Test needle with spring needle and surrounding coil spring for testing device under test

Abstract

A test pin (100) for a test device (102) for electrical contact with a device under test (104) to be tested, the test pin (100) comprising an at least partially electrically conductive spring pin (106) and an at least partially electrically conductive coil spring (110) surrounding the spring pin (106) at least over a majority of a length (1) of the spring pin (106).

Description

Technical Field

[0001] Various embodiments generally relate to test probes, test apparatus, and methods of testing devices under test. Background Art

[0002] After the manufacture of semiconductor chips or packages containing such semiconductor chips is completed, the functionality of such IC (integrated circuit) devices is usually tested. To this end, a test device having one or more test pins is provided, in which such products are tested as devices under test (DUTs).

[0003] However, the technical effort required for this type of testing is significant, as test needles can be subject to wear and require frequent replacement in a tedious and time-consuming process. Furthermore, the reliability and correctness of test results (i.e., DUTs that pass the test are actually acceptable, and DUTs that fail the test are actually unacceptable) still need to be improved. Furthermore, the DUT may still have insufficient electrical performance. Summary of the Invention

[0004] A test probe that can test a device under test with good electrical performance may be required.

[0005] According to an exemplary embodiment, a test pin for a testing device may be provided for electrically contacting a device under test to be tested, the test pin comprising an at least partially conductive spring pin and an at least partially conductive coil spring surrounding the spring pin over at least a majority of the length of the spring pin.

[0006] According to another exemplary embodiment, a test device for electrically testing a device under test may be provided, the test device comprising a substrate and at least one test needle having the above-mentioned features, the test needle being assembled with the substrate and configured to electrically contact the device under test for conducting test signals from and / or to the device under test.

[0007] According to another exemplary embodiment, a method for testing a device under test may be provided, the method comprising: bringing a test needle having the above-mentioned characteristics into contact with a conductive structure of the device under test; applying a test signal as excitation to the conductive structure of the device under test via the test needle; and detecting a response of the device under test to the test signal.

[0008] According to one exemplary embodiment, a test device and a test needle may be provided, wherein the test needle may include a test tip that can be connected to electrically contact a device under test (DUT) and test the DUT. Advantageously, the test needle includes a (e.g., metal) spring pin as a core and a (e.g., metal) coil spring disposed circumferentially around the spring pin, or at least around a substantial portion of the spring pin. Exemplary embodiments may achieve at least one of the following two objectives: On the one hand, the coil spring disposed around the spring pin may provide an extended electrical path for distributing higher currents to the test needle. Thus, the test needle may be able to withstand higher test currents. Given the skin effect, such a test needle may be particularly well-suited for high-frequency applications, as the combination of the spring pin and coil spring may increase the skin area along which current propagates, even at high frequencies. Additionally or alternatively, disposing at least one coil spring around the spring pin in the test needle may advantageously mitigate external electromagnetic interference (EMI) on the inner spring pin. Consequently, such an embodiment may benefit from strong suppression of interfering electromagnetic radiation from the environment.

[0009] Advantageously, a spring pin nested with one or more outer coil springs (which may be wound around a central spring pin) may form a plurality of radially parallel electrical connection structures, optionally in combination with a bundle of brush-like flexible conductors, to achieve a number of advantageous effects: First, a higher current and a larger contact area may be obtained to achieve better current carrying capacity. Furthermore, a larger skin area may be obtained to efficiently address the skin effect, particularly when testing at higher frequencies. In addition, the self-inductance of the test pin may be reduced by providing a plurality of parallel connection structures. Optionally, the contact tip cleaning efficiency may be improved by configuring the test pin to perform a rotational and / or radial scrubbing motion during operation. The optional feature of configuring the test pin to perform a rotational and / or radial scrubbing motion during operation may effectively reduce contamination of the test pin.

[0010] Description of Further Exemplary Embodiments

[0011] In the following, further exemplary embodiments of a test needle, a test device and a method will be explained.

[0012] In the context of this application, the term "device under test" (DUT) may particularly denote an electronic component, such as a semiconductor package, that should be tested for its required functionality after its manufacture. In particular, the DUT may be an electronic component configured as a power semiconductor, in particular for automotive applications. Such a DUT may require electrical testing involving the application of high voltage and / or high current electrical test signals (e.g., application of currents of up to 100 amperes or more).

[0013] In the context of the present application, the term "test pin" may particularly denote an at least partially electrically conductive elongated structure configured for carrying an electrical signal transmitted from the test pin to the device under test, and / or vice versa.

[0014] In the context of the present application, the term "testing apparatus" may particularly denote a device configured for testing a device under test by applying a stimulus signal to one or more test pins and from the one or more test pins to the device under test, and capturing and analyzing electrical response signals from the device under test, for example using the same and / or other test pins.

[0015] In the context of this application, the term "pogo pin" may particularly refer to, for example, a spring-loaded pin that is an electrical connector for testing electronic devices and / or applications. Pogo pins are used for their remarkable durability and the resilience of their electrical connection structure to avoid mechanical shock and vibration.

[0016] In the context of this application, the term "coil spring" may particularly denote an at least partially electrically conductive structure having an elastic element (e.g., a coil, for example a helical coil). A coil spring may provide elastic or springy properties and thus a spring function. For example, a coil spring may be a helically wound filament or wire or a sleeve having a helical recess.

[0017] In the context of the present application, the term "coil spring surrounding the pogo pin at least over a majority of its length" may particularly mean that a portion of the coil spring or the entire coil spring's axial extension overlaps with a portion of the pogo pin or the entire pogo pin's axial extension for more than half the length of the pogo pin, particularly at least 75% of the length of the pogo pin, preferably at least 90% of the length of the pogo pin, and most preferably the entire length of the pogo pin.

[0018] In the context of the present application, the term "substrate" may particularly denote a support or a carrier for a test needle or a plurality of test needles.

[0019] In the context of the present application, the term "test signal" may particularly denote an electrical signal that can be applied by a test device to a test pin and from the test pin to a device under test and / or propagated from the device under test to the same test pin or another test pin and from the test pin to the test device.

[0020] In embodiments, a pogo pin functions to provide this preferably stiff inner pin as part of a test pin. Such a pogo pin may have an internal and / or external spring, wherein the pogo pin's spring may be referred to as a pogo pin spring. The presence of the pogo pin may provide elasticity and stiffness between the inner pogo pin and the outer coil spring, and / or other properties, such as stability and guidance. While a pogo pin may have a spring, various embodiments of a pogo pin may have either an inner spring or an outer spring. In embodiments, the pogo pin may have a solid core (e.g., a cylinder located in the middle of the pogo pin) that allows for coaxial guidance of a softer outer helical (e.g., flat) coil spring. Without the stiff inner core provided by the pogo pin, the outer helical flat coil may be fragile. Thus, the pogo pin provides stability and guidance for at least one outer coil spring. For example, if the length of the central core is shorter than the length of the outer coil spring (e.g., helical coil), the central core may partially lack a spring effect. However, when an inner spring is present, the interior space of the pogo pin can be utilized particularly efficiently.

[0021] In one embodiment, a pogo pin may be configured as follows: the pogo pin may include an at least partially conductive pogo pin spring, wherein the pogo pin may further include a piston movably coupled to the pogo pin spring and may further include a fixed barrel in which at least a portion of the pogo pin spring and the piston are guided. While the configuration of the pogo pin may vary in different embodiments, the pogo pin may include a plunger or piston, a barrel, a spring, and optionally a biasing mechanism for biasing the spring into a default configuration.

[0022] In one embodiment, the coil spring surrounding the pogo pin over a majority of its length should surround the pogo pin in such a manner that a major portion of the pogo pin's length that is surrounded is larger than a minor portion of the pogo pin's length that is optionally not surrounded. For example, the major portion of the pogo pin may be at least 75%, particularly at least 90%, of the pogo pin's entire length.

[0023] Preferably, the coil spring can be the same length as the inner pogo pin, or it can be ±20% or even ±10% of the length of the inner pogo pin. In particular, the coil spring can also be slightly shorter than the pogo pin. During operation, the pogo pin can be pressed down first, and then during electrical testing, both the pogo pin and the coil spring can contact the device under test (DUT). Preferably, when current is applied, the pogo pin and the coil spring can contact the DUT simultaneously. Another option is that the coil spring is shorter than previously explained, but it is in electrical contact with the shoulder portion or upper portion of the pogo pin. In this configuration, the current can first pass through the upper portion of the pogo pin and then be distributed to the middle and lower portions of the pogo pin and the outer coil spring. More generally, the length of the outer flat spiral coil spring relative to the center pogo pin can depend on design requirements.

[0024] In one embodiment, the coil spring comprises, for example, a conductive curved sheet with a recess. In an embodiment, a flat coil spring can be used, which comprises a conductive and preferably circumferentially closed sheet. Alternatively, however, the coil spring can have a winding that is in the shape of a circular element in a cross-sectional view. Furthermore, a key point of an exemplary embodiment can be to provide an additional internal rigid spring pin in combination with an external coil spring, which can be a softer or relaxed coil spring, or a hard helix. A helical flat coil spring (which can, for example, be made of flat strips of stainless steel) may be the preferred choice, while a circular helical coil spring is also possible.

[0025] In one embodiment, the coil spring surrounds the pogo pin along its entire length. Thus, the entire axial extent of the pogo pin can be circumferentially surrounded by one or more coil springs. This protects the pogo pin along its entire length. Furthermore, this allows current to flow along a relatively long path along both the pogo pin and the at least one coil spring.

[0026] In one embodiment, the coil spring comprises a sleeve with a helical recess. The structure of the coil spring can thus be helical. Thus, the coil spring can be manufactured from a flat sheet that can be bent to form a cylindrical sleeve. The sleeve can be provided with a helically extending recess, thereby providing the sleeve with a spring function. The coil spring can have a helical construction. In particular, a coil spring based on a flat sheet can combine elastic properties with guidance and stability to provide an overall robust test needle. Alternatively, however, at least one coil spring can be configured as a helically wound filament or wire.

[0027] In one embodiment, the sleeve has a helical recess only in the front portion, while the rear portion does not. Thus, the rear portion of the sleeve can be devoid of spring function, with the spring function being provided solely by the front portion. This can increase the stability of the test needle as a whole. More specifically, having the recess in only a portion of the coil spring can have a further advantage, as only that portion allows the spring mechanism to function: leaving one end of the coil spring devoid of the recess can reduce the spring motion of the coil spring at the corresponding end. This can help reduce or even eliminate undesirable penetration of the test needle into connected components (particularly into printed circuit board (PCB) pads), as rotational and / or radial motion of the test needle can exacerbate effects on such components (e.g., wear and damage to the PCB pads). Furthermore, if, for example, the helical coil spring at the PCB end is designed to be soldered to a PCB via, it may be beneficial to secure the motion of the coil at the PCB end.

[0028] In one embodiment, the test needle includes at least one additional, at least partially conductive, coil spring surrounding the coil spring. By providing multiple coil springs, one of which is wound around another coil spring, and preferably arranged coaxially around the pogo pin, the overall current-carrying capacity of the test needle can be further increased. Furthermore, when multiple coil springs are arranged around the pogo pin, it is possible, for example, for one of the coil springs to increase the current-carrying capacity of the test needle, while another of the coil springs can be used to provide electromagnetic interference protection. However, multiple nested coil springs can also be used to increase the current-carrying capacity of the test needle.

[0029] In one embodiment, at least one additional coil spring includes a sleeve with a helical recess. In short, the construction of the additional coil spring can be, for example, as described above for the first coil spring. Thus, embodiments with a sleeve with a helical recess or a helically wound filament or wire are possible. However, for example, the coil pitch of the outer coil spring can be greater than the coil pitch of the inner coil spring.

[0030] In one embodiment, the helical recess of the coil spring and the helical recess of at least one further coil spring are displaced relative to each other in the axial direction. In such a mutually displaced configuration (see for example Figure 4 In the embodiment of the present invention, the recessed portion defining the turns of the coil spring and the recessed portion defining the turns of the additional coil spring are offset from each other. This can provide the following advantage: the coil spring and the additional coil spring are less likely to stick together when both are pressed. In short, for example, the recessed portion of the leaf coil spring and the recessed portion of the additional coil spring can be intentionally axially offset to prevent the coil spring and the additional coil spring from getting stuck.

[0031] In one embodiment, the pogo pin is electrically connected in parallel with the coil spring. This allows current to be directed through the pogo pin and through the one or more coil springs separately and independently. For example, the pogo pin, the coil spring, and / or the at least one additional coil spring can be electrically isolated from one another, allowing each to carry current during operation. Thus, for example, the inner surface of the coil spring and / or the inner surface of the at least one additional coil spring can be non-conductive, such that, for example, the inner surface of the coil spring will not be electrically connected to the inner pogo pin and / or the inner surface of the at least one additional coil spring will not be electrically connected to the coil spring. However, in one embodiment, the coil spring and the at least one additional coil spring may not need to be insulated, for example, when an air gap is maintained between the coil spring and the at least one additional coil spring. This may be advantageous for reducing mechanical friction between the coil spring and the at least one additional coil spring during test pin operation, which may involve, for example, plunger movement.

[0032] In one embodiment, the pogo pin is coaxial with the coil spring. In short, a coaxial pogo pin configuration can be provided. This coaxial arrangement can provide an EMI (electromagnetic interference) shielding arrangement. Thus, due to the surrounding coil spring, which can be brought to an electrical reference potential such as ground, electrical signals or currents propagating along the pogo pin can be protected from electromagnetic stray radiation from the environment.

[0033] In one embodiment, the test pin includes an electrically insulating gap radially between the pogo pin and the coil spring. For example, a physical distance, a non-conductive distance, or an interposer element can be provided between the pogo pin and the coil spring. Specifically, an air gap or an additional layer of material can be provided between the pogo pin and the coil spring. An air gap can be a preferred embodiment because it reduces friction between the pogo pin and the coil spring.

[0034] In one embodiment, the test pin includes an electrically insulating barrier element, such as an electrically insulating barrier coil spring, radially located between the pogo pin and the coil spring. For example, the electrically insulating barrier element may be disposed on the outer surface of the pogo pin. Such an insulating barrier element may ensure reliable electrical decoupling between the pogo pin and the coil spring. This may be to achieve independent current-carrying functions of the pogo pin and the coil spring or to maintain the pogo pin and the coil spring at different electrical potentials (e.g., when the coil spring provides EMI protection for the pogo pin).

[0035] In one embodiment, the electrically insulating barrier element radially separates a spring pin configured as a sensing contact from a coil spring configured as a force-applying contact. This may involve a preferred embodiment in which the spring pin is configured as the sensing contact, while one or more outer coil springs are configured as the force-applying contact. In another embodiment, the spring pin may also be configured as the force-applying contact. In yet another embodiment, the functions of the spring pin (herein serving as the force-applying contact) and the coil spring (herein serving as the sensing contact) are interchangeable. The terms "sensing contact" and "force-applying contact" are explained below: To accurately measure the current-voltage curve of a device under test (DUT), the instrumentation of a test device including a test pin should ensure that the parasitic resistance in the interconnection structure between the DUT terminals and the test device with the test pin is low. To this end, a four-terminal connection configuration (also known as a Kelvin configuration) can be provided in the test device including the test pin. In such a Kelvin configuration, the sensing leads or contacts can measure the electrical potential. This can be done as close to the DUT as possible so that the voltage drop caused by the contact parasitic resistance in the probe and the cable parasitic resistance is small or negligible. The force contact can represent a signal line, while the sense contact can represent a feedback line. If the sense contact is connected to the force contact at a location close to the DUT (the sense location), the system can stabilize the output voltage at the sense location at a set voltage through analog feedback.

[0036] In one embodiment, the length of the pogo pin is substantially equal (eg, within ±10%) to the length of the coil spring. Preferably, the coil spring may surround the pogo pin along substantially the entire length of the pogo pin and the coil spring.

[0037] In one embodiment, the free end portion of the coil spring and / or at least one additional coil spring (which may, for example, surround the aforementioned coil spring) includes a brush structure that is configured to at least partially remove contaminants from the test needle during operation. For example, the brush structure may include a circumferential array of brush elements located at the free end portion. Preferably, the brush elements may extend parallel to each other in the axial direction. By configuring the free end portion of the coil spring as a brush structure, a self-cleaning or contamination-reducing effect of the test needle can be achieved. This can extend the service life of the test needle.

[0038] The above description focuses primarily on the application of a test needle. Depending on the application, the outer coil springs can be used to distribute or redistribute current, enabling the test needle to carry a greater current, for example, three times the current when two coil springs are provided. In another embodiment, an additional or further function of using the outermost coil spring as an EMI shield can be provided. In such an embodiment, the shielding coil spring is not electrically connected to the leads of the device under test (for example, when the shielding coil spring is not exposed at the needle tip of the test needle facing the device under test), but can be connected to a reference potential (for example, to a ground trace of a test device), wherein the entire test needle is part of or connected to the test device.

[0039] Therefore, in one embodiment, the coil spring can be electrically decoupled from the pogo pin, and the coil spring can preferably be electrically coupled or configured to be electrically coupled to a reference potential, thereby providing electromagnetic interference protection to the pogo pin via the coil spring. Preferably, in this embodiment, the pogo pin is coaxial with the coil spring. Descriptively speaking, the pogo pin and the coil spring can form a coaxial pogo pin. By electrically insulating the outer helical coil spring from the inner core pogo pin (for example, if the outer helical coil spring is not used to increase current capacity, cause skin effect, etc.), the outer coil spring can be used, implemented, or configured as an EMI shield to protect the inner pogo pin from EMI. A configuration that enables this can configure the pogo pin and the surrounding coil spring into a coaxial structure, which can be referred to as a coaxial pogo pin, for example. In such an embodiment, a shielding layer or helical layer can be wrapped around the pogo pin. This can reduce the overall size of the pogo pin. Furthermore, the shielding layer or helical layer can have a grounding function, which can be achieved, for example, via a ground trace on a printed circuit board (PCB), which can be part of the test equipment. Furthermore, the pogo pin can also be part of the test equipment. In this embodiment of the pogo pins, there can be no electrical interconnection between the shielding layer or spiral layer (which can form an outer coil spring) and the inner pogo pins, allowing the shielding layer or spiral layer and the inner pogo pins to be electrically isolated from each other and to have different electrical potentials. Furthermore, this embodiment can disable the interface (e.g., contact portion) between the shielding layer or spiral layer (particularly the outer coil spring) and the leads of the semiconductor package to be tested. During testing, in one embodiment, the shielding layer (e.g., the outer coil spring) can be kept away from the leads to provide shielding against electromagnetic stray radiation interference.

[0040] In one embodiment, a testing apparatus includes a plurality of test pins having the aforementioned features assembled with a substrate. Using an array of test pins can increase test throughput and allow test sequences to be executed in parallel. Specifically, the method can include testing a device under test by simultaneously contacting the plurality of test pins having the aforementioned features with conductive structures of the device under test.

[0041] In one embodiment, the method includes applying a test signal having a current of at least 500 A. At such high current values, it may be most advantageous to conduct the current partially by a pogo pin and partially by at least one surrounding coil spring.

[0042] In one embodiment, the method includes applying a test signal having a pulse length not exceeding 10 μs. Short current pulses may result in high current peaks, which may make it advantageous to conduct such high currents partially by pogo pins and partially by at least one surrounding coil spring.

[0043] In one embodiment, the method includes testing a power semiconductor device as a device under test. Power semiconductor device testing may involve high electrical power applied via a test pin. Therefore, testing power semiconductor devices using a test pin according to an exemplary embodiment may be highly suitable, not only given the current-carrying capacity of the pogo pin, but also given the current-carrying capacity of at least one coil spring. For example, the semiconductor component under test (such as a semiconductor chip) may be used in power applications (e.g., in the automotive sector) and may, for example, have at least one integrated insulated gate bipolar transistor (IGBT) and / or at least one other type of transistor (such as a MOSFET, JFET, etc.) and / or at least one integrated diode. Such integrated circuit components may, for example, be manufactured using silicon technology or based on wide-bandgap semiconductors (e.g., silicon carbide or gallium nitride). The semiconductor power chip may include one or more field-effect transistors, diodes, inverter circuits, half-bridges, full-bridges, drivers, logic circuits, other devices, and the like.

[0044] In one embodiment, the method includes testing the device under test by contacting both a pogo pin and a coil spring with a conductive structure of the device under test. This can enable a test current to be transmitted to the DUT through the pogo pin and through the at least one coil spring.

[0045] In one embodiment, the method includes testing a device under test by contacting only pogo pins, rather than coil springs, with conductive structures of the device under test. The coil springs can then be brought to an electrical reference potential, such as ground, to provide EMI protection to the test pins.

[0046] In one embodiment, the test device includes a control unit configured to apply one or more electrical test signals as one or more electrical excitation signals to the device under test via one or more test pins, and to detect one or more electrical response signals from the device under test in response to the one or more test signals via the one or more test pins. Such a control unit can control the overall operation of the test device. In particular, such a control unit (e.g., a processor) can generate one or more electrical test signals and apply the one or more electrical test signals to one or more substrate structures. Such electrical test signals can propagate to the needle tips of the test pins and can then be applied to the corresponding conductive structures of the DUT. After the one or more test signals are applied to the DUT, the DUT processes these signals according to the electronic functions of the DUT. As a result of this signal processing, one or more response signals are generated in response to the applied test signals. These one or more response signals can be electrically transmitted from the conductive structures of the DUT to the control unit via the test pins. Based on the response signals, the control unit can determine whether the DUT currently being analyzed has passed or failed the test.

[0047] The above and other objects, features and advantages will become apparent from the following description and appended claims taken in conjunction with the accompanying drawings in which like parts or elements are designated by like reference numerals. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings, which are included to provide a further understanding of example embodiments and constitute a part of this specification, illustrate example embodiments.

[0049] In the attached figure:

[0050] Figure 1 A three-dimensional view of components of a test pin according to an exemplary embodiment is shown.

[0051] Figure 2 A device with a test pin (e.g. Figure 1 Test device for the test pin in the test.

[0052] Figure 3 Shown according to Figure 1 Different views of the test pin.

[0053] Figure 4 Shown according to Figure 1 A side view of the different components of a test pin.

[0054] Figure 5 Shown according to Figure 1 Multiple test pins and a 3D view of the device under test.

[0055] Figure 6Shown is a coil spring without a surrounding Figure 5 structure.

[0056] Figure 7 Shown according to Figure 1 Side and cross-sectional views of the test pin without the additional coil spring.

[0057] Figure 8 Shown according to Figure 1 Different views of a test pin with information indicating the mechanical stresses acting on the test pin during operation.

[0058] Figure 9 Shown according to Figure 1 Details of the components of the test pin.

[0059] Figure 10 Shown according to Figure 1 Different views of the test pin.

[0060] Figure 11 A three-dimensional view of a portion of a test needle is shown according to an exemplary embodiment.

[0061] Figure 12 Shown according to Figure 11 Cross-sectional view of the test pin.

[0062] Figure 13 Different views of features of a test needle providing a self-cleaning function are shown according to an exemplary embodiment.

[0063] Figure 14 Shown according to Figure 13 Side view of the test pin.

[0064] Figure 15 A cross-sectional view of a pogo pin of a test pin according to an exemplary embodiment is shown.

[0065] Figure 16 A schematic exploded view of a test pin having a coaxial configuration for providing electromagnetic interference protection functionality according to an exemplary embodiment is shown.

[0066] Figure 17 Shown according to Figure 16 Schematic 3D view of a test pin.

[0067] Figure 18 Shown with Figure 16 The test pin of the test device.

[0068] Figure 19 Shown according to Figure 16 Cross-sectional view of the test pin.

[0069] Figure 20 Shown Figure 19 and the electrical connection circuit of the test pin. DETAILED DESCRIPTION

[0070] The illustrations in the figures are schematic and not to scale.

[0071] Before describing exemplary embodiments in more detail with reference to the accompanying drawings, some general considerations based on which exemplary embodiments have been developed will be outlined.

[0072] The current-carrying capacity of contact pins is becoming a bottleneck in today's test environments, especially for power devices such as semiconductor chips using silicon carbide or gallium nitride technology, for example configured as insulated gate bipolar transistors (IGBT) chips. Modern power devices, especially wide bandgap (WBG) devices, may require demanding high test current values for direct current (DC) and alternating current (AC) testing. For example, AC tests (such as short-circuit tests) may require very high peak current values of 500A to 6500A within a time interval of 2μs. However, tests using test pins can also be performed at moderate currents. Excessive currents shorten the life of the test pins and may cause them to burn out prematurely. Therefore, a contact pin technology solution is needed that can drive ultra-high currents without the risk of excessive damage.

[0073] At the package level, the contact area on the leads may have limited space. Using copper clips instead of connecting wires can offer significant advantages in device-level current capability. However, even if the device is capable of operating at high currents, the bottleneck lies in the ability to test high currents with low inductance, particularly for WBG devices. Breakthrough test capabilities are needed for WBG technology.

[0074] In summary, traditional disadvantages of test devices with test pins include burnout of the pin tip due to overcurrent, significant self-inductance of the contact pin, and excessive pin tip contamination over time. Stray inductance of the test system can also be a problem. Furthermore, limitations with the skin effect can lead to high resistance and signal loss during high-frequency testing. As known to those skilled in the art, during high-frequency testing, current flows primarily in the surface layer of a conductor rather than across its entire cross-section. Due to this phenomenon, known as the skin effect, when there is insufficient skin area to allow sufficiently high currents at high frequencies, the impedance of the contact can increase, which can lead to signal loss.

[0075] The traditional approach to overcoming pin current-carrying capacity limitations is to place or cram as many pins as possible onto the very limited lead area. The current-carrying capacity of test pins can be increased by optimizing contact force and selecting highly conductive tip materials (e.g., using beryllium copper, silver, or gold plating). For some devices, multiple pogo pins can be placed on the same lead. However, this can have the following drawbacks: placing more pins outside the lead area may still be limited.

[0076] According to one exemplary embodiment, a test pin can be provided that can be coupled to a test device for electrically testing a device under test (DUT) (e.g., a semiconductor chip or package). The test pin can be constructed with an internal conductive spring pin surrounded by one or more conductive coil springs. By taking this approach, one or both of the following functions can be integrated into the test pin: First, both the spring pin and the at least one coil spring arranged around the periphery of the spring pin can conduct current during testing. As a result, higher test currents can be achieved, thereby achieving a higher current-carrying capacity of the test pin. In another embodiment, surrounding the spring pin with at least one coil spring can be used as a coaxial spring pin, thereby strongly suppressing degradation of the test pin's functionality due to external electromagnetic radiation. In short, the coil springs of this embodiment can provide electromagnetic interference (EMI) protection. Therefore, the test pin can be particularly advantageously used in high-frequency applications without the risk of significant EMI-based distortion.

[0077] In short, exemplary embodiments may provide nested contact pins. More specifically, a pogo pin may be nested with one, two, or more than two outer coil springs (which may be, for example, flat coil springs). This may allow for an increase in contact force and contact area (e.g., by a factor of two or three) while saving unused space, thereby increasing the current carrying capacity of the contact pin. Providing nested pins may also provide a larger skin area to mitigate the skin effect when performing tests at high frequencies (e.g., AC dynamic testing). Connecting more contact pins in parallel may help reduce self-inductance, which may be critical for high-speed, high-frequency testing. Advantageously, but not necessarily, the outer coil flat spring may induce a rotating, outwardly operating scrubbing mechanism, which may achieve a self-cleaning effect, thereby allowing for the reduction or even elimination of contaminants.

[0078] In a preferred embodiment, the spring pins can be nested with one or more outer (eg flat curved) coil springs to form multiple parallel and radial connections. Another option is to combine this structure with a bundle of brush-like flexible conductors.

[0079] Advantageously, the test needle of the exemplary embodiment can achieve high force and high contact area for excellent current carrying capacity. Furthermore, the resulting increased skin area can mitigate the skin effect when testing at high frequencies. Furthermore, the self-inductance of the test needle can be reduced by providing multiple parallel electrical connections, such as one electrical connection through a pogo pin and at least one electrical connection through at least one external coil spring. Optionally, improved cleaning efficiency of the contact tip can be achieved by providing both rotational and radial scrubbing motions.

[0080] According to an exemplary embodiment, the nested principle of a test pin can place a pogo pin inside at least one coil spring, allowing the pogo pin to pass through the cavity or hollow portion of the at least one coil spring, thereby eliminating gaps in the test pin. Providing a greater number of springs in the test pin can generate higher contact forces. Furthermore, this can provide a larger contact area, which can avoid current density peaks, effectively suppressing the risk of needle burnout at the test pin tip. The larger contact surface can improve contact impedance during high-frequency testing. This can reduce or even minimize current and / or signal loss due to the skin effect. By providing more parallel-connected pin elements, the self-inductance of the contact pin can be reduced. As an advantageous optional feature, the outer helical flat coil spring can be configured to trigger a rotating, outward-operating scrubbing mechanism that self-cleans contaminants from the test pin tip. Furthermore, providing a nested pin design allows the inner pogo pin to function as a sensing pin and the outer coil spring to function as a force-applying pin (or vice versa), thereby improving lead space utilization. Furthermore, the user experience can be improved by the test pin according to exemplary embodiments because nested contact pins can allow the user to freely add or remove nested components according to the current situation, needs, and requirements. This can allow the test pin to be used flexibly in a highly customizable configuration.

[0081] In short, a test pin according to an exemplary embodiment can enable high current, low inductance, low resistance, and an optional self-cleaning function for a test pin or contact pin. A test pin according to an exemplary embodiment can be particularly advantageous for use in semiconductor testing of power devices and for wide bandgap technology. Furthermore, a test pin according to an exemplary embodiment can be freely adjustable and customizable.

[0082] Figure 1 A three-dimensional view of components of a test needle 100 is shown according to an exemplary embodiment. Figure 2 A test pin 100 (eg Figure 1 A test device 102 having a test needle in the test apparatus. Figure 3 Shown according to Figure 1Different views of the test needle 100, namely a side perspective view, a top view and a true side view. Figure 4 Shown according to Figure 1 A side view of the different components of the test pin 100. Figure 5 Shown according to Figure 1 FIG. 1 is a three-dimensional view of a plurality of test pins 100 and a device under test 104 . Figure 6 The coil springs 110, 124 are shown without the surrounding Figure 5 structure. Figure 7 Shown according to Figure 1 1 and 2 are side views and cross-sectional views of the test needle 100 without the additional coil spring 124 . Figure 8 Shown according to Figure 1 Different views of a test needle 100 are shown, wherein the information indicates the distribution of mechanical stresses acting on the test needle 100 during operation. Figure 9 Shown according to Figure 1 Details of the components of the test pin 100. Figure 10 Shown according to Figure 1 Different views of the test pin 100.

[0083] More specifically, Figures 1 to 10 The test needle 100 shown in FIG is configured to be used with a test device 102 (see FIG. Figure 2 ) is used together with or is arranged for use in a test device 102 and is configured to be used to electrically contact a device under test (DUT) 104 to be tested. In the illustrated embodiment, the device under test 104 can be a package in which a semiconductor power chip (not shown) is encapsulated in an encapsulation material 150 (e.g., a molding compound). The pads or terminals of the semiconductor power chip can be coupled to the outside of the encapsulation material 150 through the conductive leads of the package. The conductive leads are an example of a conductive structure 144 of the device under test 104, to which an electrical excitation signal can be applied and / or at which an electrical response signal can be detected. Therefore, the conductive structure 144 can be in contact with the tips of one or more test needles 100 to perform electrical functional testing.

[0084] Now for example refer to Figure 1 The test pin 100 includes a conductive spring pin 106, which may form the core of the test pin 100. In addition, the test pin 100 may also include a conductive coil spring 110, which laterally surrounds the spring pin 106 at least over a majority of the length l of the spring pin 106. Figure 4As best shown, the length l of the pogo pin 106 can be the same as the length L of the coil spring 110, so that the pogo pin 106 can be surrounded by the coil spring 110 along its entire length l. Therefore, the coil spring 110 surrounds the pogo pin 106 over the entire length l of the pogo pin 106. In addition, the test pin 100 can include an additional conductive coil spring 124 surrounding the coil spring 110. For example, the length B of the additional coil spring 124 can be the same as the length L of the coil spring 110 and the length l of the pogo pin 106. However, other dimensions are also possible.

[0085] Still refer to Figure 1 and Figure 10 , and also refer to Figure 15 , the pogo pin 106 may include an at least partially electrically conductive pogo pin spring 108 (e.g., a coil spring made of a helically wound metal wire or filament). In addition, the pogo pin 106 may further include a piston 112 movably coupled to the pogo pin spring 108 (or even two opposing pistons 112 on two opposing ends, see Figure 1 and Figure 10 ). In addition, the pogo pin 106 comprises a fixed cylinder 114 in which the pogo pin spring 108 and the respective ends of one or two pistons 112 can be guided.

[0086] Now referring to the construction of the coil spring 110, the coil spring 110 can be formed based on a metal tubular or cylindrical sheet that can be bent so as to be circumferentially closed. A spiral recess 118 can be formed in at least a portion of the sheet to equip the sheet with a spring function. Thus, the coil spring 110 can be formed as a metal sleeve 116 having a spiral recess 118. Figure 4 As best seen in FIG, sleeve 116 may include helical recess 118 only in front portion 120 (which may face device under test 104 during operation), while rear portion 122 of sleeve 116 (which may be connected to other components of test apparatus 102 during operation) may not include a recess. Thus, rear portion 122 may provide high stability to coil spring 110, while front portion 120 may contribute to the elastic or spring characteristics.

[0087] Furthermore, the further coil spring 124 comprises a tubular or cylindrical metal sleeve 125 having a helical recess 126 to provide a spring function to the further coil spring 124. Figure 4 As best seen in FIG, the sleeve 125 may have the helical recess 126 only in the front portion 160, while the rear portion 162 of the sleeve 125 may not have a recess. Thus, the rear portion 162 may provide high stability for the further coil spring 124, while the front portion 160 may contribute to the elasticity or spring characteristics.

[0088] like Figure 4 As shown, the spiral recesses 118, 126 of the coil spring 110 and the further coil spring 124 can be displaced relative to each other in the axial direction. In this displaced configuration, the recesses 118, 126, which define the turns of the coil spring 110 and the further coil spring 124, respectively, are offset relative to each other in the axial direction. This can provide the following advantage: when both coil springs 110, 124 are pressed together, the two coil springs 110, 124 are less likely to stick together.

[0089] In the test pin 100 shown, the pogo pin 106 may form a central core surrounded by a coil spring 110 which in turn is surrounded by a further coil spring 124. Figures 1 to 10 It is not shown in the figure, but one or more additional coil springs can be arranged radially around the further coil spring 124. On the other hand, the further coil spring 124 can also be omitted to obtain a very compact test needle 100, see Figure 7 .

[0090] As shown, the pogo pin 106, coil spring 110, and additional coil spring 124 are nested. Furthermore, they are electrically connected in parallel. A test current can propagate through each of the pogo pin 106, coil spring 110, and additional coil spring 124, enabling the test pin 100 to have a very high current-carrying capacity. In the illustrated embodiment, the pogo pin 106, coil spring 110, and additional coil spring 124 are coaxially arranged.

[0091] In addition, the plurality of test pins 100 may be grouped in rows or two-dimensional arrays, see Figure 5 and Figure 6 For example, five test pins 100 per lead are foreseen.

[0092] Advantageously, a test pin 100 according to an exemplary embodiment can be constructed based on a pogo pin 106 nested with a second outer flat helical coil spring 110 and followed by a third outer helical coil spring 124. This can increase the contact pin density within a limited lead area, for example by a factor of three or more. As the number of contacts of the test pin 100 increases, the current carrying capacity of the test pin 100 can also be increased, for example by a factor of three. In short, the test current can flow in parallel through the metallic pogo pin 106, the metallic coil spring 110, and the metallic additional coil spring 124.

[0093] With the configuration of the test pin 100 shown, the self-inductance of the contact portion or test pin 100 can be significantly reduced compared to conventional methods. Below, the possible reduction of the self-inductance of the contact portion or test pin 100 composed of the spring pin 106, the coil spring 110 and the further coil spring 124 will be explained: Assuming that L1 represents the inductance of the spring pin (106), L2 represents the inductance of the coil spring (110), and L3 represents the inductance of the further coil spring (124), the resulting inductance L is calculated as follows: L=(1 / L1+1 / L2+1 / L3) -1 Therefore, the self-inductance of the test pin 100 can be reduced by connecting the pogo pin 106, the coil spring 110, and the additional coil spring 124 in parallel. In short, compared to the conventional method in which only the pogo pin 106 is present, stray inductance can be reduced by additionally providing the coil spring 110 (and preferably the additional coil spring 124).

[0094] Furthermore, the configuration of the test needle 100 may increase the skin area to mitigate the effects of the skin effect, which may be particularly beneficial for high frequency testing.

[0095] like Figure 9 As best seen in FIG, the described configuration of the test pin 100 can allow for higher contact forces and contact areas. For example, three times or more contact forces and / or contact areas can be achieved. Additionally, three times or more skin area can be achieved. This can improve the electrical performance of the test pin 100. Thus, Figure 9 It is shown that by additionally providing the coil spring 110 (and preferably also providing the further coil spring 124), the contact area of the test pin 100 relative to the device under test 104 can be significantly increased compared to a configuration including only the spring pin 106. According to an exemplary embodiment, this can achieve very low contact resistance.

[0096] Now refer to Figure 10 , an electrically insulating gap 130 may be radially provided, formed, or maintained between the center pogo pin 106 and the inner coil spring 110, and / or may be radially provided, formed, or maintained between the inner coil spring 110 and the outer or additional coil spring 124. This allows the pogo pin 106, the coil spring 110, and the additional coil spring 124 to be electrically operated independently of one another.

[0097] In one embodiment, the coil spring 110 and the coil spring 124 are provided with a plurality of coils having a plurality of springs. For example, the coil spring 110 can be configured to have a coil pitch of 2.2mm, an internal diameter of 1.40mm, an external diameter of 1.70mm and a flat coil thickness of 0.15mm. For example, other coil spring 124 can be embodied as a coil pitch of 2.8mm, an internal diameter of 1.80mm, an external diameter of 2.10mm and a flat coil thickness of 0.15mm. Preferably, the coil spring 110 and other coil spring 124 do not overlap each other. Electrically insulating gap 130 (for example, air gap) can allow a smooth spring motion with very little friction to be provided. Suitable materials for making coil springs 110, 124 are beryllium copper, steel, steel alloy, nickel, nickel alloy, bronze, bronze alloy. A more extensive list of suitable metallic conductive materials that can be used to fabricate the helical coil springs 110 , 124 includes stainless steel, nickel beryllium, copper beryllium, copper nickel, copper titanium, carbon steel, brass, bronze, cupronickel, copper-silicon, Inconel 600, copper-iron, and copper-cadmium.

[0098] In short, Figures 1 to 10 The embodiments allow for high current capability, low inductance, low impedance, large skin area, and optional automatic self-cleaning contact pins (see description below). Figure 13 and Figure 14 This is very advantageous in semiconductor testing, especially in power device testing and wide bandgap device testing. Figures 16 to 20 When configuring the coil spring 110 in this manner (without the coil spring 124 ) or configuring the coil spring 124 so as to surround the coil spring 110 , additional EMI protection can be achieved, in particular for the pogo pin 106 .

[0099] See Figure 8 , shows the Van Mises stress (in MPa) during operation of the test needle 100. As shown in the figure, only a very moderate Van Mises stress is applied to the test needle 100 compared to conventional methods.

[0100] like Figure 10 As shown in detail 172 of FIG. 1 , the plurality of openings 170 in the sleeves 116 , 125 for forming the helical recesses 118 , 126 may allow for soft and / or elastic properties to be achieved in dedicated sections of the coil springs 110 , 124 .

[0101] Figure 2 A test device 102 with the described test needle 100 is shown according to an exemplary embodiment.

[0102] More specifically, Figure 2A test apparatus 102 is schematically shown for testing a device under test 104 (DUT) by performing an electronic full functional test according to an exemplary embodiment. The DUT 104 may be an IC (Integrated Circuit) device, such as a semiconductor package for high power applications.

[0103] The test device 102 includes a housing or base 140, which may include an electrically insulating material. One or more conductive test pins 100 may be assembled with the base 140 and may extend through the base 140. The test pins 100 are configured to electrically contact conductive structures 144, such as leads (or pads or traces), of the device under test 104 to conduct electrical test signals from the test device 102 to the device under test 104 and from the device under test 104 back to the test device 102 during testing.

[0104] The control unit 164 (which may be a microprocessor or the like) may be coupled to a mounting structure 166 (e.g., a printed circuit board, PCB) and may be configured to apply a test signal as an excitation to the device under test 104 via the mounting structure 166 and via the test pin 100. The mounting structure 166 may be electrically coupled to the test pin 100 via one or more electrical contacts 168. The control unit 164 may be further configured to detect a response of the device under test 104 to the test signal applied via the test pin 100. Based on the functionality of the device under test 104, a specific pattern of response signals may be expected when a particular device under test 104 is functioning properly. Thus, analysis of the response signals may be used as a basis for determining whether the device under test 104 has passed the test and therefore may be considered a good product that can be shipped to a customer, or whether the device under test 104 has failed the test. If a determination is made that the device under test has failed the test, further testing may be performed, the device under test 104 may be further processed, or it may be discarded.

[0105] For example, performing the test may include applying a test signal having a current of at least 500 A and / or a pulse length of no more than 10 μs. The test pin 100 according to the exemplary embodiment and described above can withstand harsh conditions that may occur, for example, when testing a power semiconductor device as the device under test 104 .

[0106] During testing of the device under test 104, both the pogo pin 106 and the coil spring 110 may be brought into contact with the conductive structure 144 of the device under test 104. Optionally, at least one additional coil spring 124 (when present) may also be brought into contact with the conductive structure 144 of the device under test 104. By distributing the test current over multiple metal elements (see reference numerals 106, 110, 124), high currents may be applied without risk of damage.

[0107] In another embodiment, testing of the device under test 104 can be achieved by contacting only the spring pin 106 and not the coil spring 110 (or the spring pin 106 and the coil spring 110 but not the additional coil spring 124) with the conductive structure 144 of the device under test 104. This can allow electromagnetic interference (EMI) protection to be provided by the outermost coil spring 110 (or 124), especially when the outermost coil spring 110 (or 124) is brought to an electrical reference potential (e.g., ground) (see Figures 18 to 20 ).

[0108] During execution of a test application, the test needle 100 may be secured to the mounting structure 166 and may be actuated to contact the device under test 104 .

[0109] like Figure 2 As shown, the sleeve 125 of the additional coil spring 124 has the spiral recess 126 only in the front portion 160, while the rear portion 162 of the sleeve 125 does not have a recess. By omitting the spiral recess 126 in the rear portion 162, the spring characteristics of the additional coil spring 124 can be concentrated only in the front portion 160, while the rear portion 162 is rigid and thus very suitable for fixing to the socket housing to avoid PCB damage. A corresponding design can be used for the coil spring 110 (see reference numerals 120, 122 and the above reference numerals). Figure 4 description).

[0110] By providing the helical recess 126 / 118 only in the front portion 160 / 120 facing the device under test 104, a spring characteristic is provided in the lower portion of the nested spring pin 106, making the test pin 100 well-suited for actuation at the side of the device under test 104. The opposite upper end portion can be secured by the socket housing, resulting in significantly less spring movement on the mounting side of the test pin 100. On the other hand, the device end of the test pin 100 is more dynamic during actuation.

[0111] Figure 11 A three-dimensional view of a portion of a test needle 100 is shown according to an exemplary embodiment. Figure 12 Shown according to Figure 11 FIG. 1 is a cross-sectional view of a test needle 100 .

[0112] refer to Figure 11 and Figure 12 The electrically insulating barrier element 132 radially separates the spring pins 106 configured as sensing contacts from the coil springs 110 , 124 configured as force-applying contacts.

[0113] In the illustrated embodiment, the electrically insulating barrier element 132 is formed as a dielectric coating on the barrel 114 of the pogo pin 106. Alternatively, a separate electrically insulating barrier element 132 may be inserted between the pogo pin 106 and the coil spring 110. In yet another embodiment, an electrically isolating air gap may be formed between the pogo pin 106 and the coil spring 110.

[0114] As already mentioned, spring pin 106 can be used as a sensing pin that can measure an electrical potential or other electrical signal. Coil spring 110 can serve as a first force-applying pin, while optional additional coil spring 124 can serve as a second force-applying pin. The respective force-applying pins can represent signal lines capable of applying an electrical signal to the respective coil springs 110 and 124. Thus, the inner spring can be used for signal sensing, while the outer spring can be used for signal application. By electrically insulating the inner spring pin 106 on its outer surface via electrically insulating barrier element 132, a force-sensing configuration can be achieved within the same test pin 100.

[0115] Figure 13 Different views of features of a test needle 100 providing a self-cleaning function are shown according to an exemplary embodiment. Figure 14 Shown according to Figure 13 1 is a side view of the test pin 100.

[0116] refer to Figure 13 , shows an overview 174 of the head portion of a test needle 100 of an exemplary embodiment, a first detail 176, and a further enlarged second detail 178 to illustrate features providing a self-cleaning function. More specifically, the free end portion 138 of the coil spring 110 (i.e., the end of the coil spring 110 that faces the device under test 104 during testing operation) includes a brush structure 134 configured to at least partially remove contaminants from the test needle 100 during operation. The brush structure 134 includes a circumferential array of (e.g., at least five or at least ten) brush elements 136 located at the free end portion 138. During operation of the test needle 100 for testing the device under test 104, the circumferentially distributed plurality of brush elements 136 can form a plurality of contact portions that can rotate and expand radially outward during operation. This can scrape the needle tip to remove contaminants. This effect can be further enhanced by the wedge-shaped geometry at the free end of the brush element 136, see reference numeral 180. Thus, the outer flat coil spring 124 and / or the coil spring 110 (or just the coil spring 110 without the additional coil spring 124) can provide a rotational and outward scrubbing motion, which can achieve self-cleaning.

[0117] By configuring the tip or end of the helical flat coil spring 110 / 124 with multiple branches of a brush-like needle section (preferably with rounded tips), the contact area with the device under test 104 can be increased. This, along with the rotation and radially outward scrubbing, can remove contaminants. The multiple branches of the brush tip and the provision of one or more helical flat coil springs 110 / 124 can provide a self-cleaning mechanism through a rotational and outward scrubbing mechanism. Advantageously, during operation of the test needle 100, only very moderate Van Mises stresses can be applied to the brush element 136.

[0118] Figure 15 A cross-sectional view of the pogo pin 106 of the test pin 100 is shown according to an exemplary embodiment.

[0119] In addition to the above reference Figures 1 to 10 In addition to the components of the pogo pin 106 described above, Figure 15 The pogo pin 106 also shows a current router 154 and a crimp 156 that holds the piston 112 in the barrel 114. Figure 15 In the spring pin configuration, solder tails 158 are also foreseen. For example, Figure 15 The height of the pogo pins 106 may be in the range of 5 mm to 9 mm, preferably in the range of 6 mm to 7.5 mm.

[0120] Figure 16 A schematic exploded view of a test pin 100 having a coaxial configuration for providing electromagnetic interference protection functionality according to an exemplary embodiment is shown. Figure 17 Shown according to Figure 16 Schematic three-dimensional view of a test needle 100. Figure 18 Shown with Figure 16 A test device 102 of a test pin 100 of the type. Figure 19 Shown according to Figure 16 Detailed cross-sectional view of the test needle 100. Figure 20 Shown Figure 19 and the electrical connection circuit of the test pin 100. Descriptively speaking, Figures 16 to 20 The embodiments provide a configuration of an outer helical coil spring 110 / 124 for providing electromagnetic interference (EMI) shielding functionality to the inner spring pin 106 (and optionally the inner helical coil spring 110 in the presence of the outer coil spring 124 ).

[0121] See first Figure 16 and Figure 17 , showing a schematic exploded view of the test pin 100 ( Figure 16 ) and three-dimensional schematic diagram ( Figure 17), wherein the pogo pin 106 is arranged as an inner metal (e.g. copper) conductor. The pogo pin 106 may be surrounded by an electrically insulating barrier element 132, which is implemented here as a tubular dielectric insulator. The electrically insulating barrier element 132 is in turn surrounded by a coil spring 110 (or more generally, an outermost coil spring, e.g. an outermost coil spring 124 in the case where there are multiple coil springs 110, 124). For example, the coil spring 110 comprises a conductive braid 146 or a continuous sleeve. A protective coating 184, such as a protective plastic layer, may surround the outermost coil spring 110 as a protective and electrically insulating outer sheath. The outermost coil spring 110 may provide an EMI shielding function for the pogo pin 106, in particular when said outermost coil spring 110 is connected to ground or another fixed reference potential.

[0122] Therefore, according to Figure 16 and Figure 17 The test pin 100 may include an electrically insulating barrier element 132 , such as an electrically insulating barrier coil spring, radially located between the pogo pin 106 and the coil spring 110 . For example, the electrically insulating barrier element 132 may be arranged on an outer surface of the pogo pin 106 .

[0123] Advantageously, the coil spring 110 may be electrically decoupled from the pogo pin 106 , and the coil spring 110 may be electrically coupled to a reference potential (eg, ground potential) to provide electromagnetic interference protection to the pogo pin 106 .

[0124] Figure 18 The configuration of a test device 102 with a test pin 100 having EMI protection features is shown. Figure 19 Shown through Figure 18 The cross section of the test pin 100, Figure 20 Circuitry is shown for connecting the outermost coil spring 110 to an electrical reference potential 190 and for connecting the pogo pin 106 to a test signal source 196 to provide an electrical test signal.

[0125] Descriptively speaking, Figures 18 to 20 The embodiment can configure the test pin 100 as a coaxial spring pin, for example, by maintaining a characteristic impedance of 50Ω. In other words, due to the corresponding configuration of the outermost coil spring 110, the spring pin 106 can be converted into a spring pin 106 with EMI shielding protection.

[0126] To this end, the electrical contacts 168 of the mounting structure 166 of the testing device 102 may be provided with one or more electrical reference potential traces 186 (eg, ground traces) and one or more signal traces 188 .

[0127] In the described configuration, the inner spring pin 106 can be maintained as a conductive path for carrying an electrical test signal. Furthermore, the spring pin 106 can be surrounded by an electrically insulating material inserted in the form of an electrically insulating barrier element 132. The electrically insulating barrier element 132 can act as a high-dielectric-constant dielectric. The electrically insulating barrier 132 can be followed on its outer surface by an outer conductive coil spring 110 coupled to an electrical reference potential 190 (e.g., ground). Descriptively, the described configuration can position the spring pin 106 coaxially with the outer coil spring 110 to provide EMI shielding of the spring pin 106 by the coil spring 110. Thus, electromagnetic radiation 194 from the environment will be shielded by the outer coil spring 110 coupled to the electrical reference potential 190. Consequently, due to the EMI protection features 110, 132, 190, the electrical test signal provided to the spring pin 106 by the test signal source 196 will be prevented from being excessively affected by the electromagnetic radiation 194.

[0128] It should be noted that the term "comprising" does not exclude other elements or features, and "a" or "an" does not exclude a plurality. Elements described in association with different embodiments may also be combined. It should also be noted that the reference numerals should not be interpreted as limiting the scope of the claims. Furthermore, the scope of the present application is not intended to be limited to the particular embodiments of the processes, machines, manufactures, compositions of matter, means, methods, and steps described in the specification. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufactures, compositions of matter, means, methods, or steps.

Claims

1. A test needle (100) for a test device (102), for electrically contacting a device under test (104) to be tested, the test needle (100) comprising: An at least partially conductive pogo pin (106); as well as An at least partially electrically conductive coil spring (110) which surrounds the pogo pin (106) over at least a majority of its length (1).

2. The test needle (100) according to claim 1, wherein The coil spring (110) includes, for example, a conductive curved sheet having a recess (118).

3. The test needle (100) according to claim 1 or 2, wherein: The coil spring (110) surrounds the pogo pin (106) over the entire length (l) of the pogo pin (106).

4. The test needle (100) according to any one of claims 1 to 3, wherein The coil spring (110) includes a sleeve (116) having a helical recess (118).

5. The test needle (100) according to claim 4, wherein The sleeve (116) has a helical recess (118) only in the front portion (120), while the rear portion (122) of the sleeve (116) has no recess.

6. The test needle (100) according to any one of claims 1 to 5, wherein The test needle (100) includes at least one further electrically conductive coil spring (124) surrounding at least part of the coil spring (110).

7. The test needle (100) according to claim 6, wherein The at least one further coil spring (124) comprises a sleeve (125) having a helical recess (126).

8. The test needle (100) according to claim 4 and 7, wherein The helical recesses (118, 126) of the coil spring (110) and the at least one further coil spring (124) are displaced relative to each other in the axial direction.

9. The test needle (100) according to any one of claims 1 to 8, wherein The test needle (100) includes at least one of the following features: The spring pin (106) is electrically connected in parallel with the coil spring (110); The spring needle (106) is coaxial with the coil spring (110); The test pin (100) includes an electrically insulating gap (130) radially located between the pogo pin (106) and the coil spring (110).

10. The test needle (100) according to any one of claims 1 to 9, wherein The test pin (100) includes an electrically insulating barrier element (132), such as an electrically insulating barrier coil spring, located radially between the pogo pin (106) and the coil spring (110).

11. The test needle (100) according to claim 10, wherein The electrically insulating barrier element (132) is arranged on an outer surface of the pogo pin (106).

12. The test needle (100) according to claim 10 or 11, wherein The electrically insulating barrier element (132) radially separates the spring pin (106) configured as a sensing contact from the coil spring (110) configured as a force-applying contact.

13. The test needle (100) according to any one of claims 1 to 12, wherein The length (l) of the pogo pin (106) is substantially equal to the length (L) of the coil spring (110).

14. The test needle (100) according to any one of claims 1 to 13, wherein A free end portion (138) of the coil spring (110) and / or at least one further coil spring (124) comprises a brush structure (134) configured to at least partially remove contaminants from a test needle (100) during operation.

15. The test needle (100) according to claim 14, wherein The brush structure (134) includes a circumferential array of brush elements (136) located at the free end portion (138).

16. The test needle (100) according to any one of claims 1 to 15, wherein The coil spring (110) is electrically decoupled from the pogo pin (106), and the coil spring (110) is preferably electrically coupled to a reference potential (190) so as to provide electromagnetic interference protection for the pogo pin (106) through the coil spring (110).

17. A test device (102) for electrically testing a device under test (104), the test device (102) comprising: · substrate (140); and At least one test needle (100) according to any one of claims 1 to 16, the at least one test needle (100) being assembled with a base (140) and being configured for electrically contacting a device under test (104) for conducting a test signal from the device under test (104) and / or conducting a test signal to the device under test (104).

18. The test device (102) according to claim 17, wherein The test device (102) comprises a plurality of test pins (100) according to any one of claims 1 to 16 assembled with the base body (140).

19. A method for testing a device under test (104), the method comprising: Bringing the test needle (100) according to any one of claims 1 to 16 into contact with a conductive structure (144) of a device under test (104); Applying a test signal as stimulus to the conductive structure (144) of the device under test (104) via the test needle (100); and Detecting the response of the device under test (104) to the test signal.

20. The method according to claim 19, wherein The method includes at least one of the following features: The method includes applying a test signal having a current of at least 500A; The method includes applying a test signal having a pulse length not exceeding 10 μs; The method includes testing a power semiconductor device as a device under test (104); The method comprises testing a device under test (104) by simultaneously contacting a plurality of test pins (100) according to any one of claims 1 to 16 with a conductive structure (144) of the device under test (104); The method includes testing a device under test (104) by contacting both a pogo pin (106) and a coil spring (110) with a conductive structure (144) of the device under test (104); The method includes testing a device under test (104) by contacting only a pogo pin (106) and not a coil spring (110) with a conductive structure (144) of the device under test (104).

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