine and n-butylamine.

Further preferably, the ether substance is selected from one of methyl ether, diethyl ether, dibutyl ether, phenyl ether and epoxy diethyl ether.

Further preferably, the alcohol is selected from one of methanol, ethanol, n-propanol, isobutanol, propylene glycol, hexylene glycol and n-hexylene alcohol.

As a preferred embodiment, the co-solvent is a combination of furans and aminoalkanes.

Further preferably, the cosolvent is a combination of 2-methylfuran and diethylamine.

Further preferably, the weight ratio of 2-methylfuran to diethylamine is 1: (1-5), more preferably 1: 3.

in a preferred embodiment, the material of the deposited substrate is a composite material of glass fiber and epoxy resin.

More preferably, the substrate is an FR-4 plate.

The applicant finds that when the substrate is a composite material of glass fiber and epoxy resin, especially an FR-4 plate, the reducing agent is directly used for reducing the substrate, the backlight effect of the later copper precipitation is not good, and the applicant unexpectedly finds that when the reducing solution also comprises 1-3000ppm of cosolvent, especially the cosolvent comprises furan substances and amino alkane, and the weight ratio of the cosolvent is 1: (1-5), at this moment, the backlight grade is greater than or equal to 9, the applicant thinks that the possible reason is that, through the pretreatment of the glass fiber and the epoxy resin by the furan-like substances and the amino alkane with specific proportion, at this moment, the reducing liquid can be fully spread and infiltrated on the surface of the composite material, so that the metal core of the noble metal with the catalytic action is effectively exposed, the uniformity of copper deposition is ensured, the copper deposition cavity is avoided, and the effect is most remarkable especially when the cosolvent is 2-methyl furan and diethylamine.

More preferably, the weight ratio of the reducing agent to the cosolvent is 1 (50-800).

Further preferably, the weight ratio of the reducing agent to the co-solvent is 1: 500.

The applicant has surprisingly found that when the weight ratio of reducing agent to hydrotrope is 1: (1000-50), especially 1:500, the copper layer can be prevented from expanding and foaming, and the surface flatness of the copper layer is improved, the applicant thinks that the possible reason is that after the fluxing matter with specific content and type and the reducing agent are reduced, the complexing force between copper ions and catalytic metal is stronger during copper deposition, so that the catalytic capability is effectively improved, and during copper deposition, the copper layer and the substrate are tightly combined without clearance, so that the problem of copper deposition expansion and foaming is avoided, and the flatness of the copper layer is improved.

In a preferred embodiment, the pH of the reducing solution is 9 to 11, more preferably 10 to 10.5.

In the copper deposition process, the temperature, the surfactant and the like directly influence the copper deposition rate, in order to improve the economic benefit, the copper deposition is required to be kept at a certain rate level, however, the copper deposition rate is too high, the copper layer scorching phenomenon can be caused, generally, the pH is higher than 7.5, and the copper layer scorching phenomenon can not be caused, however, the applicant finds that when the reducing agent and the fluxing medium are adopted in the application, and the substrate material is a composite material of glass fiber and epoxy resin, at the moment, the copper deposition rate is too high and the scorching phenomenon can not be caused after the pH of the reducing solution exceeds 11, the applicant unexpectedly finds that when the pH of the reducing agent is 9-11, on the basis of further improving the later-stage copper deposition rate, the better copper deposition rate is maintained, and the copper layer scorching phenomenon can not be caused due to the too high copper deposition rate, and the applicant thinks that the possible reason is that after the pH reducing solution is treated, the expanded substrate material structure distribution and the active catalytic metal have stronger adsorption capacity, the surface roughness of the substrate material enables the copper deposition rate in the later period to be stably carried out, and the structural state of the composite material with the roughness inhibits the excessive copper deposition rate.

(1) placing the substrate treated in the activation step into tap water, and soaking for 1-5 min;

The present invention will be specifically described below by way of examples. It should be noted that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention, and that the insubstantial modifications and adaptations of the present invention by those skilled in the art based on the above disclosure are still within the scope of the present invention.

In addition, the starting materials used are all commercially available, unless otherwise specified.

Example 1

A reducing liquid is prepared by the following raw materials: 0.003 g/L2-methylfuran, 0.007g/L diethylamine, 5g/L boric acid, 10g/L sodium phosphite, and water for the balance.

The substrate is a composite material of glass fiber and epoxy resin, and is of the type FR-4, and is purchased from Zheng energy circuit technology Limited company in Meizhou city.

A method for using a reducing liquid comprises the following steps:

(1) placing the substrate treated in the activation step into tap water, and soaking for 1 min;

(2) mixing sodium phosphite, 2-methylfuran, diethylamine and water according to a weight ratio, adding boric acid to adjust the pH value to 10.5, and obtaining a reducing solution;

(3) and (3) placing the substrate obtained in the step (1) in a reducing solution, wherein the reaction temperature is 35 ℃, and the reaction time is 35s, so as to obtain the substrate subjected to reduction treatment.

FIG. 1 is a backlight effect diagram of copper deposition after the reduction solution treatment.

Example 2

A reducing liquid is prepared by the following raw materials: 0.003 g/L2-methylfuran, 0.007g/L diethylamine, 5g/L boric acid, 5g/L sodium phosphite, and water for the balance.

A method for using a reducing liquid comprises the following steps:

(2) mixing sodium phosphite, 2-methylfuran, diethylamine and water according to a weight ratio, adding boric acid to adjust the pH value to 10, and obtaining a reducing solution;

(3) and (3) placing the substrate obtained in the step (1) in a reducing solution, wherein the reaction temperature is 30 ℃, and the reaction time is 38s, so as to obtain the substrate subjected to reduction treatment.

FIG. 2 is a backlight effect diagram of the copper deposition after the reduction solution treatment.

Example 3

A reducing liquid is prepared by the following raw materials: 0.003 g/L2-methylfuran, 0.007g/L diethylamine, 5g/L boric acid, 0.5g/L sodium phosphite, and water for the balance.

A method for using a reducing liquid comprises the following steps:

(1) placing the substrate treated in the activation step into tap water, and soaking for 3 min;

(2) mixing sodium phosphite, 2-methylfuran, diethylamine and water according to a weight ratio, adding boric acid to adjust the pH value to 10.3, and obtaining a reducing solution;

(3) and (3) placing the substrate obtained in the step (1) in a reducing solution, wherein the reaction temperature is 33 ℃, and the reaction time is 25s, so as to obtain the substrate after reduction treatment.

FIG. 3 is a backlight effect diagram of the copper deposition after the reduction solution treatment.

Example 4

A reducing liquid is prepared by the following raw materials: 0.003 g/L2-methylfuran, 0.007g/L diethylamine, 5g/L boric acid, 10g/L dimethylamine borane, and water to make up the balance.

A method for using a reducing liquid comprises the following steps:

(2) mixing dimethylamine borane, 2-methylfuran, diethylamine and water according to a weight ratio, and adding boric acid to adjust the pH value to 10.5 to obtain a reducing solution;

FIG. 4 is a backlight effect diagram of the copper deposition after the reduction solution treatment.

Example 5

The specific steps of a reducing solution and a using method thereof are the same as example 4, and the difference is that the concentration of dimethylamine borane is 5 g/L.

FIG. 5 is a backlight effect diagram of the copper deposition after the reduction solution treatment.

Example 6

The specific steps of a reducing solution and a using method thereof are the same as example 4, and the difference is that the concentration of dimethylamine borane is 0.5 g/L.

FIG. 6 is a backlight effect diagram of the copper deposition after the reduction solution treatment.

Example 7

A reducing liquid is prepared by the following raw materials: 0.003 g/L2-methylfuran, 0.007g/L diethylamine, 5g/L boric acid, 10g/L sodium borohydride and water to make up the balance.

A method for using a reducing liquid comprises the following steps:

(2) mixing sodium borohydride, 2-methylfuran, diethylamine and water according to a weight ratio, adding boric acid to adjust the pH value to 10.5, and obtaining a reducing solution;

FIG. 7 is a backlight effect diagram of the copper deposition after the reduction solution treatment.

Example 8

The specific steps of a reducing solution and a using method thereof are the same as example 4, and the difference is that the concentration of sodium borohydride is 5 g/L.

FIG. 8 is a backlight effect diagram of the copper deposition after the reduction solution treatment.

Example 9

The specific steps of a reducing solution and a using method thereof are the same as example 4, and the difference is that the concentration of sodium borohydride is 0.5 g/L.

FIG. 9 is a backlight effect diagram of the copper deposition after the reduction solution treatment.

EXAMPLE 10

A reducing liquid is prepared by the following raw materials: 0.003 g/L2-methylfuran, 0.007g/L diethylamine, 5g/L boric acid and water make up the balance.

A method for using a reducing liquid comprises the following steps:

(2) mixing 2-methylfuran, diethylamine and water according to a weight ratio, adding boric acid to adjust the pH value to 10.5, and obtaining a reducing solution;

FIG. 10 is a backlight effect diagram of the copper deposition after the reduction solution treatment.

And (3) performance testing:

the chemical copper plating process comprises the following steps:

the substrate was treated in 240L of a mixed solution containing 10 vol% propylene glycol ethyl ether and 35g/L sodium hydroxide, which was obtained from Guangdong Shuichi Co., Ltd., model SCC-A01H, at 80 ℃ for 6 min. Washing with cold water at 25 deg.C for 1 min; the substrate was then treated in 550L of 50-60g/L alkaline oxidizing agent-containing solution (available from Guangdong Shuichi technologies, Inc., model SCC-A02) at 80 ℃ for 12min to achieve a pH of 12. Washing with cold water for 1 min; the substrate was placed in 100ml/L SCC-A03H, and 90ml sulfuric acid (50% sulfuric acid) was added to prepare a reaction solution, which was obtained from Kagaku Kogyo Co., Ltd., model No. SCC-A03H, and treated at 50 ℃ for 1 min. And washing with cold water for 1 min. The substrate was then treated in 20ml/L of a cationic surfactant-containing solution (available from Guangdong Shuichi technologies, Inc. under the model SCC-A04H) at 50 ℃ for 1min at pH 11. And washing with cold water for 1 min. The activation step was carried out by further treating the substrate in 30ml/L of a solution containing sodium hydroxide or sodium carbonate (available from Guangdong Shuichi Co., Ltd., model SCC-A06H) at 50 ℃ for 45 seconds to obtain a pH of 9. Soaking in cold water for 1 min.

The use method of the reducing solution according to the inventionThe substrate is processed, and the reducing liquid is prepared according to the preparation method provided by the invention. Soaking in cold water for 1 min. Finally, the substrate is plated with copper chemically for 30min at 34 ℃. (1) Copper deposition rate: the difference Δ m between the substrate before and after plating was measured as m (after) -m (before), and the surface area S (25 cm) of the substrate was measured²) The density of the plating layer is rho (8.92 g/cm)³) The electroless plating elapsed time T was measured, and the velocity V ═ Δ m/(S ×. ρ × T) was calculated using the formula.

(2) Backlight grade: cutting the chemically plated substrate from the side surface, exposing the coating of the through hole, randomly selecting the through hole coating with the thickness of 1mm, observing the side coating of the substrate under a metallographic optical microscope with the magnification of 50X, and measuring the coating thickness by adopting a European backlight classification table. The backlight level shows the effect of the reducing liquid on the backlight.

The examples were tested according to the above criteria and the results are shown in table 1.

TABLE 1

	Copper deposition rate/mum/h	Backlight grade
			Example 1	0.5	7
Example 2	0.75	9.5
			Example 3	0.78	9
Example 4	0.55	7.5
			Example 5	0.73	9.5
Example 6	0.79	9
			Example 7	0.54	8
Example 8	0.72	10
			Example 9	0.8	9.5
Example 10	0.45	5

It can be seen from table 1 that the copper deposition rate of 0.35-0.95 can be achieved by using 0.5 wt% -1 wt% of three reducing agents, namely sodium phosphite, sodium borohydride and dimethyl borane, and the backlight grade can be nine or more.

Claims

1. A reducing liquid, which is characterized by comprising a solvent and 0.5-5 wt% of a reducing agent; the reducing agent is selected from a combination of an organic reducing agent and an inorganic reducing agent, and the organic reducing agent is a nitrogen-containing compound.

2. The reducing solution according to claim 1, wherein the nitrogen-containing compound has a structure of volume ratio

3. The reducing fluid according to claim 1, wherein the inorganic reducing agent is selected from one or more of a phosphite, a borohydride, and a borane in combination.

4. The reducing solution according to claim 1, wherein the reducing agent accounts for 0.5-4.5 wt% of the reducing solution.

5. The reducing solution of claim 1, further comprising 0.001-0.1 wt% of a cosolvent and a pH adjusting agent.

6. The reducing solution according to claim 1 or 5, wherein the cosolvent is selected from one or more of aminoalkanes, furans, ethers, alcohols, and ketones.

7. The reducing solution according to claim 6, wherein the furan-like substance is one selected from alkyl furan, phenyl furan, and 2-methyl furan.

8. The reducing solution according to claim 5, wherein the weight ratio of the reducing agent to the cosolvent is 1: (1000-50).

9. The reducing solution of claim 5, wherein the pH of the reducing solution is 9-11.

10. A method of using the reducing liquid according to any one of claims 5 to 9, comprising the steps of:

(2) mixing a reducing agent, an auxiliary agent and a solvent according to the weight part ratio, and adding a pH regulator to regulate the pH to 9-11 to obtain a reducing solution;