KR940003237B1 - Copper foil for printed circuit board - Google Patents

Abstract

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Description

Copper foil for printed wiring board

1 is a cross-sectional view showing the copper foil for a printed wiring board of the present invention.

* Explanation of symbols for main parts of the drawings

1: 1st copper layer 2: corrosion resistant layer

2: 2nd copper layer

The present invention relates to a copper foil used for a printed wiring board, a printed wiring board substrate using the copper foil, and a manufacturing method thereof.

BACKGROUND With the development of electronic devices and devices, printed wiring boards having a stronger wiring density have been required, and there is an important technical problem of current time in manufacturing finer wiring.

There are a variety of methods for manufacturing printed wiring boards. And generally known methods; A subtractive method of forming a copper foil on an insulating resin to obtain a copper clad thin layer, and then etching the copper foil in a non-circuit region to prepare a circuit-type copper foil; An additional method of forming a covering copper of an intended circuit form on the insulating resin plate by forming a non-electrode plating method and a circuit; In part, for example, in the through-hole, there is a partial fold method of forming a conductor by non-electrodeposition plating or the like.

Among these methods, subtractive methods have been used for many years. In this method, the thickness of the copper foil of the coating lamination provided with the strengthening of wiring density is achieved until now. This is for the following reason. That is, an etching circuit of the required circuit form according to this method is formed on the surface, and copper foil in an unnecessary area not covered by the corrosion inhibitor is dissolved using a cupric chloride or a ferric chloride under corrosion solution. Let's do it. If the thickness of the copper foil is too large, the side of the required circuit area also comes into contact with the corrosion solution at this time, so-called side corrosion occurs. And, if the copper foil is too thick, the required circuit area is also dissolved copper, it is not possible to calculate the circuit of a fine form. In addition, in the case of the wiring board which should have a through hole, after forming a copper layer by electroplating in order to stabilize the thickness of the conductor in a through hole, the copper coating layer is made of thickness, and a copper foil is formed by a non-electrode plating method. A thin copper layer is formed in the hole containing the surface. As a result, the thickness of the copper foil becomes thicker than in the initial state.

For this reason, the copper foil of a copper clad laminated board should have a small thickness, and until now, many copper clad thin boards provided by laminating | stacking copper foil of various thickness have been proposed and developed. The copper foil used for this purpose is a rolled copper foil produced by thinning a copper mass by the action of heating and pressure, and an electrolytic copper foil produced by coating copper on a metal such as stainless steel by an electroplating method. It is classified and usually produces copper foil whose thickness is 180 micrometers-70 micrometers.

Recently, it has also been possible to produce a thin copper foil having a thickness of 5 mu m by electroplating on aluminum foil.

Currently, the reason why the conventional rolled copper foil is not used as a thin copper foil is because of the following problems. In other words, the copper foil itself is difficult to handle in a thin state, low yield, and too expensive. Moreover, even though the mechanical strength can be maintained because aluminum foil or the like supported by the electrolytic copper foil is used, there is a problem that the adhesive strength to the insulating resin is lower than that of the usual thick copper foil. The reason is that even though the surface of the conventional copper foil to the wiring board is roughened for the purpose of enhancing the adhesiveness to the resin, it is difficult to rough the thin instrument copper foil.

SUMMARY OF THE INVENTION An object of the present invention is to provide a copper foil for printed wiring boards, and a substrate for printed wiring boards using the copper foil, which is easy to process even at a small thickness and has excellent adhesion to resin.

The present invention provides a copper foil for a printed wiring board comprising a first copper layer (1), a corrosion resistant layer (2) formed of a metal having higher resistance to a solution that corrodes copper, and a second copper layer (3). The corrosion resistant layer 2 is present between the first copper layer 1 and the second copper layer 3 and the surface of the second copper layer 3 is rough.

This invention also provides the board | substrate for printed wiring boards and the insulating base which consist of the said copper foil for printed wiring boards.

This invention also provides the method of producing the board | substrate for printed wiring boards using the said copper foil for printed wiring boards.

The invention will be more apparent from the accompanying drawings.

In the figure, the copper foil for printed wiring boards of this invention consists of the 1st copper layer 1 and the corrosion-resistant layer 2 formed of the metal which has high resistance with respect to the solution which corrodes copper, and the 3rd copper layer 3 The corrosion resistant layer is present between the first copper layer 1 and the second copper layer 3, and the surface of the second copper layer 3 is roughened.

The first copper layer 1 of the present invention may be formed by a rolled copper foil method, an electrolytic copper foil method, or other method such as vapor deposition, non-electrode plating, or the like. It is preferable that the thickness of this 1st copper foil 1 is 15 micrometers or more so that handling may be easy. Moreover, it is preferable that one side of a copper layer has a rough surface of at least about 1-10 micrometers. In order to form a rough surface, a conventional rough copper foil method such as contact with a corrosion solution and electroplating under optional conditions may be suitable.

Next, regarding the corrosion resistant layer 2, the layer which has low solubility is selected in the solution which corrodes copper, and is formed in the rough surface of the 1st copper layer 1. As shown in FIG. As an example of a conventional corrosion resistant layer, a nickel layer, a tin layer, etc. can be mentioned. The layer may be formed of one kind of metal or an alloy of two or more kinds of metals. Although the overall thickness of the corrosion resistant layer 2 can be made thinner, it can be made into two or more, without restricting to one layer. Until the conditions of these methods are adjusted to form a rough surface, the corrosion resistant layer 2 may be formed by a method such as electroplating, non-electrode plating, substitution plating, or intermediate deposition.

The 2nd copper layer 3 is formed in the surface of the said corrosion-resistant layer 2, and thickness of this layer can be reduced as needed. As a method of forming this copper layer 3, the method as mentioned in the paragraph of the corrosion resistant layer 2 can be diverted.

If necessary, a waterproof film may be selectively formed on the surface of the second copper layer 3 in order to maintain high stability in long term storage.

The copper foil obtained by the said method can be used as a board | substrate for printed wiring boards by joining the rough surface of a 2nd copper layer with an insulating base material. Insulating materials that can be used for this purpose include organic insulating materials such as phenolic resins, epoxy resins, polyester resins, polyimide resins, polyethylene resins, polytetrafluoroethylene resins, and the like, and inorganic insulating materials such as ceramics and the like. . In addition, the organic insulating material may be used in the form of FRP in combination with glass fiber, glass chop, non-woven fiber and the like. The resin in the unprocessed state can be supplied to the rough surface of the second copper layer 3 of copper foil, and the whole can be laminated with heat and pressure to bond these bonded materials to the organic insulating material. In the case of an organic insulating material, the material can be bonded to the surface of the second copper layer 3 of copper foil by a flame spray coating method. Of course, the other well-known technique of bonding an insulating material to copper foil can be used in addition to the above.

In another embodiment of the present invention, by joining the rough surface of the first copper layer and the second copper layer 3 as an insulating substrate and corroding the copper layer from a region where the copper layer is not in contact with the insulating material. The copper foil of this invention can be used as a board | substrate for printed wiring boards by using the corrosion liquid which can corrode copper. In addition, by removing a corrosion resistant layer using a solution which easily corrodes the corrosion resistant layer without corroding copper, the rest can be used as a substrate for a printed wiring board. By the following technique, a substrate for a printed wiring board having a high adhesiveness and a thin gauge copper foil can be obtained, and a highly accurate wiring board can be produced by distributed circuit processing.

Example 1

On the stainless steel plate, the copper foil which has a copper sulfite thickness of 30 micrometers was formed. The surface of the copper foil thus formed has roughness of about 7 μm.

Next, the electrolytic nickel plating layer having a thickness of about 0.5 μm was formed on the surface of the copper foil using watt conductance.

Then, an electrolytic copper plating film having a thickness of about 2 μm was formed on the surface of the nickel film by the same method as used in the electroplating.

In addition, a zinc-chromium resist was formed on the surface of the copper film by electrolytic treatment.

Then, the glass fiber epoxy resin penetrating steel was laminated on the corrosion-resistant surface of the copper film thus obtained.

Thus, the first copper layer of the obtained thin plate was corroded with alkaline corrosion solution until the nickel layer was exposed.

Then, the thin layer thus prepared forms a plating insulating material on the surface and coats the copper layer having a thickness of 30 占 퐉 in an area not covered by the insulating paint. After the plating insulation was peeled off, the thin nickel layer and the thin copper layer were corroded with copper chloride / chloride solution by obtaining a test sample having a circuit pattern having a width of 10 mm and a length of 100 mm. The peel strength of the test sample was about 1.8 kgf / cm on average. On the other hand, when a plated copper layer having a thickness of 300 µm is applied to a conventional copper foil having a thickness of 5 µm by an electroplating method, and the thus obtained copper foil is laminated with a glass fiber epoxy resin, the thin layer is 1.5 kgf / It has an average peel strength of cm. And it was confirmed that the sample of the present invention is higher when produced using conventional copper foil in adhesive strength.

In the accuracy of the wiring pattern, the present invention was able to obtain a product having a conductor width and a distance between the conductors and the conductors of 70 µm. On the other hand, in the conventional products, the width of the conductor and the gap between the conductor and the conductor could not be formed below 100 m. This means that the product of the present invention is superior to the conventional product in the precision of wiring processing.

As described above, since a copper foil having a three-layer structure is used, the present invention provides a copper foil for a printed wiring board excellent in not only bonding strength but also in the accuracy of wiring processing, a substrate for a printed wiring board using the copper foil, and the production thereof. Provide a method.

Claims (8)

It is composed of a first copper layer and a corrosion resistant layer and a second copper layer formed of a metal having higher resistance to a solution that corrodes copper, wherein the corrosion resistant layer is present between the first copper layer and the second copper layer. And the copper foil for printed wiring boards in which the surface of the said 2nd copper layer was roughened. The copper foil for printed wiring boards of Claim 1 which has an antirust film on the surface of a 2nd copper layer. The board | substrate for printed wiring boards containing the copper foil of Claim 1, and the rough surface of the 2nd copper layer in the copper foil of Claim 1 bonded to the insulating base material. The method for manufacturing a printed wiring board as set forth in claim 1, wherein the rough surface of the second copper layer in the copper foil is bonded to an insulating substrate, and the copper layer is corroded with a corrosion solution that corrodes copper in a region not in contact with the insulating substrate. The coarse surface of the second copper layer of copper foil is bonded to the insulating substrate, and the copper layer is corroded with a corrosion solution that corrodes copper in a region not in contact with the insulating substrate, after which the corrosion resistant layer is easily corroded and the copper The method for producing a substrate for a printed wiring board according to claim 3, wherein the copper layer is removed with a liquid which does not corrode and a copper layer contacted with an insulating substrate is used as the copper foil for the circuit. The board | substrate for printed wiring boards comprised from the rough surface of the copper foil of Claim 2, and the 2nd copper layer of the copper foil bonded to the insulating base material. A method of manufacturing a substrate for a printed wiring board, wherein the rough surface of the second copper layer of copper foil is bonded to an insulating substrate, and the copper layer is corroded with a corrosion solution that corrodes copper in a region not in contact with the insulating substrate. The rough surface of the second copper layer of copper foil is bonded to an insulating substrate, and the copper layer is corroded with a corrosion solution that corrodes copper in a region not in contact with the insulating substrate, after which the corrosion resistant layer is easily corroded and copper The method of manufacturing a substrate for a printed wiring board according to claim 6, wherein the corrosion resistant layer is removed with a liquid which does not corrode.