JPH0351537A - Fine thin spring - Google Patents

Abstract

PURPOSE:To improve workability and suppress the burning loss in shaping and improve corrosion resistance by forming a strand of a fine thin spring from a metal fine thin wire having a wire diameter of 160mum or less or a strength of 300kg/mm<2> or more and forming a Ni plating covered layer on the outer surface. CONSTITUTION:A fine thin spring 4 is formed by winding a metal fine thin wire 5 having a circular sectional surface having a wire diameter of 160mum or less into a coil form having a winding diameter of 1mm or less. The fine thin wire 5 is made of a two-phase structure copper wire containing low carbon and has a tensile strength of 300kg/mm<2> for more. A Ni plating covered layer 6 is formed on the outer surface of the fine thin wire 5. Further, the shape of the sectional surface of the fine thin wire 5 is formed into an ellipse having the spring axis direction as longer axis. Therefore, the workability in wire drawing and coil shaping can be improved. Further, the burning loss in shaping can be suppressed, and the corrosion resistance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a contact probe. Regarding micro springs with a fine winding diameter, which are used in optical sensors, medical equipment, cassette tapes, and supercomputer IC chess cards, etc., and which contribute to the miniaturization of these devices, we are particularly interested in micro springs with a wire diameter of 160μ.
The present invention relates to a structure that can improve the workability when spirally processing an ultra-fine metal wire with a diameter of less than m, suppress the activity of the ultra-fine wire itself, and further prevent the occurrence of rust.

[Conventional technology]

For example, a contact probe for testing electrical current on a printed circuit board has a contact element supported in an elastic state by a fine spring.
The structure is such that this contactor is brought into contact with the portion to be inspected of the circuit pattern. In recent years, with the miniaturization of circuit patterns, there has been a demand for ultra-miniaturization of contact probes, and therefore, there has been an increasing demand for miniaturization of fine springs that elastically support the contacts. For this purpose, it is necessary to reduce the wire diameter to, for example, 160 μm or less while maintaining the tensile strength of the wire.

[Problem that the invention seeks to solve]

However, through experimental research by the present inventors, wire diameter 160
It has been found that the following problems must be solved when using ultrafine metal wires of micrometers or less to form fine springs.

．． It is necessary to improve the workability when drawing a metal wire into the above-mentioned ultra-fine wire and when forming the ultra-fine wire into a coil shape. The reason for this is that the strands are extremely thin, so when spirally processing them into a coil shape, for example, they are susceptible to friction with a certain shape jig, etc., and cannot be shaped into a predetermined shape. This is because it is difficult to process the wire with high accuracy, and as a result, there is a risk that variations in the winding diameter, etc. may occur.

ii. Furthermore, when the metal wire is made ultra-fine, the ratio of surface area to volume becomes extremely large, so the activity of the surface of the ultra-fine wire itself increases abnormally, resulting in, for example, interference with the die during the wire drawing process. Heat is generated due to friction or due to friction during the above-mentioned coil forming process, and in extreme cases, there is a risk of burnout or wire breakage. Therefore, it is necessary to suppress the activity of the ultrafine wire itself.

iii. Furthermore, since the above-mentioned ultra-fine metal wire is made of steel, it is susceptible to rust due to its nature, and furthermore, since it is ultra-fine, if rust occurs, there is a risk that the characteristics will be fatally deteriorated. Therefore, it is necessary to provide corrosion resistance to prevent the occurrence of rust.

In addition, for example, in the case of fine springs used in IC chess cards such as supercomputers, the environmental temperature is approximately 180°C.
Since the temperature may rise to as high as °C, if a fine spring is used in such a high-temperature atmosphere, the spring pressure is likely to deteriorate.
Sustainability of this spring pressure is required.

The purpose of the present invention is to provide a fine spring that can solve the above-mentioned problems when using ultrafine metal wires with a wire diameter of 160 μm or less, and furthermore, to provide a fine spring that can improve the sustainability of spring pressure in a high atmosphere. There is a particular thing.

[Means for solving problems]

Therefore, the invention of item 1 of the present application provides a fine spring formed by winding a wire into a coil shape with a winding diameter of 1n or less, in which the wire is
It is an ultrafine metal wire made of piano wire, stainless steel wire, or low carbon dual-phase steel wire with a wire diameter of 160 μm or less, and is characterized by having a Ni plating coating layer formed on its outer surface. Furthermore, the second feature is characterized in that the cross section of the wire is formed into an elliptical shape so that the major axis is in the direction of the spring axis.

Hereinafter, the reason for adopting the above structure in the present invention will be explained in detail.

■． Reasons why piano wire stainless steel wire or low-carbon dual-phase steel wire with a diameter of 160 μm or less was adopted as the ultra-fine wire The characteristics required of a fine spring are durability, especially fatigue strength.
High resistance to fatigue is required, and for this purpose it is necessary to use strands with excellent tensile strength.To satisfy these characteristics with a wire diameter of 160 μm or less, piano wire and stainless steel wire are required. Alternatively, a low carbon dual phase Mi woven steel wire is optimal. Here, the six ultra-fine wires are low carbon two-phase ms+
If wire is used, the tensile strength can be improved without making the cotton diameter even smaller than piano wire or the like. This low-carbon dual-phase steel wire was researched and developed by the inventors of the present invention, and was achieved by discovering the following points. That is, Fe-C3i-
A steel wire material that is made of an Mn-based iron-based alloy and has a composite metal structure in which a low-temperature transformed biophase consisting of acicular martensite, haynite, or a mixed structure of these is uniformly dispersed in a ferrite phase is excellent in strong processing. Therefore, if a wire having such a metal structure is used, an ultrafine wire with a wire diameter of 100 μm or less can be easily and reliably obtained by cold wire drawing. If such a steel wire rod is subjected to strong processing with a working strain of 4 or more by cold wire drawing, a composite J1 weave (two-phase structure) consisting of the ferrite phase and the low-temperature transformed biophase will be formed in one direction. An elongated, uniform fibrous fine metal structure is formed, and the ultrafine wire with such a metal structure has a tensile strength that is dramatically improved to 303 ky/m'' or more, and has a toughness comparable to that of piano wire or stainless steel wire.

Such a fibrous fine metal wire has a completely new m-weave that has not been known in the past. The present inventors believe that the above-mentioned metal structure is the main cause of improving tensile strength,
As a result of further research into the strengthening mechanism,
In the metal structure having ultra-high strength as described above, the spacing between the fibers is 50 to 1000 cells, and the composite Mi weave in the fibrous form is composed of ultrafine cells of 5 to 100 cells. I found out.

Here, a method for manufacturing the above-mentioned low carbon dual phase steel wire will be explained.

First, C: 0.01-0.5%, Si: 3 in weight%
．． 0% or less, Mn: 5. 0% or less, the balance is Fe and unavoidable impurities, and the wire diameter is 3.5 mm or less.
After being heated to a temperature in the range of 1100'C, it is cooled (this heating and cooling may be performed multiple times) and is made of martensite, haynite, or a mixed structure thereof, which may contain some retained austenite. A wire rod having a composite Mi weave in which a low-temperature transformed phase is uniformly dispersed in a ferrite phase in a volume fraction range of 15 to 75% is manufactured. The above manufacturing method is disclosed in Japanese Patent Application Laid-Open No. 62-2082.
It is described in Publication No. 4.

Next, the thus obtained composite textured wire rod is subjected to strong processing by cold wire drawing to a working strain of 4 or more, preferably 5 or more, to combine the ferrite phase and the low-temperature transformed biophase, and to form a metal. A fine fibrous Mi weave is formed that extends continuously in one direction.

By increasing the degree of processing in this way, the fibrous structure becomes finer and the fiber spacing becomes narrower, until finally, as mentioned above, the cell size and fiber spacing produced by processing are 5 to 100 and 50 to 50,000,000,000,000,000,000,000,000,000,000 It becomes a fibrous fine metal structure with a thickness of ~1000. Note that in a thin wire obtained by wire drawing with a processing strain of 4 or less, the fibrous structure is still in the process of development and the structure is incomplete, and therefore the strength is low.

■． Reason for forming the Ni-plated coating layer on the outer surface of the ultra-fine wire The reason for forming the Ni-plated coating layer is not only to impart normal properties such as corrosion resistance, but also to impart self-lubricity and suppress activity. This is for the purpose of achieving this goal.

As mentioned above, in wire drawing processing and coil shaping processing,
Processability is low depending on the surface properties of the wire, and this effect is particularly large in the case of ultra-fine wires. On the other hand, Ni on the surface of the wire
By forming a plating coating layer, self-lubricating properties can be imparted to the wire, and the above-mentioned processability can be improved.

In addition, as mentioned above, the above-mentioned ultra-fine metal wire has a very high degree of activity, and there is a risk of it being burned out due to frictional heat during processing.
Research conducted by the present inventors has revealed that the activity of the ultrafine wire itself can be significantly suppressed by forming an Nl plating coating layer. This activity suppression is achieved at the same time as the above-mentioned self-lubricating property is provided, so the effect is great.

The table shows various metals (Ni.Cu, Zn, Cu
-Zn,A+! , Au, Ag, Cr) on the surface (improved die life, rust prevention, oxidation, adhesion,
The results of a comparison of surface treatment properties, corrosion resistance, self-lubricating properties, decorative properties, and electrical conductivity are shown below.

As is clear from the table, N1 has high self-lubricating properties, improves die life, and provides excellent rust prevention. It has high corrosion resistance such as oxidation prevention, and also has high surface treatment properties.

In this way, it can be seen that Ni is the most excellent both comprehensively and in terms of imparting the above characteristics. Therefore, by coating with Ni, it is possible to improve the self-lubricating property when drawing ultra-fine wires and shaping ultra-fine wires into coil shapes, and to suppress abnormalities in the activity level. Can prevent rust from occurring.

The above Ni coating method is electroplating. Wet plating methods such as hot-dip plating, PCD, CVD. Commonly used means such as dry plating methods such as Subanotaling can be employed. Of course, the Ni plating mentioned here includes pure N.
In addition to i, Ni plating alloyed with the metals listed in the table or other metals is also included within a range that does not impede the above-mentioned necessary properties. Regarding the amount of Ni coated on the ultra-fine wire, if it is less than 1 g per 1 kg of the ultra-fine wire, it is difficult to achieve the above-mentioned coating effects, and even if it exceeds 100 g, no improvement in the coating effect can be expected; This is undesirable because it causes secondary disadvantages such as powdering during processing. Therefore, 1 to 1 kg of ultrafine wire
A value within the range of og is appropriate.

Here, it is desirable to apply processing strain to the Ni plating coating layer by plastic working.

This is because the Ni plating coating layer that has just been plated has a bolus shape with countless via holes, so hydrogen generated during the plating process is occluded in the Ni coating layer, or air is trapped in the bolus. As a result, this occluded hydrogen. It is possible that residual air may have a negative impact on quality.

On the other hand, if processing strain is applied to the N1 plating coating layer, the pinholes in the coating layer will be crushed and disappear, and the hydrogen and residual air will be released due to the force and heat during wire drawing. , a good Ni plating coating layer containing almost no hydrogen 5 residual air can be obtained, and the above-mentioned concerns can be resolved.

In addition, in order to formalize the above-mentioned processing distortion, for example, in the manufacturing process of the above-mentioned ultra-fine wire, N is added to the wire before cold wire drawing.
This can be achieved by applying i-plating treatment and then wire drawing.

■． The reason why the cross section of the wire is formed into an elliptical shape is to increase the spring pressure without increasing the winding diameter and to improve the sustainability of this spring pressure. That is, in order to increase the spring pressure and its sustainability in a fine spring,
It is conceivable to increase the tensile strength and elastic modulus by increasing the wire diameter of the strand itself, but there is a limit to this since the winding diameter also increases accordingly. On the other hand, by increasing the section modulus by employing a wire having an elliptical cross section with its major axis in the direction of the spring axis, it is possible to increase the spring pressure and its sustainability without changing the winding diameter. Note that the ratio of the short axis to the long axis in the cross section of the wire is preferably 1:1.3.

[Effect]

According to the molded spring according to the invention of item 1 of the present application, piano wire,
Since a stainless steel wire or a low carbon two-phase steel wire is used, a predetermined tensile strength can be secured with a wire diameter of 160 μm or less. In particular, when the low carbon two-phase structure #iI line is adopted, as explained in the strengthening mechanism above, it is possible to easily obtain a structure with a diameter of 100 μm or less, and a thickness of 300 to 60 μm
It has an ultra-high strength of 0 kgf/m2. Therefore, the tensile strength can be further improved compared to the case of piano wire or stainless steel wire. In addition, since a Ni plating coating layer is formed on the outer surface of the above-mentioned ultra-fine metal wire with a wire diameter of 160 μm or less, self-lubricating properties can be imparted. The processability of spiral processing can be improved when processing. In addition, the shape of the Ni plating coating layer suppresses the activity of the ultrafine wire itself, eliminating the problem of burnout due to heat generation during shaping, and further improving corrosion resistance and preventing the occurrence of rust. .

In addition, in the invention of item 2 of the present application, since the cross-sectional shape of the wire is made into an ellipse shape with the major axis in the direction of the spring axis, the spring pressure can be increased without changing the winding diameter, and the spring pressure can be increased even in a high temperature atmosphere. It is possible to avoid a decrease in the amount of water and improve sustainability.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 are diagrams for explaining a fine spring according to an embodiment of the present invention.

In the figure, reference numeral 1 denotes a contact probe for testing electrical conductivity of a printed circuit board, and this has a contact 3 disposed at the tip of a cylindrical body 2 so as to be able to move forward and backward, and the contact 3 is supported by a narrow spring 4. It is constructed with elastic support.

19 12 The fine spring 4 is made by winding an ultrafine metal wire 5 with a circular cross section and a wire diameter of 160 μm or less into a coil shape with a winding diameter of 1 u or less. The ultrafine wire 5 is made of a low carbon dual-phase steel wire, which contains C: 0.01 to 0.50% and Si
:3. O% or less, Mn: 5. A wire rod with a wire diameter of 3.0 to 6.011 consisting of 0% or less, the balance Fe and unavoidable impurities is made into a wire diameter of 15 to 100 μm by primary heat treatment, primary cold wire drawing, secondary heat treatment, and secondary cold wire drawing. It is manufactured through strong processing. This ultra-fine wire 5 forms a fibrous fine metal structure in which processed cells generated by the above-mentioned strong processing are arranged in a fibrous shape in one direction, and the size of the processed cells is 1. The fiber spacing is 5 to 100 people each. 50-1000 people,
Furthermore, the tensile strength is 300 to 600 kgf/m''.

The outer surface of the ultrafine wire 5 is coated with a Ni plating layer 6.
is formed. This Ni plating coating layer 6 is plastically worked at the same time when the wire rod is plated and then subjected to cold wire drawing, and thus has a working strain. That is, the above-mentioned Ni plating coating layer 6 is formed by plating the wire rod in the pre-drawing step 14 to form a coating layer of about 4 μm, and then applying this to the primary coating layer. 1μm by secondary cold drawing
It is made by stretching it to a certain thickness. As a result, the pinholes created during the plating process are crushed, resulting in a good coating layer with no defects.

As described above, according to the fine spring 1 of this embodiment, the fine wire 5 is provided with self-lubricating properties by the Ni plating coating layer 6 formed on the surface. Therefore, workability can be improved when making the wire ultra-fine by wire drawing and when winding this ultra-fine wire into a coil.

Furthermore, by forming the Ni plating coating layer 6,
The activity of the ultra-fine wire itself can be lowered, and burnout or wire breakage due to ripening during processing into a certain shape can be prevented.

Furthermore, the N1 plating improves corrosion resistance and prevents rust from occurring.

Furthermore, in this example, a low carbon dual-phase steel wire is used as the ultra-fine wire 5, so the wire diameter is 10 to 100 μm and the tensile strength is 30.
It has an extremely high strength of 0 to 600 kgf/m2. Therefore, the elastic limit of the fine spring 1 is improved, the fatigue strength and fatigue resistance are improved, and the durability is greatly improved.

Furthermore, in this example, processing distortion was caused in the Ni plating coating layer 6, so that the structure was free of pinholes etc. due to the processing distortion, and since it contained almost no hydrogen or residual air, the quality was improved. can avoid negative effects on

FIG. 3 shows a modification of the fine spring. In this example, the cross-sectional shape of the microscopic wire 5 constituting the microspring 14 is an ellipse in which the ratio of the long axis L in the spring axis direction of the microspring 14 to the short axis l in the direction orthogonal to the axis is 1.3:1. It's in shape.

In this embodiment, the cross section of the ultra-thin wire 5 is made into an ellipse with the major axis in the direction of the spring axis, so that the spring pressure can be increased without changing the winding diameter. Furthermore, the sustainability of this spring pressure can be improved, and deterioration in a high temperature atmosphere can be avoided.

Incidentally, the conditions for a fine spring used in a supercomputer's IC processor are as follows: spring outer diameter 250 μm, spring pressure 30-50 g, spring length 4.5 m, and number of turns 32-1634. In the case of this example, the short diameter of the ultrafine wire is 50 μm. The above conditions can be satisfied by setting the major axis to 60 μm.

In each of the above embodiments, the case where a low-carbon dual-phase steel wire is used as the ultra-fine wire 5 has been explained as an example, but the ultra-fine wire of the present invention can also be a piano wire or a stainless steel wire, and in these cases. By forming the N1 plated coating layer, the activity can be suppressed and self-lubricating properties and corrosion resistance can be improved.

〔Effect of the invention〕

As described above, according to the fine spring according to the invention of item 1 of the present application, N
By forming an i-plated coating layer, it is possible to improve the workability during wire drawing and coil shaping processing, suppress the activity of the ultra-fine wire itself, avoid burnout during shaping, and improve corrosion resistance. It has the effect of improving the rust and preventing the occurrence of rust.
In the invention described in Section 1, the cross-sectional shape of the wire is made into an ellipse shape with the major axis in the direction of the spring axis, so that the spring pressure can be increased without increasing the winding diameter, and the deterioration of the spring pressure in a high temperature atmosphere can be avoided. It has the effect of preventing this and improving sustainability.

1 8

[Brief explanation of drawings]

Fig. 1 fal is a side view showing a fine spring according to an embodiment of the present invention;
The figure is a sectional view showing a modified example of the wire shape. In the figure, 4 and 14 are fine springs, 5 is an ultra-fine wire, and 6 is N
This is an i-plated coating layer.

Claims (2)

[Claims] (1) In a fine spring formed by winding a wire into a coil shape with a winding diameter of 1 mm or less, the wire is a piano wire with a wire diameter of 160 μm or less, a stainless steel wire, or a tensile strength of 300 kg.
1. A fine spring characterized in that it is an ultrafine metal wire made of any of low carbon dual phase steel wires with a diameter of /mm^2 or more, and has a Ni plating coating layer formed on its outer surface. (2) The fine spring according to claim 1, wherein the wire has an elliptical cross section with the major axis in the direction of the spring axis.