JPS61204357A - Copper foil excelling in flexibility - Google Patents

Abstract

PURPOSE:To obtain copper foil exelling in flexibility and used for printed wiring boards, sheet coils, etc., by subjecting electrolytic copper foil to cold working at a specific draft and above or further to heat treatment. CONSTITUTION:The electrolytic copper foil is cold-worked >=10% draft, preferably at >=20%, or is further heat-treat to produce the desired copper foil with excellent flexibility. This copper foil is improved in defects of conventional electrolytic copper foil and rolled copper foil and it also excels in all the characteristics required of it, such as electric conductivity, mechanical strength, flexibility, accuracy of plate thickness, smoothness, and price, Accordingly this copper foil is suitably used as the one for electrical and electronic equipment and, besides, it can be inexpensively manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copper foil with excellent bending resistance used for printed wiring boards, particularly flexible printed wiring boards, sheet coils, flat cables, flexible conductors, curled cord core wires for telephones, etc. be.

Conventionally, printed wiring boards are manufactured by winding electrodeposited copper onto a rotating drum in a solution such as sulfuric acid steel. Electrolytic copper foil has been widely used.

However, in recent years, with the expansion of applications and the miniaturization of devices, high-density wiring in which wiring boards are freely folded and used within a limited space has come into widespread use. Strong enough for this flexible printed wiring board.
It is required to have excellent bending resistance and not break even after being bent many times. In addition to flexible printed wiring boards, even products that are used flat, such as precision sheet coils (laminated sheet coils and insulating materials), are made of extremely thin layers with an insulating layer of about 15 μm. Because of this, there has been a demand for plates with smooth surfaces and good thickness accuracy. In this way, the miniaturization of electrical and electronic equipment,
As precision increases, more and more custom-made copper foils are required. A summary of these custom requests is as follows.

(1) Good electrical conductivity.

(2) Excellent mechanical strength.

(3) Excellent bending resistance.

(4) Good plate thickness accuracy.

(5) The surface must be smooth.

(6) The price is low.

Although it is required to satisfy all of these properties, electrolytic copper foil has problems with strength, flexibility, and thickness accuracy9 surface smoothness, and rolled copper foil, which is made into a thin sheet by rolling,
Because it is manufactured by repeated annealing, although it has excellent properties, it is extremely expensive. Therefore, the emergence of a material that satisfies all of these requirements is eagerly awaited.

In view of this point, the present invention is directed to conventional electrolytic copper foil.

The aim is to improve the defects of rolled copper foil and to provide a material with optimal mechanical properties as various copper foils for electrical and electronic equipment.

The present invention provides a copper foil with excellent bending resistance characterized by cold working an electrolytic copper foil at a working degree of 10 seconds or more, and a heat treatment after cold working the electrolytic copper foil at a working degree of 10% or more. This is a copper foil with excellent bending resistance.

Next, the reasons for limitations regarding the constituent elements of the present invention will be described. Why cold-work electrolytic copper foil?

Although electrolytic copper foil is cheaper than rolled copper foil, it is inferior in terms of mechanical strength, bending resistance, and plate thickness accuracy9 and surface smoothness, so it is applied to compensate for these drawbacks. It is. The reason why the working degree is limited to 10- or more is that if it is less than 10-, improvements in mechanical strength, bending resistance, plate thickness accuracy, and surface smoothness are not sufficient. Preferably it is 20 inches or more. Further, the reason why heat treatment is performed after cold working is that the bending resistance can be further improved by heat treatment.

The heat treatment may be either strain relief annealing or recrystallization annealing, and is not particularly restricted.

However, from the viewpoint of bending resistance, it is preferable to perform recrystallization annealing, and in this case, the material can be made into a material that is several orders of magnitude better than conventional rolled copper foil.

The copper foil of the present invention improves the drawbacks of conventional electrolytic copper foil and rolled copper foil, and has electrical conductivity of 9, mechanical strength, bending resistance,
It exhibits excellent properties for all custom orders including plate thickness accuracy and smoothness for one price. Therefore, it is suitable as a copper foil for electrical and electronic equipment, and no prior art copper foil has such comprehensive characteristics.

The material of the present invention will be explained below with reference to Examples.

EXAMPLE Electrolytic copper foils of various thicknesses were processed by cold rolling to a final thickness of 35 μm, and copper foils with various degrees of processing were produced as shown in Table 1. Further, annealing was performed under various conditions such as strain relief annealing and annealing to reach a recrystallized state. Note that although an Ar atmosphere was used as the annealing atmosphere, it is not particularly limited. These copper foils of the present invention were compared in terms of strength and strength with conventional electrolytic copper foils, and the results are shown in Table 1.

The properties compared are tensile strength, elongation, flexibility, thickness accuracy, and maximum surface roughness. Flexibility is J-8P8115
compliant, bending angle 135°.

Bending radius Q, 8III+, M under the conditions of load 1.5 noodles,
Eng., T.

The number of times until breakage was investigated using a rolling fatigue tester. The plate thickness accuracy is 35μ by measuring the plate thickness for 100m every 1m.
We investigated how many micrometers of variation there is for the set plate thickness.

As can be seen from the results shown in Table 1, the electrolytic copper foil is inferior in all respects, but the copper foil of the present invention shows improvements in all aspects including strength, flexibility, plate thickness accuracy, and surface roughness. It has properties comparable to or better than rolled copper foil. Rolled copper foil can also be manufactured at a low price. Furthermore, among the copper foils of the present invention, those subjected to annealing such as strain relief annealing and recrystallization annealing after cold working exhibit extremely excellent flexibility.

In this way, the copper foil of the present invention has excellent electrical conductivity and strength as a copper foil used for printed wiring boards, especially flexible printed wiring boards, sheet coils, flat cables, flexible conductors, and curled cord core wires for telephones. , bending resistance, and plate thickness accuracy.

It has surface smoothness and can be manufactured at low cost.

Claims (2)

[Claims] (1) A copper foil with excellent bending resistance, which is obtained by cold working an electrolytic copper foil with a working degree of 10% or more. (2) A copper foil with excellent bending resistance, characterized in that the electrolytic copper foil is cold-worked to a working degree of 10% or more and then heat-treated.