TWI867723B - Composite clad wire and electrical test probe - Google Patents

Abstract

Provided are a composite clad wire and an electrical test probe made by the composite clad wire. The composite clad wire includes a linear core part and a covering part surrounding the outer peripheral wall of the core part. The composite clad wire has a diameter smaller than 1 mm. The composite clad wire has a transverse section; based on the total area of the transverse section, the core part occupies more than 50% of the total area of the transverse section. In addition, the composite clad wire has an average volume resistivity smaller than 12 μΩ．cm, and the material of the covering part also has an average volume resistivity smaller than 12 μΩ．cm. Further, the material of the core part has a Vickers hardness larger than 300 Hv.

Description

Composite wire and electrical test probe

This invention relates to a composite wire, in particular a composite wire suitable for preparing a probe for testing electronic components; in addition, this invention also relates to an electrical test probe made of the aforementioned composite wire.

The semiconductor industry can be roughly divided into the stages of design, manufacturing, packaging and testing. Given the high cost of wafers, testing is performed after wafer manufacturing and chip packaging. Whether defective chips can be detected and screened out from the production line in real time is very important for controlling the overall production cost. A probe card is essentially a device that electrically connects multiple contact pads to corresponding channels of a test instrument. The test instrument performs its functional tests, especially electrical function tests. Typically, the test head on a probe card includes a large number of contact elements or contact probes, which must be made of alloy wires with good mechanical and electrical properties, and have at least one contact portion for the component under test to correspond to multiple contact pads. For example, the probe directly contacts the pad or bump on the chip to extract the chip signal, and then cooperates with peripheral test instruments and software to achieve the purpose of measurement.

Palladium (Pd) alloys are often used as probe materials for semiconductor wafer testing, post-package testing, or LED chip testing due to their excellent electrical performance and reliability. However, the conductivity of palladium alloys is still lower than that of copper (Cu) alloys. When testing at higher currents, the current resistance of palladium alloy materials will show its disadvantages. Advanced and high-end probe card manufacturers use the micro-electromechanical system (MEMS) process to combine precious metals and non-precious metals to produce composite probes in order to meet the testing requirements under high currents. However, existing composite probes still cannot meet all the requirements.

In view of the defects faced by the existing technology, the purpose of this invention is to provide a composite wire that has good electrical conductivity, high hardness and good wear resistance. Therefore, the probe made of the composite wire is particularly suitable for high-frequency and high-speed high-end chip testing requirements.

Another purpose of this invention is to provide a composite wire with good machinability.

To achieve the above-mentioned purpose, the invention provides a composite wire, which includes: a linear core; and a coating; the coating surrounds the outer peripheral wall of the core. The wire diameter of the composite wire is less than 1 mm, the composite wire has a cross section; based on the overall area of the cross section, the area occupied by the coating is greater than 50%; the average volume resistivity of the composite wire is less than 12 micro-ohm. centimeters (μΩ.cm); the average volume resistivity of the material of the coating is less than 12μΩ. cm; the Vickers hardness of the material of the core is greater than 300Hv.

The composite wire of this invention has the following technical features controlled at the same time: (I) the wire diameter of the composite wire is less than 1 mm, (II) the area occupied by the coating is greater than 50% based on the overall area of the cross section, (III) the average volume resistivity of the composite wire is less than 12 μΩ. cm, and (IV) the average volume resistivity of the material of the coating is less than 12 μΩ. cm, and (V) the Vickers hardness of the core material is greater than 300Hv. Therefore, the composite wire has high conductivity, high hardness and high wear resistance. The probe made of the composite wire can avoid deformation or rapid wear during use, ensuring the service life of the probe. In addition, the probe is more suitable for applications under high current due to its low contact resistance, for example, it can meet the requirements of high-frequency and high-speed high-end chip testing. In addition, by simultaneously controlling the wire diameter of the cross-section of the composite wire and the area ratio of the cladding portion in the cross-section, the composite wire can have good machinability.

According to this invention, the cross section of the composite wire is defined as a cross section perpendicular to the axial direction of the composite wire, so the cross section of the composite wire may be circular or non-circular (for example but not limited to elliptical), rectangular or square, but not limited thereto.

In some embodiments, the cross-section may be circular or non-circular, and in the cross-section of the composite wire, the core may also be circular or non-circular. Preferably, when the cross-section or the core is non-circular, the ratio of the major axis to the minor axis of the non-circular shape may be greater than 1 and less than or equal to 5, but not limited thereto. In these embodiments, the covering portion is annular and surrounds the outer peripheral wall of the core.

Furthermore, when the core is circular or non-circular, the maximum line distance passing through the midpoint of the core is defined as the major diameter, and half of the major diameter is defined as the radius of the core. Preferably, the radius of the core may be greater than 2μm. More preferably, the radius of the core may be 7.5μm to 160μm, but not limited thereto. Even more preferably, the radius of the core may be 30μm to 160μm.

In other embodiments, the cross-section may be square or rectangular, and in the cross-section of the composite wire, the core may also be square or rectangular. Preferably, when the cross-section or the core is rectangular, the ratio of the long side to the short side of the rectangle may be greater than 1 and less than or equal to 5, but not limited thereto. In these embodiments, the covering portion is a rectangular frame and surrounds the outer peripheral wall of the core.

Furthermore, when the core is square or rectangular, the outer periphery of the core has two sets of parallel opposite sides, the longer of the two sets of sides is called the long side, and half of the long side is defined as the half-long side of the core. Preferably, the half-long side of the core can be greater than 2μm. More preferably, the half-long side of the core can be 7.5μm to 160μm, but not limited thereto. Even more preferably, the half-long side of the core can be 30μm to 160μm.

According to this invention, the ratio of the area of the coating portion to the cross-section is commonly known as the coating ratio. Preferably, based on the overall area of the cross-section, the area occupied by the coating portion can be 60% to 90%, but not limited thereto. More preferably, based on the overall area of the cross-section, the area occupied by the coating portion can be 77% to 90%.

According to this invention, the wire diameter of the composite wire refers to the length of the longest axis of the cross section, that is, the diameter of a circle, the long axis of a non-circular shape, the side length of a square, and the long side of a rectangle. Preferably, the wire diameter of the composite wire is 30 micrometers (μm) to 600μm, but not limited thereto. More preferably, the wire diameter of the composite wire is 30μm to 60μm.

According to the invention, when the composite wire and the core are both circular or non-circular, the thickness of the coating is obtained by deducting the radius of the core from half of the diameter of the composite wire. In addition, when the composite wire and the core are both square or rectangular, the thickness of the coating is obtained by deducting half of the long side of the core from half of the diameter of the composite wire. In the cross section of the composite wire, preferably, the thickness of the coating is greater than 5μm, but not limited to this. More preferably, the thickness of the coating is 9μm to 165μm. More preferably, the thickness of the coating is 60μm to 165μm.

In some embodiments, the radius/half-length of the core is equal to the thickness of the cladding. In other embodiments, the radius/half-length of the core is less than the thickness of the cladding.

According to the present invention, the material of the core is not completely the same as the material of the cladding. Preferably, the material of the core includes gold alloy, silver alloy, palladium metal, palladium alloy, copper metal, copper alloy or stainless steel, but is not limited thereto. Specifically, the gold (gold, Au) alloy refers to the gold metal accounting for more than 50 weight percent (wt%) of the total weight of the gold alloy; preferably, the gold alloy may include aluminum (Aluminum, Al), copper, silver (Silver, Ag), magnesium (Magnesium, Mg), zinc (Zinc, Zn), ruthenium (Ruthenium, Ru), cobalt (Cobalt, Co), gallium (Gallium, Ga) or a combination thereof in addition to gold. The silver alloy refers to the silver metal accounting for more than 50wt% of the total weight of the silver alloy; preferably, the silver alloy may contain copper, nickel (Ni), zirconium (Zr), chromium (Cr), aluminum, palladium or a combination thereof in addition to silver. The palladium alloy refers to the palladium metal accounting for more than 30wt% of the total weight of the palladium alloy; preferably, the palladium alloy may contain copper, silver, platinum (Pt), gold, iridium (Ir) or a combination thereof in addition to palladium. The copper alloy refers to the copper metal accounting for more than 50wt% of the total weight of the copper alloy; preferably, the copper alloy may contain tin (Tin, Sn), phosphorus (Phosphorus, P), iron (Iron, Fe), nickel, zinc, beryllium (Beryllium, Be), titanium (Ti), gold, silver, palladium or a combination thereof in addition to copper. More preferably, in the copper alloy, copper accounts for more than 90wt% of the total weight of the copper alloy. In addition, the stainless steel is a chromium-iron alloy; preferably, based on the total weight of the stainless steel, the chromium content is 15wt% to 30wt%, the iron content is 40wt% to 70wt%, and the carbon content is less than 0.2wt%. In addition, the stainless steel may contain nickel, molybdenum (Mo), vanadium (V), titanium, niobium (Nb), manganese (Mn), tungsten (W), aluminum, copper, carbon (C), phosphorus, sulfur (S), silicon (Si), nitrogen (N) or a combination thereof, but is not limited thereto. The stainless steel may be austenite or γ-Fe, ferrite or α-Fe, or martensite stainless steel.

According to the requirements for material properties in different terminal product applications, preferably, the material of the cladding portion includes stainless steel, palladium alloy, nickel alloy, copper alloy or aluminum alloy, but is not limited thereto. The stainless steel may refer to the description of stainless steel in the aforementioned core material. The palladium alloy may refer to the description of palladium alloy in the aforementioned core material. The nickel alloy means that nickel metal accounts for more than 50wt% of the total weight of the nickel alloy; preferably, the nickel alloy may include cobalt, chromium, iron, copper, silicon, carbon, manganese, titanium, tungsten, tantalum (Ta), phosphorus or a combination thereof in addition to nickel. The copper alloy may refer to the description of copper alloy in the aforementioned core material. The aluminum alloy refers to aluminum metal accounting for more than 50wt% of the total weight of the aluminum alloy; preferably, the aluminum alloy may contain silicon, iron, copper, manganese, magnesium, chromium, zinc, vanadium, titanium, zirconium or a combination thereof in addition to aluminum. More preferably, in the aluminum alloy, aluminum accounts for more than 90wt% of the total weight of the aluminum alloy.

Preferably, the Vickers hardness of the core material may be greater than 400Hv, but not limited thereto. More preferably, the Vickers hardness of the core material may be greater than 535Hv, but not limited thereto.

Preferably, the average volume resistivity of the material of the coating portion may be less than 4μΩ.cm, but not limited thereto. More preferably, the average volume resistivity of the material of the coating portion may be less than 2.5μΩ.cm, but not limited thereto.

Preferably, the average volume resistivity of the composite wire may be 1μΩ. cm to 4μΩ. cm or less than 4μΩ. cm, but not limited thereto. For example, the average volume resistivity of the composite wire may be 1.9μΩ. cm to 3μΩ. cm. More preferably, the average volume resistivity of the composite wire is less than 2.5μΩ. cm, but not limited thereto.

In some embodiments, if the coating is to be further prevented from being oxidized, the composite wire may further include a protective layer, which is formed on the outer surface of the coating, that is, the coating is sandwiched between the protective layer and the core. Preferably, the material of the protective layer may include gold, palladium or silver, but is not limited thereto; the protective layer may be formed by an electroplating process or a spraying process. Preferably, in the cross-section of the composite wire, the thickness of the protective layer may be 0.1 μm to 4 μm, but is not limited thereto.

The composite wire of this invention can be produced by some common production methods, but it is not limited to the process exemplified in this manual. For example, the aforementioned production method can be a composite extrusion method (also known as a hot extrusion method; it mainly relies on the friction of the extrusion wheel to extrude the unmelted or semi-melted cladding material onto the surface of the unmelted core), a casting and drawing composite method (it mainly casts the cladding in a molten metal state onto the surface of the core), a core-filling continuous casting composite method (it mainly casts the core material and the cladding material in a molten state first and then Cooling and joining), continuous extrusion and cladding composite method (which mainly involves continuously extruding the semi-molten cladding material and the core material and then joining them), drawing forming method (which mainly involves first assembling the cladding material and the core material and then stretching them mechanically), thin plate cladding core material method (which mainly involves welding the cladding on the surface of the core), electrocasting (electrodeposition on the core material), etc., but not limited to these.

In some embodiments, the aforementioned production method may include a heat treatment step to further adjust the material properties of the composite wire, but is not limited thereto.

This invention also provides an electrical test probe, which is made by subjecting the aforementioned composite wire to surface insulation treatment.

Preferably, the electrical test probe can be a spring probe, a snake probe, a cantilever probe, a contact probe, a wire probe, a MEMS probe, etc., but not limited thereto.

Preferably, when the length of the electrical test probe is 19 mm, the contact resistance between the electrical test probe and the pad or bump can be 30 milliohms (mΩ) to 80 mΩ, but is not limited thereto.

In this specification, the wire diameter of the composite wire, the radius/half-length of the core, the thickness of the coating, the thickness of the protective layer, etc. are all directly measured using a tool microscope. In addition, the average volume resistivity of the composite wire and the average volume resistivity of the material of the coating are calculated based on the resistance of the wire with a length of 30 cm at each wire diameter, and the volume resistivity formula; wherein, volume resistivity = (resistance/measured length) x wire cross-sectional area. The Vickers hardness of the core material is measured under the conditions of a load of 30 grams (g) and a loading time of 10 seconds.

In this manual, if there is no special indication, the range expressed by "a small number to a large number" means that the range is greater than or equal to the small number and less than or equal to the large number. For example: the radius of the core is 7.5μm to 160μm, which means that the radius range of the core is "greater than or equal to 7.5μm and less than or equal to 160μm".

10: Composite wire

11: Coating part

12: Core

13: Protective layer

S: Cross section

D: Line diameter

H1: Thickness of the coating

H2: Thickness of protective layer

r1: Radius of the core

r2: half the length of the core

RM: Microresistance meter

T:Test needle

P: Copper column

Figure 1 is a three-dimensional schematic diagram of one implementation of the composite wire of this invention.

Figure 2 is a schematic diagram of the cross section of the composite wire in Figure 1.

Figure 3 is a schematic diagram of a cross-section of another embodiment of the composite wire of the present invention.

Figure 4 is a schematic diagram of a cross-section of another embodiment of the composite wire of the present invention.

Figure 5 is a schematic diagram of the contact resistance analysis of Analysis 4.

In order to verify the influence of the raw material properties of the core and the coating of the composite wire, the wire diameter of the composite wire and the coating ratio of the coating in the cross section on the composite wire, several composite wires are listed below as examples, and the implementation of the present invention is described in detail. At the same time, several comparative examples are provided as a comparison. A person with ordinary knowledge in the relevant technical field can easily understand the advantages and effects that can be achieved by the present invention through the contents of this specification. It should be understood that the embodiments listed in this specification are only used to illustrate the implementation of this creation, and are not used to limit the scope of this creation. Technical personnel in this field can make various modifications and changes based on their common knowledge without deviating from the spirit of this creation to implement or apply the content of this creation.

Examples 1 to 13: Composite wire

Ingredients description

1. Stainless steel S: contains about 18wt% to 20.0wt% chromium, about 8.0wt% to 12.0wt% nickel, about 2wt% manganese, about 0.08wt% carbon, about 0.045wt% phosphorus, about 0.03wt% sulfur, about 1.0wt% silicon, and the rest is iron.

2. Palladium alloy A: contains about 35.0wt% to 45.0wt% palladium, about 30.0wt% to 40.0wt% silver, and about 20.0wt% to 30.0wt% copper.

3. Palladium alloy B: contains about 45.0wt% to 60.0wt% palladium, about 5.0wt% to 15.0wt% silver, and about 35.0wt% to 45.0wt% copper.

4. Copper alloy I: Contains greater than or equal to 99.5wt% copper and approximately 0.015wt% to 0.04wt% phosphorus.

5. Aluminum alloy I: contains greater than or equal to 98wt% aluminum, about 0.15wt% iron, about 0.20wt% copper, about 0.05wt% manganese, about 0.45wt% to 0.90wt% magnesium, and about 0.20wt% to 0.60wt% silicon.

First, according to the type of core material and its Vickers hardness, the type of coating material and its average volume resistivity shown in Table 1, the composite wires of Examples 1 to 13 are manufactured by a general method for manufacturing composite wires; wherein each composite wire has an average volume resistivity as shown in Table 1, and each composite wire has a wire diameter as shown in Table 1; in the composite wire of each embodiment, in the cross section of the composite wire, the core has a radius as shown in Table 1, and the coating has a thickness and its area ratio (i.e., coating ratio) as shown in Table 1.

For example, please refer to FIG. 1 and FIG. 2 , a composite wire 10 (such as Examples 1 to 13) of one embodiment of the present invention includes a linear core 12 and a cladding 11 surrounding the outer peripheral wall of the core 12. The composite wire 10 has a cross-section S, and the cross-section S of the composite wire 10 is defined as a cross-section perpendicular to the axis of the composite wire 10; the cross-section S is circular, and the cross-section S has a linear diameter D less than 1 mm (i.e., the maximum outer diameter passing through the midpoint of the cross-section S). In the cross-section S of the composite wire 10, the core 12 is also circular and the radius r1 of the core 12 is greater than 10 μm, and the cladding 11 is annular, and the thickness H1 of the cladding 11 is greater than 10 μm. Based on the overall area of the cross-section S, the area occupied by the coating 11 is greater than 50%. As shown in Figure 2, the wire diameter D of the composite wire 10 is equal to twice the sum of the thickness H1 of the coating 11 and the radius r1 of the core 12, that is, D=2 x(H1+r1).

As shown in FIG. 3 , another embodiment of the present invention includes a linear core 12, a cladding 11 surrounding the outer peripheral wall of the core 12, and a protective layer 13 surrounding the outer surface of the cladding 11, from the inside to the outside. In the cross-section S of the composite wire 10, the core 12 is circular and the radius r1 of the core 12 is about 40 μm, while the cladding 11 and the protective layer 13 are both annular; wherein the thickness H1 of the cladding 11 is about 45 μm, and the thickness H2 of the protective layer 13 is about 0.5 μm to 2 μm. Based on the overall area of the cross-section S, the area occupied by the cladding 11 is greater than 50%. As can be seen from Figure 3, the wire diameter D of the composite wire 10 is equal to twice the sum of the thickness H2 of the protective layer 13, the thickness H1 of the coating 11, and the radius r1 of the core 12, that is, D=2 x(H2+H1+r1).

As shown in FIG. 4 , a composite wire 10 of another embodiment of the present invention includes a linear core 12 and a cladding 11 surrounding the outer peripheral wall of the core 12. The composite wire 10 has a cross-section S, which is square. The core 12 in the cross-section S is also square, and the cladding 11 is a rectangular frame. In the cross-section S of the composite wire 10, the cross-section S has a wire diameter D (i.e., the side length of the aforementioned square) less than 1 mm, the half side length r2 of the core 12 is greater than 10 μm, and the thickness H1 of the cladding 11 is greater than 10 μm; based on the entire area of the cross-section S, the area occupied by the cladding 11 is greater than 50%. As can be seen from Figure 4, the wire diameter D of the composite wire 10 is equal to twice the sum of the thickness H1 of the cladding 11 and the half length r2 of the core 12, that is, D=2 x(H1+r2).

Comparative Examples 1 to 2: Palladium Alloy Wire

Comparative Example 1 is a wire made of palladium alloy A, with a wire diameter of 500μm, an average volume resistivity of 11μΩ.cm, and a Vickers hardness of 438Hv. The wire of Comparative Example 2 has the same wire diameter as Comparative Example 1, but is made of palladium alloy B, with an average volume resistivity of 6.5μΩ.cm and a Vickers hardness of 398Hv.

Comparisons 3 to 5: Stainless steel wire

The wires in Comparative Examples 3 to 5 are all made of stainless steel S, but their wire diameters, Vickers hardnesses, and average volume resistivity are shown in Table 1.

Test Example 1: Vickers Hardness Analysis

In this test example, the composite wires of Examples 1 to 13, the palladium alloy wires of Comparative Examples 1 to 2, and the stainless steel wires of Comparative Examples 3 to 5 with a length of 1 cm were first embedded with epoxy resin and hardener; then, an automatic grinder (manufacturer: Struers; model: Tegramin-25) was used to grind the wires with silicon carbide sandpaper of #80, #240, #400, #800, #1000, #1500, #2000, and #3000 in sequence. The samples were ground and then polished to a mirror surface with 1.0μm and 0.03μm aluminum oxide powder solutions to obtain cross-sectional samples of each embodiment and comparative example. The aforementioned samples were sequentially tested for Vickers hardness of the core of each sample using a Vickers hardness tester (manufacturer: Mitutoyo Instrument Co., Ltd., model: 810-353DC) with a load of 30g and a loading time of 10 seconds. The average results were recorded in Table 1 after repeated 5-point measurements.

Test Example 2: Average Volume Resistivity Analysis

In this test example, the coating materials of the composite wires of Examples 1 to 13 with a length of 30 cm were taken as samples, and the resistance of each sample was measured in sequence with a microresistance meter (manufacturer: HIOKI, model: RM-3544); the resistance measurement was repeated 3 times and the average value was taken, and the volume resistivity formula was used to calculate the result, and the results were recorded in Table 1.

Volume resistivity = (resistance/measured length) x wire cross-sectional area.

In addition, the composite wires of Examples 1 to 13, the palladium alloy wires of Comparative Examples 1 to 2, and the stainless steel wires of Comparative Examples 3 to 5 with a length of 30 cm were taken as samples to be tested, and the average volume resistivity of the composite wires of Examples 1 to 13, the average volume resistivity of the palladium alloy wires of Comparative Examples 1 to 2, and the average volume resistivity of the stainless steel wires of Comparative Examples 3 to 5 were obtained using the same analysis method as above, and the results are recorded in Table 1.

Test Example 3: Cross-section morphology analysis of wire

In this test example, a sample with a length of 1 cm was embedded with epoxy resin and hardener, and then ground with #80, #240, #400, #800, #1000, #1500, #2000, and #3000 silicon carbide sandpaper in sequence by an automatic grinder (manufacturer: Struers; model: Tegramin-25). Then, each sample was polished to a mirror surface with a 1.0 μm and 0.03 μm aluminum oxide powder solution, and the cross-section samples of the composite wires of Examples 1 to 13, the palladium alloy wires of Comparative Examples 1 to 2, and the stainless steel wires of Comparative Examples 3 to 5 were obtained. Then, a tool microscope (manufacturer: Lixun Technology Co., Ltd., model: M21G+OP) was used to observe each group of samples, and the radius of the core, the thickness of the cladding, the wire diameter of the composite wire, the area ratio of the cladding in the cross section, and the area ratio of the core in the cross section of each group of samples were obtained; among them, 3 samples were measured for each group of embodiments and comparative examples, and the above average results were recorded in Table 1.

Analysis 4: Contact resistance analysis

Please refer to FIG. 5. In this test example, the composite wires of Examples 7, 9, 10, and 11, the palladium alloy wire of Comparative Example 1, and the stainless steel wire of Comparative Example 3 with a length of 19 mm are taken as representatives. The aforementioned wires are respectively ground into test needles T, and each test needle T is brought into contact with a copper column P (8 mm in diameter, 3 cm in length, 99.999% pure copper, and its surface is polished to a mirror surface). Then, a microresistance meter RM (manufacturer: HIOKI Electric Co., Ltd., model number: RM-3544) is used to clamp the copper column P. One end of the test needle T and one end of the copper column P are further measured to obtain the "test resistance value"; in fact, the "test resistance value" is the sum of the resistance value of the test needle T, the contact resistance value between the test needle T and the copper column P, and the resistance value of the copper column P; however, since the resistance value of the test needle T and the resistance value of the copper column P are more than two orders of magnitude smaller than the " contact resistance value between the test needle T and the copper column P", the "test resistance value" measured by the above-mentioned microresistance meter RM is directly used to represent the " contact resistance value between the test needle T and the copper column P". The test needle T of each set of embodiments and comparative examples is measured 3 times, and the average result is recorded in Table 2.

Analysis 5: Tensile breaking load (Breaking Limit, BL) analysis

In this test example, the composite wires of Examples 7, 9, 10, and 11, the palladium alloy wire of Comparative Example 1, and the stainless steel wire of Comparative Example 3 are used as representatives, and each of the aforementioned wires with a length of 10 mm is used as a sample. Then, each sample is subjected to a tensile tester (manufacturer: Yangyi Technology Co., Ltd., model: QC-H35A2-S01), and the load value at the breaking point of each sample is recorded as the tensile breaking load. After each group is tested 3 times, the average value is taken, and the results are recorded in Table 2. Among them, the test conditions are as follows: the tensile speed is 10 mm/min, and the upper limit of the measurement is 10 kilograms of force (kgf). If the specimen continues to stretch to the upper limit of the load of 10kgf without breaking, it will be recorded as >10kgf.

Analysis 6: Yield load analysis

From the tensile test of the above analysis 5, the load-elongation curve of each sample is obtained, and the yield load is defined by the 0.2% intercept yield load method (Offset yield load) on the load-elongation curve of each sample, that is, a straight line parallel to the elastic deformation area line is drawn from the position of 0.2% elongation on the elongation axis. The above straight line intersects the load-elongation curve at a point, and the load at this point is the yield load. The samples of each group of embodiments and comparative examples are tested 3 times, and the average value of the obtained values is taken, and the results are recorded in Table 2.

Analysis 7: Yang's coefficient analysis

In the tensile test of the above analysis 5, the Young's modulus of each sample is obtained from the slope of the linear region in the elastic deformation region on the strain-stress curve of each sample. The samples of each group of embodiments and comparative examples are tested 3 times, and the obtained values are averaged and the results are recorded in Table 2.

Discussion of experimental results

According to the results in Table 1, it can be seen from the comparison between the composite wires of Examples 1 to 7 and the stainless steel wire of Comparative Example 3 that the composite wires of Examples 1 to 7 and the stainless steel wire of Comparative Example 3 all have high hardness; furthermore, the composite wires of Examples 1 to 7 can significantly reduce the average volume resistivity of the stainless steel wire to 2.0μΩ.cm to 2.2μΩ.cm by having the coating portion with a "coating ratio greater than 50%" (e.g., 77.01% to 80.15%). Compared with the average volume resistivity of the stainless steel wire of Comparative Example 3 (82.8μΩ.cm), the average volume resistivity decreases by more than 97%, which proves that the composite wire of the present invention can indeed have better conductivity while maintaining high hardness.

Similarly, from the comparison between the composite wires of Examples 8 to 11 and the palladium alloy wire of Comparative Example 1, it can be seen that the core of the composite wire can also maintain a hardness equivalent to that of the palladium alloy wire, so it can meet the application specifications of the test probe. Furthermore, the composite wires of Examples 8 to 11 can significantly reduce the average volume resistivity of the palladium alloy wire to 1.9μΩ.cm to 3.0μΩ.cm by having the coating with a "coating ratio greater than 50%" (for example, 60.81% to 88.12%). Compared with the average volume resistivity of the palladium alloy wire of Comparative Example 1 (11μΩ.cm), the average volume resistivity can be reduced by more than 72%, which proves that the composite wire of this invention does have better conductivity.

In addition, from the comparison between the composite wires of Examples 12 to 13 and the palladium alloy wire of Comparative Example 2, it can be seen that the core of the composite wire can also maintain the same hardness as the palladium alloy wire, so it can meet the test probe application specifications. Furthermore, the composite wires of Examples 12 to 13 can significantly reduce the average volume resistivity of the palladium alloy wire to 2.6μΩ. cm to 2.9μΩ. cm by having the coating with a "coating ratio greater than 50%" (for example, 77.56% to 79.34%). Compared with the average volume resistivity of Comparative Example 2 (6.5μΩ. cm), the average volume resistivity can be reduced by more than 55%, which proves that the composite wire of this invention does have better conductivity.

According to the results in Table 2, it can be seen from the comparison between the composite wires of Examples 9 to 11 and the palladium alloy wire of Comparative Example 1 that even though the core of the composite wires of Examples 9 to 11 and the palladium alloy wire of Comparative Example 1 use the same palladium alloy composition and have similar wire diameters, the composite wires of Examples 9 to 11 can have a smaller average volume resistivity at a coating ratio of 60.81% to 88.12%, and maintain their contact resistance and machinability (e.g., tensile fracture load, yield load, and Young's modulus). Similarly, from the comparison between the composite wire of Example 7 and the stainless steel wire of Comparative Example 3, it can be seen that even though the core of the composite wire of Example 7 and Comparative Example 3 use the same stainless steel and have similar wire diameters, the composite wire of Example 7 obviously has a smaller average volume resistivity and contact resistance, and maintains its machinability (e.g., tensile fracture load, yield load, and Young's modulus). This proves that the composite wire of this invention can indeed have better conductivity, wear resistance, and machinability.

In summary, the invention appropriately controls the wire diameter range of the composite wire, the coating ratio of the coating, the average volume resistivity range of the composite wire and the coating, and the Vickers hardness range of the core material, so that the composite wire of the invention has high conductivity, high hardness and high wear resistance. The probe made of the composite wire can avoid deformation or excessive wear during use, ensuring the service life of the probe, and is particularly suitable for high-end chip testing needs under high current.

The above embodiments are only given for the convenience of explanation. The scope of rights claimed by this creation should be based on the scope of the patent application, and is not limited to the above embodiments.

10: Composite wire

11: Coating part

12: Core

Claims (13)

A composite wire, comprising: a core in a linear shape; and a cladding portion, the cladding portion surrounding the outer peripheral wall of the core portion; wherein the wire diameter of the composite wire is less than 1 mm; the composite wire has a cross section; based on the overall area of the cross section, the area occupied by the cladding portion is greater than 50%; the average volume resistivity of the composite wire is less than 4 micro-ohm. cm; the average volume resistivity of the material of the cladding portion is less than 4 micro-ohm. cm. centimeters; the Vickers hardness of the core material is greater than 300 Hv; wherein the material of the core is not completely the same as the material of the cladding; the material of the core comprises a gold alloy, a silver alloy, a palladium alloy, a copper alloy or stainless steel; the material of the cladding comprises stainless steel, a palladium alloy, a nickel alloy, a copper alloy or an aluminum alloy; wherein the gold alloy comprises a gold metal and further comprises aluminum, copper, silver, magnesium, zinc, ruthenium, cobalt, gallium or a combination thereof, The gold metal accounts for more than 50 weight percent of the total weight of the gold alloy; the silver alloy contains silver metal and further contains copper, nickel, zirconium, chromium, aluminum, palladium or a combination thereof, and the silver metal accounts for more than 50 weight percent of the total weight of the silver alloy; the palladium alloy contains palladium metal and further contains copper, silver, platinum, gold, iridium or a combination thereof, and the palladium metal accounts for more than 30 weight percent of the total weight of the palladium alloy; the copper alloy contains copper metal and further contains tin, phosphorus, iron, nickel, zinc, caladium, titanium, gold, silver, palladium or a combination thereof, the copper metal accounts for more than 50 weight percent of the total weight of the copper alloy; The stainless steel contains chromium and iron and further contains nickel, molybdenum, vanadium, titanium, niodium, manganese, tungsten, aluminum, copper, carbon, phosphorus, sulfur, silicon, nitrogen or a combination thereof, based on the total weight of the stainless steel, the chromium content is 15 weight percent to 30 weight percent, the iron content is 40 weight percent The nickel alloy contains nickel metal and further contains cobalt, chromium, iron, copper, silicon, carbon, manganese, titanium, tungsten, tantalum, phosphorus or a combination thereof, and the nickel metal accounts for more than 50 weight percent of the total weight of the nickel alloy; the aluminum alloy contains aluminum metal and further contains silicon, iron, copper, manganese, magnesium, chromium, zinc, vanadium, titanium, zirconium or a combination thereof, and the aluminum metal accounts for more than 50 weight percent of the total weight of the aluminum alloy. The composite wire as described in claim 1, wherein the wire diameter of the composite wire is 30 microns to 600 microns. The composite wire as described in claim 1, wherein the area occupied by the coating portion is 60% to 90% based on the overall area of the cross-section. The composite wire as described in claim 3, wherein the area occupied by the coating portion is 77% to 90% based on the overall area of the cross-section. The composite wire as described in claim 1, wherein in the cross-section of the composite wire, the cross-section is circular or non-circular, and the core is circular or non-circular; wherein the radius of the core is 30 microns to 160 microns. The composite wire as described in claim 1, wherein in the cross-section of the composite wire, the cross-section is circular or non-circular, the core is circular or non-circular, the cladding is annular, and the thickness of the cladding is 9 microns to 165 microns. The composite wire as described in claim 6, wherein in the cross-section of the composite wire, the thickness of the coating portion is 60 microns to 165 microns. The composite wire as described in claim 1, wherein the Vickers hardness of the material of the core is greater than 535 Hv. The composite wire as described in any one of claims 1 to 8, wherein the material of the core comprises the palladium alloy or the stainless steel; wherein the palladium alloy comprises palladium metal, copper and silver, and the content of the palladium metal is 35 weight percent to 60 weight percent based on the total weight of the palladium alloy; the stainless steel comprises chromium, iron, nickel, manganese, carbon, phosphorus, sulfur and silicon, and the content of chromium is 18 weight percent to 20 weight percent, the content of nickel is 8 weight percent to 12 weight percent, the content of manganese is 2 weight percent, the content of carbon is 0.08 weight percent, the content of phosphorus is 0.045 weight percent, the content of sulfur is 0.03 weight percent, the content of silicon is 1.0 weight percent, and the rest is iron. The composite wire as described in claim 9, wherein the material of the coating portion comprises the copper alloy or the aluminum alloy; wherein the copper alloy comprises copper metal and phosphorus, and based on the total weight of the copper alloy, the copper content is greater than or equal to 99.5 weight percent, and the phosphorus content is 0.015 weight percent to 0.04 weight percent; the aluminum alloy comprises aluminum metal, silicon, iron, copper, manganese and magnesium, and based on the total weight of the aluminum alloy, the aluminum content is greater than or equal to 98 weight percent, the iron content is 0.15 weight percent, the copper content is 0.20 weight percent, the manganese content is 0.05 weight percent, the magnesium content is 0.45 weight percent to 0.90 weight percent, and the silicon content is 0.20 weight percent to 0.60 weight percent. A composite wire as described in any one of claims 1 to 8, wherein the composite wire further comprises a protective layer formed on the outer surface of the coating; wherein the material of the protective layer comprises gold, palladium or silver. A composite wire, comprising: a linear core; and a cladding portion, the cladding portion surrounding the outer peripheral wall of the core portion; wherein the wire diameter of the composite wire is less than 1 mm; the composite wire has a cross section; based on the overall area of the cross section, the area occupied by the cladding portion is greater than 50%; the average volume resistivity of the composite wire is less than 12 micro-ohms. cm; the average volume resistivity of the material of the cladding portion is less than 12 micro-ohms. cm centimeters; the Vickers hardness of the core material is greater than 300 Hv; wherein the material of the core is not completely the same as the material of the cladding; the material of the core comprises a palladium alloy or stainless steel, wherein: the palladium alloy comprises palladium metal, copper and silver, and the content of the palladium metal is 35 weight percent to 60 weight percent based on the total weight of the palladium alloy; the stainless steel comprises chromium, iron, nickel, manganese, carbon, phosphorus, sulfur and silicon, and the content of chromium is 18 weight percent to 20 weight percent, the content of nickel is 8 weight percent to 12 weight percent, the content of manganese is 2 weight percent, the content of carbon is 0.08 weight percent, the content of phosphorus is 0.045 weight percent, the content of sulfur is 0.03 weight percent, the content of silicon is 1 .0 weight percent, and the rest is iron; and the material of the coating portion includes copper alloy or aluminum alloy, wherein: the copper alloy includes copper metal and phosphorus, based on the total weight of the copper alloy, the copper content is greater than or equal to 99.5 weight percent, and the phosphorus content is 0.015 weight percent to 0.04 weight percent; the aluminum alloy includes aluminum metal, silicon, iron, copper, manganese and magnesium, based on the total weight of the aluminum alloy, the aluminum content is greater than or equal to 98 weight percent, the iron content is 0.15 weight percent, the copper content is 0.20 weight percent, the manganese content is 0.05 weight percent, the magnesium content is 0.45 weight percent to 0.90 weight percent, and the silicon content is 0.20 weight percent to 0.60 weight percent. An electrical test probe is made by subjecting the composite wire described in any one of claims 1 to 12 to surface insulation treatment.

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