JPH0681157A - Surface treatment of copper foil for printed circuit - Google Patents

Abstract

PURPOSE:To provide a surface treating method for improving the preservability (moisture resistance) and tarnish resistance of the lustrous surface of copper foil over a long period of time. CONSTITUTION:The lustrous surface of copper foil for a printed circuit is subjected to Zn or Zn alloy plating and chromating, Zn or Zn alloy plating and electrolytic Zn-Cr treatment for forming a chromium oxidezinc and/or zinc oxide mixed coating film, or direct electrolytic Zn-Cr treatment for forming a chromium oxide-zinc and/or zinc oxide mixed coating film. The treated surface is then treated with a silane coupling agent such as epoxysilane, aminosilane, methacrylsilane or styrylsilane. The copper foil can be stored over a long period of time and treatment at a temp. above the conventional temp. is enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a glossy surface of a printed circuit copper foil, and more particularly to a gloss of a printed circuit copper foil for the purpose of improving moisture resistance and burn resistance. It relates to a method of processing a surface.

[0002]

2. Description of the Related Art Generally, a printed circuit copper foil is laminated and adhered to a base material such as a synthetic resin under high temperature and high pressure, and after printing a necessary circuit to form a target circuit, unnecessary parts are removed. An etching process is performed. Finally, the required elements are soldered to form various printed circuit boards for electronic devices. Quality requirements for a copper foil for a printed wiring board are different between a surface bonded to a resin substrate (roughened surface) and a non-bonded surface (glossy surface).

The requirements for the roughened surface are mainly that there is no oxidative discoloration during storage and that the peeling strength from the substrate is sufficient even after high temperature heating, wet treatment, soldering, chemical treatment, etc. For example, there is no so-called laminated stain that occurs after lamination with a substrate or etching.

On the other hand, the glossy surface has a good appearance, no oxidative discoloration during storage, no oxidative discoloration during high temperature heating (heat-resistant oxidation resistance, burnability), and good solder wettability. Good adhesion with the resist is required.

[0005]

Particularly, recently, the copper foil for printed circuits is often exported to foreign countries, and the storage environment including shipping may be bad. May cause oxidation problems in humid summers. Also in Japan, there is a tendency to require a longer-term warranty than before, such as extension of the warranty period.

As a new manufacturing method, a method called two-layer flex has appeared. The two-layer flex is a method in which a polyimide resin is directly applied onto a copper foil and the polyimide resin is cured at a high temperature of 300 ° C. or more to form a flexible substrate, and has a two-layer structure of a polyimide layer and a copper foil layer. It is called 2-layer flexible. Further, even conventional materials may be subjected to high temperature treatment in order to further improve the characteristics.

The copper foil is usually subjected to anticorrosion treatment such as chromate treatment or zinc plating + chromate treatment for the purpose of anticorrosion at the final stage of production. However, the conventional anticorrosion treatment may cause an oxidation trouble if it is stored for a long time in a bad environment such as a humid summer, and if it is treated at a temperature higher than the conventional temperature, it will be discolored.

An object of the present invention is to provide a method for treating the glossy surface of a copper foil for a printed circuit for the purpose of improving the long-term storage property (moisture resistance) and the burn resistance (heat oxidation resistance) of the copper foil glossy surface. To establish.

[0009]

Means for Solving the Problems The present inventors have proposed that the glossy surface of a printed circuit copper foil is plated with Zn or a Zn alloy, and then subjected to chromate treatment or electrolytic zinc / chromium treatment.
Alternatively, it has been found that the above problems can be solved by directly treating the glossy surface with electrolytic zinc / chromium and then treating the treated surface with a silane coupling agent. The silane coupling treatment itself has long been known as a treatment for glass cloth, and has been used exclusively for improving the characteristics of the roughened surface (adhesive surface) of the copper foil, particularly the adhesive strength. For example,
Japanese Unexamined Patent Publication No. 56-118853 discloses that silane is interposed between the prepreg and the roughened surface of the copper foil.
No. 24176, JP-B-61-24177 and JP-B-61-24178, an aminosilane is applied to the roughened surface of copper foil or the roughened surface of copper foil after chromate treatment to prepare an epoxy resin substrate or a polyimide resin substrate. It describes that you do. JP-A-58-84484 describes that silane is applied to a roughened surface of a copper foil to improve acid resistance.
There are many other documents, but these are all related to the improvement of the characteristics of the roughened surface of the copper foil, and there is nothing that clearly states that the silane coupling agent is applied to the glossy surface of the copper foil, let alone There is no mention of improvement in long-term storage property (moisture resistance) and improvement in burn resistance of the glossy surface. It was also confirmed that this silane coupling treatment ensures the required level of solder wettability and resist adhesion.

Based on this finding, the present invention provides (1) Zn or Zn alloy plating on a glossy surface of a printed circuit copper foil,
Then, the Zn or Zn alloy plated surface is chromate-treated, and the chromate-treated surface is further treated with a silane coupling agent. A method for treating a glossy surface of a copper foil for a printed circuit, (2) a copper foil for a printed circuit Zn or Zn alloy plating is applied to the glossy surface, and then a mixed film of chromium oxide and zinc and / or zinc oxide is formed on the Zn or Zn alloy plating surface by electrolytic zinc / chromium treatment. Method for treating shiny surface of copper foil for printed circuit, characterized in that surface treated with chromium is treated with silane coupling agent, and (3) Chromium oxide and zinc by electrolytic zinc / chromium treatment on shiny surface of copper foil for printed circuit Gloss of copper foil for printed circuits characterized by forming a mixed film with and / or zinc oxide, and further treating the electrolytic zinc / chromium treated surface with a silane coupling agent. To provide a processing method.

[0011]

The copper foil used in the present invention may be either electrolytic copper foil or rolled copper foil. First, on the shiny side of the copper foil,
(1) Zn or Zn alloy plating and then chromate treatment, or (2) Zn or Zn alloy plating and then electrolytic zinc / chromium treatment and mixed coating of chromium oxide and zinc and / or zinc oxide. Or (3) direct electrolytic zinc / chromium treatment to form a mixed film of chromium oxide and zinc and / or zinc oxide.

In the cases (1) and (2), Zn or Zn
The alloy plating is first formed. 10 for Zn plating
Plating is performed so as to form a very thin film with an adhesion amount of 0 to 500 μg / dm ² . When the amount of deposited Zn is less than 100 μg / dm ² , the burn resistance (heat-resistant oxidation resistance) deteriorates. 500 μg / dm
^When it exceeds ² , the color tone of Zn metal becomes dark, which is a problem in appearance. Examples of Zn plating conditions are as follows: Zn plating conditions Zn: 10 to 50 g / l pH: 3 to 5 Temperature: 30 to 60 ° C. Current density: 0.1 to 3 A / dm ² Plating time: 0.5 ~ 5 seconds

The Zn alloy plating is, for example, Zn--N.
i, Zn-Co, etc. are typical. Taking Zn-Ni as an example, the Zn-Ni alloy treatment is similarly performed on the glossy surface. The Zn-Ni alloy treatment is preferably 50-97 wt% Zn and 3-50 using a Zn-Ni electroplating bath.
Zn-Ni alloy layer containing 100% by weight of Ni 100-500μ
It is carried out so as to form a very thin film with an attached amount of g / dm ² .
When the amount of Ni is 3% by weight or more, better thermal oxidation resistance is secured as compared with the case of Zn alone. On the other hand, when the amount of Ni exceeds 50% by weight, the solder wettability deteriorates and the thermal oxidation resistance also deteriorates. The adhesion amount is the same as when Zn alone. Zn-
The same applies to the case of Co alloy.

The composition and conditions of the Zn-Ni alloy plating bath are as follows: Zn: 5 to 50 g / l Ni: 5 to 50 g / l pH: 2.5 to 4 Temperature: 30 to 60 ° C. Current density : 0.5 to 5 A / dm ² Plating time: 1 to 10 seconds

In the above (1), after washing with water, Zn or Zn
Chromate treatment is applied on the alloy plating. Either immersion chromate or electrolytic chromate may be used. When weather resistance is required, electrolytic chromate is preferable. The conditions of immersion chromate or electrolytic chromate follow the conditions established in the art. For example, examples of conditions of immersion chromate treatment and electrolytic chromate treatment are as follows: (A) Immersion chromate treatment K ₂ Cr ₂ O ₇ : 0.1 to 5 g / l pH: 2.5 to 4.5 Temperature: 40 -60 ° C Time: 3-8 seconds (B) Electrolytic chromate treatment K ₂ Cr ₂ O ₇ (Na ₂ Cr ₂ O ₇ or CrO ₃ ): 2 to 10 g / l NaOH or KOH: 10 to 50 g / l pH: 7 -13 Bath temperature: 20-80 ° C Current density: 0.05-5 A / dm ² hours: 5-30 seconds

The chromate layer has a Cr content of 15 to 1
It is preferable to have an adhesion amount of 00 μg / dm ² . When the amount of deposited Cr is less than 15 μg / dm ² , the moisture resistance and chemical resistance are deteriorated. When the amount of deposited Cr exceeds 100 μg / dm ² , the wettability of solder and the adhesiveness of a resist such as a UV (ultraviolet curing type) resist ink are adversely affected.

In the case of the above (2), a mixed film of chromium oxide and zinc and / or zinc oxide is formed on the Zn or Zn alloy plating by electrolytic zinc / chromium treatment. The electrolytic zinc / chromium treatment means zinc consisting of zinc or zinc oxide and chromium oxide by electroplating using a plating bath containing zinc salt or zinc oxide and chromate.
This is a treatment for coating the anticorrosion layer of the chromium-based mixture. The plating bath is typically K ₂ Cr ₂ O ₇ , at least one of dichromates such as Na ₂ Cr ₂ O ₇ and CrO _3, and a water-soluble zinc salt such as ZnO, ZnSO ₄ .7H ₂ A mixed aqueous solution of at least one of O and alkali hydroxide is used. Typical plating bath compositions and examples of electrolysis conditions are as follows: (C) Electrolytic zinc / chromium treatment K ₂ Cr ₂ O ₇ : _{2 to} 10 g / l (Na ₂ Cr ₂ O ₇ or CrO ₃ ) Zn: 0.1 to 1 g / l Na ₂ SO ₄ : 5 to 20 g / l pH: 3 to 5 Bath temperature: 20 to 60 ° C. Current density: 0.1 to 3 A / dm ² hours: 1 to 30 seconds Chromium oxide the 15~100μg / dm ² and zinc as the chromium content of the coating amount of 50-500 / dm ² is preferred.
When the amount of deposited Cr is less than 15 μg / dm ² , the moisture resistance and chemical resistance are deteriorated. When the amount of deposited Cr exceeds 100 μg / dm ² , the wettability of the solder and the adhesion of the UV resist ink are adversely affected. If the amount of deposited Zn is less than 50 μg / dm ² , the thermal oxidation resistance (burning property) deteriorates. When it exceeds 500 μg / dm ² , the color tone of Zn metal becomes dark, which causes a problem in appearance.

In the case of the above (3), Zn or Zn alloy plating is omitted, and a mixed film of chromium oxide and zinc and / or zinc oxide is directly applied to the shiny surface of the copper foil by electrolytic zinc / chromium treatment. To form. The conditions are the same as above.

After these treatments (1) to (3), after washing with water, a silane coupling agent is applied to the treated surface. Here, the silane coupling agent has a chemical formula of YRSiX ₃
(In this case, Y is a reactive functional group, for example, a group such as epoxy, amino, vinyl, glycidyloxy, methacryloxy, etc., and R is a bonding group connecting Y with a silicon atom, such as methylene, ethylene, propylene. And an X is a hydrolyzable group that is bonded to a silicon atom and is generally represented by an alkoxy group such as methoxy, ethoxy, and propoxy. For example, epoxy silane (eg, Nippon Unicar Co., Ltd .: trade name A187), aminosilane (eg, Nippon Unicar Co., Ltd .: trade name A1100), methacrylsilane (eg, Nihon Unicar Co., Ltd .: trade name A-174). , Styrylsilane (eg Toray Silicone Co., Ltd.): trade name SZ6
032) is commercially available. The application of the silane coupling agent is usually carried out at room temperature so as to uniformly coat the surface by an appropriate method such as spraying, dipping, or brush coating.

The concentration of the silane coupling agent is 0.001
It is preferably in the range of 10%. This concentration is 0.
If it is less than 001%, the moisture resistance is poor and the antioxidant effect is not obtained. Also, no improvement in burntness is seen. On the other hand, the above concentration is 1
If it exceeds 0%, the appearance tends to be poor (unevenness or the like is generated) and the color tends to change due to heating.

The product obtained after drying has excellent long-term storability and is excellent in burn resistance even when exposed to high temperatures.
It also has the required level of solder wettability and resist adhesion.

The roughened surface of the copper foil can be subjected to any treatment conventionally adopted. That is, after the roughening treatment, it is preferable to perform a treat treatment for forming a single metal layer or an alloy layer of one or more kinds selected from Cu, Cr, Ni, Fe, Co and Zn on the roughened surface. . Examples of alloy plating include Cu-Ni and Cu-C.
o, Cu-Ni-Co, Cu-Zn and the like (for details, see JP-B-56-9028, JP-A-5-9028).
4-13971, JP-A-2-292895, JP-A-2-292894, JP-B-51-35711, JP-B-54-6701 and the like). These treat layers serve as determinants of copper foil health and as barriers.

[0023]

EXAMPLES For the purpose of illustrating the effects of the present invention, a moisture resistance test is shown for long-term storability, and a baking test result is shown for burn resistance as examples and comparative examples. The test method was as follows: For moisture resistance, a copper foil was wound around a paper tube for about 20 m and placed in a constant temperature and humidity bath at 60 ° C.-60% RH to check the oxidative discoloration of the glossy surface of the copper foil. In the baking test, a copper foil 600 mm wide x 100 mm long test piece was put into a predetermined oven and taken out, and then the presence or absence of discoloration of the glossy surface was confirmed (judgment standard: ○ = no discoloration, △ = slightly discoloration Yes, x = discoloration).

(Example I and Comparative Example I) As examples,
As a method 1, (A) Zn (or Zn
-Ni alloy) plating, washing with water (B) chromate treatment, and method 2 is (A) Zn on the glossy surface of the rolled copper foil.
(Or Zn-Ni alloy) plating, and after washing with water, (C) electrolytic zinc / chromium treatment is carried out, and thereafter both are subjected to surface treatment by washing with water → (D) silane coupling agent treatment → drying. did. The processing conditions of (A) to (D) were as follows: (A) Zn (or Zn-Ni alloy) plating Zn: 20 g / l Ni: zero or 10 g / l pH: 4 Temperature: 50 ° C Current density : 1A / dm ² Plating time: 2 seconds (B) Chromate treatment (immersion chromate treatment) K ₂ Cr ₂ O ₇ : 5g / l pH: 3 Temperature: 55 ° C Time: 8 seconds (C) Electrolytic zinc / chromium treatment K ₂ Cr ₂ O ₇ : 5 g / l Zn: 0.5 g / l pH: 3 Bath temperature: 55 ° C. Current density: 0.5 A / dm ² hours: 5 seconds (D) Silane coupling agent treatment 1% epoxysilane (Nippon Unicar Co., Ltd.): Product name A1
87) The solution was applied at room temperature.

As a comparative example, the same rolled copper foil glossy surface was subjected to a surface treatment under the same conditions as described above except that the silane coupling agent treatment (D) was not carried out, that is, only in Method 1 and Method 2. .

The test articles of Examples and Comparative Examples were subjected to the moisture resistance and baking test according to the method described above. The results are shown in Table 1.

[0027]

[Table 1]

(Example II and Comparative Example II) As an example, electrolytic zinc / chromium treatment was directly applied to the glossy surface of a rolled copper foil, followed by washing with water, treatment with a silane coupling agent, and drying to perform surface treatment. . As a comparative example, only electrolytic zinc / chromium treatment was performed and the silane coupling agent treatment was omitted. The conditions of electrolytic zinc / chromium treatment and silane coupling agent treatment were in accordance with Example I. The results are shown in Table 2.

[0029]

[Table 2]

From Tables 1 and 2 it is clear that the test articles according to the invention have excellent moisture resistance and baking properties. When the treatment with the silane coupling agent is not carried out, the moisture resistance and the baking property are poor.

[0031]

EFFECTS OF THE INVENTION The long-term storage property (moisture resistance) and burn resistance of the glossy surface of the copper foil are improved, oxidation trouble does not occur even when it is stored for a long time in a bad environment such as high humidity in the summer, and higher than before. Allowed treatment at temperature.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C25D 11/38 305 H05K 1/09 A 6921-4E

Claims (3)

[Claims] 1. Zn or Zn is applied to the glossy surface of a printed circuit copper foil.
A method for treating a shiny surface of a copper foil for a printed circuit, which comprises subjecting the Zn or Zn alloy-plated surface to a chromate treatment and then subjecting the chromate-treated surface to a silane coupling agent. 2. Zn or Zn is applied to the glossy surface of a printed circuit copper foil.
Alloy plating is performed, and then a mixed film of chromium oxide and zinc and / or zinc oxide is formed on the surface of the Zn or Zn alloy plating by electrolytic zinc / chromium treatment. A method for treating a glossy surface of a copper foil for a printed circuit, which comprises treating with a ring agent. 3. A mixed film of chromium oxide and zinc and / or zinc oxide is formed by electrolytic zinc / chromium treatment on the glossy surface of a printed circuit copper foil, and the electrolytic zinc / chromium treated surface is further coated with a silane cup. A method for treating a glossy surface of a copper foil for a printed circuit, which comprises treating with a ring agent.