CN111962109A - Acid copper additive and preparation method thereof - Google Patents

Abstract

The invention discloses an acid copper additive and a preparation method and application thereof, wherein the acid copper additive comprises the following components in parts by mass: 15-20% of 2-mercaptobenzimidazole, 5-9% of thioacetic acid alkyl ester, 2-6% of sodium dithiopropane sulfonate, 2-5% of dithiocarbamate, 1-5% of N, N-diethyl propylamine, 1-5% of N-butyl-N-methyl piperidine bromide, 1-6% of potassium hexacyanoferrate, 6-10% of fatty alcohol-polyoxyethylene ether and the balance of water. The acid copper additive has the advantages of strong filling capacity of pores with small pore diameters, uniform plating layer, strong deep plating capacity and leveling capacity, and good brightness of the obtained electrodeposited copper.

Description

Acid copper additive and preparation method thereof

Technical Field

The invention relates to the technical field of electroplating, in particular to an acid copper additive for deep hole electroplating and a preparation method thereof.

Background

The printed circuit board is one of important parts in the electronic industry, is widely applied to aspects of social life, and is used as a carrier of an integrated circuit from a digital product in daily life, a household appliance, a numerical control machine tool and an artificial intelligence device in industrial production, and then an artificial satellite and a manned spacecraft in aerospace. The holes on the printed board are divided into three types, namely buried holes, blind holes and through holes, and the buried holes are positioned in the printed board and cannot be seen from the surface; the blind holes are holes which do not penetrate through the substrate and can be seen from the outer surface of one side of the printed board; vias are holes through the substrate, visible from both the top and bottom layers of the printed board.

In the manufacture of printed circuit boards, these holes, which are on the order of microns in diameter, need to be filled using a copper plating process. The additive has great influence on the performance of the copper electroplating, the quality of acid copper electroplating directly influences subsequent processing and use, and the strength and the conductivity of a plating layer can be ensured only if the thickness of an acid copper plating layer on a plate surface and in a hole is uniform, so that the deep plating and leveling capability of the plating solution needs to be enhanced. With the development of printing plates towards high precision, higher requirements are put on the copper plating industry. The existing acid copper additive is classified into brightener, leveling agent and the like according to the function, and various additives are various, the addition operation is complex, and the process is difficult to control. When the hole with smaller aperture is filled, the common acid copper additive can not meet the requirements of deep plating and leveling capability, is difficult to fill effectively, and is not suitable for a high-density and high-precision small-aperture printing plate. There is therefore a need to further develop acid copper additives to achieve a smooth and even copper deposit.

Disclosure of Invention

The invention aims to provide an acid copper additive suitable for deep hole electroplating.

In order to solve the technical problems, the invention provides the following technical scheme:

the invention provides a copper acid additive in a first aspect, which comprises the following components in parts by mass:

the remaining component is water.

In the copper acid additive, 2-mercapto benzimidazole, thioacetic acid acetyl alkyl ester, dithio propane sodium sulfonate and dithiocarbamate can generate synergistic action, and the nucleation speed is accelerated through competitive adsorption; meanwhile, the copper ions can be adsorbed on crystal faces with higher active points, so that the reaction of the metal ions at the active points is slowed down, the deposition of copper can be accelerated, and the crystals are fine. Potassium hexacyanoferrate, as an inorganic additive, diffuses readily into the micropores, its concentration being higher in the middle of the pores, accelerating the deposition there. N, N-diethyl propyne amine and N-butyl-N-methyl piperidine bromide can be selectively adsorbed on the convex part of the microscopic surface or the area with larger current density due to special functional groups, so that the reduction of copper ions at the position is inhibited, the uniformity of the thickness of a plating layer in a hole is improved, and the quality of the plating layer is improved.

Further, the acid copper additive comprises the following components in parts by mass:

the remaining component is water.

Further, the acid copper additive comprises the following components in parts by mass:

the remaining component is water.

In a second aspect, the present invention provides a method for preparing the copper acid additive according to the first aspect, including:

weighing the components according to the formula ratio, mixing, and stirring until the components are completely dissolved to obtain the copper acid additive.

In a third aspect, the present invention provides an electroplating bath comprising the copper acid additive of the first aspect.

The fourth aspect of the invention provides the use of the copper acid additive of the first aspect in deep hole plating.

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

the acid copper additive provided by the invention has the advantages that the filling capacity of pores with small pore diameters is high, the plating layer is uniform, the deep plating capacity and the leveling capacity are high, the brightness of the obtained electrodeposited copper is good, the problems that the existing copper plating additive is various in types and difficult to control in dosage and the like are solved, and the integration of the composite additive is realized.

Drawings

Fig. 1 is a schematic position diagram of test points after deep hole electroplating on a PCB, wherein a, b, c, d, e, and f are all test points.

Detailed Description

The present invention is further described below in conjunction with specific examples to enable those skilled in the art to better understand the present invention and to practice it, but the examples are not intended to limit the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Example 1

This example provides a copper acid additive, which has the following formulation:

the remaining component is water.

The components are mixed to prepare the acid copper additive. Then, 230g/L copper sulfate pentahydrate (copper source), 55g/L sulfuric acid and 70ppm of chloride ion were mixed as a base acid copper solution, and 5ml/L of the additive prepared above was added. The prepared plating solution is used for depositing a copper plating layer on a printing plate with a blind hole with the aperture of 30 mu m and the hole depth of 70 mu m. The temperature of the plating solution is 25 ℃, and the current density is 2A/dm²And the electrodeposition time is 1 h.

Example 2

This example provides a copper acid additive, which has the following formulation:

the remaining component is water.

The components are mixed to prepare the acid copper additive. Then, 235g/L of copper sulfate pentahydrate, 50g/L of sulfuric acid and 80ppm of chloride ion were mixed as a basic acid copper solution, and 5ml/L of the additive prepared above was added. The prepared plating solution is used for depositing a copper plating layer on a printing plate with a blind hole with the aperture of 35 mu m and the hole depth of 80 mu m. The temperature of the plating solution is 25 ℃, and the current density is 2.5A/dm²And the electrodeposition time is 1 h.

Example 3

This example provides a copper acid additive, which has the following formulation:

the remaining component is water.

Mixing the above components to obtain the acid copper additive. Then, 240g/L copper sulfate pentahydrate, 52g/L sulfuric acid and 75ppm chloride ion were mixed as a base acid copper solution, and 5ml/L of the additive prepared above was added. The prepared plating solution is used for depositing a copper plating layer on a printing plate with a blind hole with the aperture of 37 mu m and the hole depth of 75 mu m. The temperature of the plating solution is 25 ℃, and the current density is 2A/dm²And the electrodeposition time is 1 h.

Example 4

This example provides a copper acid additive, which has the following formulation:

the remaining component is water.

The components are mixed to prepare the acid copper additive. Then, 234g/L copper sulfate pentahydrate, 53g/L sulfuric acid and 75ppm of chloride ion were mixed as a base acid copper solution, and 5ml/L of the additive prepared above was added. The prepared plating solution is used for depositing a copper plating layer on a printing plate with a blind hole with the aperture of 37 mu m and the hole depth of 75 mu m. The temperature of the plating solution is 25 ℃, and the current density is 2A/dm²And the electrodeposition time is 1 h.

Example 5

This example provides a copper acid additive, which has the following formulation:

the remaining component is water.

The components are mixed to prepare the acid copper additive. Then, 237g/L of copper sulfate pentahydrate, 55g/L of sulfuric acid and 70ppm of chloride ion were mixed as a base acid copper solution, and 5ml/L of the additive prepared above was added. The prepared plating solution is used for depositing a copper plating layer on a printing plate with a blind hole with the aperture of 40 mu m and the hole depth of 70 mu m. The temperature of the plating solution is 25 ℃, and the current density is 2.5A/dm²And the electrodeposition time is 1 h.

Comparative example 1

237g/L of copper sulfate pentahydrate, 55g/L of sulfuric acid and 70ppm of chloride ion were mixed as a base acid copper solution. The prepared plating solution is used for depositing a copper plating layer on a printing plate with a blind hole with the aperture of 40 mu m and the hole depth of 70 mu m. The temperature of the plating solution is 25 ℃, and the current density is 2A/dm²And the electrodeposition time is 1 h.

Comparative example 2

234g/L copper sulfate pentahydrate, 53g/L sulfuric acid and 75ppm chloride ion were mixed as a base acid copper solution. The prepared plating solution is used for depositing a copper plating layer on a printing plate with a blind hole with the aperture of 37 mu m and the hole depth of 75 mu m. The temperature of the plating solution is 25 ℃, and the current density is 2A/dm²And the electrodeposition time is 1 h.

Examples of the experiments

The plating liquids prepared in examples 1 to 5 and comparative examples 1 to 2 were examined for throwing power:

selecting an area on the PCB surface, milling the area into small blocks, filling glue after tin bleaching, polishing and polishing to the diameter of the through hole, carrying out micro-etching on the polished plane by using a micro-etching solution, and then measuring the thickness of the electroplated copper layer under a metallographic microscope. The aperture reads 4 data and the hole reads 2 data, and in order to ensure the quality of slicing, the size of the upper and lower apertures is measured at the same time, as shown in fig. 1.

The throwing power of each plating solution was then calculated, and the results are shown in Table 1.

Wherein, the calculation formula of the deep plating capacity is as follows:

_a、_d、_c、_f-the thickest thickness (mm) of the PCB orifice

_b、_eThe thinnest thickness (mm) in the PCB hole.

TABLE 1 throwing power of plating solutions of examples 1 to 5 and comparative examples 1 to 2

Example 1

Example 2

Example 3

Example 4

Example 5

Comparative example 1

Comparative example 2

100％

98％

97％

100％

100％

47％

45％

As is clear from the results of Table 1, the plating solutions of examples 1 to 5 exhibited much higher throwing power than those of comparative examples 1 to 2, indicating that the plating layers of examples 1 to 5 were more uniform. Therefore, the acid copper additive of the invention is suitable for deep hole electroplating.

The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.

Claims (6)

1. The acid copper additive is characterized by comprising the following components in parts by mass:

the remaining component is water.

2. The acid copper additive as claimed in claim 1, wherein the acid copper additive comprises the following components by mass:

the remaining component is water.

3. The acid copper additive as claimed in claim 1, wherein the acid copper additive comprises the following components by mass:

the remaining component is water.

4. The method of preparing the acid copper additive according to any one of claims 1-3, comprising:

weighing the components according to the formula ratio, mixing, and stirring until the components are completely dissolved to obtain the copper acid additive.

5. An electroplating bath comprising the copper acid additive according to any one of claims 1 to 3.

6. Use of a copper acid additive according to any of claims 1 to 3 in deep hole plating.