JP2007194265A - Flexible printed wiring board, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible printed wiring board which is superior in adhesion property of a resin substrate and metal wiring. <P>SOLUTION: The printed wiring board has the resin substrate having a fine concave and convex surface, a base layer formed on the fine concave and convex surface, a seed layer formed on the base layer in a pattern shape and a wiring plating layer formed on the seed layer. The base layer comprises a metal for adhesion property improvement. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flexible printed wiring board having excellent adhesion between a resin substrate and a metal wiring, and a method for manufacturing the same.

  Flexible printed wiring boards are metal wiring on a thin bendable resin substrate, helping to save mounting space and improving reliability, and are widely used in computer-related equipment, audio products, communication equipment, etc. .

  Currently, a subtractive method and a semi-additive method are known as a general method for manufacturing a flexible printed wiring board. In the subtractive method, a laminate including a resin substrate and a metal foil is prepared, a mask pattern similar to the pattern of the metal wiring is formed on the metal foil, and then the unmasked portion of the metal foil is removed. Finally, the metal pattern is obtained on the resin substrate by removing the mask pattern. The subtractive method has an advantage that it is a simple method, but has a drawback that it is difficult to miniaturize the metal wiring.

  On the other hand, in the semi-additive method, a seed layer is formed on a resin substrate by an electroless plating method, a resist pattern is formed in a region on the seed layer where a metal wiring pattern is not formed, and then an electrolytic plating method is formed in the gap of the resist pattern. In this method, the metal wiring is formed on the resin substrate by forming the metal wiring and finally removing the resist pattern and the unnecessary seed layer. The semi-additive method has an advantage that the metal wiring can be miniaturized, but has a disadvantage that the adhesion between the resin substrate and the metal wiring is inferior. Therefore, improvement in adhesion has been demanded.

  For example, it is possible to improve the adhesion by using an adhesive layer between the resin substrate and the metal wiring, but the heat resistance, flexibility, migration resistance, bonding property, etc. are poor. was there.

  Regarding the adhesion improvement in the semi-additive method, for example, in Patent Document 1, a material made of a thermoplastic polyimide resin, which has an adhesive strength of 5 N / cm or more when an electroless plating film is formed on the surface thereof A thermoplastic polyimide resin material characterized by being treated is disclosed. However, there are cases where sufficient adhesion cannot be obtained.

  Patent Document 2 discloses a method for manufacturing a printed wiring board having a step of heat-treating an insulating layer and an electroless plating layer. By performing the heat treatment, adhesion between the resin substrate and the metal wiring is achieved, but there are cases where sufficient adhesion cannot be obtained.

  Further, for example, by using a sputtering method, it is possible to form a metal wiring layer on a resin substrate with good adhesion, but since the sputtering method uses a vacuum process, there is a disadvantage that the cost is high and the productivity is inferior. there were.

JP 2004-189981 A JP-A-2005-135985

  This invention is made | formed in view of the said situation, and it aims at providing the flexible printed wiring board excellent in the adhesiveness of a resin substrate and metal wiring.

  In order to solve the above problems, in the present invention, a resin substrate having a fine uneven surface, an underlayer formed on the fine uneven surface, a seed layer formed in a pattern on the underlayer, And a wiring plating layer formed on the seed layer, wherein the underlayer contains a metal for improving adhesion.

  According to the present invention, a flexible printed wiring board having excellent adhesion between the resin substrate and the metal wiring is formed by forming the base layer containing the adhesion improving metal between the resin substrate and the seed layer. be able to.

  Moreover, in the said invention, it is preferable that the said base layer contains at least 1 type of metal selected from the group which consists of Ni, Co, Cu, Mo, and Fe as said metal for adhesiveness improvement. This is because a flexible printed wiring board excellent in adhesion can be obtained.

  Moreover, in the said invention, it is preferable that the said base layer contains the metal for heat processing. This is because a flexible printed wiring board having excellent durability can be obtained.

  Moreover, in the said invention, it is preferable that the surface roughness Rz of the said fine uneven | corrugated surface exists in the range of 0.1 micrometer-5.0 micrometers. This is because if the surface roughness Rz is within the above range, a flexible printed wiring board having excellent adhesion can be obtained.

  Moreover, in the said invention, it is preferable that the line | wire width of the said wiring plating layer exists in the range of 3 micrometers-30 micrometers. This is because a flexible printed wiring board having a high wiring density can be obtained if the line width of the wiring plating layer is within the above range.

  Further, in the present invention, using the forming metal foil provided with a supporting metal foil having a fine uneven surface and an underlayer containing the metal for improving adhesion formed on the fine uneven surface, Laminate forming step of forming a laminate by providing a resin substrate on the base layer of the mold metal foil, and a resin with the base layer forming the resin substrate with the base layer by removing the support metal foil from the laminate A substrate formation step, a seed layer formation step of forming a seed layer on the underlayer of the resin substrate with the underlayer by an electroless plating method, a resist pattern formation step of forming a resist pattern on the seed layer, and the resist A wiring plating layer forming step for forming a wiring plating layer in the pattern gap by an electrolytic plating method, and an adhesion between the seed layer and the wiring plating layer is improved after the wiring plating layer forming step. And a resist pattern removing step for removing the resist pattern after the heating step, and a flash etching step for etching the seed layer other than the metal wiring formation region after the resist pattern removing step. A method for producing a flexible printed wiring board is provided.

  According to the present invention, a flexible printed wiring board having excellent adhesion between the underlayer and the seed layer is obtained by forming the seed layer after forming the resin substrate with the underlayer containing the adhesion improving metal. be able to. As a result, the adhesiveness between the resin substrate and the metal wiring can be excellent.

  Further, in the present invention, using the metal foil for shaping provided with a supporting metal foil having a fine uneven surface and an underlayer containing the metal for improving adhesion formed on the fine uneven surface, A laminated body forming step of forming a laminated body by providing a resin substrate on the base layer of the mold metal foil; a seed layer forming step of forming a seed layer by etching the supporting metal foil of the laminated body; A resist pattern forming step for forming a resist pattern on the seed layer; a wiring plating layer forming step for forming a wiring plating layer in the gap between the resist patterns by an electrolytic plating method; and the seed after the wiring plating layer forming step. A heating step for improving adhesion between the layer and the wiring plating layer, a resist pattern removing step for removing the resist pattern after the heating step, After strike pattern removal step, to provide a method of manufacturing a flexible printed wiring board characterized by having a flash etching process for etching the seed layer other than the metal wiring formation region.

  ADVANTAGE OF THE INVENTION According to this invention, the flexible printed wiring board excellent in adhesiveness can be obtained more simply by utilizing the support metal foil of the shaping metal foil as a seed layer.

  In this invention, there exists an effect that the flexible printed wiring board excellent in the adhesiveness of a resin substrate and metal wiring can be provided. In particular, even when the metal wiring is miniaturized, it is possible to provide a flexible printed wiring board having excellent adhesion between the resin substrate and the metal wiring and having the metal wiring formed with high accuracy.

  Hereinafter, the flexible printed wiring board of this invention and the manufacturing method of a flexible printed wiring board are demonstrated in detail.

A. First, the flexible printed wiring board of the present invention will be described. The flexible printed wiring board of the present invention includes a resin substrate having a fine uneven surface, an underlayer formed on the fine uneven surface, a seed layer formed in a pattern on the underlayer, and the seed layer And the undercoat layer contains a metal for improving adhesion.

  According to the present invention, a flexible printed wiring board having excellent adhesion between the resin substrate and the metal wiring is formed by forming the base layer containing the adhesion improving metal between the resin substrate and the seed layer. be able to. In addition, by providing the above base layer, even when a low-roughness resin substrate is used, the adhesion between the resin substrate and the metal wiring can be improved, and a fine metal wiring can be formed. It can be formed with high accuracy. Furthermore, by providing the base layer, a flexible printed wiring board having excellent adhesion even under high temperature and high humidity conditions can be obtained. In addition, since the flexible printed wiring board of this invention is normally formed by a semi-additive method so that it may mention later, a seed layer becomes an essential component. Therefore, for example, a flexible printed wiring board formed by a subtractive method does not have a seed layer, and thus is different from the flexible printed wiring board of the present invention.

Next, the flexible printed wiring board of this invention is demonstrated using drawing. FIG. 1 is a schematic sectional view showing an example of the flexible printed wiring board of the present invention. As shown in FIG. 1, the flexible printed wiring board of the present invention was formed on a resin substrate 1 having a fine uneven surface, an underlayer 2 formed in a pattern on the fine uneven surface, and an underlayer 2. It has a seed layer 3 and a wiring plating layer 4 formed on the seed layer 3. Further, the underlayer 2 contains an adhesion improving metal that improves the adhesion with the seed layer. In the present invention, the “metal wiring” refers to the seed layer 3 and the wiring plating layer 4.
Hereinafter, the flexible printed wiring board of this invention is demonstrated for every structure.

1. Underlayer First, the underlayer used in the present invention will be described. The foundation layer used in the present invention is a layer formed between the resin substrate and the seed layer. Further, the underlayer contains an adhesion improving metal that improves adhesion with the seed layer. The underlayer may be a sparse underlayer or a dense underlayer as long as it contains a metal for improving adhesion.

  First, a sparse underlayer will be described. FIG. 2 is a schematic cross-sectional view showing an example of a sparse underlayer. As shown in FIG. 2, the flexible printed wiring board of the present invention includes a resin substrate 1, a sparse underlayer 2 interspersed with metal particles of an adhesion improving metal such as Ni and Co, a seed layer 3, And a wiring plating layer 4. FIG. 3 is a SEM (scanning electron microscope) photograph showing an example of the surface of the resin substrate (polyimide resin) on which the base layer is formed.

  The metal for improving adhesion is not particularly limited as long as it can improve the adhesion with the seed layer. Among them, in the present invention, the underlayer contains at least one metal selected from the group consisting of Ni, Co, Cu, Mo, Fe, Cr, Zn, Ta, and In as the adhesion improving metal. It is preferable to include at least one metal selected from the group consisting of Ni, Co, Cu, Mo and Fe, and it is more preferable to include at least one of Ni and Co.

  In the present invention, the underlayer preferably contains at least Co as an adhesion improving metal. This is because Co exhibits excellent adhesion with Cu or Ni used for the seed layer.

  Further, the content of the adhesion improving metal contained in the underlayer is not particularly limited, but when elements other than metals are excluded, for example, within the range of 5 atomic% to 40 atomic%, especially 25. It is preferably in the range of atomic% to 35 atomic%. In addition, the said content is calculated | required by measuring using an X-ray photoelectron spectroscopy analyzer.

  Moreover, the said base layer may contain the metal for heat processing other than the metal for an adhesive improvement mentioned above. The heat-resistant metal has a function of preventing the component of the seed layer (for example, a copper component) from moving to the resin substrate side and deteriorating the resin substrate.

  The heat-resistant metal is not particularly limited as long as it can prevent migration of the components of the seed layer. In particular, in the present invention, the underlayer preferably contains at least one metal selected from the group consisting of Zn, Cr, Ta, and In as a heat-resistant treatment metal. It is more preferable to contain at least one. This is because it is possible to efficiently prevent the components of the seed layer from moving to the resin substrate side.

  Further, the content of the heat-resistant metal contained in the underlayer is not particularly limited, but when elements other than the metal are excluded, for example, in the range of 30 atomic% to 80 atomic%, especially 50 atoms. It is preferable to be within the range of% to 70 atomic%. The said content can be calculated | required by the method similar to the case of the metal for an adhesive improvement mentioned above.

  The underlayer may contain Si in addition to the adhesion improving metal described above. For example, by providing a silane coupling treatment layer to be described later, the adhesion between the base layer and the resin substrate can be improved.

  The content of Si contained in the underlayer is not particularly limited, but when elements other than metals are excluded, for example, in the range of 3 atomic% to 30 atomic%, especially 5 atomic% to 10 atomic%. It is preferable to be within the range. The said content can be calculated | required by the method similar to the case of the metal for an adhesive improvement mentioned above.

  Next, a dense underlayer will be described. FIG. 4 is a schematic cross-sectional view illustrating a dense underlayer. As shown in FIG. 4 (a), the flexible printed wiring board of the present invention has an adhesion improving layer 5 (underlayer) composed of resin particles 1 and metal particles of an adhesion improving metal such as Ni and Co. 2), seed layer 3 and wiring plating layer 4 may be included. Further, as shown in FIG. 4B, the base layer 2 may include a heat-resistant treatment layer 6, a silane coupling treatment layer 7, and the like in addition to the adhesion improving layer 5. As will be described later, when the underlayer 2 has conductivity, the underlayer 2 is preferably patterned in the same manner as the seed layer 3 and the wiring plating layer 4.

  In addition, as a formation method of the foundation | substrate layer shown by the said FIG.4 (b), as shown to Fig.5 (a), it forms on the copper foil 8 which has a fine uneven surface, and the said fine uneven surface, Adhesion improvement layer 5 composed of metal particles for adhesion improvement metal such as Ni and Co, heat treatment layer 6 formed on adhesion improvement layer 5, and silane formed on heat treatment layer 6 Using the shaping copper foil 9 provided with the coupling treatment layer 7 and laminating the shaping copper foil 9 and the resin substrate 1 as shown in FIG. A method of forming the underlayer 2 as shown in FIG. 5C by forming and then selectively etching only the copper foil 8 with a ferric chloride aqueous solution or the like can be exemplified.

  The adhesion improving layer contains the above-described adhesion improving metal and has a function of improving the adhesion with the seed layer. Usually, the adhesion improving layer is formed on the surface of the underlayer in contact with the seed layer. Although it does not specifically limit as thickness of the said metal for adhesive improvement, Usually, it exists in the range of 1 nm-10 nm.

  The underlayer may have a heat-resistant treatment layer. The heat-resistant treatment layer contains the heat-treating metal described above, and has a function of preventing the seed substrate component (for example, a copper component) from moving to the resin substrate side and deteriorating the resin substrate. Usually, the heat-resistant treatment layer is disposed between the resin substrate and the adhesion improving metal. Although it does not specifically limit as thickness of the said heat-resistant process layer, Usually, about 1 nm-10 nm.

  The underlayer may have a silane coupling treatment layer. The silane coupling layer has a function of improving the adhesion between the base layer and the resin substrate. Usually, the silane coupling treatment layer is formed on the surface of the base layer in contact with the resin substrate. The thickness of the silane coupling treatment layer is not particularly limited, but is usually about 1 nm to 10 nm.

  Moreover, the ratio of each metal except elements other than the metal contained in the underlayer is not particularly limited, but among them, Cr is within a range of 50% to 80% in terms of atomic%, Co It is preferable to contain 2 to 30% of Ni, 2 to 5% of Ni, and 2 to 15% of Zn.

  Moreover, since the said base layer has the metal for adhesiveness improvement etc. which were mentioned above, it may have electroconductivity. When the said base layer has electroconductivity, it is preferable that it is patterned similarly to the seed layer mentioned later. On the other hand, when the said base layer does not have electroconductivity, you may form in the fine uneven surface whole surface of a resin substrate.

2. Resin Substrate Next, the resin substrate used in the present invention will be described. The resin substrate used in the present invention has a fine uneven surface. The resin substrate is usually excellent in insulation, heat resistance and flexibility.

  The surface roughness Rz of the fine uneven surface is not particularly limited, but is preferably smaller when forming fine metal wiring. This is because if the surface roughness Rz increases, it becomes difficult to form fine metal wirings with high accuracy. Specifically, it is preferably in the range of 0.1 μm to 5.0 μm, more preferably in the range of 0.5 μm to 1.5 μm, and particularly preferably in the range of 0.5 μm to 1.0 μm. This is because if it is less than the above range, a sufficient anchor effect may not be exhibited, and if it exceeds the above range, fine metal wiring may not be formed with high accuracy. The surface roughness Rz is a ten-point average roughness (Rz) defined in JIS B0601. In the present invention, the surface roughness Rz is calculated from a value measured using a laser microscope.

  In the present invention, the fine uneven surface may be formed on at least one surface of the resin substrate, and may be formed on both surfaces of the resin substrate. If the resin substrate has fine uneven surfaces on both sides, a double-sided wiring type flexible printed wiring board can be obtained.

  The thickness of the resin substrate is not particularly limited as long as the insulating properties necessary for the flexible printed wiring board can be exhibited, but it is preferably thin from the viewpoint of flexibility. Specifically, it is preferably in the range of 1 μm to 100 μm, and more preferably in the range of 10 μm to 50 μm. In particular, when the resin substrate has a thermoplastic polyimide on a non-thermoplastic polyimide, the forming process is facilitated. In that case, the thickness of the thermoplastic polyimide resin is specifically preferably in the range of 1 to 10 μm, more preferably in the range of 2 to 5 μm.

The resin substrate is preferably excellent in insulation. This is because if the insulating property is excellent, the thickness of the resin substrate can be reduced and a resin substrate having excellent flexibility can be obtained. The volume resistivity of the resin substrate is not particularly limited. For example, it is preferably 1 × 10 ¹² Ω · cm or more, and more preferably 1 × 10 ¹⁵ Ω · cm or more.

  Moreover, it is preferable that the said resin substrate is excellent in heat resistance. Since the thermocompression bonding is usually performed when the fine uneven surface is formed, it is preferable that the surface has moderate heat resistance with respect to the temperature during the thermocompression bonding. Although it does not specifically limit as glass transition temperature (Tg) of the said resin substrate, For example, it is preferable that it is in the range of 150 degreeC or more, especially 200 to 300 degreeC.

  The resin substrate is preferably excellent in flexibility. This is because excellent flexibility can contribute to improvement in adhesion with the seed layer. In particular, when the resin substrate or a part of the surface layer of the resin substrate is a thermoplastic polyimide, it greatly contributes to improving the adhesion with the seed layer. The storage elastic modulus G ′ of the resin substrate is not particularly limited, but is preferably in the range of 0.1 MPa to 10 MPa, particularly in the range of 1 MPa to 10 MPa, at 300 ° C.

  The material of the resin substrate is not particularly limited as long as it has a moldability capable of forming the fine uneven surface, and examples thereof include a polyimide resin, an epoxy resin, and a liquid crystal polymer. Among them, polyimide resin and epoxy resin are preferable, and polyimide resin is particularly preferable. It is because it can be set as the resin substrate excellent in insulation, heat resistance, and flexibility.

  Furthermore, the polyimide resin may be a thermoplastic polyimide resin or a non-thermoplastic (thermosetting) polyimide resin, but in the present invention, the polyimide resin is a thermoplastic polyimide resin. Is preferred. It is because it is excellent in flexibility.

  The resin substrate may have a single layer structure or a multilayer structure. As a resin substrate having a multilayer structure, for example, one obtained by laminating a thermoplastic polyimide resin on one or both surfaces of a non-thermoplastic polyimide resin can be exemplified. Furthermore, the resin substrate may have a metal layer on one surface. Specific examples include a polyimide resin having a SUS layer on one surface.

3. Next, the seed layer used in the present invention will be described. In the present invention, the seed layer is formed on the above-described underlayer. Since the flexible printed wiring board of the present invention is usually formed using a semi-additive method, as will be described later in the method of manufacturing a flexible printed wiring board, a seed layer is formed on the underlayer, and the A wiring plating layer is formed by electrolytic plating.

Although it does not specifically limit as thickness of the said seed layer, For example, it is preferable to exist in the range of 0.2 micrometer-1.0 micrometer, especially 0.4 micrometer-0.8 micrometer. In particular, when the printed wiring board of the present invention is produced by the manufacturing method of the first aspect described later (method of forming a seed layer by electroless plating method), for example, within the range of 0.2 μm to 1.0 μm, It is preferable to be within the range of 0.4 μm to 0.8 μm.
On the other hand, when the printed wiring board of the present invention is produced by the production method of the second aspect described later (a method of forming a seed layer by etching the supporting metal foil), for example, a range of 0.2 μm to 1.5 μm Among these, it is preferable to be in the range of 0.5 μm to 1.0 μm.

  The metal constituting the seed layer is not particularly limited, and examples thereof include Cu, Ni, Sn, Ag, Au, and the like, among which Cu and Ni are preferable, and Cu is particularly preferable. This is because it is versatile and inexpensive.

4). Wiring plating layer Next, the wiring plating layer used in the present invention will be described. The wiring plating layer used in the present invention is formed on the seed layer described above. The wiring plating layer is usually formed by an electrolytic plating method or the like.

  The thickness of the wiring plating layer is not particularly limited as long as sufficient conductivity can be exhibited. For example, the thickness is in the range of 3 μm to 30 μm, particularly in the range of 5 μm to 20 μm.

  The line width of the wiring plating layer is not particularly limited, but is preferably smaller. This is because if the line width of the wiring plating layer is small, a higher density circuit can be obtained. Specifically, it is in the range of 3 μm to 30 μm, especially in the range of 5 μm to 20 μm.

  Further, the metal constituting the wiring plating layer is not particularly limited as long as it has conductivity, and examples thereof include Cu, Ni, Au, Ag, Cr, Zn, and Pt. Of these, Cu and Ni are preferable, and Cu is particularly preferable. This is because it is versatile and inexpensive.

5). Flexible printed wiring board The flexible printed wiring board of the present invention has at least the resin substrate, the base layer, the seed layer, and the wiring plating layer described above.
The peel strength between the resin substrate and the metal wiring is not particularly limited, but the initial strength is, for example, preferably 10 kN / m or more, and more preferably 15 kN / m or more. The peel strength is a value obtained under the conditions of a peeling direction of 90 °, a peel speed of 50 mm / min, and a pattern width of 3 mm or 10 mm.

  Moreover, the flexible printed wiring board of this invention has an insulating cover layer normally on a wiring plating layer etc. The flexible printed wiring board of the present invention may be a single-sided wiring type or a double-sided wiring type. In the case of the double-sided wiring type, a via hole forming step for conducting both surfaces of the resin substrate with a laser or the like is performed during the production of the flexible printed wiring board. Moreover, it can be set as a multilayer flexible printed wiring board by laminating | stacking the flexible printed wiring board of this invention.

B. Next, the manufacturing method of the flexible printed wiring board of this invention is demonstrated. The manufacturing method of the flexible printed wiring board of this invention can be divided roughly into two aspects by the formation method of a seed layer. Hereinafter, description will be made for each aspect.

1. First Aspect First, a first aspect in the method for producing a flexible printed wiring board of the present invention will be described. The manufacturing method of the flexible printed wiring board of this aspect is a metal foil for shaping comprising a supporting metal foil having a fine uneven surface and an underlayer formed on the fine uneven surface and containing a metal for improving adhesion. And forming a laminated body by providing a resin substrate on the underlayer of the shaping metal foil, and removing the supporting metal foil from the laminated body to form a resin substrate with an underlayer Forming a resin layer with a base layer, forming a seed layer on the base layer of the resin substrate with the base layer by electroless plating, and forming a resist pattern on the seed layer A wiring plating layer forming step of forming a wiring plating layer in the gap between the resist pattern by an electrolytic plating method, and the seed layer and the wiring plating after the wiring plating layer forming step. A heating step for improving adhesion, a resist pattern removing step for removing the resist pattern after the heating step, and a flash etching step for etching the seed layer other than the metal wiring formation region after the resist pattern removing step It is characterized by having.

  According to this aspect, a flexible printed wiring board having excellent adhesion between the underlayer and the seed layer is obtained by forming the seed layer after forming the resin substrate with the underlayer containing the metal for improving adhesion. be able to. As a result, the adhesiveness between the resin substrate and the metal wiring can be excellent. Moreover, since a vacuum process is not required compared with the conventional sputtering method etc., a flexible printed wiring board can be formed cheaply. In addition, the manufacturing method of the flexible printed wiring board of this aspect uses what is called a semi-additive method.

Next, the manufacturing method of the flexible printed wiring board of this aspect is demonstrated using drawing. FIG. 6 is a process diagram showing an example of a method for producing a flexible printed wiring board of this aspect. The manufacturing method of the flexible printed wiring board of this aspect includes a supporting metal foil 61 having a fine concavo-convex surface, and a shaping metal provided with a base layer 62 formed on the fine concavo-convex surface and containing a metal for improving adhesion. Using the foil A (FIG. 6A), a laminate forming step of forming the laminate B by providing the resin substrate 63 on the base layer 62 of the shaping metal foil A (FIG. 6B), The supporting metal foil 61 is removed from the laminate B, and a resin substrate with base layer forming step (FIG. 6C) for forming the resin substrate with base layer (FIG. 6 (c)) is performed on the base layer 62 of the resin substrate with base layer C. A seed layer forming step for forming the seed layer 64 by electrolytic plating (FIG. 6D), a resist layer 65 is formed on the seed layer 64 (FIG. 6E), and light is transmitted through a photomask or the like. Resist pattern for forming a resist pattern 65 'by irradiation or the like Forming step (FIG. 6 (f)), forming a wiring plating layer 66 by electrolytic plating in the gap between the resist patterns 65 '(FIG. 6 (g)), forming a wiring plating layer Later, a heating step for improving the adhesion between the seed layer 64 and the wiring plating layer 66 (FIG. 6 (h)), and a resist pattern removing step for removing the resist pattern 65 ′ after the heating step (FIG. 6 (i)). And a flash etching step of etching the seed layer 64 other than the metal wiring formation region after the resist pattern removal step (FIG. 6J).
Hereinafter, the manufacturing method of the flexible printed wiring board of this aspect is demonstrated for every process.

(1) Laminate formation process First, the laminate formation process in this aspect is demonstrated. The laminate forming step in this aspect uses a forming metal foil including a supporting metal foil having a fine uneven surface and an underlayer formed on the fine uneven surface and containing a metal for improving adhesion, This is a step of forming a laminate by providing a resin substrate on the base layer of the shaping metal foil.

(A) Metal foil for shaping First, the metal foil for shaping used for this aspect is demonstrated. The metal foil for shaping used in this embodiment comprises a supporting metal foil having a fine uneven surface and an underlayer formed on the fine uneven surface and containing a metal for improving adhesion. In addition, what was demonstrated in FIG. 5 mentioned above etc. can be mentioned as a specific example of the said metal foil for shaping | molding. FIG. 7 is a SEM (scanning electron microscope) photograph showing an example of the surface of the underlayer of the shaping metal foil.

  Although it does not specifically limit as said support metal foil, For example, copper foil or nickel foil etc. can be mentioned, and copper foil is especially preferable. This is because it is versatile and inexpensive. The copper foil may be a rolled copper foil or an electrolytic copper foil.

  The supporting metal foil has a fine uneven surface on the surface. The method for forming the fine uneven surface is not particularly limited, and examples thereof include a method in which copper metal particles are electrodeposited to roughen the copper foil surface.

  The surface roughness Rz of the fine uneven surface is not particularly limited, but is the same as the surface roughness Rz of the resin substrate described in “A. Flexible printed wiring board” described above. Description is omitted.

  Although it does not specifically limit as thickness of the said support metal foil, Usually, it is about 9 micrometers-about 18 micrometers.

  About the said base layer, since it is the same as that of the content described in said "A. flexible printed wiring board", description here is abbreviate | omitted.

(B) Formation method of laminated body Next, the formation method of a laminated body is demonstrated. The method of providing the resin substrate on the fine uneven surface of the shaping metal foil is not particularly limited. For example, the resin substrate is formed on the fine uneven surface by a printing method such as a spin coating method or a cast method. Examples thereof include a method of forming, a method of thermocompression bonding of the shaping metal foil and the resin substrate, and the like.

(2) Base layer-attached resin substrate forming step Next, the base layer-attached resin substrate forming step in this embodiment will be described. The base layer-attached resin substrate forming step in this aspect is a step of removing the supporting metal foil from the above-described laminate and forming the base layer-attached resin substrate.

  The method for removing the supporting metal foil from the laminate is not particularly limited as long as it can leave the base layer on the resin substrate side. For example, only the supporting metal foil is removed using an etching solution. A method of selectively removing, a method of peeling the supporting metal foil, and the like can be mentioned, and among them, a method of selectively removing only the supporting metal foil using an etching solution is preferable.

  The etching solution is not particularly limited. For example, when the supporting metal foil is a copper foil, ferric chloride aqueous solution, alkaline etching solution, hydrogen peroxide solution / sulfuric acid etching solution, persulfate etching Among them, an aqueous ferric chloride solution is preferable. For example, when the supporting metal foil is a nickel foil, a ferric chloride aqueous solution, a hydrogen peroxide solution / sulfuric acid / nitric acid etching solution, and the like can be mentioned, and among these, a ferric chloride aqueous solution is preferable.

(3) Seed layer formation process Next, the seed layer formation process in this mode is explained. The seed layer forming step in this embodiment is a step of forming a seed layer by an electroless plating method on the base layer of the resin substrate with the base layer described above. Usually, the seed layer is formed on the entire surface of the base layer in this step, and is etched in accordance with a pattern of a wiring plating layer or the like by a flash etching step described later. The seed layer is formed in order to produce a wiring plating layer to be described later by electrolytic plating.

  In this embodiment, the seed layer is formed by an electroless plating method, but the electroless plating method is not particularly limited as long as a desired seed layer can be obtained. Can be used.

  The material and thickness of the seed layer are not particularly limited, but are the same as those described in “A. Flexible printed wiring board 3. Seed layer” described above, and thus the description thereof is omitted here. .

(4) Resist pattern formation process Next, the resist pattern formation process in this aspect is demonstrated. The resist pattern forming step in this aspect is a step of forming a resist pattern on the seed layer described above. The resist pattern is formed in a region other than the metal wiring pattern to be obtained, as in the general semi-additive method.

  The method of forming the resist pattern is not particularly limited. For example, a method of forming a resist layer by applying a photocurable resin to the underlayer, exposing through a photomask, and further developing the resist layer Etc.

  The resist pattern material is not particularly limited, and a general resist material can be used.

(5) Wiring plating layer formation process Next, the wiring plating layer formation process in this aspect is demonstrated. The wiring plating layer forming step in this aspect is a step of forming a wiring plating layer in the gap between the resist patterns described above by an electrolytic plating method.

  In this embodiment, the wiring plating layer is formed by an electrolytic plating method, but the electrolytic plating method is not particularly limited as long as a desired wiring plating layer can be obtained, and is a general method. Can be used.

  The metal constituting the wiring plating layer and the thickness and line width of the wiring plating layer are the same as those described in “A. Flexible printed wiring board 4. Wiring plating layer”. Therefore, explanation here is omitted.

(6) Heating process Next, the heating process in this aspect is demonstrated. The heating process in this embodiment is a process for improving the adhesion between the seed layer and the wiring plating layer after the wiring plating process. The heating step is a step of performing a so-called annealing process.

  The heating temperature is the same as that at the time of general annealing treatment, but is usually in the range of 100 ° C to 200 ° C. Moreover, it does not specifically limit as a heating method, For example, the method of using oven etc. can be mentioned. In addition, the said heating process can also be performed after the resist pattern removal process mentioned later or a flash etching process not after a wiring plating process.

(7) Resist pattern removal process Next, the resist pattern removal process in this aspect is demonstrated. The resist pattern removing step in this aspect is a step of removing the resist pattern after the heating step. By removing the resist pattern, a patterned wiring plating layer can be obtained on the seed layer.

  The method of removing the resist pattern is not particularly limited, and examples thereof include a method of decomposing and removing with an alkaline solution.

(8) Flash Etching Step Next, the flash etching step in this embodiment will be described. The flash etching step in this aspect is a step of etching the seed layer other than the metal wiring formation region after the resist pattern removal step. By this step, the seed layer other than the metal wiring formation region is removed, and the fine uneven surface of the resin substrate is exposed. In this aspect, the “metal wiring formation region” refers to a region that is the same as the pattern in which the metal wiring (seed layer and wiring plating layer) is formed in plan view.

  The method for etching the seed layer and the underlayer is not particularly limited, and examples include general dry etching and wet etching. It is preferable to select in consideration of the material of the seed layer. In addition, this step usually removes the seed layer by etching the entire surface.

  Note that in this step, the base layer may or may not be removed, but if the base layer has conductivity, it is necessary to remove it.

2. Second Aspect Next, a second aspect in the method for producing a flexible printed wiring board of the present invention will be described. The manufacturing method of the flexible printed wiring board of this aspect is a metal foil for shaping comprising a supporting metal foil having a fine uneven surface and an underlayer formed on the fine uneven surface and containing a metal for improving adhesion. And forming a laminate by providing a resin substrate on the base layer of the shaping metal foil, and a seed for forming a seed layer by etching the supporting metal foil of the laminate A layer forming step, a resist pattern forming step for forming a resist pattern on the seed layer, a wiring plating layer forming step for forming a wiring plating layer in the gap between the resist patterns by an electrolytic plating method, and the wiring plating layer formation After the step, a heating step for improving the adhesion between the seed layer and the wiring plating layer, and a resist pattern for removing the resist pattern after the heating step. And over down removing step, after the resist pattern removal step, is characterized in that it has a, a flash etching process for etching the seed layer other than the metal wiring formation region.

  According to this aspect, the flexible printed wiring board excellent in adhesiveness can be obtained more simply by using the supporting metal foil of the shaping metal foil as a seed layer. Moreover, since a vacuum process is not required compared with the conventional sputtering method etc., a flexible printed wiring board can be formed cheaply. In addition, the manufacturing method of the flexible printed wiring board of this aspect uses what is called a semi-additive method.

  Next, the manufacturing method of the flexible printed wiring board of this aspect is demonstrated using drawing. FIG. 8 is a process diagram showing an example of a method for producing a flexible printed wiring board of this aspect. The manufacturing method of the flexible printed wiring board of this aspect includes a supporting metal foil 81 having a fine concavo-convex surface and a shaping metal provided on the fine concavo-convex surface and an underlayer 82 containing a metal for improving adhesion. Using the foil A (FIG. 8A), a laminate forming step of forming the laminate B by providing the resin substrate 83 on the base layer 82 of the shaping metal foil A (FIG. 8B), The supporting metal foil 81 of the laminated body B is etched so as to leave a predetermined thickness, and a seed layer forming step for forming the seed layer 84 (FIGS. 8C and 8D), and a resist on the seed layer 84 A resist pattern forming step for forming a resist pattern 85 ′ by forming a layer 85 (FIG. 8E) and irradiating light through a photomask or the like (FIG. 8F); In the gap between A wiring plating layer forming step for forming the layer 86 (FIG. 8G), and a heating step for improving the adhesion between the seed layer 84 and the wiring plating layer 86 after the wiring plating layer forming step (FIG. 8H). ), A resist pattern removing step (FIG. 8 (i)) for removing the resist pattern 85 ′ after the heating step, and a flash etching step for etching the seed layer 84 other than the metal wiring formation region after the resist pattern removing step ( 8 (j)).

(1) Laminate formation process First, the laminate formation process in this aspect is demonstrated. The laminate forming step in this embodiment uses a metal foil for shaping provided with a supporting metal foil having a fine uneven surface and an underlayer having an adhesion improving metal formed on the fine uneven surface, This is a step of forming a laminate by providing a resin substrate on the base layer of the shaping metal foil. Since the laminated body formation process in this aspect is the same as that of the 1st aspect mentioned above, description here is abbreviate | omitted.

(2) Seed layer forming step Next, the seed layer forming step in this embodiment will be described. The seed layer forming step in this aspect is a step of forming a seed layer by etching the supporting metal foil of the above-described laminate. In this embodiment, a flexible printed wiring board can be more easily produced by using the supporting metal foil as a seed layer.

  The method for etching the supporting metal foil of the laminate is not particularly limited. For example, when the supporting metal foil is a copper foil, a method using an aqueous ferric chloride solution as an etching solution can be mentioned. .

  The material and thickness of the seed layer are not particularly limited, but are the same as those described in “A. Flexible printed wiring board 3. Seed layer” described above, and thus the description thereof is omitted here. .

(3) Other process The manufacturing method of the flexible printed wiring board of this aspect further has a resist pattern formation process, a wiring plating layer formation process, a heating process, a resist pattern removal process, and a flash etching process. Since these steps are the same as those in the first embodiment described above, description thereof is omitted here.

3. Others The method for producing a flexible printed wiring board of the present invention may be a method using an additive method in which a wiring plating layer is formed without forming a seed layer. Specifically, using a metal foil for shaping provided with a supporting metal foil having a fine irregular surface and an underlayer containing a metal for improving adhesion formed on the fine irregular surface, Laminate formation step of forming a laminate by providing a resin substrate on a base layer of metal foil, and formation of a resin substrate with a base layer by removing the supporting metal foil from the laminate and forming a resin substrate with a base layer A resist pattern forming step of forming a resist pattern on the base layer of the resin substrate with the base layer, a wiring plating layer forming step of forming a wiring plating layer by an electrolytic plating method in the gap of the resist pattern, A heating step for improving adhesion between the seed layer and the wiring plating layer after the wiring plating layer forming step; and a resist pattern removal step for removing the resist pattern after the heating step. The rear resist pattern removal step, along the wiring plating layer, the underlying layer by etching, and a method such as having a flash etching process for exposing the fine uneven surface of the resin substrate. Since each of the above steps is the same as that in the first aspect described above, description thereof is omitted here.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the technical idea described in the claims of the present invention has substantially the same configuration and exhibits the same function and effect regardless of the case. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described more specifically with reference to examples.

[Example 1]
As the supporting metal foil having a fine uneven surface treatment, 18 μm-thick BHY-22B-T manufactured by Nikko Materials was used, and as the polyimide resin, 25 μm thickness of Upilex VT having a thermoplastic resin on both sides was used. A double-sided CCL material R-F775 made by Matsushita Electric Works, which had the Cu foil laminated on both sides of Upilex VT, was used.

The metal foil support on one side of the CCL with double-sided Cu foil was etched with a ferric chloride solution at 40 ° C. and 37 Baume, leaving the base layer containing the adhesion improving metal, and removing the metal support.
The entire surface of the underlayer was treated with electroless copper plating for 25 minutes to a thickness of about 0.4 μm, washed with hot water and dried to form a seed layer. The electroless Cu plating was performed based on the electroless Cu plating process conditions manufactured by Rohm & Haas Co. shown in Table 1.

  After that, as a dry film, a 15 μm thick Asahi Kasei SPG-152 was used, laminated on the electroless Cu plating surface at a temperature of 105 ° C., and a glass mask formed with a reverse pattern of the desired wiring pattern, Exposure was performed.

  Thereafter, development was performed for about 20 seconds with a 0.8% sodium carbonate solution at 28 ° C. to form a resist pattern. For wiring formation, an electrolytic Cu plating solution of a copper sulfate solution was used to obtain a wiring plating thickness of about 10 μm. Table 2 shows the conditions of copper plating.

  In order to enhance the adhesion between Cu of the seed layer and Cu of the wiring, after heating in an oven at 125 ° C. for 60 minutes, the dry film was peeled off with a 3% sodium hydroxide solution. Thereafter, the seed layer and the underlying metal layer were removed by flash etching with a hydrogen peroxide and sulfuric acid based solution to complete the wiring formation, and a flexible printed wiring board was obtained. Table 3 shows the flash etching conditions.

  After the wiring was formed, the pattern width was 10 mm, 3 mm, the peeling angle was 90 °, and the peeling speed was 50 mm / min. By a method according to IPC-TM-650-2.4.9. The peel strength of the wiring was measured. The measuring instrument used was Autograph AGS-H manufactured by Shimadzu Corporation. The peel strength was measured at an initial stage after leaving the sample at 85 ° C. and 85% RH for 72 hours and after leaving the sample at 177 ° C. for 72 hours.

[Example 2]
A flexible printed wiring board was obtained in the same manner as in Example 1 except that the supporting metal foil was 18 μm-thick USLP manufactured by Nippon Electrolytic Co., Ltd.

[Example 3]
A flexible printed wiring board was obtained in the same manner as in Example 1 except that the supporting metal foil was SLP having a thickness of 18 μm manufactured by Nippon Electrolytic Co., Ltd.

[Example 4]
A flexible printed wiring board was obtained in the same manner as in Example 1 except that the supporting metal foil was 18 μm-thick GP-18 manufactured by Nippon Electrolytic Co., Ltd.
In addition, the result of the peel strength of Examples 1-4 was put together in Table 4.

[Analysis of underlayer on PI surface]
Table 5 shows the results of analyzing the base layer after etching the supporting metal foil after laminating the shaping metal foil on the resin substrate with an X-ray photoelectron spectrometer Quantum 2000 manufactured by ULVAC-PHI. In addition, the following numerical value was computed by making the sum total of the element except C, N, and O into 100.

[Example 5]
As the supporting metal foil having a fine uneven surface treatment, 12 μm-thick BHY-22B-T manufactured by Nikko Materials was used, and as the polyimide resin, 25 μm thickness of Upilex VT having a thermoplastic resin on both sides was used. A double-sided CCL material R-F775 made by Matsushita Electric Works, which had the Cu foil laminated on both sides of Upilex VT, was used.

  A single-sided metal foil support of CCL with double-sided Cu foil was etched with a ferric chloride solution at 30 ° C. and 40 Baume, leaving 1 μm of the support metal foil to form a seed layer.

  After that, as a dry film, a 15 μm thick Asahi Kasei SPG-152 was used, laminated on the Cu surface of the seed layer at a temperature of 100 ° C., and a glass mask formed with a pattern obtained by inverting the desired wiring pattern, Exposure was performed.

  Thereafter, development was performed with a 0.8% sodium carbonate solution for about 20 seconds to form a resist pattern. For wiring formation, an electrolytic Cu plating solution of a copper sulfate solution was used to obtain a wiring plating thickness of about 10 μm. Further, in order to enhance the adhesion between Cu of the seed layer and Cu of the wiring, after heating in an oven at 125 ° C. for 60 minutes, the dry film was peeled off with a 3% sodium hydroxide solution. Thereafter, the seed layer and the underlying metal layer were removed by etching with a hydrogen peroxide or sulfuric acid solution to complete the wiring formation to obtain a flexible printed wiring board.

  After the wiring was formed, the pattern width was 10 mm, 3 mm, the peeling angle was 90 °, and the peeling speed was 50 mm / min. By a method according to IPC-TM-650-2.4.9. The peel strength of the wiring was measured. The peel strength was measured at an initial stage after leaving the sample at 85 ° C. and 85% RH for 72 hours and after leaving the sample at 177 ° C. for 72 hours. The measurement results of peel strength are summarized in Table 6.

[Example 6]
Except that the metal foil support on one side of CCL with double-sided Cu foil was etched using SE-07 manufactured by Mitsubishi Gas Chemical Co., Ltd. leaving 1 μm of the support metal foil, and the seed layer was formed. Thus, a flexible printed wiring board was obtained.

It is a schematic sectional drawing which shows an example of the flexible printed wiring board of this invention. It is a schematic sectional drawing which illustrates the base layer used for this invention. It is a SEM photograph which shows an example of the surface of the resin substrate (polyimide resin) in which the base layer was formed. It is a schematic sectional drawing which illustrates the foundation layer used for the present invention. It is process drawing which shows an example of the formation method of the base layer used for this invention. It is process drawing which shows an example of the manufacturing method of the flexible printed wiring board of a 1st aspect. It is a SEM photograph which shows an example of the base layer surface of the metal foil for shaping. It is process drawing which shows an example of the manufacturing method of the flexible printed wiring board of a 2nd aspect.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Resin substrate 2 ... Underlayer 3 ... Seed layer 4 ... Wiring plating layer 5 ... Adhesion improvement layer 6 ... Heat-resistant treatment layer 7 ... Silane coupling treatment layer 8 ... Copper foil 9 ... Molding copper foil 10 ... Laminate

Claims (7)

A resin substrate having a fine uneven surface, an underlayer formed on the fine uneven surface, a seed layer formed in a pattern on the underlayer, and a wiring plating layer formed on the seed layer Have
The flexible printed wiring board, wherein the underlayer contains a metal for improving adhesion.   2. The flexible print according to claim 1, wherein the underlayer contains at least one metal selected from the group consisting of Ni, Co, Cu, Mo, and Fe as the metal for improving adhesion. Wiring board.   The flexible printed wiring board according to claim 1, wherein the underlayer contains a heat-resistant metal.   The surface roughness Rz of the said fine uneven | corrugated surface exists in the range of 0.1 micrometer-5.0 micrometers, The flexible printed wiring board in any one of Claim 1 to 3 characterized by the above-mentioned.   5. The flexible printed wiring board according to claim 1, wherein a line width of the wiring plating layer is in a range of 3 μm to 30 μm. Using a metal foil for shaping comprising a supporting metal foil having a fine irregular surface and an underlayer containing an adhesion improving metal formed on the fine irregular surface, an underlayer of the shaping metal foil A laminated body forming step of forming a laminated body by providing a resin substrate thereon;
Removing the supporting metal foil from the laminate, and forming a resin substrate with a base layer, forming a resin substrate with a base layer;
A seed layer forming step of forming a seed layer by an electroless plating method on the base layer of the resin substrate with the base layer;
A resist pattern forming step of forming a resist pattern on the seed layer;
A wiring plating layer forming step of forming a wiring plating layer by electrolytic plating in the gap of the resist pattern;
A heating step for improving adhesion between the seed layer and the wiring plating layer after the wiring plating layer forming step;
A resist pattern removing step for removing the resist pattern after the heating step;
A flash etching step of etching the seed layer other than the metal wiring formation region after the resist pattern removal step;
A method for producing a flexible printed wiring board, comprising: Using a metal foil for shaping comprising a supporting metal foil having a fine irregular surface and an underlayer containing an adhesion improving metal formed on the fine irregular surface, an underlayer of the shaping metal foil A laminated body forming step of forming a laminated body by providing a resin substrate thereon;
A seed layer forming step of forming a seed layer by etching the supporting metal foil of the laminate;
A resist pattern forming step of forming a resist pattern on the seed layer;
A wiring plating layer forming step of forming a wiring plating layer by electrolytic plating in the gap of the resist pattern;
A heating step for improving adhesion between the seed layer and the wiring plating layer after the wiring plating layer forming step;
A resist pattern removing step for removing the resist pattern after the heating step;
A flash etching step of etching the seed layer other than the metal wiring formation region after the resist pattern removal step;
A method for producing a flexible printed wiring board, comprising:

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