KR102618832B1 - Copper-tin alloy layer forming method - Google Patents

Abstract

The present invention includes the steps of (A) forming a tin plating layer on a copper substrate; (B) heat treating the tin plating layer to form a copper-tin alloy layer; (C) immersing the copper-tin alloy layer in a tin stripping solution containing organosulfonic acid to selectively peel off the pure tin layer; and (D) forming a silane layer on the copper-tin alloy layer. According to the present invention, a copper-tin alloy layer with low roughness and excellent peel strength is formed. can be formed.

Description

Method of forming copper-tin alloy layer {COPPER-TIN ALLOY LAYER FORMING METHOD}

The present invention relates to a method of forming a copper-tin alloy layer, and in particular, to a method of forming a copper-tin alloy layer with excellent peel strength through heat treatment.

Copper foil oxide technology is a technology that forms roughness by oxidizing the surface of copper foil to improve adhesion to the inner layer substrate when forming MLB (multi layer board). Traditionally, there are brown oxidation and black oxidation technologies that form fine copper oxide particles. . The existing process increases the physical bonding force by increasing the surface roughness, but the rough surface increases transmission signal loss, making it difficult to apply to high-frequency PCBs.

In addition, when organic substances and foreign substances remain in the oxide layer, delamination defects in which copper foil is not completely adhered and lifting occurs due to insufficient adhesion between the prepreg adhesive layer and copper foil during lamination molding have become a major issue.

Accordingly, research was conducted to chemically bond the tin alloy layer and resin by forming a tin alloy layer on copper foil and then forming a chemical coupling layer using a silane coupling agent, etc. In this case, tin stripper was used or various peeling methods were used. A tin alloy layer is formed through this method.

In this regard, Japanese Patent Laid-Open No. 2008-184675 proposes a method of forming a tin surface layer through a stripper consisting of an inorganic acid such as sulfuric acid or nitric acid after pre-treating a substrate on which a tin layer is formed with a strong base, Japanese Patent Laid-Open No. 2012-052205 proposes a method of treating a tin alloy layer with an aqueous alkaline solution stripping solution containing hydrogen peroxide as a simple and low-cost stripping method, and recovering and reprocessing the stripping solution.

However, in the method of forming a copper-tin alloy layer using a stripper, a new method of manufacturing a copper-tin alloy layer that can minimize roughness and improve peeling strength at the same time is required.

Japanese Patent Publication No. 2008-184675 (published on August 14, 2008) Japanese Patent Publication No. 2012-052205 (published on March 15, 2012)

The method of forming a copper-tin alloy layer of the present invention was devised to solve the above problems, comprising the steps of (A) forming a tin plating layer on a copper substrate; (B) heat treating the tin plating layer to form a copper-tin alloy layer; (C) immersing the copper-tin alloy layer in a tin stripping solution containing organosulfonic acid to selectively peel off the pure tin layer; and (D) forming a silane layer on the copper-tin alloy layer.

In addition to the clear objectives described above, the present invention may also aim to achieve other objectives that can be easily derived by a person skilled in the art from this objective and the overall description of the present specification.

In order to achieve the above-described purpose, the method of forming a copper-tin alloy layer of the present invention,

(A) forming a tin plating layer on a copper substrate;

(B) heat treating the tin plating layer to form a copper-tin alloy layer;

(C) immersing the copper-tin alloy layer in a tin stripping solution containing organosulfonic acid to selectively peel off the pure tin layer; and

(D) forming a silane layer on the copper-tin alloy layer.

In addition, a process of pre-treating the copper substrate before forming the tin plating layer may be further included, and the pre-treatment may include an immersion degreasing process, a primary water washing process, an acid washing process, and a secondary water washing process.

Additionally, the immersion degreasing process may involve immersing the acid in an acid degreaser at 25 to 35°C for 0.5 to 10 minutes, 0.5 to 5 minutes, 1 to 8 minutes, or 1 to 5 minutes.

Additionally, the acid degreasing agent may include sulfuric acid.

Additionally, the pickling process may involve treatment in an acidic solution at 20 to 30° C. for 30 to 90 seconds.

Additionally, the acidic solution may be a 5 to 20% (w/w), 5 to 15% (w/w), or 8 to 12% (w/w) sulfuric acid solution.

Additionally, the heat treatment may be performed at 90 to 130°C, 100 to 120°C, or 105 to 115°C.

Additionally, the heat treatment may be performed for 30 to 150 seconds, 40 to 120 seconds, or 50 to 100 seconds.

In addition, the step of washing the tin plating layer with water before the heat treatment may be further included.

Additionally, step C may involve immersing the copper-tin alloy layer in a tin stripper for 10 to 120 seconds, 20 to 105 seconds, or 30 to 90 seconds.

And, step C may be performed at 20 to 40 °C, 25 to 35 °C, or 28 to 32 °C.

Additionally, the tin stripper may contain 10 to 50 g/L, 15 to 40 g/L, or 20 to 30 g/L of organosulfonic acid.

In addition, the organosulfonic acid is represented by RSO ₃ H, and R may be a saturated hydrocarbon having 1 to 6 carbon atoms, 1 to 3 carbon atoms, or 1 to 2 carbon atoms.

Additionally, the tin stripper may contain an oxidizing agent.

Additionally, the oxidizing agent may be an aromatic compound having a nitro group.

In addition, the tin stripping solution may include 100 parts by weight of organosulfonic acid and 0.5 to 10 parts by weight, 2 to 8 parts by weight, or 4 to 6 parts by weight of an oxidizing agent.

Additionally, step D may involve forming a silane layer by applying an amine-based silane coupling agent.

In addition, the amine-based silane coupling agent may include N-(3-(Trimethoxysilyl)propyl-1,2-ethanediamine). .

And, step D may be performed at 15 to 50 °C, 20 to 40 °C, or 25 to 35 °C.

And, step D may be performed for 20 to 60 seconds, 25 to 50 seconds, or 25 to 40 seconds.

Additionally, a water washing process may be further included before forming the silane layer.

In addition, after step D, (E) a secondary heat treatment step of heat treatment at 60 to 120 ° C. may be further included.

And, step E may be performed at 80 to 100 °C, or 85 to 95 °C.

And, step E may be performed for 1 to 20 minutes, 1 to 10 minutes, or 1 to 5 minutes.

According to the method for forming a copper-tin alloy layer according to the present invention, a copper-tin alloy layer with low roughness and excellent peel strength can be formed. In addition, according to the present invention, only the pure tin layer remaining in addition to the alloy layer created after tin plating can be effectively removed without corrosion of copper, thereby suppressing the formation of Kirkendall voids due to an increase in the IMC layer and improving the adhesion with the resin layer. can be maximized. Additionally, according to the present invention, it is possible to form a uniform IMC layer that is thin and has little thickness variation.

Hereinafter, preferred embodiments of the present invention will be described in detail.

However, the following is only a detailed description of specific embodiments, and since the present invention can be changed in various ways and have various forms, the present invention is not limited to the specific embodiments exemplified. The present invention should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

In addition, in the following description, many specific details, such as specific components, are provided, but this is provided to facilitate a more general understanding of the present invention, and it is known in the art that the present invention can be practiced without these specific details. It will be self-evident to those who have the knowledge. Additionally, in describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

Additionally, the terms used in this application are only used to describe specific embodiments and are not intended to limit the present invention. Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by a person of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and unless explicitly defined in the present application, should not be interpreted in an ideal or excessively formal sense. No.

In this application, singular expressions include plural expressions unless the context clearly dictates otherwise.

In the present application, terms such as 'include', 'contain', or 'have' are intended to refer to the presence of features, components (or components), etc. described in the specification, but are not intended to indicate the presence of one or more other features or This does not mean that components, etc. do not exist or cannot be added.

The method of forming a copper-tin alloy layer of the present invention is a method that can form a copper-tin alloy layer with low surface roughness and excellent peel strength. It can reduce transmission loss in the high frequency range by evening the surface of the alloy layer, thereby reducing high frequency A copper-tin alloy layer that is easy to apply to PCB can be manufactured. Specifically, the method of forming a copper-tin alloy layer of the present invention includes (A) forming a tin plating layer on a copper substrate; (B) heat treating the tin plating layer to form a copper-tin alloy layer; (C) immersing the copper-tin alloy layer in a tin stripping solution containing organosulfonic acid to selectively peel off the pure tin layer; and (D) forming a silane layer on the copper-tin alloy layer. A washing process may be included between each step, and each step will be described in detail below.

First, Step A is a step of forming a tin plating layer on a copper substrate. The tin layer is formed to form an alloy layer to which the coupling agent can be well attached to the copper foil. Step A is a step of immersion tin plating on a copper substrate, and a known method can be used. During tin plating, a copper-tin alloy layer and a tin layer may be formed on the copper substrate.

In addition, a process of pre-treating the copper substrate before forming the tin plating layer may be further included, and the pre-treatment may include an immersion degreasing process, a primary water washing process, an acid washing process, and a secondary water washing process.

The immersion degreasing process may be performed by immersing the acid degreaser at 20 to 40°C, 25 to 35°C, or 28 to 32°C for 0.5 to 10 minutes, 1 to 8 minutes, or 1 to 5 minutes. At this time, the acid degreasing agent may include sulfuric acid.

The pickling process is to remove the copper oxide layer, and is treated in an acidic solution such as sulfuric acid at 20 to 30 ℃, 22 to 28 ℃, or 24 to 26 ℃ for 10 to 120 seconds, 30 to 90 seconds, or 50 to 70 seconds. It may be. In the pickling process, the acidic solution may be a 5 to 20% (w/w), 5 to 15% (w/w), or 8 to 12% (w/w) sulfuric acid solution.

Next, step B is a step of forming a copper-tin alloy layer by heat treating (primary heat treatment) the tin plating layer. After creating the tin layer, the alloy layer is strengthened through a heat process, a predetermined thickness is secured, and roughness is maintained. This is to control it as evenly as possible. The heat treatment may be drying through a natural circulation dry oven.

The heat treatment may be performed at 90 to 130°C, 100 to 120°C, or 105 to 115°C, and may be performed for 30 to 150 seconds, 40 to 120 seconds, or 50 to 100 seconds, especially within the above range. When heat treated, a copper-tin alloy layer with excellent peel strength can be formed. If the heat treatment temperature and time are below the above range, the peeling strength decreases and an alloy layer of an appropriate thickness is not created, so the copper layer can be easily observed when the tin layer is peeled off. On the other hand, even when the heat treatment temperature and time exceed the above range, the peel strength is lowered. Before the heat treatment, the step of washing the tin plating layer with water may be further included.

Next, step C is a step of selectively peeling off the pure tin layer by immersing the copper-tin alloy layer in a tin stripping solution containing organosulfonic acid, in which excess pure tin is removed without peeling off the copper base layer or alloy layer. It is to peel off the bay. According to the present invention, a thin copper-tin alloy layer can be formed by removing the excess tin layer formed.

The present invention relates to an average thickness of the copper-tin alloy layer formed according to the method for forming a copper-tin alloy layer of the present invention is 0.2 ㎛ or less, 0.1 ㎛ or less, or 0.05 ㎛ or less, and 0.001 ㎛ or more, 0.01 ㎛ or more, or 0.02 ㎛ or more, and the thickness deviation may be within ±0.009 ㎛, ±0.006 ㎛, or ±0.005 ㎛. In this respect, step C may be immersing the copper-tin alloy layer in a tin stripper for 10 to 120 seconds, 20 to 105 seconds, or 30 to 90 seconds, at 20 to 40 ° C., 25 to 35 ° C., or 28 ° C. It can be carried out at 32°C. If the stripper treatment time is less than the above range, peeling is not sufficiently performed, resulting in thicker thickness and greater thickness variation. On the other hand, even if the processing time exceeds the above range, the target thickness and thickness deviation are not satisfied.

In step C, the tin stripper contains an organosulfonic acid, which is represented by RSO ₃ H, and R may be a saturated hydrocarbon having 1 to 6 carbon atoms, 1 to 3, or 1 to 2 carbon atoms, for example The organosulfonic acid may be methanesulfonic acid or propanesulfonic acid.

The tin stripping liquid may be characterized in that it does not contain an inorganic acid. The inorganic acid may refer to sulfuric acid, nitric acid, etc. In the case of conventional stripping solutions made of sulfuric acid or nitric acid, the peeling speed was too fast or slow, making it difficult to control the thickness and forming a uniform surface. The present invention can solve the above problems and replace the stripping solution made of inorganic acid.

Additionally, the tin stripper may contain 10 to 50 g/L, 15 to 40 g/L, or 20 to 30 g/L of the organosulfonic acid. If the concentration of organosulfonic acid exceeds the above range, the peeling speed is too fast and surface oxidation may easily occur. On the other hand, if the concentration of organosulfonic acid is less than the above range, the peeling speed may be too slow, making thickness control ineffective. Additionally, if the peeling speed is slow, the concentration of the oxidizer may increase, in which case surface oxidation may occur frequently and control of the peeling speed may be difficult.

The tin stripping solution may further include an oxidizing agent, through which the peeling speed can be improved, the occurrence of stains can be suppressed, and a uniform thickness can be formed. The oxidizing agent may be an aromatic compound having a nitro group, or a nitrobenzene compound having a SO ₃ H, SO ₃ M, or SO ₃ X functional group. Here, M may be an alkali metal such as Na or K, and X may be a halogen such as Cl, Br, or I.

If the oxidizing agent has a sulfonic acid (SO ₃ H) functional group, it may be aminonitrobenzenesulfonic acid, for example, 2-Amino-5-nitrobenzenesulfonic acid.

When the oxidizing agent has a sulfonate (SO ₃ M) functional group, it may be o-nitrobenzenesulfonate, m-nitrobenzenesulfonate, p-nitrobenzenesulfonate, or an alkali metal salt such as sodium salt or potassium salt, and is preferred. It may be sodium salt of m-nitrobenzenesulfonate.

If the oxidizing agent has a sulfonyl halide (SO ₃

Additionally, the oxidizing agent may include 0.5 to 10 parts by weight, 2 to 8 parts by weight, or 4 to 6 parts by weight based on 100 parts by weight of organosulfonic acid. If the oxidizing agent content is less than the above range, the tin layer may not be peeled off smoothly and the thickness deviation may increase. On the other hand, if the oxidizing agent content exceeds the above range, it is difficult to control the peeling speed and oxidation may occur frequently.

Next, Step D is a step of forming a silane layer on the copper-tin alloy layer, and is a step of forming a silane coupling layer for bonding the copper substrate and the resin layer. There may be a water washing process before forming the silane layer. Additionally, in Step D, a silane layer may be formed by applying an amine-based silane coupling agent, and the amine-based silane coupling agent may be a silane compound having one or two or more amine groups. For example, the amine-based silane coupling agent is N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and 3-aminopropyltrime. Toxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)-propylamine, N-phenyl-3-aminopropyltrimethoxysilane, or It may be N-(3-trimethoxysilyl)propyl-1,2-ethanediamine or may include one or more of these.

And, step D may be performed at 15 to 50 °C, 20 to 40 °C, or 25 to 35 °C for 20 to 60 seconds, 25 to 50 seconds, or 25 to 40 seconds. If the temperature or time when forming the silane layer is below the above range, the silane compound may be unevenly distributed on the surface, which may reduce adhesion. On the other hand, if the temperature or time exceeds the above range, the silane compound in the solution may clump together as the temperature rises. This phenomenon may occur.

In addition, the method of forming a copper-tin alloy layer of the present invention may further include (E) a secondary heat treatment step after step D. Step E is a secondary heat treatment step after the primary heat treatment in Step B. The present invention can form a tin alloy layer with excellent peel strength and low roughness through a two-step heat treatment process. Additionally, the moisture contained in the alloy layer can be minimized through the secondary heat treatment. The secondary heat treatment is a baking step and may be performed through a natural circulation dry oven.

The secondary heat treatment step may be performed at 60 to 120°C, 80 to 100°C, or 85 to 95°C for 1 to 20 minutes, 1 to 10 minutes, or 1 to 5 minutes. If the secondary heat treatment temperature and time are less than the above range, the peel strength may decrease, and conversely, if it exceeds the above range, productivity may decrease.

The copper-tin alloy layer of the present invention may be a copper-tin alloy layer for stacking a resin layer on top of the silane layer, and as a result, the copper substrate, copper-tin alloy layer, silane coupling layer, and resin layer are sequentially laminated. Laminates can be manufactured.

The surface layer of the copper-tin alloy layer formed according to the copper-tin alloy layer forming method of the present invention has a copper:tin ratio (element ratio) of 93:7 to 98:2, 93.7:6.3 to 97:3, or 94:6. It may be from 95:5.

Hereinafter, embodiments of the present invention will be described.

[Example]

Examples 1-1 to 1-9: Preparation of copper-tin alloy layer

A 20 x 20 cm ² HVLP copper foil was treated with an acid degreaser containing sulfuric acid at 30°C for 3 minutes, washed with water, then treated with a 10% sulfuric acid solution for 1 minute and washed with water. Afterwards, tin was subjected to substitution plating (HoplaStan ET-40 at 30°C, 50 seconds) and then subjected to primary heat treatment at 90°C, 100°C, or 110°C for 1 minute, 1 minute and 30 seconds, or 2 minutes as shown in Table 1 below. (Examples 1-1 to 1-9). These were each immersed in a stripping solution containing methanesulfonic acid and peeled for 1 minute and 15 seconds, then an amine silane coupling agent was applied and treated at 30°C for 30 seconds, followed by secondary heat treatment at 90°C for 2 minutes to remove the copper. -A tin alloy layer was formed.

Comparative Example 1-1: Preparation of copper-tin alloy layer

A copper-tin alloy layer was formed in the same manner as in Example 1-1, but without primary heat treatment as shown in Table 1 below.

Comparative Example 1-2: Preparation of copper-tin alloy layer

A copper-tin alloy layer was formed in the same manner as in Example 1-1, but after primary heat treatment was performed at 60° C. for 1 minute, as shown in Table 1 below, the copper-tin alloy layer was formed.

Test Example 1: Peel strength measurement

The results of measuring the peeling strength of the copper-tin alloy layers prepared according to Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-2 were as shown in Table 1 below, and the results were as follows. It was confirmed that the peel strength was significantly improved in Examples 1-1 to 1-9 compared to Comparative Example 1-1 and Comparative Example 1-2 treated at 60°C.

First heat treatment temperature 1st heat treatment time Peel Strength
(Unit: N, Avg.) Comparative Example 1-1 - 0.283 Comparative Example 1-2 60℃ 1 min 0.317 Example 1-1 90℃ 1 min 0.333 Example 1-2 1 minute 30 seconds 0.350 Example 1-3 2 minutes 0.353 Example 1-4 100℃ 1 min 0.450 Examples 1-5 1 minute 30 seconds 0.500 Example 1-6 2 minutes 0.400 Example 1-7 110℃ 1 min 0.517 Examples 1-8 1 minute 30 seconds 0.533 Example 1-9 2 minutes 0.433

Examples 2-1 to 2-5: Preparation of copper-tin alloy layer

A copper-tin alloy layer was formed in the same manner as in Example 1-1, but after secondary heat treatment was performed at 60°C, 80°C, or 90°C for 1 or 2 minutes as shown in Table 3 below, the copper-tin alloy layer was formed. was formed.

Comparative Example 2-1: Preparation of copper-tin alloy layer

A copper-tin alloy layer was formed in the same manner as in Example 1-1, but without secondary heat treatment.

Test Example 2: Peel strength measurement

The peel strength of the copper-tin alloy layer prepared according to Examples 2-1 to 2-5 and Comparative Example 2-1 was measured under the conditions shown in Table 2 below.

test name item condition Tensile Test Test type tensile strength test Test Speed 5.08cm/min tensile length Test until damaged testing equipment Universal complex tester (LLOYD/LS5)

The results were as shown in Table 3 below, and it was confirmed that the peel strength was significantly improved in Examples 2-1 to 2-5 in which secondary heat treatment was performed compared to Comparative Example 2-1 in which secondary heat treatment was not performed.

Secondary heat treatment temperature Secondary heat treatment time Peel Strength
(Unit: N, Avg.) Comparative Example 2-1 - Less than 0.1 (not measurable) Example 2-1 60℃ 1 min 0.140 Example 2-2 80℃ 1 min 0.180 Example 2-3 2 minutes 0.225 Example 2-4 90℃ 1 min 0.233 Example 2-5 2 minutes 0.283

Test Example 3: Illuminance measurement

The results of measuring the roughness before and after peeling after the first heat treatment for Example 1-8 and the roughness before and after peeling for Comparative Example 1-1 were as shown in Table 4 below. When the first heat treatment was performed, the roughness was higher than when the first heat treatment was not performed. It can be seen that was reduced and an even surface was formed.

Ra(㎛) copper foil 0.46 Comparative Example 1-1 Before peeling 0.44 After peeling 0.46 Examples 1-8 Before peeling 0.43 After peeling 0.44

In the above, preferred embodiments of the present invention have been described, but the present invention is not limited to the specific embodiments described above, and various modifications can be made by those skilled in the art without departing from the gist of the present invention. Of course it is possible. Accordingly, the scope of the present invention should not be construed as limited to the above embodiments, but should be determined by the claims described below as well as equivalents to these claims.

Claims (7)

(A) forming a tin plating layer on a copper substrate;
(B) performing a primary heat treatment on the tin plating layer to form a copper-tin alloy layer;
(C) immersing the copper-tin alloy layer in a tin stripping solution containing organosulfonic acid to selectively peel off the pure tin layer;
(D) forming a silane layer on the copper-tin alloy layer; and
(E) a secondary heat treatment step of heat treatment after step D; Including,
In step (B), heat treatment is performed at 90°C to 130°C for 30 seconds to 150 seconds,
In step (E), heat treatment is performed at 60°C to 120°C for 2 to 20 minutes,
The copper-tin alloy layer formed by performing the first heat treatment in step (B) has reduced roughness compared to the tin plating layer formed by step (A). In claim 1,
Further comprising a process of pre-treating the copper substrate before forming the tin plating layer, wherein the pre-treatment includes an immersion degreasing process, a first water washing process, an pickling process, and a second water washing process. Tin alloy layer formation method. delete In claim 1,
Step C is a method of forming a copper-tin alloy layer, characterized in that immersing the copper-tin alloy layer in a tin stripper for 10 to 120 seconds. In claim 1,
A method of forming a copper-tin alloy layer, wherein the tin stripping liquid contains an oxidizing agent. In claim 1,
Step D is a method of forming a copper-tin alloy layer, characterized in that a silane layer is formed by applying an amine-based silane coupling agent. delete