JP2009053124A - Contact member and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a durable contact member with improved tribology, especially improved abrasion resistance and to manufacture such a contact member simply/at low cost, with regard to the contact member, such as a probe pin, a contact pin used for detecting or evaluating electric properties of various types of electric equipment and circuits, for example, and its manufacturing method. <P>SOLUTION: In the contact member made by forming a noble metal thin film layer 13 on the surface of a base material 10, super-distribution nano diamond particles with particle size of 2-200 nm are distributed in the grain boundary of the noble metal thin film layer 13 at the ratio of 0.1-2.0 wt.%. When manufacturing such a contact member, the nano diamond particles are distributed in a plating liquid for electroplating, and the nano diamond particles are co-precipitated on the surface of the base material together with noble metals. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a contact member such as a probe pin and a contact pin used for detecting or evaluating electric characteristics of various electric devices and circuits, and a method for manufacturing the same.

  Recently, with the advancement of nanotechnology, ultra-miniaturization technology of integrated circuits has been proceeding with narrowing of the solder ball pitch of BGA (Ball Grid Array) and CSP (Chip Scale Package) packages. Furthermore, due to technological advances such as flip chip and multi-chip modules, there is a need for a technique for evaluating electrical characteristics of wafer level integrated circuits. In order to comply with these narrow-pitch IC test technologies, fine processing technologies for probe pins and contact pins have been required.

  Actually, for example, in the case of a microprobe pin, a microprobe pin is made by inserting a plunger, a spring, a terminal or the like having a length of 1 mm or less into a thin tube having an inner diameter of about 0.1 mm and caulking the tip. Such microprobe pins are mounted on a socket housing in units of several hundreds, and are used when performing electrical measurements several hundred thousand times by repeatedly contacting an electrical terminal such as an IC.

  It is desirable to reduce the electrical resistance of such a probe pin as much as possible. Recently, it has been proposed that the surface of a contact member such as a probe pin is plated with a noble metal such as gold plating as described in Patent Documents 1 and 2 below. However, the precious metal plating as described above is soft, and wears during repeated measurement due to variations in plating quality, etc., resulting in an evaluation error or inability to measure and the socket housing must be rebuilt. , Had a hindrance to productivity.

  In particular, the electrical terminal that contacts the probe pin as described above has recently been used with so-called lead-free tin, and when the probe pin is repeatedly brought into contact with the terminal made of tin, tin will be attached to the probe tip during measurement. Adhere to. In particular, the gold-plated contact member is soft and therefore wears heavily, and tin tends to adhere to the worn portion. For this reason, there are problems such as measurement failure.

Japanese Patent No. 3551411 JP 2005-241362 A

  The present invention has been proposed in view of the above-mentioned conventional problems, and provides a contact member with good durability by improving the tribological characteristics of contact members such as probe pins, particularly wear resistance, and such It is an object of the present invention to provide a contact member manufacturing method capable of easily and inexpensively manufacturing a contact member.

  In order to achieve the above object, a contact member and a manufacturing method thereof according to the present invention are configured as follows. That is, the contact member according to the present invention is a contact member in which a noble metal thin film layer is formed on the surface of a base material, and ultradispersed nanodiamond particles having a particle size of 2 to 200 nm are included in the crystal grain boundaries of the noble metal thin film layer. Dispersed at a ratio of 0.01 to 2.0% by weight.

  As the noble metal constituting the noble metal thin film layer, for example, a single metal of Au, Pt, Ag, Pd, Rh, or Ru or an alloy mainly composed of any metal can be used. The noble metal thin film layer may have a thickness in the range of 0.1 to 5 μm. You may make it provide a smooth layer, a diffusion prevention layer, or both between the said base material and a noble metal thin film layer as needed.

  The contact member manufacturing method according to the present invention is a contact member manufacturing method in which a noble metal thin film layer is formed on the surface of a substrate by electroplating (electrolytic plating). The nano-diamond particles are co-deposited with the noble metal on the surface of the base material by dispersing the particles.

In this case, by controlling the current density in the plating solution when the ultradispersed nanodiamond particles together with the noble metal are co-deposited on the substrate surface, the nanodiamond particles having a predetermined particle diameter can be selectively eutectoid. it can. For example, ultra-dispersed nanodiamond particles having a particle size of 2 to 500 nm are dispersed in the electroplating solution at a concentration of 0.1 to 30 g, preferably 0.5 to 20 g per liter of the plating solution, and the current density is Of 0.02 to 1.0 A / dm ^2, preferably, nanodiamond particles having a particle diameter of 2 to 200 nm can be selectively co-deposited within a range of 0.05 to 0.5 A / dm ^2. it can.

  As described above, the contact member according to the present invention has a ratio of 0.01 to 2.0% by weight of ultradispersed nanodiamond particles having a particle size of 2 to 200 nm in the crystal grain boundary of the noble metal thin film layer formed on the substrate surface. Thus, the tribological characteristics of the noble metal thin film layer of the contact member, particularly the wear resistance, can be improved, and a contact member with good durability can be provided.

  Also, the method for producing a contact member according to the present invention comprises dispersing the ultra-dispersed nanodiamond particles in the plating solution for electroplating when the noble metal thin film layer is formed on the surface of the substrate by electroplating as described above. Since the nanodiamond particles are co-deposited with the noble metal on the surface of the base material, it is possible to deposit the nanodiamond particles in a uniformly dispersed state in the noble metal thin film layer, and the tribological characteristics, particularly wear resistance. Can be manufactured easily and inexpensively.

  Hereinafter, the contact member and the manufacturing method thereof according to the present invention will be specifically described based on embodiments shown in the drawings.

[Contact members]
1A and 1B show an embodiment of a contact member according to the present invention. FIG. 1A is a partially cutaway front view of the contact member, and FIG. 1B is a partially enlarged sectional view of a portion b in FIG.

  In the present embodiment, the contact member is applied to a probe pin for evaluating the electrical characteristics of an integrated circuit such as an IC, in particular, a micro probe pin. The probe pin 1 is guided as shown in FIG. It is provided in the cylinder 2 so as to be able to advance and retreat, and the lower end 1 a side of the probe pin 1 is configured to always protrude from the lower end opening of the guide cylinder 2 by a compression coil spring 3 provided in the guide cylinder 2. . The lower end 1a of the probe pin 1 is repeatedly brought into contact with a terminal or the like not shown in the drawing to measure the electrical characteristics and the like, and the lower end 1a is formed in a crown shape in this embodiment. , Hemispherical, cup-shaped, conical, flat, and other various shapes.

  Further, the probe pin 1 has a configuration in which a noble metal thin film layer 13 is provided on the surface of a base material 10 via a smoothing layer 11 and a diffusion prevention layer 12 as shown in FIG. Ultra-dispersed diamond particles (particularly ultra-dispersed nanodiamond particles) are dispersed in the grain boundaries. The ultra-dispersed nanodiamond particles referred to in the present invention are particles or films having a diamond structure artificially produced by an explosion synthesis method, a static pressure synthesis method, a gas phase method, or the like, sintered, pulverized, and chemically treated. Through a process such as classification, a zeta potential can be obtained by making the surface layer a functional group such as a hydroxyl group, a carboxyl group, or a sulfonic acid group by chemical treatment to have a size of several nanometers to several hundred nanometers. It refers to nano-order fine particles having a diamond structure that are uniformly dispersed in an aqueous solution. Hereinafter, in this document, ultra-dispersed diamond particles including nano-diamonds will be simplified as appropriate and described as UDD.

  As said base material 10, beryllium copper, phosphor bronze, a metal steel material etc. can be used, for example. In this embodiment, a round bar-shaped base material made of beryllium copper is used, and the thickness thereof is appropriate, but in this embodiment, it is formed to a thickness of about 0.3 mm in diameter. In the present embodiment, the smooth layer 11, the diffusion prevention layer 12, and the noble metal thin film layer 13 in which UDD is dispersed are sequentially laminated on the entire surface of the base material 10.

  Prior to forming the noble metal thin film layer 13 on the surface of the base material 10, the smooth layer 11 is provided as necessary to smooth the surface of the base material 10. The forming means is appropriate, but in this embodiment, the surface of the substrate 10 is formed by performing metal plating (electroless plating), particularly nickel plating. Although the thickness of the smooth layer 11 is appropriate, it may be formed to a thickness of about 1 to 5 μm, for example.

  The diffusion prevention layer 12 is provided as necessary to prevent deterioration of the layer structure of the noble metal thin film layer 13 due to generation of an intermetallic compound generated during use as a contact member such as a probe pin. In the present embodiment, the surface of the smooth layer 11 is formed by metal plating, particularly palladium plating. Although the thickness of the diffusion preventing layer 12 is appropriate, for example, it may be formed to a thickness of about 0.1 to 2 μm. Note that the smooth layer 11 and the diffusion preventing layer 12 may be combined with one layer, for example, one metal plating layer in some cases.

  The noble metal thin film layer 13 is provided mainly to increase the conductivity when used as a contact member such as a probe pin and reduce the internal resistance. The material and forming means of the noble metal thin film layer 13 are appropriate. In this embodiment, the surface of the diffusion preventing layer 12 is formed by applying noble metal plating. As the noble metal, for example, a single metal of Au, Pt, Ag, Pd, Rh, or Ru, or an alloy mainly composed of any metal can be used. Among them, gold or a gold alloy is preferable, and as the gold alloy, for example, a gold / cobalt alloy or a gold / nickel alloy containing 90% by weight or more of gold can be used.

  In the crystal grain boundary of the noble metal thin film layer 13, UDD is dispersed as described above, and as the UDD, for example, one generated by an explosion synthesis method or the like can be used. The UDD has a diamond structure in the inner shell and an amorphous carbon in the outer shell, and various functional groups can be modified in the amorphous carbon layer. In addition, the noble metal thin film layer in which the UDD is dispersed uses an ultrafine nanodiamond (UDD) powder having a narrow particle size distribution, and an aqueous suspension having excellent dispersion stability due to the UDD having a zeta potential. This can be achieved by a plating method.

  The UDD has a particle size in the range of 2 to 200 nm. The UDD particle size referred to in the present invention means the particle size of UDD alone when UDD is present alone, and the entire UDD aggregate when it exists as an aggregate. The particle size of The particle size of the UDD is in the above range because if the particle size is less than 2 nm, the effect of improving wear resistance is too small, and if the particle size exceeds 200 nm, it is too large and wears. This is because it may be easy to do. The weight ratio of UDD to the noble metal plating crystal grain boundary is preferably 0.01 to 2.0% by weight, more preferably 0.02 to 1.5% by weight. This is because if the weight ratio of UDD is too small, the effect of improving the wear resistance is small, and even if it is too much, the wear resistance is not so much improved and it is uneconomical.

  Although the thickness of the noble metal thin film layer in which the UDD of the present invention is dispersed is appropriate, it is preferably 100 nm (0.10 μm) to 5000 nm (5.0 μm), more preferably 300 nm (0.30 μm) to 2000 nm (2. 0 μm) is desirable. If the thickness of the noble metal thin film layer is too thin, if UDD larger than that is co-deposited, it will be difficult to maintain UDD in the layer without increasing the mechanical strength of the layer. It becomes easy to detach | leave from a layer inside, and since the detach | leaved UDD acts as an abrasive | polishing agent, it becomes a reverse effect. On the other hand, a thick noble metal thin film layer, for example, one having a thickness exceeding 5.0 μm can be formed by plating or electroforming for a long time. However, if it is too thick, it takes time and costs increase. This is because it is not always a good idea to make it too thick from the viewpoints of cost reduction and environmental conservation. The above layer thickness can be easily measured by, for example, taking an SEM image and analyzing the image.

  The above-mentioned noble metal constituting the noble metal thin film layer in which UDD is dispersed according to the present invention can easily control the UDD eutectoid size and eutectoid position by electrolytic plating, and can include tribology by including UDD. Since the characteristics, particularly the wear resistance strength, are remarkably improved, it is practical as a contact member such as a probe pin.

  Since this UDD is uniformly and sufficiently dispersed in the noble metal thin film layer, its appearance can hardly be visually confirmed and hardly touched. Therefore, tribological characteristics can be improved without deteriorating functional properties such as electrical conductivity and corrosion resistance.

[Method of manufacturing contact member]
Next, a method for manufacturing the contact member such as the probe pin as described above will be specifically described. In order to manufacture a contact member such as a probe pin as shown in FIG. 1, UDD is dispersed in a plating solution when the noble metal thin film layer 13 is formed by electroplating, and the UDD together with the noble metal is formed on the surface of the base material. To eutectoid.

  The electroplating may be electrolytic plating, electroforming, or the like, and it is preferable to use an aqueous suspension in which UDD is uniformly dispersed as the plating solution. As a basic advantage, UDD exhibits excellent dispersion stability when used as a suspension, particularly an aqueous suspension.

  The concentration of UDD per liter of the plating solution in the UDD aqueous suspension is preferably 0.1 to 30 g, preferably about 0.5 to 20 g. It is clear that such a UDD concentration can be adjusted very easily in view of the above-mentioned concentration of the UDD suspension preferably used in the present invention.

  When the concentration of the plating solution is low, precipitation of UDD is avoided by gas bubbles generated in the vicinity of the electrode during the plating process, and precipitation is more reliably avoided by agitation usually applied during the plating process. . The thickness of the plating layer depends on the plating conditions, the purpose of use of the plating layer and the material of the substrate, but is usually in the range of 0.1 to 5 μm, preferably 0.3 to 2.0 μm as described above. For example, in the case of gold plating in the case of electrolytic plating, it is about 0.1 to 1 μm.

  Usually, when UDD is added to the plating solution, a UDD aqueous suspension is used. UDD is dispersed in an aqueous solution to maintain a zeta potential. Therefore, the addition of a surfactant into the UDD aqueous suspension is not essential. The UDD aqueous suspension preferably used in the present invention can typically be suitably used for, for example, electroplating. If the dispersibility of UDD and plating solution is good, a surfactant in the plating solution is used. Is not necessary. If the dispersibility between UDD and plating solution is not good, the dispersion stability of UDD in the plating solution can be maintained by selecting an appropriate surfactant.

  The amount of UDD added per liter of plating solution is 0.1 to 30 g, preferably 0.5 to 20 g. If the concentration of UDD is too low, it is difficult to contain an amount of UDD sufficient to improve the characteristics of the plated noble metal film in the noble metal thin film layer. Because there is no.

Further, by controlling the current density in the plating solution when the UDD is co-deposited on the substrate surface together with the noble metal, UDD having a predetermined particle size can be selectively co-deposited. Specifically, for example, ultra-dispersed nanodiamond particles having a particle size of 2 to 500 nm are dispersed in the plating solution at a concentration of 0.1 to 30 g, preferably 0.5 to 20 g per liter of the plating solution, and the current density is set. In the range of 0.02 to 1.0 A / dm ² , preferably 0.05 to 0.5 A / dm ² , thereby selectively eutecting nanodiamond particles having a particle diameter of 2 to 200 nm. be able to. When the current density is within the range of 0.02 to 1.0 A / dm ² , preferably 0.05 to 0.5 A / dm ² , the plating solution is less than 0.02 A / dm ² The electric field inside becomes weak and it becomes impossible to control the UDD deposition size. When the electric field exceeds 0.5 A / dm ² , the electric field is too strong and the probability that UDD of 200 nm or more is deposited increases. This is because if the current exceeds 1.0 A / dm ² , an excessive current flows into the plating bath, so that the plating solution is broken or the plating layer is abnormally deposited.

  Hereinafter, a specific embodiment assuming the case of manufacturing a probe pin as shown in FIG. 1 and a specific embodiment actually manufacturing a contact pin will be described.

  The plating solution for forming the noble metal thin film layer 13 of the contact member has a UDD concentration as described above, that is, a concentration of 0.1 to 30 g, preferably 0.5 to 20 g per liter of the plating solution. Add UDD. In the case of gold plating, the UDD concentration in a typical 1 liter plating solution of the present invention is preferably 1 g or more practically.

[Example 1]
A noble metal thin film layer in which UDD is dispersed after a smooth layer is formed on the surface of a substrate made of a metal plate made of the same material as that of the base material 10 in the case of manufacturing a probe pin as shown in FIG. Formed. The diffusion preventing layer 12 in FIG. 1 is omitted. As UDD to be dispersed in the noble metal thin film layer, nano-sized super-dispersed diamond particles produced by an explosion synthesis method were used.

  The center of the single particle of the UDD is a very hard diamond nucleus (SP3 structure), and the periphery thereof is a carbon amorphous (SP2 structure). This UDD is chemically washed after the explosion synthesis, and various functional groups (for example, carbolsyl group, ester group, etc.) can be modified on the carbon non-crystalline outer shell. This functional group has a zeta potential, UDD exhibits hydrophilicity and can be dispersed in water.

  FIG. 2 shows the relationship between pH and Zeta potential during UDD water dispersion. In general, it is said that the zeta potential can be stably dispersed if it is ± 30 mV or more in an aqueous solution. The UDD has a zeta potential of about +30 mV when the pH is low at 0 near pH 7 and about -40 mV when the pH is high, indicating that the UDD can stably disperse water on the acidic side and the alkaline side. .

A plurality of kinds of UDD-added gold platings, wherein the above-mentioned suspended aqueous solution of UDD (5% by weight) is added to a glossy pure gold plating solution having the following composition and added in a predetermined amount within a UDD concentration range of 0 to 30 g / L. A liquid was created. The pH of the glossy pure gold plating solution was 4.0.
KAu (CN) ₂ : 15 g / L,
K ₃ C ₆ HO ₇ · H ₂ O: 14 g / L,
_{H 3 CH 5 O 7 · H} 2 O: 36g / L

  After adding UDD to the gold plating solution, the UDD-added gold plating solution was subjected to an ultrasonic homogenizer to further disintegrate and disperse the UDD in the gold plating solution.

  On the other hand, as described above, beryllium copper made of the same material as the base material 10 of FIG. 1 was used as described above, and the substrate was degreased and washed with alkali, and then activated. On the surface of the substrate, a smoothing layer was formed in advance by plating with an electroless Ni plating solution at 90 ° C. for 10 minutes. The thickness of the smooth layer was about 2 to 3 μm. Although the surface of the substrate was very rough at first, it was considerably smoothened by the smooth layer. After the smooth layer was formed, it was washed and subjected to activation treatment with 5% HCl, and then washed again.

A substrate having a smooth layer formed in advance as described above is subjected to UDD eutectoid gold plating using the above-mentioned UDD-added gold plating solution, and an anode in which platinum is plated on a titanium mesh at a thickness of 2 μm. The substrate on which the smooth layer was formed was attached to the cathode. As the plating conditions, two kinds of cases were carried out: the case where the current density in the plating solution was 0.05 A / dm ² and the case where the current density was 0.5 A / dm ^{2. The} distance between the electrodes was 40 mm, and the plating solution temperature was 50. Set to ° C. A noble metal thin film layer made of gold plating having a plating thickness of about 1 μm was formed on the smooth layer with a plating time of 15 minutes. At that time, the UDD having a gold complex ion and a positive zeta potential was attracted to the cathode side, and the UDD could be co-deposited in the gold plating layer.

  Table 1 below shows the relationship between the amount of UDD added in the gold plating solution and the carbon concentration in the noble metal thin film layer (gold plating layer) when the noble metal thin film layer is formed. The carbon concentration was measured by dissolving the sample substrate and the smooth layer in the experiment this time with an ammonium persulfate solution to form only a noble metal thin film layer. Further, a trace amount analysis of carbon content was performed on each noble metal thin film layer using a combustion type carbon concentration measuring device when a plurality of types of UDD-added gold plating solutions added with a predetermined amount within a range of 0 to 30 g / L of UDD concentration were used. .

  As apparent from Table 1 above, the carbon concentration increases as the amount of UDD added increases, the UDD concentration is 0.1 g / L, and the carbon concentration in the noble metal thin film layer is about 0.01% by weight, 0%. About 0.02% by weight at 0.5 g / L, about 1.5% by weight at 20 g / L, and about 2.0% by weight at 30 g / L were detected. This measured carbon concentration is equivalent to the UDD content.

FIG. 3 is a cross-sectional photograph of a layer plated with gold on a copper substrate with a UDD addition concentration of 1.9 g / L and a current density of 0.05 A / dm ² by a FE-SEM backscattered electron image at a magnification of 90,000 times. The white matrix portion is gold-plated, and the black dots are carbon or UDD. Since it is taken with a backscattered electron image, the shade on the white matrix is each gold crystal particle, and UDD of several nanometers to several tens of nanometers is mainly segregated at the grain boundary of gold. Recognize. The UDD grain size was 50 nm or less at most, and many were present at 10 nm or less, and they were uniformly dispersed on the grain boundaries in the layer.

FIG. 4 is a cross-sectional photograph of a FE-SEM backscattered electron image of 50,000 times that of a gold-plated layer on a beryllium copper substrate with a UDD addition concentration of 1.9 g / L and a current density of 0.5 A / dm ² . The UDD grain size was 200 nm or less at maximum, and was present in the layer as one large crystal grain, not a grain boundary.

  Using the image analysis type particle size distribution measurement program, the particle size distribution of UDD particles co-deposited in the noble metal thin film layer was measured from the photographs in FIGS. The size of the particle size was changed to a circle of the same area because the particle was not circular but in an irregular shape, and its diameter was taken as the size of the particle.

FIG. 5 and FIG. 6 are graphs obtained by determining the UDD size distribution in layers plated at current densities of 0.05 A / dm ² and 0.5 A / dm ² , respectively. The horizontal axis indicates the UDD particle diameter (in nanometers), and the vertical axis indicates the number of particles. It can be seen that finer UDD can be deposited by plating at a lower current density.

  The reason why small UDD can be selectively co-deposited at a low current density is that fine primary particles and agglomerated secondary particles are dispersed with a positively charged zeta potential in the plating solution. When the electric field between the cathodes is small, there is not enough force to attract particles with a large momentum to the cathode side, so that only a small UDD moves selectively to the cathode side. During plating growth, UDD that cannot be the nucleus of crystal growth is pushed out as a foreign substance to the crystal grain boundary, so that fine UDD is segregated to the crystal grain boundary. The UDD segregated at the crystal grain boundary becomes an anchor effect between the crystal grains when a load such as stress is applied to the plating layer, and prevents the crystal grain boundary from sliding, thereby increasing the mechanical strength.

Table 2 below shows the (111) plane and (200) plane of the UDD eutectoid gold plating layer when the current density is 0.05 A / dm ² and the addition amount (addition concentration) of UDD to the gold plating solution is varied. The diffraction intensity ratio is shown. In the diffraction intensity ratio of normal bulk gold that is not plated (standard state in Table 1 below), (111) :( 200) = 100: 52. On the other hand, the diffraction intensity ratio of the gold plating not added with UDD is (111) :( 200) = 8: 100. This shows that the gold plating layer not added with UDD is strongly oriented in the (200) plane. As UDD is added, the peak of (111) becomes stronger, and at the UDD addition concentration of 30 g / L, the (111) :( 200) intensity ratio is reversed, and it can be seen that the standard gold structure is approached.

  When no UDD is added, the noble metal thin film layer is a layer with a strong orientation on the (200) plane, but when UDD is added, the strength of the (111) plane increases and is close to the standard gold bulk crystal structure. It will become. This means that by adding UDD, the crystal structure of the noble metal thin film layer becomes polycrystalline and fine. As the crystal becomes finer, the mechanical strength of the noble metal thin film layer increases.

  However, there is an optimum value for the amount of UDD with respect to the wear resistance, and if the amount of UDD is excessively added, the wear resistance tends to deteriorate. This is because UDD exists in the wear powder generated during wear, and this acts as an abrasive on the contrary.

  FIG. 7 shows the relationship between the UDD addition amount per liter of gold plating solution (g / L) and the half-value width of the X-ray analysis peak of the gold plating layer. In FIG. ) Looking at the change in the half-value width of the diffraction peak, it can be seen that the half-value width of the gold plating layer not added with UDD is 0.56 °, but the half-value width decreases as the addition amount increases. A reduction in the half width means that crystal defects are reduced. The reason why the gold crystal structure and structure of the gold plating layer are reduced in crystal defects due to the addition of UDD is that the fine primary particles of UDD serve as nuclei in the formation of gold crystals and change the crystal structure and structure. It is. UDD which could not be a nucleus in gold crystal formation is discharged as a foreign substance to the crystal grain boundary during the gold crystal growth, and is precipitated at the crystal grain boundary.

Table 3 below shows a UDD-containing gold plating layer formed at a current density of 0.05 A / dm ² by adding UDD within a range of 0 to 30 g / L per liter of plating solution after nickel plating as a smooth layer on the substrate. The UDD content and the wear resistance ratio of each noble metal thin film layer 13 are shown. The wear resistance ratio is determined by measuring the wear resistance characteristics of each of the noble metal thin film layers 13 by ball-on-disk, and taking the ratio to the wear resistance characteristics without adding UDD, that is, the wear resistance characteristics without adding UDD as 1. , And the ratio with it. The evaluation conditions of the ball-on-disk were as follows: the ball was rotated 25,000 times at a 3/16 inch alumina ball, a load of 1 N, and a rotation speed of 50 mm / s. The thickness was accurately measured by non-contact optical interferometry, and the volume of the wear scar was calculated and evaluated.

  As is clear from Table 3 above, the UDD content in the noble metal thin film layer increased as the UDD addition amount increased as in Table 1 above. On the other hand, the wear resistance ratio is slightly better than when UDD is added at 0.1 g / L, which is twice as much as when UDD is added at 0.5 g / L and UDD is not added. The effect of improving wear resistance was observed. When the UDD addition amount is further increased, the wear resistance is further improved, and the wear resistance of the noble metal thin film layer made of the UDD-containing gold plating layer formed by adding 8.3 g / L of UDD is obtained when UDD is not added. It was improved about 23 times.

  However, when UDD is further added in excess of 8.3 g / L, the UDD content increases, but the wear resistance property deteriorates. At 20 g / L, the wear resistance ratio is doubled, and the resistance is 30 g / L. The wear ratio was 1.5 times, and it was found that when the addition amount of UDD was further increased, the UDD content was increased, but the wear resistance ratio was further lowered. The reason why there is an optimum value for the added amount of UDD is that if the added amount of UDD becomes too large, the amount of UDD contained in the wear powder generated when the noble metal thin film layer is worn increases. It is thought to work.

Table 4 below shows the UDD content and wear resistance ratio of each noble metal thin film layer 13 made of a UDD-containing gold plating layer formed in substantially the same manner as in Table 3 except that the current density was 0.5 A / dm ^2. It is.

  Also in Table 4, the UDD content in the noble metal thin film layer increased as the UDD addition amount increased as in Table 3, and the wear resistance ratio showed the same characteristics as in Table 3. In particular, the wear resistance ratio is slightly better than when UDD is added at 0.1 g / L, and about 1.5 when UDD is added at 0.5 g / L and UDD is not added. Doubled improvement in wear resistance was observed. When the UDD addition amount is further increased, the wear resistance is further improved, and the wear resistance when the UDD addition amount is 14.4 g / L is about 7 times that of the gold plating layer to which no UDD is added. Improved.

  However, in this case as well, if the addition amount of UDD is further increased beyond 14.4 g / L, the UDD content increases, but the wear resistance gradually decreases, and the wear resistance ratio is 1 at 20 g / L. It was found that when the addition amount of UDD was further increased, the UDD content was increased, but the wear resistance ratio was further decreased. As described above, the reason why there is an optimum value for the UDD addition amount is that if the UDD addition amount is too large as described above, the amount of UDD contained in the wear powder generated when the noble metal thin film layer is worn increases. On the contrary, it is considered to work like an abrasive.

  As described above, the wear resistance of the gold-plated layer was improved by eutectoid rather than by adding UDD, that is, by not causing UDD to eutect. In addition, when the current density is reduced and only fine UDDs are evenly deposited on the crystal grain boundaries of the gold plating layer, the current density is increased and the mechanical properties of the gold plating layer are increased rather than eutecting large agglomerated UDDs. It was found that the mechanical strength can be increased and the wear resistance can be further improved. It was also found that when the UDD addition amount was increased beyond the optimum value, the wear resistance characteristics gradually decreased.

FIG. 8 shows the amount of UDD added per liter of plating solution (g / L) when gold plating is applied to the substrate when the current density is 0.05 A / dm ² and UDD is not added as a noble metal thin film layer. ) And the coefficient of friction, it can be seen that the coefficient of friction is lower when UDD is added than when UDD is not added, and the coefficient of friction decreases as the amount of UDD added increases. For this reason, for example, in a contact member that is slid in contact with a terminal or the like, sliding resistance is reduced, and operability, sliding stability, and the like can be improved.

  In addition, the said Example assumes the case where the probe pin as shown in the said FIG. 1 is manufactured, Noble metal thin film layer which disperse | distributes UDD on the surface of the board | substrate which consists of a metal plate of the same material as the said base material 10. As is clear from the above results, the UDD as described above is dispersed not only in the probe pins as shown in FIG. 1 but also in the base material constituting the contact pins and other contact members. When the noble metal thin film layer is formed, the same characteristics can be obtained, and the tribological characteristics of the contact member, in particular, the wear resistance, sliding performance, and durability can be greatly improved.

[Example 2]
In this example, a noble metal thin film layer made of UDD eutectoid gold plating was formed using a contact pin actually used as a base material. As the contact pin, an L-type contact pin 20 manufactured by Sanyu Kogyo Co., Ltd. as shown in FIG. 9 was used. The material used was beryllium copper, and the dimension L in the figure was 3.8 mm, H was 2.6 mm, and the thickness t in the front-rear direction in the figure was 0.15 mm. After the smooth layer 11 similar to that shown in FIG. 1 was formed on the entire surface of the contact pin 20, a noble metal thin film layer 13 made of UDD eutectoid gold plating was formed on the surface. The diffusion preventing layer 12 in FIG. 1 is omitted.

The same UDD suspended aqueous solution (5% by weight) as in Example 1 was added to a glossy pure gold plating solution having the following composition to prepare a UDD-added gold plating solution having a UDD concentration of 8.3 g / L. The pH of the glossy pure gold plating solution was 4.0.
KAu (CN) ₂ : 15 g / L,
K ₃ C ₆ HO ₇ · H ₂ O: 14 g / L,
_{H 3 CH 5 O 7 · H} 2 O: 36g / L

  After adding UDD to the gold plating solution, the UDD-added gold plating solution was subjected to an ultrasonic homogenizer to further disintegrate and disperse the UDD in the gold plating solution.

Next, the contact pin as the base material was washed with acetone and then activated, and immersed in chemical nickel plating at 90 ° C. for 10 minutes to form a smooth layer made of nickel plating having a thickness of 2 to 3 μm. Then, after washing and activation treatment, it was immersed in a strike gold plating solution and subjected to electrolytic plating at a temperature of 40 ° C. and a current density of 5 A / dm ² for 30 seconds to form a diffusion prevention layer made of strike gold plating having a thickness of several tens of nm. . Thereafter, with the gold plating solution to which UDD was added, electrolytic plating was performed at a temperature of 55 ° C. and a current density of 0.05 A / dm ² for 15 minutes to form a noble metal thin film layer made of gold plating in which UDD having a thickness of about 1 μm was co-deposited. . Thereafter, it was washed with water and dried.

  Wear resistance durability evaluation was performed using a contact pin having a noble metal thin film layer made of UDD eutectoid gold plating produced as described above as a test sample (a). As a measuring device, a contact test using a motor type endurance tester in which the end contact portion 20a of the contact pin 20 in FIG. 9 is brought into contact with a gold bump (not shown) on the steel block surface at a speed of 2 reciprocations / second. Went. As a comparative sample with respect to the test sample (a), a contact pin similar to that used in the test sample was used (b) hard gold plating, (c) normal gold plating, and (d) rhodium plating. Each of these samples was incorporated into one evaluation housing, and a contact test was conducted.

  At that time, the contact resistance and the contact load were monitored during the test, and the wear state of the surface of the contact portion 20a of each contact pin 20 was examined using a laser microscope for every fixed number of contacts. In addition, the gold bumps of the mating material were also worn by the wear test, so the contact position was shifted every 50,000 times.

  FIG. 10 is an optical micrograph showing the surface state before the test in the contact portion 20a of each of the samples (a) to (d), and FIG. 11 is the contact portion 20a after the wear test is performed 100,000 times with a load of 50 gf. It is an optical microscope photograph of. As can be seen from these photographs and graphs, the comparative samples (b) to (d) made of hard gold plating, gold plating, and rhodium plating are peeled off and the substrate is worn, whereas the UDD-added gold plating is used. The sample (a) of the present invention was hardly worn.

  FIG. 12 shows each sample (a) to (d) at the time when the contact test was performed 1000 times, 5000 times, 10,000 times, 30,000 times, 50,000 times, 70,000 times, and 100,000 times with a load of 50 gf. Each represents an average contact resistance value of 5 pieces. As can be seen from this graph, compared with the comparative samples (b) to (d), the contact resistance of the sample (a) of the present invention having a noble metal thin film layer made of gold plated with UDD eutectoid is stable even after 100,000 times. It was.

  FIG. 13 is an optical micrograph of each contact portion 20a after 50,000 wear tests when the load value is 100 gf. Similarly, the comparative samples (b) to (d) made of hard gold plating, gold plating, and rhodium plating were all peeled off and the base material was completely worn, but were made of UDD-added gold plating. Sample (a) of the present invention was only partially worn.

  FIG. 14 shows the average contact resistance of each of the samples (a) to (d) at the time when the contact test was performed 1000 times, 5000 times, 10,000 times, 30,000 times, and 50,000 times with a load of 100 gf. It is a representation. As can be seen from this graph, compared with the comparative samples (b) to (d), the contact resistance of the sample (a) of the present invention having a noble metal thin film layer made of UDD eutectoid gold plating was stable even after 50,000 times. .

  As described above, according to the contact member and the manufacturing method thereof according to the present invention, it is possible to greatly improve the tribological characteristics of the contact member, particularly the wear resistance, and to provide a highly durable contact member easily and inexpensively. Therefore, it is effective not only for the probe pin and the contact pin but also for improving the wear resistance and various durability of various contact members. Therefore, it can be used very effectively industrially.

(A) is a front view which shows one Embodiment of the contact member by this invention, (b) is the elements on larger scale of the b section in (a). The graph which shows the relationship between the zeta potential of UDD and pH. The electron micrograph which shows the dispersion | distribution state of UDD in the gold plating layer formed with the current density of 0.05 A / dm < ² >. The electron micrograph which shows the dispersion state of UDD in the gold plating layer formed with the current density of 0.5 A / dm < ² >. Graph showing the dispersion state of the UDD size of the current density of 0.05 A / dm ² gold plating layer formed by. The graph which shows the dispersion | distribution state of UDD size in the gold plating layer formed with the current density of 0.5 A / dm < ² >. The graph which shows the relationship between the amount of UDD addition to a gold plating solution, and the half value width of a gold plating layer. Graph showing the relationship between the friction coefficient of the UDD amount and the current density 0.5A / dm ² gold plating layer formed by in gold plating solution. The front view of the contact pin used in the Example. The microscope picture which shows the surface state before the test in the contact part of a contact pin. The microscope picture of a contact pin contact part after performing a contact test 100,000 times with a load of 50 gf. The graph which shows the relationship between the frequency | count of a contact and a contact resistance value when a contact test is done with a load of 50 gf. The microscope picture of a contact pin contact part after performing a contact test 50,000 times with a load of 100 gf. The graph which shows the relationship between the frequency | count of a contact when a contact test is done by load 100gf, and a contact resistance value.

Explanation of symbols

1 Probe pin (contact member)
DESCRIPTION OF SYMBOLS 1a Lower end 2 Guide cylinder 3 Compression coil spring 10 Base material 11 Smooth layer 12 Diffusion prevention layer 13 Noble metal thin film layer 20 Contact pin (contact member)
20a Contact part

Claims (7)

  In the contact member formed by forming a noble metal thin film layer on the surface of the base material, 0.01 to 2.0% by weight of ultradispersed nanodiamond particles having a particle size of 2 to 200 nm in the crystal grain boundaries of the noble metal thin film layer. A contact member characterized by being dispersed at a rate.   2. The contact member according to claim 1, wherein the noble metal constituting the noble metal thin film layer is made of a single metal of Au, Pt, Ag, Pd, Rh, or Ru or an alloy mainly composed of any of the metals. .   The contact member according to claim 1, wherein a thickness of the noble metal thin film layer is formed within a range of 0.1 to 5 μm.   The contact member according to any one of claims 1 to 3, wherein a smoothing layer and / or a diffusion prevention layer for smoothing the surface roughness of the base material is provided between the base material and the noble metal thin film layer. .   In the method of manufacturing a contact member in which a noble metal thin film layer is formed on the surface of a substrate by electroplating, ultradispersed nanodiamond particles are dispersed in the electroplating plating solution, and the nanodiamond particles together with the noble metal are mixed with the base. A method for producing a contact member, wherein the material surface is eutectoid.   6. The nano-diamond particles having a predetermined particle diameter are selectively co-deposited by controlling a current density in the plating solution when the ultra-dispersed nano-diamond particles are co-deposited on the substrate surface together with the noble metal. The manufacturing method of the contact member of description. In the electroplating plating solution, ultra-dispersed nanodiamond particles having a particle diameter of 2 to 500 nm are dispersed at a concentration of 0.1 to 30 g per liter of the plating solution, and the current density is 0.02 to 1.0 A / dm. 7. The method for producing a contact member according to claim 5, wherein the nanodiamond particles having a particle diameter of 2 to 200 nm are selectively co-deposited within a range of ² .