High resistance test fixture

Abstract

This application relates to the field of test fixture technology and discloses a high-resistance test fixture, including tweezers contacts, an interface and shielding assembly, an overvoltage protection circuit, a resistor network, a filter capacitor C1, and a shielded cable. The interface and shielding assembly includes a triaxial connector and a coaxial connector interface. The output end of the coaxial connector interface is connected to the input end of the overvoltage protection circuit. The triaxial connector has a Low end and a Guard end; the Low end is connected to the output end of the resistor network, and the Guard end is connected to the shielding layer of the shielded cable. The input end of the overvoltage protection circuit is connected to the output end of the coaxial connector interface. The tweezers contacts are connected to surface-mount devices, with the low-voltage end of the tweezers contacts connected to the Low end and the high-voltage end of the tweezers contacts connected to the output end of the resistor network. The first end of the filter capacitor C1 is connected between the resistor network and the tweezers contacts, and the second end of the filter capacitor C1 is grounded. Using this application can improve the testing efficiency, reliability, safety, and accuracy of high-resistance testing results.

Description

Technical Field

[0001] This application relates to the field of test fixture technology, and in particular to a high-resistance test fixture. Background Technology

[0002] In the field of electronic component manufacturing and application, the electrical performance testing of surface mount devices (SMD), especially multilayer ceramic capacitors (MLCC), is crucial. Among them, high resistance characteristic (such as leakage current) testing is a key step in evaluating their reliability.

[0003] Currently, there is a lack of dedicated test fixtures on the market for high-resistance testing of SMD devices such as MLCCs. Existing testing methods have several shortcomings: on the one hand, SMD components are small and difficult to fix, making it difficult for conventional fixtures to hold them stably, resulting in cumbersome and inefficient testing operations; on the other hand, high-resistance testing is susceptible to electrical noise interference, and ordinary test circuits do not employ effective shielding measures, affecting test accuracy; in addition, some high-resistance tests need to be performed under high-voltage conditions, and existing solutions lack targeted safety protection designs, making it difficult to ensure the safety of the testing process.

[0004] The aforementioned problems mean that existing testing methods cannot meet users' actual needs for convenient, accurate, and safe testing of high-resistivity SMD devices such as MLCCs. Therefore, there is an urgent need for a dedicated high-resistivity test fixture to solve these problems. Utility Model Content

[0005] The purpose of this application is to provide a high-resistance test fixture to solve the technical problems mentioned in the background art.

[0006] To achieve the above objectives, this application discloses the following technical solution: a high-resistance test fixture, comprising tweezers contacts, an interface and shielding assembly, an overvoltage protection circuit, a resistor network, a filter capacitor C1, and a shielded cable; wherein:

[0007] The interface and shielding assembly includes a triaxial connector and a coaxial connector interface; the output end of the coaxial connector interface is connected to the input end of the overvoltage protection circuit; the triaxial connector is provided with a Low end and a Guard end, the Low end is connected to the output end of the resistor network, and the Guard end is connected to the shielding layer of the shielded cable.

[0008] The input terminal of the overvoltage protection circuit is connected to the output terminal of the coaxial connector interface;

[0009] The tweezers contact is connected to a surface mount device to secure it, and the low-voltage end of the tweezers contact is connected to the low-voltage end, while the high-voltage end of the tweezers contact is connected to the output end of the resistor network.

[0010] The first end of the filter capacitor C1 is connected between the resistor network and the tweezers contact, and the second end of the filter capacitor C1 is grounded.

[0011] Preferably, the overvoltage protection circuit includes diodes CR1, CR2, CR3, CR4, CR5, and CR6; wherein diodes CR6, CR5, and CR4 are connected in series, and the negative terminal of diode CR6 is connected to the output terminal of the coaxial connector interface; diodes CR1, CR2, and CR3 are connected in series, and the negative terminal of diode CR1 is connected to the output terminal of the coaxial connector interface; the positive terminals of diodes CR4 and CR3 are grounded.

[0012] Preferably, the resistor network includes resistors R1, R2, R3, and R4 connected in series; wherein the input terminal of resistor R1 is connected to the output terminal of the overvoltage protection circuit, and the output terminal of resistor R4 is connected to the high-voltage terminal of the tweezers contact and the first terminal of the filter capacitor C1, respectively.

[0013] Preferably, the filter capacitor C1 is a high-frequency filter capacitor.

[0014] Preferably, diodes CR1, CR2, CR3, CR4, CR5, and CR6 are Zener diodes or ultrafast recovery diodes.

[0015] Beneficial Effects: The high-resistance test fixture of this application, by setting tweezer contacts, can directly connect and fix to surface mount devices, realizing convenient clamping of SMD devices and improving the efficiency of testing operations. Secondly, by setting a shielded cable, and connecting the guard end of the triaxial connector to the shielding layer of the shielded cable, an effective shielding structure is formed. Combined with the filtering effect of the filter capacitor C1 to remove noise, the influence of electrical noise on high-resistance testing can be reduced, improving the accuracy of test results. At the same time, by setting an overvoltage protection circuit, and connecting its input end to the output end of the coaxial connector interface, it can play an overvoltage protection role during high-voltage testing. With the cooperation of the triaxial connector and the resistor network, leakage current testing of SMD devices can be performed in a safe high-voltage environment, improving the safety of the testing process. In addition, the interface and shielding components are composed of triaxial connectors and coaxial connector interfaces, which can be adapted to specific test equipment, and the connection relationship between the resistor network and each component ensures the stable transmission of the test circuit, further ensuring the reliability of high-resistance testing. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a hardware circuit schematic diagram of a high-resistance test fixture provided in an embodiment of this application. Detailed Implementation

[0018] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0019] In this document, the term "include" is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "includes..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0020] This embodiment discloses a high-resistance test fixture, mainly used in high-resistance test equipment such as B2985B / B2987B and 4339A, for testing the high-resistance characteristics (such as leakage current) of surface mount devices (SMD, such as MLCC), solving problems in existing tests such as inconvenient SMD device fixing, large electrical noise interference, and insufficient safety of high-voltage testing. Figure 1 As shown, the high-resistance test fixture in this embodiment includes tweezers contacts, an interface and shielding assembly, an overvoltage protection circuit, a resistor network, a filter capacitor C1, and a shielded cable. The specific structure and connection relationship of each component are as follows:

[0021] 1. Tweezers contacts

[0022] The tweezers have a conductive gripping structure with a shape that fits the size of SMD devices. They can stably fix SMD devices (such as the pins or electrodes of MLCCs) through mechanical clamping force, avoiding poor contact caused by loose devices during testing.

[0023] The tweezers contacts are divided into a low-voltage end and a high-voltage end: the low-voltage end is electrically connected to the low end of the triaxial connector, and the high-voltage end is electrically connected to the output end of the resistor network, thereby realizing the transmission of electrical signals between the SMD device and the test circuit.

[0024] 2. Interface and shielding components

[0025] The interface and shielding components are used to connect the fixture to external testing equipment and reduce external electromagnetic interference, including triaxial connectors and coaxial connector interfaces (in this embodiment, a high-voltage adapted BNC coaxial interface is selected).

[0026] Coaxial connector interface: adopts a standard coaxial interface (such as N type or BNC type). Its input end is used to connect to the signal output end of external test equipment, and the output end is electrically connected to the input end of the overvoltage protection circuit, which is responsible for introducing external test signals (such as high voltage test signals) into the internal circuit of the fixture.

[0027] The triaxial connector has a Low terminal (low-voltage signal terminal) and a Guard terminal (protection ring terminal). The Low terminal is electrically connected to the output of the resistor network and is used to transmit low-voltage test signals. It also forms a signal association with the tweezers contacts to transmit test signals from surface-mount devices fixed by the tweezers contacts after processing by the resistor network, thus forming a low-voltage signal loop. The Guard terminal is electrically connected to the shielding layer of the shielded cable. The shielding layer wraps around the signal transmission path, forming a closed shielding space. It synchronizes the shielding layer potential with the Low terminal, guides surface leakage current to flow to ground through the Guard terminal, effectively blocks external electromagnetic noise intrusion, and improves the anti-interference capability of the test signal.

[0028] 3. Overvoltage protection circuit

[0029] The overvoltage protection circuit is used to prevent instantaneous high voltage from damaging SMD devices or test equipment during testing. The input terminal of the overvoltage protection circuit is connected to the output terminal of the coaxial connector interface, which is also connected to the input terminal of the resistor network. The voltage signal, after bidirectional clamping, is transmitted to the resistor network. In this embodiment, the overvoltage protection circuit includes diodes CR1, CR2, CR3, CR4, CR5, and CR6. In this embodiment, diodes CR1-CR6 are Zener diodes or ultrafast recovery diodes to meet the rapid clamping requirements of high voltage surges.

[0030] The diodes CR6, CR5, and CR4 are connected in series to form the first branch, and the negative terminal of the diode CR6 is connected to the output terminal of the coaxial connector interface, while the positive terminal of the diode CR4 is grounded.

[0031] The diodes CR1, CR2, and CR3 are connected in series to form a second branch, with the negative terminal of diode CR1 connected to the output terminal of the coaxial connector interface and the positive terminal of diode CR3 grounded.

[0032] When an overvoltage occurs in the input signal, the two sets of series diodes can quickly conduct, discharging the overvoltage signal through the ground terminal, preventing the overvoltage signal from entering subsequent circuits, and thus protecting the SMD device and test equipment.

[0033] In this embodiment, the bidirectional clamping logic of the overvoltage protection circuit includes:

[0034] Forward overvoltage (coaxial connector interface voltage is higher than clamping threshold): CR1 (reverse breakdown, cathode voltage > anode) → CR2 (forward conduction, anode voltage > cathode) → CR3 (forward conduction, cathode voltage > anode), forming a discharge path of coaxial connector interface → CR1 (cathode → anode) → CR2 (anode → cathode) → CR3 (cathode → anode) → ground, clamping the forward voltage;

[0035] Reverse overvoltage (coaxial connector interface voltage is lower than ground potential, i.e., negative overvoltage): CR6 (reverse breakdown, cathode voltage < anode) → CR5 (forward conduction, anode voltage > cathode) → CR4 (forward conduction, cathode voltage > anode), forming a discharge path of ground → CR4 (anode → cathode) → CR5 (cathode → anode) → CR6 (anode → cathode) → coaxial connector interface, clamping the reverse voltage.

[0036] 4. Resistor Network

[0037] A resistor network is used to divide and limit the input signal, ensuring that the signal transmitted to the SMD device remains stable within the required testing range. In this embodiment, the resistor network includes resistors R1, R2, R3, and R4 connected in series. The input terminal of resistor R1 is connected to the output terminal of the overvoltage protection circuit (i.e., receiving the signal after overvoltage protection), and the output terminal of resistor R4 is connected to the high-voltage terminal of the tweezers (transmitting the processed signal to the SMD device) and the first terminal of the filter capacitor C1, respectively, to achieve voltage division adaptation for wide-range high-impedance measurements.

[0038] By using resistors R1-R4 in series to divide the voltage, the high-voltage test signal can be adjusted to a voltage range suitable for testing SMD devices, while limiting the loop current to prevent excessive current from damaging the devices.

[0039] 5. Filter capacitor C1

[0040] The first end of the filter capacitor C1 is connected between the resistor network and the tweezers contact, and the second end of the filter capacitor C1 is grounded, used to filter out high-frequency interference in the high-voltage signal.

[0041] The function of the filter capacitor C1 is to filter out high-frequency noise (such as high-frequency interference generated by electromagnetic radiation) mixed in during signal transmission. By guiding the high-frequency noise to the ground terminal, the purity of the signal transmitted to the SMD device is ensured, and the accuracy of high impedance testing is improved.

[0042] In this embodiment, the filter capacitor C1 is a high-frequency filter capacitor.

[0043] 6. Shielded cable

[0044] The shielded cable is a conductor with an outer metal shielding layer. Its shielding layer is electrically connected to the Guard end of the triaxial connector. The inner core wire is used to transmit test signals (such as signals connecting the tweezers contacts and the resistor network). Specifically, the shielded cable is placed outside the signal transmission path of the fixture (including the signal links of BNCHigh, resistor network, and tweezers contacts). Through the cooperation of the shielding layer and the Guard end, a fully enclosed shielding structure is formed, which further blocks the interference of external electromagnetic noise on the internal signals, and at the same time prevents the internal high voltage signals from radiating outward, thereby improving the safety of the testing process.

[0045] Work process

[0046] During testing, the SMD device (such as MLCC) is fixed in place by tweezers. The signal from the external testing equipment (such as B2985B) is input through the coaxial connector interface, and then passes through the overvoltage protection circuit (to prevent overvoltage) and the resistor network (voltage divider and current limiter) in sequence before being transmitted to the SMD device through the high-voltage end of the tweezers. At the same time, the low-voltage end of the SMD device forms a loop with the low-voltage end of the triaxial connector through the low-voltage end of the tweezers, realizing closed-loop signal transmission.

[0047] In this process, the shielding layer of the shielded cable and the Guard end of the triaxial connector work together to reduce external noise interference; the filter capacitor C1 filters out high-frequency noise; and the overvoltage protection circuit responds quickly under abnormal high voltage to ensure test safety. Ultimately, this achieves convenient, accurate, and safe testing of the high-impedance characteristics of SMD devices.

[0048] Based on the above, the high-impedance test fixture of this embodiment, by setting tweezer contacts, can directly connect and fix to surface mount devices (SMDs), solving the problem in the prior art where the small size of SMD components makes them difficult to fix, leading to cumbersome testing operations. This achieves convenient clamping of SMD devices (such as MLCCs) and improves the efficiency of testing operations. By setting a shielded cable, and connecting the guard end of the triaxial connector to the shielding layer of the shielded cable, an effective shielding structure is formed. Combined with the filtering effect of the filter capacitor C1 on noise, the impact of electrical noise on high-impedance testing can be significantly reduced, solving the problem of insufficient shielding in ordinary test circuits in the prior art, which affects testing accuracy. This design improves the accuracy of test results. By incorporating an overvoltage protection circuit with its input connected to the coaxial connector output, it provides overvoltage protection during high-voltage testing. Combined with the triaxial connector and resistor network, it supports safe leakage current testing of SMD devices under high-voltage conditions, addressing the lack of targeted safety protection in existing high-voltage testing technologies and enhancing the safety of the testing process. The interface and shielding components, including the triaxial connector and coaxial connector, are compatible with specific testing equipment. Furthermore, the connection between the resistor network and each component ensures stable transmission of the test circuit, further guaranteeing the reliability of high-impedance testing.

[0049] Finally, it should be noted that the above description is only a preferred embodiment of this application and is not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A high resistance test fixture, characterized by, Includes tweezers contacts, interface and shielding components, overvoltage protection circuit, resistor network, filter capacitor C1, and shielded cable; among which: The interface and shielding assembly includes a triaxial connector and a coaxial connector interface; the output end of the coaxial connector interface is connected to the input end of the overvoltage protection circuit; the triaxial connector is provided with a Low end and a Guard end, the Low end is connected to the output end of the resistor network, and the Guard end is connected to the shielding layer of the shielded cable. The input terminal of the overvoltage protection circuit is connected to the output terminal of the coaxial connector interface; The tweezers contact is connected to a surface mount device to secure it, and the low-voltage end of the tweezers contact is connected to the low-voltage end, while the high-voltage end of the tweezers contact is connected to the output end of the resistor network. The first end of the filter capacitor C1 is connected between the resistor network and the tweezers contact, and the second end of the filter capacitor C1 is grounded.

2. The high resistance test fixture of claim 1, wherein, The overvoltage protection circuit includes diodes CR1, CR2, CR3, CR4, CR5, and CR6; wherein diodes CR6, CR5, and CR4 are connected in series, and the negative terminal of diode CR6 is connected to the output terminal of the coaxial connector interface; diodes CR1, CR2, and CR3 are connected in series, and the negative terminal of diode CR1 is connected to the output terminal of the coaxial connector interface; the positive terminals of diodes CR4 and CR3 are grounded.

3. The high-resistance test fixture according to claim 1, characterized in that, The resistor network includes resistors R1, R2, R3, and R4 connected in series; wherein, the input terminal of resistor R1 is connected to the output terminal of the overvoltage protection circuit, and the output terminal of resistor R4 is connected to the high-voltage terminal of the tweezers contact and the first terminal of the filter capacitor C1, respectively.

4. The high-resistance test fixture according to claim 1, characterized in that, The filter capacitor C1 is a high-frequency filter capacitor.

5. The high-resistance test fixture according to claim 2, characterized in that, Diodes CR1, CR2, CR3, CR4, CR5, and CR6 are Zener diodes or ultrafast recovery diodes.

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