Circuit board

Abstract

The circuit board according to the embodiment includes an insulating part including a plurality of insulating layers, circuit patterns disposed on the surfaces of the plurality of insulating layers, and vias disposed within the plurality of insulating layers and connecting the circuit patterns disposed on different layers, each of the plurality of insulating layers being made of RCC (resin coated copper), and each of the plurality of insulating layers having a dielectric constant of 2.03 to 2.7.

Description

Technical Field

[0001] Examples relate to a circuit board, and more particularly to a circuit board including an insulating layer having a low dielectric constant and a low coefficient of thermal expansion.

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 substrate immediately before mounting electronic components. That is, in order to densely mount many different types of electronic elements on a flat plate, a circuit board is meant in which the mounting positions of the components are determined and a circuit pattern for connecting the components is printed and fixed on the surface of the flat plate.

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

[0004] At this time, the surface treatment method used varies depending on its application. For example, the applications include soldering applications, wire bonding applications, and connector applications.

[0005] The components mounted on the printed circuit board can transmit signals generated by the components through the circuit patterns connected to each component.

[0006] On the other hand, with the recent high functionality of portable electronic devices and the like, in order to perform high-speed processing of a large amount of information, the frequency of signals has been increasing, and a circuit pattern of a printed circuit board suitable for high-frequency applications is required.

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

[0008] The transmission loss of the circuit pattern on the printed circuit board mainly consists of conductor loss due to copper foil and dielectric loss due to the insulating resin substrate.

[0009] The conductor loss due to 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, reducing the surface roughness of the circuit pattern can prevent the reduction of transmission loss, but there is a problem that the adhesion between the circuit pattern and the insulating layer decreases.

[0011] In addition, for the reduction by the dielectric, a material with a low dielectric constant can be used as the insulating layer of the circuit board.

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

[0013] Specifically, for the ease of circuit pattern design and process, it should have isotropy of electrical properties, low reactivity with metal wiring materials, low ion transferability, sufficient mechanical strength to withstand processes such as chemical mechanical polishing (CMP), low moisture absorption rate to prevent peeling or increase in dielectric constant, heat resistance to withstand the processing temperature of the process, low thermal expansion coefficient to remove cracks due to temperature changes, adhesion to minimize various stresses and peeling that may occur at the interface with other substances, crack resistance, low stress, and low high-temperature gas generation, etc., and must meet various conditions.

[0014] Therefore, together with the above chemical and mechanical properties, a circuit board insulating layer for high-frequency applications with a low dielectric constant and improved adhesion between the insulating layer and the circuit pattern, and a circuit pattern with a small surface roughness are required. SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

[0015] In the embodiment, it is possible to achieve slimming of the circuit board.

[0016] Also, in the embodiment, a circuit board including an insulating layer having a low dielectric constant and a circuit pattern having a low signal loss is provided.

[0017] Also, in the implementation, a circuit board in which the insulating layer is formed only of RCC (Resin coated copper) having a low coefficient of thermal expansion can be provided.

[0018] Also, in the implementation, glass fibers contained in the insulating layer are removed so that the thickness of the circuit board can be reduced by the thickness corresponding to the glass fibers.

[0019] Also, in the implementation, a circuit board in which the thickness of the circuit pattern is larger than the thickness of the insulating layer can be provided.

[0020] In the proposed embodiment, the technical problems to be solved are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those having ordinary knowledge in the technical field to which the embodiment belongs from the following description.

Means for Solving the Problems

[0021] The circuit board according to the embodiment includes a first insulating portion including at least one insulating layer, a second insulating portion disposed above the first insulating portion and including at least one insulating layer, and a third insulating portion disposed below the first insulating portion and including at least one insulating layer. The insulating layer constituting the first insulating portion includes a prepreg containing glass fibers, and each insulating layer constituting the second and third insulating portions is formed of RCC (resin coated copper).

[0022] Further, the thickness of the insulating layer constituting the first insulating portion is greater than the thicknesses of the respective insulating layers constituting the second and third insulating portions.

[0023] Further, it includes circuit patterns disposed on the surfaces of the respective insulating layers of the first to third insulating portions. The thickness of the insulating layer constituting the first insulating portion is greater than the thickness of the circuit pattern, and the thicknesses of the insulating layers constituting the second and third insulating portions are smaller than the thickness of the circuit pattern.

[0024] Further, it includes vias disposed in at least one of the insulating layers constituting the first to third insulating portions. The thickness of the via disposed in the insulating layer constituting the first insulating portion is greater than the thickness of the circuit pattern, and the thicknesses of the vias disposed in the insulating layers constituting the second and third insulating portions are smaller than the thickness of the circuit pattern.

[0025] Further, each of the insulating layers constituting the second and third insulating portions includes a first compound containing polyphenyl ether (PPE) and a second compound containing tricyclodecane and a terminal group linked to the tricyclodecane. The weight ratio of the first compound to the second compound is 4:6 to 6:4.

[0026] Further, the terminal group includes at least one of an acrylate group, an epoxide group, a carboxyl group, a hydroxyl group, and an isocyanate group.

[0027] Further, the first compound and the second compound are chemically unbonded.

[0028] Further, the thermal expansion coefficients and dielectric constants of the respective insulating layers constituting the second and third insulating portions are smaller than the thermal expansion coefficients and dielectric constants of the insulating layer constituting the first insulating portion.

[0029] Further, the dielectric constant of each of the insulating layers constituting the second and third insulating portions is 2.03 to 2.7.

[0030] On the one hand, the circuit board according to the embodiment includes an insulating part including a plurality of insulating layers, a circuit pattern disposed on the surfaces of the plurality of insulating layers, and vias disposed in the plurality of insulating layers and connecting circuit patterns disposed in different layers from each other. Each of the plurality of insulating layers is made of RCC (resin coated copper), and the dielectric constant of the plurality of insulating layers is 2.03 to 2.7.

[0031] Also, the thickness of each of the plurality of insulating layers is smaller than the thickness of the circuit pattern.

[0032] Also, the thickness of the via is smaller than the thickness of the circuit pattern.

[0033] Also, each of the plurality of insulating layers includes a first substance and a second substance. The first substance includes a first compound that chemically bonds to each other, and the second substance includes a second compound that chemically bonds to each other. Each first compound includes polyphenil ether (PPE), and each second compound includes tricyclodecane and an end group linked to the tricyclodecane. The second compounds are bonded to each other through the end group, and the end group includes at least one of an acrylate group, an epoxide group, a carboxyl group, a hydroxyl group, and an isocyanate group.

Advantages of the Invention

[0034] The circuit board according to the embodiment can include a buffer layer disposed between the insulating layer and the circuit pattern.

[0035] That is, for the circuit board according to the embodiment, a buffer layer can be formed on the surface of the circuit pattern or a buffer layer can be formed on the insulating layer.

[0036] The buffer layer is disposed between the insulating layer and the circuit pattern, and can improve the adhesion between the insulating layer and the circuit pattern.

[0037] That is, the insulating layer and the circuit pattern are made of different materials including a resin material and a metal respectively, and there is a problem that the adhesive force decreases when the circuit pattern is formed on the insulating layer.

[0038] Therefore, a buffer layer that chemically bonds to the insulating layer and the circuit pattern respectively can be disposed between the insulating layer and the circuit pattern to improve the adhesion between the insulating layer and the circuit pattern.

[0039] That is, the buffer layer contains a plurality of functional groups that bond to the insulating layer and the circuit pattern, and the functional groups chemically bond to the insulating layer and the circuit pattern by covalent bonding or coordination bonding, thereby improving the adhesion between the insulating layer and the circuit pattern.

[0040] Thereby, even if the surface roughness of the insulating layer is reduced, the adhesion reliability between the insulating layer and the circuit pattern can be ensured.

[0041] Therefore, even when the circuit board according to the embodiment is used for high-frequency applications, the surface roughness of the circuit pattern can be kept low to reduce the transmission loss of high-frequency signals, and even if the surface roughness of the circuit pattern is kept low, the buffer layer can ensure the adhesion between the insulating layer and the circuit pattern, so the overall reliability of the circuit pattern can be ensured.

[0042] In addition, the circuit board according to the embodiment can have a low dielectric constant and a low coefficient of thermal expansion and include an insulating layer having improved strength.

[0043] Specifically, the insulating layer includes a first material and a second material having a low dielectric constant and improved strength, and is formed such that the first material is disposed inside the network structure of the second material within the insulating layer, thereby preventing phase separation between the first material and the second material. Therefore, since the insulating layer can form the first material and the second material in a single phase, the strength of the insulating layer can be improved.

[0044] That is, the pre-volume of the second material having a network structure by crosslinking, that is, the molecular motion can be increased, and the polymer chains having a network structure can be structured so as not to be arranged close to each other. Inside the network structure, the first material is partially disposed, whereby the first material and the second material can be formed in a single phase inside the insulating layer.

[0045] Therefore, even when the circuit board according to the embodiment is used for high-frequency applications, the dielectric constant of the insulating layer can be reduced to reduce the transmission loss of high-frequency signals, and the thermal expansion coefficient and mechanical strength of the insulating layer can be improved to ensure the overall reliability of the circuit board.

[0046] 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, the insulating layer including existing glass fibers can be replaced. Specifically, the glass fibers contained in the insulating layer of the circuit board according to the embodiment can be removed. Specifically, the dielectric constant and the thermal expansion coefficient of the insulating layer of the circuit board according to the embodiment can be easily adjusted by using the resin and filler constituting RCC (Resin coated copper), and thereby the overall thickness of the printed circuit board can be reduced by forming the insulating layer with RCC that does not contain existing glass fibers. Furthermore, 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 for ensuring strength be removed, but also the thickness of the insulating layer can be reduced, thereby providing an insulating layer having a thickness smaller than the thickness of the circuit pattern.

Brief Description of the Drawings

[0047]

Figure 1

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Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0048] Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. However, the technical idea of the present invention is not limited to some of the described embodiments, but is realized in various different forms, and within the scope of the technical idea of the present invention, one or more of the components between the embodiments can be selectively combined and replaced for use.

[0049] In addition, the terms (including technical and scientific terms) used in the embodiments of the present invention can be interpreted as having the meanings generally understood by those with ordinary knowledge in the technical field to which the present invention pertains, unless they are specifically defined and described otherwise. Terms that are commonly used like pre-defined terms can be interpreted considering their meanings in the context of the related art.

[0050] In addition, the terms used in the embodiments of the present invention are for the purpose of explaining the embodiments and do not limit the present invention. In this specification, the singular form can include the plural form as well, unless specifically mentioned in a phrase. When described as "at least one (or one or more) of A, B, and C", it can include one or more of all combinations that can be combined with A, B, and C.

[0051] Also, when describing the components of the present invention, terms such as first, second, A, B, (a), (b), etc. can be used. Such terms are merely for distinguishing the components from other components and are not limited to the essence, order, or sequence of the components by those terms.

[0052] And when a component is described as "connected", "coupled", or "joined" to another component, that component can include not only the case where it is directly connected, coupled, or joined to the other component, but also the case where it is "connected", "coupled", or "joined" by another component between that component and the other component.

[0053] Also, when it is described that something is formed or arranged "above or below" each component, "above or below" includes not only the case where two components are in direct contact with each other, but also the case where one or more other components are formed or arranged between the two components.

[0054] Also, when expressed as "above or below", it can include not only the upward direction but also the downward direction with respect to one component.

[0055] Hereinafter, with reference to the drawings, a circuit board according to an embodiment will be described.

[0056] FIG. 1 is a diagram showing a cross-sectional view of a circuit board according to a first embodiment.

[0057] Referring to FIG. 1, a circuit board 1000 according to a first embodiment may include an insulating substrate 100, 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 (here, refer to FIGS. 9 and 10 for the first upper metal layer 170, the second pad 180, and the second upper metal layer 190).

[0058] 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 realized as a single substrate, or alternatively, may be realized as a multilayer substrate in which a plurality of insulating layers are continuously laminated.

[0059] Accordingly, the insulating substrate 100 may include a plurality of insulating portions 110, 120, 130. As shown in FIG. 1, the plurality of insulating portions include a first insulating portion 110, a second insulating portion 120 disposed above the first insulating portion 110, and a third insulating portion 130 disposed below the first insulating portion 110.

[0060] At this time, the first insulating portion 110, the second insulating portion 120, and the third insulating portion 130 may be made of different insulating materials. Preferably, the first insulating portion 110 may include glass fiber. And the second insulating portion 120 and the third insulating portion 130 may not include the glass fiber, unlike the first insulating portion 110.

[0061] As a result, 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.

[0062] That is, the first insulating portion 110 contains glass fibers. The glass fibers generally have a thickness of about 12 μm. As a result, the thickness of each insulating layer constituting the first insulating portion 110 can have a thickness of 21 μm ± 2 μm including the thickness of the glass fibers. Specifically, the thickness of each insulating layer included in the first insulating portion 110 can have a range of 19 μm to 23 μm.

[0063] In contrast, the second insulating portion 120 does not contain the glass fibers. Preferably, each insulating layer constituting the second insulating portion 120 can be composed of RCC. As a result, the thickness of each insulating layer constituting the second insulating portion 120 can have 12 μm ± 2 μm. That is, the thickness of each insulating layer constituting the second insulating portion 120 can have a range of 10 μm to 14 μm.

[0064] Also, the third insulating portion 130 does not contain glass fibers. Preferably, each insulating layer constituting the third insulating portion 130 can be composed of RCC. As a result, the thickness of each insulating layer constituting the third insulating portion 130 can have 12 μm ± 2 μm. That is, the thickness of each insulating layer constituting the third insulating portion 130 can have a range of 10 μm to 14 μm.

[0065] That is, the insulating portion constituting the circuit board in the comparative example includes a plurality of insulating layers, and the plurality of insulating layers are formed of a prepreg (PPG) containing glass fibers. At this time, it is difficult to reduce the thickness of the glass fibers based on the PPG in the circuit board of the comparative example. This is because when the thickness of the PPG decreases, the glass fibers contained in the PPG may be electrically connected to the circuit pattern disposed on the surface of the PPG, thereby generating a crack list. As a result, when the thickness of the PPG is decreased in the circuit board of the comparative example, dielectric breakdown and damage to the circuit pattern may occur. Thus, due to the thickness of the glass fibers constituting the PPG, the circuit board in the comparative example has a limit in reducing the overall thickness.

[0066] In addition, since the circuit board in the comparative example is composed of only an insulating layer of PPG containing glass fibers, 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 approach as a high-frequency substitute. That is, in the circuit board of the comparative example, since the dielectric constant of the glass fiber is high, a phenomenon in which the dielectric constant is broken in the high-frequency band occurs.

[0067] Accordingly, in the embodiment, an insulating layer is formed using an RCC having a low dielectric constant, so that a highly reliable circuit board with minimized signal loss even in a high-frequency band can be provided while slimming the thickness of the circuit board. This can be achieved by the characteristics of the substances in each insulating layer constituting the second insulating portion 120 and the third insulating portion 130, which will be described in more detail below.

[0068] The first insulating portion 110 may include a first insulating layer 111, a second insulating layer 112, a third insulating layer 113, and a fourth insulating layer 114 from the bottom. Further, the first insulating layer 111, the second insulating layer 112, the third insulating layer 113, and the fourth insulating layer 114 may each be formed of a PPG containing glass fibers.

[0069] Further, the second insulating portion 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 portion 120 may be made of RCC with a low dielectric constant and a low coefficient of thermal expansion.

[0070] Also, the third insulating portion 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 portion 130 may be made of RCC with a low dielectric constant and a low coefficient of thermal expansion.

[0071] On the other hand, in the above, the first insulating portion 110 is shown as having a four-layer insulating layer structure, but it is not limited thereto, and the number of insulating layers constituting the first insulating portion 110 may be increased or decreased.

[0072] Also, in the above, the second insulating portion 120 and the third insulating portion 130 are shown as having a two-layer insulating layer structure respectively, but it 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.

[0073] As described above, the circuit board in the first embodiment includes a first insulating portion 110, a second insulating portion 120, and a third insulating portion 130. The first insulating portion 110 is made of PPG containing glass fibers, and the second insulating portion 120 and the third insulating portion 130 may be made of RCC having a low dielectric constant for use in circuit boards applied to high-frequency applications. Also, the second insulating portion 120 and the third insulating portion 130 have a low dielectric constant and can ensure mechanical / chemical safety to improve the reliability of the circuit board.

[0074] The description of the insulating layers constituting the second insulating portion 120 and the third insulating portion 130 as described above will be described in detail below.

[0075] On the other hand, a circuit pattern 140 may be disposed on the surface of each of the insulating layers constituting the first insulating portion 110, the second insulating portion 120, and the third insulating portion 130.

[0076] Preferably, a 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.

[0077] The circuit pattern 140 is a wiring for transmitting an electrical signal and may be formed of a metal material having high electrical conductivity. For this purpose, 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).

[0078] Also, the circuit pattern 140 may be formed of a paste or a solder paste containing at least one metal material selected from gold (Au), silver (Ag), platinum (Pt), titanium (Ti), tin (Sn), copper (Cu), and zinc (Zn) having excellent bonding force. Preferably, the circuit pattern 140 may be formed of copper (Cu) having high electrical conductivity and a relatively low price.

[0079] Also, the thickness of the circuit pattern 140 may be 12 μm ± 2 μm. That is, the thickness of each insulating layer constituting the third insulating portion 130 may be in the range of 10 μm to 14 μm.

[0080] The circuit pattern 140 is possible by an additive process, a subtractive process, an MSAP (Modified Semi Additive Process), and an SAP (Semi Additive Process) method, which are manufacturing processes of a normal printed circuit board. Here, detailed description is omitted.

[0081] On one hand, a buffer layer 400 may be disposed on the surface of each of the insulating layers and / or the circuit pattern 140 that constitute the first insulating portion 110, the second insulating portion 120, and the third insulating portion 130. Specifically, the buffer layer 400 may be disposed on the surface of at least one of the upper surface, lower surface, and side surface of the circuit pattern 140 or on the surface of the insulating layer on which the circuit pattern is disposed.

[0082] The buffer layer formed on the insulating layer or the circuit pattern will be described in detail below.

[0083] At least one via 150 is formed in at least one of the plurality of insulating layers that constitute the first insulating portion 110, the second insulating portion 120, and the third insulating portion 130. The via 150 is disposed to penetrate at least one of the plurality of insulating layers. The via 150 can penetrate only one of the plurality of insulating layers, or alternatively, it may be formed to commonly penetrate at least two of the plurality of insulating layers. Thereby, the via 150 electrically connects the circuit patterns disposed on the surfaces of different insulating layers to each other.

[0084] The via 150 can be formed by filling the inside of a through-hole (not shown) that penetrates at least one of the plurality of insulating layers with a conductive material.

[0085] The through-hole can be formed by any one of machining methods such as mechanical, laser, and chemical processing. When the through-hole is formed by mechanical processing, methods such as milling, drill, and routing can be used. When it is formed by laser processing, UV or CO 2 The laser method can be used. When it is formed by chemical processing, the insulating layer can be opened using chemicals including aminosilane, ketones, etc.

[0086] On the one hand, the processing by the laser is a cutting method that concentrates optical energy on the surface to melt and evaporate a part of the material to form a desired shape. It can easily process complex formations by a computer program and can also process composite materials that are difficult to cut by other methods.

[0087] Also, the processing by the laser has the advantages that the cutting diameter can be as small as 0.005 mm at minimum and the processable thickness range is wide.

[0088] As the laser processing drill, it is preferable to use a YAG (Yttrium Aluminum Garnet) laser, a CO 2 laser, or an ultraviolet (UV) laser. The YAG laser is a laser that can process both the copper foil layer and the insulating layer, and the CO 2 laser is a laser that can only process the insulating layer.

[0089] When the through hole is formed, the inside of the through hole is filled with a conductive material to form the via 150. The metallic material for forming the via 150 can be any one selected from copper (Cu), silver (Ag), tin (Sn), gold (Au), nickel (Ni), and palladium (Pd). For the filling of the conductive material, any one of electroless plating, electroplating, screen printing, sputtering, evaporation method, inkjetting, and dispensing, or a combination of these methods can be used.

[0090] On the upper part of the insulating layer (specifically, the sixth insulating layer 122 that constitutes the second insulating part 120) arranged at the uppermost part of the plurality of insulating layers, the first pad 160 is arranged, and under the insulating layer (specifically, the eighth insulating layer 132 that constitutes the third insulating part 130) arranged at the lowermost part of the plurality of insulating layers, the second pad 180 is arranged.

[0091] In other words, among the plurality of insulating layers, the first pad 160 is disposed on the uppermost insulating layer on which the electronic component 300 is formed. The first pad 160 may be formed in plurality on the uppermost insulating layer. And, a part of the first pad 160 may serve as a pattern for signal transmission, and another part may serve as an inner lead that is electrically connected to the electronic component 300 via a wire or the like. In other words, the first pad 160 may include a wire bonding pad for wire bonding applications.

[0092] And, among the plurality of insulating layers, the second pad 180 is disposed under the lowermost insulating layer to which an external substrate (not shown) is attached. Similar to the first pad 160, a part of the second pad 180 may serve as a pattern for signal transmission, and the remaining part may serve as an outer lead on which an adhesive member (not shown) is disposed for attaching the external substrate. In other words, the second pad 180 may include a soldering pad for soldering applications.

[0093] And, 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 upper metal layer 170 and the second upper metal layer 190 are formed of the same material as each other, and while protecting the first pad 160 and the second pad 180 respectively, improve the wire bonding or the soldering characteristics.

[0094] For this purpose, the first upper metal layer 170 and the second upper metal layer 190 are formed of a metal containing gold (Au). Preferably, the first upper metal layer 170 and the second upper metal layer 190 may contain only pure gold (purity 99% or more), and in contrast, 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.

[0095] On top of the insulating layer disposed at the uppermost part among the plurality of insulating layers, solder paste 200 is disposed. The solder paste is an adhesive for fixing an electronic component 300 attached to the insulating substrate 100. Thus, the solder paste 200 could also be referred to as an adhesive. The adhesive can be a conductive adhesive or, alternatively, a non-conductive adhesive. That is, the circuit board 100 can be a board to which the electronic component 300 is attached by a wire bonding method. As a result, terminals (not shown) of the electronic component 300 may not be disposed on top of the adhesive. Also, the adhesive may not be electrically connected to the electronic component 300. Therefore, a non-conductive adhesive can be used as the adhesive, or alternatively, a conductive adhesive can be used.

[0096] The conductive adhesive is broadly classified into an anisotropic conductive adhesive and an isotropic conductive adhesive, and basically comprises conductive particles such as Ni, Au / polymer, or Ag, and a thermosetting, thermoplastic, or blend type insulating resin that mixes both of these properties.

[0097] Also, the non-conductive adhesive can be a polymer adhesive, and preferably a non-conductive polymer adhesive containing a thermosetting resin, a thermoplastic resin, a filler, a curing agent, and a curing accelerator.

[0098] Also, on top of the uppermost insulating layer, a first protective layer SR1 that exposes at least a part of the surface of the first upper metal layer 170 is disposed. The first protective layer SR1 is disposed to protect the surface of the uppermost insulating layer and can be, for example, a solder resist.

[0099] Then, solder paste 200 is disposed on the first upper metal layer 170, whereby the first pad 160 and the electronic component 300 can be electrically connected.

[0100] Here, the electronic component 300 can include all of the elements and chips. The elements can be classified into active elements and passive elements. The active elements are elements that actively utilize non-linear portions, and the passive elements mean elements that do not utilize non-linear characteristics even if both linear and non-linear characteristics exist. And, the passive elements can include transistors, ICs, semiconductor chips, etc., and the passive elements can include capacitors, resistors, inductors, etc. The passive elements are mounted on a substrate together with a normal semiconductor package in order to increase the signal processing speed of a semiconductor chip which is an active element or perform a filtering function or the like.

[0101] In conclusion, the electronic component 300 can include all of semiconductor chips, light-emitting diode chips, and other drive chips.

[0102] And, a resin molding portion can be formed on the uppermost insulating layer, whereby the electronic component 300 and the first upper metal layer 170 can be protected by the resin molding portion.

[0103] On the other hand, a 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 that exposes the surface of the second upper metal layer 190. The second protective layer SR2 can be formed of a solder resist.

[0104] As described above, a buffer layer can be disposed on at least one surface of the insulating layer or the circuit pattern 140.

[0105] Specifically, the buffer layer 400 is disposed between the insulating layer and the circuit pattern 140 in a region where the insulating layer and the circuit pattern 140 overlap.

[0106] The buffer layer 400 can be a surface treatment layer treated on the surface of the insulating layer. The buffer layer 400 can be a surface treatment layer treated on the surface of the circuit pattern 140.

[0107] 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 layer disposed between the insulating layer and the circuit pattern. The buffer layer 400 may be a functional layer that improves the adhesion between the insulating layer and the circuit pattern, that is, an adhesion enhancing layer.

[0108] FIGS. 2 to 5 are diagrams for explaining the position and arrangement relationship of the buffer layer 400. In the following, the position and arrangement relationship of the buffer layer 400 disposed in the insulating layer constituting the first insulating portion 110 among the plurality of insulating portions will be described. However, the buffer layer 400 can be arranged so as to correspond to the position and arrangement relationship described below also in the insulating layers constituting the second insulating portion 120 and the third insulating portion 130.

[0109] Referring to FIG. 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 and lower surfaces 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 among the surfaces of the circuit pattern.

[0110] Also, referring to FIG. 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, lower, and both side surfaces of the circuit pattern. That is, the buffer layer 400 may be disposed so as to surround the entire surface of the circuit pattern.

[0111] Also, referring to FIG. 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 and lower surfaces 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 among the surfaces of the insulating layer. That is, the buffer layer 400 may be disposed on the front surface of the insulating layer on which the circuit pattern 140 is disposed.

[0112] Referring to FIG. 5, the buffer layer 400 can be disposed on the surface of the insulating layer. For example, the buffer layer 400 can be disposed on the upper surface and the lower surface of the insulating layer. That is, the buffer layer 400 can be disposed on the surface of the insulating layer that contacts or faces the circuit pattern 140. That is, the buffer layer 400 can be disposed only in the region of the surface of the insulating layer where the circuit pattern 140 is disposed.

[0113] That is, the buffer layer 400 is disposed between the insulating layer and the circuit pattern 140. Specifically, the buffer layer 400 is disposed between the insulating layer and the circuit pattern 140, and the buffer layer 400 can be bonded to one surface of the insulating layer and one surface of the circuit pattern 140. That is, the end groups of the buffer layer and the end groups of the insulating layer, and the end groups of the buffer layer and the end groups of the circuit pattern can be chemically bonded.

[0114] The buffer layer 400 can be formed with a certain thickness. Specifically, the buffer layer 400 can be formed as a thin film. Specifically, the buffer layer 400 can be formed with a thickness of 500 nm or less. More specifically, the buffer layer 400 can be formed with a thickness of 5 nm to 500 nm.

[0115] 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 sufficiently ensure the adhesion between the insulating layer and the circuit pattern. When the thickness of the buffer layer is formed to exceed 500 nm, the effect of improving the adhesion due to the thickness is small, and the overall thickness of the circuit board may increase, the dielectric constant of the insulating layer may increase, and the transmission loss of the circuit board in high-frequency applications may increase.

[0116] The buffer layer 400 can contain a plurality of elements. The plurality of elements contained in the buffer layer 400 are bonded to each other in the buffer layer and contained in a molecular form or in an ionic form, and the molecules, the molecules, and the ions can be chemically bonded to each other to form a buffer layer.

[0117] The buffer layer 400 can contain at least one element among a carbon element, a nitrogen element, an oxygen element, a silicon element, a sulfur element, and a metal element. Specifically, it can contain all of the carbon element, nitrogen element, oxygen element, silicon element, sulfur element, and metal element of the buffer layer 400.

[0118] The carbon element, nitrogen element, oxygen element, silicon element, sulfur element, and metal element can each be bonded to one another within the buffer layer and exist in a molecular form, or can exist in a single ionic form.

[0119] Among the plurality of elements, the oxygen element, the carbon element, and the nitrogen element can be related to the functional group of the buffer layer that binds to the insulating layer. That is, a functional group formed by a molecule containing the oxygen element, the carbon element, the nitrogen atom, etc. can chemically bond to the insulating layer.

[0120] Also, among the plurality of elements, the carbon element, the nitrogen element, the silicon element, and the sulfur element can be related to the functional group of the buffer layer that binds to the circuit pattern. That is, a functional group formed by a molecule containing the carbon element, the nitrogen element, the silicon element, the sulfur element, etc. can chemically bond to the circuit pattern.

[0121] Also, the metal element can bond the molecules formed by the carbon element, nitrogen element, oxygen element, silicon element, and sulfur element to one another. That is, the molecules formed by the carbon element, nitrogen element, oxygen element, silicon element, and sulfur element can chemically bond through the metal element to form a buffer layer. That is, the metal element can be disposed between the molecules and serve as a medium for chemically bonding the molecules.

[0122] For this purpose, the carbon element, nitrogen element, oxygen element, silicon element, sulfur element, and metal element may be included in a certain mass ratio. Specifically, among the plurality of elements, the metal element can be included in the largest amount compared to other elements, and the carbon element, nitrogen element, oxygen element, silicon element, and sulfur element can be included in a certain mass ratio based on the metal element.

[0123] Specifically, the ratio of the carbon element to the metal element ((carbon element / copper element) * 100) can be 5 to 7.

[0124] Also, the ratio of the nitrogen element to the metal element ((nitrogen element / copper element) * 100) can be 1.5 to 7.

[0125] Also, the ratio of the oxygen element to the metal element ((oxygen element / copper element) * 100) can be 1.1 to 1.9.

[0126] Also, the ratio of the silicon element to the metal element ((silicon element / copper element) * 100) can be 0.5 to 0.9.

[0127] Also, the ratio of the sulfur element to the metal element ((sulfur element / copper element) * 100) can be 0.5 to 1.5.

[0128] The ratios of the carbon element, nitrogen element, oxygen element, silicon element, and sulfur element to the metal element may be related to the bonding force of the insulating layer or the circuit board.

[0129] Specifically, when the ratio of the carbon element to the metal element ((carbon element / copper element) * 100) is outside 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 become weak.

[0130] Also, when the ratio of the nitrogen element to the metal element ((nitrogen element / copper element) * 100) is outside 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 become weak.

[0131] In addition, when the ratio of the oxygen element to the metal element ((oxygen element / copper element) * 100) is outside the range of 1.1 to 1.9, the bonding strength between the buffer layer and the insulating layer may become weak.

[0132] In addition, when the ratio of the silicon element to the metal element ((silicon element / copper element) * 100) is outside the range of 0.5 to 0.9, the bonding strength between the buffer layer and the circuit board may become weak.

[0133] In addition, when the ratio of the sulfur element to the metal element ((sulfur element / copper element) * 100) is outside the range of 0.5 to 1.5, the bonding strength between the buffer layer and the circuit board may become weak.

[0134] On the other hand, the carbon element, nitrogen element, oxygen element, silicon element, sulfur element, and metal element exist in the form of molecules or ions in the buffer layer, and the molecules and ions can be bonded and linked to each other.

[0135] Specifically, the buffer layer 400 can contain molecules and metal ions formed by the carbon element, nitrogen element, oxygen element, silicon element, sulfur element, and metal element. The molecules contained in the buffer layer 400 can contain at least two types of molecules according to the size of the molecules or the molecular weight. Specifically, the molecules can include macromolecules and unimoleculars.

[0136] The macromolecules, unimoleculars, and metal ions can be formed into a structure in which they are bonded and linked to each other within the buffer layer.

[0137] Specifically, the macromolecules, unimoleculars, and metal ions can be formed into a structure in which they are chemically bonded to each other by covalent bonds and coordination bonds and linked to each other within the buffer layer.

[0138] The metal ion can link the macro molecule, the single molecule, or the macro molecule and the single molecule to each other. Specifically, the macro molecule, the single molecule, or the macro molecule and the single molecule can form a coordination bond with the metal ion, whereby the macro molecule, the single molecule, or the macro molecule and the single molecule can be chemically bonded to each other.

[0139] The metal ion can contain the same substance as the circuit pattern. Alternatively, the metal ion can contain a substance different from the circuit pattern. For example, when the circuit pattern contains copper, the metal ion can contain copper or another metal other than copper.

[0140] Specifically, the metal ion can be formed by the circuit pattern. Specifically, another oxidizing agent can be used to ionize the circuit pattern containing metal to form metal ions. Thereby, the ionized metal ions can form a coordination bond with the macro molecule and the single molecule in the buffer layer, and the buffer layer can be formed by linking the molecules to each other.

[0141] Alternatively, another metal ion can be added during the formation of the buffer layer, and the metal ion can form a coordination bond with the macro molecule and the single molecule in the buffer layer to link the molecules to each other, thereby forming the buffer layer. At this time, the separately added metal ion may be the same as or different from the metal of the circuit pattern.

[0142] The macro molecule and the single molecule can contain at least one of the carbon element, nitrogen element, oxygen element, silicon element, and sulfur element.

[0143] That is, the macro molecule and the single molecule can be molecules containing at least one of the carbon element, nitrogen element, oxygen element, silicon element, and sulfur element.

[0144] Specifically, the macro molecule can include a molecule containing the carbon element and the nitrogen element. Specifically, the macro molecule can include an azole group containing the carbon element and the nitrogen element.

[0145] In addition, the macro molecule can include a molecule containing the silicon element. Specifically, the macro molecule can include a silane group containing the silicon element.

[0146] In addition, the single molecule can contain the carbon element, the nitrogen element, and the sulfur element. That is, the single molecule can be a molecule containing the carbon element, the nitrogen element, and the sulfur element. For example, the single molecule can include an SCN group to which a thiocyanate group (-SCN) is linked.

[0147] Referring to FIG. 3, the buffer layer 400 can include a plurality of functional groups. Specifically, the buffer layer 400 can include a first functional group that chemically bonds to the insulating layer and a second functional group that chemically bonds to the circuit pattern 140.

[0148] That is, the macro molecule and the single molecule can include a plurality of end groups, that is, functional groups, that chemically bond to the insulating layer and the circuit pattern. Such functional groups can chemically and firmly bond the insulating layer and the circuit pattern by means of the buffer layer, and the adhesion between the insulating layer and the circuit pattern can be improved.

[0149] The first functional group and the second functional group can be defined as end groups of the buffer layer that are linked to one of the macro molecule, the single atom, or the metal atom.

[0150] The first functional group can bond to the insulating layer by a covalent bond. The first functional group can include a functional group that covalently bonds to the insulating layer. Specifically, the first functional group can include a hydroxy group (-OH) and an N group of an azole group.

[0151] In addition, the second functional group can be bonded to the circuit pattern 140 by a coordination bond. The second functional group can include a functional group that is coordinated and bonded to the circuit pattern 140. Specifically, the second functional group can include an Si group of a silane group and a thiocyanate group (-SCN).

[0152] The first functional group and the second functional group included in the buffer layer can be chemically bonded to the insulating layer and the circuit pattern, respectively. Thereby, the buffer layer disposed between the insulating layer and the circuit pattern can improve the adhesion between the insulating layer, which is a different substance, and the circuit pattern.

[0153] On the other hand, as described above, the insulating layer constituting the second insulating portion 120 and the third insulating portion 130 can include a substance that can ensure mechanical and chemical reliability together with a low dielectric constant.

[0154] Specifically, the insulating layers 121, 122, 131, and 132 can have a dielectric constant Dk of 3.0 or less. More specifically, the insulating layers 121, 122, 131, and 132 can have a dielectric constant of 2.03 to 2.7. Therefore, since the insulating layer can have a low dielectric constant, when the insulating layer is applied to a circuit board for high-frequency applications, transmission loss according to the magnitude of the dielectric constant of the insulating layer can be reduced.

[0155] In addition, the insulating layers 121, 122, 131, and 132 can have a thermal expansion coefficient of 50 ppm / °C or less. More specifically, the insulating layers 121, 122, 131, and 132 can have a thermal expansion coefficient of 15 ppm / °C to 50 ppm / °C.

[0156] Thereby, the insulating layers 121, 122, 131, and 132 can have a low thermal expansion coefficient, so that cracks in the insulating layer due to temperature changes can be minimized.

[0157] For this purpose, the insulating layers 121, 122, 131, and 132 can be formed of two substances. Specifically, the insulating layers 121, 122, 131, and 132 can include a substance in which two compounds are mixed. Specifically, the insulating layers 121, 122, 131, and 132 can include a first compound and a second compound.

[0158] The first substance and the second substance can be included within a certain ratio range. Specifically, the first substance and the second substance can be included in a ratio of 4:6 to 6:4.

[0159] In addition, the insulating layers 121, 122, 131, and 132 can further include inorganic particles. Specifically, the insulating layers 121, 122, 131, and 132 can further include inorganic particles such as silicon dioxide (SiO2). The inorganic particles can be included in an amount of about 55 wt% to 70 wt% based on the entire insulating layers 121, 122, 131, and 132.

[0160] When the ratio of the inorganic particles is outside the above range, the coefficient of thermal expansion or the dielectric constant may increase due to the inorganic particles, and the characteristics of the insulating layer may deteriorate.

[0161] In addition, the first substance and the second substance can be chemically unbonded to each other within the insulating layers 121, 122, 131, and 132. However, the embodiments are not limited thereto, and the first substance containing the first compound and the second substance containing the second compound can be chemically bonded directly or through another linking group.

[0162] The first substance can include a substance having insulating properties. In addition, the first substance can have high impact strength and improved mechanical properties. Specifically, the first substance can include a resin substance. For example, the first substance can include a first compound containing polyphenyl ether (PPE).

[0163] The first substance can contain a plurality of the first compounds, and the first compounds can be chemically bonded to each other. Specifically, the first compounds can be linearly linked to each other by a covalent bond, i.e., a pi (π-π) bond.

[0164] That is, the first compounds can be chemically bonded to each other such that the molecular weight of the first substance has a molecular weight of about 300 to 500.

[0165] In addition, the second substance can contain a second compound. Specifically, the second substance can be formed by a plurality of second compounds being chemically bonded to each other.

[0166] The second compound can contain a substance having a low dielectric constant and a low coefficient of thermal expansion. Furthermore, the second compound can contain a substance having improved mechanical strength.

[0167] The second compound can contain tricyclodecane and a terminal group linked to the tricyclodecane. The terminal group linked to the tricyclodecane can contain various substances by which the second compounds can be linked to each other by a carbon-carbon double bond (C=C bond). Specifically, the terminal group linked to the tricyclodecane can contain an acrylate group, an epoxide group, a carboxyl group, a hydroxyl group, and an isocyanate group.

[0168] The terminal groups linked to the tricyclodecane in the second compound can be linked to each other. Specifically, the second compound can be cross-linked by a carbon-carbon double bond (C=C bonding) between the terminal groups to form a network structure.

[0169] Specifically, referring to FIG. 7, the second compound can be cross-linked to form a network structure and be linked. That is, the second compound can be an aggregate of bonds having a plurality of network structures.

[0170] As a result, the second substance formed by the second compound can have improved mechanical strength due to the network structure while having a low dielectric constant and a low coefficient of thermal expansion due to the substance characteristics.

[0171] FIG. 8 is a diagram for explaining the arrangement of the first substance and the second substance constituting the insulating layer.

[0172] The first substance and the second substance can be formed into one single phase within the insulating layer. Referring to FIG. 8, the first substance connected by the covalent bond of the first compound can be arranged inside the second substance formed by the second compound that cross-links with each other to form a network structure.

[0173] Specifically, the first compound can be arranged inside the network structure of the second substance formed by chemically bonding the second compound, preventing the separation of the first substance and the second substance.

[0174] That is, in the insulating layer, the first substance and the second substance can be formed into a single-phase structure without being phase-separated and arranged within the insulating layer. As a result, due to the substance characteristics of the first substance and the second substance, it can have a high mechanical strength because it can be formed into a single phase while having a low dielectric constant and a low coefficient of thermal expansion.

[0175] On the other hand, in the first embodiment, the first insulating portion 110 is configured with an insulating layer made of PPG containing glass fibers, and the second insulating portion 120 and the third insulating portion 130 are configured with RCC having a low dielectric constant and a low coefficient of thermal expansion as described above.

[0176] In contrast, the circuit board can be composed only of RCC having a low dielectric constant and a low coefficient of thermal expansion as described above.

[0177] FIG. 9 is a diagram showing a cross-sectional view of a circuit board according to the second embodiment.

[0178] Referring to FIG. 9, the circuit board 1000A can 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.

[0179] The insulating substrate 100A can be composed of an insulating portion 110A including a plurality of insulating layers.

[0180] That is, the insulating portion 110A can include first to eighth insulating layers 111a, 112a, 113a, 114a, 115a, 116a, 117a, 118a, 119a from the bottom. However, in the embodiment, although the insulating portion 110A is shown as having an eight-layer structure, it is not limited thereto, and the number of insulating layers may increase or decrease.

[0181] In other words, the insulating portion of the first embodiment is composed of a first insulating portion of PPG, a second insulating portion of RCC, and a third insulating portion of RCC.

[0182] In contrast, the insulating portion in the second embodiment can be composed only of RCC.

[0183] At this time, the insulating portion 110A in the second embodiment has a low dielectric constant and a low coefficient of thermal expansion as described above. Thus, even without the same PPG as in the first embodiment, rigidity can be ensured, and even if it is composed only of RCC, it does not affect the reliability of the rigidity of the circuit board.

[0184] FIG. 10 is a diagram showing a cross-sectional view of a circuit board according to a third embodiment.

[0185] Referring to FIG. 10, the circuit board 1000B can 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.

[0186] The insulating substrate 100B may be composed of an insulating portion 110B including a plurality of insulating layers.

[0187] That is, the insulating portion 110B may include first to eighth insulating layers 111b, 112b, 113b, 114b, 115b, 116b, 117b, 118b, and 119b from the bottom. However, in the embodiment, although the insulating portion 110B is shown as having an eight-layer structure, it is not limited thereto, and the number of insulating layers may increase or decrease.

[0188] In other words, the insulating portion of the first embodiment is composed of a first insulating portion of PPG, a second insulating portion of RCC, and a third insulating portion of RCC.

[0189] In contrast, the insulating portion of the third embodiment may be composed only of RCC.

[0190] At this time, as described above, the insulating portion 110B in the third embodiment has a low dielectric constant and a low coefficient of thermal expansion. Thus, even without the same PPG as in the first embodiment, rigidity can be ensured, and even if it is composed only of RCC, it does not affect the reliability of the rigidity of the circuit board.

[0191] Here, the circuit pattern in the embodiment has a low roughness, and the insulating layers constituting the insulating portion 110B have a low dielectric constant and a low coefficient of thermal expansion.

[0192] Thus, 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 in the third embodiment may be smaller than the thickness H1 of the circuit pattern 140.

[0193] For example, the thickness H2 of the circuit pattern 140 may have 12 μm ± 2 μm. That is, the thickness of each insulating layer constituting the third insulating portion 130 may have a range of 10 μm to 14 μm.

[0194] Further, each of the thicknesses H2 of the first to eighth insulating layers 111b, 112b, 113b, 114b, 115b, 116b, 117b, 118b, and 119b constituting the insulating portion 110B can be 8 μm ± 2 μm. That is, the thickness of each insulating layer constituting the third insulating portion 130 can be in the range of 6 μm to 10 μm.

[0195] As a result, the thickness of the via 150 disposed in each of the first to eighth insulating layers 111b, 112b, 113b, 114b, 115b, 116b, 117b, 118b, and 119b constituting the insulating portion 110B may also be smaller than the thickness of the circuit pattern 140.

[0196] On the other hand, the insulating layers constituting the second insulating portion 120 and the third insulating portion 130 in the first embodiment are also constituted by insulating layers as in the third embodiment. Accordingly, the thickness of each insulating layer constituting the second insulating portion 120 and the third insulating portion 130 in the first embodiment may be smaller than the thickness of the circuit pattern.

[0197] Hereinafter, the present invention will be described in more detail through dielectric constant measurements of examples and comparative examples that can form the insulating portions 110A and 110B as in the second and third embodiments. Such examples are merely presented as illustrations for explaining the present invention in more detail. Therefore, the present invention is not limited to such examples.

[0198] Example 1

[0199] A copper layer was formed on the insulating layer. At this time, after coating a coating layer containing a carbon element, a nitrogen element, an oxygen element, a silicon element, a sulfur element, and a metal element on the surface of the circuit layer that contacts the insulating layer, the copper layer and the insulating layer were adhered.

[0200] Next, the copper layer was patterned to form a circuit pattern, and a circuit board was manufactured.

[0201] At this time, the buffer layer included a first functional group containing a hydroxy group (-OH) and an N group of an azole group, and a second functional group containing an Si group of a silane group and a thiocyanate group (-SCN).

[0202] Next, the adhesive strength and reliability were evaluated according to the roughness of the circuit pattern.

[0203] Comparative Example 1

[0204] A circuit pattern was formed in the same manner as in the example, except that a coating layer was not formed on the copper layer, the copper layer was directly adhered to the insulating layer to form a copper layer, and the copper layer was patterned to form a circuit pattern. Then, the adhesive strength and reliability were evaluated according to the roughness of the circuit pattern.

[0205] Adhesion and Reliability Measurement Method

[0206] For the adhesive strength evaluation of the circuit patterns according to the examples and comparative examples, the UTM 90° Peel value was measured using a UTM device.

[0207] In addition, for the reliability evaluation, when the peel strength (kgf / cm) of the circuit pattern was less than 0.6, it was evaluated as NG.

[0208]

Table 1

[0209]

Table 2

[0210] 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. Specifically, for the circuit board according to Example 1, a coating layer on the insulating layer forms the coated circuit pattern. Thus, it can be understood that by chemically and firmly bonding the coating layer to the insulating layer and the circuit pattern, the peel strength of the circuit pattern can be increased, improving the adhesion of the circuit pattern and the reliability of the circuit board. It can be seen that the circuit board according to Example 1 can have an adhesion that can ensure the reliability of the circuit board even when the roughness of the circuit pattern decreases. Specifically, it can be seen that the circuit board according to Example 1 can have an 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.

[0211] That is, when the circuit board according to Example 1 is applied to high-frequency applications, the roughness of the circuit pattern may be reduced to reduce transmission loss due to the skin effect, and even with a low surface roughness, the adhesion of the circuit pattern can be improved by the coating layer to ensure the reliability of the circuit pattern.

[0212] 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, it can be seen that since the insulating layer and the circuit pattern are formed of different substances, the adhesion of the circuit pattern, that is, the peel strength, is very low.

[0213] That is, it can be seen that the circuit board according to Comparative Example 1 cannot ensure reliability unless the surface roughness of the circuit pattern is increased, and when the circuit pattern has a low surface roughness, the reliability of the circuit board decreases.

[0214] Therefore, it can be seen that when the circuit board according to Comparative Example 1 is applied to high-frequency applications, the transmission loss due to the skin effect increases due to the surface roughness of the circuit pattern.

[0215] Example 2

[0216] A copper layer was formed on the insulating layer.

[0217] Next, the copper layer was patterned to form a circuit pattern, and a circuit board was manufactured.

[0218] At this time, the insulating layer was formed by putting polyphenyl ether (PPE) and tricyclodecane-based di-acrylate (Tricyclodecane based di-acrylete) in which acrylate was linked to tricyclodecane into a toluene solvent, then allowing the mixing to proceed at a temperature of about 100 °C, and then adding an Azo compound initiator and a peroxide initiator.

[0219] Next, by changing the magnitude of the frequency, the dielectric constant, reliability, and thermal expansion coefficient of the insulating layer were measured according to the weight ratio of the polyphenyl ether (A) and the tricyclodecane-based di-acrylate (Tricyclodecane based di-acrylete) (B).

[0220] [Table 3]

[0221] [Table 4]

[0222] [Table 5]

[0223] Referring to Tables 3 to 5, it can be seen that the insulating layer according to the embodiment has a low dielectric constant and a coefficient of thermal expansion, and has improved reliability due to improved mechanical strength when polyphenyl ether (A) and tricyclodecane-based di-acrylate (B) satisfy a ratio of 4:6 to 6:4. On the other hand, when the insulating layer does not satisfy the ratio of polyphenyl ether (A) and tricyclodecane-based di-acrylate (B), the mechanical strength may decrease and cracks may occur in the insulating layer, and the dielectric constant may increase, making it unsuitable for use as an insulating layer of a high-frequency circuit board.

[0224] The circuit board according to the embodiment may include a buffer layer disposed between the insulating layer and the circuit pattern.

[0225] That is, for the circuit board according to the embodiment, a buffer layer can be formed on the surface of the circuit pattern or on the insulating layer.

[0226] The buffer layer is disposed between the insulating layer and the circuit pattern, and can improve the adhesion between the insulating layer and the circuit pattern.

[0227] That is, the insulating layer and the circuit pattern are heterogeneous substances each containing a resin material and a metal, and there is a problem that the adhesive force decreases when the circuit pattern is formed on the insulating layer.

[0228] Therefore, a buffer layer that chemically bonds to the insulating layer and the circuit pattern respectively can be disposed between the insulating layer and the circuit pattern to improve the adhesion between the insulating layer and the circuit pattern.

[0229] That is, the buffer layer includes a plurality of functional groups that bond to the insulating layer and the circuit pattern, and by chemically bonding the functional groups to the insulating layer and the circuit pattern through covalent bonding or coordination bonding, the adhesion between the insulating layer and the circuit pattern can be improved.

[0230] Thereby, even if the surface roughness of the insulating layer is reduced, the adhesion reliability between the insulating layer and the circuit pattern can be ensured.

[0231] Therefore, even when the circuit board according to the embodiment is used for high-frequency applications, the surface roughness of the circuit pattern can be kept low to reduce the transmission loss of high-frequency signals, and even if the surface roughness of the circuit pattern is kept low, the buffer layer can ensure the adhesion between the insulating layer and the circuit pattern, so the overall reliability of the circuit pattern can be ensured.

[0232] In addition, the circuit board according to the embodiment can include an insulating layer having a low dielectric constant and a low coefficient of thermal expansion and having improved strength.

[0233] Specifically, the insulating layer includes a first substance and a second substance having a low dielectric constant and improved strength, and in the insulating layer, the first substance is formed to be disposed inside the network structure of the second substance, whereby phase separation between the first substance and the second substance can be prevented. Therefore, the insulating layer can form the first substance and the second substance in a single phase, so that the strength of the insulating layer can be improved.

[0234] That is, the pre-volume of the second substance having a network structure by crosslinking, that is, the molecular motion can be increased so that polymer chains having a network structure are not arranged closely, and inside the network structure, the first substance is partially disposed, whereby the first substance and the second substance can be formed in a single phase inside the insulating layer.

[0235] Therefore, even when the circuit board according to the embodiment is used for high-frequency applications, the dielectric constant of the insulating layer can be reduced to reduce the transmission loss of high-frequency signals, and the thermal expansion coefficient and mechanical strength of the insulating layer can be improved to ensure the overall reliability of the circuit board.

[0236] 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 containing glass fibers. Specifically, the glass fibers contained in the insulating layer of the circuit board according to the embodiment can be removed. Specifically, the dielectric constant and the thermal expansion coefficient of the insulating layer of the circuit board according to the embodiment can be easily adjusted by using the resin and filler constituting RCC (Resin coated copper), and thereby, by forming the insulating layer with RCC that does not contain existing glass fibers, the overall thickness of the printed circuit board can be reduced. Further, 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 for ensuring strength be removed, but also the thickness of the insulating layer can be reduced, thereby providing an insulating layer having a thickness smaller than the thickness of the circuit pattern.

Claims

1. A first insulating layer containing glass fibers, a first circuit pattern disposed on the upper surface of the first insulating layer, a second circuit pattern disposed on the lower surface of the first insulating layer, a first via penetrating the first insulating layer and disposed between the first circuit pattern and the second circuit pattern, a second insulating layer disposed on the upper surface of the first insulating layer and not containing glass fibers, a third circuit pattern disposed on the upper surface of the second insulating layer, a second via penetrating the second insulating layer and disposed between the first circuit pattern and the third circuit pattern, a third insulating layer disposed on the lower surface of the first insulating layer and not containing glass fibers, a fourth circuit pattern disposed on the lower surface of the third insulating layer, a third via penetrating the third insulating layer and disposed between the second circuit pattern and the fourth circuit pattern, and the thickness of the first via is greater than the thickness of the first circuit pattern and the thickness of the second circuit pattern, the thickness of the second via is smaller than the thickness of the third circuit pattern, the thickness of the third via is smaller than the thickness of the fourth circuit pattern, a circuit board.

2. The first insulating layer includes a plurality of inner insulating layers laminated along the thickness direction, and an inner circuit pattern is disposed between the plurality of inner insulating layers. The circuit board according to Claim 1.

3. The second insulating layer includes a plurality of upper insulating layers laminated on the first insulating layer, the third circuit pattern is respectively disposed on the upper surfaces of the plurality of upper insulating layers, and the second via is disposed penetrating at least a partial region of each of the plurality of upper insulating layers. The circuit board according to Claim 1.

4. The third insulating layer includes a plurality of lower insulating layers laminated on the lower surface of the first insulating layer, the fourth circuit pattern is respectively disposed on the lower surfaces of the plurality of lower insulating layers, and the third via is disposed penetrating at least a partial region of each of the plurality of lower insulating layers. The circuit board according to Claim 1.

5. The thickness of the first insulating layer is greater than the thickness of the second insulating layer and the thickness of the third insulating layer. The circuit board according to Claim 1.

6. The plurality of inner insulating layers include first to fourth inner insulating layers, The first via includes a first via portion penetrating through the first inner insulating layer, a second via portion penetrating through the second inner insulating layer, a third via portion penetrating through the third inner insulating layer, and a fourth via portion penetrating through the fourth inner insulating layer. The circuit board according to claim 2, wherein the thickness of each of the first to fourth via portions is greater than the thickness of each of the first circuit pattern, the second circuit pattern, and the inner layer circuit pattern.

7. The circuit board according to claim 2, wherein the thickness of the second via is smaller than the thickness of each of the first circuit pattern, the second circuit pattern, the inner layer circuit pattern, and the fourth circuit pattern.

8. The circuit board according to claim 6, wherein the thickness of the third via is smaller than the thickness of each of the first circuit pattern, the second circuit pattern, the inner layer circuit pattern, and the third circuit pattern.

9. The circuit board according to claim 6, wherein the direction in which the first via portion or the second via portion is inclined is different from the direction in which the third via portion or the fourth via portion is inclined.

10. The direction in which the first via portion is inclined and the direction in which the second via portion is inclined are the same as each other. The circuit board according to claim 9, wherein the direction in which the third via portion is inclined and the direction in which the fourth via portion is inclined are the same as each other.

11. The direction in which the second via is inclined is the same as the direction in which the third via portion is inclined and the direction in which the fourth via portion is inclined. The circuit board according to claim 10, wherein the direction in which the third via is inclined is the same as the direction in which the first via portion is inclined and the direction in which the second via portion is inclined.

12. The second and third insulating layers include a first compound containing polyphenyl ether <Polyphenyl Ether, PPE>, a second compound containing tricyclodecane, and a terminal group linked to the tricyclodecane. The circuit board according to claim 1, wherein the weight ratio of the first compound to the second compound is 4:6 to 6:

4.

13. The circuit board according to claim 12, wherein the terminal group includes at least one of an acrylate group, an epoxide group, a carboxyl group, a hydroxyl group, and an isocyanate group.

14. The circuit board according to claim 12, wherein the first compound and the second compound are chemically unbonded.

15. The circuit board according to claim 1, wherein the coefficient of thermal expansion and the dielectric constant of each of the second and third insulating layers are smaller than the coefficient of thermal expansion and the dielectric constant of the first insulating layer.

16. The circuit board according to claim 15, wherein the dielectric constant of each of the second and third insulating layers is 2.03 to 2.7.

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