Kelvin test pin for micro bonding pad

Abstract

The invention discloses a Kelvin test pin for a micro bonding pad. The test pin has the advantages that a traditional design thought of two independent test pins and external insulation isolation is abandoned, an integrated double-pin structure is innovatively adopted, the two pins used for current application and voltage measurement are integrated on the same test pin body through the inner U-shaped loop and the outer U-shaped loop, the overall thickness of the whole test pin is controlled to range from 0.2 mm to 0.4 mm, and the test pin has the advantages of being simple in structure, convenient to use and high in reliability. The size of the test pin is matched with the height of the micro bonding pad, an isolation structure does not need to be additionally arranged between the first pin and the second pin, the design and installation problems caused by the fact that the distance between the test pins is too small in a traditional scheme are fundamentally solved, and the test pin can be directly matched with the micro bonding pad with any length and width smaller than 0.4 mm; according to the invention, beryllium copper alloy is integrally formed through a stamping process, surface gold plating treatment is carried out, the whole production process is mechanized and does not depend on manual operation, and compared with a traditional insulating paint coating scheme, tedious procedures such as painting, drying and scraping of redundant coatings are thoroughly omitted.

Description

Technical Field

[0001] This invention relates to the field of Kelvin test probe technology, and more specifically to a Kelvin test probe for micro pads. Background Technology

[0002] In the field of DC resistance testing of semiconductor components, when the resistance of the device under test is in an extremely low range such as micro-ohms, Kelvin testing (also known as four-wire testing) is the core technology for achieving accurate measurement. The core principle of this testing method is to draw two independent pairs of leads from the same pair of pins of the device under test. One pair of leads is used to apply a constant current, while the other pair of leads is used specifically to collect voltage signals. This effectively avoids the interference of lead resistance and contact resistance on the measurement results and ensures the accuracy of low resistance measurement.

[0003] With the rapid development of semiconductor technology, device packaging continues to evolve towards miniaturization and high density. This trend directly leads to the continuous reduction in the size of device pads, while the number of pads increases significantly. In practical applications, when either the length or width of the device pad is less than 0.4 mm, the traditional Kelvin test socket design faces severe challenges and can no longer meet the testing requirements.

[0004] Traditional Kelvin test sockets require two independent test pins at the same pad location to achieve current application and voltage measurement on the same pad. To address the insulation isolation issue of these two test pins, existing technologies mainly employ two solutions: first, using a plastic injection-molded barrier between the two test pins to achieve physical isolation; second, applying insulating varnish to adjacent sides of the test pins to block current interference. However, both solutions have fatal flaws in scenarios with tiny pads.

[0005] For plastic injection molded grid solutions, as the pad size shrinks, the distance between the two test pins must decrease accordingly. This drastically increases the dimensional accuracy requirements of the injection molded grid, leading not only to a significant increase in mold development costs but also to a shortened mold lifespan and reduced production stability due to the overly refined structure, making it unsuitable for large-scale mass production. For insulating varnish coating solutions, which are essentially manual processes, the number of test pins increases with the number of device pads. For example, a common SOT223-3LK test socket contains 16 test pins. Manually applying insulating varnish is not only time-consuming and labor-intensive, but also makes it difficult to control the uniformity of coating thickness and the consistency of insulation performance. The scraping process for excess insulating varnish further increases labor costs and production cycle, which is completely contrary to the mass production nature of the test socket.

[0006] In summary, the semiconductor testing field urgently needs a Kelvin test socket and probe solution that can adapt to tiny pads (length and width ≤ 0.4mm) and balance insulation performance with mass production requirements, in order to solve the bottleneck problems of traditional technologies. Summary of the Invention

[0007] The purpose of this invention is to provide a Kelvin test probe for micro pads in order to solve the above-mentioned problems.

[0008] The present invention achieves the above objectives through the following technical solutions:

[0009] A Kelvin test probe for micro pads includes a test probe body. A first pin for applying current is provided on one side of the bottom end of the test probe body, and a second pin for voltage measurement is provided on the other side of the bottom end of the test probe body. An outer U-shaped loop is installed on the upper side of the first pin, and an inner U-shaped loop is installed on the top of the second pin. The outer U-shaped loop and the inner U-shaped loop are integrally formed. The overall thickness of the test probe body is 0.2-0.4 mm.

[0010] Furthermore, the test probe body is made of beryllium copper alloy.

[0011] By adopting the above technical solutions, beryllium copper alloy is the preferred material in the field of electronic testing. Its conductivity can reach 20%-45% IACS (International Annealed Copper Standard), which can meet the requirements of low resistance transmission in Kelvin testing and reduce current loss. Its elastic limit is as high as 1200-1500MPa, far exceeding that of ordinary brass or phosphor bronze. It can generate stable contact pressure when in contact with the pads and is not easily permanently deformed after being compressed. At the same time, the hardness of beryllium copper alloy (HRC30-40) enables it to withstand frequent mechanical actions, reducing test socket failures caused by wear and breakage of the test probe. Compared with traditional ordinary copper alloy test probes, the application of beryllium copper alloy significantly improves the reliability and service life of the test probe, indirectly reducing the maintenance cost and replacement frequency of the test socket.

[0012] Furthermore, the surface of the test probe body is provided with a gold plating layer.

[0013] By adopting the above technical solution, the gold plating layer has three core advantages: First, extremely low contact resistance. Gold has stable chemical properties and does not easily form an oxide film on its surface. When in contact with the pad, it can form a path that is almost like "direct metal contact," controlling the contact resistance to below the milliohm level and ensuring the accuracy of voltage measurement. Second, excellent corrosion resistance. Gold can resist the corrosion of moisture, sweat, and common chemical reagents in the testing environment, preventing oxidation and rust on the probe surface and extending the effective service life of the test probe. Third, good wear resistance. Although the hardness of gold is lower than that of beryllium copper alloy, the gold plating layer can form a protective layer on the surface of the test probe body, reducing wear caused by repeated contact between the test probe body and the pad, and maintaining stable contact performance. Through gold plating, the measurement accuracy and service life of the test probe body are improved in two ways, ensuring the consistency and reliability of data in mass production testing.

[0014] Furthermore, the highest point of the outer U-shaped loop is the contact area of ​​the pad of the device under test. When a vertically downward pressure is applied, this contact area forms an electrical path with the pad of the device under test.

[0015] By adopting the above technical solution, the external U-shaped loop structure design has dual functions of "positioning" and "elastic buffering": From the positioning perspective, the highest point of the external U-shaped loop forms a clear contact point, which can quickly align with the center area of ​​the pad, avoiding poor contact caused by contact position misalignment; From the elastic perspective, the external U-shaped loop itself has a certain deformation capacity. When the test socket cover applies vertical downward pressure, the external U-shaped loop will produce slight elastic deformation. This deformation will be converted into contact pressure between the test probe body and the pad, ensuring that the two fit tightly and eliminating contact gaps; At the same time, the elastic deformation can buffer pressure impact, avoiding damage to the pad or test probe body due to excessive pressure, which is especially suitable for packaging fragile micro-devices; Compared with traditional straight needle contact, the design of the external U-shaped loop contact area makes the contact pressure more uniform and the contact position more precise, ensuring the stability of the electrical path and providing a basis for the application of constant current and accurate voltage measurement.

[0016] Furthermore, the test probe body is integrally formed by a stamping process.

[0017] By adopting the above technical solution, stamping is a highly efficient means of mass production of metal parts. Its principle is to apply pressure to beryllium copper alloy sheets using a mold, causing plastic deformation and forming an integrated structure containing a first pin, a second pin, an inner U-shaped loop, and an outer U-shaped loop in one step. The advantages of this process are threefold: First, high efficiency; the stamping process can achieve automated continuous production, with a single-shift output of tens of thousands of pieces, far exceeding manual operation. Second, good consistency; the high precision of the mold ensures that the size and shape of each test pin are completely consistent, avoiding individual differences caused by manual operation and ensuring the compatibility of the test socket assembly. Third, low cost; the stamping process does not require complex post-processing steps, and the mold maintenance cost is lower than that of precision injection molds. At the same time, integrated molding reduces component splicing and material loss. Through stamping, the production of test pins is fully adapted to mass production needs, significantly reducing labor and material costs.

[0018] Furthermore, the length or width of the pad of the device under test that is adapted to the test probe body is no greater than 0.4 mm.

[0019] By adopting the above technical solution, as semiconductor device packaging evolves from traditional packages such as SOT223 to miniaturized packages, the pad size continues to shrink. When either the length or width of the pad is less than 0.4mm, traditional test probes, due to the structural limitations of "double needles + insulation," can no longer be arranged in a limited space. The overall thickness of the test probe body in this invention, at 0.2-0.4mm, is highly matched to the size of such tiny pads. Its integrated structure does not require additional insulation space and can be directly installed in a test socket of the corresponding size. From the perspective of adaptation principle, the test probe body... The contact area (the highest point of the outer U-shaped loop) can be optimized according to the pad size to ensure full fit with the pad. At the same time, the nested structure of the inner and outer U-shaped loops controls the spacing between the current pins and voltage pins to 0.1-0.2mm, which meets the loop separation requirements of Kelvin testing without exceeding the size range of the pad. This precise fit solves the industry pain point that micro-pad devices cannot be reliably tested by Kelvin, expands the application scenarios of Kelvin testing technology, and provides the possibility for quality inspection of micro-semiconductor devices such as chips and sensors.

[0020] Furthermore, the Kelvin test socket to which the test probe is adapted includes at least one test probe as described in any one of claims 1-6.

[0021] By adopting the above technical solution, a single test pin body in this invention can achieve the function of two traditional pins. Therefore, the number of pins in the test socket can remain unchanged or be reduced as needed, while eliminating the need for insulating components between test pin bodies. From the perspective of test socket design, the reduction in the number of test pin bodies and the simplification of the insulation structure reduce the complexity of circuit board wiring and reduce the risk of wiring crossing and interference. From the perspective of reliability, the failure rate of the integrated test pin body is much lower than that of traditional combined pin bodies, reducing the problem of scrapping the entire test socket due to the failure of a single test pin body. In addition, the test socket has stronger adaptability. By increasing or decreasing the number of test pins in this invention, it can meet the testing needs of devices with different numbers of pads, improving the versatility and market competitiveness of the test socket.

[0022] Furthermore, the Kelvin test socket is the SOT223-3LK model test socket, and 16 test pins are installed inside the Kelvin test socket.

[0023] By adopting the above technical solution, the SOT223-3LK is a commonly used Kelvin test socket model in the semiconductor testing field, mainly used for testing three-pin devices. In its traditional design, the 16 test pins need to be combined in pairs to achieve Kelvin testing, resulting in a dense pin layout and significant insulation challenges. This invention allows a single test pin to complete a set of Kelvin tests (current + voltage). The configuration of 16 test pins perfectly matches the interface requirements of the SOT223-3LK test socket, eliminating the need for significant modifications to the socket's housing structure and reducing technical upgrade costs. From a practical application perspective… As you can see, the layout of the 16 integrated test probes is simpler, with uniform spacing between the probes, avoiding the localized crowding problem caused by the pairwise arrangement of traditional probes. At the same time, the mechanized production of the test probes ensures the performance consistency of the 16 probes, making the test data repeatability of the test socket for different devices better. For mass production testing scenarios, the demand for the SOT223-3LK test socket is large. The application of the test probes of this invention enables this model of test socket to achieve the triple advantages of "improved accuracy, reduced cost, and reduced failure rate" while maintaining the original interface compatibility, significantly enhancing its market competitiveness.

[0024] The specific working principle is as follows: The device under test (DUT) is placed in the test socket, with the device pads aligned with the highest contact area of ​​the outer U-shaped loop to ensure precise contact. The test socket cover is locked, generating a downward pressure on the DUT, causing the device pads to apply pressure to the outer U-shaped loop. The outer U-shaped loop undergoes elastic deformation, forming a stable contact pressure and ensuring a reliable electrical path between the pads and the test probe body. A constant current is applied to the first pin (current pin) through the test socket's wiring connection. The current flows through the outer U-shaped loop and pads into the DUT, then flows out of the device and through the outer U-shaped loop of another test probe body and the first pin to form a current loop. Simultaneously, the second pin of the test probe body... The voltage pins contact the pads via the inner U-shaped loop, specifically collecting the voltage signal across the pads. Due to the extremely high input impedance of the voltage measurement circuit, almost no current flows through it. Therefore, the collected voltage is only related to the internal resistance of the device under test (DUT) and is not affected by lead resistance or contact resistance. According to Ohm's law (R = U / I), combined with the applied constant current value and the collected voltage value, the DC resistance of the DUT can be accurately calculated, achieving precise measurement of micro-ohm resistance. Throughout the entire operation, the integrated structure ensures effective separation of the current loop and the voltage loop, the outer and inner U-shaped loops guarantee contact stability, and the beryllium copper alloy and gold plating enhance conductivity, ultimately achieving efficient and accurate testing of micro-pad devices.

[0025] The beneficial effects of this invention are as follows:

[0026] 1. This invention abandons the traditional design concept of "two independent test pins + external insulation isolation" and innovatively adopts an integrated dual-pin structure. The two pins used for current application and voltage measurement are integrated into the same test pin body through an inner U-shaped loop and an outer U-shaped loop. The overall thickness of the test pin is controlled between 0.2-0.4mm, which is highly matched with the size of the micro pad. There is no need to set an additional isolation structure between the first and second pins. This fundamentally solves the design and installation problems caused by the small test pin spacing in the traditional solution. It can directly adapt to micro pads with any length and width less than 0.4mm.

[0027] 2. This invention is integrally formed from beryllium copper alloy through a stamping process, with gold plating on the surface. The entire production process is mechanized, eliminating the need for manual operation. Compared with traditional insulating varnish coating solutions, it completely eliminates the tedious processes of painting, drying, and scraping off excess coating. Compared with plastic injection molding barriers, it avoids the development and maintenance costs of precision molds, significantly improves production efficiency, and reduces labor and material costs, perfectly meeting the requirements of the test socket as a mass production testing tool.

[0028] 3. The integrated structure of this invention enables a single test probe to perform the functions of two traditional test probes. Under the same testing requirements, the total number of test probes in the test socket is significantly reduced, which not only reduces the failure rate of the test socket but also simplifies the wiring design of the internal circuit board, reducing the complexity and design difficulty of the circuit board and providing favorable conditions for the miniaturization and high-density design of the test socket. At the same time, the connection structure of the inner U-shaped loop and the outer U-shaped loop ensures stable contact during testing. A reliable path between the pad of the device under test and the test probe can be achieved by vertical downward pressure, ensuring the accuracy of the measurement. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of a Kelvin test probe for micro pads according to the present invention;

[0030] Figure 2 This is a front view of a Kelvin test probe for micro pads as described in this invention.

[0031] The annotations in the attached figures are explained as follows:

[0032] 1. Inner U-shaped loop; 2. Outer U-shaped loop; 3. First pin; 4. Second pin; 5. Test probe body. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings:

[0034] like Figures 1-2As shown, a Kelvin test probe for micro-pads includes a test probe body 5. A first pin 3 for current application is located on one side of the bottom of the test probe body 5, and a second pin 4 for voltage measurement is located on the other side of the bottom of the test probe body 5. An outer U-shaped loop 2 is mounted on the upper side of the first pin 3, and an inner U-shaped loop 1 is mounted on the top of the second pin 4. The outer U-shaped loop 2 and the inner U-shaped loop 1 are integrally formed. The overall thickness of the test probe body 5 is 0.2-0.4 mm. In principle, the core requirement of Kelvin testing is to separate the current loop from the voltage measurement loop to eliminate the influence of lead resistance and contact resistance. In traditional designs, two independent test probes need to be arranged close together on the micro-pad, and additional insulation structures (such as injection-molded grids or insulating varnish) must be provided. The smaller the pad size (length and width ≤ 0.4 mm), the greater the spacing between the test probes. The contradictions in insulation structure become increasingly prominent—injection molding barriers lead to a surge in mold precision requirements, while the application of insulating varnish relies on manual operation; the integrated structure of this invention directly integrates two functional pins into the same test pin body 5. The nested design of the inner U-shaped loop 1 and the outer U-shaped loop 2 achieves both physical separation between the first pin 3 and the second pin 4 and eliminates the need for additional insulation components. Its overall thickness of 0.2-0.4mm is highly matched with the size of the micro pads, allowing for direct bonding to the pads; this design fundamentally solves the problems of "installation difficulties caused by excessively small test pin spacing" and "conflict between additional insulation structure and mass production requirements" in traditional solutions, enabling Kelvin testing to stably adapt to micro pad devices. At the same time, a single test pin body 5 can achieve the function of two traditional pins, reducing the number of pins in the test socket and laying the foundation for miniaturization of the test socket.

[0035] In this embodiment, the test probe body 5 is made of beryllium copper alloy, which is a preferred material in the field of electronic testing. Its conductivity can reach 20%-45% IACS (International Annealed Copper Standard), which can meet the requirements of low resistance transmission in Kelvin testing and reduce current loss. Its elastic limit is as high as 1200-1500MPa, far exceeding that of ordinary brass or phosphor bronze. It can generate stable contact pressure when in contact with the pad and is not easily permanently deformed after being compressed. At the same time, the hardness of beryllium copper alloy (HRC30-40) enables it to withstand frequent mechanical action, reducing test socket failure caused by wear and breakage of the test probe. Compared with traditional ordinary copper alloy test probes, the application of beryllium copper alloy significantly improves the reliability and service life of the test probe, and indirectly reduces the maintenance cost and replacement frequency of the test socket.

[0036] In this embodiment, the surface of the test probe body 5 is coated with a gold layer. The gold plating layer has three core advantages: First, extremely low contact resistance. Gold has stable chemical properties and does not easily form an oxide film on its surface. When in contact with the pad, it can form a path that is almost like "direct metal contact," controlling the contact resistance to below the milliohm level and ensuring the accuracy of voltage measurement. Second, excellent corrosion resistance. Gold can resist the corrosion of moisture, sweat, and common chemical reagents in the testing environment, preventing oxidation and rust on the probe surface and extending the effective service life of the test probe. Third, good wear resistance. Although the hardness of gold is lower than that of beryllium copper alloy, the gold plating layer can form a protective layer on the surface of the test probe body 5, reducing wear caused by repeated contact between the test probe body 5 and the pad, and maintaining stable contact performance. Through gold plating, the measurement accuracy and service life of the test probe body 5 are improved in two ways, ensuring the consistency and reliability of data in mass production testing.

[0037] In this embodiment, the highest point of the outer U-shaped loop 2 is the contact area of ​​the pad of the device under test (DUT). When a vertically downward pressure is applied, this contact area forms an electrical path with the DUT pad. The structural design of the outer U-shaped loop 2 has both "positioning" and "elastic buffering" functions: from a positioning perspective, the highest point of the outer U-shaped loop 2 forms a clear contact point, which can quickly align with the center area of ​​the pad, avoiding poor contact caused by contact position misalignment; from an elastic perspective, the outer U-shaped loop 2 itself has a certain deformation capacity. When a vertically downward pressure is applied to the test socket cover... Under pressure, the outer U-shaped loop 2 will produce a slight elastic deformation. This deformation will be converted into contact pressure between the test probe body 5 and the pad, ensuring that the two fit tightly and eliminating contact gaps. At the same time, the elastic deformation can buffer the pressure impact and prevent excessive pressure from damaging the pad or the test probe body 5, which is especially suitable for packaging fragile micro devices. Compared with the traditional straight needle contact, the design of the contact area of ​​the outer U-shaped loop 2 makes the contact pressure more uniform and the contact position more precise, ensuring the stability of the electrical path and providing a basis for the application of constant current and accurate voltage measurement.

[0038] In this embodiment, the test probe body 5 is integrally formed by stamping. Stamping is an efficient means of mass production of metal parts. Its principle is to apply pressure to the beryllium copper alloy plate through a mold, causing the plate to undergo plastic deformation, and forming an integrated structure including the first pin 3, the second pin 4, the inner U-shaped loop 1, and the outer U-shaped loop 2 in one go. The advantages of this process are reflected in three aspects: First, high efficiency. The stamping process can realize automated continuous production, and the output per shift can reach tens of thousands of pieces, far exceeding manual operation. Second, good consistency. The high precision of the mold ensures that the size and shape of each test probe are completely consistent, avoiding individual differences caused by manual operation and ensuring the compatibility of the test seat assembly. Third, low cost. The stamping process does not require complex post-processing procedures, and the mold maintenance cost is lower than that of precision injection molds. At the same time, the integral molding reduces the splicing of parts and reduces material loss. Through the stamping process, the production of test probes is fully adapted to mass production needs, and labor and material costs are significantly reduced.

[0039] In this embodiment, the test probe body 5 is adapted to the pad of the device under test, the length or width of which is no greater than 0.4 mm. As semiconductor device packaging evolves from traditional packages such as SOT223 to miniaturized packages, the size of the pads is constantly shrinking. When either the length or width of the pad is less than 0.4 mm, traditional test probes, due to the structural limitations of "double needle + insulation," cannot be arranged in a limited space. The overall thickness of the test probe body 5 in this invention, 0.2-0.4 mm, is highly matched to the size of such tiny pads. Its integrated structure does not require additional insulation space and can be directly installed in a test socket of the corresponding size. From the perspective of the adaptation principle, the contact area (the highest point of the outer U-shaped loop 2) of the test probe body 5 can be optimized according to the pad size to ensure full fit with the pad. At the same time, the nested structure of the inner U-shaped loop 1 and the outer U-shaped loop 2 controls the spacing between the current pin and the voltage pin to 0.1-0.2mm, which not only meets the loop separation requirements of Kelvin testing, but also does not exceed the size range of the pad. This precise adaptation solves the industry pain point that micro pad devices cannot be reliably tested by Kelvin, expands the application scenarios of Kelvin testing technology, and provides the possibility for quality inspection of micro semiconductor devices such as chips and sensors.

[0040] In this embodiment, the Kelvin test socket adapted to the test probe includes at least one test probe as described in any one of claims 1-6. A single test probe body 5 in this invention can achieve the function of two traditional probes. Therefore, the number of probes in the test socket can remain unchanged or be reduced as needed, while eliminating the need for insulating components between the test probe bodies 5. From the perspective of test socket design, the reduction in the number of test probe bodies 5 and the simplification of the insulation structure reduce the complexity of circuit board wiring and reduce the risk of wiring crossing and interference. From the perspective of reliability, the failure rate of the integrated test probe body 5 is much lower than that of traditional combined probe bodies, reducing the problem of scrapping the entire test socket due to the failure of a single test probe body 5. In addition, the test socket has stronger adaptability. By increasing or decreasing the number of test probes of this invention, it can meet the testing needs of devices with different numbers of pads, improving the versatility and market competitiveness of the test socket.

[0041] In this embodiment, the Kelvin test socket is an SOT223-3LK model test socket, which contains 16 test pins. The SOT223-3LK is a commonly used Kelvin test socket model in the semiconductor testing field, mainly used for testing three-pin devices. In its traditional design, the 16 test pins need to be combined in pairs to achieve Kelvin testing, resulting in a dense pin layout and difficulty in insulation. In this invention, a single test pin body 5 can complete a set of Kelvin tests (current + voltage). The configuration of 16 test pins perfectly matches the interface requirements of the SOT223-3LK test socket, without the need for significant modifications to the shell structure of the test socket. This invention reduces the cost of technology upgrades. From a practical application perspective, the layout of the 16 integrated test probes is simpler, with uniform spacing between the probes, avoiding the localized crowding problem caused by the pairwise arrangement of traditional probes. Simultaneously, mechanized production ensures the performance consistency of the 16 probes, resulting in better repeatability of test data for different devices. For mass production testing scenarios, the demand for the SOT223-3LK test socket is high. The application of the test probes of this invention enables this model of test socket to achieve the triple advantages of "improved accuracy, reduced cost, and decreased failure rate" while maintaining the original interface compatibility, significantly enhancing its market competitiveness.

[0042] The specific working principle is as follows: The device under test (DUT) is placed in the test socket, with the device pads aligned with the highest contact area of ​​the outer U-shaped loop 2 to ensure precise contact. The test socket cover is locked, generating a vertically downward pressure on the DUT, causing the device pads to apply pressure to the outer U-shaped loop 2. The outer U-shaped loop 2 undergoes elastic deformation, forming a stable contact pressure and ensuring a reliable electrical path between the pads and the test probe body 5. A constant current is applied to the first pin 3 (current pin) through the test socket's wiring connection. The current flows into the DUT through the outer U-shaped loop 2 and the pads, and then flows out of the device, forming a current loop through the outer U-shaped loop 2 and the first pin 3 of the other test probe body 5. Simultaneously, the second pin 4 (voltage pin) of the test probe body 5... The device contacts the pads via an inner U-shaped loop 1, specifically acquiring the voltage signal across the pads. Due to the extremely high input impedance of the voltage measurement circuit, almost no current flows through it. Therefore, the acquired voltage is only related to the internal resistance of the device under test and is not affected by lead resistance or contact resistance. According to Ohm's law (R = U / I), by combining the applied constant current value and the acquired voltage value, the DC resistance of the device under test can be accurately calculated, achieving precise measurement of micro-ohm resistance. Throughout the entire process, the integrated structure ensures effective separation of the current loop and the voltage loop, the outer U-shaped loop 2 and the inner U-shaped loop 1 structure ensure contact stability, and the beryllium copper alloy and gold plating layer improve conductivity, ultimately achieving efficient and accurate testing of micro-pad devices.

[0043] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A Kelvin test probe for micro pads, characterized in that: The test needle body (5) is provided with a first pin (3) for current application on one side of the bottom end, and a second pin (4) for voltage measurement on the other side of the bottom end, the first pin (3) is provided with an outer U-shaped loop (2) on the upper side, the second pin (4) is provided with an inner U-shaped loop (1) on the top end, the outer U-shaped loop (2) and the inner U-shaped loop (1) are integrated structure, the overall thickness of the test needle body (5) is 0.2-0.4mm.

2. The Kelvin test probe for microsolder pads according to claim 1, wherein: The test needle body (5) is made of beryllium copper alloy material.

3. The Kelvin test probe for microsolder pads according to claim 1, wherein: The surface of the test needle body (5) is provided with a gold plating layer.

4. The Kelvin test probe for microsolder pads according to claim 1, wherein: The highest point of the outer U-shaped loop (2) is the contact area of the device pad to be measured, which forms an electrical path with the device pad to be measured when a vertical downward pressure is applied.

5. The Kelvin test probe for microsolder pads according to claim 1, wherein: The test needle body (5) is integrally formed by stamping process.

6. The Kelvin test probe for microsolder pads according to claim 1, wherein: The device pad to be measured adapted to the test needle body (5) has any one dimension of length or width not greater than 0.4mm.

7. The Kelvin test probe for microsolder pads according to claim 1, wherein: The Kelvin test socket adapted to the test needle comprises at least one test needle as claimed in any one of claims 1-6.

8. The Kelvin test probe for microsolder pads according to claim 7, wherein, The Kelvin test socket is SOT223-3LK type test socket, and 16 test needles are arranged in the Kelvin test socket. The Kelvin test socket is SOT223-3LK type test socket, and 16 test needles are arranged in the Kelvin test socket.

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