Flexible circuit board, electronic device comprising same, and manufacturing method thereof

Abstract

The present invention relates to a flexible circuit board, an electronic device comprising same, and a manufacturing method thereof, and more specifically relates to a flexible circuit board having excellent insulation reliability and product reliability as well as excellent heat dissipation performance, an electronic device comprising same, and a manufacturing method thereof.

Description

Flexible circuit board, electronic device including same, and manufacturing method thereof

[0001] The present invention relates to a flexible circuit board, an electronic device including the same, and a method for manufacturing the same, and more particularly, to a flexible circuit board having excellent heat dissipation performance as well as excellent insulation reliability and product reliability, an electronic device including the same, and a method for manufacturing the same.

[0002]

[0003] With the recent trend toward miniaturization of electronic devices, Chip-on-Film (COF) packaging technology utilizing circuit boards is increasingly being used. For example, flexible circuit boards and COF packaging technology utilizing them are being adopted for flat panel displays (FPDs), such as liquid crystal displays (LCDs) and organic light-emitting diode (OLED) displays. These flexible circuit boards can house chips such as Display Driving ICs (DDICs) that drive the flat panel displays. Furthermore, flexible circuit boards form part of electronic devices such as camera modules, inductors, antennas, and semiconductor packages.

[0004] Meanwhile, electronic devices generate a certain amount of heat during operation, which can rapidly increase their internal temperature. If the heat is not dissipated in a timely manner, the electronic device continues to overheat, leading to overheating and malfunctions. Therefore, heat dissipation technology for flexible printed circuit boards, which are directly affected by the heat generated by electronic devices, is crucial.

[0005]

[0006] The present invention has been devised to solve the above problems, and its purpose is to provide a flexible circuit board having excellent heat dissipation performance as well as excellent insulation reliability and product reliability, an electronic device including the same, and a manufacturing method thereof.

[0007]

[0008] In order to solve the above-described problem, the flexible circuit board of the present invention may include a base film having a circuit pattern formed on one surface thereof, a protective layer formed on one surface of the base film to cover the circuit pattern, and a heat dissipation layer formed on one surface of the protective layer.

[0009] In a preferred embodiment of the present invention, the heat dissipation layer may include a metal-carbon composite and a precious metal.

[0010] In a preferred embodiment of the present invention, the metal-carbon composite may include metal particles having a carbon structure coated on the surface.

[0011] In a preferred embodiment of the present invention, the precious metal may include at least one selected from silver (Ag), gold (Au), platinum (Pt), and palladium (Pd).

[0012] In a preferred embodiment of the present invention, the carbon structure may include at least one selected from graphene, single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), and graphite.

[0013] In a preferred embodiment of the present invention, the metal particles may include at least one selected from copper (Cu) particles, nickel (Ni) particles, iron (Fe) particles, aluminum (Al) particles, and silver (Ag) particles.

[0014] In a preferred embodiment of the present invention, the carbon structure can be coated on the surface of the metal particle with an average thickness of 1 nm to 10 nm.

[0015] In a preferred embodiment of the present invention, the metal particles may have an average particle diameter of 0.1 μm to 10 μm.

[0016] In a preferred embodiment of the present invention, the precious metal may have an average particle diameter of 100 nm to 900 nm.

[0017] In a preferred embodiment of the present invention, the heat dissipation layer may include a metal-carbon composite and a precious metal in a weight ratio of 90:10 to 70:30.

[0018] In a preferred embodiment of the present invention, the heat dissipation layer may have an average thickness of 5 to 25 μm.

[0019] Meanwhile, the method for manufacturing a flexible circuit board of the present invention may include a first step of preparing a base film having a circuit pattern formed on one surface, a second step of forming a protective layer on one surface of the base film to cover the circuit pattern, and a third step of printing a heat-dissipating ink composition on one surface of the protective layer and then drying it to form a heat-dissipating layer.

[0020] In a preferred embodiment of the present invention, the heat-dissipating ink composition may include a metal-carbon composite and a precious metal.

[0021] In a preferred embodiment of the present invention, the heat-dissipating ink composition may have a viscosity of 10,000 cps to 50,000 cps and a thixotropic index of 0.3 to 0.7.

[0022] In a preferred embodiment of the present invention, drying can be performed at a temperature of 120°C to 180°C.

[0023] In a preferred embodiment of the present invention, printing can be performed by a screen printing method, a dispensing method, a toner method, or a pad printing method.

[0024] Furthermore, the electronic device of the present invention includes the flexible circuit board of the present invention.

[0025] The electronic device of the present invention may be a camera module, an inductor, an antenna, or a semiconductor package.

[0026]

[0027] The flexible circuit board of the present invention, the electronic device including the same, and the manufacturing method thereof not only have excellent heat dissipation performance, but also have excellent insulation reliability and product reliability.

[0028]

[0029] Figure 1 is a cross-sectional view of a flexible circuit board according to a preferred embodiment of the present invention.

[0030] Figure 2 is a conceptual diagram illustrating the state of components constituting a heat dissipation layer according to a preferred embodiment of the present invention.

[0031] Figure 3 is a drawing showing the results of evaluating the heat dissipation performance of each of the flexible circuit boards manufactured in Example 1 and Comparative Examples 1 to 3 using a thermal imaging camera.

[0032]

[0033] Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description have been omitted for clarity of description, and the same reference numerals are assigned to identical or similar components throughout the specification.

[0034]

[0035] Referring to FIG. 1, the flexible circuit board of the present invention may include a base film (10) having a circuit pattern (11) formed on one surface, a protective layer (20) formed on one surface of the base film (10) to cover the circuit pattern (11), and a heat dissipation layer (30) formed on one surface of the protective layer (20).

[0036] First, the base film (10) is a film that serves as a base substrate of a flexible circuit board, and any polymer insulating film used in the art can be used, and preferably, it can include at least one selected from a polyimide (PI) film, a polyethylene (PE) film, and a polyethylene naphthalate (PEN) film. In addition, the base film (10) can have an average thickness of 12 µm to 50 µm, and preferably, 25 µm to 38 µm. In addition, the circuit pattern (11) can be formed through a photolithography method, and any conductive metal used in the art can be used, and preferably, it can include at least one selected from copper and aluminum.

[0037] Next, the protective layer (20) is a layer that serves to protect the circuit pattern (11), and may include at least one selected from polyimide (PI) resin, polyethylene (PE) resin, polyethylene naphthalate (PEN) resin, urethane resin, and epoxy resin, and preferably may include solder resist. In addition, the protective layer (20) may have an average thickness of 5 μm to 30 μm, preferably 7 μm to 15 μm.

[0038] Next, the heat dissipation layer (30) may include a metal-carbon composite and a noble metal. Specifically, referring to FIG. 2, the heat dissipation layer (30) may form a heat transfer network between the metal-carbon composite and the noble metal, between the metal-carbon composite and the metal-carbon composite, and / or between the noble metal and the noble metal, thereby ensuring excellent heat dissipation performance.

[0039] Specifically, the metal-carbon composite may include metal particles having a carbon structure coated on the surface.

[0040] At this time, the carbon structure may include at least one selected from graphene, single-wall carbon nanotubes (SWCNTs), multi-wall carbon nanotubes (MWCNTs), and graphite, and preferably may include graphene.

[0041] In addition, the metal particles may include at least one selected from copper (Cu) particles, nickel (Ni) particles, iron (Fe) particles, aluminum (Al) particles, and silver (Ag) particles, and preferably may include copper particles.

[0042] In addition, the carbon structure can be coated on the surface of the metal particle with an average thickness of 1 nm to 10 nm. If the average thickness is less than 1 nm, there may be a problem of the metal particle being oxidized, and if it exceeds 10 nm, there may be a problem of reduced thermal and / or electrical conductivity.

[0043] In addition, the metal particles may have an average particle diameter of 0.1 ㎛ to 10 ㎛, preferably an average particle diameter of 1 ㎛ to 5 ㎛, and more preferably an average particle diameter of 1 ㎛ to 3 ㎛. If the average particle diameter is less than 0.1 ㎛, there may be a problem with bonding to the substrate, and if it exceeds 10 ㎛, there may be a problem with increasing the difficulty of the printing process, and there may be a problem with interfering with the flexibility of the substrate.

[0044] In addition, the precious metal may include at least one selected from silver (Ag), gold (Au), platinum (Pt), and palladium (Pd). At this time, the precious metal may be a nanoparticle having an average particle diameter of 100 nm to 900 nm, preferably an average particle diameter of 400 nm to 800 nm. If the average particle diameter is less than 100 nm, there may be a problem of increased fluidity of the heat-dissipating ink composition, and if it exceeds 900 nm, there may be a problem of decreased filling rate between different metal particles.

[0045] Meanwhile, the heat dissipation layer (30) may contain a metal-carbon composite and a precious metal in a weight ratio of 90:10 to 70:30, preferably 90:10 to 80:20. If the metal-carbon composite is contained in a weight ratio of less than 70, there may be a problem of reduced bonding strength at low temperatures, and if the weight ratio exceeds 90, there may be a problem of hindering heat diffusion due to conductivity.

[0046] In addition, the heat dissipation layer (30) may have an average thickness of 5 µm to 25 µm, preferably an average thickness of 10 µm to 20 µm, and more preferably an average thickness of 13 µm to 17 µm. If the average thickness is less than 5 µm, there may be a problem with the bonding strength with the protective layer (20), and if it exceeds 25 µm, there may be a problem with the flexibility of the flexible circuit board being reduced.

[0047]

[0048] Meanwhile, the method for manufacturing a flexible circuit board of the present invention may include steps 1 to 3.

[0049] First, in the first step of the method for manufacturing a flexible circuit board of the present invention, a base film having a circuit pattern formed on one surface may be prepared. At this time, the prepared base film is as described above.

[0050] Next, in the second step of the method for manufacturing a flexible circuit board of the present invention, a protective layer may be formed on one surface of the base film prepared in the first step to cover the circuit pattern. The formed protective layer is as described above and may be formed using a screen printing method.

[0051] Finally, the third step of the method for manufacturing a flexible circuit board of the present invention can form a heat dissipation layer by printing a heat dissipation ink composition on one side of the protective layer formed in the second step and then drying it.

[0052] At this time, the heat-dissipating ink composition may include a metal-carbon complex and a noble metal, and preferably may be manufactured by adding and mixing the metal-carbon complex and the noble metal into a solvent. At this time, the metal-carbon complex and the noble metal are as described above, and the solvent may be at least one selected from glycol ether, butyl carbitol acetate (BCA), butyl triglyceride (BTG), and ethanol.

[0053] Meanwhile, the heat-resistant ink composition may have a viscosity of 10,000 cps to 50,000 cps, preferably 15,000 cps to 25,000 cps. If the viscosity is less than 10,000 cps, there may be problems with collapse and / or spreading of the printed pattern, and if it exceeds 50,000 cps, there may be problems with the filling rate and / or wettability of the printed pattern.

[0054] In addition, the heat-resistant ink composition may have a thixotropic index of 0.3 to 0.7, preferably a thixotropic index of 0.3 to 0.5. The thixotropic index is an indicator of thixotropy. If the thixotropic index is less than 0.3, there may be a problem of increased bleed and / or curl, and if it exceeds 0.7, there may be a problem of increased thickness deviation and / or pinholes.

[0055] In addition, the drying in the third stage can be performed at a temperature of 120℃ to 180℃, preferably 120℃ to 140℃. If the temperature is lower than 120℃, there may be a problem of the heat dissipation layer being peeled off, and if it exceeds 180℃, there may be a problem of discoloration.

[0056] Additionally, the third step printing can be performed using a screen printing method, a dispensing method, a toner method, or a pad printing method.

[0057]

[0058] Meanwhile, the electronic device of the present invention may include the flexible circuit board of the present invention, and the electronic device may be, but is not limited to, a camera module, an inductor, an antenna, or a semiconductor package.

[0059]

[0060] Hereinafter, the present invention will be described in more detail through examples, but the following examples do not limit the scope of the present invention, and should be interpreted as helping to understand the present invention.

[0061]

[0062] Preparation Example 1: Preparation of heat-resistant ink composition

[0063] A heat-dissipating ink composition having a viscosity of 30,000 cps and a thixotropic index of 0.5 was prepared by adding and mixing a metal-carbon composite and a precious metal to a solvent. At this time, the metal-carbon composite and the precious metal were mixed in a weight ratio of 90:10, and glycol ether was used as the solvent. As the metal-carbon composite, copper particles having an average particle diameter of 2 μm and graphene coated on the surface with an average thickness of 5 nm were used, and as the precious metal, silver nanoparticles having an average particle diameter of 700 nm were used.

[0064]

[0065] Example 1: Manufacturing of the flexible circuit board of the present invention

[0066] (1) A polyimide film having an average thickness of 35㎛ was prepared as a base film.

[0067] (2) A circuit pattern with an average thickness of 8 μm was formed on one side of the base film prepared through the photolithography method. At this time, liquid photoresist was used as the circuit pattern forming material.

[0068] (3) A protective layer having an average thickness of 10 μm was formed on one side of the base film on which the circuit pattern was formed using a screen printing method to cover the formed circuit pattern. At this time, solder resist was used as the protective layer forming material.

[0069] (4) A flexible circuit board was manufactured by printing the heat-dissipating ink composition manufactured in Preparation Example 1 on one side of the protective layer using a screen printing method and drying it at a temperature of 127°C to form a heat-dissipating layer having an average thickness of 15 μm.

[0070]

[0071] Comparative Example 1: Manufacturing of a Flexible Circuit Board

[0072] (1) A polyimide film having an average thickness of 35㎛ was prepared as a base film.

[0073] (2) A circuit pattern with an average thickness of 8 μm was formed on one side of the base film prepared through the photolithography method. At this time, liquid photoresist was used as the circuit pattern forming material.

[0074] (3) A flexible circuit board was manufactured by forming a protective layer with an average thickness of 10 μm on one side of the base film on which the circuit pattern was formed using a screen printing method to cover the formed circuit pattern. At this time, solder resist was used as the protective layer forming material.

[0075]

[0076] Comparative Example 2: Manufacturing of a Flexible Circuit Board

[0077] (1) A polyimide film having an average thickness of 35㎛ was prepared as a base film.

[0078] (2) A circuit pattern with an average thickness of 8 μm was formed on one side of the base film prepared through the photolithography method. At this time, liquid photoresist was used as the circuit pattern forming material.

[0079] (3) A protective layer having an average thickness of 10 μm was formed on one side of the base film on which the circuit pattern was formed using a screen printing method to cover the formed circuit pattern. At this time, solder resist was used as the protective layer forming material.

[0080] (4) A flexible circuit board was manufactured by attaching an aluminum (Al) metal tape having an average thickness of 70㎛ to the base film surface.

[0081]

[0082] Comparative Example 3: Manufacturing of a Flexible Circuit Board

[0083] (1) A polyimide film having an average thickness of 35㎛ was prepared as a base film.

[0084] (2) A circuit pattern with an average thickness of 8 μm was formed on one side of the base film prepared through the photolithography method. At this time, liquid photoresist was used as the circuit pattern forming material.

[0085] (3) A protective layer having an average thickness of 10 μm was formed on one side of the base film on which the circuit pattern was formed using a screen printing method to cover the formed circuit pattern. At this time, solder resist was used as the protective layer forming material.

[0086] (4) A flexible circuit board was manufactured by attaching a copper (Cu) metal tape having an average thickness of 70㎛ to the base film surface.

[0087]

[0088] Experimental Example 1: Heat dissipation performance evaluation

[0089] In order to evaluate the heat dissipation performance of each of the flexible circuit boards manufactured in Example 1 and Comparative Examples 1 to 3, a hot plate heated to 135°C was prepared. The flexible circuit boards manufactured in Example 1 and Comparative Examples 1 to 3 were laminated so that one surface of the prepared hot plate and the base film of the flexible circuit boards manufactured in Example 1 and Comparative Examples 1 to 3 were in contact, and after 10 minutes, the temperatures of the flexible circuit boards manufactured in Example 1 and Comparative Examples 1 to 3 were measured using a thermal imaging camera, and the results are shown in Fig. 3 below.

[0090] As can be seen in Fig. 3, compared to the flexible circuit board manufactured in Comparative Example 1, the flexible circuit board manufactured in Example 1 was found to have a temperature drop of 41.8 degrees, the flexible circuit board manufactured in Comparative Example 3 was found to have a temperature drop of 28.4 degrees, and the flexible circuit board manufactured in Comparative Example 2 was found to have a temperature drop of 13.9 degrees. Through these results, it was confirmed that the flexible circuit board manufactured in Example 1 had the best heat dissipation effect.

[0091]

[0092] Experimental Example 2: Insulation Reliability Evaluation

[0093] The insulation reliability of the flexible circuit board manufactured in Example 1 was evaluated using ESPEC's AMI-050-U-5 equipment. The insulation reliability evaluation was conducted for 96 hours under the conditions of temperature 130℃, humidity 80%, and voltage 60V. If migration did not occur during the evaluation period, it was marked as '○', and if migration occurred, it was marked as 'X', and this is shown in Table 1 below.

[0094]

[0095] Experimental Example 3: Product Reliability Evaluation

[0096] 1) Tape adhesive strength evaluation

[0097] The tape adhesion of the flexible circuit board manufactured in Example 1 was evaluated. The adhesion was evaluated by applying pressure to the printed interface of the input / output terminal of the flexible circuit board with cellophane tape (3M 610) and then peeling it off instantly in a 180-degree direction from the surface within 1 second, and the peeling phenomenon of the heat dissipation layer, circuit protection layer, and circuit plating layer was confirmed. If no peeling phenomenon occurred after the evaluation, it was marked as '○', and if peeling phenomenon occurred, it was marked as 'X', and these results are shown in Table 1 below.

[0098]

[0099] 2) Chemical resistance evaluation

[0100] The chemical resistance of the flexible circuit board manufactured in Example 1 was evaluated. The chemical resistance was evaluated by ultrasonically dipping the flexible circuit board in IPA and acetone solutions at 25°C for 5 minutes each, and checking for any appearance deformation (swell, delamination, corrosion, cracks, etc.). If no appearance deformation occurred after the evaluation, it was marked with '○', and if appearance deformation occurred, it was marked with 'X', and these are shown in Table 1 below.

[0101]

[0102] 3) Pencil strength evaluation

[0103] The pencil strength of the flexible circuit board manufactured in Example 1 was evaluated. The pencil strength was measured by fixing the flexible circuit board to a measuring stage and using a strength measuring pencil from 9H to 9B to scratch the film surface at an angle of 45 degrees and a force of 500 gf. If no peeling of the heat dissipation layer occurred after the evaluation, it was marked as '○', and if peeling occurred, it was marked as 'X', and this is shown in Table 1 below.

[0104]

[0105] 4) High temperature and high humidity reliability evaluation

[0106] The high-temperature and high-humidity reliability of the flexible circuit board manufactured in Example 1 was evaluated using ESPEC's EHS-211M equipment. The high-temperature and high-humidity reliability evaluation was conducted for 96 hours under conditions of temperature 121℃ and humidity 100%. If no appearance deformation occurred after the evaluation, it was marked as '○', and if appearance deformation occurred, it was marked as 'X', and this is shown in Table 1 below.

[0107]

[0108] 5) High-temperature storage reliability evaluation

[0109] The high-temperature storage reliability of the flexible circuit board manufactured in Example 1 was evaluated using ESPEC's PHH-202M equipment. The high-temperature storage reliability evaluation was conducted at a temperature of 150°C for 168 hours. If no appearance deformation occurred after the evaluation, it was marked as '○', and if appearance deformation occurred, it was marked as 'X', and this is shown in Table 1 below.

[0110]

[0111] 6) Temperature cycle reliability evaluation

[0112] The temperature cycle reliability of the flexible circuit board manufactured in Example 1 was evaluated using the ES-56L equipment of HITACHI. The temperature cycle reliability evaluation was performed for 100 cycles after maintaining the temperature at 125℃ / -55℃ for 30 minutes each. If no external deformation occurred after the evaluation, it was marked as '○', and if external deformation occurred, it was marked as 'X', and this is shown in Table 1 below.

[0113]

[0114] As can be confirmed in Table 1 above, the flexible circuit board manufactured in Example 1 was confirmed to have excellent insulation reliability and product reliability.

[0115]

[0116] Simple modifications or changes of the present invention can be easily implemented by a person having ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims

1. Base film with a circuit pattern formed on one side; A protective layer formed on one side of the base film to cover the above circuit pattern; and A heat dissipation layer formed on one surface of the protective layer; A flexible circuit board characterized in that the heat dissipation layer comprises a metal-carbon composite and a precious metal.

2. In paragraph 1, The above metal-carbon composite comprises metal particles having a carbon structure coated on the surface, A flexible circuit board characterized in that the above precious metal includes at least one selected from silver (Ag), gold (Au), platinum (Pt), and palladium (Pd).

3. In paragraph 2, The above carbon structure includes at least one selected from graphene, single-wall carbon nanotubes (SWCNTs), multi-wall carbon nanotubes (MWCNTs), and graphite. A flexible circuit board, characterized in that the metal particles include at least one selected from copper (Cu) particles, nickel (Ni) particles, iron (Fe) particles, aluminum (Al) particles, and silver (Ag) particles.

4. In paragraph 2, The above carbon structure is coated on the surface of the metal particle with an average thickness of 1 nm to 10 nm, The above metal particles have an average particle diameter of 0.1㎛ to 10㎛, A flexible circuit board characterized in that the above precious metal has an average particle diameter of 100 nm to 900 nm.

5. In paragraph 1, A flexible circuit board characterized in that the heat dissipation layer comprises a metal-carbon composite and a precious metal in a weight ratio of 90:10 to 70:

30.

6. In paragraph 1, A flexible circuit board characterized in that the heat dissipation layer has an average thickness of 5 μm to 25 μm.

7. Step 1: Preparing a base film with a circuit pattern formed on one side; A second step of forming a protective layer on one side of the base film to cover the above circuit pattern; and A third step of printing a heat-dissipating ink composition on one side of the protective layer and then drying it to form a heat-dissipating layer; A method for manufacturing a flexible circuit board, characterized in that the heat-dissipative ink composition comprises a metal-carbon composite and a precious metal.

8. In paragraph 7, A method for manufacturing a flexible circuit board, characterized in that the heat-dissipative ink composition has a viscosity of 10,000 cps to 50,000 cps and a thixotropic index of 0.3 to 0.

7.

9. In paragraph 7, A method for manufacturing a flexible circuit board, characterized in that the above drying is performed at a temperature of 120°C to 180°C.

10. In paragraph 7, A method for manufacturing a flexible circuit board, characterized in that the above printing is performed using a screen printing method, a dispensing method, a toner method, or a pad printing method.

11. An electronic device including a flexible circuit board of paragraph 1.

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