JP2022034572A - Manufacturing method for metal clad laminate - Google Patents

Abstract

To provide a manufacturing method for a metal-clad laminate capable of producing a metal-clad laminate in which adhesion of a metal layer to a base material is suppressed.SOLUTION: A manufacturing method for a metal-clad laminate includes a metal layer forming step for forming a metal layer on a base material to manufacture the metal-clad laminate. The metal layer forming step includes a first metal layer forming step, in which a porous first metal layer with voids is formed on the base material, a second metal layer forming step, in which a non-porous second metal layer is formed on the first metal layer, and a third metal layer forming step, in which a third metal layer is formed on the second metal layer by plating.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a metal-clad laminate.

When manufacturing a flexible printed wiring board or the like, a metal-clad laminate in which a metal layer made of a metal such as copper is laminated on a base material is used.

As a method for manufacturing such a metal-clad laminate, for example, Patent Document 1 below includes a step of forming a film obtained by firing copper fine particles on a substrate and a step of plating the film to form a conductive film. A method for forming a conductive film having a conductive film is disclosed.

Japanese Unexamined Patent Publication No. 2013-135089

However, the conductive film forming method described in Patent Document 1 described above has room for improvement in terms of the adhesion of the conductive film to the substrate.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a metal-clad laminate capable of producing a metal-clad laminate in which a decrease in adhesion of a metal layer to a substrate is suppressed. do.

The present inventor has investigated the cause of insufficient adhesion of the conductive film to the substrate in the conductive film forming method described in Patent Document 1. As a result, the present inventor considered that the reason why the adhesiveness of the conductive film to the substrate was insufficient was as follows. That is, in the conductive film forming method described in Patent Document 1, the film has a porous structure having a plurality of voids, and the metal particles constituting this film are buried in a state of being caught on the base material. it is conceivable that. That is, it is considered that the film is in close contact with the base material due to the anchor effect of the metal particles constituting the film. Since the film having this porous structure is plated, when the metal grown by plating enters the voids of the film and grows, the metal eventually reaches the gap between the base material and the film. It penetrates and applies enough stress to separate them between the substrate and the coating. Alternatively, the metal grown by plating applies stress to the metal particles constituting the film. As a result, the present inventor thought that the metal layer might be easily peeled off from the base material. Therefore, as a result of further diligent studies, the present inventor has found that the above problems can be solved by the following inventions.

That is, the present invention is a method for manufacturing a metal-clad laminate including a metal layer forming step of forming a metal layer on a substrate to produce a metal-clad laminate, wherein the metal layer forming step is performed on the substrate. In addition, a first metal layer forming step of forming a porous first metal layer having voids, a second metal layer forming step of forming a non-porous second metal layer on the first metal layer, and the above-mentioned It is a method of manufacturing a metal-clad laminate including a third metal layer forming step of forming a third metal layer on a second metal layer by plating.

According to this method for manufacturing a metal-clad laminate, a porous first metal layer is formed on a base material, a non-porous second metal layer is formed on the first metal layer, and a second metal layer is formed. A third metal layer is formed by plating on the metal layer. In this way, a metal layer having a first metal layer, a second metal layer, and a third metal layer is formed on the base material. At this time, when the third metal layer is formed by plating on the second metal layer, the second metal layer suppresses the plating from entering the voids of the first metal layer. Therefore, even if the metal grows due to plating, it is suppressed that the metal penetrates into the gap between the base material and the first metal layer, and the stress that separates them between the base material and the first metal layer is suppressed. Is suppressed. Therefore, according to the method for manufacturing a metal-clad laminate of the present invention, it is possible to manufacture a metal-clad laminate in which deterioration of the adhesion of the metal layer to the substrate is suppressed.

In the method for manufacturing the metal-clad laminate, the ten-point average surface roughness of the second metal layer is smaller than the ten-point average surface roughness of the first metal layer in the second metal layer forming step. It is preferable to form the second metal layer.

In this case, the surface of the second metal layer is compared with the case where the second metal layer is formed so that the ten-point average surface roughness of the second metal layer is equal to or higher than the ten-point average surface roughness of the first metal layer. The unevenness of the metal becomes smaller, and the current path becomes shorter when a high-frequency current flows. Therefore, the electric resistance of the second metal layer can be further reduced.

In the method for manufacturing a metal-clad laminate, it is preferable that the second metal layer is made of the same metal as the first metal layer in the second metal layer forming step.

In this case, as compared with the case where the first metal layer and the second metal layer are composed of different metals, the metal is melted out from the second metal layer due to moisture or the like entering into the porous first metal layer. It becomes difficult. That is, the corrosion of the second metal layer is sufficiently suppressed. As a result, the increase in the resistance of the second metal layer is suppressed, and the cracking of the second metal layer and the peeling from the first metal layer are sufficiently suppressed.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a method for manufacturing a metal-clad laminate capable of producing a metal-clad laminate in which a decrease in adhesion of a metal layer to a substrate is suppressed.

It is sectional drawing which shows the metal-clad laminated board manufactured by the manufacturing method of the metal-clad laminated board of this invention. It is an enlarged view of the region surrounded by the two-dot chain line A of FIG. It is sectional drawing which shows the 1st metal layer formation process in the manufacturing method of the metal-clad laminated board of this invention. It is sectional drawing which shows the 2nd metal layer formation process in the manufacturing method of the metal-clad laminated board of this invention.

Hereinafter, embodiments of the method for manufacturing a metal-clad laminate of the present invention will be described in detail.

First, the metal-clad laminate manufactured by the method for manufacturing a metal-clad laminate of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing a metal-clad laminate manufactured by the method for manufacturing a metal-clad laminate of the present invention, and FIG. 2 is an enlarged view of a region surrounded by a two-dot chain line A in FIG.

As shown in FIGS. 1 and 2, the metal-clad laminate 100 includes a base material 10 and a metal layer 20 provided on the main surface 10a of the base material 10. The metal layer 20 is provided on the base material 10, a porous first metal layer 21 having a void V, a non-porous second metal layer 22 provided on the first metal layer 21, and a second metal layer 20. It has a third metal layer 23 provided on the two metal layer 22.

Next, a method for manufacturing the metal-clad laminate 100 will be described with reference to FIGS. 1 to 4. FIG. 3 is a cross-sectional view showing a first metal layer forming step in the method for manufacturing a metal-clad laminate of the present invention, and FIG. 4 is a cross-sectional view showing a second metal layer forming step in the method for manufacturing a metal-clad laminate of the present invention. It is a figure.

As shown in FIGS. 1 to 4, the method for manufacturing the metal-clad laminate 100 includes a metal layer forming step of forming the metal layer 20 on the base material 10 to manufacture the metal-clad laminate 100. The metal layer forming step includes a first metal layer forming step of forming a porous first metal layer 21 having voids V on the base material 10, and a non-porous second metal layer 21 on the first metal layer 21. It includes a second metal layer forming step of forming 22 and a third metal layer forming step of forming a third metal layer 33 by plating on the second metal layer 22.

According to the method for manufacturing the metal-clad laminate 100, the porous first metal layer 21 is formed on the base material 10, and the non-porous second metal layer 22 is formed on the first metal layer 21. It is formed, and a third metal layer 23 is formed by plating on the second metal layer 22. In this way, the metal layer 20 having the first metal layer 21, the second metal layer 22, and the third metal layer 23 is formed on the base material 10. At this time, when the third metal layer 23 is formed by plating on the second metal layer 22, the second metal layer 22 suppresses the metal grown by plating from entering the void V of the first metal layer 21. Will be done. Therefore, even if the metal grows by plating, it is suppressed that the metal penetrates into the gap between the base material 10 and the first metal layer 21, and these are suppressed between the base material 10 and the first metal layer 21. It is suppressed that the stress that separates the metal is applied. Therefore, it is possible to manufacture the metal-clad laminated board 100 in which the metal layer 20 is sufficiently suppressed from peeling from the base material 10.

Hereinafter, the first metal layer forming step, the second metal layer forming step, and the third metal layer forming step described above will be described in detail.

<First metal layer forming process>
The first metal layer forming step is a step of forming a porous first metal layer 21 having voids V on the base material 10 (see FIG. 3).

(Base material)
The material constituting the base material 10 is not particularly limited, but examples of the material constituting the base material 10 include non-thermoplastic polyimide resins; thermoplastic polyethylene terephthalates (PET) and liquid crystal polymers (LCP). , Cycloolefin polymer (COP); and fluororesins such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) and the like.

When the metal-clad laminate 100 is used for high-frequency applications, a resin having a small dielectric constant is preferable. In this case, a part of the electric energy is less likely to become heat and is less likely to be lost. Examples of such a resin having a small dielectric constant include LCP, COP, and a fluorine-based resin.

When the time of solder reflow is particularly important, a resin having a continuous use temperature of 200 ° C. or higher is preferable as the material constituting the base material 10. Examples of such resins include LCP, COP, and fluororesins.

Further, when the suppression of warpage due to temperature change is important, the material constituting the base material 10 is preferably a resin having a linear expansion coefficient close to the linear expansion coefficient of the first metal layer 21. For example, when the first metal layer is made of copper, LCP or a polyimide resin having a linear expansion coefficient close to the linear expansion coefficient (16 ppm / K) of copper is preferably used.

The average thickness of the base material 10 cannot be unequivocally determined because it depends on the application, but it is usually 25 to 100 μm. The average thickness of the base material 10 can be measured by, for example, the method described in JIS K7130: 1999 "Plastic-Film and Sheet-Thickness Measuring Method".

(First metal layer)
The first metal layer 21 can be obtained by applying, for example, a paste for forming a first metal layer containing metal particles and a solvent on the main surface 10a of the base material 10 and light-baking.

Here, the metal particles preferably include nanoparticles having an average particle size of 1 to 100 nm. The metal particles may be composed of only nanoparticles or may be composed of a mixture of nanoparticles and coarse particles. As the coarse particles, for example, disk particles having a diameter of 1 μm and a thickness of 200 nm can be used. It should be noted that only nanoparticles are dissolved by light irradiation, and coarse particles are not dissolved.

The metal particles are preferably composed only of nanoparticles. In this case, the volume resistivity of the first metal layer 21 can be made smaller. It is considered that this is because when the metal particles are composed only of nanoparticles, all the metal particles are melted by light firing and welded to each other, so that the contact area between the metal particles becomes large.

However, the metal particles may be composed of a mixture of nanoparticles and coarse particles. In this case, since the coarse particles are not dissolved by light firing, the shrinkage of the metal film during light firing can be reduced, the base material 10 warps, and the first metal layer 21 peels off from the base material 10. Can be suppressed.

Examples of the metal constituting the metal particles include gold, silver and copper. Of these, copper is preferable because it is inexpensive.

As the solvent, for example, 3-methoxy-3-methylbutanol, triethylene glycol monomethyl ether, propylene carbonate, 1,3-dimethyl-2-imidazolidinone and the like can be used.

The paste for forming the first metal layer may further contain a dispersant. Examples of the dispersant include polyethylene glycol and polyvinylpyrrolidone.

The coating of the paste for forming the first metal layer can be performed using, for example, a microgravure coating machine or a spin coater.

The paste for forming the first metal layer is preferably subjected to a drying treatment before light firing. When the paste for forming the first metal layer contains a large amount of organic components such as binder, it is preferable to further perform a treatment for removing the organic components. In this case, it is possible to prevent the voids from becoming large due to the gas generated by the decomposition of the organic component during light firing.

Examples of the drying treatment method include a method of heat treatment at about 50 to 100 ° C. As a treatment method for removing organic components, for example, the paste for forming the first metal layer is heat-treated at about 150 ° C., then immersed in dilute sulfuric acid to remove the oxide film, washed with water, and then immersed in isopropyl alcohol. The method can be mentioned.

As an apparatus for performing light firing, for example, "Pulsforge 1300" manufactured by Novacentrix can be used. As the light source used in this device, for example, a xenon lamp or the like can be used.

The irradiation energy of light may be, for example, 0.1 to 100 J / cm ² . The light irradiation time may be 0.1 to 100 ms. The number of irradiations may be one or a plurality of multi-stage irradiations.

The average thickness of the first metal layer 21 is preferably 2x or more, where x is the average particle size of the metal particles constituting the first metal layer 21. In this case, in calculation, two or more metal particles are present on the base material 10, and the second metal layer 22 is not directly formed on the metal particles that are in direct contact with the base material 10. Therefore, the stress due to the second metal layer 22 is less likely to be applied to the metal particles that are in direct contact with the base material 10, and the decrease in the adhesion of the first metal layer 21 to the base material 10 is sufficiently suppressed.

The average thickness of the first metal layer 21 is preferably 5 μm or less. In this case, the void V is larger due to the gas generated in the first metal layer forming paste when the first metal layer forming paste is light-fired, as compared with the case where the average thickness of the first metal layer 21 exceeds 5 μm. Is sufficiently suppressed. It is more preferable that the average thickness of the first metal layer 21 is 1 μm or less.

The average thickness of the first metal layer 21 can be measured, for example, by observing the cross section of the first metal layer 21 with a scanning electron microscope. As a method of obtaining a cross section of the first metal layer 21, there is a method of embedding a metal-clad laminate 100 in a resin and then polishing it.

<Second metal layer forming process>
The second metal layer forming step is a step of forming the non-porous second metal layer 22 on the first metal layer 21 (see FIG. 4). In other words, in the second metal layer forming step, when the third metal layer 23 is formed on the first metal layer 21 by plating, the second metal layer 22 is prevented from passing through the plating. Is the process of forming.

In the second metal layer forming step, the ten-point average surface roughness (R2) of the second metal layer 22 is not particularly limited, but is based on the ten-point average surface roughness (R1) of the first metal layer 21. It is preferable to form the second metal layer 22 so as to be smaller.

In this case, as compared with the case where the second metal layer 22 is formed so that R2 is R1 or more, the unevenness of the surface of the second metal layer 22 becomes smaller, and the current path becomes shorter when a high frequency current flows. Therefore, the electric resistance of the second metal layer 22 can be further reduced.

R1-R2 is not particularly limited, but is preferably 0.03 μm or more. In this case, the electrical resistance of the second metal layer 22 can be further reduced. However, R1-R2 is preferably 0.1 μm or less.

Specifically, R2 is preferably 0.01 μm or more. However, R2 is preferably 0.2 μm or less.

Further, the second metal layer 22 may be formed so as to cover only the main surface of the first metal layer 21 opposite to the base material 10 (hereinafter, referred to as “opposite main surface”), but the opposite is true. It is preferably formed so as to cover not only the side main surface but also the side surface connecting the opposite main surface and the interface between the base material 10 and the first metal layer 21. In this case, since the voids of the first metal layer 21 are closed by the second metal layer 22, the metal grown by plating when the third metal layer 23 is formed on the second metal layer 22 is the first metal. It is possible to prevent the layer 21 from entering the voids.

The metal constituting the second metal layer 22 is not particularly limited, but when the metal-clad laminate 100 is used for high-frequency applications, it is preferably a non-magnetic metal. In this case, the skin effect prevents the thickness of the portion of the second metal layer 22 through which the current flows from becoming smaller, so that the electrical resistance of the second metal layer 22 can be reduced. Non-magnetic metals include, for example, gold, silver and copper. Of these, copper is preferable because it is inexpensive.

The second metal layer 22 is preferably made of the same metal as the first metal layer 21.

In this case, as compared with the case where the first metal layer 21 and the second metal layer 22 are made of different metals, the metal is released from the second metal layer 22 due to moisture or the like entering into the porous first metal layer. It becomes difficult to melt out. That is, the corrosion of the second metal layer 22 is sufficiently suppressed. As a result, the increase in the resistance of the second metal layer 22 is suppressed, and the cracking of the second metal layer 22 and the peeling from the first metal layer 21 are sufficiently suppressed.

The non-porous second metal layer 22 is preferably formed by sputtering. In this case, when the second metal layer 22 is formed by sputtering, unlike the case where the second metal layer 22 is formed by plating, the metal formed by sputtering enters the voids of the porous first metal layer 21. It can be sufficiently suppressed.

The average thickness of the second metal layer 22 is not particularly limited, but is preferably one or more times the average particle size of the metal particles constituting the first metal layer 21.

Specifically, the average thickness of the second metal layer 22 may be 1 to 20 μm.

The average thickness of the second metal layer 22 can be adjusted by the time of sputtering.

The average thickness of the second metal layer 22 can be measured by the same method as that of the first metal layer 21.

<Third metal layer forming process>
The third metal layer forming step is a step of forming the third metal layer 33 on the second metal layer 22 by plating (see FIG. 1).

The metal constituting the third metal layer 23 is not particularly limited. Examples of such metals include gold, silver and copper. Of these, copper is preferable because it is inexpensive.

The plating solution used for plating is not particularly limited, but is preferably a copper sulfate solution. In this case, the third metal layer 23 having a smooth surface is uniformly adhered to the surface of the second metal layer 22. A brightener may be added to the plating solution.

Examples of plating include electroplating and electroless plating. Above all, electroplating is preferable from the viewpoint of increasing the thickness of the third metal layer 23 in a short time.

When the plating is electroplating, the current density is not particularly limited, but is usually 1 to 4 A / dm ² .

The present invention is not limited to the above embodiment. For example, in the above embodiment, the metal layer 20 is formed only on the main surface 10a of the base material 10, but the metal layer 20 may be formed on the main surface opposite to the main surface 10a of the base material 10. ..

Further, in the above embodiment, the first metal layer 21 is formed by light firing of the paste for forming the first metal layer, but the first metal layer 21 is not necessarily formed by light firing of the paste for forming the first metal layer. It does not have to be formed. For example, the first metal layer 21 can also be formed by thermal firing.

Hereinafter, the content of the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

(Example 1)
First, a substrate having an average thickness of 25 μm was prepared. As the base material, a polyimide film (trade name "Apical 25NPI", manufactured by Kaneka Corporation) was used.

Next, a paste containing metal particles consisting only of copper nanoparticles having an average particle size of 70 nm, a solvent made of hexylene glycol, and a dispersant made of polyethylene glycol was prepared, and the paste was applied onto the main surface of the base material with a spin coater. Then, it was dried at 50 ° C. for 10 minutes.

Next, the paste was light-fired with a light-burning device (product name "PulsForge 1300", manufactured by Novacentrick) using a xenon flash lamp as a light source to obtain a first metal layer made of copper. The average thickness of the first metal layer obtained after light firing was 1 μm.

Next, using a vacuum vapor deposition apparatus (product name "JEOL JFC-1200", manufactured by JEOL Ltd.), copper sputtering is performed so as to cover the surface of the first metal layer to form a second metal layer. I got a body. The average thickness of the second metal layer was 0.1 μm.

Next, the structure obtained as described above was sequentially pretreated with 10% by mass sulfuric acid and distilled water, and then copper plating was performed on the second metal layer of the structure. Copper plating was performed by immersing the above structure in a plating solution and electroplating. At this time, the composition of the plating solution was 100 g / L of copper sulfate pentahydrate, 180 g / L of sulfuric acid, 0.12 mL / L of hydrochloric acid, and distilled water (residual). The temperature of the plating solution was 25 ° C., and the current density was 4.0 A / dm ² . In this way, the third metal layer was formed on the second metal layer, and a metal-clad laminate was produced.

(Comparative Example 1)
A metal-clad laminate was produced in the same manner as in Example 1 except that the second metal layer was not formed on the first metal layer.

[Evaluation of adhesion of metal layer to substrate]
The metal-clad laminates obtained in Example 1 and Comparative Example 1 were tested for adhesion of the metal layer to the substrate by a cross-cut method (JIS-5600-5-6). Specifically, a grid cut was made in the metal layer, 100 squares of 1 mm × 1 mm square were formed, an adhesive tape was attached to the metal layer, and then the metal layer was peeled off to observe the surface of the metal layer. Then, the number of peeled cells in the adhesive tape was calculated. The results are shown in Table 1.

From the results shown in Table 1, in the metal-clad laminate obtained in Example 1, the number of cells peeled off in the adhesion test was 0, whereas the metal-clad laminate obtained in Comparative Example 1 was obtained. As for the plate, the number of cells peeled off in the adhesion test was 100 (all).

From the above, it was confirmed that according to the method for producing a metal-clad laminate of the present invention, it is possible to produce a metal-clad laminate in which deterioration of the adhesion of the metal layer to the substrate is suppressed.

10 ... Base material 20 ... Metal layer 21 ... First metal layer 22 ... Second metal layer 23 ... Third metal layer 100 ... Metal-clad laminate V ... Voids

Claims (3)

A method for manufacturing a metal-clad laminate, which comprises a metal layer forming step of forming a metal layer on a base material to produce a metal-clad laminate.
The metal layer forming step
A first metal layer forming step of forming a porous first metal layer having voids on the base material,
A second metal layer forming step of forming a non-porous second metal layer on the first metal layer,
A method for manufacturing a metal-clad laminate, comprising a third metal layer forming step of forming a third metal layer on the second metal layer by plating. Claimed in the second metal layer forming step, the second metal layer is formed so that the ten-point average surface roughness of the second metal layer is smaller than the ten-point average surface roughness of the first metal layer. The method for manufacturing a metal-clad laminate according to 1. The method for manufacturing a metal-clad laminate according to claim 1 or 2, wherein in the second metal layer forming step, the second metal layer is made of the same metal as the first metal layer.

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