Electroplating cobalt plating solution for filling X-type through hole of printed circuit and application of electroplating cobalt plating solution

Abstract

The invention provides an electroplating cobalt plating solution for filling an X-type through hole of a printed circuit and application, the electroplating cobalt plating solution is used for the printed circuit and comprises cobalt sulfate heptahydrate, boric acid, sodium sulfate and sodium chloride, and an additive comprises one or more of adenine nucleoside, adenine, 6-mercaptopurine, 2-thioxanthine and 6-chloropurine. The high-quality filling effect is achieved, meanwhile, the average thickness increase of the surface cobalt is controlled to be smaller than 2 micrometers, the depression degree is controlled to be smaller than 2 micrometers, and the filling degree and the surface cobalt thickness control capacity are in the leading position in the similar invention and the existing production technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of additives for electroplating cobalt on printed circuit boards, and particularly relates to an electroplating cobalt plating solution for filling X-shaped vias in printed circuits and its application. Background Art

[0002] As a core component in electronic devices, printed circuit boards play a crucial role in integrating various components and achieving electrical connections between them. With the continuous increase in their integration density and number of layers, the requirements for the reliability of electrical connections are becoming increasingly stringent, especially the demand for filling high-quality X-shaped laser vias (referred to as X-shaped vias) is becoming more prominent.

[0003] X-shaped vias are formed by the double-sided laser drilling technology of the board, and their characteristics are that the middle aperture is small, while the orifice is relatively wide. To achieve high-quality filling of X-shaped vias, it is necessary to ensure that the holes are completely filled with cobalt without voids, and at the same time, the thickness of the outer plating layer remains stable, and the surface depression is slight or almost invisible. The filling process follows the following steps: First, with the synergistic effect of various additives, the cobalt deposition rate in the holes, especially in the middle area of the X-shaped vias, is significantly faster than that outside the holes, and a connected "bridge" composed of a cobalt plating layer is formed first. Subsequently, the X-shaped via is divided into two structures similar to blind holes, and these two blind holes respectively undergo a superfilling process from bottom to top under the regulation of additives, and finally the high-quality filling goal of the X-shaped via is successfully achieved.

[0004] To achieve a super conformal filling effect from the inside out without voids, adding organic additives to the cobalt plating solution is a necessary step. In contrast, the traditional electroplated copper interconnect process relies on three additives: an accelerator to accelerate metal deposition at the bottom of the hole or trench, an inhibitor to control the growth rate of copper on the sidewalls and the surface, and a planarizer to prevent excessive deposition at the orifice and promote surface flatness. However, during the electroplating of cobalt, only additives with an inhibitory effect are sufficient to achieve super conformal filling from bottom to top, and there is no need to add an accelerator additionally.

[0005] After the X-shaped via filling process is completed, the problem of excessive surface cobalt often occurs, which is not conducive to the subsequent etching process of fine lines. However, by adjusting the types of additives in the cobalt plating solution, the thickness of the surface cobalt can be further reduced, thus creating more favorable conditions for the manufacture of subsequent fine lines.

[0006] For the above reasons, the present invention proposes an additive system that can be applied to high-quality cobalt filling of X-shaped vias, which can meet the actual needs in printed circuit manufacturing. Summary of the Invention

[0007] The purpose of the present invention is to provide an electroplating cobalt plating solution for filling X-shaped vias in printed circuits and its application.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] An electroplating cobalt plating solution for X-shaped via filling of printed circuits, the plating solution includes one of cobalt sulfate heptahydrate and cobalt sulfate, one of sodium chloride and cobalt chloride, boric acid, sodium sulfate, and an organic additive;

[0010] The concentration of the cobalt sulfate heptahydrate is 50 g / L - 100 g / L, and the concentration of cobalt sulfate is 30 g / L - 60 g / L; the concentration of boric acid is 10 g / L - 40 g / L, the concentration of sodium sulfate is 75 g / L - 150 g / L, the concentration of sodium chloride is 60 mg / L - 132 mg / L; the concentration of cobalt chloride is 150 mg / L - 300 mg / L;

[0011] The organic additive is one or several of adenosine, adenine, 6-mercaptopurine, 2-thioxanthine, 6-chloropurine, and the concentration of the organic additive is 10 mg / L - 100 mg / L.

[0012] As a preferred mode, when the plating solution is used for X-shaped via filling, the concentration of the cobalt sulfate heptahydrate is 70 g / L - 100 g / L, and the concentration of cobalt sulfate is 30 g / L - 60 g / L; the concentration of boric acid is 20 g / L - 40 g / L, the concentration of sodium sulfate is 80 g / L - 120 g / L, the concentration of sodium chloride is 60 mg / L - 132 mg / L, and the concentration of cobalt chloride is 150 mg / L - 300 mg / L;

[0013] As a preferred mode, when the plating solution is used for X-shaped via filling, the upper and lower hole diameters of the X-shaped via are 50 μm - 80 μm, the middle hole diameter is 25 μm - 40 μm, and the dielectric thickness of the copper clad laminate is 130 μm - 170 μm. The preferred dielectric material is glass cloth reinforced epoxy resin.

[0014] The second object of the present invention is to provide an application of an electroplating cobalt plating solution in printed circuits. The plating solution is used on an X-shaped via board of printed circuits, and the filling of the via is realized by the method of electro-depositing cobalt, so as to achieve interconnect electroplating. The definition of interconnect electroplating is: using the principle of electrochemistry, under the action of an electric field, metal ion cations in the electrolyte move towards the cathode material to be plated and obtain electrons to undergo a reduction reaction, and the metal is deposited on a specific patterned area to form a metal interconnect structure, realizing the process of electrical connection inside the component or with the external circuit.

[0015] As a preferred mode, for the application of the electroplating cobalt plating solution, when the plating solution is used for X-shaped via filling, the electroplating process includes the following steps:

[0016] Step 1, degreasing, micro-etching, and pre-impregnation treatment are carried out on the copper clad laminate with X-shaped vias;

[0017] Step 2: Pour the prepared plating solution into the plating bath. Use the copper clad laminate with X-shaped vias treated in Step 1 as the cathode, and use an insoluble titanium mesh as the anode. Perform electroplating using a DC power supply, where the current density is 0.1 A / dm 2 ~1 A / dm 2 , the temperature of the plating solution is 22 ± 3 °C, and the electroplating time is 1 - 6 h. The reason for setting the process parameters like this is that under these conditions, while ensuring the via filling effect, it can save electroplating time and ensure repeatability.

[0018] The cobalt sulfate heptahydrate can be replaced by cobalt sulfate. When cobalt sulfate is used, the concentration of cobalt sulfate in the plating solution can be converted according to the same molar concentration of the cobalt sulfate heptahydrate used above.

[0019] The sodium chloride can be replaced by cobalt chloride. When cobalt chloride is used, the concentration of cobalt chloride in the plating solution can be converted according to the same molar concentration of chloride ions in the sodium chloride used above.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] An electroplating cobalt plating solution additive system for filling X-shaped vias in printed circuits provided by the present invention has a simple molecular structure of the additive; when the plating solution additive system provided by the present invention is applied to filling X-shaped vias, while obtaining a high-quality filling effect, the average thickening of the surface cobalt is controlled to be less than 2 μm, and the depression is less than 2 μm. Among them, the control ability of the surface cobalt thickness is in the leading position among similar inventions and existing production technologies. At the same time, the obtained cobalt surface is flat and can meet the needs of industrial production. Description of the Drawings

[0022] Figure 1 Is the metallographic diagram of the X-shaped via slice obtained in Example 1;

[0023] Figure 2 Is the schematic diagram of the cobalt filling process in the X-shaped via under the action of the organic additive in Example 1; Detailed Embodiments

[0024] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] Figure 1 Is the metallographic diagram of the X-shaped via slice obtained in Example 1; From Figure 1It can be seen that the organic additive is concentrated in the area outside the X-shaped holes to inhibit cobalt deposition. After 1 hour of DC electroplating, a butterfly structure is formed in the X-shaped through-holes with cobalt metal, and the deposition layer thickness outside the holes is less than 1 μm. After 4 hours, the X-shaped through-holes with a filling rate ≥ 90% are filled, and at this time, the deposition layer thickness outside the holes is 1.2 μm. After the filling is finally completed, the cobalt thickening and depression at the back are both less than 2 μm.

[0026] Figure 2 It is a schematic diagram of the cobalt filling process in the X-shaped through-holes under the action of the organic additive in Example 1; It can be seen from Figure 2 that under the action of electrostatic force, the organic additive is adsorbed on the cathode surface. Due to the difference in liquid mobility and the low concentration of the additive in the holes, it is preferentially adsorbed on the electrode surface outside the holes, making Co 2+ first reduced to Co 0 to form a butterfly structure. Although the electrode outside the holes is strongly inhibited, the deposition rate is low and the layer thickness is less than 1 μm. However, as the deposition progresses, the increase in the curvature of the cobalt deposition layer brings an increase in the surface mobility and the adsorption tendency of the additive, inhibiting the deposition of Co 2+ in the holes to reduce the rate, and finally complete filling under the action of the additive.

[0027] The embodiment provides an electroplating cobalt plating solution for filling X-shaped through-holes in printed circuits. The plating solution includes one of cobalt sulfate heptahydrate and cobalt sulfate, one of sodium chloride and cobalt chloride, boric acid, sodium sulfate, and an organic additive;

[0028] The concentration of the cobalt sulfate heptahydrate is 50 g / L - 100 g / L, and the concentration of the cobalt sulfate is 30 g / L - 60 g / L; the concentration of the boric acid is 10 g / L - 40 g / L, the concentration of the sodium sulfate is 75 g / L - 150 g / L, the concentration of the sodium chloride is 60 mg / L - 132 mg / L; the concentration of the cobalt chloride is 150 mg / L - 300 mg / L;

[0029] In some embodiments, the organic additive is one or several of adenosine, adenine, 6-mercaptopurine, 2-thioxanthine, 6-chloropurine, and the concentration of the organic additive is 10 mg / L - 100 mg / L.

[0030] In some embodiments, when the plating solution is used for filling X-shaped through-holes, the concentration of the cobalt sulfate heptahydrate is 70 g / L - 100 g / L, and the concentration of the cobalt sulfate is 30 g / L - 60 g / L;; the concentration of the boric acid is 20 g / L - 40 g / L, the concentration of the sodium sulfate is 80 g / L - 120 g / L, the concentration of the sodium chloride is 60 mg / L - 132 mg / L, and the concentration of the cobalt chloride is 150 mg / L - 300 mg / L;

[0031] In some embodiments, when the plating solution is used for filling X-shaped vias, the upper and lower diameters of the X-shaped vias are 50 μm - 80 μm, the middle diameter is 25 μm - 40 μm, and the dielectric thickness is 130 μm - 170 μm.

[0032] In some embodiments, when the plating solution is used for filling X-shaped vias, the electroplating process includes the following steps:

[0033] Step 1: Degrease, micro-etch, and pre-dip the copper clad laminate with X-shaped vias.

[0034] Step 2: Pour the prepared plating solution into the plating tank. Use the copper clad laminate with X-shaped vias treated in Step 1 as the cathode and an insoluble titanium mesh as the anode, and perform electroplating using a DC power supply. Among them, the current density is 0.1 A / dm2 - 1 A / dm2. In some embodiments, the temperature of the plating solution is 22 ± 3 °C, and the electroplating time is 1 - 6 h. The reason for setting the process parameters like this is that under these conditions, the via filling effect can be guaranteed while saving electroplating time and ensuring repeatability.

[0035] Example 1

[0036] In the plating solution for filling X-shaped vias of the printed circuit in Example 1, the basic plating solution is: cobalt sulfate heptahydrate with a concentration of 84 g / L, boric acid with a concentration of 35 g / L, sodium sulfate with a concentration of 100 g / L, and sodium chloride with a concentration of 66 mg / L.

[0037] Adenosine is used as a cobalt plating additive with a concentration of 50 mg / L.

[0038] The plating solution is used for X-shaped via copper clad laminates with upper and lower diameters of 80 μm, a middle diameter of 40 μm, and a dielectric layer thickness of 160 μm.

[0039] The printed circuit provided in Example 1 for the X-shaped via filling process specifically includes the following steps:

[0040] Step 1: Prepare the plating solution:

[0041] 1.1 Mix cobalt sulfate heptahydrate, sodium sulfate, and sodium chloride evenly to obtain 1.5 L of the basic plating solution; among them, the concentration of cobalt sulfate heptahydrate is 84 g / L, the concentration of boric acid is 35 g / L, the concentration of sodium sulfate is 100 g / L, and the concentration of sodium chloride is 66 mg / L.

[0042] 1.2 Add adenosine as an additive to the basic plating solution obtained in Step 1.1 and mix evenly to obtain the plating solution; finally, the concentration of adenosine is 50 mg / L.

[0043] Step 2: Perform pretreatment on the copper clad laminate with X-shaped vias, including degreasing, micro-etching, and pre-dipping.

[0044] 2.1 Degreasing:

[0045] The degreasing solution consists of 20 g / L of sodium hydroxide, 1 g / L of sodium dodecylbenzenesulfonate, 3 g / L of sodium carbonate, 5 g / L of trisodium phosphate dodecahydrate and deionized water. Then, the copper clad laminate with X-shaped vias is immersed in the degreasing solution for 5 min;

[0046] 2.2 Micro-etching:

[0047] The micro-etching solution consists of 5% sodium sulfate by mass fraction, 5% sodium persulfate by mass fraction and deionized water. Then, the copper clad laminate obtained after the treatment in step 2.1 is immersed in the micro-etching solution for 30 s;

[0048] 2.3 Pre-impregnation:

[0049] The pre-impregnation solution consists of 5% sulfuric acid by mass fraction and deionized water. Then, the copper clad laminate obtained after the treatment in step 2.2 is immersed in the pre-impregnation solution for 5 min;

[0050] Step 3: Electroplating and filling cobalt in X-shaped vias:

[0051] Pour the plating solution prepared in step 1 into the plating bath. Fix the copper clad laminate with X-shaped vias after the pretreatment in step 2 directly in the middle of the plating bath as the cathode, and use insoluble titanium meshes as the anode plates on both sides. Perform electroplating with a DC power supply. Among them, the current density is 0.5 A / dm 2 , the temperature of the plating solution is 22 ± 3 °C, the air stirring speed is 1.5 L / min, and the electroplating time is 4 h.

[0052] Wash the electroplated copper clad laminate obtained in step 3 and dry it. After making slices, observe and take pictures under a metallurgical microscope. Measure the depression degree and the surface cobalt thickness. The depression degree refers to the depth of the depression from the cobalt at the outside of the hole to the center of the hole, and the surface cobalt thickness refers to the thickness from the cobalt at the outside of the hole to the copper plating layer outside the hole.

[0053] Figure 1 Figure; shows the longitudinal sectional view of the X-shaped via observed by a metallurgical microscope after electroplating and filling in Example 1. The measurement results show that the depression degree of the X-shaped via obtained by using this formula does not exceed 2 μm, and the average value of the surface cobalt thickness does not exceed 2 μm.

[0054] Figure 2 Figure; shows the schematic diagram of the growth and filling process of cobalt metal under the action of organic additives during the electroplating and filling of the X-shaped via in Example 1.

[0055] The above embodiments are preferred implementation methods of the present invention for illustrating the present invention. However, the present invention is not limited to the specific details in the above embodiments. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention.

[0056] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those of ordinary skill in the art in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A cobalt electroplating solution for filling X-shaped through holes in printed circuits, characterized in that: The plating solution comprises one of cobalt sulfate heptahydrate and cobalt sulfate, one of sodium chloride and cobalt chloride, boric acid, sodium sulfate, and an organic additive; The concentration of cobalt sulfate heptahydrate is 50g / L-100g / L, the concentration of cobalt sulfate is 30g / L-60g / L; the concentration of boric acid is 10g / L-40g / L, the concentration of sodium sulfate is 75g / L-150g / L, the concentration of sodium chloride is 60mg / L-132mg / L; the concentration of cobalt chloride is 150mg / L-300mg / L; The organic additive is one or more of adenine nucleoside, adenine, 6-mercaptopurine, 2-thioxanthine, and 6-chloropurine, and the concentration of the organic additive is 10 mg / L-100 mg / L.

2. The electroplating cobalt plating solution for filling X-shaped through holes in printed circuits according to claim 1, characterized in that: When the plating solution is used for X-type through-hole filling, the concentration of cobalt sulfate heptahydrate is 70g / L-100g / L, the concentration of cobalt sulfate is 30g / L-60g / L; the concentration of boric acid is 20g / L-40g / L, the concentration of sodium sulfate is 80g / L-120g / L, the concentration of sodium chloride is 60mg / L-132mg / L, and the concentration of cobalt chloride is 150mg / L-300mg / L.

3. The electroplating cobalt plating solution for filling X-shaped through holes of printed circuits according to claim 1, characterized in that: When the plating solution is used for filling an X-shaped through hole, the upper and lower apertures of the X-shaped through hole are 50 μm-80 μm, the middle aperture is 25 μm-40 μm, and the dielectric thickness of the copper-clad plate is 130 μm-170 μm.

4. Application of a cobalt electroplating solution according to claim 1 or 2 in printed circuits, characterized in that: The plating solution is used for printing circuits on X-shaped through-hole boards, and the through-holes are filled by electro-depositing cobalt, thereby realizing interconnection electroplating.

5. The use of the electroplating cobalt plating solution in a printed circuit according to claim 3, characterized in that: When the plating solution is used for X-type through-hole filling, the electroplating process includes the following steps: Step 1, degreasing, micro-etching and pre-preg treatment of the copper clad laminate with X-shaped through holes; Step 2: Pour the prepared plating solution into the plating tank, use the copper-clad laminate with X-shaped through holes treated in step 1 as the cathode, use the insoluble titanium mesh as the anode, and use a DC power supply for electroplating, wherein the current density is 0.1A / dm 2 ~1A / dm 2 , the plating solution temperature is 22±3℃, and the electroplating time is 1 to 6 hours.

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