JP2002019017A - Copper foil with resin for laser beam boring and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide copper foil with a resin capable of laser beam boring in order to enable the adoption of a copper direct method which can use a conventional infrastructure directly and reduce costs by cutting a process and a method for producing the copper foil. SOLUTION: In the copper foil with the resin for laser beam boring, a surface layer of manganese and/or a manganese alloy is formed on the surface on the laser beam irradiation side of the copper foil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a resin-coated copper foil for laser drilling and a method for producing the same.

[0002]

2. Description of the Related Art Information-related electronic devices such as mobile phones are rapidly spreading. In particular, as mobile phones have become smaller, lighter, and more multifunctional, printed wiring boards used therein have been required to have higher densities. In addition, a build-up substrate is indispensable for efficiently increasing the wiring density.

As one method of manufacturing a build-up substrate, there is a resin-attached copper foil method which can be manufactured by using a conventional laminated press type subtractive method. As a method of manufacturing this build-up substrate, a wiring pattern is formed on a conductor layer using a double-sided copper-clad laminate or the like, and the inner layer is formed, or a plurality of sheets are stacked with an insulating layer interposed therebetween, and the inner layer is formed. The foil is sandwiched so that the copper foil side is the outermost surface, and a laminating press is performed.
Alternatively, the inner layer is subjected to laminating press in advance, and the one provided with through-hole plating is sandwiched between resin-coated copper foils and subjected to laminating press. The laminated substrate forms a through hole and a via hole for taking in a signal to an inner layer, and is electrically connected. Laser processing of the copper foil with resin is applied to the via hole formation at this time, the equipment price is low,
A carbon dioxide laser having a high processing speed is mainly used.

The above-mentioned methods using a carbon dioxide laser can be roughly classified into a conformal mask method and a copper direct method. In the conformal mask method, the copper foil in the via forming portion is removed in advance by etching, and the remaining copper foil portion is used as a mask and laser processing is performed. By increasing the laser diameter, it can be used in a place where the energy is strong. Therefore, it is generally adopted. However, heat is applied to the resin portion around the copper foil opening, and the copper foil portion tends to overhang and the hole cross section tends to be barrel-shaped. However, there is a problem that a conduction failure occurs and a position shift occurs. In addition, it is difficult to inspect the opening by etching and the like, and the copper foil opening step by etching is one of the factors for increasing the cost.

On the other hand, in the copper direct method, a copper foil and a resin are collectively laser-drilled, so that the copper foil opening process can be reduced and the process can be simplified. In this method, copper must be directly irradiated with a carbon dioxide gas laser to perform drilling. However, the absorption rate of copper in the carbon dioxide laser wavelength region (10.6 μm) is extremely low, and drilling is difficult. Therefore, for example, Japanese Patent Application Laid-Open No. 10-190236 discloses that as a process for increasing the laser absorptivity, as a result of considering the formation and coloring of a material layer having high laser sensitivity, metal oxides are preferred, and CuO _X is particularly preferred. It has been disclosed. However, if the oxide layer is on the surface, the plating will be poor and the insulating layer will be formed, which is not practical.

[0006] In addition, a measure is taken to increase the absorptivity by subjecting the copper foil surface to a treatment for imparting an appropriate surface roughness such as a blackening treatment to cause multiple reflection on the copper foil surface. Before absorbing the heat until the foil penetrates, the uneven layer on the surface melts and disappears, and the effect of improving the absorption rate cannot be expected. According to the study of the present inventors, in the method such as the blackening treatment for imparting the surface roughness described above, the laser is absorbed on the surface of the copper foil, and at the stage where the uneven layer on the surface is melted, the effect is lost. It was confirmed that the thickness of the copper foil that could be penetrated was limited.

[0007]

Therefore, the present inventors can use the conventional infrastructure as it is,
In addition, as a result of intensive studies on the processing that allows direct drilling of copper foil with resin using a carbon dioxide laser, metals and alloys that have a higher laser absorption rate than copper on the laser irradiation side surface of the copper foil It has been found that the thickness of the copper foil that can be penetrated can be reduced to a practical level by forming a special layer consisting of An object of the present invention is to provide a resin-coated copper foil capable of laser drilling and a method of manufacturing the same in order to enable the adoption of a copper direct method that can use the existing infrastructure as it is and reduce costs by reducing the number of processes. Is to do.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an important feature of the present invention is that a surface layer made of one or both of manganese and a manganese alloy is provided on a copper foil surface. To be formed. That is, the present invention is a resin-coated copper foil for laser drilling in which a surface layer made of one or both of manganese and a manganese alloy is formed on the surface of the copper foil on the laser irradiation side.

Preferably, the thickness of the surface layer is 0.05 μm to 3.
This is a resin-coated copper foil having a diameter of 0 μm for laser drilling.
Further, the present invention is a method for producing a resin-coated copper foil for laser drilling, which comprises a step of forming a manganese layer or a manganese alloy layer on the surface of the copper foil by a vapor deposition method.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below.
As described above, an important feature of the present invention is to form a surface layer made of one or both of manganese and a manganese alloy on a copper foil surface. Manganese has the highest electrical resistivity among metals, and the surface layer made of manganese or manganese alloy or both has a laser absorptivity that is about the same as copper.
10 times higher. By forming a surface layer made of one or both of manganese and a manganese alloy, laser can be absorbed by the surface layer, and copper beneath can be melted and evaporated by heat conduction.

The melting point of the surface layer is the boiling point of copper.
When the temperature is higher than 55K, even when the boiling point of copper is reached, the surface layer remains in a solid phase, the evaporation does not work well, the copper foil cannot be penetrated, or the hole shape becomes distorted. Therefore, it is necessary to select a surface layer made of one or both of a metal and an alloy having a melting point of 2855 K or less, which is the boiling point of copper. Further, considering the suppression of splash during laser drilling, it is desirable that the melting point of the surface layer be higher than the melting point of copper. That is, the melting point of manganese is 1356K or more and the melting point of manganese is 1517K, which is suitable as a surface layer.

For the above reasons, by forming a surface layer made of one or both of manganese and a manganese alloy on the surface of the copper foil, the laser absorptance in the surface layer is improved, and the heat conduction causes the laser layer to be directly underneath. Copper can be melted and evaporated to penetrate the copper foil. For this reason, it is possible to suppress the hole cross section due to the overhang from becoming barrel-shaped, and to suppress the problem that the plating does not turn uniformly in the subsequent copper plating process, causing a conduction failure or a displacement. Note that the manganese alloy may be an alloy of manganese and copper (solid solution), or may be an alloy mainly containing manganese (50% or more) in atomic% and containing another element.

In the present invention, if the thickness of the above-mentioned surface layer is too small, the surface layer absorbs laser light and melts and evaporates before being thermally diffused into the copper foil. Without a sufficient temperature rise, the surface layer may disappear and the effect of the present invention may be lost. Therefore, the thickness of the surface layer is desirably 0.05 μm or more. On the other hand, if the thickness of the surface layer is too large, it adversely affects the treatment in the subsequent step and the electric conductivity. The copper foil is made by drilling and forming vias, and then the wiring pattern is formed by etching.In this case, if the surface layer is thick, precise patterning can be performed due to the difference in etching rate between the surface layer and copper. hard. Specifically, when the thickness of the surface layer is larger than 3.0 μm, the etching accuracy may be significantly deteriorated. Further, after drilling, the surface layer may be removed by selective etching in advance to form a wiring pattern. However, even if selective etching is performed, the thickness of the removed surface layer is preferably smaller. Therefore, the thickness of the surface layer is preferably 0.05 μm to 3.0 μm, and more preferably 0.1 μm to 1.5 μm.

In consideration of laser drilling and the above-described wiring pattern etching, the copper foil used in the present invention preferably has a thickness of 18 μm or less, more preferably 12 μm or less. Also, considering handling of a copper foil without a carrier, the thickness is preferably 9 μm or more. However, a manganese layer or a manganese alloy layer may be formed between the carrier and the copper foil with a carrier. By transferring this, a surface layer mainly composed of the above-mentioned manganese or manganese alloy can be formed on the laser irradiation surface side. The laser in the present invention preferably has a wavelength of 0.6 μm or more, and is preferably a YAG laser, a carbon dioxide laser or the like. In particular, copper is effective because the carbon dioxide laser absorption rate is extremely low.

Next, the manufacturing method of the present invention will be described. First, as a method for forming a manganese layer or a manganese alloy layer on the surface of a copper foil, it is preferable to form the layer by a physical vapor deposition method or a vapor deposition method such as a chemical vapor deposition method. As this vapor deposition method,
For example, a vacuum evaporation method, a plating method, an ion plating method, a sputtering method, a CVD method and the like can be mentioned, and a physical evaporation method such as a vacuum evaporation method, an ion plating method, and a sputtering method can easily control a thin film, and a copper foil can be used. Suitable for keeping the temperature relatively low. In particular, the vacuum evaporation method is suitable because it has a high film formation rate and is suitable for mass production and can be applied to film formation of many metals.

After the laser drilling process, an etching step for forming a wiring pattern may be performed while the surface layer is left. However, the etching rate of the metal or alloy on the surface layer differs greatly from copper, and fine patterning is performed. May not be possible. Therefore, the metal or alloy layer on the surface is preferably removed by selective etching after laser drilling, and an etching step for wiring patterning is performed.

[0017]

The present invention will be described in more detail with reference to the following examples. First, a manganese layer having a film thickness of 0.1 μm and 0.5 μm was formed on a shiny surface side, which is a laser irradiation side surface of a 12 μm thick electrolytic copper foil (1), by a sputtering method at a film formation rate of 0.5 nm / sec. , 1.0 μm, and 1.5 μm, to form a surface layer (2), thereby obtaining a laminate of copper and manganese as a material for a copper foil with resin. An epoxy resin (3) was adhered to the mat side of this laminate to obtain a copper foil (4) with a resin for laser drilling. FIG. 1 is a schematic sectional view at this time.
As shown. Next, using the above-mentioned resin-coated copper foil at 170 ° C.
Lamination hot pressing was performed under the conditions of × 60 min and 300 MPa to obtain a build-up substrate.

The film thickness of the surface layer is measured by observing the cross section with a scanning electron microscope, and the substance is identified by microscopic X-ray diffraction and ED.
It was performed by S quantitative analysis. Laser irradiation conditions were such that a hole having a diameter of 100 μm was formed using a carbon dioxide laser (wavelength: 10.6 μm). The laser workability was qualitatively evaluated for the way the holes were made, and the blackened copper foil described as a comparative example was used as a reference. The cross section of the hole shape was observed with a scanning electron microscope. As a result of the hole cross-section observation, all the samples exhibited no overhang, exhibited a normal hole shape, and had good laser workability.

As a comparative example, a build-up substrate was manufactured using a resin-coated copper foil that had not been subjected to a surface treatment and a material that had undergone a blackening treatment on the surface. In order for both to penetrate the copper foil, a high-power laser is required, in which case the overhang is large and the laser workability is poor. In particular, it was confirmed that the overhang was remarkably large in the build-up substrate not subjected to the surface treatment.

As described above, the resin-coated copper foil of the present invention
Because of its excellent laser workability, it was confirmed that it was suitable for the copper direct method in which laser drilling was performed directly by laser irradiation.

[0021]

According to the present invention, by providing a resin-coated copper foil capable of laser drilling and a method of manufacturing the same, it is possible to use the conventional infrastructure as it is and to reduce the cost by reducing the number of steps. Adoption of the law becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a copper foil with resin for laser drilling according to the present invention.

[Explanation of symbols]

1. 1. copper foil; 2. surface layer; Resin, 4. Copper foil with resin for laser drilling

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E351 AA01 BB01 BB23 BB24 BB32 BB35 BB49 CC01 DD04 DD18 DD21 GG01 4F100 AB14B AB14C AB17A AB31B AB31C AB33A AK01D AK53 AT00D BA04 BA07 BA10B EH66B EH66A0203 DC04 GA03

Claims (3)

[Claims] 1. A resin-coated copper foil for laser drilling, wherein a surface layer made of one or both of manganese and a manganese alloy is formed on the surface of the copper foil on the laser irradiation side. 2. The copper foil with resin for laser drilling according to claim 1, wherein the thickness of the surface layer is 0.05 μm to 3.0 μm. 3. A method for producing a resin-coated copper foil for laser drilling, comprising a step of forming a manganese layer or a manganese alloy layer on the surface of the copper foil by a vapor deposition method.