JP2574535B2 - Method for manufacturing copper polyimide substrate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to improvement of warpage of a copper polyimide substrate having a copper plating film capable of sufficiently withstanding thermal shock such as soldering.

[Prior art] Polyimide resin has excellent heat resistance,
Since it has the same electrical and chemical properties as other plastic materials, it is often used as an insulating material for electrical equipment and the like.

For example, electronic components such as a printed wiring board (PWB), a flexible printed circuit (FPC), and a tape automatic bonding (TAB) tape are obtained by processing a copper polyimide substrate provided with a copper coating on this polyimide resin. Conventional copper polyimide substrates used as materials for such PWBs, FPCs, and TABs generally employ a lamination method in which a polyimide resin and a copper foil are bonded with an adhesive. However, the substrate obtained by this laminating method does not yet have sufficient chemical resistance of the adhesive, so the ion is absorbed by the adhesive during the etching process of the copper film, and the insulating is performed when the formed circuit interval is particularly narrow. There was a risk of failure. In order to solve this drawback, a method of directly forming a metal layer on a resin has been adopted.

In this method, the surface of a polyimide resin is hydrophilized by an etching treatment, then a catalyst is applied with Pd, Ag, or the like, and then electroless plating is performed, and if necessary, electrolytic plating is performed. The substrate obtained in this way had improved thermal shock resistance and was considered to be sufficiently practical. However, the use environment of PWBs, FPCs and TAB tapes has changed drastically due to recent high density and high integration, and they have come to be used under much more severe thermal conditions than before. As a result, the thermal shock resistance of the copper polyimide substrate obtained by the above method becomes insufficient, and a copper polyimide substrate having higher thermal shock resistance has been required. In order to meet this requirement, the present inventors have proposed a method of subjecting a polyimide resin surface to electroless plating and, if necessary, electroplating, and then subjecting the substrate to a heat treatment at a temperature of 120 to 420 ° C. No. 96995. In this method, a heat-resistant, chemically-resistant altered layer formed on the surface of the polyimide resin formed by etching treatment of the surface of the polyimide resin, which is performed as a pre-treatment of the electroless plating, is thermally and chemically stable by heat treatment. In order to impart thermal shock resistance to the copper film on the surface of the polyimide resin, which can sufficiently withstand thermal shock such as soldering.

[Problems to be Solved by the Invention] A copper polyimide substrate having a copper plating film formed on a polyimide resin by a method disclosed in the above-mentioned Japanese Patent Application No. 1-96995 so as to sufficiently withstand thermal shocks such as soldering. Thus, PWB, FPC, and TAB without using an adhesive can be obtained using the copper polyimide substrate. However, the copper polyimide substrate obtained by the method has a warp, and therefore, using the copper polyimide substrate,
When FPC, TAB, etc. are manufactured by a continuous traveling type device, unevenness in resist coating thickness on the substrate or meandering at the time of substrate transfer occurs,
Defective products occur frequently, and problems such as a decrease in yield and productivity occur.

An object of the present invention is to provide a copper resin obtained by subjecting a polyimide resin surface to electroless plating of copper and, if necessary, subsequently performing electrolytic plating of copper, and then subjecting the substrate to a heat treatment at 120 to 420 ° C. An object of the present invention is to provide a copper polyimide substrate free of warpage in the polyimide substrate.

[Means for Solving the Problems] The present inventor performed electroless plating of copper on the surface of a polyimide resin, followed by electroplating of copper if necessary, and then heat-treated the substrate at 120 to 420 ° C. As a result of various studies on the cause of warpage in the copper polyimide substrate obtained by performing the above, that warpage of the substrate occurs when the substrate is heat-treated, and when a certain kind of polyimide resin is used, It has been found that the degree of warpage is reduced even if the heat treatment is performed, and the present invention has been completed based on these findings.

That is, the method of the present invention for solving the above-mentioned problem is as follows:
In a method of obtaining a copper polyimide substrate by subjecting the polyimide resin surface to electroless plating of copper, and subsequently performing electrolytic plating of copper as necessary, and then subjecting the substrate to a heat treatment at 120 to 420 ° C. 1.5 × 10 ^{-5 to} 2.0 × in the temperature range of 120 to 420 ° C. as a resin
It is characterized in that a material in the range of 10 ^-5 ° C ^-1 is used.

[Action] The present inventor has proposed that the warpage of a copper polyimide substrate be adjusted to JIS C-6481.
The substrate warpage rate was evaluated by the method, and the correlation between the substrate warpage rate and the above-described problem when FPC, TAB, and the like were manufactured using the substrate by a continuous traveling manufacturing apparatus was investigated. as a result,
If the substrate warpage ratio is 4 or more, FPC, TAB
It has been found that the above-mentioned problem does not occur even when such a device is manufactured by a continuous running type manufacturing apparatus.

In general, when a heat treatment is performed on a composite material composed of two types of substrates having different coefficients of thermal expansion, stress is generated at the substrate interface because the dimensional change rates of the respective substrates are different. Although it is known that warpage occurs in the composite material, it suggests what extent of the coefficient of thermal expansion of the polyimide substrate should be used in the production of the copper polyimide substrate which is the object of the present invention. Nothing is disclosed.

The present inventors have determined the relationship between the warp ratio of the substrate and the coefficient of thermal expansion of the polyimide resin using polyimide resins having various coefficients of thermal expansion. As a result, the coefficient of thermal expansion of the polyimide resin used in the present invention is 1.
It has been found that the warp ratio of the obtained copper polyimide substrate can be made within 4 by setting the range of 5 × 10 ^{−5 to} 2.0 × 10 ⁻⁵ ° C. ⁻¹ . Hereinafter, the present invention will be further described using examples.

[Example] The coefficient of thermal expansion was 2.1 × 10 ⁻⁵ , 2.0 × 10 ^{−5 at} 120 ° C.
1.7 × 10 ^-5 , 1.5 × 10 ^-5 , 1.4 × 10 ^-5 each ° C ^-1 , thickness 50μ
m, width 508mm, length 50m polyimide film 50
Immersed in an aqueous solution containing 1% by weight of hydrazine hydrate at 25 ° C. for 1 minute, washed with water, and then Okuno Pharmaceutical OPC-80 Catalyst M
After applying the catalyst for 5 minutes at 25 ° C. and washing sufficiently with water, an accelerating treatment was performed at 25 ° C. for 7 minutes using an OPC-555 accelerator manufactured by Okuno Pharmaceutical Co., Ltd. After performing the above pretreatment, electroless copper plating was performed under the following conditions.

(Bath _{composition) CuSO 4 · 5H 2 O:} 10g / l EDTA · 2Na: 30g / l 37% HCHO: 5ml / l PEG # 1000: 0.5g / l 2,2'- bipyridyl: 10 mg / l (Plating conditions) Temperature: 65 ° C Stirring: Air stirring Time: 10 minutes pH: 12.5 The resulting electroless copper plating films each have a thickness of 0.3μ
m.

Thereafter, the temperature was raised at a heating rate 10 ° C. / min. In vacuum 10 ^-4 torr to stand each substrate in a vacuum heating furnace, 400 ° C.
For 1 hour.

The warpage rate of each of the obtained copper polyimide substrates was determined according to JIS C-6481.
And asked for it. The results obtained are shown in Table 1.

From Table 1, the coefficient of thermal expansion at 120 ° C. is 1.5 × 10 ⁻⁵ to 2.
If FPC, TAB, etc. are manufactured by a continuous traveling type manufacturing apparatus on a copper polyimide substrate using a polyimide resin of 0 × 10 ^-5 ° C. ^-1 , non-uniform resist coating thickness or meandering at the time of substrate transfer does not occur,
It shows that yield and productivity can be improved.

[Effects of the Invention] According to the present invention, the surface of a polyimide resin is subjected to electroless plating of copper, and then, if necessary, is subjected to electrolytic plating of copper, and then the substrate is subjected to a heat treatment at 120 to 420 ° C. In the copper polyimide substrate obtained by the above, the coefficient of thermal expansion of the polyimide resin 1.
The use of the copper polyimide substrate in the range of 5 × 10 ^{-5 to} 2.0 × 10 ^-5 ° C.- ¹ enables the use of the copper polyimide substrate to produce FPC, TAB, etc. in a continuous traveling type manufacturing apparatus, resulting in unsatisfactory resist coating thickness. Uniform,
No meandering or the like occurs during the transfer of the substrate, and an improvement in yield and productivity can be expected.

Claims (1)

(57) [Claims] An electroless plating of copper is performed on the surface of a polyimide resin, followed by electroplating of copper if necessary, and then a heat treatment at 120 to 420 ° C. is performed on the substrate to form a copper polyimide substrate. In the method for obtaining a polyimide resin having a coefficient of thermal expansion of 1.5 to
A method for producing a copper polyimide substrate, characterized by using a substrate in the range of × 10 ^{-5 to} 2.0 × 10 ^-5 ° C ^-1 .