TWI699148B - Manufacturing method of multilayer wiring board - Google Patents

Abstract

The invention provides a method for manufacturing a multilayer wiring board, which has good circuit adhesion even when the circuit is extremely thin, and can effectively prevent the penetration of the circuit caused by laser processing. The manufacturing method of the multilayer wiring board includes: preparing a laminate including a metal foil, an insulating layer provided on the metal foil, and a first wiring layer provided on the surface of the insulating layer opposite to the metal foil; The process of applying laser processing from the surface of the metal foil to the formation of through holes; the process of applying plating and patterning to the side of the laminate where the through holes are formed to form a multilayer wiring board; the first wiring layer is at least with the aforementioned metal On the opposite side of the foil, the reflectance of the laser with a wavelength of 10.6 μm is over 80%, and the peak apex density Spd is 7000 pieces/mm ² or more and 15000 pieces/mm ² or less; the thickness T _{2 of the} metal foil is relative to the first The ratio T ₂ /T ₁ of the thickness T ₁ of the wiring layer is 0.23 or more.

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 of printed wiring boards and reduce their size, multilayer printed wiring boards have been widely used. Such multilayer printed wiring boards are used in various portable electronic devices for the purpose of weight reduction and miniaturization. Next, the multilayer printed wiring board is required to further reduce the thickness of the interlayer insulating layer, and to reduce the thickness and weight of the wiring board.

As a technology to meet such requirements, a manufacturing method of 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 stacked (stacked) to form multiple layers without using a so-called core substrate. In the coreless build-up method, in order to facilitate the peeling of the support and 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 laminated on the metal foil side of the metal foil with a carrier, and the metal layer is processed to form an inner layer circuit (first conductor pattern) In the inner layer circuit, the insulating layer and the metal foil are layered in sequence, and 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 and the inner layer circuit on both sides of the substrate are electrically connected to each other. Manufacturing method of connected wiring board. In addition, Patent Document 1 also discloses that laser processing is performed on both sides of the substrate to form through holes that penetrate the metal foil and insulating layer to the inner circuit, and the metal foils on both sides of the substrate are patterned with a dry film and then electroplated Fill the through-hole with plating metal, and form outer layer circuits (conductor patterns) 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, as the thickness of the multilayer printed wiring board has become more demanding, the thickness of the metal foil used in the circuit of the multilayer printed wiring board has also decreased. In this regard, in the production of the wiring board described in Patent Document 1, it is also desirable to use an extremely thin metal foil. However, when an existing ultra-thin copper foil (for example, a thickness of 6 μm or more and 12 μm or less) is used as a circuit (for example, an inner layer circuit), there is a process for forming through holes for interlayer connection, because laser processing is not only on both sides (outer layer) The metal foil and insulating layer also penetrate to the circuit and cause the problem of 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 (in other words, the thickness T _{2 of the} outer layer copper foil is relative to the inner layer When the ratio T ₂ /T _{1 of the} circuit thickness T ₁ is less than 1/4.5 (=0.22)), there is a risk of damage to the inner circuit when drilling holes caused by laser irradiation.

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

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

According to one aspect of the present invention, there is provided a method of manufacturing a multilayer wiring board, comprising: (a) preparing a metal foil, an insulating layer provided on the metal foil, and provided on the insulating layer on the opposite side of the metal foil (B) Applying laser processing to the laminate from the surface of the metal foil to form a laminate that penetrates the metal foil and the insulating layer to reach the first wiring layer Through hole process; (c) Apply plating 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 process of the board; wherein, at least the surface of the first wiring layer facing the metal foil has a reflectance of 80% or more of a laser with a wavelength of 10.6 μm as 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 as follows.

In this manual, the "reflectance of a laser with a wavelength of 10.6 μm" refers to the measurement by a Fourier transform infrared photometer (FT-IR) when a laser with a wavelength of 10.6 μm is irradiated on the surface of the sample (metal foil) relative to the surface of the sample (metal foil). 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 carried out using a commercially available Fourier transform infrared photometer, in accordance with the conditions described in the examples of this specification. In addition, because the wavelength of the carbon dioxide laser typically used in laser processing is 10.6 μm, the laser wavelength of the Fourier transform infrared photometer is set to 10.6 μm.

The "peak apex density Spd" in this specification refers to a parameter representing the number of peak apexes per unit area measured in accordance with 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, an area 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 the steps of (1) preparation of a laminate, (2) formation of via holes, and (3) formation of a second wiring layer.

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

(1) Preparation of laminated body A laminate 16 including a metal foil 10, an insulating layer 12 provided on the metal foil 10, and a first wiring layer 14 provided on the surface of the insulating layer 12 opposite to the metal foil 10 is prepared. This laminate 16 is typically one that corresponds to an intermediate product before peeling off the support in the manufacturing method of a multilayer wiring board such as the above-mentioned coreless laminate method. For example, as shown in Fig. 1(i), the laminate 16 may have 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 is buried between the insulating layer 12 and the insulating layer 12' to become an inner layer circuit. Alternatively, the laminate 16 is a form in which a metal foil or a wiring layer (not shown) (not shown) is laminated on the surface of the first wiring layer 14 via an insulating layer 12' (for example, a form in which metal foils are provided on both sides) It is also possible. In addition, the first wiring layer 14 may be provided in the insulating layer 12. In any case, the laminated body 16 should just include at least the metal foil 10, the insulating layer 12, and the 1st wiring layer 14, and it does not specifically limit about other layer structure.

The metal foil 10 may be a well-known structure used for metal foil for wiring layers. For example, the metal foil 10 may be formed by wet film formation methods such as electroless plating and electroplating methods, dry film formation methods such as sputtering and chemical vapor deposition, or a combination of these methods. As an example of the metal foil 10, aluminum, copper foil, stainless steel (SUS) foil, nickel foil, etc. are mentioned, Preferably it is copper foil. The copper foil may be 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 a carrier typically includes a carrier (not shown in the figure), a release layer (not shown in the figure), and the metal foil 10 in this order. The carrier is a foil or even a layer for supporting the metal foil 10 and improving its handleability. As preferred examples of the carrier, aluminum, copper foil, stainless steel (SUS) foil, resin film, resin film whose surface is metal-coated with copper or the like, resin plate, glass plate, and combinations thereof can be used. 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 it enables peeling of the carrier. For example, the peeling layer can be comprised by the well-known material used as the peeling layer of the metal foil with a carrier. The peeling layer may be any one of an organic peeling layer and an inorganic peeling layer, or 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 from the metal foil 10 in the process of forming the through hole described later.

The laminated body 16 may be attached to a support such as a prepreg (not shown) on one side to add rigidity. Prepreg is a general term for composite materials in which synthetic resin plates, glass plates, glass woven fabrics, glass non-woven fabrics, and paper are impregnated with synthetic resin. At this time, the metal foil with a carrier is attached symmetrically on both sides of the support, and the laminated body 16 is formed symmetrically on both sides of the temporarily laminated body with the support, and then the support and the It is better to remove the carrier together. For example, a metal foil with a carrier including a metal foil 10 is attached to a support, and the insulating layer 12 and the first wiring layer 14 are sequentially laminated and formed on the metal foil 10 to form a laminate 16. Alternatively, a metal foil with a carrier having 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 form a laminate体16. Thereby, the laminated body 16 prepared by the present invention may be produced by laminating or forming any one of the metal foil 10 and the first wiring layer 14 in advance.

The insulating layer 12 may be a well-known structure employing the insulating layer of the 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 subjecting the insulating resin material to hot stamping. Preferred examples of insulating resin impregnated in the prepreg used include epoxy resin, cyanate ester resin, bismaleimide triazine resin (BT resin), polyphenylene ether resin, phenol resin, etc. . In addition, as a preferable example of the insulating resin constituting the resin sheet, epoxy resin, polyimide resin, polyester fiber resin, and the like can be used. Furthermore, from the viewpoint of improving the insulation of the insulating layer 12, etc., filler particles composed of various inorganic particles such as silica and alumina may also be contained. 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 laminate 16 includes an insulating layer 12', the composition of the insulating layer 12' only needs to be the insulating layer 12. The above-mentioned preferred aspect of the insulating layer 12 is also applied to the insulating layer 12. '.

The first wiring layer 14 can be preferably formed by, for example, 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 an electroless plating method and an electroplating method, a dry film forming method such as sputtering and chemical vapor deposition, or a combination of these methods. Examples of the metal foil for the first wiring layer include aluminum foil, copper foil, stainless steel (SUS) foil, etc., and copper foil is preferred. The copper foil may be 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. If it is within this range, it is extremely suitable for fine circuit formation. The patterning used to form the first wiring layer 14 is performed by well-known methods such as the field subtractive process method, the MSAP (modified-semi-additive process) method, and the SAP (semi-additive) method. However, it is not particularly limited. When the insulating layer 12 or the insulating layer 12' is laminated on the first wiring layer 14, the inner layer treatment may be sequentially performed on the first wiring layer 14 in advance. It is preferable that the inner layer treatment includes roughening treatment such as CZ treatment. The CZ treatment uses an organic acid microetchant (for example, produced by MEC Co., Ltd., product number CZ-8101), and the surface of the first wiring layer 14 is finely roughened. Well done. Thereby, fine irregularities are formed on the surface of the first wiring layer 14, and the adhesion with the insulating layer to be laminated later can be improved.

At least the surface of the first wiring layer 14 facing the metal foil 10 has a reflectance of 80% or more of a laser with a wavelength of 10.6 μm as measured by a Fourier transform infrared spectrophotometer (FT-IR), and is based on ISO25178 The peak apex density Spd measured is 7000/mm ² or more and 15000/mm ² or less. By using a wiring layer that satisfies this condition as a circuit (for example, an inner layer circuit) to manufacture a multilayer wiring board, the circuit adhesion is good, and the penetration of the circuit caused by laser processing can be extremely effectively prevented.

That is, by setting the reflectance of a 10.6 μm laser with a wavelength of 10.6 μm measured by a 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 block Used for the absorption of laser light formed by the through hole. 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 It is possible to extremely effectively prevent penetration of the first wiring layer 14 by laser processing. The reflectance of the laser with a wavelength of 10.6 μm increases as the surface of the first wiring layer 14 is 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 is reduced, and circuit peeling is likely to occur. Therefore, it is not easy to balance prevention of circuit penetration due to laser processing and adhesion to the circuit. In this regard, in the present invention, the surface of the first wiring layer 14 facing the metal foil 10 maintains the smoothness that contributes to the improvement of the laser reflectivity with a wavelength of 10.6 μm, while reducing the peak apex density Spd is set to 7000 pcs/mm ² or more and 15000 pcs/mm ² or less, and it is possible to ensure the sinking of the first wiring layer 14 into the insulating layer 12 with a large number of contacts. As a result, while ensuring high circuit adhesion, it is possible to extremely effectively prevent penetration of the inner layer circuit caused by laser processing.

From the above point of view, the surface of the first wiring layer 14 facing the metal foil 10 has a reflectance of 80% or more of a laser with a wavelength of 10.6 μm measured by a Fourier transform infrared spectrophotometer (FT-IR). Preferably it is 85% or more, more preferably 90% or more, and even more preferably 95% or more. The upper limit is not particularly limited. Although it may be 100%, it is typically 98% or less. In addition, on the surface of the first wiring layer 14 facing the metal foil 10, the peak apex density Spd measured in accordance with ISO25178 is 7000 pieces/mm ² or more and 15000 pieces/mm ² or less, preferably 10,000 pieces/mm ² or more 15000 pieces/mm ² or less, more preferably 13000 pieces/mm ² or more and 15000 pieces/mm ² or less. Within the above-mentioned preferable range, it is possible to extremely effectively prevent penetration of the laser-processed first wiring layer 14 while further ensuring high circuit adhesion.

On the surface of the first wiring layer 14 facing the metal foil 10, the laser reflectivity of 10.6 μm in the above range and the peak apex density Spd are used to form the metal foil for the first wiring layer 14 The surface may be provided in advance, or may be applied to the surface of the first wiring layer 14 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, a metal foil for the first wiring layer having a surface that satisfies the above-mentioned conditions can be realized by subjecting the surface of the metal foil to a roughening treatment under known or even desired conditions. In addition, it is also possible to selectively purchase commercially available metal foils having surfaces that satisfy the above-mentioned conditions.

Like the surface of the first wiring layer 14 facing the metal foil 10, the surface of the first wiring layer 14 opposite to the metal foil 10 has the reflectance and peak apex density of a laser with a wavelength of 10.6 μm in the above range Spd can also. With this, it is possible to ensure high adhesion with the layer (for example, insulating layer 12') laminated on the side opposite to the metal foil 10 of the first wiring layer 14, and at the same time, from the side of the laminated body 16 opposite to the metal foil 10 When laser processing is applied to the surface of, the penetration of the first wiring layer 14 can also be prevented.

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 beam of the first wiring layer 14 can be suppressed. Damage caused by processing. 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 the first wiring layer 14 and/or the metal foil 10 is surface-treated before the laser processing (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 It 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 and the inner layer administering process, a thickness T ₁ of the first wiring layer 14 of the inner process.

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, particularly preferably 5 μm or more and 8 μm or less. If it is within this range, it is extremely advantageous for the thickness reduction required for a multilayer printed wiring board. 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, particularly preferably 1.5 μm or more and 2.0 μm or less . If it is within this range, it becomes easy to perform direct laser processing from the metal foil 10 to form the through hole 18 in the through hole forming process described later. In addition, when the metal foil 10 is used for the formation of a wiring layer, if it is within the above-mentioned thickness range, the formability for fine circuits is also good.

(2) Formation of through holes, as shown in FIG. 1(ii), by applying laser processing to the laminate 16 from the surface of the metal foil 10, the metal foil 10 and the insulating layer 12 are formed to penetrate the first wiring layer 14的通孔18。 Through hole 18. Although various lasers such as carbon dioxide lasers, excimer lasers, UV lasers, and YAG lasers can be used for laser processing, carbon dioxide lasers are particularly preferred. According to the method of the present invention, because the first wiring layer 14 has a surface that is difficult to absorb laser light, the penetration of the first wiring layer 14 caused by laser processing can be extremely effectively prevented in the process of forming the through hole. In particular, even when the output density of the laser is increased in order to perform the laser processing efficiently, it is difficult to cause penetration of the first wiring layer 14 according to the present invention. From this point of view, the laser output density in laser processing is preferably 8MW/cm ² or more and 14MW/cm ² or less, more preferably 8MW/cm ² or more and 12MW/cm ² or less, and still more preferably 9MW/cm ² Above 12MW/cm ^{2 and} below. Therefore, in the through hole 18 of the present invention, it is preferable to use the output density laser within the above-mentioned range to form each through hole with one shot of laser irradiation.

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. If it is in this range, it is extremely advantageous for the high density of a multilayer printed wiring board. Furthermore, in order to form the through hole 18 having the above-mentioned small diameter, it is preferable to reduce the beam diameter (spot diameter) of the laser. At this time, since the energy of the laser is likely to be concentrated in the laser-irradiated portion of the first wiring layer 14, penetration of the first wiring layer 14 is likely to occur originally. In this regard, according to the method of the present invention, since the first wiring layer 14 has a surface that hardly absorbs laser light, even when the energy of the laser is concentrated, the penetration of the first wiring layer 14 can be effectively prevented.

The process of forming the through hole, as a treatment to remove the resin residue (smear) 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 Desmear works better. The coplanarity process is a process in which swelling treatment, chromic acid treatment or permanganic acid treatment, and reduction treatment are sequentially performed, and a known wet process can be used. As an example of chromate, potassium chromate can be used. As an example of permanganate, sodium permanganate, potassium permanganate, etc. can be mentioned. In particular, it is preferable to use permanganate from the viewpoints of reduced discharge of environmentally hazardous substances in the desmear treatment solution and electrolytic regeneration.

(3) Formation of the second wiring layer As shown in FIG. 1(iii), plating and patterning are applied to the side of the laminate 16 where the through holes 18 are formed to form a second wiring layer 22 including the first wiring layer 14 and the metal foil 10 Multi-layer wiring board 24. Thereby, the plated metal is filled in the through hole 18, 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 metal derived from the metal foil 10, but may be formed as a new wiring layer (not including the metal derived from the metal foil 10) that only connects the surface profile of the metal foil 10. The method of forming the second wiring layer 22 is not particularly limited, and well-known methods such as a subtractive process method, MSAP method, and SAP method can be used. Here, Fig. 1(iii) shows the circuit formation by the MSAP method. As an example of circuit formation by the MSAP method, first, a photoresist (not shown) is formed in a predetermined pattern on the surface of the metal foil 10. The photoresist is preferably a photosensitive film. In this case, a predetermined wiring pattern can be applied to the photoresist by exposure and development. Next, an electroplating layer 20 is formed on the exposed surface of the metal foil 10 (that is, the part not shielded 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 plating may be performed by a known method, and it is not particularly limited. After the photoresist layer is peeled off, the metal foil 10 and the plating layer 20 are etched to obtain the multilayer wiring board 24 on which the second wiring layer 22 is formed.

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

Hereinafter, examples are used to further illustrate the present invention.

Examples 1～6 Six types of copper foils used as metal foils for forming inner layer circuits of multilayer wiring boards were prepared, and various evaluations were performed. The specific sequence is as follows.

(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 the others are specially produced by known methods. The measurement and calculation methods of the various parameters of the prepared copper foil are as follows.

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

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

(2) Evaluation of copper foil The various characteristics of the prepared copper foil were evaluated as follows.

<Laser processability> As shown in Figure 2, the copper foil prepared in (1) above was used as the metal foil for forming the inner layer circuit. The laminate for evaluating the laser processability was produced as follows to evaluate the laser processing Sex. First, a copper foil having a thickness of 2 μm is prepared as the metal foil 110, and a prepreg (manufactured by Mitsubishi Gas Chemical Co., Ltd., GHPL-830NSF) having a thickness of 0.02 mm is laminated as an insulating layer 112 on the metal foil 110. Next, the copper foil prepared in (1) above was used as the metal foil 113 for the first wiring layer, and laminated so that the surface having the parameters shown in Table 1 abutted on the insulating layer 112, and the pressure was 4.0 MPa , The temperature was 220°C for 90 minutes to perform hot press molding to obtain a first laminate 115 (FIG. 2(i)). After the surface of the metal foil 113 for the first wiring layer was etched for 1 μm with a microetching solution, a dry film was attached, and exposed and developed in a predetermined pattern to form an etching resist. The surface of the metal foil 113 for the first wiring layer was treated with a copper chloride etching solution, the copper was dissolved and removed from the etching resist, and the etching resist was peeled off to form the first wiring layer 114 to obtain the second laminate 116 (Figure 2(ii)). The surface of the first wiring layer 114 is roughened (CZ treatment). The thickness of the first wiring layer 114 after the roughening treatment was 7 μm. After that, a prepreg (manufactured by Mitsubishi Gas Chemical Co., Ltd., GHPL-830NSF) with a thickness of 0.02 mm and a copper foil with a thickness of 2 μm are respectively used as insulating layers 112' and The metal foil 110' is laminated in sequence, and is formed by hot-press printing at a pressure of 4.0 MPa and a temperature of 220°C for 90 minutes. Thereby, the laminated body 117 for laser processability evaluation was obtained (FIG. 2(iii)). In addition, 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 laser processability evaluation laminate 117 is 2/7=about 0.29. The obtained laminate 117 for evaluating laser processability was laser processed from the metal foil 110 side with a carbon dioxide laser with an output density of 9.5 MW/cm ² to form a penetrating metal foil 110 and an insulating layer 112 to reach the first The via hole 118 of the wiring layer 114 having a diameter of 65 μm (FIG. 2(iv)). This through hole 118 was observed with a metal microscope from the side of the metal foil 110 to determine the presence or absence of penetration of the first wiring layer 114. For each example, the formation and penetration determination of the through hole 118 were performed for each of the 88 holes. From the number of through holes 118 formed and the penetration number of the first wiring layer 114, the penetration of the first wiring layer 114 after laser processing was calculated rate.

<Circuit Adhesion>

Three prepregs (manufactured by Mitsubishi Gas Chemical Co., Ltd., GHPL-830NSF) with a thickness of 0.1mm are laminated, and the laminated prepreg will be prepared on the copper foil prepared in (1) above to have the respective values shown in Table 1. Laminated in such a way that the surfaces on the parameter side abut, A sample of copper clad laminated board was produced by hot press molding at a pressure of 4.0 MPa and a temperature of 220° C. for 90 minutes. A dry film was attached to both sides of the copper clad laminate sample to form an etching photoresist layer. Next, on the etching photoresist layer on both sides, a circuit for a peel strength measurement test with a width of 0.8 mm was exposed and developed to form an etching pattern. After that, the circuit is etched with a copper etching solution, and the etching photoresist is stripped to obtain a circuit. The circuit formed in this way (thickness 9 μm, circuit width 0.8 mm) was peeled off the surface of the prepreg in a 90° direction based on JIS C 6481-1996 to measure the peel strength (kgf/cm).

Examples 7~10

In place of the electrolytic copper foil having a thickness of 9 μm, an electrolytic copper foil having a thickness of 7 μm having the parameters shown in Table 1 on at least one side was used, and various characteristics were evaluated in the same manner as in Examples 1 to 6. 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 Except for 1) instead of copper foil with a thickness of 2 μm, a copper foil with a thickness of 3 μm was used as the metal foils 110 and 110', respectively, and 2) the amount of etching was adjusted to set the thickness of the first wiring layer 114 after roughening treatment (CZ treatment) to 5 m (i.e., the T ₂ / T ₁ is set to 3/5 = 0.60), and 3) the density of the carbon dioxide laser output is changed from 9.5MW / cm ² to 9.75MW / cm ^2, so the same manner as in Example 5 Lei Evaluation of injection processability.

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

Example 13 Except for 1) instead of 2μm thick copper foil, 3μm thick copper foil was used as the metal foils 110 and 110' respectively, and 2) the output density of the carbon dioxide laser was changed from 9.5MW/cm ² to 9.75MW/cm ² Other than that, the laser processability was evaluated in the same manner as in Example 8. In addition, the thickness of the first wiring layer 114 after the roughening treatment (CZ treatment) of the laminate 117 for evaluating laser workability was 5 μm, and T ₂ /T ₁ was 3/5=0.60.

Example 14 Except for 1) instead of copper foil with a thickness of 3μm, a copper foil with a thickness of 5μm was used as the metal foils 110 and 110', respectively, and 2) the output density of the carbon dioxide laser was changed from 9.75MW/cm ² to 10.25MW/cm ² Except for the above, 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 laminated body 117 for evaluating laser workability was 5 μm, and T ₂ /T ₁ was 5/5=1.0.

Example 15 Except for 1) instead of copper foil with a thickness of 3μm, a copper foil with a thickness of 5μm was used as the metal foils 110 and 110', respectively, and 2) the output density of the carbon dioxide laser was changed from 9.75MW/cm ² to 10.25MW/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 laminated body 117 for evaluating laser workability was 5 μm, and T ₂ /T ₁ was 5/5=1.0.

Example 16 Except for 1) instead of copper foil with a thickness of 3μm, a copper foil with a thickness of 5μm was used as the metal foils 110 and 110' respectively, and 2) the output density of the carbon dioxide laser was changed from 9.75MW/cm ² to 10.25MW/cm ² Other than that, the evaluation of laser processability was performed 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 laminated body 117 for evaluating laser workability was 5 μm, and T ₂ /T ₁ was 5/5=1.0.

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

10: Metal foil 12: Insulation layer 14: The first wiring layer 16: Layered body 12’: Insulation layer 18: Through hole 22: The second wiring layer 24: Multilayer wiring board 110: Metal foil 112: Insulation layer 113: The first metal foil 115: The first layer of integration 116: The second layer of integration 112’: Insulation layer 110’: Metal foil 118: Through hole 114: The first wiring layer 117: Laminated body for evaluating laser processability

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

10: Metal foil 12: Insulation layer 12’: Insulation layer 14: The first wiring layer 16: Layered body 18: Through hole 20: Electroplating layer 22: The 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 the surface of the insulating layer opposite to the metal foil (B) The process of applying laser processing to the laminate 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) Right The process of applying plating and patterning on the side of the laminate where the through holes are formed to form a multilayer wiring board including the first wiring layer and the second wiring layer from the metal foil; wherein, the first At least the surface of the wiring layer facing the aforementioned metal foil has a reflectance of more than 80% measured by a Fourier transform infrared spectrophotometer (FT-IR) for a laser with a wavelength of 10.6 μm and measured in accordance with ISO25178 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 the aforementioned T ₂ /T ₁ is 1.0 or less. The method according to claim 1 or 2, wherein the laser output density in the aforementioned 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-attached metal foil having a carrier, a release layer, and the metal foil in this order, and the metal foil is processed before laser processing The carrier is peeled from the aforementioned laminate.

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