JP4083927B2 - Copper foil surface treatment method - Google Patents

Description

の浴中において、10A/dm²、10秒間陰極電解し、水洗後、

の浴中において、5A/dm²、80秒間陰極電解し、水洗した。

の浴中において 0.5A/dm²、5秒間陰極電解し、水洗後、乾燥させた。
この銅箔の表面特性（均一性、表面粗さ）を調べた。その結果を表１に示す。
また、この銅箔の粗面を被着面としてFR-4グレードのガラスエポキシ樹脂含浸基材に積層し、40kgf/cm² の圧力、170℃、60分間の条件でプレスし、成型した。その銅張積層板の特性(接着力、銅残)を調べた。その結果を表１に示す。
【００２０】
(実施例２)
実施例１において、 (A)浴の代わりに

の浴中において、10A/dm²、8秒間陰極電解し、水洗し、
次いで実施例１の(B)浴中において5A/dm² 120秒間陰極電解すること以外は全て実施例１と同じ方法で処理し、同じ方法で各特性試験を行った。
その結果を表１に示す。
【００２１】
(実施例３)
実施例１において、(A)浴の代わりに

の浴中において、10A/dm²、10秒間陰極電解すること以外は全て実施例１と同じ方法で処理し、同じ方法で各特性試験を行った。その結果を表１に示す。
【００２２】
(実施例４)
実施例１において、(A)浴の代わりに

の浴中において、10A/dm²、10秒間陰極電解すること以外は全て実施例１と同じ方法で処理し、同じ方法で各特性試験を行った。その結果を表１に示す。
【００２３】
(実施例５)
実施例１において、(A)浴の代わりに

の浴中において、10A/dm²、10秒間陰極電解すること以外は全て実施例１と同じ方法で処理し、同じ方法で各特性試験を行った。その結果を表１に示す。
【００２４】
(実施例６)
実施例１において、(A)浴の代わりに

の浴中において、10A/dm²、10秒間陰極電解すること以外は全て実施例１と同じ方法で処理し、同じ方法で各特性試験を行った。その結果を表１に示す。
【００２５】
【比較例】
(比較例１)
実施例１において、(A)浴の代わりに

の浴中において、10A/dm²、10秒間陰極電解すること以外は全て実施例１と同じ方法で処理し、同じ方法で各特性試験を行った。その結果を表１に示す。
【００２６】
(比較例２)
比較例１において(I)浴中において電解時間を18秒としたこと以外は同じ処理を行った。また、この銅箔を実施例１と同じ方法で各特性試験を行った。
その結果を表１に示す。
【００２７】
【表１】

【００２８】
表１において、
「均一性」は表面形状を電子顕微鏡により約1000倍の倍率で観察し、
(1)粗化粒子が粗大でなく、大小の差が小さく均一であるもの−〇
(2)粗化粒子が粗大でないが、大小の差がややあるもの −□
(3)粗化粒子が粗大で、不均一であるもの −△
(4)粗化粒子がきわめて粗大で不均一であるもの −×
と評価を行った。
「接着力」はその基材からの引きはがし強度を示し、JIS-C-6481-1986 5.7項の方法に準じた。
「エッチング基板面残留銅」は塩化第二銅エッチングにより、銅をエッチング除去後、50倍の倍率で実体顕微鏡観察を行った。
(1)残銅が全く無いもの −○
(2)残銅が認められるもの−× で評価した。
【００２９】
【発明の効果】
上記、表１の結果から、本発明の表面処理方法は従来の表面処理方法よりも表面形状の均一性が高く、樹脂との接着力に優れ、表面粗さを低減させる効果を持っており、優れた表面処理銅箔となっていることがわかる。
以上、本発明の表面処理方法には、次のような効果がある。
(1)従来のようなヒ素、セレン、テルルなど毒性のある元素を使用せずに粗面化処理する方法であり、環境及び人体への悪影響が全く無い。
(2)粗面形状が均一でかつ、適用樹脂に対し接着力の高い表面処理銅箔が得られ、高密度のプリント配線板に適合する。
(3)この表面処理方法は実工程において、軽い表面処理で済むので導入が非常に容易であり、量産製造が可能である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface treatment of a copper foil, and in particular, in a conductor application typified by a printed wiring board, the copper foil is subjected to a surface treatment having a uniform rough surface shape and high adhesiveness to an applied resin. It is related to the method applied to.
[0002]
[Prior art]
Copper foil is used in large quantities especially for printed wiring boards for electronic and electrical materials.
Printed wiring boards have been improved in performance and reliability. Therefore, required characteristics are complicated and diversified. Similarly, strict quality requirements have been imposed on copper foil, which is one of the constituent materials of this printed wiring board.
In the production of the printed wiring board, first, the rough surface side of the copper foil is laminated together with the synthetic resin-impregnated base material, and heat-pressed by a press to obtain a copper-clad laminate. In general, a glass epoxy substrate often used is completed by pressing at a temperature of about 170 ° C. for 1 to 2 hours.
[0003]
As copper foils for printed wiring boards, electrolytic copper foils having one side rough surface and one side glossy surface are overwhelmingly used. Usually, the electrolytic copper foil is subjected to electrolytic deposition of copper from an electrolytic solution of copper by an electrodeposition apparatus to produce a raw foil called untreated copper foil, and then a series of surface treatments are performed by a processing apparatus.
Generally, the rough surface side (non-gloss surface side) is pickled and roughened to ensure adhesion to the resin, and the adhesive properties such as heat resistance, chemical resistance, and etching properties The process to improve and stabilize is completed. Various techniques have been developed and proposed for these treatments, resulting in a highly functional surface. In the recent increase in the density of printed wiring boards, for example, in thin printed wiring boards and build-up printed wiring boards, the resin layer that becomes the insulating layer is extremely thin. May cause problems.
[0004]
In addition, a fine profile has been desired to reduce the profile on the rough surface side, for example, because the smaller copper foil rough surface can maintain insulation between lines. However, if the adhesive strength is not sufficient, delamination problems such as peeling and floating of the copper foil circuit will occur during the manufacturing process and after the product has been produced. Therefore, the development of a better surface treatment method has been awaited.
[0005]
On the other hand, on the opposite side and glossy side, different characteristics from the rough side, that is, heat discoloration, solder wettability, resist adhesion, etc. are required. A method is needed. However, for multilayer printed wiring board applications, there is no need for solder wettability, particularly when applied as an inner layer, and it has not been necessary to apply a roughening treatment to the glossy side. However, other than the copper foil called DT foil (Double treatment, double-sided treatment), a light roughening treatment has been demanded for increasing the adhesion of the resist and the adhesion of the inner layer treatment during the formation of the printed board.
[0006]
As described above, complicated treatments have been developed to meet various demands on both sides of the copper foil. In the prior art, various techniques related to the roughening treatment have been proposed. For example, Japanese Patent Publication No. 53-38700 has three-stage electrolytic treatment in an acidic electrolytic bath containing arsenic, and Japanese Patent Publication No. 53-39327 and Japanese Patent Publication No. 54-38053 have arsenic, antimony, bismuth, selenium and tellurium. There is a method of performing electrolysis around a limiting current density in an acidic copper electrolytic bath containing arsenic, and arsenic is often used in practice. Japanese Patent Publication No. 61-54592 and Japanese Patent Laid-Open No. 4-202796 propose surface roughening treatment by alternating current electrolysis.
[0007]
However, in the conventional roughening treatment as described above, the use of substances harmful to the human body such as arsenic, selenium, and tellurium has been extremely limited due to environmental problems. From the viewpoint of reuse of printed boards or industrial waste, there is concern about accumulation of harmful components contained in copper foil, and alternative methods are strongly demanded.
Furthermore, in the case of AC electrolysis, since a high-temperature hydrochloric acid bath is used, the mist of hydrochloric acid gas is extremely corrosive to copper, and strict care is required in surface treatment. Sufficient adhesion cannot be obtained.
[0008]
[Problems to be solved by the invention]
The problem to be solved by the present invention is a new roughness that is uniform and low in surface roughness and can provide sufficient adhesion without using toxic elements such as arsenic, selenium, and tellurium as in the prior art. It is to develop the surface treatment.
[0009]
[Means for Solving the Problems]
In the present invention, at least one surface of a copper foil is subjected to cathodic electrolysis in a sulfuric acid or copper sulfate electrolytic bath containing aluminum ions and / or titanium ions at or near the limit current density, thereby depositing copper protrusions. The copper foil surface treatment method is characterized in that a roughening treatment is performed, copper or a copper alloy is coated thereon, and then a rust prevention treatment is performed.
[0010]
Specifically describing the surface treatment method of the present invention, first, the untreated copper foil is acid-washed to remove surface oxides and dirt. Then, the roughening process of this invention is performed to the rough surface side surface. As the treatment liquid, sulfuric acid containing an additive element and an aqueous copper sulfate solution are used. As the sulfuric acid concentration, a range of 50 to 200 g / l is usually used, but depending on conditions such as liquid temperature and current density, it is possible to deviate from this range.
The additive element is aluminum ion and / or titanium ion, and its concentration is preferably 0.03 to 5.0 g / l, and if it is 0.03 g / l or less, the effect of homogenizing the rough surface may be low. Above g / l, even if the amount added is increased, the effect is not improved any more and it becomes uneconomical.
As for the concentration range, in the case of aluminum ions, 0.1 to 3 g / l is better, and in the case of titanium ions, 0.03 to 0.5 g / l is even better. In the case of titanium ions, the addition method is preferably a titanium dioxide solution. In the case of aluminum ions, aluminum sulfate, potassium aluminum sulfate, sodium aluminum sulfate or the like is used.
[0011]
Cathodic electrolysis on the surface of the copper foil varies depending on time, temperature, and the required amount of roughening.
The cathodic electrolysis time is 2 to 60 seconds and the bath temperature is 10 to 50 ° C. The current density is 5 to 100 A / dm ² , and ²⁰ to 200 coulomb / dm ² is appropriate as the amount of electricity, and more specifically 40 to 130 coulomb / dm ² is more preferable. After this treatment, copper or copper alloy is coated on the copper protrusions or dendritic precipitates to improve the adhesion of the copper protrusions. As the processing conditions, for example,
CuSO ₄・ 5H ₂ O 250g / l
H ₂ SO ₄ 100 g / l
The roughened surface is completed by a bath temperature of 50 ° C., a current density of 5 A / dm ² , and cathodic electrolysis for about 80 seconds.
[0012]
When aluminum ions and / or titanium ions are not added to the treatment liquid in the roughening treatment of the present invention, the rough surface shape obtained from the copper protrusions is extremely uneven and coarse dendrites are generated, and press molding is performed. Later, residual copper may be generated on the etched substrate surface. This defect is fatal for a printed wiring board. In addition, the wiring density is high even if it is not a remaining copper, and the fineness of the wiring edge due to a delicate etching time is inferior, and there is a possibility of short-circuiting between wirings, resulting in a problem in insulation.
[0013]
On the other hand, when aluminum ions and / or titanium ions are added to the treatment liquid, aminium ions and titanium ions are difficult to eutect with copper, but have a function of suppressing copper precipitation. By this function, copper deposition can be made uniform.
Titanium ions also have a function of refining copper deposit protrusions. When the tendency is too strong, the sticking property of the copper protrusions may be lowered, but the sticking property will be improved if the subsequent copper or copper alloy coating treatment is applied to many eyes.
[0014]
Thus, the roughened copper foil has a uniform rough surface shape, a reduced surface roughness, and becomes a rough surface suitable for a fine pattern.
The copper foil subjected to the roughening treatment of the present invention is subjected to rust prevention treatment (treatment for imparting heat resistance and chemical resistance) after coating plating with copper or a copper alloy. A barrier layer of Co-Mo, W or Cu-Zn, such as Kokoku 2-24037 or JP-B-8-19550, or another known barrier layer may be formed to enhance heat resistance.
[0015]
Rust prevention treatment includes chromate treatment, organic rust prevention treatment typified by benztriazole, and silane coupling agent treatment, which can be carried out singly or in combination. The chromate treatment uses an aqueous solution containing dichromate ions, which may be acidic or alkaline, and is subjected to immersion treatment or cathodic electrolysis treatment. As the chemical, chromium trioxide, potassium dichromate, sodium dichromate, etc. are used. Organic rust prevention of benzotriazoles includes methylbenzotriazole, aminobenzotriazole, carboxyl benzotriazole, benzotriazole, etc., and is applied as an aqueous solution by immersion treatment or spray treatment. There are various types of silane coupling agents, such as those having an epoxy group, amino groups, methylcapto groups, and vinyl groups, but it is preferable to use ones that are compatible with the resin, such as immersion treatment or spray treatment as an aqueous solution. Apply by.
The copper foil for printed wiring boards is completed by the above process.
[0016]
As described above, conventionally, the glossy surface side of the copper foil usually does not need to be roughened except as a double-sided copper foil (DT foil) used for the inner layer of the multilayer board.
However, in recent years, there has been a demand for a DT foil that has been subjected to a fine, uniform and light roughening treatment in advance in order to eliminate resist adhesion, soft etching process, and increase the adhesion of inner layer processing in printed wiring board manufacture. .
The copper foil subjected to the surface treatment of the present invention has a uniform surface shape and high adhesion to the applied resin, and therefore can be applied as a DT foil that can meet these demands.
When the copper foil is subjected to the surface treatment of the present invention, the roughening amount on the glossy surface side of the copper foil may be appropriately reduced as compared with the rough surface.
[0017]
In addition, you may perform the process of the said invention by making the rough surface and glossy surface in a copper foil process into reverse. When the rough surface and the glossy surface are processed in reverse, the surface that was the glossy surface side of the untreated copper foil is first bonded to the resin when the copper-clad laminate is prepared.
In this way, the method of reversing the rough surface and the glossy surface has higher adhesion to the resist on the surface that is not bonded to the resin after molding with the resin than when no treatment is performed on one surface. In addition, since the adhesiveness is good, the soft etching process, which is the pretreatment, is not required in the inner layer processing process in the printed board manufacturer. Moreover, on the copper foil manufacturer side, since the surface treatment process of the copper foil is lighter than the conventional double-sided copper foil, it can be manufactured very easily.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The copper foil obtained by the surface treatment method of the present invention is applied to a copper clad laminate and used as a printed wiring board.
Hereinafter, characteristics when the embodiment of the present invention is applied to a copper clad laminate will be described.
[0019]
【Example】
(Example 1)
The rough side of untreated electrolytic copper foil with a thickness of 35 μm

In the bath of 10A / dm ² , cathodic electrolysis for 10 seconds, washed with water,

Was subjected to cathodic electrolysis at 5 A / dm ² for 80 seconds and washed with water.

Was subjected to cathodic electrolysis at 0.5 A / dm ² for 5 seconds, washed with water and dried.
The surface characteristics (uniformity, surface roughness) of this copper foil were examined. The results are shown in Table 1.
The rough surface of the copper foil was laminated on an FR-4 grade glass epoxy resin-impregnated base material as a coating surface, and pressed and molded under the conditions of 40 kgf / cm ² pressure, 170 ° C. for 60 minutes. The characteristics (adhesive strength, copper residue) of the copper-clad laminate were investigated. The results are shown in Table 1.
[0020]
(Example 2)
In Example 1, (A) Instead of bath

In the bath of 10A / dm ² , cathodic electrolysis for 8 seconds, washed with water,
Subsequently, all treatments were carried out in the same manner as in Example 1 except that cathodic electrolysis was carried out in the bath (B) of Example 1 for 5 A / dm ^{2 for} 120 seconds, and each characteristic test was performed in the same manner.
The results are shown in Table 1.
[0021]
Example 3
In Example 1, instead of (A) bath

In this bath, all treatments were performed in the same manner as in Example 1 except that cathodic electrolysis was performed at 10 A / dm ² for 10 seconds, and each characteristic test was performed in the same manner. The results are shown in Table 1.
[0022]
Example 4
In Example 1, instead of (A) bath

In this bath, all treatments were performed in the same manner as in Example 1 except that cathodic electrolysis was performed at 10 A / dm ² for 10 seconds, and each characteristic test was performed in the same manner. The results are shown in Table 1.
[0023]
(Example 5)
In Example 1, instead of (A) bath

In this bath, all treatments were performed in the same manner as in Example 1 except that cathodic electrolysis was performed at 10 A / dm ² for 10 seconds, and each characteristic test was performed in the same manner. The results are shown in Table 1.
[0024]
Example 6
In Example 1, instead of (A) bath

In this bath, all treatments were performed in the same manner as in Example 1 except that cathodic electrolysis was performed at 10 A / dm ² for 10 seconds, and each characteristic test was performed in the same manner. The results are shown in Table 1.
[0025]
[Comparative example]
(Comparative Example 1)
In Example 1, instead of (A) bath

In this bath, all treatments were performed in the same manner as in Example 1 except that cathodic electrolysis was performed at 10 A / dm ² for 10 seconds, and each characteristic test was performed in the same manner. The results are shown in Table 1.
[0026]
(Comparative Example 2)
In Comparative Example 1, the same treatment was performed except that the electrolysis time was 18 seconds in the (I) bath. In addition, each copper foil was subjected to a characteristic test in the same manner as in Example 1.
The results are shown in Table 1.
[0027]
[Table 1]

[0028]
In Table 1,
“Uniformity” is a surface shape observed with an electron microscope at a magnification of about 1000 times.
(1) Roughened particles are not coarse and the difference in size is small and uniform.
(2) Roughened particles are not coarse, but there is a slight difference in size − □
(3) Roughened particles are coarse and uneven-△
(4) Roughened particles are very coarse and non-uniform − ×
And evaluated.
“Adhesive strength” indicates the peel strength from the base material and conforms to the method described in Section 5.7 of JIS-C-6481-1986.
“Etching substrate surface residual copper” was observed with a stereomicroscope at a magnification of 50 times after removing copper by etching with cupric chloride etching.
(1) No residual copper − ○
(2) Remaining copper is observed-Evaluation was made with x.
[0029]
【The invention's effect】
From the results of Table 1 above, the surface treatment method of the present invention has higher surface shape uniformity than the conventional surface treatment method, excellent adhesion to the resin, and has the effect of reducing the surface roughness, It turns out that it is the surface-treated copper foil which was excellent.
As described above, the surface treatment method of the present invention has the following effects.
(1) A conventional surface roughening method without using toxic elements such as arsenic, selenium, and tellurium, and has no adverse effects on the environment or human body.
(2) A surface-treated copper foil with a uniform rough surface shape and high adhesion to the applied resin can be obtained, and is suitable for high-density printed wiring boards.
(3) Since this surface treatment method requires only a light surface treatment in the actual process, it is very easy to introduce and mass production is possible.

Claims (2)

At least one surface of the copper foil is subjected to cathodic electrolysis in a sulfuric acid or copper sulfate electrolytic bath containing aluminum ions and / or titanium ions at or near the limit current density, thereby depositing copper protrusions to roughen the surface. A surface treatment method for copper foil, characterized in that copper or copper alloy coating is performed thereon, followed by rust prevention treatment. The surface treatment method for a copper foil according to claim 1, wherein the aluminum ions and / or titanium ions have a concentration of 0.03 g / l to 5 g / l.