JP5075099B2 - Surface-treated copper foil, surface treatment method thereof, and laminated circuit board - Google Patents

Description

  The present invention relates to a surface-treated copper foil, and in particular, a surface-treated copper foil capable of forming an accurate circuit as a laminated circuit board to be used by bonding with polyimide at a high temperature, a method for producing the same, and the copper foil. The present invention relates to a laminated circuit board.

  When copper foil for printed wiring boards is bonded to a resin substrate, it is necessary to improve the adhesive strength and satisfy the required electrical characteristics, etching characteristics, heat resistance, and chemical resistance as a printed wiring board. is there. Therefore, the surface of the copper foil after the foil production (hereinafter sometimes referred to as an untreated copper foil) is subjected to a roughening treatment on the surface of the resin substrate, and further the zinc (Zn) on the surface subjected to the roughening treatment. Various contrivances have been made such as plating, nickel (Ni) plating, etc., and further, chromate treatment or the like on the surface plated with Zn or Ni plating.

  An IC mounting substrate for driving a liquid crystal display as a display unit of a personal computer, a mobile phone or a PDA has recently been increased in density, and high temperature processing and an accurate circuit configuration are required in the manufacturing process.

In multilayer circuit boards for manufacturing printed wiring boards, the adhesion of electrolytic copper foil that forms conductive circuits and polyimide, which is a resin board that can be used at high temperatures, is several hundred degrees in response to requirements for accurate processing and circuit configuration at high temperatures. For example, at 330 ° C. and 12 MPa.
In this high-temperature bonding treatment, the copper foil has a problem of improving the bonding strength with polyimide at a high temperature. As a means for solving this problem, for example, Patent Document 1 discloses a technique of roughening a copper foil surface with a Zn-containing alloy.

  Moreover, as a laminated circuit board to be used by bonding copper foil with polyimide at high temperature, the adhesion surface of the untreated copper foil with polyimide substrate contains at least one of molybdenum, iron, cobalt, nickel, and tungsten. There has been proposed a surface-treated copper foil in which a surface treatment is performed with an electrolytic solution and a Ni plating layer, a Zn plating layer, or a Ni plating layer + Zn plating layer is further provided on the plating layer (see Patent Document 2).

JP 2000-269637 A JP-A-11-256389

  The roughening treatment layer including the Zn layer described in the patent document is effective in improving the adhesive strength between the copper foil and the resin substrate at a high temperature. However, after bonding the copper foil to the resin substrate, forming a circuit by etching with an acid solution, zinc easily dissolves in the acid, so the Zn layer bonding between the copper foil and the circuit substrate is dissolved, There is a concern that the adhesive strength between the copper foil and the resin substrate after the circuit formation is extremely lowered, and an accident that the copper foil is peeled off from the resin substrate while the circuit substrate is used may occur. In order to prevent such an accident, it is necessary to shorten the etching time and minimize the dissolution and outflow of the Zn layer. The etching process requires advanced technology and a management system, and the productivity of the multilayer circuit board is lowered. At the same time, there was a disadvantage that caused high costs.

  As described above, in the roughening treatment disclosed in the patent document, as described above, the adhesive strength with respect to polyimide, the acid resistance, and the etching resistance cannot be satisfied, and the surface-treated copper foil satisfying these characteristics is obtained. Was not provided.

  The present invention provides a surface-treated copper foil that satisfies all adhesive strength, acid resistance, and etching properties with polyimide, a method for producing the surface-treated copper foil, and a laminated circuit board using the surface-treated copper foil. Objective.

The surface-treated copper foil of the present invention is a surface-treated copper foil in which a surface-treated layer made of a Ni—P—Zn alloy is applied to at least one surface of an untreated copper foil, and the Zn—of the Ni—P—Zn alloy The content is 5 wt% to 60 wt%, the Ni content is 35 wt% to 90 wt%, and the P content is 0.1 wt% to 15 wt% .

  The surface treatment method of the copper foil of the present invention is as follows: Ni: 1.0 to 150 g / L, P: 0.01 to 20 g / L, Zn: 0.01 to 20 g / L on at least one surface of the untreated copper foil. This is a copper foil surface treatment method for forming a surface treatment layer made of a Ni—P—Zn alloy with an electrolytic bath contained.

The laminated circuit board according to the present invention has a Ni content of 5 wt% to 60 wt%, an Ni content of 35 wt% to 90 wt%, and a P content of 0.1 wt% to 15 wt% on at least one surface of the untreated copper foil. It is a laminated circuit board in which a surface treatment layer made of a P—Zn alloy is provided and the surface of the surface treatment layer is bonded to a resin substrate.
In the multilayer circuit board of the present invention, the initial peel strength of the bonding surface between the copper foil and the resin substrate is 0.6 kN / m or more, and the peel strength after heat treatment is 0.48 kN / m or more. There is a laminated circuit board having a peel strength after acid treatment of 0.6 kN / m or more.

According to the surface-treated copper foil of the present invention, it is possible to provide a surface-treated copper foil that satisfies adhesive strength with polyimide, acid resistance, and etching properties.
Moreover, according to the surface treatment method of the copper foil of this invention, the surface treatment method of the copper foil which satisfies the adhesive strength with a polyimide, acid resistance, and etching property can be provided.
Furthermore, according to the multilayer circuit board of the present invention, it is possible to provide a multilayer circuit board that has a strong adhesive strength between a resin substrate, particularly polyimide and copper foil, has acid resistance when forming a circuit, and satisfies etching properties. .

In the present invention, the surface-treated copper foil (untreated copper foil) may be either an electrolytic copper foil or a rolled copper foil. In addition, when it is not necessary to distinguish these in particular, it may be expressed simply as copper foil or untreated copper foil. The thickness of the untreated copper foil is preferably 5 μm to 12 μm. This is because if the thickness of the copper foil is less than 5 μm, for example, wrinkles or the like enter during the production, and the production of the thin copper foil is costly and impractical.
In addition, when the foil thickness is thicker than 12 μm, it is not preferable because it falls outside the specifications of thin and miniaturization such as an IC mounting substrate for driving a liquid crystal display which is a display unit of a personal computer, a mobile phone or a PDA. If required, it is possible to adopt a thick copper foil regardless of the above thickness.

In the present invention, a surface treatment is performed by providing a ternary alloy layer of nickel (Ni) -phosphorus (P) -zinc (Zn) on the surface of the copper foil.
The surface treatment layer provided on the surface of the copper foil contains Ni in order to prevent copper from diffusing from the copper foil into the surface treatment layer, and its content is 35 wt% to 90 wt%, preferably 60 wt% to 80 wt%. is there. This is because the acid resistance is poor when the content is lower than 35 wt%, and the etching property is worse when the content is higher than 90 wt%. The lower limit of the Ni content is preferably 60 wt% in order to reliably prevent copper diffusion from the copper foil, improve acid resistance, increase reliability, and put it into practical use. Is 80 wt% in order to facilitate etching and facilitate circuit formation.

  The reason why P is contained in the surface treatment layer provided on the surface of the copper foil is to make the Ni—P—Zn alloy layer uniform and to suppress excessive precipitation of Ni, and its content is preferably 0.1 wt% to 15 wt%. Is 3 wt% to 10 wt%. This is because if the P content is lower than 0.1 wt%, there is no effect of adding P, and if it is higher than 15 wt%, the initial peel strength decreases. The reason why the lower limit of the preferable P content is 3 wt% is that the Ni—P—Zn alloy layer becomes more uniform and the etching property is better, and the upper limit is 10 wt% because the peel strength is lowered. This is because the excessive precipitation of Ni is reliably suppressed while suppressing.

  The reason why Zn is contained in the treatment layer provided on the surface of the copper foil is to improve the adhesive strength with the resin substrate (particularly polyimide) and to prevent deterioration of the adhesive strength due to heat at the time of adhesion. 5 wt% to 60 wt%, preferably 10 wt% to 40 wt%. If the content is lower than 5 wt%, the effect of adding Zn does not appear, and if it is higher than 60 wt%, the acid resistance is poor.

  FIG. 1 shows the relationship between the Zn content and the peel strength (kN / m) in the Ni—P—Zn alloy layer. FIG. 1 (a) shows the initial state immediately after the surface-treated copper foil is bonded to polyimide. Fig. 1 (b) shows the relationship between peel strength and Zn content, Fig. 1 (b) shows the relationship between the peel strength and Zn content of a surface treated copper foil laminated to a polyimide, and Fig. 1 (c) shows the surface treatment of polyimide. It is the graph which measured the relationship between the peel strength after constructing a circuit by acid treatment etching, and Zn content after pasting together copper foil.

If the initial peel strength and the peel strength after acid treatment in the laminated sheet of copper foil and polyimide are 0.6 kN / m or more, it can be put into practical use without problems in reliability, and the peel strength after heat treatment should be 0.48 kN / m or more. Can be put to practical use without any problem in reliability. For this reason, as a criterion for peel strength, the initial peel strength and the peel strength after acid treatment were set to 0.6 kN / m or more, and the peel strength after heat treatment was set to 0.48 kN / m or more. From FIG. 1 (a), the Zn content does not affect the initial peel strength. From FIG. 1 (b), if the Zn content is low, the peel strength after heat treatment is lowered, but if there is a content of 5 wt% or more, it is practical. The peel strength after the heat treatment is satisfactory if it is 10 wt% or more.
Moreover, the peel strength after acid treatment tends to decrease when the Zn content exceeds 40 wt% from FIG. 1 (c), and extremely decreases when the content exceeds 60 wt%. From these results, the Zn content is 5 wt% to 60 wt%, preferably 10 wt% to 40 wt%.

  In the present invention, it is preferable that the surface roughness of the copper foil on the surface treatment side is 0.2 μm to 1.0 μm in Rz defined by JIS B 0601.

Formation of the Ni—P—Zn alloy layer on the copper foil surface is performed by electrolytic treatment.
The composition of Ni, P, and Zn as the electrolytic treatment bath is as follows.
Ni: As a Ni component, 1.0 g / L to 150 g / L, preferably 25 g / L to 55 g / L is contained.
P: As a P component, 0.01 g / L to 20 g / L, preferably 0.2 g / L to 1.0 g / L is contained.
Zn: 0.01 g / L to 20 g / L, preferably 0.5 g / L to 1.0 g / L, as a Zn component.
The temperature of the electrolytic bath is 30 ° C to 70 ° C, preferably 40 ° C to 60 ° C.

  In addition, after forming the Ni-P-Zn alloy layer on the copper foil surface, it is preferable to provide a chromate treatment layer and a coupling treatment layer on the alloy layer surface.

  The present invention will be described more specifically with reference to examples.

<Example 1>
As the copper foil (untreated copper foil), WZ copper foil (Rz: 1.0 μm) of Furukawa Circuit Foil Co., Ltd. was used.
The chemicals used for the preparation of the electrolytic bath include NiSO ₄ · 6H ₂ O as the Ni metal component, NaH ₂ PO ₂ · H ₂ O as the P component, ZnSO ₄ · 7H ₂ O as the Zn metal component, and other components As H ₃ BO ₃ , the amount shown in Table 1 was added to adjust the electrolytic bath. Table 1 also shows the bath temperature, pH, current density, and treatment time as electrolysis conditions.
The untreated copper foil was subjected to a surface treatment with an electrolytic bath having the above composition and its conditions. The following measurements were performed on the surface-treated copper foil, and the measurement results are shown in Table 2.

(1) Alloy composition of the surface treatment layer deposited on the surface of the copper foil: analyzed by fluorescent X-ray.
(2) Initial peel strength: The surface-treated copper foil was bonded to a polyimide resin (Ube Industries, Ltd .; Upilex 25VT) by hot pressing, and the peel strength after bonding was measured. Since the initial peel strength is required to be 0.6 kN / m or more, 0.6 kN / m or more was considered acceptable. The determination criteria are shown in Table 2.

(3) Peel strength after heat treatment: After bonding with polyimide, the peel strength after heat treatment at 150 ° C. for 168 hours was measured. Since the peel strength after the heat treatment is required to be 0.48 kN / m or more, 0.48 kN / m or more was regarded as acceptable. The determination criteria are shown in Table 2.
(4) Peel strength after acid treatment: After bonding the surface-treated copper foil to polyimide, it was immersed in a dilute hydrochloric acid solution (water: hydrochloric acid = 1: 1) at room temperature for 1 hour, and then the peel strength was measured. Since the initial peel strength is required to be 0.6 kN / m or more, 0.6 kN / m or more was considered acceptable. The determination criteria are shown in Table 2.

(5) Etching property: After bonding the surface-treated copper foil to polyimide, SEM observation was performed on a 1 mm wide circuit cut with a cupric chloride solution, the bottom width and top width were measured, and the difference was obtained. It was. Since the difference between the bottom width and the top width is required to be small, the difference is determined to be within 6 μm. The determination criteria are shown in Table 2.

<Examples 2 to 7>
Using the same untreated copper foil as in Example 1, surface treatment was performed under the conditions shown in Examples 2 to 7 in Table 1, and the same measurements as in Example 1 were performed on the produced surface-treated copper foil. The measurement results are shown in Table 2 as Examples 2 to 7.

<Comparative Examples 1-6>
Using the same untreated copper foil as in Example 1, surface treatment was performed under the conditions shown in Comparative Examples 1 to 6 in Table 1, and the same measurements as in Example 1 were performed on the produced surface-treated copper foil. The measurement results are shown in Table 2 as Comparative Examples 1-6.

  As shown in Table 2, in Example 1, the Ni content is higher than 80 wt% and the Zn content is lower than 10 wt%, both of which are out of the preferred range, and each characteristic is slightly inferior, but as a whole, practical There is no problem with the property and it is satisfactory (overall evaluation ○).

  In Example 2, since the Ni content was higher than 80 wt%, the etching property at the time of circuit formation was somewhat difficult, but the other characteristics were good, and there was no problem in practicality as a whole, which was satisfactory. (Comprehensive evaluation ○).

In Examples 3 and 4, the Ni content is 60 to 80 wt%, the P content is 3 to 10 wt%, and the Zn content is 10 to 40 wt%, which satisfies the satisfactory values of each characteristic (overall evaluation ◎). .

  In Examples 5 and 6, since the Zn content is higher than 40 wt%, the peel strength after the initial treatment and after the heat treatment clears the satisfactory value, but the peel strength after the acid treatment is slightly below the satisfactory value. However, there is no problem in practicality as a whole, and it is satisfactory (overall evaluation ○).

  In Example 7, the P content is 0.1 wt% or more, but is lower than 3 wt%, and since the P content is slightly less, there are some difficulties in etching properties. In Example 8, the P content was higher than 10 wt%, and the initial Peel strength was slightly below the satisfactory value because of the high P content. However, both Examples 7 and 8 are satisfactory as a whole, and are satisfactory (overall evaluation ○).

  In Comparative Examples 1 and 2, the Ni content is lower than 35 wt% and the Zn content is higher than 60 wt%. In particular, since the Zn content is high, the peel strength after the initial treatment and after the heat treatment clears the satisfactory value, but the peel strength after the acid treatment and the etching property cannot be satisfied (overall evaluation ×).

  Since Comparative Example 3 does not contain Zn, the peel strength after heat treatment is inferior, and Comparative Example 4 is surface-treated only with Zn, so that the peel strength after acid treatment and the etching property are inferior, making it suitable as a circuit board. (Comprehensive evaluation x).

  In Comparative Example 5, the P content is lower than 0.1 wt%, and the P content is low, so the etching property is inferior. In Comparative Example 6, the P content is higher than 15 wt%, and the initial P peel strength is high because the P content is large. Is low and lacks suitability as a circuit board (overall evaluation ×).

From the results shown in Table 2, the following ranges are appropriate ranges for the appropriate values of Ni, P, and Zn content in the Ni-P-Zn alloy.

Appropriate value of Ni content The peel strength after acid treatment decreases when the Ni content is small, but if it is 35 wt% or more, there is no effect on practicality, and if it is 60 wt% or more, it is good. Moreover, although etching property falls, when Ni content is high, if it is 90 wt% or less, there will be no influence on practicality, and if it is 80 wt% or less, it will become favorable. From the above results, the appropriate value for the Ni content is 35 wt% to 90 wt%, preferably 60 wt% to 80 wt%.

Appropriate value of P content Etching properties decrease when the P content is small, but if it is 0.1 wt% or more, there is no effect on practicality, and if it is 3 wt% or more, it is good. Further, the initial peel strength (adhesion) decreases when the P content is high, but if it is 15 wt% or less, there is no effect on practicality, and if it is 10 wt% or less, it is good. From the above results, the appropriate value of the P content is 0.1 wt% to 15 wt%, preferably 3 wt% to 10 wt%.

Appropriate value of Zn content The peel strength after heat treatment decreases when the Zn content is low, but if it is 5 wt% or more, there is no effect on practicality, and if it is 10 wt% or more, it is good. Further, the peel strength after acid treatment decreases when the Zn content is high, but if it is 60 wt% or less, there is no effect on practicality, and if it is 40 wt% or less, it becomes good. From the above results, the appropriate value of Zn content is 5 wt% to 60 wt%, preferably 10 wt% to 40 wt%.

As described above, the surface-treated copper foil of the present invention is an industrially superior surface-treated copper foil that satisfies the adhesive strength with polyimide, acid resistance, and etching properties.
Moreover, according to the surface treatment method of the copper foil of this invention, the surface treatment method of the copper foil which industrially satisfies the adhesive strength with a polyimide, acid resistance, and etching property can be provided.
Furthermore, according to the multilayer circuit board of the present invention, it is possible to provide a multilayer circuit board that has a strong adhesive strength between a resin substrate, particularly polyimide and copper foil, has acid resistance when forming a circuit, and satisfies etching properties. Have excellent effects.

It is a graph which shows the relationship between content of Zn in a Ni-P-Zn alloy layer in a copper foil surface treatment layer, and peel strength.

Claims (3)

A surface-treated copper foil in which a surface treatment layer made of a Ni—P—Zn alloy is applied to at least one surface of an untreated copper foil, wherein the Zn content of the Ni—P—Zn alloy is 5 wt% to 60 wt%
Ni content is 35wt% ~ 90wt%
P content is 0.1wt% ~ 15wt%
Is a surface-treated copper foil.   In an electrolytic bath containing Ni: 1.0 to 150 g / L, P: 0.01 to 20 g / L, Zn: 0.01 to 20 g / L on at least one surface of the untreated copper foil, Ni—P—Zn A copper foil surface treatment method for forming a surface treatment layer made of an alloy. Zn content of 5 wt% to 60 wt% on at least one side of the untreated copper foil
Ni content is 35wt% ~ 90wt%
P content is 0.1wt% ~ 15wt%
A laminated circuit board comprising a surface treatment layer made of a Ni—P—Zn alloy and bonding the surface of the surface treatment layer to a resin substrate.

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