KR20140021627A - Copper foil, copper-clad laminate, flexible circuit board, and manufacturing method for copper-clad laminate - Google Patents

Abstract

Provided are a method for producing a copper foil, a copper clad laminate, a flexible circuit board, and a copper clad laminate, which exhibit excellent durability under severe use conditions involving repeated bending with a small curvature radius even when wiring is formed in a flexible circuit board. It is a copper foil containing 0.001 mass% or more and 0.4 mass% or less and having inevitable impurities and residual Cu, or Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and A copper foil containing 0.005% by mass or more and 0.4% by mass or less of at least one element selected from the group consisting of Y and having a residual copper of 99.6% by mass or more and 99.999% by mass or less, wherein the basic crystal axis of the copper unit lattice <100> is the thickness of the copper foil A copper foil having a preferred orientation area within 15 ° of an orientation difference of 60% or more for each of two orthogonal axes in either direction and in the thin surface, and using copper clad laminates, flexible circuit boards, and copper clad laminates using the same. It is a manufacturing method of.

Description

Copper foil, copper clad laminate, flexible circuit board and manufacturing method of copper clad laminate {COPPER FOIL, COPPER-CLAD LAMINATE, FLEXIBLE CIRCUIT BOARD, AND MANUFACTURING METHOD FOR COPPER-CLAD LAMINATE}

The present invention relates to a copper foil having high durability against bending fatigue, a copper clad laminate and a flexible circuit board using the same, and a method for manufacturing a copper clad laminate, and in particular, to obtain a flexible circuit board having excellent flexibility while being durable against bending. The present invention relates to a copper foil, a copper clad laminate, and a flexible circuit board and a copper clad laminate.

Flexible circuit boards (flexible printed circuit boards) formed with wirings made of a resin layer and metal foil can be bent and used, so that movable parts in a hard disk, hinge parts of mobile phones, slide sliding parts, and printer heads can be used. It is widely used in various electronic and electrical equipment, including the parts, optical pickups, and movable parts of notebook computers. In recent years, in particular, as the size of these devices has been reduced, thinning, and high functionality, flexibility of folding flexible circuit boards in a limited space or accommodating various movements of electronic devices and the like has been required. Therefore, there is a need for improvement of mechanical properties such as better strength of the flexible circuit board so that the bending radius of the bent portion becomes smaller and the bending cycle is frequently repeated.

In general, it is the wiring side rather than the resin layer that causes defects such as the repetition of bending and the curvature of the small curvature radius, and the failure is not possible, and if it cannot endure, part of the wiring may be cracked or broken to be used as a circuit board. There will be no. Therefore, for example, in order to reduce the bending stress on the wiring in the hinge portion, the flexible circuit board (see Patent Document 1) or the hinge portion is rotated obliquely with respect to the turning axis. A method of forming a helix portion spiraled by at least one turn in the direction and increasing this number of turns to reduce the change in the diameter of the helix portion by the opening and closing operation so as to reduce damage (see Patent Document 2) or the like has been proposed. . However, in all these methods, the design of the flexible circuit board is limited.

On the other hand, the intensity (I) of the (200) plane obtained by X-ray diffraction (X-ray diffraction in the thickness direction of the copper foil) of the rolled surface of the rolled copper foil is the intensity of the (200) plane obtained by X-ray diffraction of fine powder It is reported that when I / I ₀ > 20 with respect to (I ₀ ), flexibility is excellent (refer patent documents 3 and 4). That is, since the agreement improves the flexibility of the re-crystallization sets tissue cube is developed more foil bearings, is a flexible appropriate copper foil as the wiring material for the circuit substrate defining a development view of the cube texture in the parameter (I / I ₀₎ is known . In addition, the rolled copper alloy foil obtained by containing an element such as Fe, Ni, Al, Ag, etc. at a concentration within a range dissolved in copper and annealed under a predetermined condition to recrystallize is shear deformation along the sliding surface. It is reported that it is easy and excellent in flexibility (refer patent document 5).

Moreover, although the copper foil containing the impurity, such as oxygen and silver, may be used for the flexible circuit board which requires high bending characteristic, it is 99%-99.9 mass% copper foil by purity. In the present invention, purity is expressed by mass concentration unless otherwise specified. In the test level, there is an example in which tough pitch copper of about 99.5% purity and oxygen-free copper containing no oxide are widely used as conductors of cables (see Patent Documents 3 and 4). Tough pitch copper impurities include silver, iron, sulfur, phosphorus, etc., in addition to several hundred ppm of oxygen (mostly included as copper oxide). Oxygen-free copper is usually copper with a purity of about 99.96 to 99.995%, and has significantly reduced oxygen to 10 ppm or less. In Patent Documents 3 and 4 described above, the bending fatigue characteristics of copper foils made of oxygen-free copper are superior to those of tough pitch copper foils, and are reported to be in accordance with the presence or absence of copper oxide. In addition, when the purity of these copper is further increased, it is necessary to remove impurities such as silver, phosphorus and sulfur.

Japanese Unexamined Patent Publication No. 2002-171033 Japanese Laid-Open Patent Publication No. 2002-300247 JP 2001-58203 A Japanese Patent Publication No. 3009383 Japanese Unexamined Patent Publication No. 2007-107036

Under these circumstances, the present inventors have made no restrictions on the design of the flexible circuit board, and have studied diligently to obtain a flexible circuit board with durability against bending repetition and bending with a small curvature radius. By using a highly oriented copper alloy foil, the inventors have found that a flexible circuit board having excellent bending durability and flexibility can be obtained and completed the present invention.

Therefore, the object of the present invention is excellent in durability, and when the wiring is formed in a flexible circuit board, for example, repeated bending of a small radius of curvature such as a hinge part or a slide sliding part of a mobile phone or a small electronic device is accompanied. The present invention also provides durability against severe use conditions, and provides a copper alloy foil (hereinafter sometimes referred to simply as "copper foil") having excellent bending durability.

Another object of the present invention is to provide a copper clad laminate and a flexible circuit board capable of obtaining a flexible circuit board having excellent durability and the like using the copper foil.

Another object of the present invention is to provide a method for producing a copper clad laminate suitable for obtaining a flexible circuit board having excellent durability and the like.

As a result of earnestly examining in order to solve the problem of the said prior art, it is the summary of this invention including the following structures.

(1) A copper foil containing 0.001% by mass or more and 0.4% by mass or less, and having an unavoidable impurity and residual Cu, in which the basic crystal axis of the copper unit lattice is in the thickness direction of the copper foil and in either direction A copper foil, characterized in that, for two orthogonal axes, a preferred orientation region within an orientation difference of 15 ° each occupies 60% or more in area ratio.

(2) It contains 0.001 mass% or more and 0.1 mass% or less, and contains at least any one of 0.005 mass% or more and 0.2 mass% or less of Ti, or 0.005 mass% or more and 2 mass% or less of Al. Copper foil as described in (1).

(3) Copper foil as described in (1) or (2) containing 0.06 mass% or less of Mn.

(4) 0.005% by mass or more and 0.4% by mass or less of at least one element selected from the group consisting of Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Y The balance copper is 99.6 mass% or more and 99.999 mass% or less, and the basic crystal axis of the copper unit lattice <100> is within 15 degrees of azimuth difference with respect to two orthogonal axes of either direction which exist in the thickness direction and thin surface of copper foil, respectively. Copper foil characterized by the preferential orientation area | region of occupies 60% or more by area ratio.

(5) Copper foil as described in (4) containing at least any one of 0.005 mass% or more and 0.2 mass% or less Ti or 0.005 mass% or more and 0.395 mass% or less Al.

(6) Copper foil as described in any one of (1)-(5) whose content of oxygen is less than 0.1 mass%.

(7) The copper clad laminated board which has a copper foil layer which consists of copper foil in any one of (1)-(6), and the resin layer laminated | stacked on it.

(8) The copper clad laminated board as described in (7) whose thickness of a copper foil layer is 5 micrometers or more and 18 micrometers or less, and the thickness of a resin layer is 5 micrometers or more and 75 micrometers or less.

(9) The copper clad laminated board as described in (7) or (8) in which a resin layer consists of polyimide.

(10) A flexible circuit characterized by etching a copper foil layer of the copper clad laminate according to any one of (7) to (9) to form a predetermined wiring, and forming a bent portion in at least one of the wirings. Board.

(11) The flexible circuit board according to (10), which is used to form a bend with one or more repetitive motions selected from the group consisting of sliding bend, bend bend, hinge bend and slide bend.

(12) An electronic device carrying the flexible circuit board according to (10) or (11).

(13) A method for producing a copper clad laminate having a copper foil layer and a resin layer, wherein the polyamic acid is contained on the surface of a cold-rolled copper foil containing Mn of 0.001% by mass or more and 0.1% by mass or less and having unavoidable impurities and residual Cu in its composition. The solution is applied by heat treatment or by superimposing a polyimide film to form a resin layer made of polyimide on the cold rolled copper foil, and recrystallizing the cold rolled copper foil. A method for producing a copper clad laminate, characterized in that the copper foil layer occupies 60% or more of the preferred orientation region within an orientation difference of 15 ° with respect to two orthogonal axes in one direction existing in the thickness direction and the thin surface of the copper foil, respectively. .

(14) The method for producing a copper clad laminate according to (13), wherein the cold rolled copper foil further contains at least either of 0.005% by mass or more and 0.2% by mass or less of Ti or 0.005% by mass or more and 2% by mass or less of Al.

(15) The manufacturing method of the copper clad laminated board as described in (13) or (14) in which a cold rolled copper foil contains Mn of 0.06 mass% or less.

(16) A method for producing a copper clad laminate having a copper foil layer and a resin layer, wherein at least one selected from the group consisting of Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Y A polyamic acid solution is applied to a surface of a cold-rolled copper foil containing 0.005% by mass or more and 0.4% by mass or less and having a residual copper of 99.6% by mass or more and 99.999% by mass or less, or a polyimide film is overlaid and heated. By crimping, a resin layer made of polyimide is formed on the cold rolled copper foil, and the cold rolled copper foil is recrystallized, so that the basic crystal axis of the copper unit lattice is in the thickness direction of the copper foil and in any direction in the thin surface. A method for manufacturing a copper clad laminate, characterized in that the copper foil layer occupies 60% or more of the preferred orientation region within an orientation difference of 15 ° with respect to two orthogonal axes, respectively.

(17) The manufacturing method of the copper clad laminated board as described in (16) in which cold-rolled copper foil contains at least either 0.005 mass% or more and 0.2 mass% or less of Ti, or 0.005 mass% or more and 0.395 mass% or less of Al.

(18) The manufacturing method of the copper clad laminated board in any one of (13)-(17) whose temperature which heat-processes the apply | coated polyamic-acid solution and forms a resin layer is 280 degreeC or more and 400 degrees C or less.

(19) The manufacturing method of the copper clad laminated board in any one of (13)-(17) whose temperature which thermocompresses a polyimide film and forms a resin layer is 280 degreeC or more and 400 degrees C or less.

According to the copper foil of this invention, even if wiring is formed in the bending part at the time of bending a flexible circuit board, metal fatigue hardly arises and it is excellent in stress and a distortion. As a result, the design of the flexible circuit board is not constrained, and the flexible circuit board having excellent flexibility can be obtained by providing the strength that can withstand bending repetition or bending with a small radius of curvature. , Hard disks, printers, DVD devices and the like, and highly durable electronic devices can be realized.

1 is a schematic plan view showing a relationship between a wiring made of a copper foil layer of a flexible circuit board and a ridge line of a bent portion.
2 is a cross-sectional explanatory view showing a state where a flexible circuit board is bent.
3 is an explanatory diagram of an MIT bending test apparatus.
4 (a) is an explanatory view of the IPC bending test apparatus, and FIG. 4 (b) is a sectional view taken along the line XX 'of the test flexible circuit board used in the IPC bending test.
5 is a perspective explanatory diagram of a single-sided copper clad laminate.

Hereinafter, the present invention will be described in detail.

The copper foil of the present invention is less likely to cause fatigue fracture due to cyclic load (load) or torsion, and by adopting two kinds of alloy compositions to realize such copper foil, it is difficult to produce metal fatigue, and has excellent durability against stress and torsion. Successfully obtained copper clad laminates and flexible circuit boards. The copper foil having the first alloy composition contains Mn in an amount of 0.001% by mass or more and 0.4% by mass or less, and has inevitable impurities and residual Cu, while the basic crystal axis of the copper unit lattice <100> has a thickness direction and thin surface of the copper foil. It is characterized by having a structure in which a preferred orientation region within an orientation difference of 15 ° each occupies 60% or more in area ratio with respect to two orthogonal axes in any one direction existing in the following (hereinafter, 'copper foil according to the first invention' I may say). In addition, the copper foil having the second alloy composition is 0.005% by mass of at least one or more elements selected from the group consisting of Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y. About two orthogonal axes in any one direction which contains 0.4 mass% or less, and the residual copper is 99.6 mass% or more and 99.999 mass% or less, and the basic crystal axis of a copper unit grid exists in thickness direction and thin surface of copper foil. Each of the orientation areas having an orientation difference of 15 degrees or less has a structure occupying 60% or more in area ratio, respectively (hereinafter referred to as "copper foil according to the second invention").

First, the rule on the material structure of the copper foil which concerns on 1st and 2nd invention is demonstrated.

In general, the material organization affects the fatigue properties of the material. When the structure is fine, the strength and the elongation at break are improved, but the grain boundary becomes the dislocation accumulation surface. In addition, micro stress concentration at the time of deformation | transformation by the anisotropy for every crystal grain according to the orientation of a crystal grain worsens a fatigue characteristic. In particular, the present invention provides a copper foil having excellent fatigue characteristics even in a high warp region of more than 1% of a warpage value having a curvature radius of 2 mm or less by forming a wiring of a flexible circuit board, and thus has no grain boundary in the copper foil. It is preferable that it is good, and it is highly oriented and the three basic crystal axes of copper are provided. Since the three basic crystal axes <100> are orthogonal to each other, when two of these axes are determined, all axes are determined. In other words, the preferred orientation region within the direction difference of 15 ° for the two orthogonal axes in which the basic crystal axis <100> of the copper unit lattice exists in the thickness direction of the copper foil and in the thin surface is 60% or more, preferably in the area ratio. More than 80%. In particular, it is preferable to occupy 95% or more, and more preferably 98% or more for the severe bending use in which the bending part to which curvature radius becomes 0.8 mm or less is formed.

First, since the crystal orientation at the center of the orientation is called the kitchen table of the aggregate structure, both the first and second copper foils of the present invention have a kitchen table of <100> in the thickness direction of the copper foil, and the thin surface of the copper foil < It can be said that it has a kitchen table of 100>. That is, these copper foils of the present invention have a <100> orientation in the thickness direction of the foil, and need to have an aggregate structure called a highly oriented cube orientation having a <100> orientation orthogonal thereto in the foil surface. have. The higher the degree of integration of the cubic orientation, the better the development of the aggregate structure, and the copper foil in the present invention preferably has a grain size of 800 µm or more in the thin surface, and it has a structure that penetrates in the thickness direction of the foil. desirable. Hereinafter, unless otherwise indicated, their description is common about the copper foil which concerns on 1st and 2nd invention.

Although the copper foil which concerns on 1st and 2nd invention may be either rolled foil or electrolytic foil, respectively, It is preferable that it is rolled foil preferably in the phase which obtains high orientation. In the case of copper, rolling conditions and heat treatment conditions are devised, specifically, rolling processing is carried out at a large cold work rate (final compaction rate of 90% or more), and after distortion is accumulated by work hardening, recrystallization is performed by applying heat. It is preferable. One of the copper recrystallized structures of the rolling process is a cube aggregate structure having a <100> orientation in the thickness direction of the foil and a <100> orientation in the rolling direction.

There are several indices indicating the priority of the preferential orientation of the texture, that is, the degree of orientation or the degree of integration. An indicator based on objective data using statistical data of local three-dimensional orientation data obtained by electron beam diffraction can be used. Thus, in order to define the aggregated structure in three-dimensional density, it can be specified using the area ratio of the preferential alignment region falling within 15 ° with respect to the kitchen position of the aggregated structure.

In other words, the crystal orientation of the predetermined surface of the copper foil is, for example, electron beam diffraction method such as EBSD (Electron Back Scattering Diffraction) method, ECP (Electron Channeling Pattern) method, micro-Laue method, etc. Can be confirmed by X-ray diffraction. In particular, the EBSD method analyzes crystals from diffraction images called pseudo-Kikuchi lines diffracted from the respective crystal planes generated when irradiating converging electron beams on the sample surface to be measured, and azimuth data and measurement points are analyzed. It is a method of measuring the crystal orientation distribution of a measurement object from the positional information of, and it is possible to analyze the crystal orientation of the aggregated structure in a region finer than the X-ray diffraction method. For example, in each micro-area, the orientations of the crystals can be identified and mapped to each other, and the inclination angles (direction differences) of the plane orientations between the mapping points are painted with the same color, and the surface orientations are almost the same. The orientation mapping image can be obtained by revealing the distribution of the region (crystal grains) having. It is also possible to define an orientation surface including an orientation surface having an orientation within a predetermined angle with respect to a specific surface orientation, and to define the orientation as an area ratio. Since the EBSD method yields an area ratio of a region within a certain angle from a specific orientation, in the present invention, considering the formation of wiring in the flexible circuit board, the area is larger than the region of the portion where the wiring is bent. It is desirable to scan the electron beams with a small enough score to obtain the rate and obtain the average information. In the present invention, generally, in consideration of the size of the wiring circuit formed on the flexible circuit board, a region of about 0.005 mm 2 may be selected to measure 1000 points or more in order to obtain an average area ratio.

<Copper foil which concerns on 1st invention>

Next, the provision of an alloy component is described about the copper foil which concerns on 1st invention.

In general, alloying elements improve the strength of the metal by solid solution strengthening. However, on the one hand, most of the alloying elements for copper having a face-centered cubic structure lower the stacking defect energy and make it easier to expand the potential. Therefore, dislocations hardly cause cross slip during deformation, and localization of dislocations is likely to occur locally. As a result, it also has an effect of reducing the fatigue characteristics at the time of repeated deformation. Among them, Mn is considered to have a smaller effect of reducing the copper lamination defect energy compared with other alloys. In the case of having the same structure, when Mn is contained in a copper containing no amount of Mn, copper containing Mn has an effect of increasing the elongation at break when tensile stress is applied in one direction in the thin surface. That is, even if an alloy component is added, copper alloy foil having a crystal structure of a face-centered cubic system having a high elongation at break while having a high orientation can be realized, and improving fatigue characteristics when repeated tensile stress or distortion is applied in one direction in the thin surface. Could know.

Then, as a result of this inventor's examination about content of Mn in copper foil, when content of Mn expresses the effect in 0.001 mass% or more, it found that especially when it contains 0.005 mass% or more, the effect becomes large. In addition, the upper limit is prescribed | regulated as 0.4 mass% for the following reasons.

As described above, the copper foil according to the first aspect of the present invention has a preferred orientation within 15 ° of azimuth difference with respect to two orthogonal axes in one direction in which the basic crystal axis of the copper unit lattice <100> exists in the thickness direction of the copper foil and in the foil surface, respectively. The area has an organization that accounts for more than 60% of the area. As a powerful means for obtaining such a structure, a method of forming a recrystallized texture structure in which the <100> orientation is highly oriented in the thickness direction and the rolling direction of the foil can be employed by heat-treating the copper foil processed by rolling. At that time, if the concentration of the alloying element is increased, the recrystallization temperature increases. The extent depends on the species. In addition, recrystallization occurs depending on the component species and concentration, but no recrystallization structure or cube aggregate structure is formed.

When Mn is the addition amount within the range prescribed | regulated with the copper foil which concerns on 1st invention, a cubic aggregate structure is obtained, but when content increases, recrystallization temperature rises and it contains in quantity exceeding 0.4 mass%, for example, 500 Even if it heat-processes in degreeC, formation of a strong cube orientation becomes difficult. This heat treatment at 500 ° C. or more easily oxidizes under simple atmosphere control, and requires a very small oxygen concentration to perform heat treatment. When continuous heat treatment such as roll-to-roll is performed, a large-scale facility is required. Will grow. Therefore, in the copper foil which concerns on 1st invention, the upper limit of content of Mn was prescribed | regulated as content of the upper limit in which the aggregate structure of the prescription | regulation referred to in this invention cannot be obtained by heat processing of 500 degreeC and 1 hour.

Moreover, this invention makes the main objective to provide the copper foil for flexible circuit boards. Therefore, the copper foil can also be recrystallized by using the thermal history during the manufacturing process of the flexible circuit board, which is advantageous in terms of cost. Of course, after forming the recrystallized texture by heat-processing the previously hardened copper foil and forming a recrystallized texture, forming a resin layer in the hardened copper foil is also easier in handling. There are various methods of manufacturing a flexible circuit board, such as a cast method, a hot press method, a laminate method, etc. Among them, a polyamic acid solution is applied by a cast method and heat treated to form a resin layer made of polyimide. Even if the temperature is high, it is 400 degreeC. Moreover, when superimposing a polyimide film and thermocompressing and forming a resin layer on copper foil, the temperature of the thermocompression bonding is generally about 300-400 degreeC. Therefore, since it is preferable to complete recrystallization at the temperature in these heat processing or thermocompression bonding, it is more preferable that Mn concentration in the composition of cold rolled copper foil does not exceed 0.1 mass%. In addition, since the heat treatment time becomes short when it is going to manufacture this continuously, the Mn density | concentration of industrial copper foil for flexible circuit boards is 0.06 mass% or less in terms of handling, and the annealing process of copper foil before the lamination process of copper foil and polyimide. It is more preferable at the point which can omit.

On the other hand, the electrical resistance value of copper is about 1.7x10 <^-8> m at room temperature. When used for a flexible circuit board, the copper foil forming the wiring is preferably used for the transmission of signals or power, and therefore, the electrical resistance is preferably lower. If the Mn concentration is added in excess of 0.1% by mass, the electrical resistance at room temperature exceeds 2.0 × 10 ⁻⁸ mm and the IACS is less than 85%. In this respect, the Mn concentration does not exceed 0.1% by mass. desirable. Moreover, since Mn density | concentration is 0.06 mass% or less, since an electric resistance value floats and becomes 1.9 * 10 <^-8> mV or less, it is more preferable.

Moreover, about the case where the content of Mn is suppressed to 0.1 mass% or less as mentioned above, in the copper foil which concerns on 1st invention, while 0.001 mass% or more and 0.1 mass% or less contain Mn, 0.005 mass% or more and 0.2 mass% At least one of the following Ti or 0.005 mass% or more and 2 mass% or less Al may be contained, and you may have an unavoidable impurity and remainder Cu. By using copper foil of such a composition, break elongation can be improved further and a fatigue characteristic can be improved. By adding Ti or Al in the said range, especially the small amount of Mn addition amount of 0.001 mass% or more and 0.005 mass% or less can obtain a big effect regarding durability.

Here, the upper limit of Ti content is prescribed | regulated by recrystallization temperature similarly to Mn. Ti has a function of increasing the recrystallization temperature more than Mn, so that the aggregate structure of the regulation as described in the present invention cannot be obtained by heat treatment at 500 ° C. for 1 hour. Specifically, the upper limit of Ti content is 0.2% by mass. Moreover, it is preferable to complete recrystallization preferably at 400 degrees C or less, and it is preferable that the upper limit of content of Ti in that case is 0.05 mass%.

On the other hand, Al has a small effect of raising the copper recrystallization temperature, and can be added in principle up to 9 mass%, which is the maximum solid solubility limit of Al to copper. However, when Al is added in excess of 2 mass%, the CuAl compound phase It becomes easy to form. When this compound phase is formed, when a distortion is applied, a stress concentrates in the vicinity of the CuAl compound in copper foil, and a fatigue characteristic falls remarkably.

The copper foil according to the first invention contains inevitable impurities in addition to Mn, Ti, and Al. In particular, silver, iron, and nickel contained as impurity elements in the raw copper do not affect the effects disclosed in the present invention. However, when oxygen contains a large amount of oxygen as copper oxide, stress concentration occurs on copper oxide when stress is applied to the copper foil. Therefore, the oxygen content should not exceed 0.1 mass% at most, and preferably It is preferable that it is 0.05 mass% or less which is the level contained in tough pitch copper, More preferably, it is 0.001 mass% or less which is the oxygen impurity concentration level of an oxygen free copper.

<Copper foil which concerns on 2nd invention>

Moreover, the prescription | regulation of the alloy component of the copper foil which concerns on 2nd invention is described.

In order for copper foil to be highly oriented, it is preferable to form a cube orientation which is a recrystallized texture by accumulating distortion by cold rolling, heating and recrystallization. As described above, the alloying element may inhibit the formation of the cube orientation after recrystallization, among which Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y Promotes the formation of a cube bearing. In the case of heating under the same heat treatment conditions, Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Y may be In comparison, when the alloying element is contained, it is considered that the degree of integration of the copper cube orientation is increased. Moreover, an alloying element improves strength by solid solution strengthening. However, on the one hand, most alloying elements for copper having a face centered cubic structure lower the stacking defect energy and make it easier to expand the dislocation. As a result, dislocations are less likely to cause cross slip during deformation, and accumulation of dislocations is likely to occur locally. As a result, it also has an effect of reducing the fatigue characteristics at the time of repeated deformation. Among them, Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y have a smaller effect of reducing copper stacking defect energy than other alloys, It also found a small effect on reducing fatigue properties.

The content of one or more alloying elements selected from the group consisting of Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Y expresses the effect with a small amount of addition. Especially when it contains 0.005 mass% or more, an effect becomes large. Moreover, when these elements are added exceeding 0.4 mass% in total amount, the integration degree of a cube orientation will become small on the contrary. In the case where these elements are not dissolved in copper, twisting the copper foil causes stress concentrations in the vicinity of the precipitated phase, and this causes a breakdown point, so that the maximum solid solution limit of the alloying element is more than 0.4% by mass. If it is small, it is preferable not to exceed it.

Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y defined in the copper foil according to the second invention are similar in chemical properties, and all have a <100> orientation. There is an action to improve. Therefore, these elements may be contained in mixture of 2 or more types of elements. Among them, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y are rare earth elements, and many of them are expensive and expensive to classify each element. The metal before refining and separating these elements is called misch metal, and is a mixture containing Ce, La, Pr, and Nd as a main component, and is relatively inexpensive. Since all the metals contained in the micrometal have the same effect, it is effective for cost reduction by adding as a micrometal.

Although it demonstrated also in the copper foil which concerns on 1st invention, this invention aims at providing the copper foil for flexible circuit boards. Therefore, the copper foil can be recrystallized using the thermal history during the manufacturing process of the copper clad laminate or the flexible circuit board, which is advantageous in terms of cost. Of course, you may make it obtain the copper clad laminated board after heat-processing the previously hardened copper foil to form a recrystallized texture, but it is also easy to form a resin layer in the workpiece hardened copper foil from a handling surface. There are various methods of manufacturing a copper clad laminate, such as a cast method, a hot press method, and a lamination method. Although the temperature at which the resin layer is formed is high, it is about 400 ° C, and it is preferable to complete the recrystallization of the copper foil according to the second invention at this temperature. Do.

About the copper foil which concerns on 2nd invention, the element of that excepting the above may be included as an unavoidable impurity. In particular, if Al, Ti, Ag, Fe, Ni, Mn, Hf, Ta, B or V is within the purity (copper content) of the copper foil specified by the copper foil according to the second invention, the effect of the present invention is maintained. Among these elements, Al and Ti are combined by one or more elements selected from the group consisting of Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Y, in detail. By containing at least either of 0.005 mass% or more and 0.2 mass% or less Ti or 0.005 mass% or more and 0.395 mass% or less Al. It has the effect | action which improves the <100> orientation degree when recrystallizing copper foil on the same conditions. In addition, although Mg is similar in chemical properties to the element group prescribed | regulated by the copper foil which concerns on 2nd invention among inevitable impurities, since it reduces <100> orientation degree, it is preferable that the content is 0.001 mass% or less.

In addition, among the unavoidable impurities, when oxygen contains a large amount of oxygen as copper oxide, stress concentration occurs on copper oxide when stress is applied to the copper foil, so the content of oxygen does not need to exceed 0.1 mass% at the maximum. Preferably it is 0.05 mass% which is the level contained with general tough pitch copper, More preferably, it is preferable that it is 0.001 mass% or less which is the oxygen impurity concentration level of an oxygen free copper. In addition, sulfur has a high affinity with copper and is easy to accept as an impurity. However, the smaller the content, the better the copper content. Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Y which are the elements defined in the copper foil which concerns on 2nd invention, and Al and Ti added as needed are oxygen, respectively. In addition, it has a high affinity with sulfur and has a secondary effect of forming oxygen and sulfur and compounds that are harmful to bending fatigue characteristics when dissolving and alloying copper to release oxygen or sulfur out of the material. Therefore, it is preferable to add the alloying element added as mentioned above in consideration of the quantity removed as a compound according to content of oxygen and sulfur in a copper raw material.

As described above, the content of Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Y, Al and Ti in the copper foil according to the second invention is determined by the cast method, The heat treatment temperature for forming a copper-clad laminate by forming a resin layer by a hot press method, a lamination method, or the like is defined as a condition that a preferred <100> alignment region with sufficient copper foil can be obtained, and when the heat history applied to the copper foil is the same, The effect of improving the degree of integration of the <100> cube orientation by the above elements can be obtained.

Copper Clad Laminates, Flexible Circuit Boards

By using the copper foil which concerns on 1st invention mentioned above, or the copper foil which concerns on 2nd invention, in this invention, a resin layer is laminated | stacked on the copper foil layer which consists of either copper foil, and it is set as a copper clad laminated board, and the copper foil layer of this copper clad laminated board is etched, By forming the predetermined wiring, a flexible circuit board having excellent bending durability and flexibility can be obtained. It is suitable to form and use a bent portion at least at one place of the wiring of the flexible circuit board, and particularly has excellent fatigue characteristics even in a high torsion region where the radius of curvature of the bent portion is 2 mm or less. In order to achieve this object, in this invention, it is preferable that copper foil has a structure and component value prescribed | regulated by the 1st or 2nd invention, and it is preferable that it is a structure shown below. In addition, the following content is common to the copper foil which concerns on 1st and 2nd invention, and the case where either copper foil is used is called the copper clad laminated board and flexible circuit board which concern on this invention.

That is, in the present invention, when particularly high flexibility is required, the copper foil for forming the wiring of the flexible circuit board is preferably a rolled copper foil having a thickness of 5 to 18 µm, preferably a rolled copper foil having a thickness of 9 to 12 µm. It is good to use. When the rolled copper foil is thicker than 18 µm, it becomes difficult to obtain a flexible circuit board having excellent fatigue characteristics in a high warping region having a radius of curvature of 2 mm or less. Moreover, when thickness becomes thinner than 5 micrometers, handling in laminating | stacking copper foil and a resin layer is difficult, and it is difficult to form a homogeneous copper clad laminated board. As described above, when the copper foil layer is formed of a rolled copper foil, the rolled copper foil is heat-treated in advance so that the basic crystal axes of the copper unit lattice are in two directions in the thickness direction of the copper foil and in the thin surface. Recrystallized so as to occupy 60% or more of the preferred orientation area within 15 degrees of the orientation difference with respect to the orthogonal axis, respectively, or cold-rolled in the above thickness range to form a resin layer by a cast method, a laminate method, or the like. The crystallization may be performed by the thermal history of.

Although the kind of resin which forms a resin layer is not specifically limited about the resin layer of the copper clad laminated board in this invention, For example, polyimide, polyamide, polyester, a liquid crystal polymer, polyphenylene sulfide, polyether ether ketone Etc. can be illustrated. Among them, polyimides and liquid crystal polymers are preferable in that they exhibit good flexibility and excellent heat resistance when the circuit board is used.

Although the thickness of a resin layer can be suitably set according to the use, shape, etc. of a copper clad laminated board, it is preferable that it is the range of 5-75 micrometers from a viewpoint of flexibility, The range of 9-50 micrometers is more preferable, The range of 10-30 micrometers Most preferred. If the thickness of the resin layer is less than 5 μm, the insulation reliability may be deteriorated. On the contrary, if the thickness of the resin layer is more than 75 μm, the thickness of the entire circuit board may be too thick when mounted on a small device or the like as a flexible circuit board. The fall of flexibility is also conceivable.

In addition, in the case where it is mounted in a small apparatus etc. as a flexible circuit board, the cover material as shown below may be formed on the wiring formed from the copper foil layer in some cases. In that case, it is good to design the structure of a cover material and a resin layer in consideration of the balance of the stress applied to wiring. According to the findings of the present inventors, for example, if the polyimide resin forming the resin layer has a tensile modulus of 4 to 6 GPa at 25 ° C and a thickness of 14 to 17 µm, the cover member to be used has a thickness of 8 to 17 µm. It is preferable to have two layers of an adhesive layer made of a thermosetting resin and a polyimide layer having a thickness of 7 to 13 µm, and the tensile modulus of the adhesive layer and the entire polyimide layer to be 2 to 4 GPa. If the polyimide forming the resin layer has a tensile modulus of 6 to 8 GPa at 25 ° C and a thickness of 12 to 15 µm, the cover member to be used has an adhesive layer and a thickness composed of a thermosetting resin having a thickness of 8 to 17 µm. It is preferable that it has two layers of the polyimide layer of 7-13 micrometers, and that the tensile elasticity modulus of an adhesive layer and the whole polyimide layer becomes 2-4GPa.

As for the means for laminating the resin layer and the copper foil layer, for example, when the resin layer is made of polyimide, the copper foil may be thermally laminated by applying or interposing a thermoplastic polyimide to the polyimide film (so-called lamination method). Examples of the polyimide film used in the laminating method include "Kapton" (Torre Dupont Co., Ltd.), "Apical" (Kaneka Co., Ltd.) and "UPILEX". (Ubekosan Co., Ltd.) etc. can be illustrated. When heat-pressing a polyimide film and copper foil, it is good to interpose the thermoplastic polyimide resin which shows thermoplasticity. When forming a resin layer by thermocompression-bonding a polyimide film by such a lamination method, it is preferable that the temperature of the thermocompression bonding is 280 degreeC or more and 400 degrees C or less, Preferably it is 300 degreeC or more and 400 degrees C or less.

On the other hand, it is also possible to apply a polyimide precursor solution (also called a polyamic acid solution) to copper foil, and to dry and harden | cure it, and to form a laminated body from a viewpoint which is easy to control the thickness, bending characteristics, etc. of a resin layer. Cast method). In such a casting method, the temperature of the heat treatment for imidating the polyimide precursor solution to form a resin layer is preferably 280 ° C or more and 400 ° C or less, preferably 300 ° C or more and 400 ° C or less.

The resin layer may be formed by laminating a plurality of resins, and for example, two or more types of polyimides having different linear expansion coefficients or the like may be laminated. In this case, an epoxy resin or the like is used as an adhesive from the viewpoint of ensuring heat resistance and flexibility. It is preferable that the entire resin layer is substantially formed of polyimide. Including the case which consists of a single polyimide, and the case which consists of a some polyimide, it is good to set the tensile elasticity modulus of 4-10 GPa, Preferably it is 5-8 GPa.

In the copper clad laminated board of this invention, it is preferable to make the linear expansion coefficient of a resin layer become the range of 10-30 ppm / degreeC. What is necessary is just to make the linear expansion coefficient of the whole resin layer into this range, when a resin layer consists of several resin. In order to satisfy these conditions, for example, a low linear expansion polyimide (low thermal expansion polyimide) layer having a linear expansion coefficient of 25 ppm / 占 폚 or lower, preferably 5-20 ppm / 占 폚, and a linear expansion coefficient of 26 ppm / 占 폚 or higher. Preferably, it is a resin layer which consists of a 30-80 ppm / degree high linearly expandable polyimide (high thermally expansible polyimide) layer, and it can be set to 10-30 ppm / degreeC by adjusting these thickness ratios. The ratio of the thickness of a preferable low linear expansion polyimide layer and a high linear expansion polyimide layer is 70: 30-95: 5. Moreover, it is preferable to provide so that a low linearly expandable polyimide layer may become a main resin layer of a resin layer, and a high linearly expandable polyimide layer may contact copper foil. In addition, the coefficient of linear expansion was obtained by using a polyimide in which the imidation reaction was sufficiently completed, as a sample, and after heating up to 250 ° C. using a thermomechanical analyzer (TMA), cooling at a rate of 10 ° C./min, and 240 to 240 ° C. It can obtain | require from the average linear expansion coefficient in the range of 100 degreeC.

Moreover, the flexible circuit board obtained by the copper clad laminated board in this invention is equipped with the wiring formed from the resin layer and the copper foil layer, and is used with a bent part anywhere. That is, it is widely used in various electronic and electrical devices, including the movable part in the hard disk, the hinge part or slide sliding part of the mobile phone, the head part of the printer, the optical pickup part, the movable part of the notebook, and the like, and the circuit board itself is bent or twisted, Or it is deformed according to the operation | movement of the mounted apparatus, and the bending part is formed in any one place. In particular, since the flexible circuit board of the present invention has a bent structure having excellent bending durability, it is frequently bent with repeated operations such as sliding bending, bending bending (including joint bending), hinge bending, slide bending, or the like. Or in order to cope with the miniaturization of the equipment to be mounted, the curvature radius is 0.38 to 2.0 mm in bending behavior, 1.25 to 2.0 mm in sliding bending, 3.0 to 5.0 mm in hinge bending, and 0.3 to 2.0 mm in slide bending. It is suitable in the case of a condition, and it is especially effective in the slide application which requires severe bending | flexion performance in a narrow gap of 0.3-1 mm, especially the severe bending use | formation in which the bending part which curvature radius becomes 0.8 mm or less is formed.

There is no restriction | limiting in particular about the width | variety, a shape, a pattern, etc. of wiring, What is necessary is just to design suitably according to the use of a flexible circuit board, the electronic device mounted, etc. Fig. 1 shows a flexible circuit board for use in a hinge part of a cellular phone, for example, and is an example having a resin layer 1 and a wiring 2 formed of copper foil and a connector terminal 3. The schematic diagram at the time of bending the flexible circuit board of FIG. 1 to U shape so that a ridge line L may arise is shown in FIG. As shown in Fig. 2, when the flexible circuit board is bent in a U-shape, for example, a ridge line L is formed on its outer side (opposite to the side on which an inscribed circle having a radius of curvature is formed). This ridge line L shown in FIGS. 1A, 1B, and 2 shows α ° with respect to the [100] axial direction of the preferential alignment region of the copper foil forming the copper wiring 2. Has an angle. Here, FIG. 1 (a) shows an example in which wiring is obliquely formed near the ridge line L in the middle of the connector terminal 3 at both ends. As shown in FIG. It is also possible. Moreover, in addition to the case where the position of the ridge line L in the bend is fixed, such as a folding cell phone, the slide sliding bend in which the ridge line L is bent in the bent portion, such as a slide type mobile phone, is described in Fig. 1 (b). One thick line arrow direction). Moreover, although the flexible circuit board in this invention is equipped with the wiring which consists of copper foil on at least one side of a resin layer, you may make it provide copper foil on both surfaces of a resin layer as needed.

As shown in FIG. 1, the wiring 2 formed from the copper foil in the flexible circuit board of this invention may face in any direction. α ° can take any angle. That is, in the flexible circuit board of the present invention, one <100> axis of the preferential alignment region in the copper wiring is the thickness direction of the copper foil and is perpendicular to the resin layer 1, but two <100> The axis may face in any direction within the copper wiring surface. When the fatigue test is performed by bending the U-shaped shape so as to form the ridge line L with respect to the flexible circuit board shown in FIG. 1, FIG. 1 (c) in which the principal stress at the time of bending coincides with FIG. ) And FIG. 1 (d) are the harshest directions. This is for the following reason.

When bent in a U shape to form a ridge line L with respect to the flexible circuit board, the main stress applied to the copper circuit depends on the configuration of the flexible circuit board. The cut is a tensile or compressive stress that is perpendicular to the cross section. If the cross-sectional orientation of the wiring when cut in the thickness direction from the ridge at the bend is set to (100), the Schmid's factor of eight slip surfaces becomes equivalent when curved, and eight slip systems At the same time, dislocations tend to accumulate locally. As shown to Fig.1 (a) and (b), when the angle of [100] axis | shaft and ridgeline L is made into an angle other than 90 degrees, the Schmid factor is also among the eight {111} which is the sliding surface of copper foil. Since the largest main sliding surface becomes four sides, the shear slip becomes good and local work hardening hardly occurs.

In the known rolled copper foil conventionally used, the longitudinal direction of the copper foil corresponds to the rolling direction, and as shown in Figs. 1 (c) and (d), it is common to form a circuit along the kitchen table. . And when a circuit is formed in such a direction using the conventional copper foil, a problem arises in durability, and even in this case, it is hard to fracture | rupture with respect to repeated bending. Of course, when copper foil wiring is formed as shown to Fig.1 (a) and (b), it becomes a flexible circuit board with a higher bending fatigue characteristic.

As described above, the copper foil of the present invention is highly oriented and contains a prescribed alloy component, which hardly causes metal fatigue, and has excellent durability against stress and distortion. Moreover, the flexible circuit board obtained by forming a copper clad laminated board using such copper foil, etching the copper foil by a well-known method, and forming a wiring has the strength which can endure the repetition of bending and the bending with small curvature radius. In addition, since it is excellent in bendability, the design of a flexible circuit board, such as taking into account the shape of the wiring in the bent portion, does not occur.

Example

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated further more concretely based on an Example and a comparative example. The following shows examples of the present invention, and the present invention is not limited by these at all. In the present Example, copper foils having various alloying elements were fabricated, copper foil structure was analyzed from the test single-sided copper clad laminate obtained using the same, and a test flexible circuit board was manufactured from the test single-sided copper clad laminate to measure flexural fatigue characteristics. .

Example 1

In the present Example, copper foil containing Mn as an alloying element was produced, the elongation at break was measured from the test single-sided copper clad laminate using the same, and the test flexible circuit board was manufactured from the test single-sided copper clad laminate to measure the bending fatigue characteristics. .

The copper foil which concerns on sample numbers 1-16 used in the present Example was manufactured as follows. Oxygen-free copper having a purity of 99.99% and an oxygen content of 0.0008% and Mn having a purity of 99.9% weighed in a predetermined amount as shown in Table 1 are dissolved in an argon atmosphere in a graphite crucible and stirred, and a width of 50 mm and a length of 100 mm, An ingot was produced by pouring into a rectangular graphite mold having a thickness of 15 mm. Next, width rolling was performed to make thickness 10mm in the width direction, and hot rolling was performed at the maximum 600 degreeC, and further hot rolling was performed to the thickness of 2 mm on the same conditions in the longitudinal direction. Then, cold rolling was performed until it became 9 micrometers in thickness. In the meantime, both ends were cut by the slit process in the place where thickness was 0.5 mm, and the width was adjusted to 60 mm. Therefore, the obtained copper foil was 60 mm in width and 9 micrometers in thickness.

Thereafter, some copper foil was subjected to recrystallization heat treatment at 500 ° C. for 1 hour in a vacuum furnace. When the density | concentration of Mn of the both ends of the obtained copper foil and the center part was chemically analyzed, it confirmed that there was almost no density variation on the case also about the copper foil which was not performed even about the copper foil which performed the recrystallization heat treatment.

Moreover, the polyamic-acid solution which is a precursor of the polyimide which comprises the resin layer of the test flexible circuit board which concerns on Example 1 was synthesize | combined two types by the following method.

(Synthesis Example 1)

N, N-dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) was dissolved in the reaction vessel while stirring in the vessel. Next, pyromellitic dianhydride (PMDA) was added. It injected | threw-in so that the total amount of monomer may be 15 mass%. Thereafter, stirring was continued for 3 hours to obtain a resin solution of polyamic acid a. The solution viscosity of this resin solution of polyamic acid a was 3,000 cps.

(Synthesis Example 2)

N, N-dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 2,2'-dimethyl-4,4'- diaminobiphenyl (m-TB) was put into this reaction container. Next, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) were added. The total amount of monomers was 15% by mass, and the molar ratio (BPDA: PMDA) of each acid anhydride was added at 20:80. Thereafter, stirring was continued for 3 hours to obtain a resin solution of polyamic acid b. The solution viscosity of this resin solution of polyamic acid b was 20,000 cps.

Next, the formation method of the copper clad laminated board which is a composite of copper foil and a polyimide is demonstrated.

The polyamic acid solution a prepared as described above was applied to the surface of the copper foil according to Sample Nos. 1 to 16 prepared above, and dried (after curing, a thermoplastic polyimide having a thickness of 2 μm was formed). Apply and dry (after curing to form a low thermally expandable polyimide having a thickness of 9 μm) and apply polyamic acid a thereon to dry (after curing, form a thermoplastic polyimide having a thickness of 2 μm), The resin layer which consists of polyimide of three-layered structure was formed through the heat processing by the heating condition whose temperature is set to 400 degreeC, and the integration time in the 360-400 degreeC temperature range becomes 5 minutes.

Subsequently, it cuts out so that it may become rectangular size of width 40mm in length 250mm and the direction orthogonal to a rolling direction (TD direction) along the rolling direction (MD direction) of copper foil, and the resin layer (polyimide) of 13 micrometers in thickness (1 ) And a single-sided copper clad laminate for testing having a copper foil layer 2 having a thickness of 9 μm (FIG. 5). The tensile elasticity modulus of the whole resin layer at that time was 7.5 GPa.

Break elongation and structure analysis were performed about the copper foil (copper foil layer) in the single-sided copper clad laminated board for a test obtained above.

The breaking elongation of copper foil cut | disconnected the sample cut out to width 10mm in the direction orthogonal to this rolling direction in length 150mm in the rolling direction of copper foil obtained by chemically removing the resin layer which consists of polyimide of the single-sided copper clad laminated board for a test. It used and measured by the distance of 100 mm and the tensile speed of 10 mm / min in the longitudinal direction. For the measurement, seven samples were prepared for each type of copper foil, and the average value of the elongation at break was determined.

 The structure of the copper foil was obtained by performing azimuth analysis with an EBSD apparatus after mechanically and chemically polishing the colloidal silica on the rolled surface of each copper foil. The apparatus used was FE-SEM (S-4100) manufactured by Hitachi Seisakusho, and EBSD device and software (OIM Analysis 5.2) manufactured by TSL. The measurement area was an area of about 800 mu m x 1600 mu m, and the acceleration voltage was 20 kV and the measurement step interval was 4 mu m. That is, the measurement score is 80000 points. The degree of integration of the cube texture of the present invention, i.e., the <100> preferred orientation region, is a ratio with respect to the measuring point of the whole measuring point where <100> is within 15 ° for both the thickness direction of the foil and the rolling direction of the foil. Can be represented. The number of measurements was carried out on five different samples of each cultivar individual, and rounded off to the nearest decimal point. Moreover, the crystal grain diameter was evaluated using the obtained data as a crystal grain boundary that the orientation difference of adjacent crystal grains is 15 degrees or more.

Next, a predetermined mask was put on the copper foil layer side of the single-sided copper clad laminate for test obtained above, and etching was performed using an iron chloride / copper chloride solution, and the wiring direction of the linear wiring having a line width l of 150 µm was rolled. The wiring pattern was formed so that space width s might be 250 micrometers, making it parallel to a direction. And a flexible test circuit having a width of 150 mm in the longitudinal direction along the wiring direction (H) of the circuit board and a width of 40 mm in the direction orthogonal to the wiring direction (H) in accordance with JIS 6471 to serve as a sample for bending test described later. A substrate was obtained. It was confirmed that there was no change in the structure of the copper foil before and after the circuit formation by etching.

Using the test flexible circuit board obtained above, the MIT bending test was done according to JIS C5016. The schematic diagram of a test is shown in FIG. The device is a product of TOYO Seiki Seisakusho (STROGRAPH-R1), and one end in the longitudinal direction of the test flexible circuit board is fixed to the nip jig of the bending test apparatus, and the other end is fixed by weight to the nip part ( The nip portion is bent to a radius of curvature of 0.8 mm while being rotated 135 ± 5 degrees alternately left and right under the condition of the vibration speed of 150 times / min, and the number of times until the conduction of the wiring of the circuit board is interrupted. It calculated | required as the number of bending.

Under this test condition, since the ridge lines formed in the bent portion are bent so as to be perpendicular to the wiring direction H of the wiring of the test flexible circuit board, the main stress and major distortion applied to the copper circuit are in the rolling direction. Parallel tensile stress, tensile distortion. When the circuit was observed from the thickness direction of the copper foil after the bending test, it was confirmed that the crack was broken in the vicinity of the ridge line of the bent portion almost perpendicular to the rolling direction.

Table 1 shows the amount of Mn in the copper foil obtained by the test described above, the elongation at break of the copper foil, the <100> preferred orientation area ratio, and the bending life. Flexural life is an average of the result of the test flexible circuit board which prepared five pieces for each kind of copper foil.

 From Table 1, it can be seen that the high bending resistance property of more than 2000 fatigue lifes is obtained when the Mn concentration is 0.001% by mass or more and 0.4% by mass or less and the area ratio of the <100> preferred alignment region is 60% or more. At concentrations of 0.02 mass% or less, a cube aggregate having a very high degree of integration was obtained regardless of the presence or absence of recrystallization heat treatment at 500 ° C. for 1 hour. In this range, no significant difference was observed in the degree of integration, and as the Mn concentration increased, the fatigue life increased, and particularly good bending resistance was obtained at 0.005% by mass or more. This is because the addition of Mn increases the elongation at break in the longitudinal direction of the wiring, that is, the rolling direction, which is the main stress direction during bending. In the sample having a Mn concentration of 0.001% by mass or more, crystal grains having a cube orientation developed to a size of 800 µm or more in the copper foil surface, and it was found that they penetrated in the thickness direction of the foil.

Comparing the samples of Sample Nos. 11 and 12 having an Mn concentration of 0.1% by mass, the bending resistance of the Sample No. 11 was relatively high, but the number of samples until the fracture of the Sample No. 12 was small. This is because the copper foil of the sample of Sample No. 11 was subjected to recrystallization heat treatment at 500 ° C. for 1 hour, so that recrystallization proceeded and the area ratio of the <100> first alignment region was relatively large. In the sample having a Mn concentration of 0.42% by mass or more, even though recrystallization heat treatment was performed before forming the flexible circuit board, the area ratio of the <100> first alignment region became 60% or less, and the number of bendings until breakage was obtained. Also greatly degraded. This is because the recrystallization temperature was increased by the excessive addition of Mn.

The formation time of the polyimide in this Example is 5 minutes, and this is a test simulating the continuous production of roll-to-roll. Comparing the sample which was not subjected to recrystallization heat treatment at 500 ° C. for 1 hour in advance, the bending life was increased when the Mn concentration was 0.005% by mass or more and 0.06% by mass or less. That is, the copper foil of this density | concentration range is especially suitable as copper foil used when obtaining the polyimide-type flexible circuit board provided with the resin layer which consists of polyimides.

[Example 2]

In this embodiment, a copper foil containing Mn, Ti, and Al as an alloying element is produced, and the elongation at break is measured from the test single-sided copper clad laminate using the same, and a test flexible circuit board is manufactured from the test single-sided copper clad laminate to flexure fatigue characteristics. Was measured.

The copper foil concerning sample numbers 17-38 used in the present Example was manufactured as follows. Tough pitch copper having a purity of 99.9% and an oxygen content of 0.015% and Mn, Ti, and Al having a purity of 99.9%, respectively, were dissolved and stirred in an argon atmosphere in a graphite crucible as shown in Table 2, and the width was 50. The ingot was produced by pouring into a rectangular graphite mold of mm, a length of 100 mm, and a thickness of 15 mm. Thereafter, width bet rolling was performed to have a thickness of 10 mm in the width direction, hot rolling was performed at a maximum of 600 ° C., and further hot rolling was performed under the same conditions in the length direction to a thickness of 2 mm. Then, cold rolling was performed until it became 9 micrometers in thickness. In the meantime, both ends were cut by the slit process in the place where thickness was 0.5 mm, and the width was adjusted to 60 mm. Therefore, the obtained copper foil was 60 mm in width and 12 micrometers in thickness.

Thereafter, some copper foil was subjected to recrystallization heat treatment at 500 ° C. for 1 hour in a vacuum furnace. As a result of chemical analysis of the concentrations of Mn, Ti, and Al at both ends of the obtained copper foil and at the center portion, it was confirmed that there were almost no concentration variations in the case of the copper foil which was not subjected to the recrystallized heat treatment.

Next, using the polyamic-acid solution prepared by the method similar to the synthesis example 1 and the synthesis example 2 of Example 1, first, the polyamic-acid solution a is apply | coated to the surface of the copper foil which concerns on the sample numbers 17-38 prepared above. Dried to form a thermoplastic polyimide having a thickness of 2 µm, and then coated with polyamic acid b to dry (after curing, a low thermally expandable polyimide having a thickness of 8 µm), and thereon The polyamic acid a is applied and dried (after curing, a thermoplastic polyimide having a thickness of 2 μm is formed), and the heating temperature is 5 minutes at a maximum temperature of 400 ° C. and the integration time in a temperature range of 360 to 400 ° C. is obtained. The resin layer which consists of polyimide of a 3-layered structure was formed through the heat processing by.

Subsequently, it cuts out so that it may become rectangular size of width 250mm in the direction orthogonal to a 250 mm length and a rolling direction along the rolling direction of copper foil, and has a resin layer (polyimide) of thickness 12 micrometers, and the copper foil layer of thickness 12 micrometers. The single-sided copper clad laminate for testing according to Example 2 was obtained.

The elongation at break and the structure analysis were performed similarly to Example 1 about the copper foil (copper foil layer) in the single-sided copper clad laminated board for a test obtained above. Moreover, the predetermined mask was put on the copper foil side of the single-sided copper clad laminated board for a test, and it etched using the iron chloride / copper chloride system solution, and formed the wiring pattern similar to Example 1. And a flexible test circuit having a width of 150 mm in the longitudinal direction along the wiring direction (H) of the circuit board and a width of 40 mm in the direction orthogonal to the wiring direction (H) in accordance with JIS 6471 to serve as a sample for bending test described later. A substrate was obtained. Moreover, it confirmed that there was no change in the structure of copper foil before and after circuit formation by etching.

Next, with respect to the test flexible circuit board having the resin layer 1 and the wiring (copper foil) 2, as shown in Fig. 4 (b), an epoxy adhesive is used on the surface of each wiring pattern side. The cover material 7 (Arizawa Seisakusho CVK-0515KA: thickness 12.5 micrometers) was laminated | stacked. The thickness of the adhesive layer 6 which consists of adhesives was 15 micrometers in the part without a copper foil circuit, and was 6 micrometers in the part in which a copper foil circuit exists. And it cut out so that it might be set to 15 cm in the longitudinal direction along the wiring direction (H direction), and width 8mm in the direction orthogonal to the wiring direction, and obtained the test flexible circuit board for making an IPC test sample.

As shown in the schematic diagram in FIG. 4, the IPC test simulates a slide bend, which is one of the bend forms used in a cellular phone and the like. As shown in FIG. 4, the IPC test is a test in which a bent portion is provided with a predetermined gap length 8, one side is fixed by the fixing portion 9, and the opposite slide movable portion 10 is repeatedly reciprocated as shown in the figure. Therefore, the substrate is repeatedly bent in the region corresponding to the stroke amount of the reciprocating portion. In the present Example, the resin layer (polyimide) 1 was made to the outer side, the gap length was 1 mm, ie, the bending radius was 0.5 mm, and the stroke was 38 mm, and it repeated and tested. During the test, the electrical resistance of the circuit of the test flexible circuit board was measured, and the progress of the fatigue crack of the copper foil circuit was monitored by the increase of the electrical resistance. In this embodiment, the number of strokes in which the electrical resistance of the circuit reached twice the initial value was taken as the circuit breaking life. Under this test condition, since the ridges formed in the bent portion are bent so as to be orthogonal to the wiring direction of the wiring 2 of the test flexible circuit board, the main stress and major distortion applied to the copper circuit are in the rolling direction. Parallel tensile stress, tensile distortion.

When the cross section which cut | disconnected the copper foil in the thickness direction by making it orthogonal to the copper foil after circuit break life is observed with a scanning electron microscope, although there exists a difference in a degree, a crack generate | occur | produces in each copper foil surface of a resin layer side and a cover material side. In particular, it was observed that a large number of cracks were introduced into the copper foil surface on the resin layer side corresponding to the outer side of the bent portion.

Table 2 shows the results of the amount of Mn, Ti, Al in the copper foil obtained by the test described above, the elongation at break of the copper foil, the <100> preferred orientation area ratio, and the bending life.

As can be seen from Table 2, in the IPC test, high bending resistance over 30,000 times of fatigue life is obtained, while the Mn concentration is 0.001% by mass or more, and the Ti concentration is 0.005% by mass or more and 0.2% by mass or less, Alternatively, it was found that the Al concentration was 0.005% by mass or more and 2% by mass or less and the area ratio of the <100> preferred alignment region was 60% or more. At concentrations of 0.2% by mass and 2% by mass of Al or more, respectively, a cubic texture having a very high degree of integration was not obtained despite the recrystallization heat treatment at 500 ° C. for 1 hour. The bending resistance of such a sample is low. When the structure of the sample of Sample No. 31 having an Al concentration of 2.1% by mass after the IPC test was observed, an intermetallic compound composed of Cu and Al was present, and cracks were generated in the vicinity. The reason why the fatigue life is lowered is that in normal dissolution, the intermetallic compound is formed around the intermetallic compound that is harder than copper and cannot be formed in a single phase.

By adding a prescribed amount of Ti or Al in addition to Mn, the elongation at break increased. In particular, a large effect was obtained with a low Mn concentration compared with the case where Mn alone was added. In addition, when both Ti and Al were added to Mn, fatigue life was greatly improved in the IPC bending test.

[Example 3]

The copper foil used by the present Example was manufactured as follows. As a raw material, oxygen-free copper having an oxygen content of 0.0008% was used as a sheet thickness of 15 mm and a purity of 99.99% or more. The raw material copper and each alloying element weighed to a predetermined concentration were dissolved and stirred in an argon atmosphere in a graphite crucible, and poured into a rectangular graphite mold having a width of 50 mm, a length of 100 mm, and a thickness of 15 mm to prepare an ingot. The purity of lithium, calcium and ytterbium in the alloying elements is at least 99.9%. In addition, micrometals were also used as alloy elements. The main components of the micrometal are 25% by mass of La, 53% by mass of Ce, 6% by mass of Pr, and 15% by mass of Nd, and the sum of these elements is 99% by mass, and the balance is different from other rare earth metals. Other inevitable impurities that contain.

The cast ingot was subjected to width-proof rolling to a thickness of 10 mm in the width direction, hot rolling at a maximum of 600 ° C., and further hot rolling to the thickness of 1.5 mm under the same conditions in the longitudinal direction. The sample which does not add an alloying element was hot-rolled on the same conditions that the raw material copper plate was cut | disconnected in the same size as a casting ingot. Thereafter, these hot rolled plates were cold rolled to a thickness of 9 µm. In the meantime, both ends were cut by the slit process at the place of thickness 0.5mm, and the width was adjusted to 60mm. Therefore, the obtained copper foil was 60 mm in width and 9 micrometers in thickness. Moreover, it melt | dissolved and cast, without adding an alloying element, and produced the comparative material in the same process. As a result of the chemical analysis of the density | concentration of the alloying element of the both ends and center part of the obtained copper foil, it confirmed that there was little density | variation variation of the alloying element in some cases. The alloy concentration of the copper foil (sample numbers 39-70) used by the present Example is put together in Table 3, and is shown. In Table 3, copper content is a calculated value calculated | required as follows from the amount of impurities derived from the analyzed alloy element and a raw material, and is a theoretical range.

That is, the minimum of copper content shown in Table 3 was calculated | required as "(minimum value of raw material purity)-(alloy element content)-(impurity derived from alloy element)." For example, sample number 41 is '99 .99-0.0042-0.0042 × 1/999 = 99.9858 (%) ', and sample number 61 is '99 .99- (0.0026 + 0.0012 + 0.0002 + 0.005)-(0.0026 + 0.0012). + 0.0002 + 0.005) × 1/99 = 99.9854 '. In addition, the upper limit was calculated | required by "100- (alloy element content). When calculating this upper limit, the impurity derived from an alloying element was treated as a gas component refine | purified in the process of alloying, and was not included in a calculation formula. For example, in case of sample No. 41, '100-0.0042 = 99.9958 (%)'. However, in the case of copper foil which does not add an alloying element like sample numbers 39 and 40, oxygen content was taken out. Moreover, when the numerical value of 5 decimal places or less came out, it calculated by cutting off 5th digit at the lower limit.

Moreover, the polyamic-acid solution which is a precursor of the polyimide which comprises the resin layer of the test flexible circuit board of this Example was obtained according to the two types of synthesis examples described in Example 1.

Next, the formation method of the copper clad laminated board which is a composite of copper foil and a polyimide is demonstrated.

The polyamic acid solution a obtained in Synthesis Example 1 was applied to one surface of the copper foil prepared above and dried (after curing, a thermoplastic polyimide having a thickness of 2 μm was formed), and the polyamic acid b obtained in Synthesis Example 2 thereon. Was applied and dried (after curing to form a low thermally expandable polyimide having a thickness of 9 µm), and polyamic acid a was applied thereon to dry (after curing, a thermoplastic polyimide having a thickness of 2 µm was formed), The resin layer which consists of polyimide of a three-layered structure was formed through the heating conditions by which the temperature of 280 degreeC or 350 degreeC is loaded 5 minutes or more by integration time. In addition, this heat processing temperature is made into the polyimide formation temperature.

Subsequently, it cuts out so that it may become rectangular size of width 40mm in length 250mm and the direction orthogonal to a rolling direction (TD direction) along the rolling direction (MD direction) of copper foil, and the resin layer (polyimide) of 13 micrometers in thickness (1 ) And a single-sided copper clad laminate for testing having a copper foil layer 2 having a thickness of 9 μm (FIG. 5). The tensile elasticity modulus of the whole resin layer at that time was 7.5 GPa.

The structure analysis was performed like Example 1 about the copper foil (copper foil layer) in the single-sided copper clad laminated board obtained above. Moreover, the predetermined | prescribed mask was put on the copper foil side of the single-sided copper clad laminated board for a test obtained above, and it etched using the iron chloride / copper chloride type solution, and formed the wiring pattern similar to Example 1. Then, a flexible test board having a width of 150 mm in the longitudinal direction along the wiring direction (H) of the circuit board and a width of 40 mm in the direction orthogonal to the wiring direction (H) was used in accordance with JIS 6471 to serve as a sample for bending test. Got it. It was confirmed that there was no change in the structure of the copper foil before and after the circuit formation by etching.

Using the test flexible circuit board obtained above, the MIT bending test was carried out similarly to Example 1 according to JIS C5016. Under this test condition, since the ridge lines formed in the bent portion are bent so as to be orthogonal to the wiring direction H of the wiring of the test flexible circuit board, the main stress and the main distortion applied to the copper foil circuit are tensilely parallel in the rolling direction. Stress, tensile distortion. When the circuit was observed from the thickness direction of the copper foil after the bending test, it was confirmed that the crack was broken in the vicinity of the ridge line of the bent portion almost perpendicular to the rolling direction.

The amount of alloy elements in the copper foil obtained by the test described above, the <100> preferred orientation area ratio, and the bending life are shown in Table 3 together with the sample number and the polyimide formation temperature. Flexural life is an average of the result of the test flexible circuit board which prepared five pieces for each kind of copper foil. What is represented by-in a component value shows that it is below the measurement limit value of a chemical analysis.

As is clear from the results shown in Table 3, 0.005 mass% or more is 0.45 mass% or more of 1 or more types chosen from the group which consists of Ca, La, Ce, Pr, Nd, Yb, and Y compared with the copper foil produced without adding an alloying element. By containing it in the mass% or less, it turned out that the area ratio of the <100> preference orientation area | region became large compared with the same heat processing temperature, and the fatigue life improved. In addition to Ca and Y, effects were also obtained for La and the smallest Yb in the lanthanoid genus, so that Sm, Eu, Gd, Dy, Ho, Er The same effect can be judged also in Tm.

Moreover, although the area ratio of the <100> preferential orientation area | region of copper foil differs significantly with the temperature which forms the single-sided copper clad laminated board for a test, ie, polyimide formation temperature in a present Example, also in the thermal history of 280 degreeC and 5 minutes, Within the range of the alloying component, the area ratio of the <100> preferred alignment region is obtained by 60% or more, and the area ratio of the <100> preferred alignment region and fatigue life are higher than those of the copper foil produced without adding an alloying element. I could see that. In the case where 0.4 mass% of Ca was added in Sample Nos. 52 to 54 (Sample No. 54), the area ratio of the <100> preferred alignment region was lowered, and the recrystallization temperature was increased due to the addition of the alloying element. It is considered that the formation of recrystallized texture was inhibited.

Example 4

In this embodiment, a copper foil containing alloys of these is prepared by using micrometals, Ti, and Al, and the copper foil structure is analyzed from the test single-sided copper clad laminate obtained by using the same, and the test flexible circuit board is used as a test single-sided copper clad laminate. Was produced and the bending fatigue characteristic was measured. In addition, the main component of the micrometal used in the present Example is 25 mass% of La, 54 mass% of Ce, 6 mass% of Pr, and 14 mass% of Nd, and the purity of the sum total of these elements is 99 mass%. Other components are other unavoidable impurities containing other rare earth metals.

The copper foil used by the present Example was manufactured as follows. Thickness 15mm, purity 99.9% or more, 0.015 mass% of oxygen content, 0.03 mass% of sulfur content, and 0.02% of silver content, Ti and Al alloy element of 99.9% or more of purity and weighed in predetermined quantity, and the said constituent element, The fine metal having the purity was weighed to a predetermined concentration, dissolved and stirred in an argon atmosphere in a graphite crucible, and poured into a rectangular graphite mold having a width of 50 mm, a length of 100 mm, and a thickness of 15 mm to prepare an ingot.

The cast ingot was subjected to width-proof rolling to have a thickness of 10 mm in the width direction, hot rolling at a maximum of 600 ° C., and further hot rolling under the same conditions in the longitudinal direction to a thickness of 1 mm. Then, cold rolling was performed until it became 12 micrometers in thickness. In the meantime, both ends were cut by the slit process at the place of thickness 0.5mm, and the width was adjusted to 60mm. Therefore, the obtained copper foil was 60 mm in width and 12 micrometers. Moreover, it melt | dissolved and cast, without adding an alloying element, and produced the comparative material in the same process. Moreover, when the density | concentration of the alloying component was chemically analyzed about the obtained copper foil, it confirmed that there was almost no density | concentration variation in case with any copper foil. The alloy concentration of the copper foil (sample numbers 71-84) used by the present Example is put together in Table 4, and is shown. In Table 4, copper content is a calculated value calculated | required from the impurity amount of the alloying element and raw material analyzed as demonstrated in Example 3, and is a theoretical range.

Among these, the upper limit of the copper content was calculated when the other impurities were gas components and the like, and all were discharged out of the system by reaction with gas or rare earth elements in the course of alloying.

In addition, the lower limit computed that all the impurities in the raw material remained in the alloy. In other words, 1% of La, Ce, Pr, and Nd in the rare earth elements are other than the elements shown in Table 4 except for the content of the alloying elements except silver from the lower limit of the purity of the raw material copper. Similarly, 0.1% impurity content of Al and Ti remained. In addition, silver was not added as an alloying element but mainly mixed as an impurity in raw material copper, and was added to the value removed. For example, the lower limit of Sample No. 72 is '99 .9- (0.053 + 0.024 + 0.0061 + 0.014 + 0.0042) -1 / 99 × (0.053 + 0.024 + 0.0061 + 0.014) -1 / 999 × 0.0042 + 0.018 = 99.8147 ' do.

Next, the polyamic acid solution a prepared in the same manner as in Synthesis Example 1 of Example 1 was applied and dried (after curing, a thermoplastic polyimide having a thickness of 2 μm was formed), and Synthesis Example 2 of Example 1 thereon. The polyamic acid b prepared in the same manner as described above is applied and dried (after curing to form a low thermally expandable polyimide having a film thickness of 8 µm), and the polyamic acid a is applied thereon to dry (film thickness 2 after curing). A polyimide layer (resin layer) was formed through a heating condition in which a thermoplastic polyimide having a μm was formed) and a temperature at a maximum temperature of 320 ° C. was added for 10 minutes with integration time.

Subsequently, it cuts out so that it may become rectangular size of width 40mm in the direction (TD direction) orthogonal to length 250mm and a rolling direction along the rolling direction (MD direction) of copper foil, and the polyimide layer (resin layer) of thickness 12micrometer ( The single-sided copper clad laminate for testing according to Example 2 having 1) and a copper foil layer 2 having a thickness of 12 μm was obtained (FIG. 5). The tensile elasticity modulus of the whole resin layer at that time was 7.5 GPa.

The structure analysis was performed like Example 1 about the copper foil (copper foil layer) in the single-sided copper clad laminated board obtained above. Moreover, a predetermined mask was put on the copper foil layer side of the single-sided copper clad laminate for testing, and etching was performed using an iron chloride / copper chloride solution to form the same wiring pattern as in Example 1. And a flexible test circuit having a width of 150 mm in the longitudinal direction along the wiring direction (H) of the circuit board and a width of 40 mm in the direction orthogonal to the wiring direction (H) in accordance with JIS 6471 to serve as a sample for bending test described later. A substrate was obtained. Moreover, it confirmed that there was no change in the structure of copper foil before and after circuit formation by etching.

Next, with respect to the test flexible circuit board having the resin layer 1 and the wiring (copper foil) 2, as shown in Fig. 4 (b), an epoxy adhesive is used on the surface of each wiring pattern side. The cover material 7 (Arizawa Seisakusho CVK-0515KA: thickness 12.5 micrometers) was laminated | stacked. The thickness of the adhesive layer 6 which consists of adhesives was 15 micrometers in the part without a copper foil circuit, and was 6 micrometers in the part in which a copper foil circuit exists. And it cut out so that it might be set to 15 cm in the longitudinal direction along the wiring direction (H direction), and width 8mm in the direction orthogonal to the wiring direction, and obtained the test flexible circuit board for making an IPC test sample. Then, in the same manner as in Example 2, the IPC test was conducted, and the number of strokes in which the electrical resistance of the circuit reached twice the initial value was determined as the circuit breaking life. In addition, when the cross section which cut | disconnected the copper foil in the thickness direction by making it orthogonal to the copper foil after circuit break life is observed with a scanning electron microscope, although there exists a difference in degree similarly to Example 2, there exists a difference in the resin layer side and a cover material side Cracks occurred on each copper foil surface, and in particular, it was observed that a large number of cracks were introduced on the copper foil surface on the resin layer side corresponding to the outside of the bent portion.

The alloy component value, <100> preferred orientation area ratio, and bending life in copper foil obtained by the test described above are shown in Table 4 with a sample number and polyimide formation temperature. What is represented by-in a component value shows that it is below the measurement limit value of a chemical analysis. Since the raw material copper used by the present Example was comparatively low in purity, relatively many Ag was detected in addition to the alloying element added to copper foil. In addition, oxygen and sulfur were detected as other unavoidable impurities.

As is clear from the results shown in Table 4, the addition of mesh metal or alloying elements increases the area ratio of the <100> preferred orientation region of the copper foil and the fatigue life measured by the IPC test compared to the case where no addition of these is performed. I can see that there is. In addition, when Al, Ti, or both of them were added when the alloy concentrations of Ce, La, Pr, and Nd were almost the same, the <100> preferred alignment region was increased as the concentration increased within the range defined by the present invention. It can be seen that the fatigue life measured by the area ratio and the IPC test is increased. The sample of Sample No. 76 in which 0.41% by mass of Al was added and the Sample No. 81 in which 0.21% by mass of Ti were added, on the contrary, the fatigue life decreased. The excessive addition of the alloying element is thought to be because the recrystallization temperature is high and the formation of the <100> recrystallized texture is inhibited.

[Example 5]

In the present Example, these copper alloy foils were produced using Ce, La, Y, Sm, Ca, and Al as alloy elements, and the copper foil structure was analyzed from the test single-sided copper clad laminate obtained by using the alloy foil. The flexural fatigue characteristics were measured by fabricating a test flexible circuit board using a test single-sided copper clad laminate. In addition, the purity of the alloying elements used in the present Example is 99.9% or more, and each has the shape of a 2-3 mm particle state.

The copper foil used by the present Example was manufactured as follows. Raw material copper is tough pitch copper of diameter 5mm and length about 20mm, purity is 99.96% and oxygen content 0.029 mass%. In addition, the preparation composition (weighing composition) to be put before dissolution of the alloying element was fixed to 0.01%. That is, in the sample of Sample No. 89 shown in Table 5 below, the raw material copper was 99.8%, Ce was 0.1%, and Al was 0.1%.

The melting and casting of raw copper and alloying elements were made in two ways.

One is an alloy element wrapped in a copper foil obtained by rolling raw copper in advance into a crucible, and once buccumbed in a vacuum furnace, 99.99% of argon is introduced and 1200 ° C in an argon atmosphere controlled at 1 atmosphere. After melt | dissolving and stirring, the ingot was produced by pouring into the rectangular graphite mold of width 50mm, length 100mm, and thickness 15mm in the vacuum furnace. The produced ingot was ultrasonically cleaned in a pickling solution in which 20% hydrochloric acid and 0.1% hydrogen peroxide solution were added to pure water to remove scale from the surface.

Secondly, an alloying element wrapped in a copper foil rolled with raw copper was placed in a crucible, melted at 1200 ° C while introducing 99.99% of argon into a box furnace, the crucible was taken out, 50 mm in width, and length in air. An ingot was produced by flowing into 100 mm and a 15-mm-thick rectangular graphite mold. The produced ingot was ultrasonically washed in an acid washing solution in which 20% hydrochloric acid and 0.1% hydrogen peroxide solution were added to pure water to remove scale from the surface.

The processing method of the ingot after that was made into the same conditions irrespective of the atmosphere at the time of casting as mentioned above. The ingot was subjected to width bet rolling so as to have a thickness of 10 mm in the width direction, hot rolling at a maximum of 600 ° C., and further hot rolling under the same conditions in the longitudinal direction to a thickness of 1 mm. Then, cold rolling was performed until it became 12 micrometers in thickness. In the meantime, both ends were cut by the slit process at the place of thickness 0.5mm, and the width was adjusted to 60mm. Therefore, the obtained copper foil was 60 mm in width and 12 micrometers. Moreover, it melt | dissolved and cast, without adding an alloying element, and produced the comparative material in the same process. Moreover, when the density | concentration of the alloying component was chemically analyzed about the obtained copper foil, it confirmed that there was almost no density | concentration variation in case with any copper foil. The alloy concentration of the copper foil (Sample No. 85-98) used by the present Example is put together in Table 5, and is shown.

In Table 5, copper content is a calculated value calculated | required from the amount of impurities of the analyzed element and a raw material, and is a theoretical range. The upper limit of the content of copper is calculated as being composed only of alloy elements, oxygen and copper in the table. Thus, for example, in the case of sample No. 89, the upper limit value is '100-0.079-0.1-0.0067 = 99.8143 (%)'. On the other hand, the lower limit includes all elements other than the alloy element and the oxygen containing 0.011% other than 99.989% of the total amount of oxygen contained in the raw material copper and the raw material copper and 0.01% impurity concentration in the alloying element, all of which are copper foil It computed by subtracting from the upper limit as having entered into the middle. For example, in the case of Sample No. 89, the lower limit is '99 .8143-0.998 × 0.011-0.001 × 0.1-0.001 × 0.1 = 99.8031 (%) '.

The analytical value of the alloying element is smaller than 0.1% as shown, for example, as a result of Sample No. 89, but this is mainly caused by oxygen or sulfur contained in impurities and reaction with oxygen in the atmosphere during dissolution and casting. A sulfide is formed and discharged to the top or surface layer portion of the ingot and out of the system as a scale during acid washing. Although some deoxidation effect was recognized also in aluminum, it is thought that the rare earth element was larger in this condition.

Next, the polyamic acid solution a prepared in the same manner as in Synthesis Example 1 of Example 1 was applied and dried (after curing, a thermoplastic polyimide having a thickness of 2 μm was formed), and Synthesis Example 2 of Example 1 thereon. The polyamic acid b prepared in the same manner as described above was applied and dried (after curing to form a low thermally expandable polyimide having a film thickness of 8 µm), and the polyamic acid a was applied thereon to dry (film thickness 2 after curing). A polyimide layer (resin layer) was formed through a heating condition in which a thermoplastic polyimide having a μm was formed) and a temperature of a maximum temperature of 360 ° C. was added for 10 minutes by integration time.

Subsequently, it cuts out so that it may become rectangular size of width 40mm in the direction (TD direction) orthogonal to length 250mm and a rolling direction along the rolling direction (MD direction) of copper foil, and the polyimide layer (resin layer) of thickness 12micrometer ( The single-sided copper clad laminate for testing according to Example 3 having 1) and a copper foil layer 2 having a thickness of 12 μm was obtained (FIG. 5). The tensile elasticity modulus of the whole resin layer at that time was 7.5 GPa.

The structure analysis was performed like Example 1 about the copper foil (copper foil layer) in the single-sided copper clad laminated board obtained above. Further, a predetermined mask was placed on the copper foil layer side of the single-sided copper clad laminate for testing, and etching was performed using an iron chloride / copper chloride solution to form the same wiring pattern as in Example 1. And a flexible test circuit having a width of 150 mm in the longitudinal direction along the wiring direction (H) of the circuit board and a width of 40 mm in the direction orthogonal to the wiring direction (H) in accordance with JIS 6471 to serve as a sample for bending test described later. A substrate was obtained. Moreover, it confirmed that there was no change in the structure of copper foil before and after circuit formation by etching.

Next, about the test flexible circuit board which has the said resin layer 1 and wiring (copper foil) 2, the test flexible circuit board for making an IPC test sample similarly to Example 2 was obtained. In the present embodiment, the IPC layer was formed in the same manner as in Example 2 except that the polyimide layer (resin layer) 1 was made to the outside and the gap length was 1.5 mm, that is, the bend radius was 0.75 mm and the stroke was 38 mm. The test was conducted and the number of strokes for which the electrical resistance of the circuit reached twice the initial value was determined as the circuit breaking life. In addition, when the cross section which cut the copper foil in the thickness direction by making it orthogonal to a slide direction with respect to the copper foil after a circuit break life is observed with a scanning electron microscope, although there is a difference in a degree similarly to Example 2, the resin layer side and the cover material side Cracks occurred on the surface of each copper foil of, and in particular, it was observed that a large number of cracks were introduced on the copper foil surface on the resin layer side corresponding to the outside of the bent portion.

The alloy component value in a copper foil obtained by the test described above, a <100> preferred orientation area ratio, and a bending life are shown in Table 5 with a sample number and polyimide formation temperature. Marking-in the component value indicates unmeasured. As shown in the sample of Sample No. 85, the molten cast in the Ar air stream has a smaller oxygen concentration than the raw copper. This is a deoxidation effect by melt | dissolution and casting at low oxygen concentration. In addition, samples No. 87, 91, 94, and 96 were dissolved and cast under the same conditions by adding Ce, Y, Sm, and Ca. However, by adding these elements, the area ratio of the < 100 > It turns out that the fatigue life measured by the IPC test improves as a result. Comparing the results of the sample number 94 and the sample number 95, it can be seen that the fatigue life measured by the IPC test is increased by adding Al to Sm.

On the other hand, as shown in the case of Sample No. 86, in the air casting, the oxygen concentration of the copper foil is larger than that of the raw copper. On the other hand, when looking at the result of sample numbers 88, 90, 92, and 96, it turns out that the oxygen concentration in copper foil is reduced by adding Ce, La, Y, and Ca. This is because these elements have a deoxidation effect. The fatigue life measured by the IPC test in these samples is thought to be due to the direct effect of improving the area ratio of the <100> preferred orientation region of the rare earth element and the deoxidation effect due to the oxidation reaction during dissolution and casting. do. The results of Sample Nos. 89, 93, and 98 are considered to indicate that aluminum further enhances the effect.

(Industrial availability)

The copper foil of the present invention can be widely used in various electronic and electrical equipment as a flexible circuit board, and the circuit board itself is bent or twisted or deformed according to the operation of the mounted device, and has a bent portion anywhere. Suitable for use In particular, since the flexible circuit board of the present invention has a bent structure having excellent bending durability, the flexible circuit board is frequently bent with repeated operations such as sliding bending, bending bending, hinge bending, slide bending, or the like. In order to cope with miniaturization, it is preferable in the case of forming a bent portion which requires a very small radius of curvature. Therefore, it can be used suitably for various electronic devices, such as a thin cell phone, a thin display, a hard disk, a printer, and a DVD device which require durability.

1: resin layer
2: wiring (metal foil)
3: connector terminal
6: adhesive layer
7: cover material
8: gap length
9: fixed part
10: slide moving part
21: Normal direction of cross section (P)
L: Ridge
P: cross section of the wiring when cut in the thickness direction from the ridge line at the bent portion

Claims (19)

A copper foil containing 0.001% by mass or more and 0.4% by mass or less and having inevitable impurities and residual Cu, wherein two orthogonal directions in which the basic crystal axis of the copper unit grid exists in the thickness direction of the copper foil and in the thin surface A copper foil characterized by a preferred orientation area within 15 degrees of azimuth difference with respect to an axis occupying 60% or more in area ratio. The method of claim 1,
Copper content characterized by containing at least any one of 0.005 mass% or more and 0.2 mass% or less Ti, or 0.005 mass% or more and 2 mass% or less Al, while containing Mn 0.001 mass% or more and 0.1 mass% or less. 3. The method according to claim 1 or 2,
Copper foil containing 0.06 mass% or less of Mn. 0.005 mass% or more and 0.4 mass% or less of at least one element selected from the group consisting of Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y, Copper is 99.6 mass% or more and 99.999 mass% or less, The basic crystal axis of the copper unit lattice <100> has a preferred orientation within 15 degrees of orientation difference with respect to two orthogonal axes of either direction which exist in the thickness direction and thin surface of copper foil, respectively. Copper foil characterized by the area occupying 60% or more by area ratio. 5. The method of claim 4,
At least any one of 0.005 mass% or more and 0.2 mass% or less of Ti or 0.005 mass% or more and 0.395 mass% or less of Al is contained. The method according to any one of claims 1 to 5,
Copper foil whose content of oxygen is less than 0.1 mass%. The copper clad laminated board which has the copper foil layer which consists of copper foil of any one of Claims 1-6, and the resin layer laminated | stacked on it. The method of claim 7, wherein
The copper clad laminated board whose thickness of a copper foil layer is 5 micrometers or more and 18 micrometers or less, and the thickness of a resin layer is 5 micrometers or more and 75 micrometers or less. 9. The method according to claim 7 or 8,
The copper clad laminated board in which a resin layer consists of polyimide. A flexible circuit board, wherein the copper foil layer of the copper clad laminate according to any one of claims 7 to 9 is etched to form a predetermined wiring, and a bent portion is formed and used at at least one of the wirings. The method of claim 10,
A flexible circuit board used to form a bend with one or more repetitive motions selected from the group consisting of sliding bend, bending bend, hinge bend and slide bend. An electronic device comprising the flexible circuit board according to claim 10 or 11. A method for producing a copper clad laminate having a copper foil layer and a resin layer, wherein a polyamic acid solution is applied to the surface of a cold rolled copper foil containing Mn of 0.001% by mass or more and 0.1% by mass or less and having an unavoidable impurity and residual Cu in its composition. By heat treatment or by superimposing a polyimide film to form a resin layer made of polyimide on the cold rolled copper foil, and recrystallizing the cold rolled copper foil so that the basic crystal axis of the copper unit lattice <100> A copper foil layer, wherein the copper foil layer occupies 60% or more of the preferred orientation region within an orientation difference of 15 ° with respect to two orthogonal axes in either direction existing in the thickness direction and the thin surface, respectively. 14. The method of claim 13,
The manufacturing method of the copper clad laminated board which cold-rolled copper foil further contains at least any one of 0.005 mass% or more and 0.2 mass% or less of Ti, or 0.005 mass% or more and 2 mass% or less of Al. The method according to claim 13 or 14,
The manufacturing method of the copper clad laminated board in which cold rolled copper foil contains Mn of 0.06 mass% or less. At least one selected from the group consisting of Ca, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y as a method for producing a copper clad laminate having a copper foil layer and a resin layer A polyamic acid solution is applied to the surface of a cold-rolled copper foil containing 0.005% by mass or more and 0.4% by mass or less and the residual copper is 99.6% by mass or more and 99.999% by mass or less, or the polyimide film is overlaid and thermally compressed. A resin layer made of polyimide is formed on the cold rolled copper foil, and the cold rolled copper foil is recrystallized, so that the basic crystal axes of the copper unit lattice are in two directions in the thickness direction of the copper foil and in the thin surface. A copper foil layer which occupies 60% or more of preferred orientation areas within 15 degrees of an orientation difference with respect to an orthogonal axis, respectively, in area ratio. 17. The method of claim 16,
The manufacturing method of the copper clad laminated board in which a cold rolled copper foil contains 0.005 mass% or more and 0.2 mass% or less of Ti, or 0.005 mass% or more and 0.395 mass% or less of Al. 18. The method according to any one of claims 13 to 17,
The manufacturing method of the copper clad laminated board whose temperature which heat-processes the apply | coated polyamic-acid solution and forms a resin layer is 280 degreeC or more and 400 degrees C or less. 18. The method according to any one of claims 13 to 17,
The manufacturing method of the copper clad laminated board whose temperature which thermocompresses a polyimide film and forms a resin layer is 280 degreeC or more and 400 degrees C or less.

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