KR100818587B1 - Fabrication method of ultra thin thickness metal strips - Google Patents

Abstract

A fabrication method of ultra-thin metal strips is provided to inexpensively fabricate flexible laminate films for fine pitch having high quality through a casting process by fabricating ultra-thin strips with a thickness of 10 mum or less, thereby replacing conventional electrolytic copper foils. A fabrication method of a ultra-thin metal strip comprises: a workpiece preparing step of repeatedly performing rolling and annealing on a metal sheet to manufacture a metal strip(S1); an oxidizing step of adhering a masking tape to the edge of the metal strip and spraying an NaOH solution onto a central part of the metal strip, thereby selectively oxidizing only the central part except the edge on one face of the metal strip to form a metal oxide layer(S2); a rolling step of overlapping two metal strips passing through the oxidizing step in a way that metal oxide layer-formed faces of the metal strips are brought into contact with each other and adhering the metal strips to form a metal strip laminate and reduce the thickness of the metal strip laminate(S3); a slitting step of cutting and removing the edge of the metal strip laminate passing through the rolling step(S4); and a separating step of separating two single metal strips from each other, the two single metal strips forming the metal strip laminate passing through the slitting step(S5).

Description

FABRICATION METHOD OF ULTRA THIN THICKNESS METAL STRIPS

The present invention relates to a method for producing a metal ultra-thin plate, and more particularly, to produce a copper or stainless steel ultra-thin plate (Ultra Thin Thickness Strip) used in the production of a flexible copper foil laminated film or a flexible stainless steel laminated film for fine pitch. It is about a method.

Flexible laminated film is the main core material of flexible printed circuit board mainly used in mobile phones and LCDs, etc., and it is possible to manufacture a flexible circuit board by forming a circuit using etching techniques thereon. For example, FIG. 1 shows a flexible copper foil laminated film (top) and a flexible circuit board (bottom) photograph manufactured using the same.

Unlike flexible copper clad laminates used for general PCBs, such flexible laminated films are thin and flexible, and their use is increasing mainly in digital devices with a trend toward small size and light weight. In accordance with the trend of miniaturization of digital devices, integration of electronic components is required. In order to integrate components, the line width of a circuit must be designed to be 40 μm or less, and in order to meet the line width of 40 μm or less, copper foil or stainless steel of flexible laminated film is required. The foil thickness should be less than 10㎛. In other words, the fine pitch (fine pitch) means that the distance between the centers of adjacent conductor circuits is very short. In the case of small electronic products such as mobile phones or digital cameras, when multiple components are to be mounted on small boards, the spacing between the components This means that very little) of the flexible laminated film is required.

The flexible laminated film is manufactured by attaching a metal thin plate such as copper or stainless steel to a polyimide (PI) film, which is a raw material, and the method of manufacturing the flexible laminated film is largely casted and metalized. Process, and laminating method. Hereinafter, the manufacturing method will be briefly described based on the flexible copper foil laminated film.

The casting method is a method of manufacturing a flexible laminated film by coating a liquid polyimide solution on a copper foil and curing it at about 300 ° C., which has excellent adhesive strength, excellent thickness precision, and a cost of raw materials by using a liquid polyimide solution. Its low cost and simple process make it the best process with low manufacturing cost. Since only 12 micrometers or more of copper foils are currently supplied in the industry, it is used for the circuit whose pitch is 50 micrometers-100 micrometers, and the thickness of copper foil is about 12 micrometers-18 micrometers.

The metallization method deposits Ni-Cr particles in a polyimide film on a film by sputtering in a vacuum state, and then undergoes Cu strike plating, and then copper plated to facilitate a copper foil thickness of 10 μm or less. Although it has been applied to the production of flexible copper clad laminated films for fine pitch requiring copper thickness of 10 μm or less, the manufacturing process is complicated and the manufacturing cost is high, and current loss occurs because Ni-Cr particles remain during etching of the circuit. It tends to be brittle as an electrolytic copper foil, and quality fall is a problem. The thickness of copper foil currently supplied mainly is 8 micrometers.

The laminating method is a method of rolling-bonding a polyimide film and a copper foil, and can achieve high productivity, but there are disadvantages in that raw materials are more expensive than the casting method due to the use of a polyimide film.

Therefore, the casting method is the most efficient at the time of manufacturing the flexible laminated film, but the current situation is not made of copper foil of 10㎛ or less.

On the other hand, a conventional metal ultrathin plate manufacturing method includes a clad method, a multilayer rolling method, an aluminum foil rolling method and the like. Hereinafter, the conventional method of manufacturing the ultrathin metal plate will be briefly described.

The clad method is a method of clad rolling other metals and copper to separate copper from other metals after rolling to a certain thickness, and thermal and etching methods are widely used as separation methods. However, such a clad method is theoretically feasible but practically difficult, and even if it is practically used, there is a disadvantage in that productivity is low and manufacturing cost is high.

Multi-layer rolling is a method of inserting and rolling a copper piece between high-strength metal pieces, the production is possible, but there is a disadvantage in productivity and low production cost.

The aluminum foil rolling method is a method of coating oil on one side of a strip to serve as a release agent in the future lamination rolling, laminating the oil-coated two sides face-to-face, rolling and separating to a predetermined thickness after doubling. In the case of manufacturing the ultra-thin plate or application to the production of copper or stainless foil, copper or stainless, unlike aluminum, is severely slipped in some parts of the oil layer, and in other parts, the oil film is broken and fused. Strips are entangled and have not been put to practical use.

Therefore, the present invention was devised to solve the problems of the conventional metal ultra thin plate manufacturing method as described above, by replacing the conventional electrolytic copper foil by manufacturing an ultra-thin plate of 10㎛ or less thickness that was not possible due to the conventional rolling limit An object of the present invention is to provide a method of manufacturing a high quality fine pitch flexible laminated film at low cost by a casting method.

The objects and advantages of the present invention will be described in more detail below, and will be further embodied by the examples. Further objects and advantages of the invention may be realized by the means indicated in the claims and combinations thereof.

Metal ultra-thin plate manufacturing method according to the present invention for achieving the object as described above, the material preparation step of producing a metal strip by repeatedly rolling and annealing the metal sheet; An oxidation step of selectively oxidizing only a central portion of the surface of the metal strip except for an edge to form a metal oxide layer; Rolling the two metal strips subjected to the oxidation step so that the surfaces on which the metal oxide layer is formed are brought into contact with each other and then bonding them to form a metal strip laminate, and to reduce the thickness of the metal strip laminate; A slitting step of cutting off and removing the adhered portion of the edge of the metal strip laminate after the rolling step; And a separation step of separating two single metal strips constituting the metal strip laminate subjected to the slitting step from each other, wherein the metal is copper or stainless steel.

Here, the oxidation step is carried out by attaching a masking tape to the edge of the metal strip and spraying a NaOH solution in the central portion of the metal strip, the NaOH solution sprayed in the oxidation step is an aqueous solution of 25% concentration, 70 It is characterized in that it is maintained at a temperature of ℃ to 80 ℃.

In addition, the rolling step includes the step of laminating and rolling together to produce an integrated metal strip laminate as the two metal strips are bonded to each other, and simultaneously to reduce the thickness of the metal strip laminate and to make it thin; It characterized in that it comprises a cold rolling step using a multi-stage rolling machine to reduce the thickness of the laminated rolled metal strip laminate again to ultra-thin plate.

In the slitting step, the metal strip laminate is transferred while being unwound in a rolled form, and only the edge portions (bonded portions) of the metal strip laminate, in which the metal oxide layer is not formed, are moved up and down. Characterized in that it is carried out by cutting and removing by a pair of rotating cutters.

On the other hand, the separating step is characterized in that it is carried out by the continuous bending up and down by passing the metal strip laminate cut off the edge portion to the separation roll unit is arranged in two stages in a plurality of rollers in a zigzag up and down.

According to the manufacturing method of the ultra-thin metal plate according to the present invention as described above, by forming a metal oxide layer on the metal strip to prevent the slip phenomenon during the lamination and rolling of two metal strips to be uniformly rolled in a state where both strips are laminated And, the metal oxide layer also acts as a release material when the separation is easy to separate, it is possible to easily manufacture the ultra-thin plate of 10 ㎛ thickness or less that was not possible due to the conventional rolling limits, the metal thus produced The ultra-thin plate has an excellent advantage of manufacturing a high quality fine pitch flexible laminated film at low cost by casting method by replacing the conventional electrolytic copper foil.

Hereinafter, a method of manufacturing a metal ultrathin plate according to the present invention will be described in detail with reference to the accompanying drawings. Here, the metal is made of copper or stainless steel, and the ultra-thin plate manufactured according to this is copper foil or stainless foil. Hereinafter, the manufacturing method which concerns on this invention based on copper foil manufacture is demonstrated in detail. In the case of stainless steel foil, only the type of metal used is different, and the whole process is applied in the same way.

2 is a process flowchart sequentially showing the process steps of the method of manufacturing a metal ultrathin plate according to the present invention. As shown, the method of manufacturing a metal ultrathin plate according to the present invention includes a material preparation step (S1), an oxidation step (S2), a rolling step (S3), a slitting step (S4) and a separation step (S5). do.

The material preparation step (S1) is a step of preparing a metal strip (1), in particular a copper strip or a stainless steel strip, which is a raw material for manufacturing the ultrathin metal plate according to the present invention. This metal strip 1 is produced by a conventional strip production method. That is, rolling and annealing are repeatedly performed on the copper plate or the stainless steel plate to produce a copper strip or a stainless steel strip.

FIG. 3 shows the appearance of the metal strip 1 produced by such repeated work of rolling and annealing and its preferred specification. As shown, the metal strip 1 is configured in the form of a thin foil having a constant thickness T and width W, and is wound and prepared as shown in the left part of FIG. 3. 3 is a cross sectional view of the metal strip 1. It is preferable that the thickness of the metal strip 1 be manufactured so that the thickness of the completed ultra-thin plate may be 10 μm or less, in consideration of being thinned through the rolling processes described later. In particular, in the present invention, FIG. As shown in, it is preferably manufactured to a thickness of 25 μm.

When the material preparation is completed in the above manner, the oxidation step (S2) is performed. The oxidation step is a step of oxidizing one surface of the prepared metal strip 1 to form the metal oxide layer 4. The metal oxide layer 4 is rolled to face the two metal strips (1) during the lamination rolling to be described later serves as a release material to facilitate the separation of each strip after rolling and to prevent slip between the two strips. .

It is preferable that the metal oxide layer 4 is selectively formed only at the center portion excluding the edge portion of the metal strip 1. More specifically, except for a section of about 10 mm from both ends of the width direction in one surface of the metal strip 1, all of the central portion thereof is preferably oxidized. The reason why the metal oxide layer 4 is not formed at the edges of the metal strip 1 is that the two strips do not slide together as the adhesive parts are pressed while the copper parts of the two strips are laminated to each other during lamination rolling, which will be described later. It is to be able to roll uniformly without.

In order to form the metal oxide layer 4 as described above, in the present invention, a basic solution is sprayed onto the surface of the metal strip 1. The basic solution used herein is preferably a 25% NaOH aqueous solution, and in order to prevent oxidation of the edge portion of the metal strip 1, the masking tape 3 is disposed at a length of about 10 mm from both ends in the width direction of the metal strip 1. So that the edge surface of the metal strip 1 does not come into contact with the basic solution.

When NaOH solution is sprayed on the above metal strip 1, for example, copper strip, Cu and hydroxyl groups (OH groups) react to form basic copper hydroxide, and when heat is supplied thereto, black as water and metal oxide Copper oxide is formed. For this heat supply, the temperature of the NaOH solution is preferably maintained at 70 to 80 ℃. This reaction can be expressed by the formula (1).

^{Cu 2 + + 2OH - → Cu} (OH) type _{2 → H 2 O + CuO (} 1)

4 schematically shows a process performed in this oxidation step and a change process of the metal strip 1 according to the process.

As shown in the drawing, the metal strip 1 is wound in the form of a roll and then unwinded in accordance with the rotation of the uncoiler 10 and is conveyed forward by the feed roller 12. As shown in the lower part of the figure, the thickness of the metal strip 1 in the state wound and conveyed by the first uncoiler 10 is set to 25 micrometers. The front side of the uncoiler 10 is provided with a masking tape unwinder 20, and the masking tape 3 wound thereon is unwound and also conveyed to the front side.

The metal strip 1 unwound from the uncoiler 10 and the masking tape 3 unwound from the masking tape unwinder 20 are laminated while overlapping each other in the lamination roller 30. As shown at the bottom of the figure, the masking tape 3 is attached only to 10 mm portions of both edges of the metal strip 1.

As such, the metal strip 1 to which the masking tape 3 is attached proceeds to be in close contact with the urethane roll 40 in the oxidation chamber, and 25% NaOH solution is injected therein. As the NaOH solution is injected, copper and hydroxyl groups react at the central portion of the metal strip 1 to which the masking tape 3 is not bonded to form a black copper oxide layer.

When the NaOH injection is completed, the masking tape 3 is recovered to the masking tape rewinder 50, and the metal strip 1 is recovered to the recoiler 60. At the bottom of the figure, a cross-sectional view of the copper oxide layer is formed on the surface of the metal strip 1 by such a process. As shown, the metal strip 1 has a total thickness of 25 μm, and the metal oxide layer 4, specifically copper oxide, has a depth of about 1 μm only at the center portion where the masking tape 3 is not adhered. It can be seen that a layer is formed.

5 is a photograph of the metal strip (1) oxidized through this process. It can be seen from the photograph that the black copper oxide layer is formed on one surface of the metal strip 1. 6 shows a photograph of the copper oxide layer observed with an electron microscope. It was confirmed from the photograph that an oxide layer was formed on the surface of the metal strip 1.

The metal strip 1 which has undergone the oxidation step as described above enters the rolling step S3. The rolling step is a step for forming a metal strip laminate by folding two metal strips 1 which have undergone oxidation step such that the metal oxide layer 4 is opposed to each other, and reducing the thickness of the metal strip laminate. The rolling step in the present invention is carried out in two steps, lamination rolling and cold rolling.

The lamination rolling is adhesive rolling of two or more metal sheets together, and FIG. 7 schematically illustrates a process performed in the lamination rolling step according to the present invention and a process of changing the metal strip according to the process.

As shown in the drawing, through the oxidation step, the two metal strips 1 on which the metal oxide layer 4 is formed are prepared, and both metal strips 1 are prepared using a conventional four high mill rolling mill. The surfaces on which the metal oxide layer 4 is formed are laminated so as to face each other and then adhesively rolled. As a result of the lamination rolling, both strips are bonded to and integrated with each other at the edges except for the central portion where the metal oxide is formed, thereby forming a metal strip laminate and simultaneously reducing the thickness of the metal strip laminate and making it thin. It is preferable that the reduction ratio at the time of the lamination rolling is about 30%. Accordingly, the thickness of the two integrated metal strips 1 becomes thinner from the first 50 µm to 35 µm. In this case, it can be seen that the thickness of the single metal strip 1 is 17 μm.

In the metal strip laminate formed through the lamination rolling of the two metal strips 1, cold rolling is performed in order to reduce the thickness and make the ultra thin plate again. 8 schematically shows a process performed in the cold rolling step according to the present invention and a process of changing the metal strip according to the process.

As shown, in the cold rolling step, the metal strip laminate is cold rolled using a conventional multi-stage rolling mill (20 stages). Rolling is carried out in two passes (rolling) to 17㎛. In one pass, the thickness of the metal strip laminate becomes thin from 35 μm to 24 μm, and in two passes, the thickness of the metal strip laminate becomes 17 μm. Accordingly, it can be seen that the thickness of the single metal strip 1 is 8 μm.

The metal strip laminate, which has undergone the rolling step as described above, is subjected to a slitting step S4 and a separation step S5 in this order. Slitting is the process of cutting and removing the bonded edges of the metal strip laminate, that is, the edges that are not oxidized (bonded), and the separation is the two single pieces that make up the slitting laminate. This is a process of removing the metal strips 1 from each other. 9 schematically illustrates a process performed in the slitting and separating step according to the present invention, and a process of changing the metal strip according to the process.

As shown in FIG. 9, the metal strip laminate is rolled and unwound using an uncoiler 70 in a rolled state, and the edge of the metal strip laminate is formed by a pair of upper and lower rotating cutters 80. Cut the part (not oxidized part). The metal strip stack is then passed up and down by passing the metal strip stack through a two-stage separation roll unit 90 in which a plurality of rollers are arranged in a zigzag manner, and separated into two single strips and two separate noses. The irrigation 100 is used to recover each single strip. At this time, the metal oxide layer 4 acts as a release material so that the single strips can be easily separated from each other. Subsequently, when the metal oxide film formed on one surface of the single strips is removed, metal ultrathin plates having a thickness of 8 μm are formed as shown.

By using a metal ultra-thin plate of less than 10㎛ formed in this way it is possible to cheaply produce a high-quality fine pitch flexible laminated film by the casting method.

So far, the present invention has been described in detail with reference to embodiments of the present invention. However, the scope of the present invention is not limited thereto, and the present invention is intended to include practically equivalent ranges.

1 is a photo showing a conventional conventional flexible laminated film and a flexible circuit board using the same;

2 is a process flow chart sequentially showing the process steps of the method for producing a metal ultrathin plate according to the present invention;

Figure 3 is a view showing the shape and size of the metal strip prepared in the material preparation step of the method for producing a metal ultrathin plate according to the present invention,

4 is a view schematically showing a process performed in the oxidation step of the metal ultrathin plate manufacturing method according to the present invention and a process of changing the metal strip according to the process performed;

5 is a photograph showing a result of forming a metal oxide layer on one surface of a strip according to the oxidation step of the method of manufacturing a metal ultrathin plate according to the present invention;

6 is an electron micrograph of a metal oxide layer formed on one surface of a strip,

7 is a view schematically showing a process performed in the lamination rolling step of the method for manufacturing a metal ultrathin plate according to the present invention and a process of changing the metal strip according to the process;

8 is a view schematically showing a process performed in the cold rolling step of the method for manufacturing a metal ultra-thin plate according to the present invention and a process of changing the metal strip according to the process;

9 is a view schematically showing a process performed in the slitting and separation step of the method for manufacturing a metal ultrathin plate according to the present invention, and a process of changing the metal strip according to the process.

Claims (7)

A material preparation step of repeatedly rolling and annealing the metal sheet to produce the metal strip 1; By attaching a masking tape 3 to the edge of the metal strip 1 and spraying a NaOH solution to the center of the metal strip 1, only the central part of the surface of the metal strip 1 except for the edge is selectively oxidized. An oxidation step of forming a metal oxide layer 4; The two metal strips 1 which have undergone the oxidation step are folded to face each other on which the metal oxide layer 4 is formed and then bonded to each other to form a metal strip laminate, and to reduce the thickness of the metal strip laminate. Rolling step for; A slitting step of cutting and removing an edge of the metal strip laminate which has been subjected to the rolling step; And a separation step of separating two single metal strips (1) constituting the metal strip laminate having the slitting step from each other. The method of claim 1, The metal is a thin metal plate manufacturing method, characterized in that the copper or stainless steel. delete The method according to claim 1 or 2, The NaOH solution sprayed in the oxidation step is a 25% aqueous solution, characterized in that the ultra-thin metal plate manufacturing method characterized in that maintained at a temperature of 70 ℃ to 80 ℃. The method according to claim 1 or 2, The rolling step may include a lamination rolling step of manufacturing an integrated metal strip laminate as the two metal strips 1 are bonded to each other and at the same time adhesive rolling to reduce the thickness of the metal strip laminate and to reduce the thickness thereof. ; And a cold rolling step using a multi-stage rolling machine to reduce the thickness of the laminated rolled metal strip laminate to ultra-thin plate. The method according to claim 1 or 2, In the slitting step, the metal strip laminate is transported while being unwound in the form of a roll, and a pair of upper and lower rotary cutters are formed on only edge portions of the metal strip laminate in which the metal oxide layer 4 is not formed. 80) A method for producing a metal thin plate, characterized in that it is carried out by cutting and removing. The method according to claim 1 or 2, The separating step is carried out by continuously bending up and down by passing the metal strip laminate, the edge portion of which is cut off, through the separation roll unit 90 in which a plurality of rollers are arranged in two stages in a vertical zigzag manner. Method of manufacturing metal ultrathin plates.

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