JPH0456754A - Flexible oxygen-free copper rolled foil and flexible printed board and tab tape carrier using the foil - Google Patents

Abstract

PURPOSE:To produce an oxygen-free copper foil having an excellent flexural fatigue life and the flexible printed board and TAB tape carrier using the foil by cold-rolling an oxygen-free copper material contg. a trace amt. of specified elements into an extremely thin foil. CONSTITUTION:An oxygen-free copper ingot ocntg. 10-50 ppm of one or >=2 kinds among Nb, Ti, Ni, Zr, V, Mn and Ta in total and <=50 ppm of O2 as the inevitable impurity is repeatedly hot-rolled, process-annealed and cold-rolled into a thin sheet. The thin sheet is finally cold-rolled at >=90% working rate into a copper foil having <=100 mum thickness, and a flexible oxygen-free copper rolled foil having a high flexural fatigue life is produced. When the foil is used for a flexible printed board or a tape carrier in the TAB method requiring a high flexural fatigue life, the surface is electrolytically roughned by a deposit 10a having <=2 mum thickness, and then an insulating film 12 is adhered to the surface by an adhesive 14 to produce a flexible printed board having an excellent flexural fatigue life.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an oxygen-free rolled copper foil and a flexible printed circuit board using the same, and particularly relates to an oxygen-free rolled copper foil that requires a high bending fatigue life, and a flexible printed circuit board using the same. The present invention relates to the flexible printed circuit board and TAB tape carrier used.

[Conventional technology]

Flexible printed circuit boards are currently used mainly in office automation equipment and electronic equipment such as printers and hard disk drives. This flexible printed circuit board is made by bonding copper foil onto an insulating film made of polyimide or the like via an adhesive resin such as epoxy,
It is manufactured by heating and curing under conditions of 0° C. to 170° C.×lhr to 24 hr, and then etching the copper foil to form a predetermined wiring pattern. The bonding surface of the copper foil to the insulating film is roughened by electrolytic treatment or the like to form irregularities, thereby improving the bonding strength.

By the way, in recent years, for the purpose of downsizing the device, the curvature is 10~
There is a demand for the practical use of flexible printed circuit boards that have a bending fatigue life of 101' to 109 cycles in the range of 15 cycles. Furthermore, in mounting using the TAB method, there is a demand for improvement in the flexibility of the copper foil placed on the tape carrier. In order to meet such demands, the most important point is to provide copper foil with a high bending fatigue life. This is because, in the flexible printed circuit board mentioned above, the bending fatigue life of the insulating film made of polyimide etc. is significantly longer than that of copper foil, and therefore the bending fatigue life of the entire board is determined by the bending strength of the copper foil. This is to be done.

Under these circumstances, the copper foil of conventional flexible printed circuit boards is mainly made of tough pitch copper containing 200 to 300 ppm of oxygen or oxygen-free copper (oxygen content of 3 ppm or less).

[Problem to be solved by the invention]

However, although tough pitch copper has a low softening temperature when heated and is easily softened when the adhesive resin is heated and hardened to improve flexibility, its bending strength does not meet the above requirements.

On the other hand, oxygen-free copper with an oxygen content of 3 ppm or less has a higher flexural fatigue life as a material than tough pitch copper, but
The bending fatigue properties at small curvatures of 10 to 15 degrees, which are currently strongly required, are insufficient, and the softening temperature is high, so when bonding insulation films, temperatures of 130°C to 170°C are insufficient.
It is not sufficiently softened by heating to a temperature of about °C, and improvement in flexural fatigue life due to softening cannot be expected.

Moreover, regardless of the material of each of the copper foils, there is a problem in that the bending fatigue life is reduced due to irregularities formed on the adhesive surface of the copper foils.

[Purpose of the invention]

The present invention has been made in view of the above points, and an object thereof is to provide a bending-resistant oxygen-free rolled copper foil having a high bending fatigue life, and a flexible printed circuit board and a tape carrier for TAB using the same. do.

[Means to solve the problem]

In order to achieve the above object, the present invention uses Nb, Ti.

Oxygen-free copper containing 10 ppm to 50 ppm of one or more elements among Ni, Zr + V, Mn, and Ta, and with the content of unavoidable impurities such as oxygen at 50 ppm or less, is processed at a final processing rate of 90% or more. Thickness 1 due to cold working
00 μm or less, and a roughened surface of 2 μm or less is formed on the surface to which a predetermined member is bonded, and the oxygen-free rolled copper foil is formed. Additionally, this oxygen-free rolled copper foil is used as a conductor for flexible printed circuit boards.

[Effect]

Since the present invention is configured as described above, each component (
Each condition) has the following effects.

(1) Nb, Ti+ Ni+ Zr, V+ M
n, Ta content Nb, Ti, Ni, Zr,
Since the total content of one or more elements among V, Mn+Ta is within the range of 10 pprrI to 500 ppm, the softening temperature is lowered without causing a decrease in the conductivity of the rolled copper foil. This means that the content of the above elements is 1
This is because if it is less than Qpp+n, the softening temperature is insufficiently lowered, and if it is 500 ppm or more, the added element becomes too large, causing the softening temperature to rise again and the conductivity to decrease.

(2) Content of unavoidable impurities Since the content of unavoidable impurities is set to 50 pprr1 or less, a decrease in conductivity and a decrease in flexural fatigue life after softening are suppressed. This is because the main component of the unavoidable impurity in oxygen-free rolled copper foil is oxygen, and a large amount of oxygen leads to a decrease in conductivity and also has the characteristic that the bending fatigue life after softening decreases. be.

(3) Final cold working degree By setting the final cold working degree to 90% or more, the bending fatigue life of the copper foil after softening is extended.

This means that the final degree of cold work (%) is determined by the following formula, and the bending fatigue life of the copper foil after softening based on this increases as the final degree of cold work increases. This is to improve dramatically.

(4) Surface Roughening Treatment By controlling the roughness of the roughened surface formed on one or both surfaces by electrolytic treatment to 2 μm or less, the decrease in flexural fatigue life is suppressed. This is because the finer the roughness of the roughened surface, the less the decrease in the flexural fatigue life, and in particular, there is a critical value around 2 μm.

〔Example〕

Hereinafter, the bend-resistant oxygen-free rolled copper foil of the present invention, a flexible printed circuit board using the same, and a tape carrier for TAB will be described in detail based on the following experimental data.

The first experiment measured flexural fatigue life for each alloy composition and degree of final cold work. To explain the manufacturing process of the oxygen-free copper rolled foils that will be the samples for this experiment (samples No. 091 to 0.20), oxygen-free copper containing 50 ppm or less of unavoidable impurities such as oxygen is melted using a continuous casting machine. Each of the elements shown in the following table is added to the molten metal in the form of a master alloy or a composite material of copper and additional elements to form an oxygen-free copper-based ingot with a thickness of about 200 mm and a width of about 650 mm. This ingot was hot-rolled into about 10 cylinders, and then intermediate annealing and cold rolling were repeated to give a thickness of 2 mm.
0.8 mm, 0.5 mm.

Generate 0.18mm and 0.10mm green annealed materials. In addition, as comparative materials, ordinary oxygen-free copper (sample No. 0.21) without added elements such as Nb and Ti, and tough pitch copper containing 250 ppm of oxygen (sample No.
, 22) with a thickness of 0.035 mm and a working degree of 93%.

Next, as shown in Table 1 below, the above sample was 98%, 9%
Copper foils were manufactured to a final thickness of 0.035 mm by final cold rolling at 6%, 93%, 90%, 81%, and 65%, and then heated at 160°C. Flexural fatigue life was measured after heating for 1 hour.

The bending fatigue life was measured using a testing device as shown in FIG. Here, I will briefly explain the test equipment.
A vibration transmission member 3 that transmits the vibration in the direction of the arrow is connected to the oscillation drive body 4, and the end of the sample copper foil 1 fixed to the fixing plate 2 via the screw 2a has a predetermined curvature R. It is held in place while being bent into a hairpin shape. The test conditions at this time were: sample width: 10m, curvature R: 5Wn,
Vibration stroke = 10 strokes, vibration frequency: 25 Hz, and the number of measurements under the same conditions was 6.

Table 1 From the results in Table 1 above, when the working degree is the same, the softening temperature is oxygen-free w4 (sample NO, 4, 1), which satisfies the conditions of the present invention.
0, 12, 14, 16, 18, 20), Comparative Example Tough Pitch Copper (Sample No. 22), Comparative Example Oxygen-Free Copper (Sample No. 21). It can be seen that it is getting bigger. In addition, for those whose final degree of cold working is 90% or less, the flexural fatigue life is not improved even if the alloy composition matches the present invention; It can be seen that it is improving rapidly.

Next, the second experiment of the present invention will be explained.

In this experiment, a sample of oxygen-free copper foil (containing 30 ppm of Ti) was used.

Final processing degree: 93%), Cu concentration: 20 g/f, H2SO
4100g/! Copper plating is applied to one side of the sample to form a roughened surface while changing the shape of the precipitates by changing the current density in a plating solution (liquid temperature 25°C) consisting of The relationship between flexural fatigue life and flexural fatigue life was investigated, and the results are shown in Table 2.

As is clear from the table, by reducing the current density, the roughened surface becomes finer, and the flexural fatigue life improves accordingly. Particularly excellent values were shown when the roughness was 2 μm or less.

Table 2 Next, as shown in FIG. 2, the oxygen-free rolled copper foil 10 on which precipitates 10a (precipitate height 2 μm or less) are formed on the surface by the roughening treatment is placed on an insulating film 12 made of polyimide or the like.
The adhesive material 14 such as epoxy is bonded to the top, and this is cured by heating at 130°C to 170°C for 1hr to 24hr, and then etched to form a predetermined wiring pattern to form a flexible printed circuit board. Manufactured. When we investigated the bending fatigue life of the flexible printed circuit board obtained in this way, we found that
Flexural fatigue properties similar to those shown in the table were obtained. Furthermore, when the flexural fatigue life was similarly measured with the curvature set to 10, the flexural fatigue life was improved by about two orders of magnitude compared to the case where the curvature was 50, and a life of 10' cycles or more was obtained.

In addition to flexible printed circuit boards, the oxygen-free rolled copper foil of the present invention is also effective in other uses that require a high bending fatigue life, particularly as a conductor placed on a tape carrier in mounting by the TAB method.

In addition, in the above-mentioned present example, the explanation was given for an oxygen-free rolled copper foil with a thickness of 0.035 mm, but it is also applicable to copper foil with other thicknesses as long as the thickness is 0.1 mm or less. be. In general, copper foil for flexible printed circuit boards has a thickness of 0.070 mm, 0.07 mm, 0.07 mm,
018 wn is used.

In addition, in the above example, the shape of the roughened surface was adjusted by the current density, but the shape of the roughened surface was also changed by changing the liquid temperature, Cu concentration, etc., and the roughening treatment method was also changed by using other methods than copper sulfate plating. Alternatively, a black copper oxide layer may be formed by treating with sodium chloride or the like.

〔Effect of the invention〕

As explained above, in the present invention, Nb.

Contains 10 ppm to 50 ppm of one or more elements among TI, Nil Zr, V, Mn and Ta,
Oxygen-free copper with a content of unavoidable impurities such as oxygen of 50 ppm or less is final cold worked to a thickness of 100 μm or less with a processing degree of 90% or more, and the surface to which the specified member is bonded is roughened to 2 μm or less. Since the oxygen-free rolled copper foil is formed with a surface, the bending fatigue life is significantly improved. In particular, remarkable effects can be obtained if the oxygen-free rolled copper foil is used for flexible printed circuit boards and TAB tape carriers that require a high bending fatigue life.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of an experimental apparatus according to an example. FIG. 2 is a sectional view of the flexible printed circuit board. 1-・・---m----・ 2-・ 2　a　---------・・ 3-・---1-・ 4-1--・-・- R---------・ 10a --- 1 2--1----・ 1 4-1-------・ Patent issue

Claims (3)

[Claims] (1) 10ppm to 50ppm of one or more elements among Nb, Ti, Ni, Zr, V, Mn, and Ta
Oxygen-free copper containing 50 ppm or less of unavoidable impurities such as oxygen is formed into a thickness of 100 μm or less by final cold working with a processing degree of 90% or more, and the surface to which the specified member is bonded is 2 μm or less. An oxygen-free rolled copper foil for bending resistance, characterized in that it has a roughened surface formed thereon. (2) A flexible printed circuit board formed by adhering a conductor with a predetermined wiring pattern formed on an insulating film, wherein the conductor is composed of Nb, Ti, Ni, Zr, V, Mn, and T.
10 ppm to 50 of one or more elements in a
ppm, and the content of unavoidable impurities such as oxygen is 50%.
Bending resistance made by forming oxygen-free copper with a concentration of ppm or less into a thickness of 100 μm or less by final cold working with a working degree of 90% or more, and forming a roughened surface of 2 μm or less on the adhesive surface with the insulating film. A flexible printed circuit board characterized in that it is formed from an oxygen-free rolled copper foil. (3) A TAB tape carrier formed by adhering a conductor with a predetermined lead pattern formed on an insulating tape, in which the conductor is made of Nb, Ti, Ni, Zr, V, Mn and T.
10 ppm to 50 of one or more elements in a
ppm, and the content of unavoidable impurities such as oxygen is 50%.
Bending resistance made by molding oxygen-free copper with a concentration of ppm or less to a thickness of 100 μm or less by final cold working with a working degree of 90% or more, and forming a roughened surface of 2 μm or less on the adhesive surface with the insulating tape. A tape carrier for TAB, characterized in that it is formed from a rolled oxygen-free copper foil.