TW202014076A - Multilayer wiring board manufacturing method - Google Patents

Abstract

Provided is a multilayer wiring board manufacturing method with which, even when a circuit is made extremely thin, it is possible to obtain excellent circuit adhesion and to extremely effectively prevent penetration of the circuit during laser processing. The multilayer wiring board manufacturing method comprises: a step of preparing a stack provided with a metal foil, an insulating layer disposed on the metal foil, and a first wiring layer disposed on a surface of the insulating layer on the side opposite to the metal foil; a step of forming a via hole by subjecting the stack to laser processing from a surface of the metal foil; and a step of forming a multilayer wiring board by subjecting the side of the stack on which the via hole has been formed to plating and patterning. At least a surface of the first wiring layer opposing the metal foil has a reflectance of not less than 80% with respect to laser with a wavelength of 10.6 [mu]m, and has a density of peaks Spd of 7000/mm2 to 15000/mm2 inclusive. The ratio of thickness T2 of the metal foil to thickness T1 of the first wiring layer, or T2/T1, is not less than 0.23.

Description

Manufacturing method of multilayer wiring board

The present invention relates to a method of manufacturing a multilayer wiring board.

In recent years, in order to increase the mounting density and size reduction of printed wiring boards, multilayering of printed wiring boards has been widely carried out. Such a multilayer printed wiring board is used in various portable electronic devices for the purpose of weight reduction and miniaturization. Next, this multilayer printed wiring board requires a further reduction in the thickness of the interlayer insulating layer, and thinner and lighter weight as a wiring board.

As a technique for satisfying such requirements, a method of manufacturing a multilayer printed wiring board using a coreless build-up method is adopted. The coreless build-up method is a method in which an insulating layer and a wiring layer are alternately laminated (laminated) without using a so-called core substrate, and the method is multilayered. In the coreless build-up method, in order to facilitate the peeling of the support from the multilayer printed wiring board, it is proposed to use a metal foil with a carrier. For example, Patent Document 1 (Patent No. 4460013) discloses that an insulating layer and a metal layer with a thickness of 18 μm are sequentially stacked on the metal foil side of a metal foil with a carrier, and the metal layer is processed to form an inner layer circuit (first conductor pattern) , Insulating layer and metal foil are sequentially laminated in the inner layer circuit, the carrier is peeled off to form a substrate with metal foil on both sides of the inner layer circuit, and then the metal foil on both sides of the substrate and the inner layer circuit are passed through the holes A method of manufacturing a connected wiring board. In addition, Patent Document 1 also discloses that laser processing is performed from both sides of the substrate to form each through hole that penetrates the metal foil and the insulating layer to the inner layer circuit, and after patterning the metal foil on both sides of the substrate with a dry film, by plating The through-hole plated metal is filled, and outer-layer circuits (conductor patterns) are formed on both sides of the substrate. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Patent No. 4460013 [Patent Document 2] Patent No. 3142270

In recent years, the thickness of metal foils used for circuits of multilayer wiring boards has also decreased as the thickness of multilayer printed wiring boards has become thinner. In this regard, it is also desirable to use extremely thin metal foils in the manufacture of the wiring substrates described in Patent Document 1. However, when an existing ultra-thin copper foil (for example, 6 μm or more and 12 μm or less) is used as a circuit (for example, an inner layer circuit), there are not only two sides (outer layer) due to laser processing in the process of forming a through hole for interlayer connection The metal foil and insulating layer also penetrated into the circuit and caused holes. For example, Patent Document 2 (Patent No. 3142270) discloses that when the thickness of the inner-layer circuit is less than 4.5 times the thickness of the outer-layer copper foil with respect to the inner-layer circuit board (in other words, the thickness T _{2 of the} outer-layer copper foil relative to the inner layer When the thickness T ₁ of the circuit is T ₂ /T ₁ less than 1/4.5 (=0.22), there is a risk of damage to the inner layer circuit when drilling holes due to laser irradiation.

The present inventors have obtained a multilayer wiring board by using a wiring layer having a specific surface satisfying predetermined conditions as a reflectance of a laser with a wavelength of 10.6 μm and a peak vertex density Spd as a circuit (for example, an inner layer circuit). Even when the circuit is extremely thin, the circuit has good adhesion and can effectively prevent the penetration of the circuit caused by laser processing.

Therefore, an object of the present invention is to provide a method for manufacturing a multilayer wiring board, which has excellent circuit adhesion even when the circuit is extremely thinned, and can effectively prevent penetration of the circuit due to laser processing.

According to one aspect of the present invention, there is provided a method for manufacturing a multilayer wiring board, comprising: (a) preparing a metal foil, an insulating layer provided on the metal foil, and an opposite side of the metal foil provided on the insulating layer The construction of the laminate of the first wiring layer on the surface of the surface; (b) laser processing is performed on the laminate from the surface of the metal foil to form a layer that penetrates the metal foil and the insulating layer to reach the first wiring layer Through-hole engineering; (c) Applying coating and patterning to the side of the laminate where the through-hole is formed to form a multilayer wiring including the first wiring layer and the second wiring layer from the metal foil The construction of the board; wherein, at least the surface of the first wiring layer opposite to the metal foil has a reflectivity of 80% or more of the laser with a wavelength of 10.6 μm measured by a Fourier transform infrared spectrophotometer (FT-IR) and the vertex of the peak density Spd subject data measured ISO25178 of 7000 / mm ^{2 or} more than 15,000 / mm ² or less; the thickness T ₂ of the metal foil relative to the thickness of the first wiring layer T ₁ of the ratio T ₂ /T ₁ is 0.23 or more.

definition The definitions of the parameters used to specify the present invention are shown below.

In this manual, "reflectance of laser with a wavelength of 10.6 μm" refers to the measurement of the surface of a sample (metal foil) with a wavelength of 10.6 μm when irradiated by a Fourier transform infrared photometer (FT-IR). The ratio of the amount of light reflected by the reference plate (for example, Au vapor deposition mirror) to the amount of light reflected by the sample. The measurement of the reflectance of the laser with a wavelength of 10.6 μm can be performed using a commercially available Fourier conversion infrared photometer under the conditions described in the examples of this specification. In addition, since the wavelength of carbon dioxide laser typically used in laser processing is 10.6 μm, the laser wavelength of the Fourier conversion infrared photometer is set to 10.6 μm.

In this specification, "peak apex density Spd" refers to a parameter indicating the number of peak apexes per unit area measured based on ISO25178. The larger the value, the greater the number of contact points with other objects. The peak apex density Spd can be calculated by measuring the surface profile of a predetermined measurement area (for example, a region of 107 μm×143 μm) on the surface of the metal foil or the wiring layer with a commercially available laser microscope.

Manufacturing method of multilayer wiring board The present invention relates to a method of manufacturing a multilayer wiring board. The method of the present invention includes: (1) preparation of a laminate, (2) formation of through holes, and (3) formation of a second wiring layer.

Hereinafter, each of the processes (1) to (3) will be described with reference to FIG. 1.

(1) Preparation of laminate A laminate 16 including the metal foil 10, the insulating layer 12 provided on the metal foil 10, and the first wiring layer 14 provided on the surface of the insulating layer 12 opposite to the metal foil 10 is prepared. The laminate 16 is typically a method of manufacturing a multilayer wiring board such as the coreless build-up method described above, and corresponds to an intermediate product before peeling the support. For example, as shown in FIG. 1(i), the laminate 16 may be in a form in which an insulating layer 12' is further laminated on the surface of the first wiring layer 14 side (that is, the side opposite to the metal foil 10). At this time, the first wiring layer 14 becomes buried between the insulating layer 12 and the insulating layer 12' and becomes an inner layer circuit. Alternatively, the layered body 16 is in a form where a metal foil or a wiring layer (not shown) is formed on the surface on the side of the first wiring layer 14 via the insulating layer 12' (for example, a form having metal foil on both sides) Can also. In addition, the first wiring layer 14 may be provided in the insulating layer 12. In any case, the laminate 16 only needs to include at least the metal foil 10, the insulating layer 12, and the first wiring layer 14, and other layer configurations are not particularly limited.

The metal foil 10 may be a well-known configuration adopted for a metal foil for wiring layers. For example, the metal foil 10 may be formed by a wet film forming method such as electroless plating and electroplating, a dry film forming method such as sputtering and chemical vapor deposition, or a combination of these methods. Examples of the metal foil 10 may be aluminum, copper foil, stainless steel (SUS) foil, nickel foil, etc., preferably copper foil. The copper foil can be either rolled copper foil or electrolytic copper foil.

The metal foil 10 may be provided in the form of a metal foil with a carrier. The metal foil with carrier typically includes a carrier (not shown), a peeling layer (not shown), and a metal foil 10 in this order. The carrier is a foil or a layer for supporting the metal foil 10 and improving its handling. Preferred examples of the carrier include aluminum, copper foil, stainless steel (SUS) foil, resin film, resin film coated with copper on the surface, resin plate, glass plate, and combinations thereof. The thickness of the carrier is typically 5 μm or more and 250 μm or less, preferably 9 μm or more and 200 μm or less. In addition, the material of the peeling layer is not particularly limited as long as the peeling of the carrier is possible. For example, the peeling layer may be composed of a known material used as a peeling layer of a metal foil with a carrier. The peeling layer may be either an organic peeling layer or an inorganic peeling layer, or may be a composite peeling layer of an organic peeling layer and an inorganic peeling layer. The thickness of the peeling layer is typically 1 nm or more and 1 μm or less, preferably 5 nm or more and 500 nm or less, and more preferably 6 nm or more and 100 nm or less. When the metal foil 10 is provided in the form of a metal foil with a carrier, it is preferable to peel the carrier from the laminate 16 before laser processing of the metal foil 10 described later. This allows laser processing to be performed from the metal foil 10 in the through-hole formation process described later.

The laminated body 16 may be attached to a support (not shown) such as a prepreg on one side, and rigidity may be added. The prepreg is a general term for composite materials in which synthetic resin plates, glass plates, glass woven fabrics, glass non-woven fabrics, paper and other substrates are impregnated with synthetic resin. At this time, the metal foil with a carrier is attached on both sides of the support in a symmetrical manner, and the laminate 16 is formed on both sides of the obtained temporary laminate with a support in a vertically symmetrical manner. The carrier is preferably removed together. For example, a metal foil with a carrier provided with a metal foil 10 is attached to a support, and the insulating layer 12 and the first wiring layer 14 are sequentially laminated on the metal foil 10 to form a laminate 16. Alternatively, a metal foil with a carrier including a metal foil different from the metal foil 10 is attached to the support, and the first wiring layer 14, the insulating layer 12, and the metal foil 10 are sequentially laminated on the metal foil to be laminated体16。 16. In this way, the laminate 16 prepared in the present invention may be produced by laminating or even forming any one of the metal foil 10 and the first wiring layer 14.

The insulating layer 12 may be a known configuration of an insulating layer used in a coreless build-up method, and is not particularly limited. For example, the insulating layer 12 is more preferably formed by laminating insulating resin materials such as a prepreg and a resin sheet on the metal foil 10 and then applying hot stamping. Preferred examples of the insulating resin impregnated with the prepreg used are epoxy resin, cyanate resin, bismaleimide triazine resin (BT resin), polyphenylene ether resin, phenol resin, etc. . In addition, as preferred examples of the insulating resin constituting the resin sheet, epoxy resin, polyimide resin, polyester fiber resin, etc. may be used. Furthermore, from the viewpoint of improving the insulating properties of the insulating layer 12 and the like, it may contain filler particles made of various inorganic particles such as silicon dioxide and aluminum oxide. Although the thickness of the insulating layer 12 is not particularly limited, it is preferably 1 μm or more and 100 μm or less, more preferably 5 μm or more and 40 μm or less, and still more preferably 10 μm or more and 30 μm or less. The insulating layer 12 may be composed of a plurality of layers. In addition, as shown in FIG. 1(i), when the laminated body 16 includes the insulating layer 12', the insulating layer 12' may be configured as a quasi-insulating layer 12, and the preferred form of the insulating layer 12 described above is also applied to the insulating layer 12 '.

The first wiring layer 14 can be preferably formed, for example, by laminating a metal foil for the first wiring layer on the insulating layer 12 or the insulating layer 12', and patterning the metal foil for the first wiring layer. Alternatively, the first wiring layer 14 may be preferably formed by patterning on a metal foil different from the metal foil 10 by metal plating or the like. The metal foil for the first wiring layer may be formed by a wet film forming method such as electroless plating and electroplating, a dry film forming method such as sputtering or chemical vapor deposition, or a combination of these methods. Examples of the metal foil for the first wiring layer may be aluminum foil, copper foil, stainless steel (SUS) foil, etc., preferably copper foil. The copper foil can be either rolled copper foil or electrolytic copper foil. The preferred thickness of the metal foil for the first wiring layer is 0.1 μm or more and 12 μm or less, more preferably 1 μm or more and 9 μm or less, and still more preferably 5 μm or more and 7 μm or less. Within this range, it is extremely suitable for fine circuit formation. The patterning used to form the first wiring layer 14 is performed by a well-known technique such as the subtractive process method, MSAP (modified-semi-additive process) method, and SAP (semi-additive) method. Yes, it is not particularly limited. When the insulating layer 12 or the insulating layer 12' is laminated on the first wiring layer 14, an inner layer process may be performed on the first wiring layer 14 in advance. The inner layer treatment includes roughening treatment such as CZ treatment, etc. CZ treatment uses an organic acid-based micro-etching agent (for example, manufactured by MEC Corporation, product number CZ-8101), and fine roughening can be applied to the surface of the first wiring layer 14 Carry out well. Thereby, fine irregularities are formed on the surface of the first wiring layer 14, and the adhesion with the insulating layer stacked thereafter can be improved.

At least the surface of the first wiring layer 14 facing the metal foil 10 has a reflectivity of 80% or more of the laser beam of 10.6 μm measured by a Fourier transform infrared spectrophotometer (FT-IR), and is subject to ISO 25178 The peak density Spd of the measured peaks is 7,000/mm ² or more and 15,000/mm ² or less. By using a wiring layer that satisfies such conditions as a circuit (for example, an inner layer circuit) to manufacture a multilayer wiring board, the circuit has good adhesion and can effectively prevent the penetration of the circuit due to laser processing.

That is, by setting the reflectance of the laser beam of the wavelength 10.6 μm measured by the Fourier transform infrared spectrophotometer on the surface of the first wiring layer 14 facing the metal foil 10 to 80% or more, it can effectively prevent Used for absorption of laser light formed by through holes. As a result, even when the first wiring layer 14, the ultra-thin (also even if the thickness T ₂ of the metal foil 10 with respect to the thickness T of the first wiring layer 14 is _a ratio T ₂ / T ₁ is greater than 0.23 or more), and The penetration of the first wiring layer 14 by laser processing can be extremely effectively prevented. The laser reflectance at this wavelength of 10.6 μm increases as the surface of the first wiring layer 14 becomes smoother. However, if the surface of the first wiring layer 14 is simply smoothed in order to increase the laser reflectivity, the adhesion between the first wiring layer 14 and the insulating layer 12 will decrease, and circuit peeling is likely to occur. Therefore, it is not easy to take into account the prevention of the penetration of the circuit due to laser processing and the adhesion to the circuit. In this regard, in the present invention, on the surface of the first wiring layer 14 facing the metal foil 10, the peak apex density is maintained while maintaining the smoothness that contributes to the improvement of the laser reflectance at a wavelength of 10.6 μm Spd is set to 7000 pieces/mm ² or more and 15000 pieces/mm ² or less, and the number of contacts can be ensured for the first wiring layer 14 to sink into the insulating layer 12. As a result, while ensuring high circuit adhesion, it is possible to effectively prevent penetration of the inner layer circuit due to laser processing.

From the above viewpoint, the surface of the first wiring layer 14 opposed to the metal foil 10 has a reflectivity of 80% or more of the laser beam of 10.6 μm wavelength measured by a Fourier transform infrared spectrophotometer (FT-IR). It is preferably 85% or more, more preferably 90% or more, and still more preferably 95% or more. The upper limit value is not particularly limited, and although it may be 100%, it is typically 98% or less. In addition, the peak density Spd of the peak of the surface of the first wiring layer 14 opposed to the metal foil 10 measured in accordance with ISO 25178 is 7,000 pieces/mm ² or more and 15,000 pieces/mm ² or less, preferably 10,000 pieces/mm ² or more and 15,000/mm ² or less, more preferably 13,000/mm ² or more and 15,000/mm ² or less. Within the above-mentioned preferable range, while ensuring high circuit adhesion, the penetration of the laser-processed first wiring layer 14 can be extremely effectively prevented.

On the surface of the first wiring layer 14 opposed to the metal foil 10, the laser reflectance and the peak apex density Spd of the wavelength 10.6 μm in the above range allow the metal foil for the first wiring layer forming the first wiring layer 14 The surface may be provided in advance, or may be provided on the surface of the first wiring layer 14 afterwards by the above-mentioned inner layer treatment (for example, roughening treatment such as CZ treatment). Therefore, the surface of the first wiring layer 14 facing the metal foil 10 is preferably a roughened surface. In addition, the metal foil for the first wiring layer having a surface that satisfies the above conditions can be realized by subjecting the surface of the metal foil to roughening treatment under known or even desired conditions. In addition, a commercially available metal foil having a surface that satisfies the above conditions may be selectively obtained.

Similar to the surface of the first wiring layer 14 opposite to the metal foil 10, the surface of the first wiring layer 14 opposite to the metal foil 10 has a laser reflectance and peak apex density of a wavelength of 10.6 μm in the above range Spd will do too. With this, while ensuring high adhesion to the layer (for example, the insulating layer 12 ′) laminated on the side opposite to the metal foil 10 of the first wiring layer 14, from the side opposite to the metal foil 10 of the laminate 16 It is also possible to prevent the penetration of the first wiring layer 14 when laser processing is applied to the surface of.

The thickness T ₂ of the metal foil 10 with respect to the thickness of the first wiring layer 14 is T, _a ratio T ₂ / T ₁ is 0.23 or more, preferably 0.25 or more, more preferably 0.30 or more. As described above, according to the present invention, since the first wiring layer 14 has a surface that is difficult to absorb laser light, even if the first wiring layer 14 is extremely thinned to satisfy the above range, the laser light of the first wiring layer 14 can be suppressed Processing damage. T ₂ /T _{1 is} preferably 1.0 or less, more preferably 0.50 or less, and still more preferably 0.33 or less. In addition, when surface treatment is performed on the first wiring layer 14 and/or the metal foil 10 before laser processing is applied (even if the thickness of the first wiring layer 14 and/or the metal foil 10 changes), the above T ₁ and T ₂ are respectively Refers to the thickness of the first wiring layer 14 and the thickness of the metal foil 10 after the surface treatment. For example, when the first wiring layer 14 is subjected to the inner layer treatment, T ₁ becomes the thickness of the first wiring layer 14 after the inner layer treatment.

The thickness T _{1 of the} first wiring layer 14 is preferably 2 μm or more and 15 μm or less, more preferably 3 μm or more and 12 μm or less, still more preferably 5 μm or more and 10 μm or less, and particularly preferably 5 μm or more and 8 μm or less. Within this range, the reduction in thickness required for multilayer printed wiring boards is extremely advantageous. On the other hand, the thickness T _{2 of the} metal foil 10 is preferably 0.5 μm or more and 6 μm or less, more preferably 0.7 μm or more and 4.0 μm or less, still more preferably 1.2 μm or more and 3.0 μm or less, and particularly preferably 1.5 μm or more and 2.0 μm or less. . Within this range, it is easy to form the through-hole 18 by direct laser processing from the metal foil 10 in the through-hole forming process described later. In addition, when the metal foil 10 is used for forming a wiring layer, if it is within the above-mentioned thickness range, the formability to a fine circuit is also good.

(2) Formation of through holes As shown in FIG. 1(ii), laser processing is performed on the laminate 16 from the surface of the metal foil 10 to form the through metal foil 10 and the insulating layer 12 to reach the first wiring layer 14的通孔18。 The through hole 18. Although various types of lasers such as carbon dioxide laser, excimer laser, UV laser, and YAG laser can be used for laser processing, carbon dioxide laser is particularly preferred. According to the method of the present invention, since the first wiring layer 14 has a surface that is difficult to absorb laser light, penetration of the first wiring layer 14 due to laser processing can be extremely effectively prevented in the process of forming the through hole. In particular, even when the laser output density is increased in order to efficiently perform laser processing, it is difficult for the first wiring layer 14 to penetrate according to the present invention. From this viewpoint, the laser output density is preferably in the laser processing 8MW / cm ² or more 14MW / cm ² or less, more preferably 8MW / cm ² or more 12MW / cm ² or less, and then the best of 9MW / cm ² Above 12MW/cm ² below. Therefore, the through holes 18 in the present invention are preferably formed by laser irradiation of one shot by using the output density laser within the above range.

The diameter of the through hole 18 is preferably 30 μm or more and 80 μm or less, more preferably 30 μm or more and 60 μm or less, and still more preferably 30 μm or more and 40 μm or less. Within this range, it is extremely advantageous for increasing the density of multilayer printed wiring boards. In addition, in order to form the through-hole 18 having the small diameter as described above, it is preferable to reduce the laser beam diameter (spot diameter). At this time, since the energy of the laser is easily concentrated on the laser-irradiated portion of the first wiring layer 14, the penetration of the first wiring layer 14 is easily generated originally. Regarding this point, according to the method of the present invention, because the first wiring layer 14 has a surface that is difficult to absorb laser light, even if the laser energy is concentrated, the penetration of the first wiring layer 14 can be effectively prevented.

The process of forming a through hole, as a treatment for removing the resin residue (rubber residue) at the bottom of the through hole generated when the through hole is formed by laser processing, further includes the use of at least one of a chromate solution and a permanganate solution The glue removal project is better. The coplanarity engineering is a treatment in which swelling treatment, chromic acid treatment, permanganic acid treatment, and reduction treatment are sequentially performed, and a well-known wet process can be used. An example of chromate may be potassium chromate. Examples of permanganate include sodium permanganate and potassium permanganate. In particular, it is preferable to use permanganate from the viewpoints of reduction of the discharge of environmental load substances from the scum removal treatment liquid, electrolytic regeneration, and the like.

(3) Formation of the second wiring layer As shown in FIG. 1(iii), the side of the laminated body 16 on which the via 18 is formed is plated and patterned to form a layer including the first wiring layer 14 and the second wiring layer 22 from the metal foil 10 Multilayer wiring board 24. As a result, the through-hole 18 is filled with plated metal, and the first wiring layer 14 and the second wiring layer 22 are electrically connected through the through-hole 18. The second wiring layer 22 typically contains a metal derived from the metal foil 10, but it may be formed as a new wiring layer (the metal derived from the metal foil 10 is not included) following only the surface contour of the metal foil 10. The method of forming the second wiring layer 22 is not particularly limited, and known methods such as a subtractive process method, MSAP method, and SAP method can be used. Here, FIG. 1(iii) is a circuit formation by MSAP method. As an example of circuit formation by the MSAP method, first, a photoresist (not shown) is formed on the surface of the metal foil 10 in a predetermined pattern. The photoresist is preferably a photosensitive film. In this case, a predetermined wiring pattern may be provided to the photoresist by exposure and development. Next, a plating layer 20 is formed on the exposed surface of the metal foil 10 (that is, the portion not covered by the photoresist layer) and the through hole 18. At this time, since the through-hole 18 is filled with plated metal, the first wiring layer 14 and the metal foil 10 are electrically connected through the through-hole 18. The electroplating may be performed by a well-known method, and is not particularly limited. After peeling off the photoresist layer, by etching the metal foil 10 and the plating layer 20, the multilayer wiring board 24 in which the second wiring layer 22 is formed can be obtained.

A multilayer wiring layer may be formed on the multilayer wiring board 24 again. That is, by alternately laminating the wiring layers including the insulating layer and the wiring pattern on the multilayer wiring board 24 alternately, the multilayer wiring board up to the nth wiring layer (n is an integer of 3 or more) can be obtained. This process may be repeated until the desired number of build-up wiring layers is formed. In addition, if necessary, bumps for mounting solder resists, pillars, etc. may be formed on the outer surface. [Example]

Hereinafter, the present invention will be further described using examples.

Example 1～6 Six types of copper foils used as metal foils for forming inner layer circuits of a multilayer wiring board were prepared and various evaluations were conducted. The specific sequence is shown below.

(1) Preparation of copper foil Six types of electrolytic copper foils having a thickness of 9 μm having the parameters shown in Table 1 on at least one side were prepared. Some of these copper foils are commercially available products, and others are specially made by known methods. The measurement and calculation methods of the parameters of the prepared copper foil are as follows.

(Reflectance of laser with a wavelength of 10.6 μm in FT-IR) Using an infrared spectrophotometer (Nicolet Nexus 640 FT-IR Spectrometer manufactured by Thermo Fisher Scientific Co., Ltd.), the surface of the copper foil was measured under the following conditions to obtain an IR spectrum data. By analyzing the obtained IR spectrum data, the reflectance of the laser with a wavelength of 10.6 μm is calculated. <Measurement conditions>-Measurement method: regular reflection method-Background: Au vapor deposition mirror-Resolution: 4cm ^-1 -Number of scans: 64scan-Detector: DTGS (Deuterium Tri-Glycine Sulfate) detector

(Peak apex density Spd) Using a laser microscope (manufactured by Keynes Co., Ltd., VK-X100), the surface of the copper foil was measured under the conditions of the cut-off wavelength of 0.8 μm and the magnification of 2000 times (measurement area 107 μm × 143 μm) due to the S filter, based on ISO25178 The peak density Spd of the peak.

(2) Evaluation of copper foil With respect to the prepared copper foil, various characteristics were evaluated as follows.

<Laser workability> As shown in FIG. 2, the copper foil prepared in (1) above was used as a metal foil for inner layer circuit formation. The laminate for evaluation of laser workability was prepared as follows, and the laser processing was evaluated Sex. First, a copper foil with a thickness of 2 μm was prepared as the metal foil 110, and a prepreg (GHPL-830NSF, manufactured by Mitsubishi Gas Chemical Co., Ltd., GHPL-830NSF) with a thickness of 0.02 mm was laminated on the metal foil 110 as the insulating layer 112. Next, the copper foil prepared in the above (1) was used as the metal foil 113 for the first wiring layer, and the surface having each parameter side shown in Table 1 was laminated so as to contact the insulating layer 112 at a pressure of 4.0 MPa Then, hot stamping was performed at a temperature of 220°C for 90 minutes to obtain a first laminate 115 (Fig. 2(i)). After etching the surface of the first wiring layer metal foil 113 with a micro-etching solution at 1 μm, a dry film is attached, and exposure and development are performed in a predetermined pattern to form an etched photoresist. The surface of the metal foil 113 for the first wiring layer was treated with a copper chloride etchant to dissolve and remove copper from between the etched photoresists, and the etched photoresist was peeled off to form the first wiring layer 114 to obtain a second laminate 116 (Figure 2(ii)). The surface of the first wiring layer 114 is subjected to roughening treatment (CZ treatment). The thickness of the first wiring layer 114 after the roughening treatment is 7 μm. After that, a prepreg with a thickness of 0.02 mm (manufactured by Mitsubishi Gas Chemical Co., Ltd., GHPL-830NSF) and a copper foil with a thickness of 2 μm were used as the insulating layer 112′ and the second laminate 116 on which the first wiring layer 114 was formed. The metal foils 110' are sequentially stacked, and hot stamping is performed at a pressure of 4.0 MPa and a temperature of 220°C for 90 minutes. By this, the laminate 117 for evaluation of laser processability is obtained (FIG. 2(iii) ). The ratio T ₂ /T ₁ of the thickness T ₂ (2 μm) of the metal foil 110 to the thickness T ₁ (7 μm) of the first wiring layer 114 of the laminate 117 for laser processability evaluation is 2/7=about 0.29. The obtained laminate 117 for evaluation of laser processability was subjected to laser processing from the metal foil 110 side at an output density of 9.5 MW/cm ² using carbon dioxide laser to form the through metal foil 110 and the insulating layer 112 to reach the first The wiring layer 114 has a through hole 118 with a diameter of 65 μm (FIG. 2(iv) ). This through hole 118 was observed with a metal microscope from the metal foil 110 side, and the presence or absence of penetration of the first wiring layer 114 was determined. For each example, the formation and penetration determination of the through-hole 118 were performed for every 88 holes, and the penetration rate of the first wiring layer 114 after laser processing was calculated from the number of formation of the through-hole 118 and the number of penetrations of the first wiring layer 114.

<circuit adhesion> Three prepregs (GHPL-830NSF, manufactured by Mitsubishi Gas Chemical Co., Ltd.) with a thickness of 0.1 mm are laminated, and the laminated prepreg will be the copper foil prepared in (1) above to have each of those shown in Table 1. The surface on the parameter side was laminated so as to be subjected to hot stamping molding at a pressure of 4.0 MPa and a temperature of 220° C. for 90 minutes to prepare a copper-clad laminate sample. A dry film was bonded on both sides of the copper-clad laminate sample to form an etched photoresist layer. Next, on the etched photoresist layers on both surfaces, a 0.8 mm width peel strength measurement test circuit was exposed and developed to form an etched pattern. Thereafter, the circuit is etched with a copper etching solution, and the photoresist is stripped to obtain a circuit. The circuit thus formed (thickness 9 μm, circuit width 0.8 mm) was peeled off the surface of the prepreg in the direction of 90° according to JIS C 6481-1996, and the peel strength (kgf/cm) was measured.

Examples 7 to 10 Instead of using an electrolytic copper foil having a thickness of 9 μm, various characteristics were evaluated in the same manner as in Examples 1 to 6, except that an electrolytic copper foil having a thickness of 7 μm having the parameters shown in Table 1 on at least one side was used. In addition, the thickness of the first wiring layer 114 after the roughening treatment (CZ treatment) of the laminate 117 for laser processability evaluation was 5 μm, and T ₂ /T ₁ was 2/5=about 0.40.

result The evaluation results obtained in Examples 1 to 10 are shown in Table 1.

Example 11 In addition to 1) instead of copper foil with a thickness of 2 μm, copper foil with a thickness of 3 μm was used as the metal foils 110 and 110 ′, 2) the thickness of the first wiring layer 114 after roughening (CZ treatment) was adjusted by adjusting the etching amount Is 5 μm (that is, T ₂ /T _{1 is} set to 3/5=0.60), and 3) The output density of the carbon dioxide laser is changed from 9.5MW/cm ² to 9.75MW/cm ² , and the laser is performed in the same manner as in Example 5. Evaluation of shot processability.

Example 12 except that 1) the thickness of 2μm substituted copper foil, the metal foils 110, 110 '3μm thick copper foil were used, and 2) the density of the carbon dioxide laser output from 9.5MW / cm ² was changed to 9.75MW / cm ² Except for Example 10, the laser processability was evaluated. In addition, the thickness of the first wiring layer 114 after the roughening treatment (CZ treatment) of the laminate 117 for laser processability evaluation was 5 μm, and T ₂ /T ₁ was 3/5=0.60.

Example 13 except that 1) the thickness of 2μm substituted copper foil, the metal foils 110, 110 '3μm thick copper foil were used, and 2) the density of the carbon dioxide laser output is changed from 9.5MW / cm ² to 9.75MW / cm ² Except for Example 8, the laser processability was evaluated. In addition, the thickness of the first wiring layer 114 after the roughening treatment (CZ treatment) of the laminate 117 for laser processability evaluation was 5 μm, and T ₂ /T ₁ was 3/5=0.60.

Example 14 Except for 1) replacing copper foil with a thickness of 3 μm, using copper foil with a thickness of 5 μm as the metal foils 110 and 110 ′, and 2) changing the output density of the carbon dioxide laser from 9.75 MW/cm ² to 10.25 MW/cm ² Other than that, the laser processability was evaluated in the same manner as in Example 11. In addition, the thickness of the first wiring layer 114 after the roughening treatment (CZ treatment) of the laminate 117 for laser processability evaluation was 5 μm, and T ₂ /T ₁ was 5/5=1.0.

Example 15 Except for 1) replacing copper foil with a thickness of 3 μm, using copper foil with a thickness of 5 μm as the metal foils 110 and 110 ′, and 2) changing the output density of the carbon dioxide laser from 9.75 MW/cm ² to 10.25 MW/cm ² Other than that, the laser processability was evaluated in the same manner as in Example 12. In addition, the thickness of the first wiring layer 114 after the roughening treatment (CZ treatment) of the laminate 117 for laser processability evaluation was 5 μm, and T ₂ /T ₁ was 5/5=1.0.

Example 16 Except for 1) replacing copper foil with a thickness of 3 μm, using copper foil with a thickness of 5 μm as the metal foils 110 and 110 ′, and 2) changing the output density of the carbon dioxide laser from 9.75 MW/cm ² to 10.25 MW/cm ² Other than that, the laser processability was evaluated in the same manner as in Example 13. In addition, the thickness of the first wiring layer 114 after the roughening treatment (CZ treatment) of the laminate 117 for laser processability evaluation was 5 μm, and T ₂ /T ₁ was 5/5=1.0.

result The evaluation results obtained in Examples 11 to 16 are shown in Table 2.

10: Metal foil 12: Insulation 14: 1st wiring layer 16: Laminate 12’: Insulation 18: through hole 22: Second wiring layer 24: Multilayer wiring board 110: metal foil 112: Insulation 113: First metal foil 115: Layer 1 116: Layer 2 112’: Insulation 110’: Metal foil 118: through hole 114: 1st wiring layer 117: Laminate for evaluation of laser processability

[Fig. 1] An engineering flowchart showing an engineering (engineering (i) to (iii)) in an example of the manufacturing method of the present invention. [Fig. 2] A process flow chart showing a process (processes (i) to (iv)) for producing a laminate for laser processability evaluation in Examples 1 to 6 and forming a through hole.

10: Metal foil

12: Insulation

12’: Insulation

14: 1st wiring layer

16: Laminate

18: through hole

20: plating layer

22: Second wiring layer

24: Multilayer wiring board

Claims (7)

A method of manufacturing a multilayer wiring board, comprising: (a) preparing a layer including a metal foil, an insulating layer provided on the metal foil, and a first wiring layer provided on a surface of the insulating layer opposite to the metal foil The process of the product; (b) The process of applying laser processing to the layered product from the surface of the metal foil to form a through hole that penetrates the metal foil and the insulating layer to the first wiring layer; (c) The step of forming a multilayer wiring board including the first wiring layer and the second wiring layer from the metal foil by applying plating and patterning on the side of the laminated body where the through hole is formed; wherein, the first At least the surface of the wiring layer facing the aforementioned metal foil has a reflectivity of 80% or more measured by a Fourier Transform Infrared Spectrophotometer (FT-IR) at a wavelength of 10.6 μm, and is measured in accordance with ISO 25178 Spd peak apex density of 7000 / mm ^{2 or} more than 15,000 / mm ² or less; the thickness T ₂ of the metal foil relative to the thickness T of the first wiring layer is ₁ ratio of T ₂ / T ₁ is 0.23 or more. The method according to claim 1, wherein the thickness T ₁ of the first wiring layer is 2 μm or more and 15 μm or less. The method according to claim 1 or 2, wherein the thickness T ₂ of the metal foil is 0.5 μm or more and 6 μm or less. The method according to claim 1 or 2, wherein T ₂ /T ₁ is 1.0 or less. The method according to claim 1 or 2, wherein the laser output density in the laser processing is 8 MW/cm ² or more and 14 MW/cm ² or less. The method according to claim 1 or 2, wherein the diameter of the through hole is 30 μm or more and 80 μm or less. The method according to claim 1 or 2, wherein the metal foil is provided in the form of a carrier metal foil with a carrier, a peeling layer, and the metal foil in sequence, and before the laser processing of the metal foil, the The carrier is peeled from the aforementioned laminate.

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