Coaxial probe for testing high-frequency PCB (Printed Circuit Board)

Abstract

The invention discloses a coaxial probe for testing a high-frequency PCB (Printed Circuit Board), which comprises a large needle tube, one end of the large needle tube is connected with a connector, the other end of the large needle tube is connected with an inner conductor probe and an outer conductor shell, and the outer conductor shell is positioned outside the inner conductor probe; and an insulating support body is filled between the outer conductor shell and the inner conductor probe. The problems of high-frequency impedance matching, contact stability, service life and operation convenience in the prior art are solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor detection, and particularly relates to a coaxial probe for high-frequency PCB board testing. BACKGROUND

[0002] In the research and development, production and fault analysis of high-frequency PCB boards, it is crucial to accurately measure the transmission line characteristics (such as insertion loss, return loss, impedance continuity). The currently widely used test probes have the following problems: 1. High-frequency performance limitation: Traditional spring probes or ordinary coaxial probes have poor impedance matching problems at GHz and above frequencies, resulting in significant signal reflection (high VSWR) and signal attenuation (high insertion loss), which seriously reduces the measurement accuracy.

[0003] 2. Unstable contact: The PCB test points (such as pads, vias) may have surface oxidation, unevenness or solder paste residue. Ordinary probe contact pressure is insufficient or uneven, which easily leads to contact resistance fluctuation or instantaneous open circuit, especially on small test points, which introduces test noise and error.

[0004] 3. Structural wear and short service life: Frequent mechanical contact and friction easily lead to probe tip and internal elastic element wear, causing contact resistance increase, high-frequency characteristic deterioration or even failure, which requires frequent replacement, increasing cost and downtime.

[0005] 4. Poor operation convenience: Fixed probes or cumbersome clamp systems are difficult to adapt to dense and irregularly distributed test points on PCBs, especially for multi-point synchronous testing or test points located in narrow areas, resulting in low positioning and contact efficiency.

[0006] Therefore, it is urgent to develop a coaxial probe for PCB testing that can maintain excellent electrical performance at high frequencies, provide stable and reliable contact, have a long service life, and be flexible to operate. SUMMARY

[0007] The purpose of the present application is to provide a coaxial probe for high-frequency PCB board testing, which solves the problems of high-frequency impedance matching, contact stability, service life and operation convenience in the prior art.

[0008] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a coaxial probe for high-frequency PCB board testing, comprising a large needle tube, one end of the large needle tube is connected with a connector, the other end is connected with an inner conductor probe and an outer conductor shell, the outer conductor shell is located outside the inner conductor probe; an insulating support is filled between the outer conductor shell and the inner conductor probe.

[0009] The technical scheme of the present application also has the following characteristics: As a preferred technical scheme of the present application, the inner conductor probe comprises an inner needle tube, an inner spring and an inner needle head, the inner needle tube is fixed inside the large needle tube, the inner spring and the inner needle head are placed in the inner needle tube in sequence, and one end of the inner needle head extends out of the pipe opening of the inner needle tube.

[0010] As a preferred technical scheme of the present application, the outer conductor shell comprises a first outer needle tube, an outer spring and a second outer needle tube; the first outer needle tube is fixed at one end of the large needle tube, the second outer needle tube and the first outer needle tube are both provided with steps, the steps of the second outer needle tube and the steps of the first outer needle tube are matched and clamped, and then the second outer needle tube is slidably arranged outside the first outer needle tube within a certain range, and the outer spring is arranged between one end of the second outer needle tube and one end of the large needle tube.

[0011] As a preferred technical scheme of the present application, the end face of the second outer needle tube is a sawtooth end face.

[0012] As a preferred technical scheme of the present application, the end of the inner needle head is in the shape of plum blossom.

[0013] The present application has the following beneficial effects: (1) The coaxial probe for high-frequency PCB board testing has super-high frequency characteristics. The stepped impedance design and low-loss medium ensure excellent insertion loss (IL) and voltage standing wave ratio (VSWR) performance, and the working frequency band can cover DC to 40 GHz or even higher, and the test result is accurate and reliable.

[0014] (2) The coaxial probe for high-frequency PCB board testing has extreme contact stability. The unique force compensation structure and accurate guiding mechanism provide constant and vertical normal contact pressure, the multi-pronged tip of the inner conductor probe and the sawtooth end face of the outer sleeve end face ensure that the contact resistance is extremely low and highly stable, is not affected by slight changes in the surface state of the pad or slight disturbances in operation, and effectively eliminates measurement noise and jumping points.

[0015] (3) The coaxial probe for high-frequency PCB board testing has super-long service life: wear-resistant tip material, optimized pressure distribution design and greatly reduced micro-motion friction greatly improve the mechanical life of the probe, reduce maintenance and replacement costs.

[0016] (4) The coaxial probe for high-frequency PCB board testing has signal integrity guarantee. The overall design maintains the integrity of the high-frequency characteristics of the measured signal to the greatest extent, and provides a basis for accurate evaluation of high-speed digital circuits and radio frequency / microwave circuits. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the structure of a coaxial probe for testing high-frequency PCB boards according to the present invention.

[0018] Figure 2 This is a schematic diagram of the principle of using a coaxial probe for testing high-frequency PCB boards according to the present invention.

[0019] Among them, 1. large needle tube, 2. inner spring, 3. inner needle tube, 4. inner needle head, 5. second outer needle tube, 6. insulating support, 7. first outer needle tube, 8. outer spring, 9. high-frequency PCB board testing. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Example 1 like Figure 1 As shown, a coaxial probe for testing high-frequency PCB boards according to the present invention includes a large needle tube 1, one end of which is connected to a connector 9, and the other end is connected to an inner conductor probe and an outer conductor housing. The outer conductor housing is located outside the inner conductor probe. A low-loss insulating support 6 is filled between the outer conductor housing and the inner conductor probe.

[0022] The present invention provides a coaxial probe for high-frequency PCB board testing, comprising an inner conductor probe and an outer conductor shell. The inner conductor probe is a tip probe made of wear-resistant conductive material. The core innovation lies in its special force compensation structure. The inner cavity of the probe body is equipped with a small spring with high precision and low stress relaxation. The inner cavity is provided with a radial compensation gap, which allows the spring to undergo slight radial deformation during compression, thereby converting the spring's rebound force into a more concentrated normal contact pressure with the tip perpendicular to the PCB test surface, significantly reducing the lateral component of the contact pressure. The outer conductor shell is composed of multiple sleeves and an outer spring. The inner hole step of the outer sleeve and the outer circle step of the inner sleeve cooperate with each other to provide axial constraint. The rebound force of the outer spring gives the outer sleeve a normal contact force when it contacts the PCB test surface. The end face of the outer sleeve that contacts the PCB is serrated. This structure can: (1) penetrate the slight oxide layer or stains on the surface of the pad and reduce the contact resistance; (2) reduce the tip swing or slippage caused by uneven contact surface and provide extremely stable contact. (3) Minimize the fretting friction at the contact interface and extend the service life of the tip.

[0023] The outer conductor is a multi-layer precision turned sleeve structure. Its inner cavity is designed as a multi-section impedance ladder. By precisely controlling the inner diameter and dielectric constant of each section (achieved by selecting a specific high-frequency engineering plastic as the internal support insulator), the impedance transition between the inner conductor probe tip and the rear-end standard connector (such as SMA / SMP) is smooth, effectively suppressing signal reflections caused by impedance discontinuities. Especially at high frequencies (>10 GHz), the voltage standing wave ratio (VSWR) is significantly improved.

[0024] The internal insulator that fills between the inner and outer conductors and supports the elastic contact head guide sleeve is made of PTFE, a high-frequency thermoplastic material with extremely low dielectric loss, and its contact surface shape with the inner and outer conductors is optimized to minimize high-frequency signal medium loss.

[0025] The probe body tail adopts a standard connector interface (such as SMA / SMP), and the coaxial probe can be selected according to the interface of the test system.

[0026] The inner conductor probe includes an inner needle tube 3, an inner spring 2, and an inner needle head 4. The inner needle tube 3 is fixed inside the large needle tube 1, the inner spring 2 and the inner needle head 4 are placed in the inner needle tube 3 in turn, and one end of the inner needle head 4 protrudes from the pipe opening of the inner needle tube 3.

[0027] The outer conductor shell includes a first outer needle tube 7, an outer spring 8, and a second outer needle tube 5. The first outer needle tube 7 is fixed to one end of the large needle tube 1. The second outer needle tube 5 and the first outer needle tube 7 are both provided with steps. After the steps of the second outer needle tube 5 and the first outer needle tube 7 are matched and clamped, the second outer needle tube 5 is slidably arranged outside the first outer needle tube 7 within a certain range. The outer spring 8 is arranged between one end of the second outer needle tube 5 and one end of the large needle tube 1. The end surface of the second outer needle tube 5 is a sawtooth end surface, and the end of the inner needle head 4 is a quincunx shape.

[0028] As shown in Figure 2 When the test point is pressed, the inner needle head 4 of the inner conductor probe is forced to retreat and compresses the inner spring 3. Since the inner spring 2 is constrained in the inner needle tube 3, the spring force can only be transmitted axially at this time, which is converted into concentrated normal pressure acting on the inner conductor 901 of the PCB test point 9. Similarly, the sawtooth end surface of the second needle tube 5 acts on the outer conductor 902 of the PCB test point 9, and the elastic force of the outer conductor spring 8 is converted into concentrated normal pressure acting on the outer conductor 902 of the PCB test point 9. The tip of the inner needle head 4 and the section of the first needle tube 5 both have the ability to pierce the surface of the measured point slightly oxidized or stained, reducing the contact resistance, cooperating with the action of the spring force, ensuring the effective contact of the test probe and the measured point, and this elastic test contact effectively reduces the structure wear compared to the traditional hard connection, increasing the service life of the probe. High-frequency signals are conducted through a precise impedance matching path to ensure measurement accuracy. After release, the spring resets.

[0029] The foregoing description illustrates and describes several preferred embodiments of the present invention. However, it is to be understood that the present invention is not limited to the precise embodiments described herein, and that various modifications and changes can be effected therein by those skilled in the art without departing from the spirit of the present invention. It is intended that the present invention be construed as including all such modifications and changes as fall within the scope of the appended claims.

Claims

1. A coaxial probe for high frequency PCB board testing, characterized by, The utility model relates to a large needle tube (1) one end is connected with the connector (9), the other end is connected with the inner conductor probe and the outer conductor shell, the outer conductor shell is located the outside of inner conductor probe, is filled with the insulating support (6) between the outer conductor shell and inner conductor probe.

2. The coaxial probe for testing a high-frequency PCB according to claim 1, wherein, The inner conductor probe contains inner needle tube (3), inner spring (2) and inner needle head (4), the inner needle tube (3) is fixed in the inside of large needle tube (1), and inner spring (2) and inner needle head (4) are placed in the inner needle tube (3) in proper order, and the one end of inner needle head (4) is stretched out from the pipe orifice of inner needle tube (3).

3. The coaxial probe for testing a high-frequency PCB according to claim 2, wherein, The outer conductor shell contains first outer needle tube (7), outer spring (8) and second outer needle tube (5), the first outer needle tube (7) is fixed in one end of large needle tube (1), and the upper of second outer needle tube (5) and first outer needle tube (7) is provided with the step, after the step of second outer needle tube (5) is matched with the step of first outer needle tube (7) and is packed, second outer needle tube (5) can be slidably arranged in the outside of first outer needle tube (7) in certain range, and the outer spring (8) is arranged between one end of second outer needle tube (5) and one end of large needle tube (1).

4. The coaxial probe for testing a high-frequency PCB according to claim 3, wherein, The end face of second outer needle tube (5) is sawtooth end face.

5. The coaxial probe for testing a high-frequency PCB board according to claim 4, wherein, The end of inner needle head (4) is plum blossom shape.

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