JP2002134858A - Copper foil for printed boards - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper foil for printed boards which maintains a stable adequate electrodeposition grain shape even on a rolled copper foil having a nonuniform surface condition, and forms a desired uniform roughened plating of electrodeposition grains on the nonuniformly conditioned surface of the rolled copper foil, thereby improving the adhesion of the roughened electrodeposition plating copper foil to a resin board. SOLUTION: The copper foil for printed boards has a roughened plating surface. Prior to the roughening plating, the foil surface is pre-roughened into a pre-roughened surface having a roughness Ra of 200 nm or more but less than 500 nm in measurement using an interatomic force microscope. The copper foil is dipped in a specified treating solution and set to a negative electrode to apply electrodeposition metal grains preferably such as copper grains of 1-3 μm onto the pre-roughened surface, thereby forming a roughened plating surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper foil for a printed circuit board, and more particularly to a copper foil for a printed circuit board which is used by roughening the surface of a rolled copper foil.

[0002]

2. Description of the Related Art Copper foils used for printed circuit boards are:
In order to improve the adhesiveness of the copper foil to be laminated with the resin substrate,
The surface to be bonded of the copper foil is subjected to a roughening plating process. Conventionally, a method of electrodepositing metallic copper by electroplating has been used for roughening plating of copper foil. That is, the electrodeposition is performed using an aqueous solution of copper sulfate obtained by adding an appropriate amount of sulfuric acid to the electrolytic solution at a liquid temperature of 40%.
Electrolysis is carried out at about ° C. using a copper foil as a negative electrode to cause coarse metal particles to be electrodeposited on the surface of the copper foil.

[0003] In the electrodeposition of metal particles on the copper foil surface, in order to improve the adhesion between the roughened copper foil and the resin substrate, the shape of the electrodeposited particles of the coarse metal particles to be electrodeposited on the copper foil surface is improved. Tight control is very important. In this context, first,
If the electrodeposited copper particles are too fine, the roughened surface is finished in a smooth copper plating state, and there is a situation that an anchor effect for improving the adhesiveness cannot be expected. Second, the shape of the electrodeposited copper particles is as follows. It is closely related to the current density of roughening plating.If the current density is low, fine particles are electrodeposited and a smooth plating surface is formed. Conversely, if the current density is too high, so-called roughening plating occurs, and the electrodeposited particles themselves are formed. There is a situation that it is easy to peel off. On the other hand, a polishing method of mechanically roughening using a brush or a buff has also been proposed, but it is difficult to apply the method to a copper foil having low strength, and a uniform finish is not always obtained. Further, the polishing powder is not an appropriate roughening method because there is a possibility that the polishing powder is mixed into the roughening plating solution and causes a rough plating failure.

[0004]

However, according to the rough plating on the surface of the copper foil by the conventional electrodeposition method, even if the shape of the electrodeposited particles is controlled, the rolling roll and the copper foil can be used during the rolling of the copper foil. Because the contact state of the copper foil is not necessarily uniform, the effect also appears on the surface state of the copper foil, and when the surface of the rolled copper foil is viewed finely, the surface roughness of the copper foil is said to be unevenly finished. There was a problem. Therefore, even if the surface of the rolled copper foil is subjected to roughening plating by electrodeposition under certain conditions, the state of the electrodeposited particles becomes uneven depending on the surface position of the copper foil, and the uneven electrodeposited particles are There is a problem of causing a cause of poor adhesion between the copper foil of the electrodeposition-roughening plating and the resin substrate, and a solution has been demanded.

Therefore, an object of the present invention is to provide a copper foil for a printed circuit board that can maintain a stable and appropriate electrodeposited particle shape even in a copper foil for a board in which the surface morphology of the rolled copper foil is uneven. To provide.

Another object of the present invention is to provide a method of forming a roughened plating of desired uniform electrodeposited particles on the surface of a rolled copper foil in an uneven state, and to provide a copper foil of electrodeposited roughened plating. To provide a printed circuit board copper foil having improved adhesiveness between the resin and a resin substrate.

[0007]

In order to achieve the above object, the present invention provides a copper foil for a printed circuit board whose surface is subjected to roughening plating, wherein the copper foil is formed before the roughening plating is performed. A copper foil for a printed circuit board, comprising a pre-roughened surface formed by a pre-roughening treatment applied to a surface of a foil.

According to the present invention, in order to achieve the above object, the pre-roughened surface has a roughened surface roughness Ra measured by an atomic force microscope on the surface of the copper foil. 20
It is characterized by being formed by a preliminary roughening treatment of not less than 0 nm and less than 500 nm, wherein the preliminary roughened surface has a predetermined roughness Ra used in the final rolling step of the copper foil. Provided by a preliminary roughening treatment at the time of rolling the copper foil by a rolling roll provided on the surface thereof.

Further, in order to achieve the above object, the present invention is characterized in that the preliminary roughening surface is subjected to a preliminary roughening treatment by electrolytic degreasing of the copper foil surface using the copper foil as an anode. Characterized in that the preliminary roughened surface,
The copper foil as an anode is characterized by being subjected to a preliminary roughening treatment by fine electrolytic polishing of the copper foil surface, and the preliminary roughened surface is immersed and pickled in the copper foil. It is characterized by being subjected to a preliminary roughening treatment by degreasing the surface of the copper foil, wherein the preliminary roughened surface is immersed in the copper foil and pickled, and the surface of the copper foil is dissolved using the copper foil as an anode. Provided is a copper foil for a printed circuit board, which has been subjected to preliminary roughening treatment by removal.

Further, in order to achieve the above object, the present invention has a roughened plating surface formed by electrodeposition of metal particles using the copper foil as a negative electrode on the preliminary roughened surface. Characterized in that the copper foil is used as a negative electrode and has a particle size of 1 μm.
A copper foil for a printed circuit board, characterized by having a roughened plating surface formed by electrodeposition of copper particles of m to 3 μm on the preliminary roughened surface.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As an embodiment of the present invention, a copper foil for a printed circuit board finished by a rolling roll or a copper foil for an oxygen-free copper printed circuit board which is most frequently used for a printed circuit board will be described. I do. These copper foils are usually subjected to final rolling using a roll having a normal surface roughness, and a roll having a smooth finish, and the surface roughness of the copper foil measured by an atomic force microscope. (Ra) is also generally about Ra = 100, and is generally a copper foil with an insufficient surface having uneven portions. In the embodiment of the present invention, in the copper foil for a printed circuit board subjected to roughening plating on the surface of the rolled copper foil having non-uniform irregularities, before roughening plating, on the surface of the copper foil It has a pre-roughened surface formed by the applied pre-roughening process, and then roughening plating necessary for the configuration of a printed circuit is applied on the pre-roughened surface.
According to the embodiment of the present invention, on the surface of the rolled copper foil having non-uniform irregularities, first subjected to the pre-roughened surface formed by the pre-roughening treatment, The roughening plating is performed on the pre-roughened surface by electrodeposition of metal particles with the copper foil as the negative electrode. The copper foil surface has a uniform predetermined surface roughness Ra by the preliminary roughening surface formed by the above, and the roughening performed on the preliminary roughening surface having the uniform surface roughness Ra It is realized that the plated surface is also finished to a roughened plating having a desired surface roughness Ra.

In particular, according to the present invention, in the conventional copper foil for printed circuit boards, the relationship between the surface roughness of the copper foil and the form of the electrodeposited material of the roughening plating has not been sufficiently grasped, so that Although elucidation of the cause of the poor adhesion to the resin substrate was delayed, the present inventors found that the size of the electrodeposited particles of the rough plating applied to the rolled copper foil having an uneven surface roughness was roughened. The size of the metal particles electrodeposited on the copper foil,
Desirably, it has been found that it is optimal to finish the particle size in the range of 1 μm to 3 μm.

In the present invention, the roughening plating applied on the pre-roughened surface is formed by electrodeposition of metal particles having a copper foil as a negative electrode. The roughening plating applied thereon is characterized by being formed of electrodeposited metal particles such as copper particles having a particle diameter of preferably 1 μm to 3 μm using a copper foil as a negative electrode. According to the embodiment of the present invention, by applying an appropriate amount of preliminary roughening treatment in advance to the surface of the rolled copper foil to form a pre-roughened surface, the unevenness of the surface of the rolled copper foil is uniformly and finely distributed. The fine and uniform irregularities can be directly reflected in the distribution of the high and low current density portions during the roughening plating performed on the copper foil. The particles are electrodeposited on the high current density portions uniformly distributed on the entire surface of the copper foil, and as a result, a uniform roughened plating surface can be obtained.

In an embodiment of the present invention, a pre-roughening method for forming a pre-roughened surface to be preliminarily applied before roughening plating on the surface of a rolled copper foil in an uneven surface state includes: , Predetermined surface roughness (atomic force microscope measured value Ra)
Moderate preliminary roughening treatment with copper foil, moderate preliminary roughening treatment by degreasing or pickling using copper foil as anode, moderate preliminary roughening treatment by dissolving removal using copper foil as anode, or moderate surface roughening There are pre-roughening treatments using rolling rolls and the like, and these can be appropriately used depending on the type and use of the copper foil for printed circuit boards.

In the present invention, the pre-roughened surface formed by performing the pre-roughening treatment on the surface of the copper foil is determined by measuring the roughness of the surface of the copper foil by an atomic force microscope. Ra
Is desirably formed so as to be quantitatively at least 200 nm and less than 500 nm. This is because when the preliminary roughening treatment amount of the preliminary roughening treatment surface is less than 200 nm, the effect of roughening plating uniformity is small, and when it is 500 nm or more, the effect of roughening plating uniformity is saturated. Not economic. As one of the pre-roughening treatment methods of the pre-roughened surface in the present invention, at least the surface of a rolling roll used in the final rolling step of a copper foil has a predetermined roughness Ra (for example, 200 nm or more). , Less than 500 nm) by rolling the copper foil with a rolling roll provided with
A desired preliminary roughening process can be performed, and a predetermined preliminary roughening surface is formed.

In the present invention, a specific method other than the rolling roll method for roughening treatment for forming a preliminary roughened surface by performing a preliminary roughening treatment on the surface of a copper foil is as follows. Method. These can be applied alone or in an appropriate combination. (1) The copper foil surface is formed by electrolytic degreasing using the copper foil as an anode. (2) The copper foil surface is formed by fine electrolytic polishing using the copper foil as an anode. (3) The copper foil is formed by immersing and pickling and then degreasing the surface of the copper foil. (4) The surface of the copper foil is formed by dissolving and removing the copper foil as an anode during immersion and pickling.

Further, in the present invention, as a method of forming a roughened plating formed on a pre-roughened surface applied to a copper foil surface, the copper foil is immersed in a predetermined processing solution to convert the copper foil into a negative electrode. It is preferably formed by applying electrodeposited metal particles of copper particles having a particle size of 1 μm to 3 μm, but also by applying electrodeposited metal particles such as silver particles other than copper particles. A roughened plating surface can be formed on the substrate.

[0018]

(Embodiment 1) The column of Embodiment 1 in Table 1 shows a copper foil for a printed circuit board according to an embodiment of the present invention. The preparation of the sample of Example 1 was performed using a pre-roughening surface formed by a pre-roughening treatment applied to the surface of the copper foil by rolling using a final rolling roll finished with a changed surface roughness. After using the provided copper foil as a test material and removing the rolling oil by electrolytic degreasing using the copper foil as an anode, Table 1
Predetermined roughening plating was performed under the described conditions to obtain a copper foil for a printed circuit board having a pre-roughened surface and a roughened plated surface on the surface of the copper foil. Table 1 shows the surface roughness Ra (nm) measured by an atomic force microscope, the conditions for roughening, and the results of evaluation of the roughness uniformity by visual observation.

[0019]

[Table 1]

(Comparative Example 1, Comparative Example 2)
The column of Comparative Example 2 shows a copper foil for a substrate prepared for comparison. For the preparation of the sample of the comparative example, using a roll having a smooth surface roughness and a normal roll, a finally rolled copper foil was used as a test material. The surface roughness Ra of the copper foil is around Ra = 100 nm. Rough plating is
This was performed by a predetermined method conventionally performed.

According to Table 1, the surface of the copper foil of Example 1 of the present invention was given a predetermined surface roughness by a finishing roll provided on a roll in advance, and the copper foil was measured by an atomic force microscope. A preliminary roughened surface (Ra = 221 nm) having a surface roughness Ra of more than 200 nm is formed, and a predetermined roughening plating is applied thereon, so that the copper foil surface has a uniform roughened plating. It can be seen that the treatment has been formed and is in a good roughened state. In particular, the surface of the copper foil of Example 1 using a roll more finished than usual had a surface roughness of the copper foil exceeding 200 nm (Ra value measured by an atomic force microscope), and a uniform roughening treatment was possible. It has become.

On the other hand, when a smooth rolled roll is used (Comparative Example 1 in Table 1), the copper foil surface roughness Ra
In the case of using a normal rolling roll having a small surface roughness of 76 nm (Comparative Example 2 in Table 1), the copper foil surface roughness Ra was 120 nm, and the uniformity of rough plating was insufficient. It turns out to be something.

[0023]

(Embodiments 2 to 5 of the Present Invention) The columns of Embodiments 2 to 5 in Table 2 show copper foils for printed circuit boards according to embodiments of the present invention. Examples of the sample include:
Copper foil (oxygen-free copper, thickness 25 μm, pure material) was used. First, the preliminary roughening treatment is performed by degreasing the surface by electrolytic degreasing, and then immersing it in a 1% aqueous sulfuric acid solution (described in Table 2) to which 3% of a hydrogen peroxide aqueous solution (35%) has been added (described in Table 2) for a predetermined time. A copper foil provided with a pre-roughened surface was obtained. The copper foil which has been subjected to the preliminary roughening treatment is subjected to predetermined roughening plating under the conditions shown in Table 2, and a print having a preliminary roughening treated surface and a roughened plating surface on the surface of the copper foil. A copper foil for a substrate was prepared. Table 2 shows the relationship between the conditions for the preliminary roughening treatment, the surface roughness Ra (nm) measured by an atomic force microscope (AFM), the conditions for roughening, and the results of evaluation of the roughness uniformity by visual observation. Was.

[0024]

[Table 2]

(Comparative Examples 3 to 5) The columns of Comparative Examples 3 to 5 in Table 2 show copper foils for substrates prepared for comparison. For the preparation of the sample of the comparative example, using a roll having a smooth surface roughness and a normal roll, a finally rolled copper foil was used as a test material. The surface roughness Ra of the copper foil is around Ra = 100 nm. The roughening plating was performed by a conventional method. The sample of the comparative example includes copper foil (oxygen-free copper, thickness 25 μm).
m, pure material), copper foil without pre-roughening treatment (Comparative Example 3), after degreasing the surface by electrolytic degreasing, in 1% sulfuric acid aqueous solution to which 3% of hydrogen peroxide aqueous solution (35%) was added A copper foil (Comparative Example 4, Comparative Example 5) immersed in a predetermined time was prepared. Next, roughening plating was performed under the roughening plating conditions shown in Table 2, and the uniformity of the roughening was visually evaluated. Table 2 also shows the surface roughness Ra (nm) measured by an atomic force microscope, the conditions for roughening, and the evaluation results of the roughness uniformity by visual observation.

According to Table 2, the copper foil surfaces of Examples 2 to 5 of the present invention were previously subjected to a predetermined preliminary roughening treatment in which the copper foil surface roughness Ra measured by an atomic force microscope exceeded 200 nm. Since it has a preliminary roughened surface formed by the above, and given a roughening plating on it,
It can be seen that the surface of the copper foil can be subjected to a roughening plating process in which copper particles are uniformly electrodeposited, and that the roughening is uniformly formed and is in a good condition. Note that if the preliminary roughening process is performed for 60 minutes or more (Examples 4 and 5), the effect is saturated and only the processing time is extended, so that it is understood that no further processing is required.

On the other hand, in Comparative Examples 3 to 5 in Table 2, the measured surface roughness Ra by the atomic force microscope was 2%.
The thickness was less than 00 nm, and depending on the position of the copper foil, there were places where copper particles were densely and partly sparse, and the uniformity of roughening plating was insufficient.

[0028]

According to the copper foil for printed circuit boards of the present invention,
Before roughening plating, the surface of the rolled copper foil having an uneven surface is subjected to a preliminary roughening surface having a predetermined roughness (Ra) formed by an appropriate preliminary roughening process. ,
Since the surface of the copper foil has been appropriately roughened in advance and subjected to a predetermined roughening plating, the copper foil surface having a pre-roughened surface formed by an appropriate preliminary roughening process The rough plating has an effect that the electrodeposition of copper particles in the rough plating is stabilized, and good rough plating can be formed.
In particular, the surface of the rolled copper foil having an uneven surface is preliminarily roughened by an appropriate preliminary roughening treatment, so that the unevenness of the copper foil surface is uniformly and finely distributed. This is directly reflected in the distribution of the high and low current densities during rough plating. Therefore, the copper particles of the rough plating are electrodeposited on the high current density portion uniformly distributed over the entire surface of the copper foil, and as a result, a uniform rough plating surface can be obtained.

Further, according to the copper foil for a printed board of the present invention, the surface irregularities of the copper foil caused by the rolling are appropriately roughened in advance by forming the preliminary roughened surface. The current density distribution when roughening plating electrodeposition is applied, the phenomenon that current concentrates on the convex part of the copper foil surface generated during rolling and large copper particles precipitate, and the copper foil surface generated during rolling The phenomenon that the current density of the concave portion becomes low and the concave portion becomes fine copper particles can be eliminated. As a result, roughening plating by electrodeposition applied on an appropriate preliminary roughening treatment surface is effective for stable and uniform roughening of electrodeposited particles even in a rolled copper foil having an uneven surface state. Plating can be formed, and a copper foil for printed circuit boards having improved adhesion between the copper foil on the electrodeposited roughened plating surface and the resin substrate can be provided.

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Claims (9)

[Claims] 1. A copper foil for a printed circuit board having a surface subjected to roughening plating, wherein the copper foil is formed by a preliminary roughening treatment applied to the surface of the copper foil before the roughening plating is applied. A copper foil for a printed circuit board, comprising a pre-roughened surface. 2. The pre-roughened surface is measured by an atomic force microscope on the surface of the copper foil, and the roughened surface
2. The copper foil for a printed circuit board according to claim 1, wherein the copper foil is formed by a preliminary roughening treatment of not less than 200 nm and less than 500 nm. 3. The pre-roughened surface is a pre-roughened surface when a predetermined roughening surface roughness Ra used in the final rolling step of the copper foil is rolled by a rolling roll provided on the surface. The copper foil for printed circuit boards according to claim 1 or 2, wherein the copper foil is applied by a roughening treatment. 4. The pre-roughening surface is subjected to a pre-roughening treatment by electrolytic degreasing of the surface of the copper foil using the copper foil as an anode. The printed circuit board copper foil described in the above. 5. The pre-roughening surface is subjected to a pre-roughening treatment by fine electrolytic polishing of the surface of the copper foil using the copper foil as an anode. Item 3. A copper foil for a printed circuit board according to item 2. 6. The pre-roughened surface is preliminarily roughened by immersing and pickling the copper foil and degreasing the surface of the copper foil. 2. The copper foil for printed circuit boards according to 2. 7. The pre-roughening surface is subjected to a pre-roughening treatment by immersing and pickling the copper foil and dissolving and removing the surface of the copper foil using the copper foil as an anode. 3. The copper foil for a printed circuit board according to claim 1 or claim 2. 8. The pre-roughened surface has a roughened plating surface formed by electrodeposition of metal particles using the copper foil as a negative electrode. The copper foil for a printed board according to any one of the above. 9. The method according to claim 1, wherein said copper foil is used as a negative electrode and has a particle size of 1 μm to 3 μm.
9. The printed circuit board according to claim 1, further comprising a roughened plating surface formed by electrodeposition of copper particles having a thickness of μm on the preliminary roughened surface. 10. Copper foil.