Circuit Board

Abstract

According to an embodiment, a circuit board includes: an insulating portion, which includes a plurality of insulating layers; a circuit pattern, which is arranged on the surface of the plurality of insulating layers; and a through hole, which is arranged in the plurality of insulating layers and connects the circuit patterns arranged on different layers, wherein each of the plurality of insulating layers includes resin coated copper (RCC) and has a dielectric constant of 2.03 to 2.7.

Description

Technical Field

[0001] The present embodiment relates to a circuit board, and more particularly, to a circuit board including an insulating layer having a low dielectric constant and a low thermal expansion coefficient. Background Art

[0002] A printed circuit board (PCB) is formed by printing a circuit line pattern with a conductive material (such as copper) on an electrically insulating substrate, and refers to a board immediately before electronic components are mounted. That is, in order to densely mount a variety of electronic devices on a flat board, the flat board refers to a circuit board on which the mounting position of each part is determined and the circuit pattern connecting these parts is printed on the surface of the flat board and fixed.

[0003] Generally, OSP (Organic Solderability Preservative), electrolytic nickel / gold, electrolytic nickel / gold-cobalt alloy, electroless nickel / palladium / gold may be used as a surface treatment method for the circuit pattern included in the printed circuit board as described above.

[0004] In this case, the surface treatment method used varies depending on its use, for example, the use includes welding use, wire bonding use, connector use, and the like.

[0005] Components mounted on a printed circuit board may transmit signals generated from the components through a circuit pattern connected to each component.

[0006] On the other hand, recent portable electronic devices and the like have become increasingly more functional, and high-frequency signals are being developed in order to process a large amount of information at high speed, and therefore, circuit patterns of printed circuit boards suitable for high-frequency applications are required.

[0007] In order to enable transmission of such a circuit pattern of a printed circuit board without degrading the quality of high-frequency signals, reduction in transmission loss is desired.

[0008] The transmission loss of the circuit pattern of the printed circuit board is mainly composed of conductor loss caused by copper foil and dielectric loss caused by insulator.

[0009] The conductor loss due to the copper foil is related to the surface roughness of the circuit pattern. That is, as the surface roughness of the circuit pattern increases, the transmission loss may increase due to the skin effect.

[0010] Therefore, when the surface roughness of the circuit pattern is reduced, there is an effect of preventing the transmission loss from being reduced, but there is a problem that the adhesion between the circuit pattern and the insulating layer is reduced.

[0011] In addition, in order to reduce the dielectric constant, a material with a small dielectric constant can be used as the insulating layer of the circuit board.

[0012] However, in circuit boards for high-frequency applications, the insulating layer also requires chemical and mechanical properties for use in the circuit board in addition to a low dielectric constant.

[0013] In detail, it should have isotropic electrical properties to facilitate circuit pattern design and processing, low reactivity with metal wiring materials, low ionic conductivity, mechanical strength sufficient to withstand processes such as chemical mechanical polishing (CMP), low moisture absorption (which can prevent delamination or increase in dielectric constant), heat resistance (can overcome processing temperature), low thermal expansion coefficient to eliminate cracking due to temperature changes, and in addition, various conditions (such as adhesion, crack resistance, low stress and low high-temperature gas generation) must be met to minimize various stresses and peeling that may be generated by interfacing with other materials.

[0014] Therefore, there is a need for an insulating layer for high frequency applications, which has a low dielectric constant and a circuit pattern with small surface roughness while improving the adhesion between the insulating layer and the circuit pattern and the above-mentioned chemical and mechanical properties. Summary of the invention

[0015]

Technical issues

[0016] In this embodiment, the circuit board can be made thinner.

[0017] Furthermore, in an embodiment, a circuit board including an insulating layer having a low dielectric constant and a circuit pattern having a low signal loss may be provided.

[0018] Furthermore, in an embodiment, a circuit board having an insulating layer formed only of resin coated copper (RCC) having a low thermal expansion coefficient may be provided.

[0019] Furthermore, in the embodiment, by removing the glass fiber included in the insulating layer, the thickness of the circuit board may be reduced by a thickness corresponding to the glass fiber.

[0020] Furthermore, in an embodiment, a circuit board may be provided in which a thickness of the circuit pattern is greater than a thickness of the insulating layer.

[0021] The technical problems to be solved in the proposed embodiments are not limited to the above-mentioned technical problems, and a person skilled in the art will clearly understand other technical problems not mentioned in the embodiments from the embodiments proposed in the following description.

[0022]

Technical Solution

[0023] According to an embodiment, a circuit board includes: a first insulating part, which includes at least one insulating layer; a second insulating part, which is arranged on the first insulating part and includes at least one insulating layer; and a third insulating part, which is arranged below the first insulating part and includes at least one insulating layer; wherein the insulating layer constituting the first insulating part includes a prepreg containing glass fiber, and wherein each of the insulating layers constituting the second insulating part and the third insulating part is made of resin-coated copper (RCC).

[0024] Furthermore, the thickness of the insulating layer constituting the first insulating portion is greater than the thickness of each of the insulating layers constituting the second insulating portion and the third insulating portion.

[0025] In addition, the circuit board also includes a circuit pattern, which is arranged on the surface of each insulating layer in the first insulating part to the third insulating part, wherein the thickness of the insulating layer constituting the first insulating part is greater than the thickness of the circuit pattern, and wherein the thickness of the insulating layer constituting the second insulating part and the third insulating part is less than the thickness of the circuit pattern.

[0026] In addition, the circuit board also includes a through hole, which is arranged in at least one of the insulating layers constituting the first insulating part to the third insulating part; wherein the thickness of the through hole arranged in the insulating layer constituting the first insulating part is greater than the thickness of the circuit pattern; and wherein the thickness of the through hole arranged in the insulating layer constituting the second insulating part and the third insulating part is less than the thickness of the circuit pattern.

[0027] In addition, each of the insulating layers constituting the second insulating part and the third insulating part includes: a first compound including polyphenylene ether (PPE); and a second compound including tricyclodecane and an end group connected to the tricyclodecane, and wherein a weight ratio of the first compound to the second compound is 4:6 to 6:4.

[0028] Furthermore, the terminal group includes at least one of an acrylate group, an epoxy group, a carboxyl group, a hydroxyl group, and an isocyanate group.

[0029] Furthermore, the first compound and the second compound are not chemically bonded.

[0030] Furthermore, the thermal expansion coefficient and the dielectric constant of each of the insulating layers constituting the second insulating portion and the third insulating portion are smaller than the thermal expansion coefficient and the dielectric constant of the insulating layer constituting the first insulating portion.

[0031] Furthermore, the dielectric constant of each of the insulating layers constituting the second insulating portion and the third insulating portion is 2.03 to 2.7.

[0032] On the other hand, a circuit board according to an embodiment includes: an insulating portion including a plurality of insulating layers; a circuit pattern disposed on surfaces of the plurality of insulating layers; and a through hole disposed in the plurality of insulating layers and connecting the circuit patterns disposed on different layers, wherein each of the plurality of insulating layers is made of resin-coated copper (RCC), and wherein a dielectric constant of each of the plurality of insulating layers is 2.03 to 2.7.

[0033] Furthermore, the thickness of each of the plurality of insulating layers is smaller than the thickness of the circuit pattern.

[0034] Furthermore, the thickness of the through hole is smaller than the thickness of the circuit pattern.

[0035] In addition, each of the multiple insulating layers includes a first material and a second material, wherein the first material includes first compounds chemically bonded to each other, wherein the second material includes second compounds chemically bonded to each other, wherein each of the first compounds includes polyphenylene ether (PPE), wherein each of the second compounds includes tricyclodecane and an end group connected to the tricyclodecane; wherein the second compounds are bonded to each other through the end groups, wherein the end groups include at least one of an acrylate group, an epoxy group, a carboxyl group, a hydroxyl group, and an isocyanate group.

[0036]

Beneficial Effects

[0037] The circuit board according to the embodiment may include a buffer layer disposed between the insulating layer and the circuit pattern.

[0038] That is, in the circuit board according to the embodiment, the buffer layer may be formed on the surface of the circuit pattern, or the buffer layer may be formed on the insulating layer.

[0039] A buffer layer may be disposed between the insulating layer and the circuit pattern to improve adhesion between the insulating layer and the circuit pattern.

[0040] That is, the insulating layer and the circuit pattern are heterogeneous materials including a resin material and a metal, respectively, and when the circuit pattern is formed on the insulating layer, there is a problem in that adhesion is reduced.

[0041] Therefore, by providing a buffer layer chemically bonded to the insulating layer and the circuit pattern between the insulating layer and the circuit pattern, adhesion between the insulating layer and the circuit pattern may be improved.

[0042] That is, the buffer layer includes a plurality of functional groups coupled to the insulating layer and the circuit pattern, and the functional groups are chemically bonded to the insulating layer and the circuit pattern through covalent bonds or coordination bonds, thereby improving adhesion between the insulating layer and the circuit pattern.

[0043] Therefore, even when the surface roughness of the insulating layer is reduced, adhesion reliability between the insulating layer and the circuit pattern can be ensured.

[0044] Therefore, even when the circuit board according to the embodiment is used for high-frequency purposes, the transmission loss of the high-frequency signal can be reduced by maintaining the surface roughness of the circuit pattern low. Even if the surface roughness of the circuit pattern is kept low, the adhesion between the insulating layer and the circuit pattern can be ensured by the buffer layer, and thus the overall reliability of the circuit pattern can be ensured.

[0045] Furthermore, the circuit board according to the embodiment may include an insulating layer having improved strength, a low dielectric constant, and a low thermal expansion coefficient.

[0046] In detail, the insulating layer includes a first material and a second material having a low dielectric constant and improved strength, and since the first material is formed in the insulating layer to be arranged inside the mesh structure of the second material, and thus the phase separation of the first material and the second material can be prevented, the insulating layer can form the first material and the second material into a single phase, thereby improving the strength of the insulating layer.

[0047] That is, by increasing the free volume (i.e., molecular movement) of the second material having a network structure through cross-linking, the polymer chains having a network structure can be structured so that they are not tightly arranged, and since the first material is partially disposed inside the network structure, the first material and the second material can be formed as a single phase inside the insulating layer.

[0048] Therefore, when the circuit board according to the embodiment is used in high-frequency applications, the transmission loss of the high-frequency signal can be reduced by reducing the dielectric constant of the insulating layer, and the overall reliability of the circuit board can be ensured by improving the thermal expansion coefficient and mechanical strength of the insulating layer.

[0049] In addition, since the circuit board according to the embodiment includes an insulating layer having a low dielectric constant and a low thermal window coefficient, it can replace the existing insulating layer including glass fiber. Specifically, the circuit board according to the embodiment can remove the glass fiber included in the insulating layer. Specifically, in the circuit board according to the embodiment, by using the resin and filler constituting RCC (resin coated copper), the dielectric constant and thermal expansion coefficient of the insulating layer can be easily adjusted, and therefore, by configuring the insulating layer as a traditional RCC that does not include glass fiber, the overall thickness of the printed circuit board can be reduced. In addition, since the circuit board according to the embodiment is composed of an insulating layer having a low thermal expansion coefficient, not only can the core layer be removed to ensure strength, but also the thickness of the insulating layer can be reduced, and therefore, an insulating layer having a thickness less than the thickness of the circuit pattern can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a view showing a cross-sectional view of a circuit board according to the first embodiment.

[0051] Figures 2 to 5 1 is a view for explaining an arrangement relationship of a buffer layer of a circuit board according to an embodiment.

[0052] Figure 6 is a view showing a simplified structural formula of a buffer layer of a circuit board according to an embodiment.

[0053] Figure 7 is a view illustrating a structure of a second material included in an insulating layer of a circuit board according to an embodiment.

[0054] Figure 8 is a view for explaining an arrangement structure of a first material and a second material included in an insulating layer of a circuit board according to an embodiment.

[0055] Fig. 9 is a view showing a cross-sectional view of a circuit board according to a second embodiment.

[0056] Fig.10 is a view showing a cross-sectional view of a circuit board according to a third embodiment. DETAILED DESCRIPTION

[0057] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the spirit and scope of the present invention are not limited to a part of the described embodiments, and may be implemented in various other forms, and within the spirit and scope of the present invention, one or more elements of the embodiments may be selectively combined and used in an alternative manner.

[0058] In addition, unless otherwise explicitly defined and described, the terms (including technical terms and scientific terms) used in the embodiments of the present invention may be interpreted as having the same meaning as commonly understood by ordinary technicians in the field to which the present invention belongs, and terms such as those defined in commonly used dictionaries may be interpreted as having a meaning consistent with their meaning in the context of the relevant technology.

[0059] In addition, the terms used in the embodiments of the present invention are used to describe the embodiments and are not intended to limit the present invention. In this specification, unless otherwise specified in a phrase, a singular form may also include a plural form, and when described as "at least one (or more) of A (and), B and C", at least one of all combinations of combinations in A, B and C may be included.

[0060] In addition, when describing the elements of the embodiments of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish an element from other elements, and these terms are not limited to the nature, order, or sequence of the elements.

[0061] In addition, when an element is described as being “connected,” “coupled” or “connected” to another element, it may include not only the element being directly “connected,” “coupled” or “connected” to the other element, but also the element being “connected,” “coupled” or “connected” to the other element through another element between the element and the other element.

[0062] In addition, when described as being formed or arranged “on” or “under” each element, “on” or “under” may not only include two elements being directly connected to each other, but may also include one or more other elements being formed or arranged between the two elements.

[0063] In addition, when expressed as "upper" or "lower", it may include not only an upper direction based on one element but also a lower direction.

[0064] Hereinafter, a circuit board according to an embodiment will be described with reference to the accompanying drawings.

[0065] Figure 1 is a view showing a cross-sectional view of a circuit board according to the first embodiment.

[0066] refer to Figure 1 The circuit board 1000 according to the first embodiment may include an insulating substrate 100, a first pad 160, a first upper metal layer 170, a second pad 180 and a second upper metal layer 190, a first protective layer SR1, a second protective layer SR2, a solder paste 200, and an electronic component 300 (hereinafter, Fig. 9 and Fig.10 A first upper metal layer 170, a second pad 180, and a second upper metal layer 190 are shown.

[0067] The insulating substrate 100 may have a flat plate structure. The insulating substrate 100 may be a printed circuit board (PCB). Here, the insulating substrate 100 may be implemented as a single substrate, or alternatively, may be implemented as a multilayer substrate in which a plurality of insulating layers are sequentially stacked.

[0068] Therefore, the insulating substrate 100 may include a plurality of insulating parts 110, 120, and 130. Figure 1 As shown, the plurality of insulating portions include a first insulating portion 110 , a second insulating portion 120 disposed on the first insulating portion 110 , and a third insulating portion 130 disposed under the first insulating portion 110 .

[0069] In this case, the first insulating part 110, the second insulating part 120 and the third insulating part 130 may be formed of different insulating materials. Preferably, the first insulating part 110 may include glass fiber. In addition, unlike the first insulating part 110, the second insulating part 120 and the third insulating part 130 may not include glass fiber.

[0070] Therefore, the thickness of each insulating layer constituting the first insulating portion 110 may be different from the thickness of each insulating layer constituting the second insulating portion 120 and the third insulating portion 130. In other words, the thickness of each insulating layer constituting the first insulating portion 110 may be greater than the thickness of each insulating layer constituting the second insulating portion 120 and the third insulating portion 130.

[0071] That is, the first insulating part 110 includes glass fiber. Glass fiber generally has a thickness of about 12 μm (micrometer). Therefore, the thickness of each insulating layer constituting the first insulating part 110 may have a thickness of 21 μm ± 2 μm, including the thickness of the glass fiber. Specifically, the thickness of each insulating layer included in the first insulating part 110 may be in the range of 19 μm to 23 μm.

[0072] Unlike this, the glass fiber is not included in the second insulating part 120. Preferably, each insulating layer constituting the second insulating part 120 may be composed of RCC. Therefore, each insulating layer constituting the second insulating part 120 may have a thickness of 12 μm ± 2 μm. That is, the thickness of each insulating layer constituting the second insulating part 120 may be in the range of 10 μm to 14 μm.

[0073] In addition, the glass fiber is not included in the third insulating part 130. Preferably, each insulating layer constituting the third insulating part 130 may be composed of RCC. Therefore, each insulating layer constituting the third insulating part 130 may have a thickness of 12 μm ± 2 μm. That is, the thickness of each insulating layer constituting the third insulating part 130 may be in the range of 10 μm to 14 μm.

[0074] That is, the insulating part constituting the circuit board in the comparative example includes a plurality of insulating layers, and the plurality of insulating layers are composed of a prepreg (PPG) including glass fibers. In this case, it is difficult to reduce the thickness of the glass fibers based on the PPG of the circuit board in the comparative example. This is because, when the thickness of the PPG is reduced, the glass fibers included in the PPG may be electrically connected to the circuit pattern provided on the surface of the PPG, and thereby induce a crack risk. Therefore, in the case of reducing the thickness of the PPG of the circuit board in the comparative example, dielectric breakdown and damage to the circuit pattern may occur. Therefore, the circuit board in the comparative example has limitations in reducing the overall thickness due to the thickness of the glass fibers constituting the PPG.

[0075] In addition, since the circuit board in the comparative example is composed only of an insulating layer of PPG containing glass fiber, it has a high dielectric constant. However, in the case of a dielectric having a high dielectric constant, there is a problem that it is difficult to access it as a substitute for high frequencies. That is, in the circuit board of the comparative example, since the dielectric constant of the glass fiber is high, the dielectric constant in the high frequency band is destroyed.

[0076] Therefore, in the present embodiment, the insulating layer is formed using RCC having a low dielectric constant, thereby reducing the thickness of the circuit board and providing a high reliability circuit board with minimized signal loss even in a high frequency band. This can be achieved by the properties of the material in each insulating layer constituting the second insulating portion 120 and the third insulating portion 130, which will be described in more detail below.

[0077] The first insulating part 110 may include, from the bottom, first, second, third, and fourth insulating layers 111, 112, 113, and 114. In addition, each of the first, second, third, and fourth insulating layers 111, 112, 113, and 114 may be made of PPG including glass fiber.

[0078] In addition, the second insulating part 120 may include a fifth insulating layer 121 and a sixth insulating layer 122 from the bottom. The fifth insulating layer 121 and the sixth insulating layer 122 constituting the second insulating part 120 may be formed of RCC having a low dielectric constant and a low thermal expansion coefficient.

[0079] In addition, the third insulating part 130 may include a seventh insulating layer 131 and an eighth insulating layer 132 from the top. The seventh insulating layer 131 and the eighth insulating layer 132 constituting the third insulating part 130 may be formed of RCC having a low dielectric constant and a low thermal expansion coefficient.

[0080] Meanwhile, although the first insulating part 110 has been illustrated above as having a four-layer insulating layer structure, it is not limited thereto, and the number of insulating layers constituting the first insulating part 110 may be increased or decreased.

[0081] Furthermore, although the second insulating portion 120 and the third insulating portion 130 have been illustrated as having a two-layered insulating layer structure, the present invention is not limited thereto, and the number of insulating layers constituting the second insulating portion 120 and the third insulating portion 130 may be increased.

[0082] As described above, the circuit board according to the first embodiment includes the first insulating part 110, the second insulating part 120 and the third insulating part 130, and the first insulating part 110 may be made of PPG including glass fiber, and the second insulating part 120 and the third insulating part 130 may be formed of RCC having a low dielectric constant for use in circuit boards applied to high-frequency applications. In addition, the second insulating part 120 and the third insulating part 130 may have a low dielectric constant and simultaneously ensure mechanical / chemical safety, thereby improving the reliability of the circuit board.

[0083] The insulating layers constituting the second insulating portion 120 and the third insulating portion 130 will be described in detail below.

[0084] Meanwhile, the circuit pattern 140 may be provided on a surface of an insulating layer constituting each of the first insulating portion 110 , the second insulating portion 120 , and the third insulating portion 130 .

[0085] Preferably, the circuit pattern 140 may be disposed on at least one surface of each of the first insulating layer 111 , the second insulating layer 112 , the third insulating layer 113 , the fourth insulating layer 114 , the fifth insulating layer 121 , the sixth insulating layer 122 , the seventh insulating layer 131 and the eighth insulating layer 132 .

[0086] The circuit pattern 140 is a wire that transmits an electrical signal and may be formed of a metal material having high conductivity. To this end, the circuit pattern 140 may be formed of at least one metal material selected from gold (Au), silver (Ag), platinum (Pt), titanium (Ti), tin (Sn), copper (Cu), and zinc (Zn).

[0087] In addition, the circuit pattern 140 may be formed of a paste or solder paste including at least one metal material selected from gold (Au), silver (Ag), platinum (Pt), titanium (Ti), tin (Sn), copper (Cu), and zinc (Zn), which has excellent bonding strength. Preferably, the circuit pattern 140 may be formed of copper (Cu) which has high conductivity and is relatively inexpensive.

[0088] In addition, the circuit pattern 140 may have a thickness of 12 μm±2 μm. That is, the thickness of the circuit pattern may be in the range of 10 μm to 14 μm.

[0089] The circuit pattern 140 may be formed using an additive process, a subtractive process, an MSAP (Modified Semi-Additive Process), and a SAP (Semi Additive Process) method, which are possible typical printed circuit board manufacturing processes, and a detailed description thereof will be omitted herein.

[0090] Meanwhile, the buffer layer 400 may be disposed on each of the insulating layers constituting the first insulating portion 110, the second insulating portion 120, and the third insulating portion 130 and / or on the surface of the circuit pattern 140. In detail, the buffer layer 400 may be disposed on a surface of at least one of the top surface, the bottom surface, and the side surface of the circuit pattern 140 or on a surface of the insulating layer on which the circuit pattern is disposed.

[0091] The buffer layer formed on the insulating layer or the circuit pattern will be described in detail below.

[0092] At least one through hole 150 is formed in at least one of the plurality of insulating layers constituting the first insulating portion 110, the second insulating portion 120, and the third insulating portion 130. The through hole 150 is arranged to pass through at least one of the plurality of insulating layers. The through hole 150 may pass through only one of the plurality of insulating layers. Alternatively, the through hole 150 may be formed while passing through at least two of the plurality of insulating layers together. Therefore, the through hole 150 electrically connects the circuit patterns arranged on the surfaces of different insulating layers to each other.

[0093] The via hole 150 may be formed by filling the inside of a via hole (not shown) passing through at least one of the plurality of insulating layers with a conductive material.

[0094] When the through hole is formed by mechanical processing, methods such as milling, drilling and routing can be used, and when the through hole is formed by laser processing, UV or CO2 laser method can be used, and when the through hole is formed by chemical processing, drugs containing aminosilane, ketones, etc. can be used, so that the first insulating layer 110 can be opened.

[0095] On the other hand, laser processing is a cutting method that melts and evaporates a part of a material to form a desired shape by concentrating light energy on the surface. It can easily process complex shapes through computer programs and can process composite materials that are difficult to cut by other methods.

[0096] In addition, laser processing can have a cutting diameter of at least 0.005mm and has a wide range of advantages in possible thicknesses.

[0097] As the laser processing drill, YAG (yttrium aluminum garnet) laser, CO2 laser or ultraviolet (UV) laser is preferably used. YAG laser is a laser that can process both the copper foil layer and the insulating layer, while CO2 laser is a laser that can only process the insulating layer.

[0098] When forming the through hole, the through hole 150 is formed by filling the inside of the through hole with a conductive material. The metal material forming the through hole 150 may be any one selected from copper (Cu), silver (Ag), tin (Sn), gold (Au), nickel (Ni), and palladium (Pd), and the conductive material may be filled using any one of chemical plating, electrolytic plating, screen printing, sputtering, evaporation, inkjet, and dispensing, or a combination thereof.

[0099] The first pad 160 is disposed on the uppermost insulating layer among the plurality of insulating layers (specifically, the sixth insulating layer 122 constituting the second insulating portion 120 ), and the second pad 180 is disposed under the lowermost insulating layer among the plurality of insulating layers (specifically, the eighth insulating layer 132 constituting the third insulating portion 130 ).

[0100] In other words, the first pad 160 is disposed on the uppermost insulating layer in the plurality of insulating layers on which the electronic component 300 is disposed. A plurality of first pads 160 may be formed on the uppermost insulating layer. In addition, a portion of the first pad 160 may be used as a pattern for signal transmission, while another portion may be used as an internal wire electrically connected to the electronic component 300 by a wire or the like. In other words, the first pad 160 may include a wire bonding pad for wire bonding.

[0101] In addition, the second pad 180 is disposed below the lowest insulating layer to which the external substrate (not shown) is to be attached among the plurality of insulating layers. Like the first pad 160, a portion of the second pad 180 is also used as a pattern for signal transmission, while another portion of the second pad 180 is an external wire on which an adhesive member (not shown) is disposed for attaching the external substrate. In other words, the second pad 180 may include a welding pad for welding purposes.

[0102] In addition, the first upper metal layer 170 is disposed on the first pad 160, and the second upper metal layer 190 is disposed under the second pad 180. The first and second upper metal layers 170 and 190 are respectively formed of the same material, and enhance wire bonding or welding characteristics while protecting the first and second pads 160 and 180.

[0103] To this end, the first upper metal layer 170 and the second upper metal layer 190 are formed of a metal including gold (Au). Preferably, the first upper metal layer 170 and the second upper metal layer 190 may include only pure gold (with a purity of 99% or more), and alternatively, may be formed of an alloy containing gold (Au). When the first upper metal layer 170 and the second upper metal layer 190 are formed of an alloy containing gold, the alloy may be formed of a gold alloy containing cobalt.

[0104] The solder paste 200 is disposed on the uppermost insulating layer of the plurality of insulating layers. The solder paste is an adhesive for fixing the electronic component 300 attached to the insulating substrate 100. Therefore, the solder paste 200 may also be referred to as an adhesive. The adhesive may be a conductive adhesive, or alternatively may be a non-conductive adhesive. That is, the circuit board 100 may be a board to which the electronic component 300 is attached by a wire bonding method, and therefore, the terminals (not shown) of the electronic component 300 may not be disposed on the adhesive. In addition, the adhesive may not be electrically connected to the electronic component 300. Therefore, the adhesive may use a non-conductive adhesive, or alternatively, a conductive adhesive may be used.

[0105] Conductive adhesives are roughly divided into anisotropic conductive adhesives and isotropic conductive adhesives, and are mainly composed of conductive particles such as Ni, Au / polymer, or Ag, and thermosetting, thermoplastic, or hybrid insulating resins that mix the properties of both.

[0106] Furthermore, the non-conductive adhesive may be a polymer adhesive, preferably a non-conductive polymer adhesive including a thermosetting resin, a thermoplastic resin, a filler, a curing agent, and a curing accelerator.

[0107] In addition, a first protective layer SR1 exposing at least a portion of a surface of the first upper metal layer 170 is disposed on the uppermost insulating layer. The first protective layer SR1 is disposed to protect the surface of the uppermost insulating layer, and, for example, it may be a solder resist.

[0108] In addition, the solder paste 200 is disposed on the first upper metal layer 170 , and thus, the first pad 160 and the electronic component 300 may be electrically connected to each other.

[0109] Here, the electronic component 300 may include both devices and chips. Devices may be divided into active devices and passive devices, and active devices are devices that actively utilize nonlinear parts, and passive devices refer to devices that do not use nonlinear characteristics even if both linear and nonlinear characteristics exist. In addition, passive devices may include transistors, IC semiconductor chips, etc., and passive devices may include capacitors, resistors, inductors, etc. Passive devices are mounted on a common printed circuit board to increase the signal processing speed of a semiconductor chip as an active device, or to perform a filtering function.

[0110] Therefore, the electronic component 300 may include all semiconductor chips, light emitting diode chips, and other driving chips.

[0111] A resin mold may be formed on the uppermost insulating layer, and thus, the electronic component 300 and the first upper metal layer 170 may be protected by the resin mold.

[0112] Meanwhile, the second protective layer SR2 is disposed under the lowermost insulating layer among the plurality of insulating layers. The second protective layer SR2 has an opening exposing the surface of the second upper metal layer 190. The second protective layer SR2 may be formed of a solder resist.

[0113] As described above, the buffer layer may be disposed on at least one surface of the insulating layer or the circuit pattern 140 .

[0114] In detail, the buffer layer 400 may be disposed between the insulating layer and the circuit pattern 140 in a region where the insulating layer and the circuit pattern 140 overlap.

[0115] The buffer layer 400 may be a surface treatment layer processed on the surface of the insulating layer. The buffer layer 400 may be a surface treatment layer processed on the surface of the circuit pattern 140.

[0116] The buffer layer 400 may be an intermediate layer disposed between the insulating layer and the circuit pattern. The buffer layer 400 may be a coating disposed between the insulating layer and the circuit pattern. The buffer layer 400 may be a functional layer that improves adhesion between the insulating layer and the circuit pattern, that is, an adhesion enhancing layer.

[0117] Figures 2 to 5 4 is a view for explaining the position and arrangement relationship of the buffer layer 400. Hereinafter, the position and arrangement relationship of the buffer layer 400 disposed on the insulating layer constituting the first insulating portion 110 among the plurality of insulating portions will be described. However, the buffer layer 400 may also be disposed on the insulating layers constituting the second insulating portion 120 and the third insulating portion 130 to correspond to the position and arrangement relationship described below.

[0118] refer to Figure 2 , the buffer layer 400 may be disposed on the surface of the circuit pattern. For example, the buffer layer 400 may be disposed on the upper surface and the lower surface of the circuit pattern. That is, the buffer layer 400 may be disposed on the surface of the circuit pattern that contacts or faces the insulating layer.

[0119] Alternatively, refer to Figure 3 , the buffer layer 400 may be disposed on the surface of the circuit pattern. For example, the buffer layer 400 may be disposed on the upper surface, the lower surface, and both sides of the circuit pattern. That is, the buffer layer 400 may be disposed to surround the entire surface of the circuit pattern.

[0120] Alternatively, refer to Figure 4 , the buffer layer 400 may be disposed on the surface of the insulating layer. For example, the buffer layer 400 may be disposed on the upper surface and the lower surface of the insulating layer. That is, the buffer layer 400 may be disposed on the surface of the insulating layer that contacts or faces the circuit pattern 140. That is, the buffer layer 400 may be disposed on the entire surface of the insulating layer on which the circuit pattern 140 is disposed.

[0121] Alternatively, refer to Figure 5 , the buffer layer 400 may be disposed on the surface of the insulating layer. For example, the buffer layer 400 may be disposed on the upper surface and the lower surface of the insulating layer. That is, the buffer layer 400 may be disposed on the surface of the insulating layer contacting or facing the circuit pattern 140. That is, the buffer layer 400 may be disposed only in the region where the circuit pattern 140 is disposed on the surface of the insulating layer where the circuit pattern 140 is disposed.

[0122] That is, the buffer layer 400 may be disposed between the insulating layer and the circuit pattern 140. In detail, the buffer layer 400 may be disposed between the insulating layer and the circuit pattern 140, and the buffer layer 400 may be coupled to one surface of the insulating layer and one surface of the circuit pattern 140. That is, the end group of the buffer layer and the end group of the insulating layer, and the end group of the buffer layer and the end group of the circuit pattern may be chemically bonded.

[0123] The buffer layer 400 may be formed to have a constant thickness. In detail, the buffer layer 400 may be formed as a thin film. In detail, the buffer layer 400 may be formed to have a thickness of 500 nm (nanometer) or less. In more detail, the buffer layer 400 may be formed to have a thickness of 5 nm to 500 nm.

[0124] When the thickness of the buffer layer 400 is formed to be 5 nm or less, the thickness of the buffer layer is too thin to fully ensure the adhesion between the insulating layer and the circuit pattern, and when the thickness of the buffer layer is formed to exceed 500 nm, the effect of improving the adhesion according to the thickness is negligible, the overall thickness of the circuit board may increase, and the dielectric constant of the insulating layer may increase, so that the transmission loss of the circuit board in high-frequency applications may increase.

[0125] The buffer layer 400 may include a plurality of elements. The plurality of elements included in the buffer layer 400 are combined with each other in the buffer layer and included in the form of molecules or ions, and the molecules, molecules, and ions may be chemically bonded to each other to form the buffer layer.

[0126] The buffer layer 400 may include at least one of carbon, nitrogen, oxygen, silicon, sulfur, and metal elements. Specifically, the buffer layer 400 may include all of carbon, nitrogen, oxygen, silicon, sulfur, and metal elements.

[0127] The carbon element, the nitrogen element, the oxygen element, the silicon element, the sulfur element, and the metal element may exist in a molecular form by being bonded to each other in the buffer layer, or may exist alone in an ion form.

[0128] Among the plurality of elements, oxygen, carbon, and nitrogen may be associated with a functional group of the buffer layer coupled to the insulating layer. That is, a functional group formed of molecules including oxygen, carbon, nitrogen atoms, etc. may be chemically bonded to the insulating layer.

[0129] In addition, carbon, nitrogen, silicon and sulfur among the plurality of elements may be associated with a functional group of the buffer layer coupled to the circuit pattern, that is, a functional group formed by molecules including carbon, nitrogen, silicon, sulfur, etc. may be chemically bonded to the circuit pattern.

[0130] In addition, the metal element may bond molecules formed of carbon, nitrogen, oxygen, silicon, and sulfur to each other. That is, molecules formed of carbon, nitrogen, oxygen, silicon, and sulfur may be chemically bonded by the metal element to form a buffer layer. That is, the metal element may be provided between the molecules to serve as a medium for chemically bonding the molecules.

[0131] To this end, carbon, nitrogen, oxygen, silicon, sulfur and metal elements may be contained in a constant mass ratio. Specifically, the metal element among the plurality of elements may be the most contained element compared to other elements, and carbon, nitrogen, oxygen, silicon and sulfur may all be contained in a constant mass ratio based on the metal element.

[0132] Specifically, the ratio of carbon element to metal element ((carbon element / copper element)*100) may be 5 to 7.

[0133] In addition, the ratio of the nitrogen element to the metal element ((nitrogen element / copper element)*100) may be 1.5 to 7.

[0134] In addition, the ratio of the oxygen element to the metal element ((oxygen element / copper element)*100) may be 1.1 to 1.9.

[0135] In addition, the ratio of silicon element to metal element ((silicon element / copper element)*100) may be 0.5 to 0.9.

[0136] In addition, the ratio of sulfur element to metal element ((sulfur element / copper element)*100) may be 0.5 to 1.5.

[0137] The ratio of carbon, nitrogen, oxygen, silicon and sulfur to metal elements can be related to the bonding strength of the insulating layer or circuit board.

[0138] In detail, when the ratio of the carbon element to the metal element ((carbon element / copper element)*100) exceeds the range of 5 to 7, the bonding force between the buffer layer and the circuit board or between the buffer layer and the insulating layer may be weakened.

[0139] In addition, when the ratio of nitrogen element to metal element ((nitrogen element / copper element)*100) exceeds the range of 1.5 to 7, the bonding force between the buffer layer and the circuit board or between the buffer layer and the insulating layer may be weakened.

[0140] In addition, when the ratio of the oxygen element to the metal element ((oxygen element / copper element)*100) exceeds the range of 1.1 to 1.9, the bonding force between the buffer layer and the insulating layer may be weakened.

[0141] In addition, when the ratio of silicon element to metal element ((silicon element / copper element)*100) exceeds the range of 0.5 to 0.9, the bonding force between the buffer layer and the circuit board may be weakened.

[0142] In addition, when the ratio of sulfur element to metal element ((sulfur element / copper element)*100) exceeds the range of 0.5 to 1.5, the bonding force between the buffer layer and the circuit board may be weakened.

[0143] Meanwhile, carbon elements, nitrogen elements, oxygen elements, silicon elements, sulfur elements, and metal elements exist in the buffer layer in the form of molecules or ions, and the molecules and ions may be connected to each other through bonding.

[0144] In detail, the buffer layer 400 may include molecules and metal ions formed of carbon, nitrogen, oxygen, silicon, sulfur and metal elements. The molecules included in the buffer layer 400 may include at least two types of molecules, depending on the size of the molecules or the size of the molecular weight. In detail, the molecules may include macromolecules and single molecules.

[0145] Macromolecules, single molecules, and metal ions may be formed into a structure in which they are bonded to each other in the buffer layer.

[0146] In detail, macromolecules, single molecules, and metal ions may be chemically bonded through covalent bonds and coordination bonds in the buffer layer to form a structure in which they are connected to each other.

[0147] The metal ion can connect a macromolecule, a single molecule, or connect a macromolecule and a single molecule to each other. In detail, the macromolecule, the single molecule, or the macromolecule and the single molecule are coordinately bonded to the metal ion, and therefore, the macromolecule, the single molecule, or the macromolecule and the single molecule can be chemically bonded.

[0148] The metal ions may include the same material as the circuit pattern. Alternatively, the metal ions may include a material different from the circuit pattern. For example, when the circuit pattern includes copper, the metal ions may include copper or a metal other than copper.

[0149] In detail, the metal ions can be formed by the circuit pattern. In detail, the metal ions can be formed by ionizing the circuit pattern including the metal using a separate oxidant. Therefore, the ionized metal ions can form a buffer layer by coordinating the macromolecules and single molecules in the buffer layer to connect the molecules to each other.

[0150] Alternatively, metal ions may be added separately when forming the buffer layer, and the metal ions may form the buffer layer by coordinating the macromolecules and single molecules in the buffer layer to connect the molecules to each other. In this case, the separately added metal ions may be the same as or different from the metal of the circuit pattern.

[0151] The macromolecule and the single molecule may include at least one of carbon, nitrogen, oxygen, silicon, and sulfur.

[0152] That is, the macromolecule and the single molecule may be a molecule including at least one of a carbon element, a nitrogen element, an oxygen element, a silicon element, and a sulfur element.

[0153] In detail, the macromolecule may include a molecule including carbon and nitrogen. In detail, the macromolecule may include an azole group including carbon and nitrogen.

[0154] In addition, the macromolecule may include a molecule including a silicon element. In detail, the macromolecule may include a silane group including a silicon element.

[0155] In addition, the single molecule may include carbon, nitrogen and sulfur. That is, the single molecule may be a molecule including carbon, nitrogen and sulfur. For example, the single molecule may include an SCN group to which a thiocyanate group (-SCN) is connected.

[0156] refer to Figure 3 , the buffer layer 400 may include a plurality of functional groups. In detail, the buffer layer 400 may include a first functional group chemically bonded to the insulating layer and a second functional group chemically bonded to the circuit pattern 140 .

[0157] That is, the macromolecule and the single molecule may include multiple terminal groups, ie, functional groups, chemically bonded to the insulating layer and the circuit pattern. Through these functional groups, the insulating layer and the circuit pattern are chemically tightly coupled through the buffer layer, thereby improving the adhesion between the insulating layer and the circuit pattern.

[0158] The first functional group and the second functional group may be defined as an end group of the buffer layer connected to one of a macromolecule, a single atom or a metal atom.

[0159] The first functional group may be covalently bonded to the insulating layer. The first functional group may include a functional group covalently bonded to the insulating layer. In detail, the first functional group may include a hydroxyl group (-OH) and an N group of an azole group.

[0160] In addition, the second functional group may be coupled to the circuit pattern 140 through coordination bonding. The second functional group may include a functional group coordinated with the circuit pattern 140. In detail, the second functional group may include a Si group of a silane group and a thiocyanate group (—SCN).

[0161] The first functional group and the second functional group included in the buffer layer may be chemically bonded to the insulating layer and the circuit pattern, respectively. Therefore, by providing the buffer layer between the insulating layer and the circuit pattern, the adhesion between the insulating layer and the circuit pattern, which are different materials, may be improved.

[0162] Meanwhile, as described above, the insulating layers constituting the second insulating part 120 and the third insulating part 130 may include a material capable of ensuring mechanical / chemical reliability with a low dielectric constant.

[0163] In detail, the insulating layers 121, 122, 131, and 132 may have a dielectric constant Dk of 3.0 or less. In more detail, the insulating layers 121, 122, 131, and 132 may have a dielectric constant of 2.03 to 2.7. Therefore, the insulating layer may have a low dielectric constant, and when the insulating layer is applied to a circuit board used at a high frequency, the transmission loss according to the dielectric constant of the insulating layer may be reduced.

[0164] In addition, the insulating layers 121, 122, 131, and 132 may have a thermal expansion coefficient of 50 ppm / °C or less. In detail, the insulating layers 121, 122, 131, and 132 may have a thermal expansion coefficient of 15 ppm / °C to 50 ppm / °C.

[0165] Therefore, the insulating layers 121 , 122 , 131 , and 132 may have a low thermal expansion coefficient, thereby minimizing cracks in the insulating layers due to temperature changes.

[0166] To this end, the insulating layers 121, 122, 131, and 132 may be formed of two materials. In detail, the insulating layers 121, 122, 131, and 132 may include a material in which two compounds are mixed. In detail, the insulating layers 121, 122, 131, and 132 may include a first compound and a second compound.

[0167] The first material and the second material may be included in a specific ratio range. In detail, the first material and the second material may be included in a ratio of 4:6 to 6:4.

[0168] In addition, the insulating layers 121, 122, 131, and 132 may further include inorganic particles. In detail, the insulating layers 121, 122, 131, and 132 may further include inorganic particles such as silicon dioxide (SiO2). Based on the entire insulating layers 121, 122, 131, and 132, the content of the inorganic particles may be included in about 55wt% to about 70wt%.

[0169] When the ratio of the inorganic particles exceeds the above range, the thermal expansion coefficient or the dielectric constant may be increased by the inorganic particles, and thus the properties of the insulating layer may be deteriorated.

[0170] In addition, the first material and the second material may be chemically non-bonded to each other in the insulating layers 121, 122, 131, and 132. However, the embodiment is not limited thereto, and the first material including the first compound and the second material including the second compound may be chemically bonded directly or through a separate linking group.

[0171] The first material may include a material having insulating properties. In addition, due to high impact strength, the first material may have improved mechanical properties. In detail, the first material may include a resin material. For example, the first material may include a first compound including polyphenylene ether (PPE).

[0172] The first material may include a plurality of first compounds, and the first compounds may be formed by chemically bonding to each other. In detail, the first compounds may be linearly connected to each other by covalent bonds (ie, pi-pi bonds (π-π)).

[0173] That is, the first compounds may be formed by chemically bonding to each other such that the first material has a molecular weight of about 300 to 500.

[0174] In addition, the second material may include a second compound. In detail, the second material may be formed by chemically bonding a plurality of second compounds to each other.

[0175] The second compound may include a material having a low dielectric constant and a thermal expansion coefficient. In addition, the second compound may include a material having improved mechanical strength.

[0176] The second compound may include tricyclodecane and an end group connected to the tricyclodecane. The end group connected to the tricyclodecane may include various materials, wherein the second compound may be connected to each other by a carbon double bond (C=C bond). In detail, the end group connected to the tricyclodecane may include an acrylate group, an epoxy group, a carboxyl group, a hydroxyl group and an isocyanate group.

[0177] The second compound may be linked to each other between the terminal groups connected to the tricyclodecane. Specifically, the second compound is cross-linked through carbon double bonds (C=C bonds) between the terminal groups to form a network structure.

[0178] Specifically, refer to Figure 7 , the second compound may be cross-linked to form a network structure. That is, the second compound may be an aggregate of bonds having a plurality of network structures.

[0179] Therefore, the second material formed of the second compound may have a low dielectric constant and a low thermal expansion coefficient according to material properties, and may have improved mechanical strength due to a network structure.

[0180] Figure 8 2 is a diagram for explaining the arrangement of the first material and the second material constituting the insulating layer.

[0181] The first material and the second material may form a single phase in the insulating layer. Figure 8 , the first material connected by the covalent bond of the first compound may be disposed inside the second material formed by the second compounds being cross-linked with each other to form a network structure.

[0182] In detail, the first compound may be disposed inside a network structure of the second material formed by chemically bonding the second compound to prevent the first material from being separated from the second material.

[0183] That is, in the insulating layer, the first material and the second material are not arranged to be phase-separated in the insulating layer, and can be formed into a single-phase structure. Therefore, due to the material properties of the first material and the second material, the first material and the second material have a low dielectric constant and a low thermal expansion coefficient, so they can be formed into a single phase and thus have high mechanical strength.

[0184] On the other hand, in the first embodiment, the first insulating part 110 is composed of an insulating layer of PPG containing glass fiber, and the second insulating part 120 and the third insulating part 130 are made of RCC having a low dielectric constant and a low thermal expansion coefficient as described above.

[0185] Alternatively, the circuit board may be composed only of RCC having a low dielectric constant and a low coefficient of thermal expansion as described above.

[0186] Fig. 9 is a view showing a cross-sectional view of a circuit board according to a second embodiment.

[0187] refer to Fig. 9 The circuit board 1000A may include an insulating substrate 100A, a first pad 160 , a first upper metal layer 170 , a second pad 180 , a second upper metal layer 190 , a first protective layer SR1 , a second protective layer SR2 , a solder paste 200 , and an electronic component 300 .

[0188] The insulating substrate 100A may include an insulating portion 110A including a plurality of insulating layers.

[0189] That is, the insulating part 110A may include the first to eighth insulating layers 111a, 112a, 113a, 114a, 115a, 116a, 117a, 118a and 119a from the bottom. However, in this embodiment, the insulating part 110A is shown as having an 8-layer structure, but the present invention is not limited thereto, and the number of insulating layers may be increased or decreased.

[0190] In other words, the insulating portion in the first embodiment is constituted by the first insulating portion of the PPG, the second insulating portion of the RCC, and the third insulating portion.

[0191] Alternatively, the insulating portion in the second embodiment may be composed of only RCC.

[0192] At this time, as described above, the insulating part 110A in the second embodiment has a low dielectric constant and a low thermal expansion coefficient, and therefore, as in the first embodiment, rigidity can be ensured without PPG, and even if it is composed only of RCC, the reliability of the rigidity of the circuit board is not affected.

[0193] Fig.10 is a view showing a cross-sectional view of a circuit board according to a third embodiment.

[0194] refer to Fig.10 The circuit board 1000B may include an insulating substrate 100B, a first pad 160 , a first upper metal layer 170 , a second pad 180 , a second upper metal layer 190 , a first protective layer SR1 , a second protective layer SR2 , a solder paste 200 , and an electronic component 300 .

[0195] The insulating substrate 100B may include an insulating portion 110B including a plurality of insulating layers.

[0196] That is, the insulating part 110B may include the first to eighth insulating layers 111b, 112b, 113b, 114b, 115b, 116b, 117b, 118b and 119b from the bottom. However, in this embodiment, the insulating part 110B is shown as having an 8-layer structure, but the present invention is not limited thereto, and the number of insulating layers may be increased or decreased.

[0197] In other words, the insulating portion in the first embodiment is constituted by the first insulating portion of the PPG, the second insulating portion of the RCC, and the third insulating portion.

[0198] Alternatively, the insulating portion in the third embodiment may be composed of only RCC.

[0199] At this time, as described above, the insulating part 110B in the third embodiment has a low dielectric constant and a low thermal expansion coefficient, and therefore, as in the first embodiment, rigidity can be ensured without PPG, and therefore even if it is composed only of RCC, the reliability of the rigidity of the circuit board is not affected.

[0200] Here, the circuit pattern in the embodiment has low roughness, and the insulating layer constituting the insulating portion 110B has a low dielectric constant and a low thermal expansion coefficient.

[0201] Therefore, the thickness H2 of each of the first to eighth insulating layers 111 b , 112 b , 113 b , 114 b , 115 b , 116 b , 117 b , 118 b , and 119 b constituting the insulating part 110B in the third embodiment may be smaller than the thickness H1 of the circuit pattern 140 .

[0202] For example, the thickness H2 of the circuit pattern 140 may have a thickness of 12 μm±2 μm. That is, the thickness of each insulating layer constituting the third insulating part 130 may be in the range of 10 μm to 14 μm.

[0203] In addition, the thickness H2 of each of the first to eighth insulating layers 111b, 112b, 113b, 114b, 115b, 116b, 117b, 118b, and 119b constituting the insulating portion 110B is 8 μm±2 μm. That is, the thickness of each insulating layer constituting the third insulating portion 130 may be in the range of 6 μm to 10 μm.

[0204] Therefore, the thickness of the through hole 150 provided in the first to eighth insulating layers 111 b , 112 b , 113 b , 114 b , 115 b , 116 b , 117 b , 118 b , and 119 b constituting the insulating part 110B may be smaller than the thickness of the circuit pattern 140 .

[0205] At the same time, the insulating layers constituting the second insulating part 120 and the third insulating part 130 in the first embodiment are also composed of the same insulating layers as those in the third embodiment, and therefore, in the first embodiment, the thickness of each of the insulating layers constituting the second insulating part 120 and the third insulating part 130 can be smaller than the thickness of the circuit pattern.

[0206] Hereinafter, the present invention will be described in more detail by measuring the dielectric constants of the embodiments and comparative examples according to which the insulating parts 110A and 110B can be constituted as in the second and third embodiments. These embodiments are presented only as examples in order to explain the present invention in more detail. Therefore, the present invention is not limited to these examples.

[0207] Example 1

[0208] The copper layer is formed on the insulating layer. At this time, after coating a coating containing carbon, nitrogen, oxygen, silicon, sulfur and metal elements on the surface of the circuit layer in contact with the insulating layer, the copper layer and the insulating layer are adhered together.

[0209] The copper layer is then patterned to form a circuit pattern, thereby manufacturing a circuit board.

[0210] In this case, the buffer layer includes a first functional group including a hydroxyl group (—OH) and an N group of an oxazole group, and a second functional group including a Si group of a silane group and a thiocyanate group (—SCN).

[0211] Next, the adhesion and reliability were evaluated based on the roughness size of the circuit pattern.

[0212] Comparative Example 1

[0213] The circuit pattern was formed in the same manner as in the embodiment, except that the copper layer was formed by directly bonding the copper layer on the insulating layer without forming a coating on the copper layer, and the circuit pattern was formed by patterning the copper layer. And, after the circuit pattern was formed, the adhesion and reliability were evaluated according to the roughness of the circuit pattern.

[0214] Adhesion / Reliability Measurement Methods

[0215] In order to evaluate the adhesion of the circuit patterns according to the embodiment and the comparative example, a UTM 90° peel value was measured using a UTM device.

[0216] Furthermore, when the peel strength (kgf / cm) of the circuit pattern was less than 0.6, the reliability evaluation was evaluated by MG.

[0217]

Table 1

[0218]

[0219]

Table 2

[0220]

[0221] Referring to Table 1 and Table 2, it can be seen that the circuit board according to Example 1 has improved reliability compared to the circuit board according to Comparative Example 1. In detail, the circuit board according to Example 1 forms a circuit pattern in which a coating is applied on an insulating layer. Therefore, since the coating is chemically tightly bonded to the insulating layer and the circuit pattern, the peel strength of the circuit pattern can be increased, and therefore it can be seen that the adhesion of the circuit pattern and the reliability of the circuit board can be improved. That is, it can be seen that the circuit board according to Example 1 can have adhesion that can ensure the reliability of the circuit board even when the roughness of the circuit pattern is reduced. In detail, it can be seen that the circuit board according to Example 1 can have adhesion that can ensure the reliability of the circuit board even when the surface roughness of the circuit pattern is 0.5 or less or in the range of 0.1 to 0.5.

[0222] That is, the circuit board according to the first embodiment can reduce the illuminance of the circuit pattern when applied to high-frequency applications, and therefore, can reduce the transmission loss caused by the skin effect, and even in the case of low surface roughness, the reliability of the circuit pattern can be ensured by improving the adhesion of the coating to the circuit pattern.

[0223] On the other hand, in the case of the circuit board according to Comparative Example 1, the circuit pattern is directly formed on the insulating layer. Therefore, since the insulating layer and the circuit pattern are formed of different materials, it can be seen that the adhesion (ie, peel strength) of the circuit pattern is very low.

[0224] That is, it can be seen that, in the circuit board according to Comparative Example 1, reliability can be ensured only when the surface roughness of the circuit pattern increases, and when the circuit pattern has a low surface roughness, the reliability of the circuit board decreases.

[0225] Therefore, when the circuit board according to Comparative Example 1 is applied to high-frequency applications, it can be seen that the transmission loss caused by the skin effect increases due to the surface roughness of the circuit pattern.

[0226] Example 2

[0227] A copper layer is formed on the insulating layer.

[0228] The copper layer is then patterned to form a circuit pattern, thereby manufacturing a circuit board.

[0229] At this time, the insulation is formed by placing tricyclodecane diacrylate in which acrylate is linked with polyphenylene ether (PPE) and tricyclodecane in a toluene solvent, mixing at a temperature of about 100° C., and then adding an azo compound initiator and a peroxide initiator.

[0230] Then, the dielectric constant, reliability, and thermal expansion coefficient of the insulating layer were measured according to the weight ratio of the polyphenylene ether (A) and tricyclodecane diacrylate (B) by changing the frequency.

[0231]

Table 3

[0232]

[0233]

Table 4

[0234] The weight ratio of A to B Thermal expansion coefficient (ppm / ℃) 6:4 35 4:6 39

[0235]

Table 5

[0236] The weight ratio of A to B Reliability Assessment 8:2 NG (crack) 6:4 OK 4:6 OK 2:8 NG (crack)

[0237] Referring to Tables 3 to 5, when the ratio of polyphenylene ether (A) to tricyclodecane diacrylate (B) satisfies 4:6 to 6:4, the insulating layer according to the embodiment has a low dielectric constant and a thermal expansion coefficient, and it can be seen that the reliability is improved with the improvement of mechanical strength. On the other hand, when the insulating layer does not satisfy the ratio of polyphenylene ether (A) to tricyclodecane diacrylate (B), the mechanical strength may be reduced, and cracks may occur in the insulating layer, and it can be seen that the dielectric constant increases, making it unsuitable for use as an insulating layer of a high-frequency circuit board.

[0238] The circuit board according to the embodiment may include a buffer layer disposed between the insulating layer and the circuit pattern.

[0239] That is, in the circuit board according to the embodiment, the buffer layer may be formed on the surface of the circuit pattern, or the buffer layer may be formed on the insulating layer.

[0240] A buffer layer may be disposed between the insulating layer and the circuit pattern to improve adhesion between the insulating layer and the circuit pattern.

[0241] That is, the insulating layer and the circuit pattern are heterogeneous materials including a resin material and a metal, respectively, and when the circuit pattern is formed on the insulating layer, there is a problem in that adhesion is reduced.

[0242] Therefore, by providing a buffer layer chemically bonded to the insulating layer and the circuit pattern between the insulating layer and the circuit pattern, adhesion between the insulating layer and the circuit pattern may be improved.

[0243] That is, the buffer layer includes a plurality of functional groups coupled to the insulating layer and the circuit pattern, and the functional groups are chemically bonded to the insulating layer and the circuit pattern through covalent bonds or coordination bonds, so that adhesion between the insulating layer and the circuit pattern can be improved.

[0244] Therefore, even when the surface roughness of the insulating layer is reduced, adhesion reliability between the insulating layer and the circuit pattern can be ensured.

[0245] Therefore, even when the circuit board according to the embodiment is used for high-frequency applications, the transmission loss of the high-frequency signal can be reduced by maintaining the surface roughness of the circuit pattern low. Even if the surface roughness of the circuit pattern is kept low, the adhesion between the insulating layer and the circuit pattern can be ensured by the buffer layer, thereby ensuring the overall reliability of the circuit pattern.

[0246] Furthermore, the circuit board according to the embodiment may include an insulating layer having improved strength, a low dielectric constant, and a low thermal expansion coefficient.

[0247] In detail, the insulating layer includes a first material having a low dielectric constant and improved strength and a second material, and since the first material is formed in the insulating layer to be arranged inside the mesh structure of the second material, phase separation of the first material and the second material can be prevented. Therefore, the insulating layer can form the first material and the second material into a single phase, thereby improving the strength of the insulating layer.

[0248] That is, by increasing the free volume (i.e., molecular movement) of the second material having a network structure through cross-linking, the polymer chains having a network structure can be structured so that they are not tightly arranged, and since the first material is partially arranged inside the network structure, the first material and the second material can be formed as a single phase inside the insulating layer.

[0249] Therefore, when the circuit board according to the embodiment is used in high-frequency applications, the transmission loss of the high-frequency signal can be reduced by reducing the dielectric constant of the insulating layer, and the overall reliability of the circuit board can be ensured by improving the thermal expansion coefficient and mechanical strength of the insulating layer.

[0250] In addition, since the circuit board according to the embodiment includes an insulating layer having a low dielectric constant and a low thermal window coefficient, it can replace the existing insulating layer including glass fiber. Specifically, the circuit board according to the embodiment can remove the glass fiber included in the insulating layer. Specifically, in the circuit board according to the embodiment, by using the resin and filler constituting RCC (resin coated copper), the dielectric constant and thermal expansion coefficient of the insulating layer can be easily adjusted, and therefore, by configuring the insulating layer as a traditional RCC that does not include glass fiber, the overall thickness of the printed circuit board can be reduced. In addition, since the circuit board according to the embodiment is composed of an insulating layer having a low thermal expansion coefficient, not only can the core layer be removed to ensure strength, but also the thickness of the insulating layer can be reduced, and therefore, an insulating layer having a thickness less than the thickness of the circuit pattern can be provided.

Claims

1. A circuit board, comprising: a first insulating layer, the first insulating layer comprising first to fourth layers stacked in a vertical direction; a first circuit pattern disposed between a first layer and a second layer of the first insulating layer; a second circuit pattern disposed between the second layer and the third layer of the first insulating layer; a third circuit pattern, the third circuit pattern being disposed between the third layer and the fourth layer of the first insulating layer; a first conductive via disposed in a first layer of the first insulating layer and connected to the first circuit pattern; a second conductive via disposed in the second layer of the first insulating layer and connecting the first circuit pattern and the second circuit pattern; a third conductive via disposed in a third layer of the first insulating layer and connected between the second circuit pattern and the third circuit pattern; a fourth conductive via disposed in a fourth layer of the first insulating layer and connected to the third circuit pattern; a second insulating layer, the second insulating layer being disposed on the first insulating layer; a third insulating layer, the third insulating layer being disposed below the first insulating layer; a fourth circuit pattern, the fourth circuit pattern being disposed on the second insulating layer, a fifth circuit pattern, the fifth circuit pattern being disposed below the third insulating layer, a fifth conductive via, the fifth conductive via passing through the second insulating layer; as well as a sixth conductive via, the sixth conductive via passing through the third insulating layer; wherein each of the first to fourth layers of the first insulating layer is provided with an insulating material including glass fiber, wherein each of the second insulating layer and the third insulating layer is provided with an insulating material that does not include glass fibers, wherein each thickness of the second insulating layer and the third insulating layer is smaller than each thickness of the first to fourth layers of the first insulating layer, wherein the first to third circuit patterns are buried in the first insulating layer, wherein each of the first conductive via and the second conductive via has a first slope in which the width gradually increases from the upper surface to the lower surface, Each of the third conductive via and the fourth conductive via has a second slope, and a width of the second slope gradually decreases from the upper surface to the lower surface. wherein the first slopes of the first conductive via and the second conductive via and the second slopes of the third conductive via and the fourth conductive via are inclined in opposite directions relative to the second circuit pattern, wherein the thickness of each of the first to fourth conductive vias is greater than the thickness of each of the first to third circuit patterns; wherein the thickness of each of the fourth circuit pattern and the fifth circuit pattern is 10 μm to 14 μm, wherein the thickness of the fifth conductive via is smaller than the thickness of each of the first to fifth circuit patterns; and Wherein, the thickness of the sixth conductive via is smaller than the thickness of each of the first to fifth circuit patterns.

2. The circuit board according to claim 1, wherein: The second insulating layer is composed of a plurality of layers on the first insulating layer, and The third insulating layer is composed of a plurality of layers below the lower surface of the first insulating layer.

3. The circuit board according to claim 1, wherein: The thickness of each of the first to fourth layers of the first insulating layer is greater than the thickness of each of the first to third circuit patterns; wherein the thickness of the second insulating layer is smaller than the thickness of the fourth circuit pattern, and Wherein, the thickness of the third insulating layer is smaller than the thickness of the fifth circuit pattern.

4. The circuit board according to claim 3, wherein: The second insulating layer has a thickness smaller than a thickness of each of the first to fifth circuit patterns.

5. The circuit board according to claim 4, wherein: The third insulating layer has a thickness smaller than a thickness of each of the first to fifth circuit patterns.

6. The circuit board according to claim 1, wherein: Each of the second insulating layer and the third insulating layer includes: a first compound including polyphenylene ether (PPE); and a second compound including tricyclodecane and an end group connected to the tricyclodecane, and Wherein, the weight ratio of the first compound to the second compound is 4:6 to 6:

4.

7. The circuit board according to claim 6, wherein: The terminal group includes at least one of an acrylate group, an epoxy group, a carboxyl group, a hydroxyl group, and an isocyanate group.

8. The circuit board according to claim 6, wherein: The first compound and the second compound are not chemically bonded.

9. The circuit board according to claim 4, wherein: The thermal expansion coefficient and the dielectric constant of each of the second insulating layer and the third insulating layer are smaller than the thermal expansion coefficient and the dielectric constant of each of the first layer to the fourth layer of the first insulating layer, and The dielectric constant of each of the second insulating layer and the third insulating layer is 2.03 to 2.

7.

10. The circuit board according to claim 1, further comprising: a buffer layer provided to cover each of the first to third circuit patterns, and The buffer layer covers an upper surface, a side surface, and a lower surface of each of the first to third circuit patterns.

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