TWI703909B - Manufacturing method of multilayer wiring board - Google Patents

Abstract

The invention provides a manufacturing method of a multilayer wiring board, which has good circuit adhesion and can effectively prevent the penetration of inner layer circuits caused by laser processing. The manufacturing method of the multilayer wiring board includes: (a) a process of sequentially laminating a first insulating layer and a second metal foil on a first metal foil to form a first laminate; (b) forming a second wiring layer Process; (c) The process of laminating the second insulating layer and the third metal foil in order to form the second laminate; (d) The process of forming the first through hole and the second through hole; (e) The process of forming the second layer 1 Wiring layer, 2nd wiring layer and 3rd wiring layer multilayer wiring board; at least the surface of the second metal foil opposite to the first insulating layer, measured by Fourier transform infrared spectrophotometer (FT-IR) The reflectance of the laser with a wavelength of 10.6μm is 80% or more, and the peak apex density Spd measured according to ISO25178 is 7000/mm ² or more and 15000/mm ² or less.

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 miniaturization of printed wiring boards, multilayer printed wiring boards have been widely used. Such multilayer printed wiring boards are used for the purpose of weight reduction and miniaturization in various portable electronic devices. 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 this requirement, 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 to form a substrate with metal foil on both sides of the inner layer circuit. Then, the metal foil and the inner layer circuit on both sides of the substrate are electrically connected through the holes. Manufacturing method of 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 insulating layer to the inner layer circuit, and the metal foil on both sides of the substrate is 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

In recent years, as the thickness of the multilayer printed wiring board has become more demanding, the thickness of the metal foil used for the inner circuit of the multilayer wiring board (hereinafter referred to as "inner metal foil") 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 inner layer 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 an inner layer metal foil, there is a process of forming through holes for interlayer connection, because laser processing is not only the metal on both sides (outer layer) The foil and the insulating layer also penetrate the inner circuit and cause the problem of holes.

The inventors have now obtained the manufacture of multilayer wiring boards by using a metal foil on a specific surface that has a 10.6 μm wavelength laser reflectance and peak apex density Spd satisfying predetermined conditions as an inner metal foil. It has good adhesion and can effectively prevent the penetration of the inner 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 and can extremely effectively prevent the penetration of the inner layer circuit caused by laser processing.

According to one aspect of the present invention, there is provided a method for manufacturing a multilayer wiring board, comprising: (a) a process of sequentially laminating a first insulating layer and a second metal foil on a first metal foil to form a first laminate (B) The process of patterning the second metal foil to form a second wiring layer; (c) The second insulating layer and the third metal foil are formed on the first layered body forming the second wiring layer The process of laminating sequentially to form a second laminate; (d) applying laser processing to the second laminate from each of the first metal foil and the third metal foil to form a penetrating through the first metal The process in which the foil and the first insulating layer reach the first through hole of the second wiring layer, and the second through hole that penetrates the third metal foil and the second insulating layer to reach the second wiring layer; (e) Yes Both surfaces of the second laminate are plated and patterned to form electrical connections through the first through hole, the second wiring layer, and the second through hole to form a first insulating layer adjacent to the first insulating layer. The wiring layer, the second wiring layer from the second metal foil, and the multilayer wiring board of the third wiring layer adjacent to the second insulating layer; wherein, the second metal foil is at least insulated from the first On the opposite side of the layer, the reflectance of a 10.6μm laser measured by Fourier Transform Infrared Spectrophotometer (FT-IR) is 80% or more, and the peak apex density Spd measured according to ISO25178 is 7000 Pieces/mm ² or more and 15000 pieces/mm ² or less.

[Implementation form]

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 of the laser with a wavelength of 10.6 μm relative to the surface of the sample (metal foil) measured by a Fourier transform infrared photometer (FT-IR). The ratio of the amount of light reflected by the reference plate (for example, an Au vapor deposition mirror) to the amount of light reflected by the sample. The measurement of the reflectance of a laser with a wavelength of 10.6 μm can be carried out using a commercially available Fourier transform infrared photometer under the conditions described in the examples of this specification. In addition, since 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 that indicates 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 with a commercially available laser microscope.

The "ten-point average roughness Rz" in this manual refers to a parameter that can be determined based on JIS B 0601-1994. In the rough curve of the reference length, the average of the peak height from the highest peak to the fifth highest , And the sum of the average value from the deepest valley bottom to the fifth deepest valley depth.

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) formation of a first laminate, (2) formation of a second wiring layer, (3) formation of a second laminate, (4) peeling of the carrier as required, (5) Formation of the first and second via holes, (6) Formation of the first and third wiring layers.

Hereinafter, referring to FIGS. 1 to 3, each of the processes (1) to (6) will be described.

(1) Formation of the first layered body As shown in Fig. 1 (i) and (ii), a first metal foil 16 is prepared, and a first insulating layer 18 and a second metal foil 20 are sequentially laminated on the first metal foil 16 to form a first laminate twenty two. The first metal foil 16 may be provided in the form of the metal foil 10 with a carrier. The metal foil with carrier 10 typically includes a first carrier 12, a first peeling layer 14, and a first metal foil 16 in this order. In addition, the various layers described above may be sequentially provided on both surfaces of the first carrier 12 so as to be vertically symmetrical. Alternatively, the first carrier 12 side of the metal foil 10 with a carrier may be attached to a temporary support (not shown) such as a prepreg to add rigidity. At this time, the metal foil 10 with a carrier is attached to both sides of the temporary support in a symmetrical manner up and down, and the layers described below are formed in a symmetrical manner on both sides of the resulting laminate, and then the temporary support and the first carrier It is better to remove 12 together. In addition, prepreg is a general term for composite materials in which synthetic resin is impregnated into synthetic resin plates, glass plates, glass woven fabrics, glass non-woven fabrics, and paper.

The first carrier 12 is a foil or a layer for supporting the first metal foil 16 and improving the handleability. As a preferred example of the first carrier 12, aluminum, copper foil, stainless steel (SUS) foil, resin film, resin film coated with metal such as copper on the surface, resin plate, glass plate, and combinations thereof . The thickness of the first carrier 12 is typically 5 μm or more and 250 μm or less, preferably 9 μm or more and 200 μm or less.

The material of the first peeling layer 14 is not particularly limited as long as it is a layer that enables peeling of the first carrier 12. For example, the first peeling layer 14 can be made of a known material used as a peeling layer of metal foil with a carrier. The first peeling layer 14 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.

The first metal foil 16 may be a well-known configuration of metal foil for a wiring layer used in the coreless build-up method. For example, the first metal foil 16 may be formed by wet film formation methods such as electroless plating and electroplating, dry film formation methods such as sputtering and chemical vapor deposition, or a combination of these methods. Examples of the first metal foil 16 may be aluminum, copper foil, stainless steel (SUS) foil, nickel foil, etc., and copper foil is preferred. The copper foil may be rolled copper foil or electrolytic copper foil. Furthermore, the thickness of the first metal foil 16 is preferably 0.1 μm or more and 12 μm or less, more preferably 0.5 μm or more and 9 μm or less, still more preferably 1 μm or more and 7 μm or less, particularly preferably 1.5 μm or more and 5 μm or less. If it is within such a range, it becomes easy to form a through hole by direct laser processing from the first metal foil 16 in a through hole forming process described later. In addition, when the first metal foil 16 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.

The first insulating layer 18 may be a well-known configuration of an insulating layer used in the coreless build-up method, and is not particularly limited. For example, the first insulating layer 18 is more preferably formed by laminating an insulating resin material such as a prepreg and a resin sheet on the first metal foil 16 and then subjecting it to hot stamping. As a preferable example of the insulating resin impregnated in the prepreg used, epoxy resin, cyanate ester resin, bismaleimide triazine resin (BT resin), polyphenylene ether resin, phenol resin, etc. . Moreover, 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. In addition, from the viewpoint of improving insulation properties of the first insulating layer 18, filler particles composed of various inorganic particles such as silica and alumina may be contained. Although the thickness of the first insulating layer 18 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 first insulating layer 18 may be composed of a plurality of layers.

At least the surface of the second metal foil 20 facing the first insulating layer 18 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), and is based on ISO25178 The peak apex density Spd measured as a reference is 7000/mm ² or more and 15000/mm ² or less. By using the metal foil that meets this condition as the inner metal foil (that is, the second metal foil 20) to manufacture the multilayer wiring board, the circuit adhesion is good and the laser processing can be extremely effectively prevented The penetration of the inner layer circuit (that is, the second metal foil 20).

That is, it is effective 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 second metal foil 20 facing the first insulating layer 18 to 80% or more. The ground hinders the absorption of laser light used for through-hole formation. As a result, it is possible to extremely effectively prevent penetration of the second wiring layer 24 from the second metal foil 20 due to laser processing. The reflectance of the laser with a wavelength of 10.6 μm increases as the surface of the second metal foil 20 is smoother. However, if the surface of the second metal foil 20 is simply smoothed in order to increase the laser reflectivity, the adhesion between the second metal foil 20 and the first insulating layer 18 will decrease, and circuit peeling will easily occur. Therefore, it is not easy to balance the prevention of penetration of the inner layer circuit caused by laser processing and the adhesion to the circuit. In this regard, in the present invention, the surface of the second metal foil 20 opposite to the first insulating layer 18 maintains the smoothness that contributes to the improvement of the reflectance of the laser with a wavelength of 10.6 μm, while reducing the peak The vertex 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 second metal foil 20 into the first insulating layer 18 with a large number of contacts. As a result, while ensuring high circuit adhesion, it is extremely effective to prevent penetration of the inner layer circuit caused by laser processing.

From the above point of view, the surface of the second metal foil 20 facing the first insulating layer 18 has a reflectivity of 80% for a laser with a wavelength of 10.6 μm measured by a Fourier transform infrared spectrophotometer (FT-IR) Above, preferably 85% or more, more preferably 90% or more, and still more preferably 95% or more. The upper limit is not particularly limited, and although it may be 100%, it is typically 98% or less. In addition, the surface of the second metal foil 20 facing the first insulating layer 18 has a peak apex density Spd of 7000/mm ² or more and 15000/mm ² or less, preferably 10000 15000 pieces/mm ² or more/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, the laser-processed second wiring layer 24 can be prevented from penetrating extremely effectively while ensuring high circuit adhesion.

Preferably, the ten-point average roughness Rz of the surface facing the first insulating layer 18 in the second metal foil 20 is 0.2 μm or more and 2.0 μm or less, more preferably 0.5 μm or more and 1.8 μm or less, and still more preferably 0.8 μm or more 1.5μm or less. Within this range, it is possible to further improve the formation of fine circuits.

On the surface of the second metal foil 20 facing the first insulating layer 18, the laser reflectivity of the wavelength 10.6μm, the peak apex density Spd, and the ten-point average roughness Rz in the above range can be applied to the copper foil The surface is realized by roughening the surface under known and even desired conditions. Therefore, the surface of the second metal foil 20 that faces the first insulating layer 18 is preferably a roughened surface. In addition, it is also possible to selectively purchase commercially available copper foils having surfaces that satisfy the above-mentioned conditions.

The second metal foil 20 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 second metal foil 20 may be 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 second metal foil 20 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 miniaturized circuit formation. In addition, the second metal foil 20 may be provided in the form of a metal foil with a carrier including a second carrier (not shown), a second release layer (not shown), and a second metal foil 20 in this order. In this case Here, after the second metal foil 20 is laminated on the first insulating layer 18 and before the second wiring layer 24 is formed, the second carrier may be peeled from the first laminate 22. The configurations of the second carrier and the second release layer may be those that are used in the first carrier 12 and the first release layer 14 described above, and are not particularly limited.

(2) Formation of the second wiring As shown in FIG. 1(iii), the second wiring layer 24 is formed by patterning the second metal foil 20. The patterning can be performed by a known technique. A preferable circuit formation method may be to leave the second metal foil 20 as it is or use as a part of the method to form the second wiring layer 24, and it is more preferable that the second metal foil 20 is not plated or the like, and the second metal foil 20 The method of forming the second wiring layer 24 is used as it is. As a preferable example of such a method capable of circuit formation, a subtractive process method may be used. As an example of circuit formation by the subtractive process method, a dry film is first attached to the surface of the second metal foil 20, and exposed and developed in a predetermined pattern to form an etching resist (not shown). Next, by treating the metal constituting the second metal foil 20 with a soluble etching solution, the metal exposed from the etching resist is dissolved and removed, and the etching resist can be peeled off to form the second wiring layer 24.

The process of forming the second wiring layer 24 preferably further includes a process of applying an inner layer treatment to the second wiring layer 24. The inner layer treatment includes roughening treatments such as CZ treatment. The CZ treatment uses an organic acid microetching agent (for example, produced by MEC Co., Ltd., product number CZ-8101), and the surface of the second wiring layer 24 is finely roughened. Well done. Thereby, fine irregularities are formed on the surface of the second wiring layer 24, and the adhesion between the second wiring layer 24 and the second insulating layer 26 in the process of forming a second laminate described later can be improved.

The thickness of the second wiring layer 24 is preferably 3 μm or more and 12 μm or less, more preferably 5 μm or more and 10 μm or less, and still more preferably 5 μm or more and 8 μm or less. If it is in this range, it is extremely advantageous for the thickness reduction required for a multilayer printed wiring board. In addition, according to the method of the present invention, even when the thickness of the second wiring layer 24 is as thin as described above, it is possible to effectively prevent penetration accompanied by laser processing. In addition, when the second wiring layer 24 is subjected to the above-mentioned inner layer treatment, the thickness of the second wiring layer 24 after the inner layer treatment is desirably within the above-mentioned range.

(3) Formation of the second layered body As shown in FIG. 2(iv), the second insulating layer 26 and the third metal foil 28 are laminated on the first laminate 22 where the second wiring layer 24 is formed to form the second laminate 30. Thereby, the second wiring layer 24 becomes an inner layer circuit buried between the first insulating layer 18 and the second insulating layer 26. The configuration of the second insulating layer 26 and the third metal foil 28 may be applied to each of the first insulating layer 18 and the first metal foil 16. Therefore, the preferred aspects of the first metal foil 16 and the first insulating layer 18 can also be applied to each of the third metal foil 28 and the second insulating layer 26. In addition, the third metal foil 28 may be provided in the form of a metal foil with a carrier including a third carrier (not shown), a third release layer (not shown), and a third metal foil 28 in this order. The configurations of the third carrier and the third release layer may be those that are used in the first carrier 12 and the first release layer 14 described above, and are not particularly limited.

The surface of the second wiring layer 24 facing the second insulating layer 26 has a reflectance of a laser with a wavelength of 10.6 μm measured by a Fourier transform infrared spectrophotometer (FT-IR) of 80% or more, preferably 85 % Or more, more preferably 90% or more, still more preferably 95% or more. The upper limit is not particularly limited, and although it may be 100%, it is typically 98% or less. In addition, the surface of the second wiring layer 24 facing the second insulating layer 26 has a peak apex density Spd measured in accordance with ISO 25178 of 7000/mm ² or more and 15000/mm ² or less, preferably 10000 15000 pieces/mm ² or more/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, while ensuring high adhesion between the second wiring layer 24 and the second insulating layer 26, it is also possible to prevent the second wiring layer 24 from being damaged during laser processing from the third metal foil 28. Run through. On the surface of the second wiring layer 24 facing the second insulating layer 26, the laser reflectance of 10.6 μm and the peak apex density Spd in the above range are provided, although the surface of the second metal foil 20 may be provided with However, the inner layer treatment (for example, roughening treatment such as CZ treatment) may be applied to the surface of the second wiring layer 24 afterwards. Therefore, the surface of the second wiring layer 24 that faces the second insulating layer 26 is preferably a roughened surface.

Preferably the first metal foil thickness T 16 of ₁ with respect to the thickness of the second wiring layer 24 T ₂ of the ratio T ₁ / T ₂ is 0.23 or more, and a thickness / or the third metal foil 28 with respect to T ₃ of the second The ratio T ₃ /T ₂ of the thickness T ₂ of the wiring layer 24 is 0.23 or more. More preferably, both of T ₁ /T ₂ and T ₃ /T ₂ are 0.23 or more. According to the present invention, since the second wiring layer 24 from the second metal foil 20 has a surface that hardly absorbs laser light, even if the second metal foil 20 is extremely thinned to satisfy the above range, the inner layer circuit can be suppressed. That is, damage caused by the laser processing of the second wiring layer 24. T ₁ /T ₂ and/or T ₃ /T _{2 are} 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 metal foil or the wiring layer before laser processing (even if the thickness of the metal foil or the wiring layer changes), the above T ₁ , T ₂ and T ₃ refer to the first metal after the surface treatment. The thickness of the foil 16, the thickness of the second wiring layer 24, and the thickness of the third metal foil 28. For example, when the second wiring layer 24 is subjected to the above-mentioned inner layer treatment, T ₂ becomes the thickness of the second wiring layer 24 after the inner layer treatment.

(4) Stripping of the carrier (arbitrary engineering) When the first metal foil 16 and/or the third metal foil 28 are provided in the form of a metal foil with a carrier, as shown in FIG. 2(v), the first carrier 12 and/or the third carrier (not shown) are removed from the The two-layered product 30 peeled off. Thereby, in the process of forming the first and second through holes to be described later, laser processing can be performed from each of the first metal foil 16 and the third metal foil 28. In addition, the rigidity of the second laminate 30 is increased by the first insulating layer 18 and the second insulating layer 26, and sufficient handling properties can be ensured even in a state where the carrier is peeled off. In addition, when the metal foil with a carrier is attached to a temporary support (not shown) such as a prepreg as described above, the temporary support is removed from the second layer together with the first carrier 12 and/or the third carrier (not shown). The integrated body 30 is removed.

(5) Formation of the first and second through holes As shown in FIG. 3(vi), by applying laser processing to the second laminate 30 from each of the first metal foil 16 and the third metal foil 28, the first metal foil 16 and the first insulation are formed. The layer 18 reaches the first through hole 32 of the second wiring layer 24 and the second through hole 34 that penetrates the third metal foil 28 and the second insulating layer 26 to reach the second wiring layer 24. 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, the penetration of the second wiring layer 24 caused by laser processing can be effectively prevented in the process of forming the through hole.

The process of forming the first and second through-holes, as a treatment to remove the resin residue (smudge) at the bottom of the through-hole generated when the through-hole is formed by laser processing, includes the use of chromate solution and permanganate solution At least one of the slag removal engineering is 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. may be mentioned. In particular, it is preferable to use permanganate from the viewpoints of reduced discharge of environmentally hazardous substances in the desmear treatment liquid and electrolytic regeneration.

The diameter of the first through hole 32 and the second through hole 34 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 a through hole having a small diameter as described above, 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 on the laser-irradiated portion of the second wiring layer 24, penetration of the second wiring layer 24 is likely to occur originally. In this regard, according to the method of the present invention, because the second wiring layer 24 from the second metal foil 20 has a surface that is difficult to absorb laser light, even when the energy of the laser is concentrated, the second wiring layer can be effectively prevented The penetration of 24.

(6) Formation of the first and third wiring As shown in 3(vii), both sides of the second laminate 30 are plated and patterned to form electrical connections through the first through hole 32, the second wiring layer 24, and the second through hole 34 to form an electrical connection including The multilayer wiring board 42 of the first wiring layer 38 adjacent to the first insulating layer 18, the second wiring layer 24 from the second metal foil 20, and the third wiring layer 40 adjacent to the second insulating layer 26. The first wiring layer 38 is typically derived from the first metal foil 16, and typically includes metal derived from the first metal foil 16, but as a new wiring layer that only follows the surface profile of the first metal foil 16 (not including The metal derived from the first metal foil 16 may be formed. Similarly, the third wiring layer 40 is typically derived from the third metal foil 28, and typically contains metal derived from the third metal foil 28, but serves as a new wiring layer that only follows the surface profile of the third metal foil 28 ( It does not include the metal derived from the third metal foil 28). The method of forming the first wiring layer 38 and the third wiring layer 40 is not particularly limited, and the subtractive process method, MSAP (modified-semi-additive process) method, SAP (semi-additive process) method can be used. (Addition) method and other well-known methods. Here, Fig. 3 (vii) 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 surfaces of the first metal foil 16 and the third metal foil 28. The photoresist is preferably a photosensitive film. In this case, the predetermined wiring pattern can be applied to the photoresist by exposure and development. Next, a plating layer 36 is formed on the exposed surfaces of the first metal foil 16 and the third metal foil 28 (that is, the portion not shielded by the photoresist layer), and the first through hole 32 and the second through hole 34. At this time, since the first through hole 32 and the second through hole 34 are filled with plated metal, both surfaces of the second laminate 30 are electrically connected by the first through hole 32, the second wiring layer 24, and the second through hole 34. Electroplating may be performed by a known method, and it is not particularly limited. After the photoresist layer is peeled off, the first metal foil 16, the third metal foil 28, and the plating layer 36 are etched to obtain a multilayer wiring board 42 in which the first wiring layer 38 and the third wiring layer 40 are formed.

A build-up wiring layer may be further formed on the multilayer wiring board 42. That is, by alternately layering wiring layers including insulating layers and wiring patterns on the multilayer wiring board 42, it is possible to obtain the n-th wiring layer (n is an integer greater than or equal to 4, more preferably 5, 7, Multilayer wiring boards up to the odd number of 9). 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 inner layer metal foils of multilayer wiring boards were prepared, and various evaluations were performed. The specific sequence is as follows.

(1) Preparation of copper foil Six kinds of electrolytic copper foils having a thickness of 12 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 each parameter 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 conditions described below to obtain an IR spectrum data. By analyzing the obtained 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 -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 cut-off wavelength of the S filter is 0.8μm, and the magnification is 2000 times (measurement area 107μm×143μm), and the surface of copper foil is measured according to ISO25178. The apex density of the peak is Spd.

(Ten point average roughness Rz) Using a laser microscope (manufactured by Keynes Co., Ltd., VK-X100), the ten-point average roughness of the copper foil surface was measured under the conditions of a magnification of 2000 times, a cut-off value of 0.8 μm, and a measuring length of 100 μm according to JIS B 0601-1994 Rz.

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

<Laser processability> The copper foil prepared in (1) above was used as the inner layer metal foil, and the laminate for laser processability evaluation was produced as follows. First, a copper foil with a thickness of 2 μm is prepared as the first metal foil 16, and a prepreg (manufactured by Mitsubishi Gas Chemical Co., Ltd., GHPL-830NSF) with a thickness of 0.02 mm is used as the first insulating layer 18 on the first metal foil 16 product. Next, as the second metal foil 20, the copper foil prepared in (1) above was laminated so that the surface having the parameters shown in Table 1 abutted on the first insulating layer 18, and the pressure was 4.0 MPa , The temperature is 220° C., and the first layered body 22 is obtained by hot imprint molding for 90 minutes. After the surface of the second metal foil 20 is etched with a microetching solution for 1 μm, a dry film is attached, and exposed and developed in a predetermined pattern to form an etching resist. The surface of the second copper foil is treated with a copper chloride etching solution, and after the copper is dissolved and removed from the etching resist, the etching resist is peeled off to form the second wiring layer 24. The surface of the second wiring layer 24 is roughened (CZ treatment). The thickness of the second wiring layer 24 after the roughening treatment was 9 μm. Therefore, the ratio T ₁ /T ₂ of the thickness T ₁ (2 μm) of the first metal foil to the thickness T ₂ (9 μm) of the second wiring layer is 2/9=about 0.22. Thereafter, 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 were respectively used as the second insulating layer 26 on the first laminate 22 on which the second wiring layer 24 was formed. The third metal foil 28 and the third metal foil 28 are sequentially laminated, and are formed by hot embossing at a pressure of 4.0 MPa and a temperature of 220° C. for 90 minutes. Thereby, a laminate for evaluating laser workability was obtained. The obtained laminate for evaluating the laser processability was laser-processed from the first metal foil 16 side with an output density of 9.5 MW/cm ² using a carbon dioxide laser to form a penetrating first metal foil 16 and a first insulation The layer 18 reaches the 65 μm diameter through hole of the second wiring layer 24. This through hole was observed with a metal microscope from the side of the first metal foil 16 to determine the presence or absence of penetration of the second wiring layer 24. Regarding each example, the formation of through holes and the penetration determination were performed for every 88 holes, and the penetration rate of the second wiring layer 24 after laser processing was calculated from the number of through holes formed and the penetration number of the second wiring layer 24.

＜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 in the copper foil prepared in (1) above to have the respective Laminated in such a way that the surface on the parameter side was in contact with each other, and a copper-clad laminated board sample was produced by hot stamping 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 0.8 mm width peel strength measurement test circuit was exposed and developed to form an etching pattern. After that, the circuit is etched with a copper etching solution, and the etching resist is stripped to obtain a circuit. The circuit formed in this way (thickness 12 μm, circuit width 0.8 mm) was peeled off the surface of the prepreg in a 90° direction in accordance with JIS C 6481-1996 to measure the peel strength (kgf/cm).

<Circuit formation> Electroplating was performed on the surface of the above-mentioned copper clad laminate until the circuit height became 20 μm. A dry film is attached to the surface of the electroplated layer formed in this way, and exposed and developed to form an etching resist. The copper chloride etching solution is used to dissolve and remove copper from between the etching resists to form a linear wiring pattern with a circuit height of 20 μm and a line/space=25 μm/25 μm. The linear wiring pattern thus obtained was observed by SEM from directly above (observation angle 0°) under the condition of 1000 times magnification. Attach the acquired SEM image to a digital microscope (manufactured by Keyence Corporation, VHX-500), and measure the width of the bottom of the circuit at 100 points. From the measurement results, instead of the average value, the standard deviation σ (μm) is calculated using the median value, and 3σ-(-3σ), that is, 6σ, is adopted as the value of circuit linearity.

Examples 7 to 12 Instead of the electrolytic copper foil having a thickness of 12 μm, the various characteristics were evaluated in the same manner as in Examples 1 to 6 except that an electrolytic copper foil having a thickness of 9 μm having the parameters shown in Table 1 was used on at least one side. In addition, the thickness of the second wiring layer 24 after the roughening treatment (CZ treatment) of the laminate for laser processability evaluation was 7 μm, and T ₁ /T ₂ was 2/7=about 0.29.

Examples 13 to 16 In place of the electrolytic copper foil having a thickness of 12 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 was used on at least one side. In addition, the thickness of the second wiring layer 24 after the roughening treatment (CZ treatment) of the laminate for laser processability evaluation was 5 μm, and T ₁ /T ₂ was 2/5=about 0.40.

result The evaluation results obtained in Examples 1 to 16 are shown in Table 1.

Example 17 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 first metal foil 16 and the third metal foil 28 respectively; 2) the second wiring after the roughening treatment (CZ treatment) was adjusted by adjusting the etching amount the thickness of layer 24 to 5 m (i.e., the T ₁ / T ₂ 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 / outside cm ^2, and Example 11 was also evaluated for laser processability.

Example 18 Except for 1) instead of copper foil with a thickness of 2μm, a copper foil with a thickness of 3μm was used as the first metal foil 16 and the third metal foil 28, respectively, and 2) the output density of the carbon dioxide laser was changed from 9.5MW/cm ² to Except for 9.75 MW/cm ² , the laser processability was evaluated in the same manner as in Example 16. In addition, the thickness of the second wiring layer 24 after the roughening treatment (CZ treatment) of the laminate for laser processability evaluation was 5 μm, and T ₁ /T ₂ was 3/5=about 0.60.

Example 19 Except for 1) instead of copper foil with a thickness of 2μm, a copper foil with a thickness of 3μm was used as the first metal foil 16 and the third metal foil 28, respectively, and 2) the output density of the carbon dioxide laser was changed from 9.5MW/cm ² to Except for 9.75 MW/cm ² , the laser processability was evaluated in the same manner as in Example 14. In addition, the thickness of the second wiring layer 24 after the roughening treatment (CZ treatment) of the laminate for laser processability evaluation was 5 μm, and T ₁ /T ₂ was 3/5=about 0.60.

Example 20 Except for 1) instead of copper foil with a thickness of 2μm, a copper foil with a thickness of 3μm was used as the first metal foil 16 and the third metal foil 28, respectively, and 2) the output density of the carbon dioxide laser was changed from 9.75MW/cm ² to Except for 10.25 MW/cm ² , the laser processability was evaluated in the same manner as in Example 17. In addition, the thickness of the second wiring layer 24 after the roughening treatment (CZ treatment) of the laminate for laser processability evaluation was 5 μm, and T ₁ /T ₂ was 5/5=about 1.0.

Example 21 Except for 1) instead of copper foil with a thickness of 2 μm, copper foil with a thickness of 3 μm was used as the first metal foil 16 and the third metal foil 28, respectively, and 2) the output density of the carbon dioxide laser was changed from 9.75MW/cm ² to Except for 10.25 MW/cm ² , the laser processability was evaluated in the same manner as in Example 18. In addition, the thickness of the second wiring layer 24 after the roughening treatment (CZ treatment) of the laminate for laser processability evaluation was 5 μm, and T ₁ /T ₂ was 5/5=about 1.0.

Example 22 Except 1) instead of copper foil with a thickness of 2μm, a copper foil with a thickness of 5μm was used as the first metal foil 16 and the third metal foil 28, respectively, and 2) the output density of the carbon dioxide laser was changed from 9.75MW/cm ² to Except for 10.25 MW/cm ² , the laser processability was evaluated in the same manner as in Example 19. In addition, the thickness of the second wiring layer 24 after the roughening treatment (CZ treatment) of the laminate for laser processability evaluation was 5 μm, and T ₁ /T ₂ was 5/5=about 1.0.

result The evaluation results obtained in Examples 17-22 are shown in Table 2.

16‧‧‧The first metal foil 18‧‧‧The first insulation layer 20‧‧‧Second metal foil 22‧‧‧The first layer of integration 10‧‧‧Metal foil with carrier 12‧‧‧Carrier 1 14‧‧‧The first peeling layer 24‧‧‧2nd wiring layer 26‧‧‧Second insulation layer 28‧‧‧The third metal foil 30‧‧‧Layer 2 32‧‧‧1st through hole 34‧‧‧2nd through hole 40‧‧‧3rd wiring layer 42‧‧‧Multilayer wiring board 38‧‧‧The first wiring layer 36‧‧‧Plating layer

[Fig. 1] A process flow chart showing initial processes (processes (i) to (iii)) in an example of the manufacturing method of the present invention. [Fig. 2] A process flow chart showing a series of processes (processes (iv) to (v)) following the process shown in Fig. 1 in the manufacturing method of the present invention. [FIG. 3] A process flow chart showing a series of processes (processes (vi) to (vii)) following the process shown in FIG. 2 in the manufacturing method of the present invention.

16‧‧‧The first metal foil

18‧‧‧The first insulation layer

24‧‧‧2nd wiring layer

26‧‧‧Second insulation layer

28‧‧‧The third metal foil

30‧‧‧Layer 2

32‧‧‧1st through hole

34‧‧‧2nd through hole

36‧‧‧Plating layer

38‧‧‧The first wiring layer

40‧‧‧3rd wiring layer

42‧‧‧Multilayer wiring board

Claims (10)

A method of manufacturing a multilayer wiring board includes: (a) a process of sequentially laminating a first insulating layer and a second metal foil on a first metal foil to form a first laminate; (b) for the second metal The process of applying foil patterning to form a second wiring layer; (c) Laminating a second insulating layer and a third metal foil in sequence on the first laminate that forms the second wiring layer to form a second laminate (D) Laser processing is applied to the second laminate from each of the first metal foil and the third metal foil to form the first metal foil and the first insulating layer to penetrate the The first through hole of the second wiring layer, and the process of penetrating the third metal foil and the second insulating layer to the second through hole of the second wiring layer; (e) on both sides of the second laminate, Plating and patterning are applied to form electrical connections through the first through hole, the second wiring layer, and the second through hole to form a first wiring layer that is adjacent to the first insulating layer, and the second metal foil The second wiring layer and the multilayer wiring board of the third wiring layer adjacent to the second insulating layer; wherein at least the surface of the second metal foil facing the first insulating layer is obtained by Fourier The reflectance of the 10.6μm laser measured by the conversion infrared spectrophotometer (FT-IR) is 80% or more, and the peak apex density measured according to ISO25178 is 7000 pieces/mm ² or more and 15000 pieces/mm ² or less. The method according to claim 1, wherein the ten-point average roughness Rz of the surface facing the first insulating layer in the second metal foil is 0.2 μm or more and 2.0 μm or less. The method according to claim 1 or 2, wherein the surface of the second wiring layer facing the second insulating layer is measured by a Fourier transform infrared spectrophotometer (FT-IR) with a 10.6 μm laser The reflectance of the slab is 80% or more, and the peak apex density Spd measured based on ISO25178 is 7000/mm ² or more and 15000/mm ² or less. The method according to claim 1 or 2, wherein the thickness of the second wiring layer is 3 μm or more and 12 μm or less. The method according to claim 1 or 2, wherein the first metal foil, the second metal foil, and the third metal foil are all copper foils. The method according to claim 1 or 2, wherein the thickness of each of the first metal foil and the third metal foil is 0.1 μm or more and 12 μm or less. The method as requested item claim 1 or 2, wherein the thickness of the first metal foil a T ₁ with respect to the thickness of the second wiring layer T ₂ of the ratio T ₁ / T ₂ is 0.23 or more, and / or the third metal the thickness T ₃ of the foil relative to the thickness of the second wiring layer T ₂ of the ratio T ₃ / T ₂ is 0.23 or more. The method according to claim 7, wherein the aforementioned T ₁ /T ₂ is 1.0 or less, and/or the aforementioned T ₃ /T ₂ is 1.0 or less. The method according to claim 1 or 2, wherein the diameters of the first through hole and the second through hole are both 30 μm or more and 80 μm or less. The method according to claim 1 or 2, wherein the first metal foil is provided in the form of a metal foil with a carrier having a first carrier, a first release layer, and the first metal foil in this order, and the second layer After the formation of the laminate and before the laser processing of the first metal foil, the first carrier is peeled from the second laminate, and/or The third metal foil is provided in the form of a metal foil with a carrier having a third carrier, a third release layer, and the third metal foil in this order. After the second laminate is formed, the third metal foil Before the laser processing, the third carrier is peeled from the second laminate.

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