TWI805902B - Surface treated copper foil, copper clad laminate and printed circuit board - Google Patents

Abstract

The present invention provides a surface-treated copper foil that achieves a high level of adhesion, reliability, and reduction in transmission loss on a non-roughened surface. The surface-treated copper foil has: a copper foil main body 1, one of its two main surfaces is a roughened surface 1a formed by roughening treatment, and the other is a non-roughened surface 1b; and an antirust layer 10 formed On the non-roughened surface 1b of the copper foil main body 1. The antirust layer 10 has a metallic zinc layer 11 composed of metallic zinc, a zinc oxide layer 12 composed of zinc oxide, a zinc hydroxide layer 13 composed of zinc hydroxide, and a chromate layer composed of chromium compounds 14. The layers of the antirust layer 10 are laminated in the order of the metal zinc layer 11, the zinc oxide layer 12, the zinc hydroxide layer 13, and the chromate layer 14 from the copper foil main body 1 side.

Description

Surface treated copper foil, copper clad laminate and printed circuit board

The invention relates to a surface-treated copper foil. Furthermore, the present invention relates to a copper-clad laminate and a printed wiring board using the aforementioned surface-treated copper foil.

In various electronic equipment, printed circuit boards are used as substrates and connecting materials, and copper foil is usually used for the conductive layer of printed circuit boards. As copper foil used in printed circuit boards, rolled copper foil and electrolytic copper foil are generally used.

Rolled copper foil used as copper foil for printed wiring boards contains additives such as metals as essential components in order to suppress crystal growth due to the heat history given during the manufacturing process. Therefore, there are cases where the original electrical conductivity of the copper foil is lowered, and the manufacturing cost is also higher than that of the electrolytic copper foil. Therefore, as copper foil for printed wiring boards, electrolytic copper foil with high conductivity, excellent productivity, and easy thinning tends to be widely used.

In recent years, with the further increase of mobile communication traffic, etc., the transmission of high-frequency signals from several GHz to 100 GHz by printed circuit boards has increased. It is known that the high-frequency signal has the following tendency: the higher the frequency, the more high-speed and large-capacity communication can be carried out. On the other hand, the signal only passes through the surface of the conductive layer of the printed circuit board (skin effect). If the high-frequency signal only passes through the surface, it will be more affected by the surface shape of the copper foil and the anti-rust layer. That is, if the surface roughness of copper foil is large, the transmission length of a signal will become long, and a transmission loss will become large. In addition, if the electrical conductivity is lower than that of copper or if there are many dissimilar metals with magnetism on the surface of the copper foil, the transmission loss will increase. Therefore, from the viewpoint of reducing the transmission loss, the smoother the surface of the copper foil and the smaller the roughness, the better, and the less the amount of adhesion of dissimilar metals, the better.

On the other hand, a printed wiring board is generally produced by laminating a resin film containing epoxy resin, polyphenylene ether, etc., and copper foil by high-temperature pressing, and forming a circuit pattern by etching. Therefore, in order to improve the adhesion with the resin film, a roughening treatment layer is often provided on the surface of the copper foil. The so-called roughening treatment is to adjust the surface shape of copper foil (including the shape of granular protrusions made of copper or various alloys, and the porous shape obtained by etching copper foil) to increase the roughness.

In addition, as the reliability of printed circuit boards, it is necessary to maintain good adhesion between copper foil and resin during heating (such as heat resistance test) and acid immersion (such as acid immersion test), so copper Foils often have an antirust layer containing dissimilar metals represented by nickel, zinc, and chromium.

However, from the viewpoint of reducing transmission loss, these roughening treatment layers and anti-rust layers are the main causes of adverse effects. Under such circumstances, a lot of research has been conducted so far in order to balance the adhesion, reliability, and reduction of transmission loss.

For example, in Patent Document 1, a technique of increasing the surface area of copper foil by using fine unevenness is proposed; in Patent Document 2, a technique of making roughened particles into a special shape is proposed; in Patent Document 3, a technique of using The technique of forming fine roughened particles by alloy plating with nickel, cobalt, etc., is proposed in Patent Document 4 to form fine roughened particles and cover the roughened particles with an anti-oxidation treatment layer containing molybdenum and cobalt technology above all else.

Based on the above facts, in recent years, it has been required to achieve a higher level of adhesion, reliability, and reduction of transmission loss. Based on this, studies focusing on the non-roughened surface of copper foil are being conducted.

In addition, in this specification, the surface which has a roughening process layer of copper foil is called a "roughening surface", and the surface which does not have a roughening process layer is called a "non-roughening surface." The non-roughened surface of the electrolytic copper foil has a shape (shiny surface, hereinafter referred to as "S surface") in which the grinding marks of the drum surface as the cathode are transferred according to the manufacturing method, or is in contact with the electrolyte, Any of the plating deposit shapes (mat surface, hereinafter referred to as "M surface") corresponding to various organic additives. The non-roughened surface of the rolled copper foil becomes the surface shape of the rolled finish.

When making a multilayer printed circuit board, as with the roughened surface, the non-roughened surface also requires adhesion and reliability with the resin film (that is, the adhesion between the copper foil and the resin during heating and acid immersion) ). In addition, in this specification, the adhesion and reliability of the copper foil on the non-roughened surface and the resin film (adhesion between the copper foil and the resin during heating and acid dipping) are recorded as the non-roughened surface of the copper foil. The "inner layer adhesion" of the chemical surface.

After making the circuit pattern, the non-roughened surface of the copper foil is half-etched as needed, and then, in order to improve the adhesion of the inner layer, the non-roughened surface of the copper foil and the etched end surface of the circuit pattern are blackened, micro-etched, etc. Inner treatment. Blackening treatment is a method of forming copper oxides and reducing copper oxides to form copper protrusions. Micro-etching is a method of dissolving copper foil into a porous shape using sulfuric acid-hydrogen peroxide and organic acid treatment solutions. A method of surface roughening. However, no matter which method is used, the roughness of the copper foil surface is increased, which becomes one of the main reasons for increasing the transmission loss.

In addition, there are also cases where the chemical adhesion treatment represented by GliCAP of Shikoku Chemical Industry Co., Ltd., which does not accompany the increase in the surface roughness of the copper foil, is used as the inner layer treatment, but the adhesion of the inner layer is poor. , and the effect of improving the adhesion of the inner layer varies greatly depending on the type of resin attached.

These increases in the roughness of the non-roughened surface caused by the inner layer treatment and the accompanying increase in transmission loss are phenomena that have been recognized for a long time. However, in the conventional copper foil, since the roughened surface has a greater influence on the increase in transmission loss than the non-roughened surface, no effort has been made to improve the non-roughened surface. In recent years, the improvement and development of the roughened surface, relatively, the non-roughened surface has a greater impact on the increase in transmission loss. In the process, it is required to take into account the adhesion, reliability and transmission at a higher level than before. The reduction of the loss, thus the improvement of the non-roughened surface is gradually paid attention to.

For example, Non-Patent Document 1 discloses that by using microetching as an inner layer process, especially the transmission loss increases, and the higher the frequency of the signal, the more conspicuous the effect is. On the other hand, it is reported that micro-etching is necessary to ensure the adhesion of the inner layer.

In addition, Patent Document 5 discloses a method of performing surface treatment using tin, nickel, or any of these alloys instead of blackening treatment as an inner layer treatment, and then applying an undercoat resin. prior art literature patent documents

Patent Document 1: Japanese Patent No. 6182584 Patent Document 2: Japanese Patent No. 5972486 Patent Document 3: Japanese Patent Laid-Open No. 2015-61939 Patent Document 4: Japanese Patent No. 6083619 Patent Document 5: Japanese Patent No. 5129843 Patent Document 6: Japanese Patent No. 6182584 non-patent literature

Non-Patent Document 1: Kaoru Sugimoto et al., "Influence of Surface Roughness of Conductors in Multilayer Printed Wiring Boards on High-Speed Transmission", Surface Technology, Surface Technology Association, 2018, Vol. 69, No. 1, p.38–45

[Problem to be Solved by the Invention] As mentioned above, there is currently a trade-off relationship between the reduction of the inner layer adhesion and the transmission loss of the non-roughened surface of the copper foil, and it is impossible to obtain a copper foil that meets the high level of demand in recent years. The use of magnetic metals such as nickel as an inner layer treatment will lead to a large increase in transmission loss, and the coating of primer resin will not only affect the transmission loss due to the characteristics of the primer resin, but also significantly increase the manufacturing cost.

In fact, the status quo is to sacrifice any characteristic, according to the type of resin attached and the customer's manufacturing process, through trial and error: the optimization of the previous inner layer treatment; the non-roughened surface of the previous copper foil Optimization of shape and anti-rust layer.

The object of the present invention is to provide a surface-treated copper foil, a copper-clad laminate, and a printed wiring board that balance high-level adhesion, reliability, and transmission loss reduction of a non-roughened surface.

[Technical means to solve the problem] A surface-treated copper foil according to an aspect of the present invention is the following surface-treated copper foil, which has: a copper foil main body, one of the two main surfaces of which is roughened by roughening treatment. The other is the non-roughened surface; and the anti-rust layer is formed on the non-roughened surface of the copper foil main body; the main purpose of the surface-treated copper foil is that the anti-rust layer has metallic zinc layer, a zinc oxide layer composed of zinc oxide, a zinc hydroxide layer composed of zinc hydroxide, and a chromate layer composed of chromium compounds, these layers of the antirust layer are from the copper foil main body side Laminate layers in the order of metal zinc layer, zinc oxide layer, zinc hydroxide layer, and chromate layer.

The gist of the copper-clad laminate of another aspect of the present invention is that it includes the surface-treated copper foil of the above-mentioned one aspect, and a resin base material laminated on the roughened surface side of the surface-treated copper foil.

The gist of the printed wiring board of still another aspect of the present invention is that it has the copper-clad laminated board of the above-mentioned another aspect.

[Advantageous Effects of the Invention] According to the present invention, the adhesion, reliability, and reduction of transmission loss of the non-roughened surface can be achieved at a high level.

One embodiment of the present invention will be described. In addition, this embodiment shows an example of this invention, Various changes and improvements can be added to this embodiment, The form to which various changes or improvements were added can also be included in this invention.

In order to solve the above-mentioned problems, the inventors of the present invention paid attention to the antirust layer of the non-roughened surface of copper foil. Previously, electrogalvanizing was usually performed on the non-roughened surface of copper foil, and then either or both of acid chromate treatment and alkaline chromate treatment were performed. Regarding the antirust layer formed in this way, it is implied that a part of zinc hydroxide and zinc oxide are contained in addition to the chromate component and metallic zinc, but the amount is extremely small. It exists in the form of zinc hydroxide and zinc oxide.

Accordingly, the inventors of the present invention conducted in-depth research and found that: by forming the antirust layer having a chromate layer, a zinc hydroxide layer, a zinc oxide layer, and a metal zinc layer from the side of the main body of the copper foil according to the metal Zinc layer, zinc oxide layer, zinc hydroxide layer, and chromate layer are arranged in order, which can take into account the reduction of inner layer adhesion and transmission loss at a very high level.

That is, the surface-treated copper foil of this embodiment is a surface-treated copper foil that includes a copper foil main body, one of its two main surfaces is a roughened surface formed by roughening treatment, and the other is a non-roughened surface. a roughened surface; and an antirust layer formed on the non-roughened surface of the copper foil main body. Furthermore, the antirust layer has a metallic zinc layer composed of metallic zinc, a zinc oxide layer composed of zinc oxide, a zinc hydroxide layer composed of zinc hydroxide, and a chromate layer composed of chromium compounds, These layers of the antirust layer are laminated in the order of the metal zinc layer, the zinc oxide layer, the zinc hydroxide layer, and the chromate layer from the copper foil main body side.

In addition, the antirust layer may consist only of these four layers, and may have another layer together with four layers.

In addition, the metal zinc layer, zinc oxide layer, and zinc hydroxide layer may contain unavoidable impurities together with metal zinc, zinc oxide, and zinc hydroxide, respectively. Examples of unavoidable impurities contained in these layers include lead, iron, cadmium, tin, chlorine, or compounds thereof. The chromate layer also sometimes contains unavoidable impurities together with chromium compounds.

In addition, the zinc oxide layer and the zinc hydroxide layer may contain indefinite compounds of zinc oxide and zinc hydroxide, respectively.

Hereinafter, an example of the surface-treated copper foil of the present embodiment will be described in detail with reference to FIG. 1 . On the non-roughened surface 1b side of the copper foil main body 1, a metal zinc layer 11 is first provided. The metal zinc layer 11 is a base metal, so it plays the role of sacrificial corrosion resistance and inhibits the corrosion of other metals in contact. In addition, it is effective in preventing the decrease of adhesion force during acid immersion.

Then, a zinc oxide layer 12 is disposed directly on the metal zinc layer 11 . Zinc oxide is composed of zinc oxide (ZnO), for example. It is considered that ZnO has a wurtzite structure with high ion binding property and forms a dense layer. It was found that covering the lower metal zinc layer 11 with the zinc oxide layer 12 effectively prevents the decrease of the adhesion force in the heat resistance test and the acid immersion test.

In addition, the higher the heating temperature and the longer the heating time applied to the printed circuit board, the more the metal zinc will diffuse with the copper of the copper foil main body 1 to form a copper-zinc alloy, which will damage the color tone and adhesion of the appearance. It was found that zinc oxide and copper do not diffuse with each other, and therefore, by having the zinc oxide layer 12, adverse effects caused by the formation of the copper-zinc alloy can be suppressed to a minimum.

Then, a zinc hydroxide layer 13 is provided directly on the zinc oxide layer 12 . Zinc hydroxide is, for example, zinc hydroxide (Zn(OH) ₂ ). Zn(OH) ₂ is a gel-like substance containing water molecules, and it was found that in the subsequent chromate treatment, it has the effect of making the chromate film (chromate layer 14) adhere more uniformly and firmly.

Then, a chromate layer 14 is provided directly on top of the zinc hydroxide layer 13 . The chromate layer 14 is an anti-corrosion film composed of chromium oxides and hydroxides, and the chromium oxides and hydroxides are formed in an acidic or alkaline treatment solution containing chromium (VI) ions. It is formed by cathodic electrolysis or simple impregnation. The chromate layer 14 serves as a bonding point with functional groups of resins, especially polyphenylene ether resins, improves adhesion and effectively prevents reduction in adhesion during heat resistance tests and acid immersion tests. It was found that by the presence of the zinc hydroxide layer 13 underneath, a denser and more uniform chromate layer 14 can be formed than before.

As mentioned above, by setting the antirust layer 10 of the structure consisting of chromate layer 14/zinc hydroxide layer 13/zinc oxide layer 12/metal zinc layer 11 on the copper foil main body 1, instead of the inner layer Increasing the roughness of the non-roughened surface 1b of the copper foil main body 1 during the treatment can effectively improve the adhesion of the inner layer. It is especially important that the layers constituting the antirust layer 10 adopt a layer structure without mixing, and it is found that the adhesion of the inner layer can be kept well with less adhesion of chromium and zinc, and the transmission loss can be reduced more effectively. .

This high-level surface-treated copper foil, which takes into account both the inner layer adhesion and the reduction of transmission loss, also exerts its effect when using a process that does not perform inner layer treatment. Recently, for example, in part of the mass build-up process and the pad via process, for the purpose of process simplification and cost reduction, there are increasing cases where circuits are produced without performing full-surface polishing and microetching before resist formation. Plate, inner layer treatment, omission of half-etching, partial implementation of electroless plating, etc. Even in this case, the problem of poor adhesion of the inner layer due to no inner layer treatment, and the problem of increased transmission loss due to surface treatment of chromium and zinc on the non-roughened surface of the copper foil can be solved.

In addition, compared with the previous method of performing inner layer treatment after making the circuit pattern, there are also the following advantages: by pre-setting the zinc hydroxide layer 13, zinc oxide The method of the antirust layer 10 of the layer 12 and the metal zinc layer 11 can be completed with fewer processes for making a printed circuit board, which is excellent in reducing costs and improving productivity.

The surface-treated copper foil of this embodiment balances the adhesion, reliability, and transmission loss reduction of the non-roughened surface 1b at a high level, so it is suitable as, for example, copper-clad laminates and printed circuit boards for high-frequency transmission. Especially the surface-treated copper foil used in multilayer printed circuit boards). That is, the copper-clad laminated board of this embodiment is equipped with the surface-treated copper foil of this embodiment, and the resin base material laminated|stacked on the roughened surface 1a side of the surface-treated copper foil of this embodiment. Moreover, the printed wiring board of this embodiment is equipped with the copper clad laminated board of this embodiment.

In the surface-treated copper foil of this embodiment, an electrolytic copper foil can be used as the copper foil main body 1 . In addition, the average height of the roughened particles on the roughened surface 1a of the copper foil main body 1 can be set within a range of not less than 0.2 µm and not more than 0.8 µm. Furthermore, the ten-point average roughness Rzjis of the non-roughened surface 1b of the copper foil main body 1 can be set to 1.5 µm or less.

The copper foil used as the copper foil main body 1 is preferably the ten-point average roughness Rzjis measured by a stylus-type roughness meter as specified in JIS B0601 (2001) before roughening treatment. 1.5 µm or less. If the ten-point average roughness Rzjis is large, there is a concern that the transmission loss will increase.

When manufacturing the surface-treated copper foil of this embodiment, the roughening process is given to the main surface of one of copper foils first. Copper roughening plating is mentioned as a representative example of roughening process. In copper roughening plating, a copper sulfate plating solution is used. The sulfuric acid concentration of the copper sulfate plating solution is preferably from 50 g/L to 250 g/L, more preferably from 70 g/L to 200 g/L. If the concentration of sulfuric acid in the copper sulfate plating solution is lower than 50 g/L, there is a concern that the electrical conductivity will decrease and the electrodepositability of the roughened particles will deteriorate. If the concentration of sulfuric acid in the copper sulfate plating solution is higher than 250 g/L, there is concern about the corrosion of equipment that promotes copper roughening plating.

The copper concentration of the copper sulfate plating solution is preferably from 6 g/L to 100 g/L, more preferably from 10 g/L to 50 g/L. If the copper concentration of the copper sulfate plating solution is lower than 6 g/L, there is a concern that the electrodepositability of the roughened particles will deteriorate. If the copper concentration of the copper sulfate plating solution is higher than 100 g/L, a larger current is required to plate it into particles, which is also unrealistic in terms of equipment.

In the copper sulfate plating solution, organic additives or inorganic additives may also be added. When high-molecular polysaccharides are added as organic additives, the diffusion-limited current density becomes small, and roughened particles are likely to be generated even under lower current density conditions. In addition, adding salts that are less water-soluble than copper sulfate and noble metal ions as inorganic additives can increase the number of roughened copper particles.

The current density in copper roughening plating is preferably 5 A/dm ² to 120 A/dm ² , more preferably 30 A/dm ² to 100 A/dm ² . If the current density is less than 5 A/dm ² , the processing will take time, so there is a concern that the productivity will decrease. If the current density is higher than 120 A/dm ² , there is a concern that the electrodepositability of the roughened particles will deteriorate.

After the roughening treatment, a coating plating treatment for covering the roughened particles and improving the adhesion between the roughened particles and the copper foil may be performed. In this case, the above-mentioned copper sulfate plating solution can also be used. The uniform electrodeposition of the roughened particles can also be improved by further repeating the double-layer treatment several times.

In addition, the roughening process can also be performed by methods other than copper roughening plating. Examples include: roughening treatment by dissimilar metal plating or alloy plating, roughening treatment by etching treatment, roughening treatment by oxidizing the surface of copper foil with an oxidizing agent or adjusting the atmosphere to roughen the surface , roughening treatment for roughening the surface by re-reducing the oxidized surface, roughening treatment based on treatment combining these, and the like.

Then, the antirust layer 10 is provided on the non-roughened surface 1b of the said copper foil. First, the metal zinc layer 11 is provided on the non-roughened surface 1b of the copper foil main body 1 . The formation of the metal zinc layer 11 is preferably performed by electro-galvanizing. As the zinc plating solution, for example, an alkaline zinc plating solution is used. The zinc concentration of the alkaline zinc plating solution is preferably 2 g/L to 10 g/L. If the zinc concentration of the alkaline zinc plating solution is lower than 2 g/L, there is a concern that the current efficiency of zinc will decrease and the productivity will decrease. If the zinc concentration of the alkaline zinc plating solution is higher than 10 g/L, precipitation is easily formed in the alkaline zinc plating solution, and there is concern that the stability of the alkaline zinc plating solution will decrease.

The sodium hydroxide (NaOH) concentration of the alkaline zinc plating solution is preferably 25 g/L to 45 g/L. If the sodium hydroxide concentration of the alkaline zinc plating solution is lower than 25 g/L, there is a concern that the conductivity of the alkaline zinc plating solution will decrease and the productivity will decrease. If the concentration of sodium hydroxide in the alkaline zinc plating solution is higher than 40 g/L, it is easy to redissolve the zinc that has been plated, and it is difficult to obtain a normal and uniform zinc plating film. The current density during electrogalvanizing is preferably 0.1 A/dm ² to 1 A/dm ² , and the treatment time is preferably 2 to 5 seconds.

Then, the zinc oxide layer 12 is provided on the metal zinc layer 11 . Anodic oxidation treatment is mentioned as an example of the method of forming the zinc oxide layer 12 . By performing anodic oxidation treatment under appropriate conditions, the zinc on the outermost layer of the zinc metal layer is oxidized to form a dense zinc oxide layer 12 . As an anodizing solution, for example, a mixed solution of sodium hydroxide and sodium carbonate (Na ₂ CO ₃ ) can be used. The sodium hydroxide concentration of the mixed solution is preferably 2 g/L to 10 g/L. If the sodium hydroxide concentration of the mixed solution is lower than 2 g/L, the zinc oxide will easily become rough and messy. If the sodium hydroxide concentration of the mixed solution is higher than 10 g/L, it is worried that the yield of zinc oxide will decrease. The sodium carbonate concentration of the mixed solution is preferably in the range of 30 g/L to 70 g/L. It is also related to the concentration of sodium hydroxide, but if it deviates from this concentration range, the zinc oxide will easily become rough and messy. Oxalic acid and ammonium borate are also used in the anodizing treatment solution.

The current density in the anodizing treatment is preferably 1 A/dm ² to 10 A/dm ² , and the treatment time is preferably 2 to 20 seconds. If the current density and treatment time are too small, the zinc oxide layer 12 may not be formed sufficiently, but if the anodic oxidation treatment current density and time are too large, there may be a concern that almost all the metal zinc layer 11 may be oxidized.

As an example of another method of forming the zinc oxide layer 12, a high temperature oxidation treatment can be mentioned. Specifically, it is a method of oxidizing the metal zinc layer 11 in dry air at about 80° C. to 130° C. for about 2 to 5 seconds. If the temperature and time of the high-temperature oxidation treatment are too short, there may be concerns that the zinc oxide layer 12 may not be formed sufficiently, but if the temperature and time of the high-temperature oxidation treatment are too large, there may be a concern that almost all of the metallic zinc layer 11 may be oxidized. The conditions of high temperature oxidation treatment need to be properly adjusted according to the amount of metal zinc attached.

Then, a zinc hydroxide layer 13 is provided on the zinc oxide layer 12 . As an example of the method of forming the zinc hydroxide layer 13, a high temperature steam process is mentioned. By exposing the zinc oxide layer 12 to high temperature water vapor, the zinc hydroxide layer 13 is formed on the outermost layer of the zinc oxide layer 12 . The temperature of high-temperature steam treatment is preferably 70°C to 100°C, and the humidity is preferably above 80%RH. The treatment time of the high temperature steam treatment is preferably 1 to 4 seconds.

As an example of another method of forming the zinc hydroxide layer 13 , a hydrogen generation process in which the copper foil on which the zinc oxide layer 12 is formed is used as an electrode and subjected to cathodic polarization in a neutral aqueous solution is mentioned. For example, cathodic polarization is performed in potassium sulfate (K ₂ SO ₄ ), sodium sulfate (Na ₂ SO ₄ ) neutral brine solution at a current density in the range of 0.1 A/dm ² to 1 A/dm ² . By generating hydrogen on the surface of the copper foil (electrode) on which the zinc oxide layer 12 is formed, the zinc hydroxide layer 13 is formed on the outermost layer. The concentration of the neutral salt in the neutral saline solution is preferably in the range of about 0.5 mol/L to 2 mol/L. The processing time of the hydrogen generation processing is preferably in the range of about 1 to 5 seconds.

Then, a chromate layer 14 is provided on the zinc hydroxide layer 13 . The chromate treatment for forming the chromate layer 14 is roughly divided into two types: acid chromate treatment and alkaline chromate treatment. By performing either or both of these two treatments, a chromate layer 14 composed of a chromium compound is formed on the zinc hydroxide layer 13 .

The so-called acid chromate treatment refers to the treatment of immersing copper foil in acidic chromic anhydride (VI) aqueous solution, or the treatment of cathodic polarization using copper foil as an electrode in acidic chromic anhydride (VI) aqueous solution. The chromium (VI) concentration of the acidic chromic anhydride (VI) aqueous solution is preferably 1 g/L to 8 g/L. If the concentration of chromium (VI) is lower than 1 g/L, it will be difficult to obtain a sufficient amount of chromium adhesion, and if it is higher than 8 g/L, it will increase the risk of operation and the cost of waste liquid treatment, so it is not preferable.

The pH value of the acidic aqueous solution of chromic anhydride (VI) is preferably in the range of 2-5. If the pH of the acidic chromic anhydride (VI) aqueous solution is lower than 2, the material of the lower layer may be excessively eluted, which is not preferable. If the pH value of the acidic chromic anhydride (VI) aqueous solution is higher than 5, it is difficult to obtain sufficient chromium adhesion. Sulfuric acid can be used for pH adjustment.

The current density at the time of cathodic polarization is preferably 2 A/dm ² to 10 A/dm ² . The immersion time or the treatment time of cathodic polarization also depends on the current density, but is preferably 2 to 8 seconds. When the treatment time of cathodic polarization or the current density is too large, the material of the lower layer may be excessively eluted, so it is not preferable. When the treatment time of cathodic polarization or the current density is too small, it is difficult to obtain sufficient chromium adhesion. The liquid temperature of the acidic aqueous solution of chromic anhydride (VI) is preferably 25°C to 40°C.

The so-called alkaline chromate treatment refers to the treatment of cathodic polarization using copper foil as an electrode in an alkaline chromic anhydride (VI) aqueous solution. The concentration of chromium (VI) in the basic aqueous solution of chromic anhydride (VI) is preferably 1 g/L to 8 g/L. If the concentration of chromium (VI) is lower than 1 g/L, it will be difficult to obtain a sufficient amount of chromium adhesion, and if it is higher than 8 g/L, it will increase the risk of operation and the cost of waste liquid treatment, so it is not preferable.

The pH value of the basic aqueous solution of chromic anhydride (VI) is preferably in the range of 9-14. If the pH value of the alkaline aqueous solution of chromic anhydride (VI) is lower than 9, it is difficult to obtain sufficient chromium adhesion. If the pH value of the alkaline chromic anhydride (VI) aqueous solution is higher than 14, the corrosion of the equipment for alkaline chromate treatment will become high, so it is not practical. For pH adjustment, simple alkaline salts such as sodium hydroxide and potassium hydroxide can be used.

In addition, zinc can also be added to the alkaline chromic anhydride (VI) aqueous solution. If zinc is added, it can also effectively suppress the excessive dissolution of zinc in the lower layer. The zinc can also be added in the form of zinc oxide. The zinc concentration of the basic aqueous solution of chromic anhydride (VI) is preferably in the range of 2 g/L to 10 g/L.

Organic treatment such as a silane coupling agent may be further performed on the non-roughened surface 1b of the copper foil on which the antirust layer 10 was formed by the above-mentioned series of antirust layer forming treatments. In addition, the antirust layer may be formed on the roughened surface 1a before, after, or simultaneously with the antirust layer forming treatment on the non-roughened surface 1b. The antirust layer formed on the roughened surface 1a may be made of nickel, zinc, chromium, etc., or may have the same composition as that of the antirust layer 10 on the non-roughened surface 1b. In addition, after the antirust layer is formed on the roughened surface 1a, an organic treatment such as a silane coupling agent may be further performed.

The copper-clad laminate of this embodiment is formed using the surface-treated copper foil of this embodiment mentioned above. Such a copper-clad laminate according to this embodiment can be formed by a known method. For example, a copper-clad laminate can be manufactured by laminating on the roughened surface 1a (adhesion surface) of the surface-treated copper foil of this embodiment and adhering it to a resin base material.

Here, as the resin used for the resin base material, polymer resins having various components can be used. For rigid circuit boards or printed circuit boards for semiconductor packages (PKG), phenolic resins and epoxy resins are mainly used. For the flexible substrate, polyimide, polyamideimide can be mainly used. In precision pattern (high density) circuit boards or high-frequency substrates, heat-resistant resins with high glass transition points (Tg) can be used as materials with good dimensional stability, materials with less warpage and distortion, and materials with less thermal shrinkage.

Examples of heat-resistant resins include liquid crystal polymers, polyether ether ketone, polyphenylene sulfide, polyphenylene oxide, polyphenylene oxide, polyether imide, polyether ketone, polyethylene naphthalate Thermoplastic resins such as diester, polyethylene terephthalate, and thermoplastic polyimide, or polymer alloys composed of these, further examples include: polyimide, heat-resistant epoxy resin, bismaleimide Cyanate ester resins such as iminotriazine, thermosetting resins such as thermosetting modified polyphenylene ether, etc. In particular, the resin used for the resin base material of the copper-clad laminate of this embodiment is preferably a polyphenylene ether-based resin. The dielectric loss tangent and relative permittivity of polyphenylene ether resin are small, the thermal stability and chemical stability are excellent, and the adhesion to dissimilar materials is excellent. Therefore, polyphenylene ether-based resins are suitable for use in printed wiring boards as resin base materials.

It is preferable that the printed wiring board of this embodiment is formed using the said copper clad laminated board. Such a printed wiring board of this embodiment can be formed by a known method.

In addition, a printed wiring board can be produced by chemically etching a part of the surface-treated copper foil of the above-mentioned copper-clad laminate board by a usual method to form a desired circuit pattern. In addition, it is of course possible to mount electronic circuit components on the circuit pattern. As electronic circuit components, those usually mounted on electronic printed circuit boards can be used. In addition to individual semiconductor elements, for example, chip resistors, chip capacitors, semiconductor packages (PKG) and the like can be used. [Example]

Examples and comparative examples are shown below, and the present invention will be further described in detail. As the copper foil main body, a double-sided glossy electrolytic copper foil with an Rzjis of 1.0 µm on the M side and an Rzjis of 0.8 µm on the S side was used. Copper roughening plating is performed on the M surface of the copper foil to perform roughening treatment, and further coating plating treatment is performed to produce a rough surface with an average height of roughening particles in the range of 0.2 µm to 0.8 µm. chemically treated copper foil. The average height of the roughened particles was calculated from the scanning electron microscope image (SEM image) of the cross-section of the roughened copper foil according to the method described in Patent Document 6.

The conditions of copper roughening plating are as follows. Copper concentration of copper sulfate plating solution: 35 g/L Sulfuric acid concentration of copper sulfate plating solution: 140 g/L Temperature of copper sulfate plating solution: 27°C Current density: 55 A/dm ² Processing time: 4 seconds

The conditions of the coating plating treatment are as follows. Copper concentration of copper sulfate plating solution: 120 g/L Sulfuric acid concentration of copper sulfate plating solution: 90 g/L Current density: 10 A/dm ² Processing time: 6 seconds

Surface-treated copper foils of Examples 1 to 5 and Comparative Examples 1 to 4 were produced using the roughened copper foil produced in this way. The manufacturing method of each surface-treated copper foil is described below. (Example 1)

The S surface (non-roughened surface) of the roughened copper foil is subjected to the treatments shown in (1), (2), (3) and (4) in the following order to form an antirust layer and obtain surface treated copper. foil.

(1) Electrogalvanizing was performed on the S surface of the roughened copper foil under the conditions shown below. Zinc concentration of alkaline zinc plating solution: 3 g/L Sodium hydroxide concentration of alkaline zinc plating solution: 30 g/L Temperature of alkaline zinc plating solution: 25°C Current density: 0.6 A/dm ² treatment Time: 5 seconds

(2) Anodizing treatment was performed on the S surface of the roughened copper foil under the conditions shown below. Concentration of sodium hydroxide in the anodizing treatment solution: 8 g/L Sodium carbonate concentration in the anodizing treatment solution: 42 g/L Temperature of the anodizing treatment solution: 34°C Current density: 5 A/dm ² Treatment time: 3 seconds

(3) Under the conditions shown below, the S surface of the roughened copper foil was treated with high-temperature steam. Temperature: 85°C Humidity: 90%RH Processing time: 3 seconds

(4) Under the conditions shown below, acid chromate treatment was given to the S surface of the roughening process copper foil. Chromium (VI) concentration in acidic chromic anhydride (VI) aqueous solution: 5 g/L pH value of acidic chromic anhydride (VI) aqueous solution: 3.2 Temperature of acidic chromic anhydride (VI) aqueous solution: 40°C Current density: 5 A /dm ² processing time: 4 seconds (Example 2)

A rustproof layer was formed on the S surface of the roughened copper foil in the same manner as in Example 1, except that the treatment shown in (4a) below was performed instead of the treatment shown in (4) above, and a surface-treated copper foil was obtained.

(4a) Alkaline chromate treatment was given to the S surface of the roughening process copper foil under the conditions shown below. Chromium (VI) concentration of alkaline chromic anhydride (VI) aqueous solution: 5 g/L pH value of alkaline chromic anhydride (VI) aqueous solution: 13.5 Zinc concentration of alkaline chromic anhydride (VI) aqueous solution: 3 g/L L Alkaline chromic anhydride (VI) aqueous solution temperature: 30°C Current density: 4 A/dm ² Treatment time: 5 seconds (Example 3)

Except that the treatment shown in (4a) above was further performed after the treatment shown in (4) above, an antirust layer was formed on the S surface of the roughened copper foil in the same manner as in Example 1 to obtain a surface-treated copper foil. . (Example 4)

A rustproof layer was formed on the S surface of the roughened copper foil in the same manner as in Example 3, except that the treatment shown in (2a) below was performed instead of the treatment shown in (2) above, and a surface-treated copper foil was obtained.

(2a) High-temperature oxidation treatment was performed on the S surface of the roughened copper foil under the conditions shown below. Temperature: 110°C Processing time: 5 seconds (Example 5)

Except having performed the process shown in the following (3a) instead of the process shown in said (3), it carried out similarly to Example 4, and formed the antirust layer on the S surface of the roughening process copper foil, and obtained the surface-treated copper foil.

(3a) Hydrogen generation process was given to the S surface of the roughening process copper foil under the conditions shown below. Sodium sulfate concentration in neutral saline solution: 1 mol/L Current density: 0.4 A/dm ² Processing time: 5 seconds

Comparative examples 1 to 3 are shown as typical examples of the usual antirust layer formed on the non-roughened surface of copper foil. (comparative example 1)

Except that the treatments shown in (2) and (3) above are not carried out, and only the treatments shown in (1) and (4) above are carried out, the S surface of the roughened copper foil is formed in the same way as in Example 1. Antirust layer, get surface treated copper foil. (comparative example 2)

Except that the treatments shown in (2) and (3) above are not carried out, and only the treatments shown in (1) and (4a) above are carried out, the S surface of the roughened copper foil is formed in the same way as in Example 2. Antirust layer, get surface treated copper foil. (comparative example 3)

Except that the treatment shown in the above (2) and (3) is not carried out, only the aspects of the treatment shown in the above (1), (4) and (4a) are carried out, in the same manner as in Example 3, the roughening treatment of copper The anti-rust layer is formed on the S surface of the foil, and the surface-treated copper foil is obtained. (comparative example 4)

Microetching treatment was performed on the S surface of the surface-treated copper foil of Comparative Example 3 as inner layer treatment. As the microetching solution, Etch Bond CZ-8000 manufactured by MEC Co., Ltd. was used.

The evaluation of the surface-treated copper foils of Examples 1 to 5 and Comparative Examples 1 to 4 produced in the above manner was performed. The evaluation items are the structure of the anti-rust layer, the adhesion of the inner layer and the transmission characteristics. Regarding the inner layer adhesiveness, three kinds of inner layer adhesiveness of normal state adhesiveness, heat-resistant adhesiveness and hydrochloric acid-resistant adhesiveness were evaluated. The evaluation method will be described below. (Evaluation method for the structure of the antirust layer)

The S surface of the surface-treated copper foil was analyzed by X-ray photoelectron spectroscopy (XPS) and hard X-ray photoelectron spectroscopy (HAXPES). The XPS measurement and HAXPES measurement were performed using PHI Quants, an X-ray photoelectron spectroscopy analyzer manufactured by ULVAC PHI. For incident X-rays, monochromatic Al-Kα rays (hν=1486.6 eV) were used in XPS measurement, and monochromatic Cr-Kα rays (hν=5414.9 eV) were used in HAXPES measurement. Both XPS and HAXPES measurements were carried out at a grazing angle of 45°.

The analysis software Multipak was used to perform background subtraction and peak separation on the Zn2p _3/2 spectrum and O1s spectrum obtained in XPS and HAXPES measurements. The Shirley method was used for background subtraction, and the pseudo-Voigt (pseudo-Voigt) function was used for peak separation. The binding energy of the peak top allows ±0.2 eV as an error range relative to the value recorded in this specification. For example, the peak of Zn(0) is 1021.8 eV, so the value in the range of 1021.6 eV to 1022.0 eV is actually used for peak separation.

The presence or absence and order of the three layers of the metal zinc layer, the zinc oxide layer and the zinc hydroxide layer were evaluated in accordance with the procedures (A) to (C) shown below.

(A) For the Zn2p _3/2 spectrum obtained by XPS measurement and HAXPES measurement, only the peak of Zn(0) (1021.8 eV) and the peak of Zn(II) (1022.5 eV) were separated, and the peaks were calculated Area rate. The unit of the area ratio is %, and only two peaks are separated to indicate that the area ratios of the two peaks add up to 100%. The measurement results of the copper foil of Example 1 are shown in (a) of FIG. 2 and (b) of FIG. 2 as an example.

In this case, when the condition (hereinafter, referred to as condition A) of "the area ratio of the Zn(0) peak in the HAXPES measurement is increased by 5% or more compared with the XPS measurement" can be evaluated from the surface layer side There is a layer structure of Zn(II)/metal Zn.

(B) For the O1s spectrum obtained by XPS measurement and HAXPES measurement, only the oxide peak (530.9 eV) and the hydroxide peak (532.4 eV) were separated, and the area ratio of each peak was calculated. The measurement results of Example 1 are shown in (c) and (d) of FIG. 2 as examples.

At this time, when the condition (hereinafter, referred to as condition B) is satisfied that the area ratio of the oxide peak in the HAXPES measurement is increased by 5% or more compared with the XPS measurement, it can be evaluated that hydrogen exists from the surface layer side. Oxide/oxide layer structure.

(C) By satisfying both of the above conditions A and B, it can be evaluated as a three-layer structure in which a metal zinc layer, a zinc oxide layer, and a zinc hydroxide layer exist in order from the copper foil side.

The results are shown in Table 1. In Table 1, the items about condition A and condition B are marked with ○ marks when the conditions are satisfied, and marked with X marks when the conditions are not satisfied. In addition, in Comparative Example 4, since the microetching was performed on the S surface, zinc and the like were not detected by XPS measurement. Therefore, in Table 1, it is represented as - mark with the meaning of no data.

（內層密接性之評價方法：常態密接性）Moreover, in this Example and a comparative example, the chromate layer existed in the outermost layer of the non-roughened surface of copper foil. It is well known that in the chromate layer, chromium oxides and chromium hydroxides are mixed. From this, it was confirmed that the increase in the area ratio of the chromium oxide peak in the HAXPES measurement was less than 5 percentage points compared with the XPS measurement, and it was confirmed that chromium does not have a layer structure and that a chromate layer exists on the outermost layer. Therefore, it can be seen that the presence of the chromate layer has no influence on the evaluation of the zinc hydroxide layer, zinc oxide layer and metal zinc layer using the method.

(Evaluation method of inner layer tightness: normal tightness)

As one of the evaluations of inner layer adhesion, a normal peeling test was performed based on JIS C6481:1996. On the non-roughened surface of the copper foil of the examples and comparative examples, that is, the S surface, two low-dielectric polyphenylene ether resin films (multilayer substrate material MEGTRON7 manufactured by Panasonic Co., Ltd., thickness 60 µm) to make a copper clad laminate. In addition, in Examples 1 to 5 and Comparative Examples 1 to 3, copper-clad laminates were produced without performing full-surface grinding and microetching treatment before attaching the resin film. In Comparative Example 4, a copper-clad laminate was produced after microetching.

The masking tape was removed after performing copper chloride etching on this copper-clad laminated board, and the circuit wiring board which has the circuit wiring of width 10 mm was produced. In a room temperature environment, use a Tensilon testing machine manufactured by Toyo Seiki Seisakusho Co., Ltd. to peel off the circuit wiring part (copper foil part) of the circuit board from the resin base material in a 90-degree direction at a speed of 50 mm/min. , The peel strength was measured as the normal peel strength. The results are shown in Table 1.

In Table 1, when the normal-state peel strength is 0.62 N/mm or more, it is judged that the normal-state adhesiveness is excellent, and it is indicated by a circle. mark indicates. (Evaluation method of inner layer adhesion: heat-resistant adhesion)

As one of the evaluations of inner layer adhesion, a heat-resistant peeling test was performed based on JIS C6481:1996. In the same way as in the normal peeling test, a circuit board was made, heated in a heated atmosphere oven at 300°C for 1 hour, and then naturally air-cooled to room temperature. Thereafter, a peeling test was performed in the same manner as in the case of the normal peeling test, and the peeling strength was measured as the heat-resistant peeling strength. The results are shown in Table 1.

In Table 1, when the heat-resistant peel strength is 0.55 N/mm or more, it is judged that the heat-resistant adhesiveness is excellent, and it is indicated by a circle. mark indicates. (Evaluation method of inner layer adhesion: hydrochloric acid resistance adhesion)

As one of the evaluations of inner layer adhesion, a hydrochloric acid peeling test was performed based on JIS C6481:1996. A circuit board was prepared in the same manner as in the normal peeling test, and immersed in hydrochloric acid with a liquid temperature of 25° C. and a concentration of 12% by mass for 30 minutes. After that, after careful water washing, a peeling test was performed in the same manner as in the normal state peeling test, and the peeling strength was measured as the hydrochloric acid-resistant peeling strength. The results are shown in Table 1.

In Table 1, when the hydrochloric acid peel strength is 0.55 N/mm or more, it is judged that the hydrochloric acid resistance is excellent, and it is indicated by a circle, and when the hydrochloric acid peel strength is less than 0.55 N/mm, it is judged as the hydrochloric acid resistance. Insufficient, indicated by × mark. (Evaluation method of transmission characteristics)

Using the copper foils of Examples and Comparative Examples and a low-dielectric polyphenylene ether-based resin film (Multilayer substrate material MEGTRON7 manufactured by Panasonic Co., Ltd., thickness 60 µm) as a resin base material, the cross-section shown in Fig. 3 was produced The structure is formed with a circuit board with a circuit, and the transmission characteristics are evaluated. The circuit width of the strip line formed on the circuit board was set to 140 µm, and the circuit length was set to 310 mm.

Specifically, the resin layers 30, 30 are arranged on both surfaces of the copper foil 22, and the copper foils 21, 23 are respectively laminated on the resin layers 30, 30 to produce a wiring board. Both the resin layers 30 and 30 are composed of two overlapping low-dielectric polyphenylene ether resin films. Moreover, both copper foils 21 and 23 are arrange|positioned so that the rough surface may face the resin layer 30 side.

For Comparative Example 4, first, the copper foil of Comparative Example 3 was used to form a circuit by copper chloride etching, followed by microetching treatment, and then the outer layer copper-clad laminate was bonded.

In addition, the microstrip line exposed on the side of the non-roughened surface may also be used for the evaluation of transmission characteristics, but the influence of the non-roughened surface side on the transmission characteristics cannot be accurately measured. Therefore, as the multilayer printed circuit of the present invention The evaluation of copper foil for boards is not suitable, and the evaluation of strip lines such as this example is suitable.

A high-frequency signal was transmitted to the circuit formed on the copper foil 22 of the wiring board using a network analyzer (network analyzer) N5291A manufactured by Keysight Technologies, and the transmission loss was measured. The copper foils 21 and 23 are grounded. The characteristic impedance is set to 50 Ω. The smaller the absolute value of the measured value of the transmission loss is, the less the transmission loss is, which means that the high-frequency signal can be transmitted well. The results are shown in Table 1.

In Table 1, when the absolute value of the measured transmission loss at 28 GHz is less than 11 dB/310 mm, it is judged that the transmission loss is small, indicated by a ○ mark, and it is more than 11 dB/310 mm and less than 15 dB/ When it is 310 mm, it is judged that the transmission loss is slightly large, and it is indicated by an × mark, and when it is 15 dB/310 mm or more, it is judged that the transmission loss is large, and it is indicated by a ×× mark.

It can be seen from Table 1 that the copper foils of Examples 1 to 5 satisfy conditions A and B, and are excellent in normal state adhesion, heat resistance adhesion, hydrochloric acid resistance adhesion, and transmission characteristics.

On the other hand, the copper foils of Comparative Examples 1 to 3 are copper foils having a previous anti-rust layer on the non-roughened surface, and it was confirmed that they did not satisfy the conditions A and B and were excellent in normal state adhesion, but heat-resistant adhesion, resistance Hydrochloric acid adhesion and transmission characteristics are poor. Since the copper foil of Comparative Example 4 was subjected to microetching treatment, it was confirmed that the normal-state adhesiveness, heat-resistant adhesiveness, and hydrochloric acid-resistant adhesiveness were excellent, but the transmission characteristics were significantly inferior.

1: copper foil body 1a: Rough surface 1b: Non-roughened surface 10: Anti-rust layer 11: metal zinc layer 12: Zinc oxide layer 13: Zinc hydroxide layer 14: Chromate layer 21: copper foil 22: copper foil 23: copper foil 30: resin layer

Fig. 1 is a cross-sectional view showing the structure of a surface-treated copper foil according to an embodiment of the present invention. Fig. 2 is a graph showing the results of XPS analysis and HAXPES analysis of the antirust layer of the copper foil of Example 1. Fig. 3 is a cross-sectional view showing the structure of a circuit board for evaluation of transmission characteristics.

Domestic deposit information (please note in order of depositor, date, and number) none Overseas storage information (please note in order of storage country, institution, date, and number) none

1: copper foil body

1a: Rough surface

1b: Non-roughened surface

10: Anti-rust layer

11: metal zinc layer

12: Zinc oxide layer

13: Zinc hydroxide layer

14: Chromate layer

Claims (6)

A surface-treated copper foil comprising: a copper foil main body, one of two main surfaces of which is a roughened surface formed by roughening treatment, and the other is a non-roughened surface; and an antirust layer formed on The aforementioned non-roughened surface of the aforementioned copper foil main body; and the aforementioned antirust layer has a metallic zinc layer consisting of metallic zinc, a zinc oxide layer consisting of zinc oxide, and a zinc hydroxide layer consisting of zinc hydroxide And a chromate layer composed of a chromium compound, the layers of the aforementioned antirust layer are arranged according to the aforementioned metal zinc layer, the aforementioned zinc oxide layer, the aforementioned zinc hydroxide layer, and the aforementioned chromic acid layer from the side of the aforementioned copper foil main body. Sequential layering of salt layers. The surface-treated copper foil according to claim 1, wherein the main body of the copper foil is electrolytic copper foil. The surface-treated copper foil according to claim 1 or 2, wherein the ten-point average roughness Rzjis of the non-roughened surface is 1.5 μm or less. The surface-treated copper foil according to claim 1 or 2, wherein the average height of the roughened particles on the roughened surface is in the range of 0.2 μm to 0.8 μm. A copper-clad laminate comprising: the surface-treated copper foil according to any one of claims 1 to 4, and a resin base material laminated on the roughened surface side of the surface-treated copper foil. A printed circuit board comprising the copper-clad laminate as described in Claim 5.

Images