JP6196429B2 - Copper alloy sheet with excellent heat dissipation and repeated bending workability - Google Patents

Description

  The present invention relates to a copper alloy plate suitable as a flexible printed circuit board (FPC) including an LED mounting substrate for illumination and the like, particularly a copper alloy plate excellent in heat dissipation and repetitive bending workability, and an electronic apparatus using the same It relates to parts.

  LED lighting has advantages such as low power consumption, long life, and high-speed response compared to conventional incandescent bulbs and fluorescent lamps, etc., and it is rapidly spreading as product prices decrease. In addition, various applications such as backlights for LCD TVs and LCD monitors, and lighting for automobiles are also expanding.

  Since the LED itself is a semiconductor, the light emitting element itself has a long life when used within the rated range. However, the resin material covering the light emitting element is easily deteriorated by heat, and the transparency is easily lowered by heat generation. Unsuitable for use. In addition, LEDs are manufactured in various package shapes in consideration of light emission characteristics and heat dissipation. However, when used in a small space, various devices such as space saving and molding methods are required. It is.

  In order to deal with the problem of heat generation, in order to efficiently dissipate heat from the FPC, it has been proposed to attach a heat sink to the FPC, and for space saving, an attempt has been made to place an LED on the FPC. (Patent Document 1).

  In addition, as a lighting device, it has been proposed to perform complicated processing on a circuit board on which LEDs are arranged to perform three-dimensional molding (Patent Document 2).

JP 2007-141729 A Japanese Patent Laid-Open No. 2007-5003

When the LED is mounted on the FPC, the heat dissipation of the resin that is the substrate is not sufficient, so that the resin that covers the light emitting element is deteriorated by heat for a long time, and the lifetime as illumination is shortened.
As a countermeasure to heat generation, when an aluminum plate is bonded to the FPC as a heat dissipation plate, there is a problem that warpage occurs in the FPC circuit due to a difference in linear thermal expansion coefficient from the copper wiring constituting the FPC circuit. Furthermore, by repeatedly expanding and contracting due to heat, there is a problem that the copper wiring of the FPC is repeatedly subjected to tensile stress and breaks.
The above problem does not occur when a copper plate is used as the heat sink, but copper has a higher work hardening coefficient than aluminum, so when forming FPC into a complex shape, bending part or bending back and rebending Under molding conditions such as performing cracks, cracks are likely to occur in the bent portion. When a crack occurs, when it is used in an environment where repeated vibration is applied, such as in-vehicle, a problem such as the crack progressing and breaking occurs.
Although a method of three-dimensionally forming a lighting device using a copper plate as an FPC substrate is conceivable, general tough pitch copper softens the copper plate itself due to heat generation while it is used in the lighting device, and maintains the initial shape. Is difficult.
That is, the present invention has been made to solve the above problems, and it is an object to provide a copper alloy plate for an FPC board that is excellent in heat dissipation, repeated bending workability, shape maintenance, and heat resistance. And

  The present inventor has conducted research to solve the above problems, and can control the bending workability and the like by controlling the existence density of the shear band in a predetermined range of the material thickness of the copper alloy plate. I found.

In one aspect, the present invention completed on the basis of the above knowledge is one or more selected from the group consisting of Ag, Cr, Fe, In, Ni, P, Si, Sn, Ti, Zn, and Zr. .01 mass% or more, Ag is 1.0 mass% or less, Ti is 0.08 mass% or less, Ni is 2.0 mass% or less, Zn is 3.5 mass% or less, Cr, Fe, In, P, Si, Sn, and Zr contain at least 0.5% by mass in total of one or more selected from these groups, and are composed of the balance Cu and impurities,
Conductivity is 60% IACS or higher,
The tensile strength is 350 MPa or more,
In the rolling parallel cross section, among the three straight lines perpendicular to the thickness direction that divide the material thickness T into four equal parts, the remaining two straight lines excluding the center line, The number of intersecting shear bands n is
n ≦ 300
Meets the material thickness T is a copper alloy sheet is 0.05 to 0.3 mm.

Copper alloy sheet according to the present invention in one embodiment, the tensile strength is more than 250MPa after heating at 200 ° C. 30 min.

  In one embodiment, the copper alloy plate according to the present invention is for an FPC board.

  In another embodiment, the copper alloy plate according to the present invention is for an FPC board on which LED lighting is mounted.

  Another aspect of the present invention is an electronic device component using the copper alloy plate of the present invention.

  In still another aspect, the present invention is an FPC in which LED lighting using the copper alloy plate of the present invention is mounted.

  ADVANTAGE OF THE INVENTION According to this invention, the copper alloy plate for FPC boards excellent in heat dissipation, repeated bending workability, shape maintenance property, and heat resistance can be provided.

FIG. 1 is a schematic diagram of a shear band in a rolled parallel section of a copper alloy sheet. FIG. 2 shows a SEM cross-sectional photograph when a copper alloy sheet is observed by being cut in the rolling parallel direction.

(Copper foil components)
In the present invention, in order to improve the heat resistance of the copper foil, at least one selected from the group consisting of Ag, Cr, Fe, In, Ni, P, Si, Sn, Ti, Zn and Zr is added to the copper. Add 0.01% by mass or more. When the total concentration of the additive elements is less than 0.01% by mass, the effect of the additive elements is not exhibited and the heat resistance is insufficient. Further, the upper limit of the total concentration of the additive elements is as follows.
Ag is not particularly limited because it is less affected by the decrease in conductivity due to the addition, but is preferably 1.0% by mass or less because the concentration increases and the cost increases.
Cr, Fe, In, P, Si, Sn, and Zr, which have a large effect on the decrease in conductivity due to the addition, are 0.5% by mass or less of the total of these elements. 08 mass% or less is preferable.
Ni is preferably 2.0% by mass or less, and Zn is preferably 3.5% by mass or less.

As the base Cu to which the alloy element is added, oxygen free copper standardized to JIS H3100 C1020 or tough pitch copper standardized to JIS H3100 C1100 is suitable. The oxygen concentration is usually 0.01 to 0.05% by mass for a tough pitch copper melt and 0.001% by mass or less for an oxygen free copper melt.
In general, Cr, Fe, In, Ni, P, Si, Sn, Ti, Zn, and Zr, which are easily oxidized as compared with Cu, are added to the oxygen-free copper melt. After adding a deoxidizer such as P or Si to the molten copper containing oxygen to reduce the oxygen concentration to 10 ppm or less, these alloy elements may be added. Since Ag is less susceptible to oxidation than Cu, it can be added both in the tough pitch copper melt and in the oxygen free copper melt.

(Heat dissipation)
In order to dissipate the heated material, a material having good heat conduction is required. The heat conduction is preferably a material having a high electrical conductivity. Considering the heat generated when the LED lighting is on, there are influential factors such as the LED mounting density and the shape of the lighting device, but the conductivity of the material may be 60% IACS or more, and more preferably 70% IACS or more. .

(Repeated bending workability)
As for the repetitive bending workability, the relationship with the metal structure was examined, and it was related to the existence density of the shear band. In the rolling parallel section, the three straight lines perpendicular to the thickness direction dividing the material thickness T into four equal parts. Among the remaining two straight lines excluding the center line, the number n of shear bands intersecting with each straight line is n ≦ 300 in the observation range of each length 100T, that is, the total observation range of length 200T. In some cases, the repeated bending workability was good. The value of n is preferably 250 or less, more preferably 150 or less.
A shear band is a structure in which shear deformation occurs intensively when a material is strongly processed, and appears on the observation surface. In rolling, the structure is observed as a discontinuous surface of the rolling structure. Can be identified as a line inclined by 30 to 60 degrees. Further, the shear band spreads in the thickness direction, and the spread, that is, the length in the thickness direction may vary depending on the thickness of the material, the degree of processing, and the like.
For the shear band, the copper foil rolled parallel section after the final rolling is processed by, for example, a focused ion beam (FIB), a scanning ion microscope (SIM) or a scanning electron microscope (SEM). It can be observed with a Microscope or processed with a cross section polisher (CP) and observed with an SEM.

(Shape maintenance)
After the material is formed into a predetermined shape, a certain level of material strength is required to maintain the initial processed shape. Although there is an influence of the structure such as the processing shape, the tensile strength is 350 MPa or more and 400 MPa or more because the material is easily deformed by the applied force when the tensile strength which is the material strength is less than 350 MPa. It is more preferable that The upper limit of strength is not particularly set, but it is generally known that when the strength is increased by increasing the workability of the material, bending workability is generally deteriorated. Therefore, the balance with bending workability is considered. Then, the material can be processed.

(Heat-resistant)
About heat resistance, from the characteristic of LED lighting, it is designed so that it may be normally used at the temperature of less than 150 degreeC so that it can be used as lighting equipment for a long time. Even if the temperature is lower than 150 ° C., it is inevitable that general tough pitch copper is softened by long-term use, and when it is softened, the initial processed shape cannot be maintained. In order to avoid such a phenomenon, it is important to ensure heat resistance. On the other hand, it is assumed that the lighting equipment will be used for several tens of thousands of hours, but a long-time heating test that reproduces this as it is is not realistic. Heating was performed at 200 ° C. for 30 minutes, and when the tensile strength was 250 MPa or more, the heat resistance was judged to be good. Moreover, it is more preferable to maintain 300 MPa or more after heating at 200 ° C. for 30 minutes.

  The thickness of the copper alloy plate according to the present invention is preferably 0.05 to 0.3 mm. If the thickness of the copper alloy plate is less than 0.05 mm, there is a problem that it is difficult to maintain the shape because the material is thin. May become too heavy. In addition, as described above, the copper alloy plate according to the present invention includes a form of copper foil.

  If the existence density of the shear band of the copper alloy plate is in the above characteristic range, the effect of the present invention is exhibited regardless of the components and the production conditions. The copper alloy plate of the present invention can be manufactured, for example, by the following process.

The manufacturing process of a rolled copper foil uses electrolytic copper as a raw material for pure copper, adds an alloying element as necessary, and casts to produce an ingot having a thickness of 100 to 300 mm. This ingot is hot-rolled to a thickness of about 5 to 20 mm, and then cold-rolling and annealing are repeated to finish it to a predetermined thickness by cold-rolling.
A copper foil that satisfies the specified ranges for the above-mentioned repeated bending workability, tensile strength, and density of shear bands is determined by the temperature increase rate of the final recrystallization annealing and the final cold rolling performed immediately after the final recrystallization annealing. It is obtained by adjusting the total processing degree, which is a processing condition, and the processing degree of the first pass. Here, the final recrystallization annealing is a recrystallization annealing before the final cold rolling for processing to the thickness of the product. In the final cold rolling, the material is repeatedly passed between a pair of rolls (hereinafter referred to as “pass”) to finish the thickness. Here, the first pass indicates the first pass in the final cold rolling in which the material after the final recrystallization annealing is finished to the product thickness.
The temperature increase rate of the final recrystallization annealing may be 12 to 50 ° C./s. When the rate of temperature increase is less than 12 ° C./s and when it exceeds 50 ° C./s, it is difficult to satisfy the above-described repeated bending workability.
The total work degree of final cold rolling should just be 85% or less. Here, the degree of work represents a percentage obtained by dividing the difference in thickness between before and after rolling by the thickness before rolling. When the total workability of final cold rolling exceeds 85%, it is difficult to satisfy the above-described repeated bending workability. Further, the lower limit value of the total workability may be set so as to exceed the lower limit value of the tensile strength, although it varies depending on the alloy components and the concentration.
The degree of processing in the first pass of the final cold rolling may be 20% or less. When the degree of work in the first pass of the final cold rolling exceeds 20%, a shear band is likely to be generated, so that the specified density of the shear band cannot be satisfied, and the above-described repeated bending workability is satisfied. Is difficult.

  The copper alloy plate of the present invention can be used for electronic device parts such as lead frames, connectors, pins, terminals, relays, switches, and foil materials for secondary batteries. In particular, the copper alloy plate of the present invention is suitable as an FPC material on which LED lighting is mounted.

  Examples of the present invention are shown below, but these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the invention.

[Manufacture of rolled copper foil]
Various elements were added to oxygen-free copper to cast an ingot having a thickness of 100 mm. Next, the ingot is rolled to 5 mm by hot rolling, and after removing the oxide scale, cold rolling and annealing are repeated, and 0.05 to 0 under the conditions shown in Tables 1 and 2 by final cold rolling. Rolled to 3 mm. The final recrystallization annealing was performed at the rate of temperature increase described in Tables 1 and 2, and the material temperature was heated to 500 ° C. at maximum, and the rate of temperature increase was calculated from the time to reach 500 ° C. from room temperature (25 ° C.). . And it cooled immediately after material temperature reached | attained 500 degreeC.

[Shape maintenance]
In accordance with JIS Z 2241, a JIS No. 13B test piece collected so that the rolling parallel direction was the longitudinal direction was used as a test material, and the tensile strength was obtained by a tensile test. In the tensile test, UTM-10T manufactured by ORIENTEC Co., Ltd. was used, and the average value measured at n = 2 for the same sample at a tensile speed of 5 mm / min was used as the measured value. The shape maintainability was evaluated as good (◯) when the tensile strength was 350 MPa or more. In addition, when the pressure was less than 350 MPa, the shape maintainability was evaluated as poor (x).

[Heat dissipation]
The plate thickness after the final cold rolling was evaluated by the conductivity (% IACS) measured by the four-terminal method based on JIS H 0505.

[Shear band density]
About the material after the last cold rolling, material was cut | disconnected in the rolling parallel direction by CP, and the cross-sectional image by SEM was obtained. A discontinuous portion with the rolling structure inclined by 30 to 60 degrees with respect to the rolling surface was determined as a shear band. Among the three straight lines perpendicular to the thickness direction that divide the material thickness into four equal parts, the remaining two straight lines excluding the center line are each length 100T, that is, the total length 200T is used as the observation range. The number of shear bands intersecting with was visually evaluated on an electron microscope monitor. As an example of the evaluation of the number of shear bands, when observed as in the schematic diagram shown in FIG. 1, the remaining 2 excluding the center line among the three straight lines perpendicular to the thickness direction dividing the material thickness into four equal parts. The number of shear bands that intersect the straight line of the book is four. Moreover, the SEM cross-section photograph when a copper alloy plate is cut | disconnected in the rolling parallel direction and observed in FIG. 2 is shown. In FIG. 2, the portion indicated by the dotted line is a shear band.

[Heat-resistant]
Using the above JIS13B test piece, the sample was put in a heating furnace and, after the temperature reached 200 ° C., held for 30 minutes, the sample was taken out, air-cooled, and subjected to a tensile test. The tensile test was performed under the same conditions as the above shape maintainability. As for heat resistance, a tensile strength of 250 MPa or more was indicated by “◯”, and a tensile strength of less than 250 MPa was indicated by “x”.
Tables 1 and 2 show the evaluation conditions and results.

[Repeated bending workability]
Repeated bending workability was evaluated by the following procedure.
(1) A sample was cut into a length of 50 mm and a width of 10 mm in the rolling parallel direction and the perpendicular direction.
(2) V-bending was performed at 90 ° at a bending R = 0.5 mm, and this was bent back to the original strip shape, and then 90 ° V bending and bending back were repeated.
(3) The above operation was repeated, and the bent portion when bent 90 ° V every time was magnified 50 times to confirm whether cracks or breakage occurred. Then, the maximum number of bendings at which cracks or breakage did not occur was investigated. The maximum number of bendings at which cracks did not occur was evaluated as “」 ”for 4 times or more,“ ◯ ”for 4 times,“ Δ ”for 3 times, and“ x ”for less than 3 times.
The above evaluation conditions and the results are shown in Tables 1 and 2.

In Examples 1 to 33, the additive element concentration is 0.01% by mass or more, the concentration of each element is not more than the upper limit value, the tensile strength is 350 MPa or more, and the tensile strength after heating at 200 ° C. for 30 minutes. Since the thickness is 250 MPa or more and the existence density of the shear band is 300 or less, all of them were excellent in heat dissipation (conductivity), repeated bending workability, shape maintenance, and heat resistance.
Comparative Example 1 was pure copper with no additive elements and had poor heat resistance.
In Comparative Example 2, Sn was added, but the heat resistance was poor because the concentration was less than 0.01% by mass.
In Comparative Example 3, the total workability of final cold rolling exceeded 85%, so the shear band density did not satisfy the specified number, and the repeated bending workability was poor.
In Comparative Example 4, the additive element concentration was too high, so the conductivity was low and the heat dissipation was poor.
In Comparative Examples 5 and 9, the total degree of rolling in the final cold rolling is 85% or less, but since the degree of processing in the first pass in the final cold rolling exceeds 20%, the shear band density is the specified number. The repeated bending workability was poor.
In Comparative Example 6, the total degree of rolling in the final cold rolling is 85% or less, but since the temperature increase rate in the final recrystallization annealing is less than 12 ° C./s, the shear band density satisfies the specified number. The repeated bending workability was poor.
In Comparative Example 7, the total degree of rolling in the final cold rolling is 85% or less, but since the temperature increase rate in the final recrystallization annealing exceeds 50 ° C./s, the shear band density satisfies the specified number. The repeated bending workability was poor.
In Comparative Example 8, since the total degree of work in final recrystallization annealing was too low, the tensile strength was less than 350 MPa, and the shape maintainability was poor.

Claims (6)

It contains 0.01% by mass or more in total of at least one selected from the group consisting of Ag, Cr, Fe, In, Ni, P, Si, Sn, Ti, Zn and Zr, and Ag is 1.0% by mass or less. , Ti is 0.08 mass% or less, Ni is 2.0 mass% or less, Zn is 3.5 mass% or less, and Cr, Fe, In, P, Si, Sn, and Zr are selected from these groups 1 type or more in total, containing 0.5% by mass or less, consisting of the balance Cu and impurities,
Conductivity is 60% IACS or higher,
The tensile strength is 350 MPa or more,
In the rolling parallel cross section, among the three straight lines perpendicular to the thickness direction that divide the material thickness T into four equal parts, the remaining two straight lines excluding the center line, The number of intersecting shear bands n is
n ≦ 300
Meet the,
A copper alloy plate having a material thickness T of 0.05 to 0.3 mm . Copper alloy plate according to claim 1, the tensile strength is more than 250MPa after heating at 200 ° C. 30 min.   The copper alloy sheet according to claim 1 or 2, which is for an FPC board.   The copper alloy plate according to claim 3, which is for an FPC board on which LED lighting is mounted. The electronic device component using the copper alloy plate in any one of Claims 1-4 . The FPC which mounted LED lighting using the copper alloy plate in any one of Claims 1-4 .