Method for manufacturing printed wiring board

Abstract

Provided is a method for manufacturing a printed wiring board, whereby a metal carrier can be easily separated and recovered from an unwanted support substrate. The method for manufacturing a printed wiring board includes: a step for preparing a support substrate including a metal foil with a carrier provided with a first metal foil, a first release layer, a metal carrier, a second release layer, and a second metal foil in this order, and a resin base material provided on a first metal foil side of the metal foil with a carrier, the support substrate including the first metal foil, the first release layer, the metal carrier, the second release layer, and the second metal foil; the peeling strength of the second peeling layer is greater than that of the first peeling layer; a step for forming a stacked wiring layer on the second metal foil of the support substrate to produce a support substrate with the stacked wiring layer; a step for separating the first metal foil and the resin base material from the support substrate with the stacked wiring layer via a first peeling layer to obtain a stacked wiring layer with a carrier, the stacked wiring layer including the stacked wiring layer, a second metal foil, a second peeling layer, and a metal carrier; and a step for separating and recovering the metal carrier from the stacked wiring layer with the carrier via the second peeling layer.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing printed wiring boards. Background Technology

[0002] In recent years, multilayer printed circuit boards (PCBs) have been widely adopted to increase mounting density and achieve miniaturization. These multilayer PCBs are mostly used in portable electronic devices for the purpose of weight reduction and miniaturization. Furthermore, there are demands for further reductions in the thickness of interlayer insulation layers, as well as further thinning and weight reduction of the PCB itself.

[0003] To meet these requirements, a manufacturing method for multilayer printed circuit boards (PCBs) using a coreless stacking method is employed. Coreless stacking refers to a method of creating multiple layers by alternately layering insulating layers and wiring layers without using a so-called core substrate. In coreless stacking, to facilitate easy separation of the support substrate from the multilayer PCB, a carrier-bearing metal foil is used, which sequentially comprises a carrier, a release layer, and a metal foil (e.g., copper foil). Specifically, the carrier side of the carrier-bearing metal foil is adhered to a resin substrate to form a support substrate serving as a dummy core. After alternately stacking insulating layers and wiring layers on the metal foil to obtain a stacked wiring layer, the stacked wiring layer is separated from the support substrate at the release layer location.

[0004] For example, in Patent Document 1 (WO2019 / 188836), a method for manufacturing a multilayer wiring board is disclosed, in which a carrier side of a metal foil with a carrier is pasted onto a temporary support such as prepreg, an insulating layer and a metal foil are alternately stacked on the metal foil and various processing is performed, and then the temporary support and the carrier are removed from the resulting laminate.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: WO2019 / 188836 Summary of the Invention

[0008] In coreless stacking methods using carrier-supported metal foil, the support substrate comprising the resin substrate and the carrier is peeled off after the stacked wiring layers are formed. Typically, the carrier is made of metal (e.g., copper), so it is suitable if the carrier, which is a valuable metal resource, can be separated from and recycled from the support substrate. However, currently, due to the strong bonding between the resin substrate and the carrier constituting the support substrate, it is difficult to separate them. Support substrates containing metal are discarded as industrial waste or traded cheaply as metal-containing resin materials. Therefore, a method for easily separating and recycling carrier monomers is desired.

[0009] The inventors have obtained the following insight: to prepare a support substrate formed by attaching a metal foil with a carrier having a peel strength of different peel strengths and a metal foil to a resin substrate on both sides of a metal carrier, and to form a stacked wiring layer on the support substrate, thereby enabling the metal carrier to be easily separated and recycled from the unwanted support substrate.

[0010] Therefore, the object of the present invention is to provide a method for manufacturing a printed wiring board that allows for easy separation and recycling of the metal carrier from an unwanted support substrate.

[0011] According to this disclosure, the following methods are provided.

[0012] [Method 1]

[0013] A method for manufacturing a printed wiring board includes the following steps:

[0014] The process of preparing a support substrate includes a metal foil with a carrier and a resin substrate disposed on the first metal foil side of the metal foil with the carrier. The metal foil with the carrier sequentially includes a first metal foil, a first release layer, a metal carrier, a second release layer and a second metal foil. The release strength of the second release layer is greater than the release strength of the first release layer.

[0015] The process of forming a stacked wiring layer on the second metal foil of the support substrate to manufacture a support substrate with a stacked wiring layer;

[0016] The process of separating the first metal foil and the resin substrate from the support substrate with the stacked wiring layer via the first release layer to obtain a stacked wiring layer with a carrier comprising the stacked wiring layer, the second metal foil, the second release layer, and the metal carrier; and

[0017] The process of separating and recovering the metal carrier from the stacked wiring layer with the carrier via the second stripping layer.

[0018] [Method 2]

[0019] According to the method for manufacturing a printed wiring board as described in Method 1, the thickness of the metal carrier is greater than the thickness of each of the first metal foil and the second metal foil.

[0020] [Method 3]

[0021] According to the manufacturing method of printed wiring board according to method 1 or 2, the thickness of the second metal foil is greater than or equal to the thickness of the first metal foil.

[0022] [Method 4]

[0023] The method for manufacturing a printed wiring board according to any one of methods 1 to 3, wherein the peel strength of the second peeling layer is more than 1.1 times and less than 50 times the peel strength of the first peeling layer.

[0024] [Method 5]

[0025] The method for manufacturing a printed wiring board according to any one of methods 1 to 4, wherein the first release layer has a peel strength of 1 gf / cm or more and 50 gf / cm or less.

[0026] [Method 6]

[0027] The method for manufacturing a printed wiring board according to any one of methods 1 to 5, wherein the second release layer has a peel strength of 2 gf / cm or more and 100 gf / cm or less.

[0028] [Method 7]

[0029] The method for manufacturing a printed wiring board according to any one of methods 1 to 6, wherein the difference between the peel strength of the second peeling layer and the peel strength of the first peeling layer is more than 1 gf / cm and less than 50 gf / cm.

[0030] [Method 8]

[0031] The method for manufacturing a printed wiring board according to any one of methods 1 to 7, wherein the adhesion strength between the first metal foil and the resin substrate is greater than the peel strength of the second release layer.

[0032] [Method 9]

[0033] The method for manufacturing a printed wiring board according to any one of methods 1 to 8, wherein the metal carrier is copper foil.

[0034] [Method 10]

[0035] The method for manufacturing a printed wiring board according to any one of methods 1 to 9, wherein the first metal foil and the second metal foil are both copper foils. Attached Figure Description

[0036] Figure 1 This is a process flow diagram illustrating an example of the manufacturing method of the present invention.

[0037] Figure 2 This is a process flow diagram illustrating an example of a method for forming stacked wiring layers.

[0038] Figure 3 It means to express the understanding of the classics. Figure 2 The flowchart illustrates an example of an additional processing method for the stacked wiring layer obtained through the shown process.

[0039] Figure 4 This is a process flow diagram illustrating another example of a method for forming stacked wiring layers.

[0040] Figure 5 It means to express the understanding of the classics. Figure 4 The flowchart illustrates an example of an additional processing method for the stacked wiring layer obtained through the shown process. Detailed Implementation

[0041] Manufacturing method of printed wiring board

[0042] This invention relates to a method for manufacturing printed wiring boards. The method of this invention includes the following steps: (1) preparation of a support substrate, (2) formation of stacked wiring layers, (3) separation of unwanted substrates, and (4) separation and recycling of a metal carrier. Hereinafter, each step will be described with reference to the accompanying drawings.

[0043] (1) Preparation of the support substrate

[0044] First, such as Figure 1 As shown in (i), a support substrate 10 comprising a carrier-bearing metal foil 12 and a resin substrate 24 is prepared. The carrier-bearing metal foil 12 sequentially comprises a first metal foil 20, a first release layer 16, a metal carrier 14, a second release layer 18, and a second metal foil 22. The release strength of the second release layer 18 is greater than the release strength of the first release layer 16. The resin substrate 24 is disposed on the first metal foil 20 side of the carrier-bearing metal foil 12. When the stacked wiring layer 28 (described later) is formed on both sides of the support substrate 10, as shown, it is preferable to provide the carrier-bearing metal foil 12 on both sides of the resin substrate 24. On the other hand, when the stacked wiring layer 28 is formed on one side of the support substrate 10, the carrier-bearing metal foil 12 can be provided only on one side of the resin substrate 24.

[0045] The metal carrier 14 is a foil or layer made of metal used to support the first metal foil 20 and the second metal foil 22 to improve their operability. Preferred examples of the metal carrier 14 include aluminum foil, copper foil, stainless steel foil, nickel foil, and combinations thereof, with copper foil being more preferred. The thickness of the metal carrier 14 is typically 6 μm or more and 200 μm or less, preferably 9 μm or more and 70 μm or less, and more preferably 12 μm or more and 35 μm or less. The thickness of the metal carrier 14 is typically greater than the thickness of each of the first metal foil 20 and the second metal foil 22. The metal carrier 14 can be separated in the process described later, and therefore, by satisfying such a thickness relationship, metal resources can be recovered more efficiently. From this viewpoint, the thickness of the metal carrier 14 is preferably 1.2 times or more and 200 times or less of the thickness of the first metal foil 20, more preferably 1.5 times or more and 100 times or less, and even more preferably 2.0 times or more and 30 times or less.

[0046] The first release layer 16 and the second release layer 18 are layers that respectively function to: weaken the release strength of the metal carrier 14, ensure the stability of this strength, and thereby suppress the interdiffusion that may occur between the metal carrier 14 and the first metal foil 20 or the second metal foil 22 during high-temperature pressing. The first release layer 16 and the second release layer 18 can be either organic release layers or inorganic release layers. Examples of organic components used in organic release layers include nitrogen-containing organic compounds, sulfur-containing organic compounds, and carboxylic acids. Examples of nitrogen-containing organic compounds include triazole compounds and imidazole compounds, among which triazole compounds are preferred in terms of easy and stable release properties. Examples of triazole compounds include 1,2,3-benzotriazole, carboxybenzotriazole, N',N'-bis(benzotriazolylmethyl)urea, 1H-1,2,4-triazole, and 3-amino-1H-1,2,4-triazole. Examples of sulfur-containing organic compounds include mercaptobenzothiazole, trithiocyanate, and 2-benzimidazole thiol. Examples of carboxylic acids include monocarboxylic acids and dicarboxylic acids. On the other hand, examples of inorganic components used in the inorganic release layer include Ni, Mo, Co, Cr, Fe, Ti, W, P, Zn, and chromate-treated films. The thicknesses of the first release layer 16 and the second release layer 18 are typically 1 nm or more and 1 μm or less, preferably 5 nm or more and 500 nm or less.

[0047] As described above, the peel strength of the second release layer 18 is greater than that of the first release layer 16. Specifically, the peel strength of the second release layer 18 is preferably 1.1 times or more and 50 times or less than that of the first release layer 16, more preferably 1.2 times or more and 30 times or less, even more preferably 1.3 times or more and 20 times or less, and particularly preferably 1.5 times or more and 5.0 times or less. Therefore, in the processes described later, the first metal foil 20 and the resin substrate 24 can be further and stably separated from the support substrate 26 with the stacked wiring layer at the location of the first release layer 16. In this specification, the first metal foil 20 and the resin substrate 24, separated after the formation of the stacked wiring layer 28, are sometimes collectively referred to as "unused substrate".

[0048] The first release layer 16 preferably has a peel strength of 1 gf / cm or more and 50 gf / cm or less, more preferably 3 gf / cm or more and 50 gf / cm or less, even more preferably 5 gf / cm or more and 30 gf / cm or less, and particularly preferably 10 gf / cm or more and 20 gf / cm or less. This effectively prevents accidental peeling between the metal carrier 14 and the first metal foil 20 during the formation of the stacked wiring layer 28 (described later), and allows for smoother separation of the substrate after the formation of the stacked wiring layer 28. It should be noted that the peel strength of the first release layer 16 in this specification refers to the measured value when the metal carrier 14 and the first metal foil 20 are peeled off via the first release layer 16, according to JIS C 6481-1996, on a support substrate 10 comprising a resin substrate 24 disposed on the side of the first metal foil 20 with a carrier metal foil 12.

[0049] The second release layer 18 preferably has a peel strength of 2 gf / cm or more and 100 gf / cm or less, more preferably 5 gf / cm or more and 70 gf / cm or less, even more preferably 7 gf / cm or more and 50 gf / cm or less, and particularly preferably 20 gf / cm or more and 30 gf / cm or less. Therefore, in the processes described later, the adhesion between the metal carrier 14 and the second metal foil 22 can be ensured until the substrate is separated from the support substrate 26 with the stacked wiring layer, and the subsequent separation of the metal carrier 14 from the stacked wiring layer 40 with the carrier can be performed more smoothly. It should be noted that the peel strength of the second release layer 18 in this specification refers to the measured value when the metal carrier 14 is peeled from the second metal foil 22 via the second release layer 18, under the same conditions as the fabrication of the support substrate 10 (e.g., the thermal history and pressure during pressing).

[0050] The difference between the peel strength of the second release layer 18 and the peel strength of the first release layer 16 (=(peel strength of the second release layer 18) - (peel strength of the first release layer 16)) is preferably 1 gf / cm or more and 50 gf / cm or less, more preferably 3 gf / cm or more and 30 gf / cm or less, even more preferably 5 gf / cm or more and 20 gf / cm or less, and particularly preferably 7 gf / cm or more and 20 gf / cm or less. Therefore, in the process described later, the unwanted substrate can be further and stably separated from the support substrate 26 with the stacked wiring layers at the location of the first release layer 16.

[0051] As long as the peel strength of the second release layer 18 is greater than the peel strength of the first release layer 16, the first release layer 16 and the second release layer 18 can be made of different materials or of the same material. However, from the viewpoint of efficiently manufacturing the carrier-supported metal foil 12, it is preferable that the first release layer 16 and the second release layer 18 are made of the same material. Even if the first release layer 16 and the second release layer 18 are made of the same material, by making their thicknesses different, the peel strengths of the first release layer 16 and the second release layer 18 can be controlled to the desired values ​​and relationships described above. That is, it is preferable that the thickness of the second release layer 18 is less than the thickness of the first release layer 16, thereby enabling the peel strength of the second release layer 18 to be controlled to be greater than that of the first release layer 16. For example, in the case of forming the organic release layer described above, for the metal carrier 14, a liquid with a high concentration of the release layer component is brought into contact with the side forming the thicker release layer (i.e., the side forming the first release layer 16) by spraying or the like, while a liquid with a low concentration of the release layer component is brought into contact with the side forming the thinner release layer (i.e., the side forming the second release layer 18). In this way, by fixing the release layer component in the solution containing the release layer component to the surface of the metal carrier 14, a first release layer 16 and a second release layer 18 with different thicknesses (i.e., different release strengths) can be formed. On the other hand, in the case of forming the inorganic release layer described above, relative to the metal carrier 14, the processing current is controlled to be higher on one side, thereby causing the release layer component to be electrodeposited thicker to form the first release layer 16, and the processing current is controlled to be lower on the other side, thereby causing the release layer component to be electrodeposited thinner to form the second release layer 18.

[0052] The first metal foil 20 adheres closely to the resin substrate 24, which helps to fix the carrier-bearing metal foil 12 onto the resin substrate 24 and facilitates the separation of the metal carrier 14 from the unwanted substrate in subsequent processes. Therefore, the first metal foil 20 preferably maintains adhesion to the resin substrate 24 until the metal carrier 14 is separated from the unwanted substrate. Specifically, the adhesion strength between the first metal foil 20 and the resin substrate 24 is preferably greater than the peel strength of the second release layer 18. More specifically, the adhesion strength between the first metal foil 20 and the resin substrate 24 is preferably 5 times or more, more preferably 10 times or more, than the peel strength of the second release layer 18. A higher adhesion strength between the first metal foil 20 and the resin substrate 24 is preferred, typically 2000 times or less than the peel strength of the second release layer 18. Here, the adhesion strength between the first metal foil 20 and the resin substrate 24 refers to the measured value when the first metal foil 20 is peeled from the resin substrate 24 according to JIS C 6481-1996.

[0053] The second metal foil 22 is used in the formation of the stacked wiring layer 28, which will be described later. The second metal foil 22 may form part of the stacked wiring layer 28. A preferred method for forming the stacked wiring layer 28 using the second metal foil 22 will be described later. The second metal foil 22 may be a known structure used in wiring layer metal foils in coreless stacking, and is not particularly limited.

[0054] The first metal foil 20 and the second metal foil 22 can be formed by wet film-forming methods such as electroless plating and electrolytic plating, dry film-forming methods such as sputtering and chemical vapor deposition, or combinations thereof. Examples of the first metal foil 20 and the second metal foil 22 include aluminum foil, copper foil, stainless steel foil, nickel foil, etc., with copper foil being preferred. Particularly preferred is that both the first metal foil 20 and the second metal foil 22 are copper foils.

[0055] The thickness of the second metal foil 22 is preferably greater than or equal to the thickness of the first metal foil 20. Specifically, the thickness of the second metal foil 22 is preferably 1.0 times or more the thickness of the first metal foil 20, more preferably 1.1 times or more and 25 times or less, and even more preferably 1.5 times or more and 10 times or less. This reduces the amount of potentially wasted metal resources (i.e., the first metal foil 20 bonded to the resin substrate 24) and facilitates the formation of the desired wiring layer using the second metal foil 22. For example, the first metal foil 20 preferably has a thickness of 0.1 μm or more and 5.0 μm or less, more preferably 0.2 μm or more and 3.0 μm or less, and even more preferably 0.5 μm or more and 1.5 μm or less. Similarly, the second metal foil 22 preferably has a thickness of 0.5 μm or more and 10.0 μm or less, more preferably 1.0 μm or more and 5.0 μm or less, and even more preferably 1.5 μm or more and 5.0 μm or less.

[0056] The carrier-supported metal foil 12 may have other functional layers between the first release layer 16 and the metal carrier 14 and / or the first metal foil 20, and between the second release layer 18 and the metal carrier 14 and / or the second metal foil 22. An auxiliary metal layer is an example of such a functional layer. The auxiliary metal layer is preferably composed of nickel and / or cobalt. By forming such an auxiliary metal layer, interdiffusion that may occur between the metal carrier 14 and the first metal foil 20 or the second metal foil 22 during high-temperature or long-term hot pressing can be further suppressed, ensuring the stability of the peel strength of the metal carrier 14. The thickness of the auxiliary metal layer is preferably 0.001 μm or more and 3 μm or less.

[0057] The resin substrate 24 is a layer that helps to impart the desired rigidity to the support substrate 10. The resin substrate 24 can be a known structure used as a support in a coreless stacking method. For example, the resin substrate 24 is preferably a prepreg and / or a resin sheet. Prepreg refers to a general term for composite materials made by impregnating a synthetic resin into a substrate such as a synthetic resin board, glass board, glass fabric, glass nonwoven fabric, or paper. Preferred examples of synthetic resins impregnated in the prepreg include epoxy resin, cyanate ester resin, bismaleimide triazine resin (BT resin), polyphenylene ether resin, and phenolic resin. Examples of resins constituting the resin sheet include epoxy resin, polyimide resin, and polyester resin. In addition, the resin substrate 24 may also contain filler particles composed of various inorganic particles such as silica and alumina. The thickness of the resin substrate 24 is not particularly limited, but is preferably 1 μm or more and 1000 μm or less, more preferably 2 μm or more and 400 μm or less, and even more preferably 3 μm or more and 200 μm or less. The resin substrate 24 may be composed of multiple layers.

[0058] The support substrate 10 can be a pre-finished support substrate that can be used directly, or the first metal foil 20 side of the carrier metal foil 12 can be laminated on one or both sides of the resin substrate 24 to form a laminate (metal-clad laminate). This lamination can be performed according to the known conditions and methods used in the lamination of metal foil and prepreg in the usual printed wiring board manufacturing process.

[0059] (2) Formation of stacked wiring layers

[0060] like Figure 1 As shown in (ii), a stacked wiring layer 28 is formed on the second metal foil 22 of the support substrate 10. Thus, a support substrate 26 with the stacked wiring layer is obtained. The formation of the stacked wiring layer 28 is not particularly limited; it can be performed by alternately stacking the insulating layer 30 and the wiring layer 32 according to a known coreless stacking method. The insulating layer 30 and the wiring layer 32 can be stacked repeatedly until the desired number of stacked wiring layers 28 are formed.

[0061] Figure 2 An example of a preferred method for forming the stacked wiring layer 28 is shown. In this example, firstly, an insulating layer 30 and a metal layer 34 are sequentially stacked on the second metal foil 22 of the support substrate 10. Figure 2(i)). The insulating layer 30 can preferably be formed by laminating the aforementioned prepreg, resin sheet, or other insulating resin material onto the second metal foil 22 and then performing hot pressing. The metal layer 34 can be formed by wet film formation methods such as electroless plating and electrolytic plating, dry film formation methods such as sputtering and chemical vapor deposition, or combinations thereof. Examples of the metal layer 34 include aluminum foil, copper foil, stainless steel foil, nickel foil, etc., with copper foil being preferred. The metal layer 34 can also be supplied in the form of a metal foil with a carrier, or the metal layer 34 can be formed by laminating the metal foil with the carrier onto the insulating layer 30 and then peeling off the carrier.

[0062] Next, circuitry is formed on the stacked metal layer 34 using known methods such as subtraction, thereby forming the wiring layer 32. Figure 2 (ii)). As an example of circuit formation based on subtractive processing, a dry film is adhered to the surface of the metal layer 34, and exposed and developed in a predetermined pattern to form a resist layer (not shown). Next, an etchant capable of dissolving the metal constituting the metal layer 34 is used to remove the metal exposed between the resist layers, thereby peeling off the resist layer to form a wiring layer 32. Then, an insulating layer 30 and a metal layer 34 are further stacked on the support substrate 10 on which the insulating layer 30 and the wiring layer 32 are formed to obtain a support substrate 26 with stacked wiring layers. Figure 2 (iii)). Furthermore, as described later, it is preferable that after separating the unwanted substrate and metal carrier 14 from the support substrate 26 with the stacked wiring layer, various processes such as forming vias and plating are performed on both sides of the stacked wiring layer 28, thereby processing the second metal foil 22 and the metal layer 34 into a wiring layer (see (iii)). Figure 3 ).

[0063] in addition, Figure 4 Another example of a preferred method for forming the stacked wiring layer 28 is shown. In this example, firstly, a wiring pattern 36 is formed on the second metal foil 22 of the support substrate 10. Figure 4 (i) and (ii)). The formation of the wiring pattern 36 can be performed according to known methods for manufacturing printed wiring boards, and is not particularly limited. Preferably, the wiring pattern 36 can be formed by (i) forming a photoresist layer pattern on the second metal foil 22, (ii) forming electroplated copper (pattern plating), and (iii) peeling off the photoresist layer pattern. Then, in addition to the wiring pattern 36 formed on the second metal foil 22 as the first wiring layer, an insulating layer 30 and a wiring pattern 36 as the second wiring layer are formed sequentially to obtain a stacked wiring layer 28. For example, the insulating layer 30 and the metal layer 34 can also be stacked. Figure 4(iii) Laser processing is performed on the metal layer 34 and the insulating layer 30 directly beneath it using a carbon dioxide laser or similar method. Next, patterning can be performed through chemical copper plating, photoresist coating processing, electrolytic copper plating, photoresist removal, etc. (further rapid etching may be performed as needed) to form a wiring pattern 36 as the second wiring layer. Figure 4 (iv) The patterning and arbitrary fast etching are repeated as needed to form up to the nth wiring layer (n is an integer greater than 2).

[0064] (3) No substrate separation process required

[0065] like Figure 1 As shown in (iii), the first metal foil 20 and the resin substrate 24 (i.e., the unwanted substrate) are separated from the support substrate 26 with the stacked wiring layer via the first release layer 16. This results in a stacked wiring layer 40 with a carrier, comprising the stacked wiring layer 28, the second metal foil 22, the second release layer 18, and the metal carrier 14. Since the peel strength of the second release layer 18 is greater than that of the first release layer 16, the peeling between the metal carrier 14 and the first metal foil 20 occurs preferentially compared to the peeling between the metal carrier 14 and the second metal foil 22. As a result, the stacked wiring layer 40 with the carrier and the unwanted substrate can be stably separated. Furthermore, since the metal carrier 14 functions as a protective layer for the stacked wiring layer 28, oxidation and degradation of the wiring layer and the like can be effectively prevented.

[0066] As described above, in conventional coreless stacking methods, the carrier and resin substrate are firmly bonded together, making it difficult to separate and recycle the carrier monomers. On the other hand, in this invention, a first release layer 16 and a first metal foil 20 are provided between the metal carrier 14 and the resin substrate 24, ensuring a tight bond between the first metal foil 20 and the resin substrate 24. Therefore, the metal carrier 14 can be separated from the resin substrate 24 and recycled. Typically, the thickness of the metal carrier 14 is greater than the thickness of the first metal foil 20, enabling efficient recycling of metal resources.

[0067] It should be noted that when the metal carrier and resin substrate are directly bonded without the first metal foil 20 via an organic layer (e.g., a release resin layer or an organic anti-rust layer), controlling the peel strength becomes difficult depending on the material of the resin substrate. Therefore, it is difficult to prevent accidental peeling between the metal carrier and resin substrate during the formation of the stacked wiring layer, and it is difficult to smoothly separate the metal carrier from the resin substrate after the stacked wiring layer is formed. In contrast, according to the present invention, the first metal foil 20 is bonded to the resin substrate 24, and the peel strength between the metal carrier 14 and the first metal foil 20 can be controlled within a desired range using the first release layer 16. Therefore, the stacked wiring layer 40 with the carrier and the substrate can be smoothly separated, and the metal carrier 14 can be easily separated and recovered in the processes described later.

[0068] (4) Separation and recovery of metal carriers

[0069] like Figure 1 As shown in (iv), the metal carrier 14 is separated from the carrier-supported stacked wiring layer 40 via the second release layer 18. In this way, the metal carrier 14 monomers separated from the stacked wiring layer 28, resin substrate 24, etc. can be recovered.

[0070] The stacked wiring layer 28 after separating the metal carrier 14 can be used directly as a printed wiring board, but it is preferable to process it into a printed wiring board by appropriately adding known processes. Here, Figure 3 It shows the effect of Figure 2 An example of an additional processing method for the stacked wiring layer obtained by the process shown. In this example, vias 42 reaching the wiring layer 32 are formed by performing laser processing on both sides (second metal foil 22 and metal layer 34) of the stacked wiring layer 28 after separating the metal carrier 14. Figure 3 (i) and (ii)). Then, after performing cleaning and other processes as optional steps, plating and patterning are performed on both sides of the stacked wiring layer 28 to form an electrical connection via the via 42 and the wiring layer 32, forming an electroplated layer 44. Figure 3 (iii)). Thus, a stacked wiring layer with wiring patterns on both sides is obtained. In addition, as described later, a solder mask layer, mounting bumps such as pillars can also be formed on the outer layer as needed.

[0071] As another example, Figure 5 The text shows the process of... Figure 4 The illustrated process describes an additional processing method for the stacked wiring layer obtained. In this example, rapid etching is performed on the stacked wiring layer 28 after the metal carrier 14 has been separated to remove the second metal foil 22 and the metal layer 34. Figure 5(i) and (ii)). Thus, the second metal foil 22 exposed between the wiring patterns 36 of the first wiring layer and the metal layer 34 exposed between the wiring patterns 36 of the nth wiring layer are removed by rapid etching, resulting in the prescribed wiring pattern 36. That is, the wiring pattern 36 of the first wiring layer is buried in the insulating layer 30, becoming a state where only the surface is exposed. In this way, a stacked wiring layer with wiring pattern 36 as an embedded circuit is obtained. Then, the stacked wiring layer 28, where the second metal foil 22, etc., has been removed, is covered with a solder mask layer 46. Figure 5 (iii)). The preferred solder resist layer 46 is a photo-etched solder resist layer. Furthermore, various outer layer processing can be performed. For example, Ni-Au plating, Ni-Pd-Au plating, water-soluble flux treatment, etc., can be performed as surface treatments for the outer layer pads. Additionally, columnar supports, etc., can be provided on the outer layer pads.

Claims

1. A method for manufacturing a printed wiring board, wherein, The manufacturing method of this printed wiring board includes the following steps: The process of preparing a support substrate includes a metal foil with a carrier and a resin substrate disposed on the first metal foil side of the metal foil with the carrier. The metal foil with the carrier sequentially includes a first metal foil, a first release layer, a metal carrier, a second release layer and a second metal foil. The release strength of the second release layer is greater than the release strength of the first release layer. The process of forming a stacked wiring layer on the second metal foil of the support substrate to manufacture a support substrate with a stacked wiring layer; The process of separating the first metal foil and the resin substrate from the support substrate with the stacked wiring layer via the first release layer to obtain a stacked wiring layer with a carrier comprising the stacked wiring layer, the second metal foil, the second release layer, and the metal carrier; and The process of separating and recovering the metal carrier from the stacked wiring layer with the carrier via the second stripping layer.

2. The method for manufacturing a printed wiring board according to claim 1, wherein, The thickness of the metal carrier is greater than the thickness of both the first metal foil and the second metal foil.

3. The method for manufacturing a printed wiring board according to claim 1 or 2, wherein, The thickness of the second metal foil is greater than or equal to the thickness of the first metal foil.

4. The method for manufacturing a printed wiring board according to claim 1 or 2, wherein, The peel strength of the second peeling layer is more than 1.1 times and less than 50 times the peel strength of the first peeling layer.

5. The method for manufacturing a printed wiring board according to claim 1 or 2, wherein, The first release layer has a peel strength of more than 1 gf / cm and less than 50 gf / cm.

6. The method for manufacturing a printed wiring board according to claim 1 or 2, wherein, The second release layer has a peel strength of more than 2 gf / cm and less than 100 gf / cm.

7. The method for manufacturing a printed wiring board according to claim 1 or 2, wherein, The difference between the peel strength of the second peeling layer and the peel strength of the first peeling layer is greater than 1 gf / cm and less than 50 gf / cm.

8. The method for manufacturing a printed wiring board according to claim 1 or 2, wherein, The adhesion strength between the first metal foil and the resin substrate is greater than the peel strength of the second release layer.

9. The method for manufacturing a printed wiring board according to claim 1 or 2, wherein, The metal carrier is copper foil.

10. The method for manufacturing a printed wiring board according to claim 1 or 2, wherein, Both the first metal foil and the second metal foil are copper foils.

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