Laminate, circuit board, and method for manufacturing circuit board

Abstract

To provide laminate capable of forming a metal base circuit board having excellent insulation reliability under conditions of high voltage application.SOLUTION: Laminate includes: a first metal layer; an insulation layer disposed on the first metal layer; and a second metal layer disposed on the insulation layer. At least one of a bonding surface of the first metal layer with the insulation layer and a bonding surface of the second metal layer with the insulation layer exhibits a surface roughness curve having a reference length of 250 μm, an average length RSm of an element of 10 μm or more, and a maximum height Rz of 20 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a laminate suitable for use in producing a circuit board (metal-based circuit board), a circuit board, and a method for producing a circuit board. [Background technology]

[0002] A variety of circuit boards have been put to practical use to form hybrid integrated circuits by mounting electronic and electrical components such as semiconductor elements. Circuit boards are classified based on the board material into resin circuit boards, ceramic circuit boards, metal-based circuit boards, etc.

[0003] Resin circuit boards are inexpensive, but due to the low thermal conductivity of the substrate, they are limited to applications requiring relatively low power. Ceramic circuit boards, due to the high electrical insulation and heat resistance characteristics of ceramics, are suitable for applications requiring relatively high power, but have the disadvantage of being expensive. On the other hand, metal-based circuit boards have properties intermediate between the two, and are suitable for general-purpose applications requiring relatively high power, such as refrigerator inverters, commercial air conditioner inverters, power supplies for industrial robots, and automotive power supplies.

[0004] For example, Patent Document 1 discloses a method for obtaining a circuit board having excellent stress relaxation properties, heat resistance, moisture resistance, and heat dissipation properties by using a composition for circuit boards containing a specific epoxy resin, a curing agent, and an inorganic filler as essential components. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-266533 Summary of the Invention [Problem to be solved by the invention]

[0006] If ceramic circuit substrates could be replaced with metal-based circuit substrates, productivity could be expected to improve. In the industrial module field where ceramic circuit substrates are used, high voltages are sometimes applied under harsh conditions, and high reliability under such conditions is required.

[0007] Therefore, an object of the present invention is to provide a laminate that can form a metal base circuit board having excellent insulation reliability under high voltage application conditions, and to provide a metal base circuit board having excellent insulation reliability under high voltage application conditions and a method for manufacturing the same. [Means for solving the problem]

[0008] One aspect of the present invention relates to a laminate comprising a first metal layer, an insulating layer disposed on the first metal layer, and a second metal layer disposed on the insulating layer, wherein at least one of a bonding surface of the first metal layer with the insulating layer and a bonding surface of the second metal layer with the insulating layer exhibits a surface roughness curve having a reference length of 250 μm, a mean element length RSm of 10 μm or more, and a maximum height Rz of 20 μm or less.

[0009] In one embodiment, both the bonding surface of the first metal layer with the insulating layer and the bonding surface of the second metal layer with the insulating layer may exhibit the surface roughness curve.

[0010] In one embodiment, the insulating layer may have a thickness of 30 μm or more.

[0011] In one embodiment, the first metal layer and the second metal layer may contain 60% by mass or more of at least one metal atom selected from the group consisting of aluminum, copper, iron, silver, gold, zinc, nickel, and tin.

[0012] In one embodiment, the insulating layer may contain a cured insulating resin and an inorganic filler.

[0013] Another aspect of the present invention relates to a circuit board comprising a metal layer, an insulating layer disposed on the metal layer, and a metal circuit portion disposed on the insulating layer, wherein at least one of a bonding surface of the metal layer with the insulating layer and a bonding surface of the metal circuit portion with the insulating layer exhibits a surface roughness curve having a reference length of 250 μm, a mean element length RSm of 10 μm or more, and a maximum height Rz of 20 μm or less.

[0014] In one embodiment, both the bonding surface of the metal layer with the insulating layer and the bonding surface of the metal circuit portion with the insulating layer may exhibit the surface roughness curve.

[0015] Yet another aspect of the present invention relates to a method for manufacturing a circuit board, including the steps of preparing the above-mentioned laminate and removing a portion of the first metal layer or a portion of the second metal layer of the laminate to form a metal circuit portion. [Effects of the Invention]

[0016] According to the present invention, there is provided a laminate capable of forming a metal base circuit board having excellent insulation reliability under high voltage application conditions. Also, according to the present invention, there are provided a metal base circuit board having excellent insulation reliability under high voltage application conditions and a method for manufacturing the same. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view showing one embodiment of a laminate. [Figure 2] FIG. 1 is a cross-sectional view illustrating an embodiment of a circuit board. DETAILED DESCRIPTION OF THE INVENTION

[0018] Preferred embodiments of the present invention will be described in detail below.

[0019] [Laminate] The laminate of this embodiment includes a first metal layer, an insulating layer disposed on the first metal layer, and a second metal layer disposed on the insulating layer. The laminate of this embodiment can also be called a laminate for forming a circuit board.

[0020] In the laminate of this embodiment, at least one of the bonding surface (S1) of the first metal layer with the insulating layer and the bonding surface (S2) of the second metal layer with the insulating layer exhibits a surface roughness curve with a reference length of 250 μm, an average element length RSm of 10 μm or more, and a maximum height Rz of 20 μm or less.

[0021] The laminate of this embodiment can form a metal base circuit board having excellent insulation reliability (particularly, the effect of suppressing deterioration of electrical insulation over time) under conditions of high voltage application. The reason why the laminate of this embodiment exhibits such an effect is not entirely clear, but it is thought that this is because by roughening at least one of the metal layers to exhibit the above-mentioned surface roughness curve, electric field concentration during high voltage application is suppressed, and a decrease in insulation reliability due to electric field concentration is suppressed.

[0022] In this specification, the surface roughness curve is measured using a laser microscope (VK-X1000 manufactured by Keyence Corporation).

[0023] The mean element length (RSm) indicates the average length of the roughness curve elements in the reference length, and is a value calculated from the surface roughness curve in accordance with JIS B 0601. The maximum height (Rz) indicates the sum of the height of the highest peak (Rp) and the depth of the deepest valley (Rv) in the roughness curve in the reference length, and is a value calculated from the surface roughness curve in accordance with JIS B 0601.

[0024] In this embodiment, "exhibiting a specific surface roughness curve" means that the specific surface roughness curve is measured on at least a portion of the target surface.

[0025] (metal layer) The metal material constituting the first metal layer is not particularly limited and may be, for example, aluminum, copper, iron, silver, gold, zinc, nickel, tin, alloys containing these metals, etc. The first metal layer may be composed of one type of metal material, or may be composed of two or more types of metal materials.

[0026] The first metal layer preferably contains at least one metal atom (M1) selected from the group consisting of aluminum, copper, iron, silver, gold, zinc, nickel, and tin. The metal atom (M1) is preferably at least one selected from the group consisting of aluminum, copper, and iron, and more preferably at least one selected from the group consisting of aluminum and copper.

[0027] The content of the metal atom (M1) may be, for example, 50 mass% or more, preferably 60 mass% or more, more preferably 70 mass% or more, and even more preferably 80 mass% or more, based on the total amount of the first metal layer, and may be 90 mass% or more, or even 100 mass%.

[0028] The first metal layer may be, for example, a metal plate. The thickness of the first metal layer is not particularly limited and may be, for example, 0.01 mm or more, preferably 0.1 mm or more, and more preferably 1.0 mm or more. The thickness of the first metal layer may be, for example, 10 mm or less, preferably 5.0 mm or less, and more preferably 3.0 mm or less.

[0029] The bonding surface (S1) of the first metal layer may be a roughened surface. The roughening method is not particularly limited, and any known roughening treatment can be used without particular limitation. Examples of roughening treatment include chemical etching, blasting, and buffing.

[0030] The conditions for the roughening treatment are not particularly limited, and for example, the conditions may be appropriately selected so that the joining surface (S1) exhibits the surface roughness curve (C) described below.

[0031] The metal material constituting the second metal layer is not particularly limited and may be, for example, aluminum, copper, iron, silver, gold, zinc, nickel, tin, alloys containing these metals, etc. The second metal layer may be composed of one type of metal material, or may be composed of two or more types of metal materials.

[0032] The second metal layer preferably contains at least one metal atom (M2) selected from the group consisting of aluminum, copper, iron, silver, gold, zinc, nickel, and tin. The metal atom (M2) is preferably at least one selected from the group consisting of aluminum, copper, and iron, and more preferably at least one selected from the group consisting of aluminum and copper.

[0033] The content of the metal atom (M2) may be, for example, 50 mass% or more, preferably 60 mass% or more, more preferably 70 mass% or more, and even more preferably 80 mass% or more, based on the total amount of the second metal layer, and may be 90 mass% or more, or even 100 mass%.

[0034] The second metal layer may be, for example, a metal foil. The thickness of the second metal layer is not particularly limited and may be, for example, 0.01 mm or more, preferably 0.02 mm or more, and more preferably 0.03 mm or more. The thickness of the second metal layer may be, for example, 5.0 mm or less, preferably 3.0 mm or less, and more preferably 1.0 mm or less.

[0035] The bonding surface (S2) of the second metal layer may be a roughened surface. The roughening method is not particularly limited, and any known roughening treatment can be used without particular limitation. Examples of roughening treatment include chemical etching, blasting, and buffing.

[0036] The conditions for the roughening treatment are not particularly limited, and for example, conditions may be appropriately selected so that the joining surface (S2) exhibits the surface roughness curve (C) described below.

[0037] It is preferable that the first metal layer and the second metal layer have a joint surface (S1 or S2) with the insulating layer that exhibits a surface roughness curve (C) with a reference length of 250 μm, an average element length (RSm) of 10 μm or more, and a maximum height (Rz) of 20 μm or less.

[0038] In the surface roughness curve (C), the mean element length (RSm) is preferably 15 μm or more, more preferably 20 μm or more. Although there is no particular upper limit to the mean element length (RSm), from the viewpoint of further improving the adhesion to the insulating layer at the joining surface and obtaining a circuit board with superior adhesion reliability, the mean element length (RSm) is, for example, 200 μm or less, preferably 150 μm or less, more preferably 100 μm or less.

[0039] In the surface roughness curve (C), the maximum height (Rz) is preferably 15 μm or less, more preferably 10 μm or less. Although there is no particular limitation on the lower limit of the maximum height (Rz), from the viewpoint of further improving the adhesion to the insulating layer at the bonding surface and obtaining a circuit board with more excellent adhesion reliability, the maximum height (Rz) is, for example, 0.1 μm or more, preferably 0.5 μm or more, more preferably 1.0 μm or more.

[0040] (insulating layer) The insulating layer may be, for example, a layer containing a cured insulating resin and an inorganic filler.

[0041] The insulating resin cured body may be, for example, a cured body of a resin component containing a thermosetting resin and a curing agent.

[0042] Examples of thermosetting resins include epoxy resins, silicone resins, phenolic resins, cyanate resins, melamine resins, urea resins, thermosetting polyimide resins, and unsaturated polyester resins. Of these, epoxy resins are preferred from the viewpoints of adhesiveness and electrical insulation.

[0043] The epoxy resin may be any resin that can be cured with a curing agent. Examples of epoxy resins include bisphenol A epoxy resins, bisphenol S epoxy resins, bisphenol F epoxy resins, hydrogenated bisphenol A epoxy resins, polypropylene glycol epoxy resins, polytetramethylene glycol epoxy resins, naphthalene epoxy resins, phenylmethane epoxy resins, tetrakisphenolmethane epoxy resins, biphenyl epoxy resins, epoxy resins having a triazine ring, bisphenol A alkylene oxide adduct epoxy resins, dicyclopentadiene epoxy resins, cresol novolac epoxy resins, and phenol novolac epoxy resins. One type of epoxy resin may be used alone, or two or more types may be used in combination.

[0044] The curing agent may be any curing agent capable of curing the thermosetting resin, and may be appropriately selected from known curing agents depending on the type of thermosetting resin.

[0045] When the thermosetting resin is an epoxy resin, examples of the curing agent (curing agent for epoxy resin) include amine-based curing agents, phenol-based curing agents, acid anhydride-based curing agents, and thiol-based curing agents.

[0046] The amine-based curing agent may be any curing agent that has an amino group and can cure epoxy resins. Examples of the amine-based curing agent include aromatic amine-based curing agents, aliphatic amine-based curing agents, and dicyandiamide.

[0047] As the amine-based curing agent, any amine-based curing agent known as a curing agent for epoxy resins can be used without any particular limitation. Commercially available amine-based curing agents may be used, and for example, aliphatic polyamines, alicyclic polyamines, aromatic polyamines, etc. can be suitably used.

[0048] The phenolic curing agent may be any curing agent that has a plurality of phenolic hydroxyl groups and is capable of curing an epoxy resin. Examples of the phenolic curing agent include novolac-type phenolic resins and resol-type phenolic resins.

[0049] As the phenolic curing agent, any phenolic curing agent known as a curing agent for epoxy resins can be used without any particular limitation. Commercially available phenolic curing agents may be used, and suitable examples include phenol novolac, xylylene novolac, and bisphenol A novolac.

[0050] The acid anhydride curing agent may be any curing agent that has a structure formed by dehydration condensation of two carboxyl groups and is capable of curing epoxy resins. Examples of the acid anhydride curing agent include aliphatic acid anhydrides and aromatic acid anhydrides.

[0051] As the acid anhydride curing agent, any acid anhydride curing agent known as a curing agent for epoxy resins can be used without any particular limitation. As the acid anhydride curing agent, commercially available products may be used, and for example, phthalic anhydride derivatives, maleic anhydride derivatives, etc. can be suitably used.

[0052] The thiol-based curing agent may be any curing agent that has a plurality of mercapto groups and is capable of curing epoxy resins. Examples of the thiol-based curing agent include an aliphatic thiol-based curing agent and an aromatic thiol-based curing agent.

[0053] As the thiol-based curing agent, any thiol-based curing agent known as a curing agent for epoxy resins can be used without any particular limitation. As the thiol-based curing agent, commercially available products may be used, and for example, aliphatic polythioethers, aliphatic polythioesters, aromatic-containing polythioethers, etc. can be suitably used.

[0054] The content of the curing agent in the resin component may be, for example, 1.0 part by mass or more, preferably 10 parts by mass or more, more preferably 20 parts by mass or more, or even 50 parts by mass or more, relative to 100 parts by mass of the thermosetting resin. The content of the curing agent may be, for example, 300 parts by mass or less, preferably 200 parts by mass or less, more preferably 150 parts by mass or less, or even 0 parts by mass, relative to 100 parts by mass of the thermosetting resin.

[0055] The resin component may further contain other components in addition to those described above, such as a curing accelerator, a discoloration inhibitor, a surfactant, a coupling agent, a colorant, a viscosity modifier, an antioxidant, an ion scavenger, etc., as necessary.

[0056] The content of other components in the resin component may be, for example, 10% by mass or less, preferably 5% by mass or less, or even 0% by mass. That is, the total amount of the thermosetting resin and curing agent in the resin component may be, for example, 90% by mass or more, preferably 95% by mass or more, or even 100% by mass.

[0057] The insulating resin cured body is a cured body of a resin component.

[0058] The glass transition point of the cured insulating resin is preferably 125°C or higher, and more preferably 150°C or higher. This improves the insulation resistance of the cured product at high temperatures, allowing the formation of an insulating layer with better insulating reliability at high temperatures. There is no particular upper limit for the glass transition point of the cured insulating resin, but it is preferably 400°C or lower, and more preferably 350°C or lower. This further improves the flexibility of the cured product, allowing the formation of an insulating layer with even better stress relaxation properties.

[0059] In this specification, the glass transition temperature of the insulating resin cured product refers to a value measured by the following method. <Method for measuring glass transition temperature> (1) Preparation of measurement samples The insulating resin cured body is cut into a plate of 0.1 mm x 5 mm x 40 mm size to prepare a measurement sample. (2) Measurement of glass transition temperature Using a dynamic viscoelasticity measuring device ("RSA 3" manufactured by T&A Instruments), the loss tangent (tanδ) was measured in the temperature range of 30°C to +300°C under conditions of a frequency of 10 Hz and a heating rate of 10°C / min, and the temperature at which the loss tangent value was maximized was determined to be the glass transition point.

[0060] The content of the cured insulating resin in the insulating layer may be, for example, 1.0% by volume or more, preferably 10% by volume or more, more preferably 20% by volume or more, based on the total volume of the insulating layer, and the content of the cured insulating resin in the insulating layer may be, for example, 99% by volume or less, preferably 90% by volume or less, more preferably 80% by volume or less, based on the total volume of the insulating layer.

[0061] Examples of inorganic fillers include inorganic fillers made of aluminum oxide, silica, aluminum nitride, silicon nitride, boron nitride, and the like.

[0062] From the viewpoint of suppressing deterioration of electrical insulation properties in a high-temperature, high-humidity environment due to hydrolysis of the inorganic material, the inorganic filler preferably contains, as a main component, an inorganic material selected from the group consisting of aluminum oxide, silica, silicon nitride, and boron nitride. The content of the inorganic material in the inorganic filler is preferably 60 mass% or more, more preferably 70 mass% or more, and even more preferably 80 mass% or more, based on the total amount of the inorganic filler.

[0063] For example, if the inorganic filler contains a large amount of aluminum nitride, hydrolysis of the aluminum nitride may occur in a high-temperature, high-humidity environment, resulting in a decrease in electrical insulation. Therefore, the content of aluminum nitride in the inorganic filler is preferably 40 mass% or less, more preferably 30 mass% or less, and even more preferably 20 mass% or less, based on the total amount of the inorganic filler. As described above, by using an inorganic material selected from the group consisting of aluminum oxide, silica, silicon nitride, and boron nitride as the main component, the decrease in electrical insulation caused by such hydrolysis is significantly suppressed.

[0064] The shape of the inorganic filler is not particularly limited, and may be particulate, scale-like, polygonal, or the like, with particulate shape being preferred.

[0065] The maximum particle size of the inorganic filler may be, for example, 250 μm or less, preferably 200 μm or less, and more preferably 150 μm or less. This tends to further improve the electrical insulation of the insulating layer. The minimum particle size of the inorganic filler is not particularly limited, but from the viewpoint of further improving the thermal conductivity of the insulating layer, it may be, for example, 0.05 μm or more, preferably 0.1 μm or more. In this specification, the maximum particle size and minimum particle size of the inorganic filler refer to the d90 diameter and d10 diameter in the volume-based particle size distribution, which are measured using a laser diffraction particle size distribution analyzer.

[0066] The content of the inorganic filler in the insulating layer may be, for example, 1.0% by volume or more, preferably 10% by volume or more, more preferably 20% by volume or more, based on the total volume of the insulating layer, and may be, for example, 99% by volume or less, preferably 90% by volume or less, more preferably 80% by volume or less, based on the total volume of the insulating layer.

[0067] The insulating layer can be formed, for example, by curing a coating of a composition containing the above-mentioned resin component and inorganic filler.

[0068] The coating film can be cured, for example, by heat treatment. The heat treatment may be performed in one step or two steps. By performing the heat treatment in two steps, an insulating layer can be formed via a semi-cured coating film. The temperature and time of the heat treatment may be appropriately changed depending on the types of thermosetting resin and curing agent, etc.

[0069] When the heat treatment is carried out in one step, the heat treatment temperature may be, for example, 40 to 250°C, preferably 70 to 180°C, and the heat treatment time may be, for example, 0.5 to 48 hours, preferably 1 to 6 hours.

[0070] When the heat treatment is carried out in two stages, the temperature of the first stage (first heat treatment) may be, for example, 40 to 150°C, preferably 50 to 100°C, and the time of the first heat treatment may be, for example, 0.2 to 8 hours, preferably 0.5 to 5 hours. The temperature of the second stage (second heat treatment) may be, for example, 70 to 250°C, preferably 120 to 180°C, and the time of the heat treatment may be, for example, 0.5 to 9 hours, preferably 1 to 6 hours.

[0071] The insulating layer may be formed, for example, by placing a coating film of the composition or a semi-cured product of the coating film between a first metal layer and a second metal layer and applying heat and pressure. The pressure application conditions are not particularly limited. The pressure may be applied at a surface pressure of, for example, 1 MPa or more, preferably 5 MPa or more, and more preferably 8 MPa or more. The pressure may also be applied at a surface pressure of, for example, 30 MPa or less, preferably 25 MPa or less, and more preferably 20 MPa or less.

[0072] The thickness of the insulating layer is not particularly limited, but from the viewpoint of electrical insulation, it may be, for example, 30 μm or more, preferably 50 μm or more, more preferably 80 μm or more, and from the viewpoint of thermal resistance, the thickness of the insulating layer may be, for example, 500 μm or less, preferably 300 μm or less, more preferably 200 μm or less.

[0073] Fig. 1 is a cross-sectional view showing a preferred embodiment of a laminate. The laminate 10 shown in Fig. 1 includes a first metal layer 1, an insulating layer 2 disposed on the first metal layer 1, and a second metal layer 3 disposed on the insulating layer 2. The first metal layer 1 has a bonding surface S1 with the insulating layer 2. The second metal layer 3 has a bonding surface S2 with the insulating layer 2.

[0074] At least one of the joining surface S1 and the joining surface S2 exhibits the above-mentioned surface roughness curve (C).

[0075] The second metal layer 3 of the laminate 10 is processed into a predetermined shape to form a metal circuit portion, thereby making it possible to easily manufacture a circuit board.

[0076] It is preferable that the portion of the bonding surface S1 of the first metal layer 1 facing the metal circuit portion exhibits the above-mentioned surface roughness curve. It is also preferable that the portion of the bonding surface S2 of the second metal layer 3 remaining as the metal circuit portion exhibits the above-mentioned surface roughness curve (C). In other words, it is preferable that the metal circuit portion is formed at a position facing the portion of the bonding surface S1 that exhibits the above-mentioned surface roughness curve (C). It is also preferable that the metal circuit portion is formed so that the portion of the bonding surface S2 that exhibits the above-mentioned surface roughness curve (C) remains.

[0077] There are no particular limitations on the method for forming the metal circuit portion, and any known processing method may be used.

[0078] [Circuit board] The circuit board of this embodiment includes a metal layer, an insulating layer disposed on the metal layer, and a metal circuit portion disposed on the insulating layer.

[0079] In the circuit board of this embodiment, at least one of the bonding surface (S1) of the metal layer with the insulating layer and the bonding surface (S3) of the metal circuit portion with the insulating layer exhibits a surface roughness curve (C) having a reference length of 250 μm, an average element length RSm of 10 μm or more, and a maximum height Rz of 20 μm or less.

[0080] The circuit board of this embodiment has excellent insulation reliability (particularly, the effect of suppressing deterioration of electrical insulation over time) under conditions of high voltage application. Although the reason why the circuit board of this embodiment exhibits such an effect is not necessarily clear, it is thought that this is because by roughening at least one of the metal layer and the metal circuit portion so as to exhibit the above-mentioned surface roughness curve (C), electric field concentration during high voltage application is suppressed, and a decrease in insulation reliability due to electric field concentration is suppressed.

[0081] The circuit board of this embodiment may be manufactured by removing a portion of the second metal layer of the above-described laminate.

[0082] In the circuit board of this embodiment, the surface roughness curve (C) may be the same as the surface roughness curve (C) in the above-mentioned laminate.

[0083] The metal layer in the circuit board of this embodiment may be the same as the first metal layer in the laminate described above.

[0084] The insulating layer in the circuit board of this embodiment may be the same as the insulating layer in the laminate described above.

[0085] The metal circuit portion in the circuit board of this embodiment may be the remainder obtained by removing a portion of the second metal layer in the laminate described above. That is, the material and thickness of the metal circuit portion may be the same as the material and thickness of the second metal layer.

[0086] Fig. 2 is a cross-sectional view showing a preferred embodiment of a circuit board. The circuit board 20 shown in Fig. 2 is a circuit board manufactured from the laminate shown in Fig. 1, and includes a first metal layer 1, an insulating layer 2 disposed on the first metal layer 1, and a metal circuit portion 4 disposed on the insulating layer 2. The first metal layer 1 has a bonding surface S1 with the insulating layer 2. The metal circuit portion 4 has a bonding surface S3 with the insulating layer 2.

[0087] At least one of the joining surface S1 and the joining surface S3 exhibits the above-mentioned surface roughness curve (C).

[0088] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

[0089] The present invention may relate to a method for producing a laminate, the method comprising: a first preparatory step of preparing a first metal layer having a roughened surface in which the average element length RSm in a surface roughness curve having a reference length of 250 μm is 10 μm or more and the maximum height Rz is 20 μm or less; a second preparatory step of preparing a second metal layer having a roughened surface in which the average element length RSm in a surface roughness curve having a reference length of 250 μm is 10 μm or more and the maximum height Rz is 20 μm or less; a third preparatory step of preparing a composition containing a resin component containing a thermosetting resin and a curing agent and an inorganic filler; an arrangement step of arranging a coating film of the composition or a semi-cured product thereof between the first metal layer and the second metal layer arranged so that the roughened surfaces face each other; and a heating and pressing step of forming an insulating layer by heating and pressing to obtain a laminate comprising the first metal layer, the insulating layer, and the second metal layer.

[0090] The first preparation step may be a step of roughening one surface of a metal layer to form a first metal layer, or a step of measuring a surface roughness curve of a metal layer having a roughened surface, the roughened surface having a reference length of 250 μm, and selecting a first metal layer based on the average length RSm and maximum height Rz of elements in the surface roughness curve.

[0091] The second preparation step may be a step of roughening one surface of the metal layer to form a second metal layer, or a step of measuring a surface roughness curve of a metal layer having a roughened surface, the roughened surface having a reference length of 250 μm, and selecting a second metal layer based on the average length RSm and maximum height Rz of elements in the surface roughness curve.

[0092] The present invention may also relate to a sorting method for sorting a laminate comprising a first metal layer, an insulating layer disposed on the first metal layer, and a second metal layer disposed on the insulating layer.

[0093] The above-mentioned selection method may include a first selection step of measuring a surface roughness curve with a reference length of 250 μm for the joint surface (S1) of the first metal layer with the insulating layer, and selecting laminates whose element average length RSm in the surface roughness curve is 10 μm or more and whose maximum height Rz is 20 μm or less.

[0094] The above-mentioned selection method may also include a second selection step of measuring a surface roughness curve with a reference length of 250 μm for the joint surface (S2) of the second metal layer with the insulating layer, and selecting laminates whose element average length RSm in the surface roughness curve is 10 μm or more and whose maximum height Rz is 20 μm or less.

[0095] The above-mentioned selection method may include one of a first selection step and a second selection step, or may include both.

[0096] The present invention may further relate to a sorting method for sorting circuit boards having a metal layer, an insulating layer disposed on the metal layer, and a metal circuit portion disposed on the insulating layer.

[0097] The above-mentioned selection method may include a first selection step of measuring a surface roughness curve having a reference length of 250 μm for the joint surface (S1) of the metal layer with the insulating layer, and selecting circuit boards having an average element length RSm of 10 μm or more and a maximum height Rz of 20 μm or less in the surface roughness curve.

[0098] The above-mentioned selection method may also include a second selection step of measuring a surface roughness curve with a reference length of 250 μm for the joint surface (S3) of the metal circuit portion with the insulating layer, and selecting circuit boards having an element average length RSm of 10 μm or more and a maximum height Rz of 20 μm or less in the surface roughness curve.

[0099] The above-mentioned selection method may include one of a first selection step and a second selection step, or may include both. [Example]

[0100] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0101] Example 1 <Preparation of Composition> The thermosetting resin used was naphthalene-type epoxy resin HP-4032D (DIC Corporation, specific gravity 1.2 g / cm 3 ) 100 parts by mass, and phenol novolac resin VH-4150 (DIC Corporation, specific gravity 1.1 g / cm) as a curing agent. 3 ) and 12.4 parts by mass of boron nitride (manufactured by Denka Co., Ltd., specific gravity 2.27 g / cm 3 ) 214.8 parts by mass, and a wetting and dispersing agent DISPER BYK111 (manufactured by BYK-Chemie, specific gravity 1.1 g / cm 3 ) 0.7 parts by mass, and TPP (manufactured by Hokko Chemical Co., Ltd., specific gravity 1.1 g / cm) as a curing accelerator 3 ) 0.6 parts by mass, and imidazole compound 2PHZ-PW (manufactured by Shikoku Chemicals Corporation, specific gravity 1.1 g / cm 3 ) and 1.0 parts by mass of the hydroxybenzoate were mixed and stirred for 15 minutes using a planetary mixer to prepare a composition. The volumetric contents of the components in the composition were 43.6% by volume of naphthalene-type epoxy resin, 5.9% by volume of phenol novolac resin, 49.4% by volume of boron nitride, 0.3% by volume of wetting and dispersing agent, 0.3% by volume of curing accelerator, and 0.5% by volume of imidazole compound.

[0102] <Preparation of laminate> The resulting composition was applied to a 0.038 mm thick polyethylene terephthalate (PET) film so that the thickness after semi-curing was 0.20 mm, and then heated and dried at 100°C for 70 minutes to produce a semi-cured product (B-stage sheet). The resulting semi-cured product was peeled from the PET film and placed on the roughened surface of a metal plate (2.0 mm thick copper plate). Next, the roughened surface of metal foil (0.5 mm thick copper foil) was placed on the semi-cured product, and the mixture was heated and cured at 180°C for 410 minutes while applying a surface pressure of 10 MPa using a press to obtain a laminate. The thickness of the insulating layer in the laminate was 125 μm.

[0103] The surface roughness curves of the roughened surfaces of the metal plate and metal foil were measured using the method described below, and the average length RSm and maximum height Rz of the elements were determined. The results are shown in Table 1. The glass transition temperature of the cured resin that constitutes the insulating layer was also measured. The results are shown in Table 1.

[0104] <Creating a circuit board> After masking predetermined positions on the metal foil of the laminate with an etching resist, the copper foil was etched using a sulfuric acid-hydrogen peroxide mixed solution as an etching solution. The etching resist was removed, and the substrate was washed and dried to obtain a metal base circuit board with a circular electrode (copper foil) with a diameter of 20 mm. The insulation reliability of the obtained metal base circuit board was evaluated using the following method. The results are shown in Table 1.

[0105] <Surface roughness curve measurement> The roughened surfaces of the metal plate and metal foil were observed using a laser microscope VK-X1000 (Keyence Corporation), and a surface roughness curve with a reference length of 250 μm was obtained using line roughness measurement with data analysis software, and RSm and Rz were calculated using the method specified in JIS B 0601. The measurement conditions were an objective lens set to x50 and an eyepiece set to approximately x20, and data was obtained from one location.

[0106] <Evaluation of insulation reliability> The obtained metal base circuit board was subjected to a high-temperature, high-voltage bias test (Vt) under test conditions in which a DC voltage of 10 kV was applied between the circular electrode and the metal plate in a 125°C environment. The endurance time was determined as the time from the start of voltage application to the point at which the leakage current value measured with a voltage resistance tester reached 10 mA or more. If the endurance time was 50 minutes or more, it could be said that the metal base circuit board had excellent insulation reliability in a high-temperature environment.

[0107] (Examples 2 to 11 and Comparative Examples 1 and 2) Laminates and circuit boards were produced in the same manner as in Example 1, except that metal plates and metal foils having the average element length RSm and maximum height Rz on the roughened surface shown in Table 1, Table 2, or Table 3 were used. The insulation reliability of the obtained circuit boards was evaluated in the same manner as in Example 1. The results are shown in Table 1, Table 2, or Table 3.

[0108] Example 12 <Preparation of Composition> The thermosetting resin used was bisphenol A epoxy resin EXA-850CRP (DIC Corporation, specific gravity 1.2 g / cm 3 ) 100 parts by mass, and diaminophenylmethane H-84B (manufactured by Acmex Corporation, specific gravity 1.1 g / cm) as a curing agent. 3 ) 34 parts by mass, and alumina AS30-1 (manufactured by Showa Denko K.K., specific gravity 3.95 g / cm 3 The resulting mixture was stirred and mixed for 15 minutes using a planetary mixer to prepare a composition. The volumetric content of each component in the composition was 24.4% by volume for bisphenol A epoxy resin, 9.0% by volume for curing agent, and 66.6% by volume for alumina AS30-1.

[0109] <Preparation of laminate> The resulting composition was applied to a 0.038 mm thick polyethylene terephthalate (PET) film so that the thickness after semi-curing was 0.20 mm, and then heated and dried at 100°C for 20 minutes to produce a semi-cured product (B-stage sheet). The resulting semi-cured product was peeled from the PET film and placed on the roughened surface of a metal plate (a 1.5 mm thick aluminum plate). Next, the roughened surface of metal foil (0.5 mm thick copper foil) was placed on the semi-cured product, and the mixture was heated and cured at 180°C for 410 minutes while applying a surface pressure of 10 MPa using a press to obtain a laminate. The thickness of the insulating layer in the laminate was 130 μm.

[0110] The surface roughness curves of the roughened surfaces of the metal plate and metal foil were measured in the same manner as in Example 1, and the average length RSm and maximum height Rz of the elements were determined. The results are shown in Table 2. The glass transition temperature of the cured resin constituting the insulating layer was also measured. The results are shown in Table 2.

[0111] <Creating a circuit board> After masking predetermined positions on the metal foil of the laminate with an etching resist, the copper foil was etched using a sulfuric acid-hydrogen peroxide mixed solution as an etching solution. The etching resist was removed, and the substrate was washed and dried to obtain a metal base circuit board having a circular electrode (copper foil) with a diameter of 20 mm. The insulation reliability of the obtained metal base circuit board was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0112] [Table 1]

[0113] [Table 2]

[0114] [Table 3] [Explanation of symbols]

[0115] 1...first metal layer, 2...insulating layer, 3...second metal layer, 4...metal circuit portion, 10...laminated body, 20...circuit board.

Claims

1. a first metal layer; an insulating layer disposed on the first metal layer; a second metal layer disposed on the insulating layer; Equipped with the insulating layer contains an insulating resin cured body and an inorganic filler, the insulating resin cured body is a cured body of a resin component containing an epoxy resin and a curing agent such that the total amount of the epoxy resin and the curing agent is 90 mass % or more, A laminate, wherein at least one of the bonding surface of the first metal layer with the insulating layer and the bonding surface of the second metal layer with the insulating layer exhibits a surface roughness curve having a reference length of 250 μm, an average element length RSm of 10 μm or more, and a maximum height Rz of 20 μm or less.

2. The laminate according to claim 1 , wherein both a bonding surface of the first metal layer with the insulating layer and a bonding surface of the second metal layer with the insulating layer exhibit the surface roughness curve.

3. The laminate according to claim 1 or 2, wherein the insulating layer has a thickness of 30 μm or more.

4. The laminate according to any one of claims 1 to 3, wherein the first metal layer and the second metal layer contain 60 mass% or more of at least one metal atom selected from the group consisting of aluminum, copper, iron, silver, gold, zinc, nickel, and tin.

5. a metal layer, an insulating layer disposed on the metal layer, and a metal circuit portion disposed on the insulating layer; the insulating layer contains an insulating resin cured body and an inorganic filler, the insulating resin cured body is a cured body of a resin component containing an epoxy resin and a curing agent such that the total amount of the epoxy resin and the curing agent is 90 mass % or more, A circuit board, wherein at least one of the bonding surface of the metal layer with the insulating layer and the bonding surface of the metal circuit portion with the insulating layer exhibits a surface roughness curve having a reference length of 250 μm, an average element length RSm of 10 μm or more, and a maximum height Rz of 20 μm or less.

6. The circuit board according to claim 5 , wherein both a joint surface of the metal layer with the insulating layer and a joint surface of the metal circuit portion with the insulating layer exhibit the surface roughness curve.

7. A step of preparing a laminate according to any one of claims 1 to 4; removing a portion of the first metal layer or a portion of the second metal layer of the laminate to form a metal circuit portion; A method for manufacturing a circuit board, comprising:

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