KR20110061825A - Laminated structure for a flexible circuit board being improved a crack development elasticity and manufacturing method the same - Google Patents

Abstract

PURPOSE: A method for manufacturing a structure on flexible circuit boards are laminated capable of reducing cracks on a copper pattern is provided to minimize a repulsive force against external stress. CONSTITUTION: A tie layer(2) is deposited on a polymer film(1) whose surface is processed by a sputtering method. A seed layer(3) is deposited on the tie layer by copper. The amount of applied currents increases in a copper electrolysis plating solution so that an electrolytic plated layer(4) is formed.

Description

Laminated structure for a flexible circuit board being improved a crack development elasticity and manufacturing method the same}

The present invention relates to a method for manufacturing a flexible printed circuit board laminate structure having improved copper pattern crack generation, and a laminate structure manufactured by the method, and more particularly, a base film layer, a tie layer, a seed layer and Fabrication of a flexible printed circuit board laminated structure in which a flexible circuit board laminate structure composed of an electroplating layer is fundamentally blocked or suppressed to the maximum the crack generation of a copper pattern, which is a major cause of a wiring short circuit of the circuit board, thereby improving crack generation. A method and a laminated structure produced by the method.

In recent years, due to the development of technology, especially in the field of electronics industry, the trend of miniaturization, thinning, high density, and high bending of electronic products is accelerating. The use of printed circuit boards (PCBs), which are easy to use in space, is on the rise. In the case of printed circuit boards, the use of COF (Chip On Film) films, especially for LCD TVs, is increasing. . The COF film is used to serve to transfer electrical signals between the LCD panel and the PCB substrate.

The method of manufacturing a COF film that plays such a role is a flex resistance using a physical vapor deposition (PVD) after surface treatment in order to improve the adhesion with the substrate using a polyimide film having excellent heat resistance and acid resistance as a substrate. In order to improve heat resistance, anti-migration, and the like, a Ni-Cr layer is deposited and a conductive layer of copper is deposited. The conductor on which the metal is deposited is electrodeposited using the electroplating method.

However, recently, in the case of the COF product, a fine pattern for high integration has been applied to be used in LCD TV products requiring high quality and large screen characteristics. As the width decreases, the overall copper area of the pattern decreases. The reduced copper pattern increases heat generation due to resistance in terms of electrical and causes short circuits due to external influences generated in each process, that is, etching process, SR coating process, bonding process, and vibration caused by conveying. There is a problem that the probability of occurrence of possible copper pattern cracks is significantly increased.

By the way, the conventional technology related to the flexible printed circuit board is mainly to improve the dimensional stability of the substrate, for example, the surface of the polyimide film using the "silane coupling agent of the Republic of Korea Patent Application No. 2004-0098949 Modification method, manufacturing method of copper foil laminated film using same and copper foil laminated film of two-layer structure produced therefrom, "Flexible metal laminate and its manufacturing method" of Korean Patent Application No. 2005-0046470 and Korean Patent Application No. 2008-0018482 Only a flexible metal laminate and a method of manufacturing the same having a stable dimension change rate are disclosed, and a method of reducing or eliminating the possibility of occurrence of a copper pattern crack which may cause a short circuit in a COF product as described above is disclosed. There is no solution for this.

Accordingly, an object of the present invention is to solve a conventional problem in a laminated structure of a flexible circuit board requiring the above fine pattern, and even in the case of a fine pattern by changing the conditions of each layer constituting the flexible circuit board. It is an object of the present invention to provide a method for manufacturing a flexible printed circuit board laminated structure that can improve a crack generation phenomenon of a copper pattern which may cause a short circuit of a wiring by a process.

Another object of the present invention is to provide a flexible printed circuit board laminated structure which improves the occurrence of cracks in the copper pattern manufactured by the above-described manufacturing method.

The present invention may also be aimed at achieving, in addition to the above-mentioned specific objects, other objects which can be easily derived by those skilled in the art from this and the overall description of the present specification.

The above object of the present invention is to adjust the thickness of the polyimide used as the base substrate to lower the repulsive force of the film itself, and also to adjust the particle size of the Ni-Cr used as the tie layer to have excellent bending resistance while cracking the copper pattern Achieved by significantly improving the likelihood of occurrence.

Method of manufacturing a flexible printed circuit board laminated structure to improve the generation of copper pattern cracks of the present invention for achieving the above object;

(a) surface treating polyimide, which is a base film, using a vacuum apparatus;

(b) sequentially depositing a Ni-Cr layer and a copper seed layer, which are tie layers serving as metal conductive layers, by using a physical vapor deposition method (PVD), which is a vacuum deposition method, on the surface of the polyimide film surface treated in the step; And

(c) electrodepositing copper on the polyimide film on which the conductive layer is deposited by using electroplating;

The polyimide film has a thickness not exceeding 35 μm, and a Ni-Cr target has a composition ratio of Ni of 80% or more and a grain size of the target of 100 μm or less.

According to another configuration of the present invention, the surface treatment of the base film in the step (a) is characterized in that it is performed using a plasma.

According to another configuration of the present invention, the thickness of the conductive layer deposited by the sputtering method in the step (b) is characterized in that a total of 1,000 kPa to 2,000 kPa.

According to another configuration of the present invention, the thickness of the conductive layer deposited by the sputtering method in the step (b) is the thickness of Ni-Cr, which is a tie layer of 200Å or more, the copper (Cu) layer of the seed layer is 800Å or more It is characterized by.

According to another configuration of the present invention, the copper sulfate aqueous solution, the additive with a carrier component and a leveler component and the polishing agent for controlling the surface gloss by maintaining a constant concentration in the plating solution in the step (c) at least 0.5A / dm 2 to 3A / It is characterized in that the current density of dm2 to be sequentially increased.

Laminated structure for flexible circuit board with improved bend resistance for achieving another object of the present invention;

(a) surface treating polyimide, which is a base film, using a vacuum apparatus;

(b) sequentially depositing a Ni-Cr layer and a copper seed layer, which are tie layers serving as metal conductive layers, by using a physical vapor deposition method (PVD), which is a vacuum deposition method, on the surface of the polyimide film surface treated in the step; And

(c) prepared by electrodepositing copper on the polyimide film on which the conductive layer is deposited by using electroplating;

The polyimide film has a thickness not exceeding 33 μm, the composition ratio of the Ni-Cr target is characterized in that the content of Ni is 80% or more and the grain size of the target is 100 μm or less.

The method of manufacturing a flexible printed circuit board laminate structure having improved copper pattern crack generation according to the present invention, which is configured as described above, is used to make the thickness of polyimide, which is a base film, thin so as not to exceed 35 μm from the conventional 38 μm. Solve the short circuit problem by minimizing the repulsion force and also reducing the grain size of Ni-Cr to minimize the sputtering thickness variation and improving the mechanical strength (Young's modulus) to minimize the crack occurrence of the copper pattern caused by external stress Can be.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in more detail by preferred embodiments.

1 is a cross-sectional view of a laminated structure manufactured according to an embodiment of the present invention, Figure 2 is a view schematically showing a bending resistance measuring method according to the present invention.

The flexible circuit board laminate of the present invention, having a layer structure as shown in FIG. 1, is made of a polyimide film-based layer, a Ni-Cr alloy layer as a tie layer, and a layer sputtered with copper as a conductive layer. After the electroplating has a structure in which the copper plating layer is sequentially electrodeposited. The laminated structure of the present invention having such a configuration is the same as the basic laminated form of COF, which is a flexible circuit board material.

According to a preferred embodiment of the present invention, the laminated structure of the present invention comprises the steps of (a) surface treatment of a polyimide, which is a base film, using a vacuum apparatus, (b) vacuum on the surface of the polyimide film surface-treated in the step Sequentially depositing a Ni-Cr layer and a copper seed layer, which are tie layers serving as metal conductive layers, using physical vapor deposition (PVD), a deposition method, and (c) electroplating the polyimide film on which the conductive layer is deposited. It is prepared by the step of electrodepositing copper using.

As described above, the base film 1 of the laminated structure uses a polyimide film.

The polyimide film is surface treated in the step (a) according to the present invention. The surface treatment of the base film 1 improves the adhesion between the polymer film forming the base film 1 and the metal laminated thereon. RF plasma surface treatment is performed.

At this time, according to the preferred embodiment of the present invention, a polyimide film having a thickness not exceeding 35 μm is used as the base film 1. If the polyimide film having a thickness of more than 35 μm is used, the repulsive force against external stress is large, which is not preferable because of high possibility of cracking of the copper pattern during the process. Most preferably, a polyimide film having a thickness of 32 to 34 μm is used. The polyimide film having a thickness of less than 32 mu m is not preferable because the strength as the base film is too low.

The main effect of the RF plasma treatment according to the present invention is to first increase the surface roughness of the polymer to increase the area in contact with the metal to improve adhesion and to increase the activation of the surface of the polymer through the surface treatment to bond with other materials It plays a role in making you do well. The plasma treatment according to the invention is preferably usually surface treated with an active gas, for example nitrogen, oxygen or the like.

In addition, in the method of manufacturing a laminate structure for a flexible circuit board according to the present invention, in the step (b), the tie layer 2 is Ni-Cr on the surface-treated polymer film to a thickness of 100 to 300 kPa. By vapor deposition.

According to a preferred embodiment of the present invention, the tie layer 2 is formed of an alloy of nickel and chromium, and it is preferable to use a Ni-Cr alloy having a Ni content of 80 to 90%.

According to a preferred embodiment of the present invention, the grain size of the Ni-Cr target forming the tie layer 2 is 100 µm or less, more preferably 70 to 80 µm. When the grain size particles exceed 100 μm, the variation in the sputtering thickness is increased and the mechanical strength is poor, which is not preferable because the possibility of cracking of the copper pattern due to external stress increases significantly.

After depositing the tie layer 2 as described above, a seed layer 3 made of copper is deposited thereon to a thickness of about 800 mm 3.

Next, according to the method of the preferred embodiment of the present invention, the copper seed layer 3 is formed by sputtering, and then electroplating is performed using copper sulfate and sulfuric acid as the base materials to form the electroplating layer 4. In forming the electroplating layer 4, an additive having a carrier component and a leveler component in a copper sulfate aqueous solution and a polishing agent for controlling surface gloss are used for productivity and surface uniformity.

The leveler according to the present invention is adsorbed on the cathode surface (Cu / Ni-Cr / polyimide) and the cathode surface close to the anode, that is, the adsorption is concentrated on the protruding portion to lower the plating rate of the copper while lowering the current efficiency Play a role. In addition, the brightening agent is adsorbed on the surface of the cathode to act as a catalyst in the reduction reaction of Cu ²⁺ ions to increase the plating rate of copper and to suppress the growth of grains to form uniform and small crystals.

In the method of manufacturing a laminate structure for a flexible circuit board of the present invention, in the step (c), Cu seed layer by sequentially increasing the applied current to at least 0.5A / dm 2 to 3A / dm 2 electrolytic plating in a copper electrolytic plating solution The electrolytic plating layer 4 made of copper is formed on the (3) / Ni-Cr tie layer 2 / polyimide substrate film 1.

The method for manufacturing a laminate structure for a flexible circuit board of the present invention may additionally include post-treatment steps including anti-rust treatment for oxidation prevention in addition to the above steps.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are provided to make the present invention more understandable, and the scope of the present invention is not limited thereto.

Example 1

Polyimide (Polyimide, Kaponton 130EN-C from Dupont, 33 μm) was subjected to RF plasma surface treatment using nitrogen gas under vacuum. At this time, the surface treatment power was 2 kW.

The surface-treated polyimide film was formed using a product of Ni-Cr, which is a tie layer of Ni-Cr (purity of 99.9% or more), by using DC magnetron sputtering. The grain size of the target was about 70 to 80 μm. The product was deposited using a vacuum and then a conductive layer of copper (purity 99.995% or higher) was vacuum deposited.

Sputtering was performed using argon gas, which is an inert gas, to maintain a vacuum of about ¹ × 10 ⁻¹ Pa, and deposited Ni—Cr at a thickness of 250 kPa and copper at 800 kPa or more, regardless of grain size. The thickness of the deposited Ni-Cr and Cu was measured using a thin film XRF device.

The copper plating layer was formed based on the copper sulfate plating liquid in the product in which the polyimide layer and the conductive layer were formed. The copper plating layer having such a structure may be formed by controlling additives and polishes in the electrolyte solution during the usual electroplating for copper plating.

Comparative Example 1

Example 1 except that polyimide (kapton 150EN-C, 38 μm from dupont) was used as the base film and the Ni-Cr target was deposited using a product having a composition ratio of 80% or more Ni and a grain size of 200 μm or more. It was as follows.

Comparative Example 2

The polyimide (polyimide, kapton 150EN-C, 38 μm from dupont) is used as the base film, and the Ni-Cr target is deposited using a product having a composition ratio of 80% or more Ni and a grain size of 70 to 80 μm or more. Example 1 was carried out.

Experimental Example

Specimens of the flexible circuit board laminate structure prepared according to the above Examples and Comparative Examples were measured using a bending resistance tester. In detail, the specimen of the structure is subjected to an etching process to form a copper pattern as shown in FIG. 2, and then the jig is bitten by a jig reciprocating 135 degrees left and right, 50 times, 70 times, 100 times, 130 times, 150 times, 170 times. After reciprocating 200 times, the crack state of the copper pattern was measured by a tool microscope (magnification × 50).

The measurement results are shown in Table 1 below.

division Example 1 Comparative Example 1 Comparative Example 2 50 times 0% 0% 0% 70 times 0% 0% 0% 100 times 0% 10 to 20% 5-10% 130 times 10-20% 50-60% 30-40% 150 times 30-40% 70-80% 50-60% 170 times 60-70% 100% 80-90% 200 times 100% - 100%

As can be seen in Table 1, the smaller the grain size of the Ni-Cr target can be confirmed that the amount of cracks reduced through Comparative Example 1 and Comparative Example 2 and polyimide film through Example 1 and Comparative Example 2 results When the thickness of 33 micrometers was used, it can be seen that the occurrence of cracks is reduced.

1 is a cross-sectional view of a laminated structure manufactured according to one embodiment of the present invention,

2 is a view schematically showing a method of measuring the bending resistance according to the present invention.

* Explanation of symbols for the main parts of the drawings

1: base film

2: tie layer

3: seed layer

4: plating layer

Claims (6)

(a) surface treating polyimide, which is a base film, using a vacuum apparatus; (b) sequentially depositing a Ni-Cr layer and a copper seed layer, which are tie layers serving as metal conductive layers, by using a physical vapor deposition method (PVD), which is a vacuum deposition method, on the surface of the polyimide film surface treated in the step; And (c) electrodepositing copper on the polyimide film on which the conductive layer is deposited by utilizing electroplating; The polyimide film has a thickness not exceeding 35 μm, and a Ni-Cr target has a composition ratio of Ni of 80% or more and a grain size of the target of 100 μm or less. A method of manufacturing a flexible printed circuit board laminate structure having improved crack generation. The method of claim 1, wherein the surface treatment of the base film in step (a) is performed using plasma. The method according to claim 1, wherein the thickness of the conductive layer deposited by the sputtering method in the step (b) is to produce a flexible circuit board laminated structure with improved copper pattern crack generation, characterized in that a total of 1,000 kPa to 2,000 kPa. Way. The thickness of the conductive layer deposited by the sputtering method in the step (b) is a thickness of Ni-Cr, which is a tie layer, 200 Å or more, the copper (Cu) layer of the seed layer is 800 Å or more. A method for manufacturing a flexible printed circuit board laminate structure having improved copper pattern crack generation. The method according to claim 1, wherein in the step (c), the copper sulfate aqueous solution, the additive having the carrier component and the leveler component, and the polishing agent for adjusting the surface gloss are maintained at a constant concentration to maintain a current of at least 0.5 A / dm 2 to at most 3 A / dm 2. 12. A method of manufacturing a flexible printed circuit board laminate structure having improved copper pattern crack generation, characterized by increasing density sequentially. Claims 1 to 5, wherein the flexible printed circuit board laminated structure with improved copper pattern crack generation, characterized in that obtained.

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