JP2005317463A - Material and terminal for high frequency signal transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material having a sufficient strength, a superior spring performance, and a superior performance in transmitting high frequency signals to be used for various kinds of parts for electronic equipments, and to provide a terminal made of that material. <P>SOLUTION: This is the material for the high frequency signal transmission, wherein a raw material composed of an alloy which is provided with characteristic relationship between yield strength (YS) 0.2% and electric conductivity (EC) of YS≥-1.25EC+700, and which has a copper plating layer with the thickness of 0.1-5.0 μm on the surface of the raw material, wherein the standard deviation of the thickness of the copper plating layer on the face where the copper plating is applied is σ≤0.5 μm per 1mm<SP>2</SP>, and regarding the surface roughness, the arithmetic average roughness (Ra) is 0.5 μm or less, the maximum height (Ry) is 2 μm or less, and ten-point average roughness (Rz) is 1 μm or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-frequency signal transmission material excellent in sufficient strength and springiness used for various electronic device parts and a terminal processed into a terminal shape using the material.

As electronic components become smaller and lower in profile, electronic component materials are required to be handled with a thin plate thickness and a narrow plate width. In order to reliably transmit and receive signals, it is important to maintain a stable contact pressure in a narrow space. As the operating environment temperature rises, there is an increasing demand for materials with good stress relaxation characteristics. Therefore, in order to maintain a high contact pressure, it is important that the material properties have high strength.
On the other hand, along with the demand for higher strength accompanying the reduction in size and height, the speed of transmission signals has increased, and it has become important to deal with high frequencies in the GHz band. The skin effect is a phenomenon peculiar to high frequency current. The skin effect is a phenomenon in which the current concentrates on the surface layer of the conductor as the frequency increases. Regarding the skin effect, since the loss of current increases in the copper foil for laminated plates, it has been proposed to improve the time and current loss required for signal transmission by adjusting the surface roughness flatly (Patent Document 1, 2).

JP-A-5-55746 JP 2003-31180 A

  Correspondence to the high frequency of current as described above has been demanded not only for materials for laminates but also for materials used for electronic devices such as terminals. For example, the spring material used for high frequency signal transmission / reception parts, such as CPU socket, is mentioned. When high-frequency current flows through the terminal, the current concentrates on the surface due to the skin effect, and the electrical resistance (skin resistance) increases, so the amount of heat generated at the contact surface increases, the material causes stress relaxation, and the contact pressure of the contact This is because it may decrease. In this case, contact failure may be caused. Therefore, the material used for the terminal is required to have higher conductivity. In that respect, the copper foil has a high conductivity, and the copper foil according to Patent Document 1 can be used for high-frequency signal transmission, but the contact pressure of the contact, which is an important characteristic of the connector, is low, and it is for terminals. It cannot be used as a material.

  Accordingly, an object of the present invention is to provide a material having sufficient strength and good spring property for use in various electronic device parts and excellent in high-frequency signal transmission and a terminal processed using the material. There is.

  As a result of diligent research, the inventors have made a material suitable for high-frequency signal transmission by applying copper plating with adjusted surface roughness to a metal material for electronic device parts having sufficient strength and good springiness, and its material I found a terminal made of materials.

That is, the present invention uses (1) an alloy having a property of YS ≧ −1.25EC + 700 between 0.2% proof stress (YS) and conductivity (EC) as a material, and has a thickness of 0.1 on the material surface. The standard deviation of the thickness of the copper plating layer per 1 mm ² is σ ≦ 0.5 μm on the plated surface having a copper plating layer of ˜5.0 μm, and the arithmetic average of the surface roughness A high-frequency signal transmission material, characterized in that the roughness (Ra) is 0.5 μm or less, the maximum height (Ry) is 2 μm or less, and the ten-point average roughness (Rz) is 1 μm or less,
(2) The material for high-frequency signal transmission according to (1) above, wherein cold rolling and annealing are performed at least once after copper plating,
(3) The high-frequency signal according to any one of (1) to (2) above, wherein the alloy is made of an alloy containing 2.0 to 4.0% by mass of Ti and the balance being Cu and inevitable impurities. Transmission materials,
(4) Ti is 2.0 to 4.0% by mass, and the third element group is 0.01 to 0.50% by mass of one or more of Fe, Co, Ni, Cr, V, Zr, B, and P. The material for high-frequency signal transmission as described in (1) to (2) above, wherein the material is an alloy containing the remaining Cu and the inevitable impurities.
(5) Ni: 2.0 to 4.5% by mass, Si: 0.4 to 1.2% by mass, and an alloy composed of the remainder Cu and inevitable impurities is used as the material The high-frequency signal transmission material according to (1) to (2),
(6) Ni: 2.0 to 4.5 mass%, Si: 0.4 to 1.2 mass%, as the third element group, Mn, Mg, Sn, Ti, Zr, Al, Co, Cr, Fe , Zn, Ag, B, containing 0.003 to 2.0% by mass of one or more of the above, and an alloy composed of the balance Cu and unavoidable impurities as a material (1) ) To (2), a high-frequency signal transmission material,
(7) The material for high-frequency signal transmission according to (1) to (2) above, wherein the alloy material is austenitic stainless steel,
(8) A high-frequency signal transmission terminal obtained by press-punching any one of the high-frequency signal transmission materials according to (1) to (7) into a terminal shape,
(9) After the material described in (1), (3) to (7) above is stamped into a terminal shape, a copper plating layer having a thickness of 0.1 to 5.0 μm is applied to the surface of the material, and the plating is performed. The standard deviation of the thickness of the copper plating layer per 1 mm ² is σ ≦ 0.5 μm on the surface subjected to, and the arithmetic average roughness (Ra) is 0.5 μm or less and the maximum height ( Ry) is 2 μm or less, and ten-point average roughness (Rz) is 1 μm or less.
(10) The high frequency signal transmission terminal according to (8) to (9) above, wherein the applied frequency band is 2 GHz or more,
It is.

  According to the present invention, compared to the prior art, heat generation due to the skin effect during high-frequency energization can be avoided, and a high-frequency signal transmission terminal and material thereof excellent in strength and heat resistance can be obtained.

The reason for limitation will be described below.
(1) One aspect of the invention is to apply copper plating with adjusted surface roughness to a material having sufficient strength and good springiness for use in electronic equipment components. A material obtained by performing copper plating on a metal material used for an electronic device component has existed conventionally as disclosed in, for example, Japanese Patent Laid-Open No. 9-283688. However, the purpose is to improve solderability. It does not give motivation.
Embodiments of copper plating to be provided for high-frequency signal transmission are specifically shown below.

(A) Plating layer thickness As the frequency of the signal increases, the current concentrates on the surface layer, so that the cross-sectional area of conduction decreases and the actual resistance value is higher than the resistance value of the conductor. Therefore, the amount of heat generated on the contact surface layer increases, which may cause contact failure for reasons such as stress relaxation and surface oxidation. Depending on the frequency of the signal, the energization cross-sectional area is reduced by the skin effect, so that only the surface layer that becomes the energization part is subjected to copper plating with good conductivity to suppress heat generation caused by the skin effect and avoid signal delay. Effective plating thickness is 0.1-5.0 micrometers, More preferably, it is 1-3 micrometers. If the thickness is 0.1 μm or less, pinholes are easily formed in the copper plating layer.

  In addition, when the plating thickness is 5 μm or more, it is easy to form electrodeposited grains locally, and thus the distribution of the thickness of the plating layer is likely to be non-uniform, which causes transmission signal delay and noise generation. . In addition, if a plating layer having an excessive thickness with respect to the material plate thickness is formed, the strength of the terminal is reduced by the composite rule, and a target contact pressure cannot be obtained, which is not preferable.

When the standard deviation of the thickness variation per 1 mm ² to which the plating layer is applied is σ ≧ 0.5 μm, a thin region of the plating layer is locally generated. When a high-frequency signal is applied to such a material, stress relaxation occurs in the material due to heat generation due to the skin effect, the contact pressure decreases, and contact failure occurs.

(B) Surface roughness of plating layer (maximum height (Ry) and arithmetic average roughness (Ra), ten-point average roughness (Rz))
As the surface roughness increases, the attenuation of high-frequency signals due to the skin effect becomes more prominent. As a result of analyzing this phenomenon for terminals, each of Ry, Ra, and Rz has an effect on the surface roughness of the plating surface layer before contact insertion as a factor that affects the electrical conductivity after contact insertion. I understood that I should do. That is, Ry is 2 μm or less, Ra is 0.5 μm or less, and Rz is 1 μm or less.
When Ry exceeds 2 μm, Ra exceeds 0.5 μm, and Rz exceeds 1 μm, the thickness of the copper plating layer is unevenly distributed, so that normal signal transmission / reception is impossible for the above reason. In addition, metal powder may be generated at the site where the contact is inserted, causing a short circuit.

(C) Preparation of plating layer In order to control the copper plating layer so as to be in the above range, bath management and material surface roughness are important. From the viewpoint of bath management, uniform electrodeposition at a plating thickness within the range of the present invention can be maintained by using copper sulfate plating in combination with an additive. Since the surface roughness of the material also affects the surface roughness of the plated material, a method for controlling this is also effective. That is, the surface roughness of the work roll of the rolling mill is controlled and transferred to the material, and then the final product surface roughness obtained through mechanical polishing or chemical polishing for the purpose of removing the scale after annealing is desired. What is necessary is just to manage so that it may become smoother than the plating surface roughness.

  Furthermore, in order to control the surface roughness of the plating layer, it is more effective to perform cold rolling on the surface after plating. That is, by adjusting the degree of processing so that the plating surface after cold rolling has a plating thickness and surface roughness within the range of the present invention, pinholes distributed in the plating layer and surface electrodeposited grains can be reduced. Therefore, since the surface roughness can be controlled with high accuracy, the disturbance of the signal waveform can be suppressed and the transmission loss due to the conductor loss can be suppressed. The cold rolling work degree is controlled so that the upper limit of the copper plating layer thickness after rolling is not less than 0.5 μm, and the lower limit is 1% or more as the work degree necessary for the skin pass for smoothing the unevenness of plating. I just need it. On the other hand, when cold rolling is performed, the characteristics of the plating base material such as a decrease in the spring limit value and the formation of a rolled structure change, so that annealing may be required to recover this. The annealing conditions may be performed according to the material characteristics.

  When the plated material is press-punched, there is no copper plating on the end face, and the material is exposed. When the pin width of the terminal is narrow and the plate thickness is thin, since the ratio of the surface area of the portion not subjected to copper plating increases, there is a concern about heat generation due to the skin effect. Therefore, if the plating treatment is performed after pressing, heat generation can be more effectively suppressed.

(2) About alloy material As long as it is a terminal even for high frequency applications, it is necessary to have the characteristics required for the terminal. In order to obtain a sufficient contact pressure as a terminal, strength and springiness are required. It is also important to have conductivity required for normal terminals if it is not always used in a high frequency environment.

Accordingly, it is required to satisfy both high strength and high conductivity, but generally there is a trade-off relationship between 0.2% proof stress (YS) and conductivity (EC) of an alloy.
Therefore, in the present invention, an alloy having a 0.2% proof stress satisfying YS ≧ −1.25EC + 700 between the 0.2% proof stress (YS) and the conductivity (EC) is used as a material. It has been found that a stable contact pressure can be obtained depending on the strength of the material itself, and that this material is suitable for high-frequency transmission by copper plating. Specific alloy materials are listed below.

a) Titanium copper A copper base alloy containing 2.0 to 4.0% by mass of Ti, and one or more of Fe, Co, Ni, Cr, V, Zr, B and P as the third element group Is an alloy for electronic materials having high strength and excellent stress relaxation resistance, and is widely used as a titanium-copper material. When the Ti concentration is higher than the above range, the conductivity is lowered and the conductor resistance value is increased, which is not preferable. Further, when the concentration is low, the strength is insufficient.

b) Cu—Ni—Si-based copper alloy Ni: 2.0 to 4.5 mass%, Si: 0.4 to 1.2 mass%, and the alloy composed of the balance Cu and inevitable impurities is Corson It is called an alloy and has a higher conductivity than the titanium copper, so it is widely used in various electronic component applications. It is also applied as a part of arithmetic system terminals. Ni and Si form an intermetallic compound by performing an appropriate heat treatment, and can increase the strength without deteriorating the electrical conductivity. If the added amount of Ni and Si is less than Ni: 2.0% and Si: less than 0.4%, the desired strength cannot be obtained. If Ni: 4.5% or more, Si: 1.2% or more, the strength is increased. However, the electrical conductivity is remarkably lowered, and the hot workability is further deteriorated. Therefore, the addition amounts of Ni and Si were set to Ni: 2.0 to 4.5% by mass and Si: 0.30 to 1.2% by mass. By adding one or more of Mn, Mg, Sn, Ti, Zr, Al, Co, Cr, Fe, Zn, Ag, and B, high strength can be obtained without impairing electrical conductivity.

c) Stainless steel The general characteristics of austenitic stainless steel are non-magnetic, non-quenching hardenability, excellent corrosion resistance, high strength and tenacity in a wide temperature range from high to low temperature, and molding and welding. It has many features such as easy secondary processing. In particular, the strength is remarkably higher than that of a copper-based alloy used in signal transmission / reception applications, so that a sufficient contact pressure surpassing that of beryllium copper can be maintained even with a thin plate thickness. Moreover, since it is excellent in workability, it is effective as a space-saving terminal material.

(3) The latest CPU may have an operating frequency of 3 GHz or higher, and high frequency characteristics corresponding to the operating frequency are required for computing sockets such as CPU socket applications. In particular, it is required to exert its effectiveness particularly for frequencies of 2 GHz or higher. In particular, terminal materials for sockets have strong demands for high strength and high conductivity to reduce transmission loss as much as possible, and are currently being supported by beryllium copper because of environmental regulations, price, availability, etc. The development of materials with characteristics was awaited.

(1) Example 1
As the alloy material before plating, an alloy having the composition shown in Table 1 was prepared, and annealing and cold rolling were appropriately repeated to obtain a plate material having a thickness of 0.1 mm. For the plating, a copper sulfate bath was used, and after electrolytic degreasing and sulfuric acid pickling, electroplating was performed so as to obtain each plating thickness.
The plating thickness was measured using a fluorescent X-ray film thickness meter, and an average value and a standard deviation were obtained for 10 points measured at 10 mm intervals. The roughness of the plating surface was measured using a surface roughness meter and measured according to JIS-B0601 to measure Ry, Ra, and Rz. The plated material was processed by press punching to a width of 1 mm and a length of 100 mm in the rolling direction, a 2 GHz high frequency signal was applied using a network analyzer, and the temperature change of the material at this time was directly measured using thermography. . For example, since the specification upper limit temperature of the CPU main body is often set around 70 ° C., it is desirable that the temperature rise during operation at the contact portion is less than 30 ° C. with respect to room temperature when a cooling fan is used in combination. .

For the alloys shown in Table 1, 0.2% proof stress and electrical conductivity were measured. Alloys A to E are alloys satisfying claims 3 and 4, Alloys F to K are alloys satisfying claims 5 and 6, and Alloy L is an alloy satisfying claim 7.
Alloys A to M satisfy the relationship of YS ≧ −1.25EC + 700 between the 0.2% proof stress (YS) and the conductivity (EC), and satisfy the characteristics as a terminal. For reference, the alloy N in Table 1 is a copper foil for laminated plates using tough pitch copper, has a low 0.2% yield strength, and is not suitable for a terminal material.
Inventive example No. in which the surface roughness of the materials of the alloys A to M having the composition shown in Table 1 was appropriately controlled and the copper plating conditions were also controlled. 1 to 13 are shown in Table 2. Since the thickness and surface roughness of the copper plating are within the scope of the present invention, the temperature rise of the current-carrying part is small.

  On the other hand, a comparative example is shown in Table 3. The alloy material used is an alloy having the composition shown in Table 1 as in the example. Comparative Example No. In Nos. 14, 21, 22, and 26, when the plating thickness was increased, coarse electrodeposition grains frequently occurred and heat was generated. In Comparative Examples 19 and 22, when the plating thickness was increased, coarse electrodeposition grains were frequently generated, and the variation in the plating thickness was large, and heat was generated. Comparative Example No. 15, 17, 20, 23, and 25 generated heat because the plating was thin. Comparative Example No. No. 16 had a large variation in plating thickness, and the thin plating portion generated heat. In Comparative Examples 18 and 24, the material was soggy, coarse electrodeposition grains were frequently generated, and heat was generated.

(2) Example 2
In the same manner as in Example 1, annealing and cold rolling were repeated as appropriate for each alloy material to form a plate material having a thickness of 0.1 mm, and plating was performed using a copper sulfate bath, electrolytic degreasing, and sulfuric acid pickling, and then plating Electroplating was performed to obtain a thickness.
Comparative Examples No. 1 to No. 4 in which alloys A, B, F, I, L, and M were subjected to copper plating not satisfying the present claims Sample materials 33 to 38 were prepared. Samples obtained by performing cold rolling on these parts and improving the surface roughness were No. 27-32.
The measuring method is the same as that in the first embodiment.

  Invention Example No. shown in Table 4 27 to 32 were out of the scope of the present invention as they were plated with copper, but the surface roughness was improved by performing cold rolling, so the energized part temperature did not increase. On the other hand, Comparative Example No. Since 33-38 was outside the scope of the present invention when copper plating was applied, the temperature of the energized part increased.

(3) Example 3
Invention Example No. 1 produced in Example 1. Nos. 1, 2, 6, 9, 12, and 13 were punched out of the press. 39-44 were produced. On the other hand, Invention Example No. For 45 to 50, alloys A, B, F, I, L, and M were subjected to annealing and cold rolling as appropriate in the same manner as in Example 1 to obtain a plate material having a thickness of 0.1 mm, and a width of 1 mm and a length of 100 mm. After press punching, copper plating was performed. The measuring method is the same as in Example 1.
In addition, invention example No. 45 to 50 are examples satisfying the tenth aspect.

The results are shown in Table 5, all of which control the surface properties within the scope of the present invention and give good results. Invention Example No. In Nos. 45 to 50, if copper plating is performed after press punching, the punching end face can also be subjected to copper plating, so that conductor loss can be reduced and temperature rise can be suppressed.

Claims (10)

A copper plating layer having a thickness of 0.1 to 5.0 μm on the surface of the material made of an alloy having a property of YS ≧ −1.25EC + 700 between 0.2% proof stress (YS) and conductivity (EC) And the standard deviation of the copper plating layer thickness per mm ² is σ ≦ 0.5 μm for the plated surface, and the arithmetic average roughness (Ra) is 0. A high-frequency signal transmission material characterized by having a maximum height (Ry) of 2 μm or less and a ten-point average roughness (Rz) of 1 μm or less, 5 μm or less, a maximum height (Ry) of 2 μm or less.   The material for high-frequency signal transmission according to claim 1, wherein cold rolling and annealing are performed at least once after copper plating.   The high-frequency signal transmission material according to claim 1, wherein the material is made of an alloy containing 2.0 to 4.0% by mass of Ti, and the balance being Cu and inevitable impurities.   Ti is contained in an amount of 2.0 to 4.0% by mass, and the third element group contains 0.01 to 0.50% by mass of one or more of Fe, Co, Ni, Cr, V, Zr, B, and P. The material for high-frequency signal transmission according to claim 1, wherein an alloy composed of the remaining Cu and inevitable impurities is used as a raw material.   Ni: 2.0 to 4.5 mass%, Si: 0.4 to 1.2 mass%, and an alloy composed of the balance Cu and unavoidable impurities is used as a raw material. 2. The high-frequency signal transmission material according to 2.   Ni: 2.0-4.5% by mass, Si: 0.4-1.2% by mass, as the third element group, Mn, Mg, Sn, Ti, Zr, Al, Co, Cr, Fe, Zn, An alloy composed of 0.003 to 2.0% by mass of one or more of Ag and B, the balance being Cu and inevitable impurities is used as a material. The material for high frequency signal transmission as described. The material for high-frequency signal transmission according to claim 1, wherein the alloy material is austenitic stainless steel.   A high-frequency signal transmission terminal obtained by press-punching any one of the high-frequency signal transmission materials according to claim 1 into a terminal shape. After press punching the material according to claim 1, 3 to 7 into a terminal shape, a copper plating layer having a thickness of 0.1 to 5.0 μm is applied to the surface of the material, and the plated surface per 1 mm ² The standard deviation of the copper plating layer thickness is σ ≦ 0.5 μm, and the arithmetic average roughness (Ra) of the surface roughness is 0.5 μm or less, the maximum height (Ry) is 2 μm or less, ten points A high-frequency signal transmission terminal having an average roughness (Rz) of 1 μm or less. The terminal for high frequency signal transmission according to claim 8, wherein the applied frequency band is 2 GHz or more.