Resin composition, prepreg, film with resin, metal foil sheet with resin, metal-clad laminate, and printed wiring board

Abstract

The resin composition of the present disclosure contains a curable resin. When a thermal gravimetric analysis is performed on a cured product of the resin composition at a temperature increase rate of 90°C / minute from 30°C to 800°C, the amount of exhaust gas generated from the cured product at 30°C to 550°C is less than 27% by mass relative to the total mass of the cured product.

Description

Technical Field

[0001] This disclosure generally relates to resin compositions, prepregs, resin-containing films, resin-containing metal foil sheets, metal-coated laminates, and printed circuit boards. More specifically, this disclosure relates to resin compositions containing curable resins, prepregs, resin-containing films, resin-containing metal foil sheets, metal-coated laminates, and printed circuit boards. Background Technology

[0002] Patent Document 1 discloses an epoxy resin composition. The epoxy resin composition contains the following as essential components: (a) a phenolic varnish epoxy resin, (b) a novolac phenolic resin, and (c) a crosslinked butadiene acrylonitrile elastomer.

[0003] Patent Document 1 also discloses an epoxy resin prepreg. This epoxy resin prepreg is formed by preparing a varnish containing an epoxy resin composition, impregnating a fiber substrate (base member) with the varnish, and drying the varnish.

[0004] In addition, Patent Document 1 discloses a multilayer printed circuit board. This multilayer printed circuit board is formed by using the epoxy resin prepreg as a prepreg for bonding the inner circuit board and the outer metal foil sheet together.

[0005] Through-holes are typically created to penetrate multiple layers of printed circuit boards. Through-holes are holes used to make electrical connections through a printed circuit board in the thickness direction.

[0006] Currently, through-holes are mostly created using laser cutting. This is because laser cutting makes it easier to create through-holes with small diameters compared to drilling. Creating through-holes with such small diameters increases the density of multilayer printed circuit boards, thereby helping to reduce the size and weight of electronic devices.

[0007] However, the use of laser cutting to create holes through the multilayer printed circuit board in Patent Document 1 increases the likelihood of leaving long overhangs, which is disadvantageous.

[0008] For example, laser-cut holes are performed on the multilayer printed circuit board of Patent Document 1 using a direct method as follows. Specifically, first, a laser beam is used to irradiate the outer metal foil sheet to create a through-hole penetrating the outer metal foil sheet. In this state, the laser beam is continuously used to irradiate the insulating layer (i.e., the cured prepreg used for bonding) to provide non-through-holes, the bottom surface of which is the inner circuit board. In this case, the inner diameter of the through-hole in the outer metal foil sheet tends to be smaller than the inner diameter of the non-through-hole in the insulating layer. In this case, a portion of the outer metal foil sheet protrudes towards the center of the through-hole as a burr or overhang. Such a protrusion is called an "overhang".

[0009] In this situation, if the overhang is too long, the chemical solution used in the subsequent destaining process will be obstructed and prevented from fully reaching any corner of the hole, making it difficult to remove contaminants from the bottom surface of non-through holes. Furthermore, this also prevents sufficiently uniform and smooth electrodeposition of the plating, thereby increasing the likelihood of plating porosity. Therefore, this results in a significant decrease in the reliability of the through-hole connection. This is why a process step is required to remove the overhang if it is too long. However, this means increased man-hours and therefore tends to lead to a decrease in productivity.

[0010] Citation List

[0011] Patent documents

[0012] Patent Document 1: JP H10-077392 A Summary of the Invention

[0013] Therefore, one object of this disclosure is to provide resin compositions, prepregs, resin-containing films, resin-containing metal foil sheets, metal-coated laminates, and printed circuit boards, all of which reduce the likelihood of overhangs associated with laser-cut holes.

[0014] According to one aspect of this disclosure, the resin composition contains a curable resin. When the cured product of the resin composition is subjected to thermogravimetric analysis at a temperature increasing from 30°C to 800°C at a heating rate of 90°C / min, the amount of outgas discharged from the cured product at temperatures ranging from 30°C to 550°C is less than 27% by mass relative to the total mass of the cured product.

[0015] The prepreg according to another aspect of this disclosure comprises: a substrate; and a resin layer comprising the resin composition or a semi-cured product of the resin composition. The resin composition or the semi-cured product is impregnated into the substrate.

[0016] According to another aspect of this disclosure, a resin-containing film comprises: a resin layer containing the resin composition or a semi-cured product of the resin composition; and a support film supported thereon of the resin layer.

[0017] According to another aspect of this disclosure, a resin-containing metal foil sheet includes: a resin layer comprising the resin composition or a semi-cured product of the resin composition; and a metal foil sheet bonded to the resin layer.

[0018] According to another aspect of this disclosure, a metal-clad laminate includes: an insulating layer comprising a cured product of the resin composition or a cured product of the prepreg; and a metal layer bonded to the insulating layer.

[0019] A printed circuit board according to another aspect of this disclosure includes: an insulating layer comprising a cured product of the resin composition or a cured product of the prepreg; and conductor lines formed on the insulating layer. Attached Figure Description

[0020] Figure 1 This is a schematic cross-sectional view illustrating a prepreg according to an exemplary embodiment of the present disclosure;

[0021] Figure 2 A is a schematic cross-sectional view illustrating a film having resin (and no protective film) according to an exemplary embodiment of the present disclosure;

[0022] Figure 2 B is a schematic cross-sectional view illustrating a film having a resin (and a protective film) according to an exemplary embodiment of the present disclosure;

[0023] Figure 3 This is a schematic cross-sectional view showing a metal foil sheet having resin according to an exemplary embodiment of the present disclosure;

[0024] Figure 4 This is a schematic cross-sectional view showing a metal-clad laminate (double-sided metal-clad laminate) according to an exemplary embodiment of the present disclosure;

[0025] Figure 5 A is a schematic cross-sectional view illustrating a printed circuit board (without interlayer connections) according to an exemplary embodiment of the present disclosure;

[0026] Figure 5 B is a schematic cross-sectional view illustrating a printed circuit board (with interlayer connections) according to an exemplary embodiment of the present disclosure;

[0027] Figure 6 This is a diagram showing the relationship between the exhaust and the overhang in the temperature range of 30°C to 550°C;

[0028] Figure 7 This is a diagram showing the relationship between exhaust and overhang in a temperature range of 30°C to 600°C; and

[0029] Figure 8 This demonstrates how to leave overhangs by laser-cutting holes. Detailed Implementation

[0030] 1. Summary

[0031] First, refer to Figure 8 Describes laser-cutting. An insulating layer 40 is inserted between two metal layers 41 arranged along the thickness direction. The two metal layers 41 are a first metal layer 411 and a second metal layer 412. That is, the first metal layer 411, the insulating layer 40, and the second metal layer 412 are stacked sequentially on top of each other in the thickness direction. The metal layers 41 are not limited to any specific layer, but can be, for example, layers containing copper. The insulating layer 40 is a layer containing resin and having electrical insulation properties. The insulating layer 40 has a thickness T.

[0032] A through-hole 43 is formed through the first metal layer 411 by irradiating it with a laser beam L along its thickness direction. In this state, the insulating layer 40 is continuously irradiated with the laser beam L to provide a non-through-hole 44 within the insulating layer 40. The laser beam L is not limited to any particular laser beam, but can be, for example, a CO2 laser beam or a YAG laser beam. The laser cutting method is performed directly in this embodiment, but it can also be performed using a conformal mask method.

[0033] The through-hole 43 has an inner diameter D1. The non-through-hole 44 is a bottomed hole whose bottom surface is the surface of the second metal layer 412. The non-through-hole 44 has a depth T. The non-through-hole 44 is a tapered hole, and its inner diameter decreases from the first metal layer 411 towards the second metal layer 412. The opening of the non-through-hole 44 has an inner diameter (maximum inner diameter) D2. The bottom surface of the non-through-hole 44 has an inner diameter (minimum inner diameter) D3. Alternatively, the non-through-hole 44 can also be a straight hole. In this case, the non-through-hole 44 has a constant inner diameter (i.e., D2 = D3). Still alternatively, the non-through-hole 44 can also be an inverted tapered hole. In this case, the inner diameter of the non-through-hole 44 increases from the first metal layer 411 towards the second metal layer 412. The opening of the non-through-hole 44 has an inner diameter (minimum inner diameter) D2. The bottom surface of the non-through hole 44 has an inner diameter (maximum inner diameter) D3.

[0034] In the prior art, the inner diameter D1 of the through hole 43 of the first metal layer 411 tends to be smaller than the inner diameter D2 of the opening of the non-through hole 44 of the insulating layer 40. In this case, a portion of the first metal layer 411 protrudes towards the center of the through hole 43 as a burr or eave. This portion is called the "overhang 6".

[0035] The inventors focused on venting from the insulating layer 40 and related to laser-cut holes, while simultaneously investigating ways to shorten the length W of the overhang 6. The inventors performed thermogravimetric analysis (TGA) to measure the amount of venting. As a result, the inventors found a correlation between the amount of venting and the length W of the overhang 6. Generally, the inventors found that the smaller the amount of venting, the shorter the overhang 6 tends to be, and the larger the amount of venting, the longer the overhang 6 tends to be. Therefore, the inventors further investigated to find conditions for reducing the likelihood of leaving the overhang 6.

[0036] In other words, the resin composition according to this embodiment can be used to form such as Figure 8 The insulating layer 40 is shown. This resin composition contains a curable resin. When the cured product of the resin composition is subjected to thermogravimetric analysis at a temperature increase rate of 90°C / min from 30°C to 800°C, the amount of exhaust gas emitted from the cured product at temperatures ranging from 30°C to 550°C is less than 27% by mass relative to the total mass of the cured product. Therefore, using the resin composition according to this embodiment to form the insulating layer 40 can reduce the likelihood of leaving overhangs 6, which are typically associated with laser-cut holes (see...). Figure 6 In other words, compared to existing technologies, this allows for a reduction in the length W of the overhang 6.

[0037] 2. Details

[0038] Next, the resin composition according to this embodiment will be described in detail. Then, the prepreg 1, the resin-containing film 2, the resin-containing metal foil sheet 3, the metal-coated laminate 4, and the printed circuit board 5 according to this embodiment will be described in detail with reference to the accompanying drawings.

[0039] (1) Resin composition

[0040] The resin composition according to this embodiment contains a curable resin. The resin composition according to this embodiment exhibits the following thermophysical properties when its cured product is subjected to thermogravimetric analysis (TGA). Specifically, when the cured product of the resin composition according to this embodiment is subjected to TGA at a temperature increase rate of 90°C / min from 30°C to 800°C, the amount of exhaust gas emitted from the cured product at temperatures ranging from 30°C to 550°C is less than 27% by mass relative to the total mass of the cured product. The TGA can be performed, for example, in a nitrogen atmosphere. The components of the exhaust gas can be, for example, low molecular weight components generated from the decomposition of a portion of the cured product.

[0041] In this case, for example, in Figure 8During the laser cutting process shown, when the temperature of the first metal layer 411 (e.g., specifically copper foil) irradiated by the laser beam L reaches its melting point (e.g., the melting point of copper is approximately 1085°C), the temperature of 550°C is approximately equal to the temperature of the insulating layer 40 directly below the first metal layer 411. It can be seen that setting the amount of exhaust gas discharged from the cured product at temperatures ranging from 30°C to 550°C to less than 27% by mass reduces the likelihood that the insulating layer 40 directly below the first metal layer 411 will be removed. This reduces the difference between the inner diameter D1 of the through hole 43 in the first metal layer 411 and the inner diameter D2 of the opening of the non-through hole 44 in the insulating layer 40. In other words, this shortens the length W of the overhang 6. Therefore, this reduces the likelihood of leaving the overhang 6, which is typically associated with laser cutting.

[0042] Furthermore, setting the amount of exhaust gas emitted from the cured product at temperatures ranging from 30°C to 550°C to less than 27% by mass also improves the flammability of the cured product. Generally, combustible material, oxygen, and a temperature equal to or above the ignition point are the three essential elements for combustion. Exhaust gas is a low molecular weight component and can therefore be classified as combustible material. However, because the amount of exhaust gas emitted from the cured product at temperatures ranging from 30°C to 550°C is relatively small, as described above, the cured product is less flammable. In other words, this improves the flammability of the cured product.

[0043] Preferably, when thermogravimetric analysis is performed under the same conditions as described above, the amount of exhaust gas discharged from the cured product at temperatures ranging from 30°C to 600°C is less than 30% by mass relative to the total mass of the cured product. This further reduces the possibility of leaving overhangs 6.

[0044] The curable resin contained in the resin composition is not limited to any specific curable resin, as long as the resin composition can exhibit such thermophysical properties. The curable resin is a prepolymer and may contain a main reagent and a curing agent. Optionally, the resin composition may also contain additional components besides the curable resin.

[0045] The curable resin preferably comprises at least one compound selected from the group consisting of: epoxy compounds, maleimide compounds, phenolic compounds, amide compounds, and cyanate ester compounds. This further reduces the likelihood of leaving the overhang 6 compared to a resin composition containing only curable resins other than those listed above.

[0046] Epoxy compounds are one of the main reagents and are compounds having at least one (preferably two or more) epoxy groups in their molecules. Specific examples of epoxy compounds include, but are not limited to: phenolic varnish epoxy compounds, naphthol-aryl epoxide compounds, biphenyl-aryl epoxide compounds, naphthyl epoxy resins, biphenyl epoxy resins, and dicyclopentadiene epoxy resins. Among these, phenolic varnish epoxy compounds and biphenyl-aryl epoxide compounds are particularly preferred. The epoxy equivalent of the epoxy compound is preferably equal to or greater than 150 g / eq and equal to or less than 350 g / eq.

[0047] Maleimide compounds are one of the main reagents and are compounds having at least one maleimide group in their molecule. Specific examples of maleimide compounds include, but are not limited to: phenolic varnish maleimide compounds (preferably phenylmethane maleimide), 4,4'-diphenylmethane bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, and bisphenol A diphenyl ether bismaleimide. Adding maleimide compounds to resin compositions can improve the flame retardancy of the cured product.

[0048] Phenolic compounds are curing agents and are compounds produced by polymerizing phenol and formaldehyde using an acidic or basic catalyst. Specific examples of phenolic compounds include, but are not limited to, phenolic varnish compounds and biphenyl-arylalkylphenol compounds. The hydroxyl equivalent of the phenolic compound is preferably equal to or greater than 100 g / eq and equal to or less than 250 g / eq.

[0049] Amide compounds are curing agents and are compounds having a structure in which a dehydration condensation reaction is initiated between an oxyacid and ammonia, a primary amine, or a secondary amine. Specific examples of amide compounds include, but are not limited to, dicyandiamide.

[0050] A cyanate ester compound is a curing agent and is a compound having at least one cyanate ester group in its molecule. Specific examples of cyanate ester compounds include, but are not limited to, cyanate ester compounds for phenolic varnishes. Adding a cyanate ester compound to a resin composition can improve the flame retardancy of the cured product.

[0051] The curable resin preferably comprises a biphenyl-aryl compound having a biphenyl-aryl structure. Specific examples of biphenyl-aryl compounds include, but are not limited to, biphenyl-aryl epoxides and biphenyl-aryl phenols. This further reduces the likelihood of leaving the overhang 6 compared to a resin composition containing only a curable resin other than a biphenyl-aryl compound.

[0052] Relative to a total of 100 parts by mass of the main reagent and the curing agent, the proportion of the main reagent is preferably equal to or greater than 60 parts by mass and equal to or less than 95 parts by mass. That is, relative to a total of 100 parts by mass of the main reagent and the curing agent, the proportion of the curing agent is preferably equal to or greater than 5 parts by mass and equal to or less than 40 parts by mass.

[0053] Specific examples of additional components other than the curable resin include, but are not limited to: catalysts, fillers, coupling agents (e.g., silane coupling agents), flame retardants, initiators, curing accelerators, defoamers, antioxidants, polymerization inhibitors, polymerization retardants, dispersants, leveling agents, heat stabilizers, antistatic agents, ultraviolet absorbers, dyes, pigments, and lubricants.

[0054] A catalyst is a compound that promotes the curing of a curable resin. Specific examples of catalysts include, but are not limited to, imidazole compounds, such as 2-ethyl-4-methylimidazolium, and metal soaps, such as zinc octanoate.

[0055] Fillers are additives that improve the processability of cured resin compositions or impart functionalities (such as flame retardancy). Specific examples of fillers include silica, alumina, titanium dioxide, and mica. The shape of the particles forming the filler is preferably spherical. The average particle size of the filler is preferably equal to or greater than 0.1 μm and equal to or less than 10 μm. Note that the average particle size herein refers to the particle size at the 50% cumulative value in the particle size distribution obtained by laser diffraction and scattering.

[0056] If the resin composition also contains fillers, the filler content (phr) is preferably equal to or greater than 50 parts by weight and equal to or less than 200 parts by weight relative to 100 parts by weight of the cured resin.

[0057] Note that, apart from the unavoidable presence of elastomers, the resin composition preferably does not contain elastomers. Specific examples of elastomers include, but are not limited to, acrylic rubbers. This reduces the increase in the amount of venting from the cured product. However, the resin composition may contain elastomers, provided that the amount of venting from the cured product at temperatures between 30°C and 550°C during thermogravimetric analysis of the cured product is less than 27% by mass.

[0058] (2) Prepreg

[0059] Figure 1 A prepreg 1 according to this embodiment is shown. The prepreg 1 is in sheet form. The prepreg 1 can be used as a material for the metal-clad laminate 4, as a material for the printed circuit board 5, and for preparing a multilayer printed circuit board 5 (by an additive method). For example, upon heating, the prepreg 1 cures and transforms into a cured product. The cured product of the prepreg 1 can form the insulating layer 40 of the metal-clad laminate 4 or the insulating layer 50 of the printed circuit board 5 (see [link]). Figure 4 as well as Figure 5 A and 5B).

[0060] The prepreg 1 includes a substrate 11 and a resin layer 10. The resin layer 10 contains a resin composition or a semi-cured product of a resin composition, each of which is impregnated into the substrate 11. A sheet of prepreg 1 includes at least one substrate 11. The thickness of the prepreg 1 may, but is not necessarily, equal to or greater than 10 μm and equal to or less than 120 μm.

[0061] Substrate 11 is a textile substrate in which warp yarns 111 and weft yarns 112 are woven perpendicularly to each other. Substrate 11 can be a textile, such as glass cloth. Alternatively, substrate 11 can also be a nonwoven fabric, such as glass nonwoven fabric.

[0062] The resin layer 10 may be a resin layer containing a resin composition (first case) or a resin layer containing a semi-cured product of a resin composition (second case).

[0063] In the first case, the resin layer 10 can be formed as follows. Specifically, the resin layer 10 can be formed by impregnating a varnish of the resin composition into the substrate 11 and then allowing the solvent to evaporate. This resin layer 10 is formed as an unreacted resin composition (its dried product). As used herein, "unreacted state" includes a completely unreacted state and a nearly unreacted state. Upon heating, the resin layer 10 changes from the unreacted state to a cured state.

[0064] On the other hand, in the second case, the resin composition is in a semi-cured state. As used herein, "semi-cured state" refers to the intermediate stage (stage B) of the curing reaction. The intermediate stage is between stage A, which is in a varnish state, and stage C, which is in a fully cured state. In the second case, the resin layer 10 can be formed as follows. Specifically, the resin layer 10 can be formed by impregnating the substrate 11 with a varnish of the resin composition, heating the substrate 11 to evaporate the solvent, and proceeding the curing reaction of the resin composition to the intermediate stage. This resin layer 10 is made from the resin composition in a semi-cured state (i.e., the semi-cured product of the resin composition).

[0065] As can be seen from the above description, the degree of curing reaction of resin layer 10 varies depending on the resin composition used.

[0066] It can be seen that the resin layer 10 of the prepreg 1 according to this embodiment is made of the above-described resin composition. Therefore, the resin layer 10 is used to form... Figure 8 The insulating layer 40 shown reduces the likelihood of leaving overhangs 6, which are typically associated with laser-cut holes.

[0067] (3) A film containing resin

[0068] Figure 2 A shows a resin-containing film 2 according to this embodiment. The resin-containing film 2 is sheet-like. The resin-containing film 2 includes a resin layer 20 and a support film 21. The resin layer 20 contains a resin composition or a semi-cured product of a resin composition. The support film 21 supports the resin layer 20 thereon. The resin-containing film 2 can be used to form a multilayer printed circuit board 5 (by an additive method).

[0069] For example, when heated, the resin layer 20 can become a cured product to form the insulating layer 40 of the metal-coated laminate 4 and the insulating layer 50 of the printed circuit board 5 (see...). Figure 4 as well as Figure 5 (A and 5B). Except that resin layer 20 is not impregnated into substrate 11, resin layer 20 is the same as resin layer 10 of prepreg 1. The thickness of resin layer 20 is not limited to any specific value, but may be, for example, equal to or greater than 10 μm and equal to or less than 120 μm.

[0070] A support film 21 supports the resin layer 20 thereon. Supporting the resin layer 20 in this manner makes it easier to handle. The support film 21 can be peeled off from the resin layer 20 as needed. Preferably, the support film 21 is peeled off from the insulating layer 40 after the resin layer 20 has cured to form the insulating layer 40. The same description applies to the case where the insulating layer 50 is formed from the resin layer 20.

[0071] For example, the support film 21 can be, but is not limited to, an electrically insulating film. Specific examples of the support film 21 include polyethylene terephthalate (PET) film, polyimide film, polyester film, polyethylene urea film, polyetheretherketone film, polyphenylene sulfide film, polyarylamide film, polycarbonate film, and polyacrylate film. However, these are merely examples, and the support film 21 need not be one of these films.

[0072] Despite Figure 2 In the example shown in A, a support film 21 covers one surface of the resin layer 20, but as Figure 2 As shown in Figure B, when one surface of the resin layer 20 is covered with the support film 21, the other surface of the resin layer 20 can be covered with the protective film 22. The protective film 22 and the support film 21 can also be peeled off from the resin layer 20 as needed. Covering both surfaces of the resin layer 20 in this manner makes it easier to process the resin layer 20. This also reduces the possibility of foreign particles adhering to the resin layer 20.

[0073] For example, the protective film 22 can be, but is not limited to, an electrically insulating film. Specific examples of the protective film 22 include polyethylene terephthalate (PET) films, polyolefin films, polyester films, and polymethylpentene films. However, these are merely examples, and the protective film 22 need not be one of these films.

[0074] It can be seen that the resin layer 20 of the resin-containing film 2 according to this embodiment is made of the above-described resin composition. Therefore, the resin layer 20 is used to form... Figure 8 The insulating layer 40 shown can reduce the likelihood of leaving overhangs 6, which are typically associated with laser hole cutting.

[0075] (4) Resin-coated metal foil sheets

[0076] Figure 3 A resin-containing metal foil sheet 3 according to this embodiment is shown. The resin-containing metal foil sheet 3 is in sheet form. The resin-containing metal foil sheet 3 includes a resin layer 30 and a metal foil sheet 31. The resin layer 30 contains a resin composition or a semi-cured product of a resin composition. The metal foil sheet 31 is bonded to the resin layer 30. For example, the resin-containing metal foil sheet 3 can be used to form a multilayer printed circuit board 5 (by additive method).

[0077] For example, when heated, the resin layer 30 can become a cured product to form the insulating layer 40 of the metal-coated laminate 4 and the insulating layer 50 of the printed circuit board (see [reference]). Figure 4 as well as Figure 5 (A and 5B). Except that resin layer 30 is not impregnated into substrate 11, resin layer 30 is the same as resin layer 10 of prepreg 1. The thickness of resin layer 30 is not limited to any specific value, but may be, for example, equal to or greater than 10 μm and equal to or less than 120 μm.

[0078] The metal foil sheet 31 can be, but is not limited to, copper foil sheet, aluminum foil sheet, or nickel foil sheet. For example, the metal foil sheet 31 can be patterned into conductor lines 51 by etching away unwanted portions using a subtractive process (see [link]). Figure 5 (A and 5B). The thickness of the metal foil sheet 31 is not limited to any specific value, but is preferably equal to or greater than 1 μm and equal to or less than 18 μm.

[0079] If the metal foil sheet 31 is constructed as an extremely thin metal foil sheet, then from the perspective of improving its processability, the metal foil sheet 31 preferably forms part of an extremely thin metal foil sheet having a carrier foil. The extremely thin metal foil sheet with a carrier foil includes the metal foil sheet 31 (extremely thin metal foil sheet), a peelable layer, and a carrier foil. In this case, for example, the thickness of the metal foil sheet 31 is equal to or less than 3 μm. The peelable layer is used to temporarily bond the metal foil sheet 31 to the carrier foil. The metal foil sheet 31 is peeled off from the peelable layer or the carrier foil as needed. The carrier foil is a support for supporting the metal foil sheet 31 thereon. Specific examples of carrier foils include copper foil sheets and aluminum foil sheets. The carrier foil is thicker than the metal foil sheet 31.

[0080] It can be seen that the resin layer 30 of the resin-containing metal foil sheet 3 according to this embodiment is made of the above-described resin composition. Therefore, the resin layer 30 is used to form... Figure 8 The insulating layer 40 shown can reduce the likelihood of leaving overhangs 6, which are typically associated with laser hole cutting.

[0081] (5) Metal-coated laminate

[0082] Figure 4 A metal-clad laminate 4 according to this embodiment is shown. The metal-clad laminate 4 includes an insulating layer 40 and at least one metal layer 41. For example, the metal-clad laminate 4 can be used as a material for a printed circuit board 5.

[0083] The insulating layer 40 comprises a cured product of the resin composition or a cured product of the prepreg 1. Although in Figure 4 In the example shown, a single insulating layer 40 comprises a single substrate 42, but a single insulating layer 40 may comprise two or more substrates 42. The thickness of the insulating layer 40 is not limited to any specific value, but may, for example, be equal to or greater than 10 μm and equal to or less than 120 μm.

[0084] One or more metal layers 41 are bonded to the insulating layer 40. Although in Figure 4 In the example shown, the metal layer 41 is bonded to both surfaces of the insulating layer 40, but the metal layer 41 may be bonded to only one surface of the insulating layer 40. A metal-clad laminate 4 having metal layers 41 bonded to both surfaces of the insulating layer 40 is a double-sided metal-clad laminate. A metal-clad laminate 4 having metal layers 41 bonded to only one surface of the insulating layer 40 is a single-sided metal-clad laminate.

[0085] For example, the metal layer 41 may be, but is not limited to, a metal foil sheet. For example, the metal foil sheet may be, but is not limited to, a copper foil sheet, an aluminum foil sheet, or a nickel foil sheet.

[0086] The thickness of the metal layer 41 is not limited to any specific value, but can be, for example, equal to or greater than 1 μm and equal to or less than 18 μm. If the metal layer 41 is an extremely thin metal foil sheet, then from the perspective of improving its processability, the metal layer 41 preferably forms part of an extremely thin metal foil sheet having a carrier foil. The extremely thin metal foil sheet having a carrier foil is as described above.

[0087] As can be seen, the insulating layer 40 of the metal-clad laminate 4 according to this embodiment comprises a cured product of the resin composition or a cured product of the prepreg 1. Therefore, the use of the insulating layer 40 can reduce the possibility of leaving overhangs 6, which are typically associated with laser-cut holes.

[0088] (6) Printed Circuit Board

[0089] Figure 5 A and 5B illustrate a printed circuit board 5 according to this embodiment. Each printed circuit board 5 includes an insulating layer 50 and conductor lines 51.

[0090] The insulating layer 50 comprises a cured product of the resin composition or a cured product of the prepreg 1. Figure 5 The printed circuit board 5 shown in Figure A includes a single insulating layer 50. Figure 5 In A, a single insulating layer 50 comprises a single substrate 52. However, this is merely an example and should not be construed as limiting. Alternatively, a single insulating layer 50 may comprise more than two substrates 52.

[0091] on the other hand, Figure 5 The printed circuit board 5 shown in Figure B includes multiple (specifically, three) insulating layers 50, namely a first insulating layer 510, a second insulating layer 520, and a third insulating layer 530. These three insulating layers 50 are stacked sequentially on top of each other in the thickness direction and are bonded together. Figure 5 In B, each of the first insulating layer 510, the second insulating layer 520, and the third insulating layer 530 may or may not include the substrate 52, or may include one or more substrates 52. It can be seen that the insulating layer 50 is the same as the insulating layer 40 of the metal-clad laminate 4 described above.

[0092] Conductor lines 51 are formed on insulating layer 50. Figure 5 In the printed circuit board 5 shown in A, conductor lines 51 are formed on each of the two surfaces of the insulating layer 50. Alternatively, conductor lines 51 may be formed on only one surface of the insulating layer 50.

[0093] On the other hand, Figure 5In the printed circuit board shown in B, the conductor line 51 includes an internal circuit 511 and an external circuit 512. The internal circuit 511 is located between two insulating layers 50. Specifically, the internal circuit 511 is located between the first insulating layer 510 and the second insulating layer 520, and between the second insulating layer 520 and the third insulating layer 530. The external circuit 512 is located outside the insulating layers 50. That is, the external circuit 512 is formed on the surface of the first insulating layer 510 and on the surface of the third insulating layer 530. Figure 5 The printed circuit board 5 shown in B also includes plated through-holes 8 and blind through-holes 9. The plated through-holes 8 and blind through-holes 9 electrically connect the internal circuit 511 and the external circuit 512 to each other. That is, the internal circuit 511 and the external circuit 512 are interconnected via the plated through-holes 8 and blind through-holes 9.

[0094] The conductor line 51 may be formed, but is not limited to, by means of, subtractive processing, semi-additive processing (SAP), or modified semi-additive processing (MSAP).

[0095] As can be seen, the insulating layer 50 of the printed circuit board 5 according to this embodiment comprises a cured product of the resin composition or a cured product of the prepreg 1. Therefore, the use of the insulating layer 50 can reduce the possibility of leaving overhangs 6, which are typically associated with laser-cut holes.

[0096] (7) Laser hole cutting method

[0097] Next, we will refer to Figure 8 Describe how to use the resin composition according to this embodiment for laser hole cutting.

[0098] For example, the laser beam L used can be, but is not limited to, a CO2 laser beam or a YAG laser beam. For example, the wavelength of the CO2 laser beam can be, but is not limited to, equal to or greater than 9 μm and equal to or less than 11 μm.

[0099] Examples of laser cutting methods include, but are not limited to, the direct method and the conformal mask method. In this embodiment, the direct method is preferably used. For example, the direct method is a method of directly creating a hole through the first metal layer 411 and the insulating layer 40 using a laser beam L without pre-providing an opening (i.e., a through-hole 43) through the first metal layer 411 by chemical etching. Compared with the conformal mask method, the direct method makes it easier to create holes with small diameters, improves the positional accuracy of the holes, and controls the shape of the holes. In addition, the direct method eliminates the need for the window etching process required for the conformal mask method, thereby simplifying the process and achieving a significant reduction in cost.

[0100] The insulating layer 40 contains a cured product of the resin composition according to this embodiment and has electrical insulation properties. That is, examples of the insulating layer 40 include the insulating layer 40 of the metal-clad laminate 4 described above and the insulating layer 50 of the printed circuit board 5. The thickness T of the insulating layer 40 is preferably equal to or greater than 10 μm and equal to or less than 120 μm.

[0101] For example, metal layer 41 may be, but is not limited to, a copper-containing layer. Examples of copper-containing layers include, but are not limited to, copper foil sheets. The first metal layer 411 is preferably thick enough to directly create the through-hole 43 using a laser beam L. The thickness of the first metal layer 411 may, for example, be equal to or greater than 1 μm and equal to or less than 18 μm. On the other hand, the thickness of the second metal layer 412 is not limited to any specific value.

[0102] Preferably, the first metal layer 411 undergoes a surface treatment. The surface treatment may be, but is not limited to, blackening treatment and roughening treatment using a sulfuric acid-hydrogen peroxide-based chemical solution. This allows the first metal layer 411 to have a higher absorption rate for the laser beam L.

[0103] Then, the first metal layer 411 is irradiated with a laser beam L along the thickness direction to create a through-hole 43 penetrating the first metal layer 411. In this state, the insulating layer 40 is continuously irradiated with the laser beam L to create a non-through-hole 44 penetrating the insulating layer 40. In this case, the pulse wavelength of the laser beam L is preferably equal to or greater than 10 μsec and equal to or less than 14 μsec. The energy of the laser beam L is preferably equal to or greater than 3 mJ and equal to or less than 6 mJ.

[0104] The insulating layer 40 contains a cured product of the resin composition according to this embodiment, thus reducing the likelihood of leaving overhangs 6 typically associated with laser-cut holes. For example, the inner diameter D1 of the through-hole 43 penetrating the first metal layer 411 can be equal to or greater than 50 μm and equal to or less than 60 μm. The inner diameter D2 of the opening of the non-through-hole 44 can be equal to or greater than 55 μm and equal to or less than 80 μm. The aspect ratio (T / D2) is equal to or greater than 0.5 and equal to or less than 1. The length W of the overhang 6 can be less than 11 μm. Therefore, the overhang 6 can have a shorter length W compared to known overhangs.

[0105] Shortening the length W of the overhang 6 in this way allows the chemical solution to reach even the depths of the non-through-hole 44 during subsequent decontamination processes, thereby making it easier to remove contaminants from inside the non-through-hole 44. This enables a sufficiently uniform electrodeposition of the plating layer on the inner surface of the non-through-hole 44, thereby improving the connection reliability of the through-hole. Furthermore, shortening the overhang 6 eliminates the need for a separate process step to remove it, which can also lead to a significant increase in productivity.

[0106] Example

[0107] Specific embodiments of this disclosure will now be described. Note that the embodiments described below are merely examples of this disclosure and should not be construed as limiting.

[0108] (1) Resin composition

[0109] The following are materials used in resin compositions:

[0110] <Curing Resin>

[0111] <<Main Reagent>>

[0112] [Epoxy Compounds]

[0113] • Phenolic varnish epoxy compound, product name "EPPN-201", manufactured by Nippon Kayaku Co., Ltd., with an epoxy equivalent of 180 to 200 g / eq;

[0114] • Naphthol-aralkyl epoxy compound, product name "HP-9500", manufactured by DIC Corporation, with an epoxy equivalent of 200 to 240 g / eq; and

[0115] • Biphenyl-aryl epoxide compound, product name "NC-3000-H", produced by Nippon Kayaku Co., Ltd., with an epoxy equivalent of 280 to 300 g / eq.

[0116] [Maleimide compounds]

[0117] • Phenolic varnish maleimide compound, product name "BMI-2300", produced by Daiwa Fine Chemicals Co., Ltd., phenylmethane maleimide.

[0118] <<Curing Agent>>

[0119] [Amide compounds]

[0120] • Dicyandiamide (DICY), produced by Nippon Carbide Industries Co., Inc.

[0121] [Phenolic compounds]

[0122] • Phenolic varnish containing phenolic compounds, product name "TD-2090-60M", manufactured by DIC Corporation, with a hydroxyl equivalent of 105 g / eq; and

[0123] • Biphenyl-arylalkylphenol compound, product name "GPH-103", produced by Nippon Kayaku Co., Ltd., with a hydroxyl equivalent of 220 to 240 g / eq.

[0124] [Cyanate ester compounds]

[0125] • Phenolic varnish cyanate compound, product name "PT-30", manufactured by Lonza.

[0126] <Other>

[0127] <<Elastomers>>

[0128] • Acrylic rubber (acrylate polymer), product name "SG-P3", produced by Nagase ChemteX Corporation, with a weight average molecular weight of 850,000.

[0129] <<Catalyst>>

[0130] ·2-Ethyl-4-methylimidazole, product name "2E4MZ", manufactured by Shikoku Chemicals Corporation; and

[0131] • Zinc octoate, product name "Zn-OCTOATE 20% T", is manufactured by DIC Corporation. The metal species is Zn, and the metal content is 20%.

[0132] <<Filling>>

[0133] ● Spherical silica, product name "SC2050-MB", produced by Admatechs, with an average particle size of 0.5μm.

[0134] The curable resin and other components are blended together to obtain any of the compositions shown in Table 1 below, and then mixed with a suitable solvent. The mixture is stirred until homogeneous. In this manner, a varnish of the resin composition is prepared.

[0135] (2) Metal foil sheets with resin

[0136] The varnish prepared therefrom is applied to an ultrathin metal foil sheet with a carrier foil (an ultrathin copper foil sheet with a carrier foil, product name "MT18FL", manufactured by Mitsui Mining & Smelting Co., Ltd., with a thickness of 1.5 μm for the ultrathin copper foil sheet and a thickness of 18 μm for the carrier foil), and then heated and dried at a temperature of 90°C to 140°C for about 4 minutes, thereby preparing a resin-containing metal foil sheet (a resin-containing copper foil sheet), wherein the thickness of the resin layer is about 50 μm.

[0137] (3) Metal-coated laminate

[0138] (3.1) Substrate for first evaluation

[0139] Two resin-coated metal foil sheets are stacked together with their resin layers facing each other. The laminate is then vacuum-formed under conditions including a temperature of 220°C, a pressure of 2 MPa, and a duration of two hours. In this manner, a double-sided metal-clad laminate (double-sided copper-clad laminate) with an insulating layer of approximately 0.1 mm thickness is manufactured. The substrate thus manufactured is used as the first evaluation substrate.

[0140] (3.2) Substrate for Second Evaluation

[0141] A resin-coated metal foil sheet is laminated onto each side of a double-sided metal-clad laminate (double-sided copper-clad laminate) having an insulating layer with a thickness of 0.2 mm. Then, the assembly is vacuum-formed under the same conditions as the first evaluation substrate described above. In this manner, a four-layer board is manufactured and used as the second evaluation substrate.

[0142] (4) Physical properties

[0143] Thermogravimetric analysis was performed on the insulating layer of the first evaluation substrate under a heating rate of 90°C / min, from 30°C to 800°C. The amount of exhaust gas emitted from the insulating layer was measured in the temperature range of 30°C to 550°C and in the temperature range of 30°C to 600°C. The results are summarized in Table 1 below.

[0144] (5) Experiment

[0145] (5.1)Overhanging part

[0146] A laser cutting machine (model "ML605GTW4-P", manufactured by Mitsubishi Electric Corporation) for creating holes through a substrate was used to laser cut holes in the second evaluation substrate using a CO2 laser beam via a direct method. In this manner, holes were created in the surface copper foil sheet with an inner diameter (corresponding to...) Figure 8 D1 shown is a 50μm through hole and its depth (corresponding to) Figure 8 The hole shown (T) is a 50 μm non-through hole. Laser drilling is performed under the following conditions:

[0147] Mask:

[0148] Pulse width: 12μsec; and

[0149] Energy: 4.0–5.0 mJ.

[0150] For this non-through hole, the length of the overhang was measured. The results are summarized in Table 1 below. Additionally, a graph showing the correlation between the amount of venting and the length of the overhang was plotted. Figure 6 This is a graph showing the correlation between the amount of exhaust gas discharged and the length of the remaining overhang in the temperature range of 30°C to 550°C. Figure 7 This is a graph showing the correlation between the amount of exhaust gas discharged and the length of the remaining overhang in a temperature range of 30°C to 600°C. Figure 6 and 7 In this disclosure, the results of specific embodiments are represented by hollow circles, and the results of comparative examples are represented by solid circles. A straight line fitting these data is drawn using the least squares method.

[0151] (5.2) Flame resistance

[0152] Test pieces, each 125 mm long and 12.5 mm wide, were cut from the first evaluation substrate. Ten flammability tests (vertical burning tests) were performed on the test pieces according to Underwriters Laboratories' "Test for Flammability of Plastic Materials – UL 94". Specifically, each of the five test pieces underwent two flammability tests. The average duration of continuous burning of the test pieces during the flammability tests was obtained. The test pieces were rated according to their flammability as follows:

[0153] “V-0”: The average duration is equal to or less than 5 seconds;

[0154] “V-1”: Average duration greater than 5 seconds; and

[0155] “V-2”: The test piece continued to burn to the end.

[0156]

Claims

1. A resin composition containing a curable resin, When the cured product of the resin composition is subjected to thermogravimetric analysis at a heating rate of 90°C / min from 30°C to 800°C, the amount of exhaust gas discharged from the cured product at temperatures ranging from 30°C to 550°C is less than 27% by mass relative to the total mass of the cured product. The curable resin consists of a main reagent and a curing agent. The main reagent is composed of a biphenyl-aryl alkyl epoxy compound. The curing agent is composed of biphenyl-arylphenol compounds. The proportion of the main reagent is equal to or greater than 60 parts by mass and equal to or less than 95 parts by mass relative to a total of 100 parts by mass of the main reagent and the curing agent.

2. The resin composition according to claim 1, wherein... The amount of exhaust gas discharged from the cured product at temperatures ranging from 30°C to 600°C is less than 30% of the total mass of the cured product.

3. A prepreg, said prepreg comprising: Substrate; And a resin layer comprising the resin composition of claim 1 or 2 or a semi-cured product of the resin composition, wherein the resin composition or the semi-cured product is impregnated into the substrate.

4. A resin-containing membrane, said resin-containing membrane comprising: A resin layer comprising the resin composition of claim 1 or 2 or a semi-cured product of the resin composition; And a support film supporting the resin layer thereon.

5. A resin-containing metal foil sheet, said resin-containing metal foil sheet comprising: A resin layer comprising the resin composition of claim 1 or 2 or a semi-cured product of the resin composition; And a metal foil sheet bonded to the resin layer.

6. A metal-clad laminate, the metal-clad laminate comprising: An insulating layer comprising a cured product of the resin composition of claim 1 or 2 or a cured product of the prepreg of claim 3; And a metal layer bonded to the insulating layer.

7. A printed circuit board, the printed circuit board comprising: An insulating layer comprising a cured product of the resin composition of claim 1 or 2 or a cured product of the prepreg of claim 3; And conductor lines formed on the insulating layer.

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