High-flatness adaptive microwave probe

Abstract

The invention provides a high-flatness adaptive microwave probe which comprises a coaxial cable and contact pieces arranged at the end of the coaxial cable, and the contact pieces comprise at least one grounding contact piece and at least one signal contact piece. A connecting part, an extension part and a needle tip are sequentially arranged in the grounding contact piece and the signal contact piece along the length direction, the connecting part is connected with the coaxial cable, the extension part and the needle tip extend out of the end part of the coaxial cable, and a hollow part is arranged in the extension part of the grounding contact piece, so that the elasticity of the needle tip of the probe is increased; the probe can be stably inserted when the height difference exists on the test surface, the compatibility of the test surface is high, the needle points can be recovered to the same plane after the test, the leveling time of the probe can be obviously reduced, compared with a microwave probe with a common needle point, the probe can be stably inserted more easily, the damage to a bonding pad after the test is smaller, the abrasion to a contact piece can be effectively reduced, and the service life of the probe can be prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of microwave probes, and in particular to a microwave probe with high flatness adaptability. Background Art

[0002] Microwave probes are mainly used in on-wafer testing, junction parameter extraction, on-chip antenna testing, PCB board-level testing and other scenarios. They are important tools for accurately measuring the high-frequency characteristics of chips and circuits, improving packaging processes and circuit models, and improving product consistency and reliability. They are also important testing tools for the development of integrated circuits. In general, when calibrating and testing the probe, the height difference of the pad to be tested must be strictly controlled during the design and processing to ensure that the test surface is flat so that each probe tip can stably contact the pad to be tested at the same time to achieve correct test results and minimize damage to the pad and probe. There are two existing technical routes for the production of microwave probes:

[0003] Technical route 1 is a coaxial cable microwave probe: CN113447680B discloses a novel microwave probe contact piece and a manufacturing method thereof, the microwave probe contact piece comprises a plurality of split parallel arranged contact pieces installed at the front end of the coaxial cable, the bottom surface of the front end of each contact piece is an elliptical arc surface, and the top surface of the front end is an inwardly concave inclined surface, the probe has high requirements for the flatness of the measured position, if the flatness is poor after the needle is inserted, the needle tip cannot be restored to be flush, which affects the re-test and reduces the test efficiency. CN115951104A discloses a coaxial microwave measurement probe, comprising a probe holder, a coaxial cable and a pressing piece, the end of the probe holder has a groove structure, the coaxial cable is located inside the probe holder and passes through the end of the probe holder, the pressing piece is fixed at the end of the probe holder and is located at the opening of the groove structure, an active space is formed between the pressing piece and the groove structure, and the passing end of the coaxial cable moves in the active space. Although this probe can overcome the problems of long sliding distance, large touch marks and unstable test results during probe testing in the above-mentioned technical route, its flatness compatibility is only below 10 microns.

[0004] Technical route 2 is a coaxial cable-free probe structure: Figure 7 As shown, the contact piece adopts a hollow needle tip, but is not connected to the coaxial cable. Instead, the probe cavity air groove is integrally processed. There is no coaxial cable structure, and only the inner conductor of the probe welds the contact piece to the probe cavity and the inner conductor of the connector respectively. Although this type of probe has high planar compatibility, it has high requirements on the processing accuracy of the cavity air groove and the inner conductor of the connector, resulting in great difficulty in cavity processing, low yield, high product cost, great difficulty in assembly, low assembly efficiency, many rework steps, and high time consumption. Summary of the invention

[0005] In order to overcome the problems existing in the prior art, the present invention provides a high-planarity adaptive microwave probe, including a coaxial cable and a contact piece arranged at the end of the coaxial cable, the contact piece includes at least one ground contact piece and at least one signal contact piece, and a connecting part, an extension part and a needle tip are sequentially arranged in the ground contact piece and the signal contact piece along their length direction, the connecting part is connected to the coaxial cable, the extension part and the needle tip extend from the end of the coaxial cable, and a hollow is arranged in the extension part of the ground contact piece.

[0006] Specifically, a mounting plane is provided on the bottom surface of the end portion of the coaxial cable, and the connecting portion is welded to the bottom of the mounting plane.

[0007] Specifically, the hollowed-out shape is a circle or a polygon with rounded inner corners.

[0008] Specifically, the thickness of the contact sheet is 0.04 mm-0.12 mm.

[0009] Specifically, the length of the contact piece extending out of the coaxial cable portion is 0.6 mm-1.2 mm.

[0010] Specifically, the extended portion of the signal contact piece adopts a gradual shrinkage structure along the width direction, shrinking from both sides to the middle, the ground contact piece close to the signal contact piece extends toward the signal contact piece along the width direction, and the ground contact piece away from the signal contact piece shrinks toward the signal contact piece along the width direction.

[0011] Specifically, the hollow area is proportional to the distance between the pin tips of the ground contact sheet and the signal contact sheet.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] 1. The microwave probe of the present invention is additionally designed with an extension part and a hollow part is designed in the extension part, so that the elasticity of the probe tip is increased, and the needle can be stably inserted even when there is a height difference on the test surface. The test surface compatibility is high. After the test, each needle tip can be restored to the same plane, which can significantly reduce the probe leveling time. Compared with the microwave probe with an ordinary needle tip, it is easier to stably insert the needle, the damage to the pad after the test is less, and the wear on the contact piece can be effectively reduced to increase the service life of the probe.

[0014] 2. The microwave probe of the present invention is directly connected to the coaxial cable by welding, and the contact surfaces of the two are both flat. The cable welding surface processing process is simple, the processing efficiency is high, and the processing cost is low. The assembly is assembled by welding, and the assembly difficulty is small and the assembly efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the assembly structure of the present invention;

[0016] Figure 2 It is a schematic diagram of the contact sheet structure of the present invention;

[0017] Figure 3 It is a schematic diagram of pad flatness;

[0018] Figure 4 is a diagram showing the relationship between the contact piece extension length and the flatness compatibility;

[0019] Figure 5 This is an effect diagram of the needle insertion state of the probe of the present invention;

[0020] Figure 6 This is a picture showing the effect of the probe of the present invention after being inserted into the needle;

[0021] Figure 7 It is a schematic diagram of the structure of a coaxial cable-free probe in the prior art.

[0022] Figure numerals: 1. signal contact piece; 2. ground contact piece; 3. coaxial cable; 4. probe mounting bracket; 5. absorber base; 6. connecting part; 7. extension part; 8. needle tip; 9. first hollow; 10. second hollow; 11. mounting plane. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The specific implementation of the present invention is described in detail below in combination with specific embodiments.

[0024] like Figure 1-Figure 2 As shown, the present invention provides a high-flatness adaptable microwave probe, which is composed of a probe mounting bracket 4, an absorber base 5, an absorbing tube, a coaxial cable 3 and a contact piece. The coaxial cable 3 and the absorber base 5 are fixed on the mounting bracket, the absorbing tube is fixed on the coaxial cable 3, and after a mounting plane 11 is processed at the end of the coaxial cable 3, the contact piece is welded in the mounting plane 11.

[0025] The contact sheet includes at least one ground contact sheet 2 (G) and at least one signal contact sheet 1 (S). The number of ground contact sheets 2 and signal contact sheets 1 can be adjusted according to the type of pad, such as GS, SG, GSG, GSSG, GSGSG, etc. A connecting portion 6, an extending portion 7 and a needle tip 8 are sequentially arranged in the ground contact sheet 2 and the signal contact sheet 1 along their length direction. The connecting portion 6 is connected to the coaxial cable 3, and the extending portion 7 and the needle tip 8 extend from the end of the coaxial cable 3.

[0026] The connecting portion 6 is used to connect the contact piece with the coaxial cable 3. A mounting plane 11 is provided on the bottom surface of the end of the coaxial cable 3. The mounting plane 11 is formed by oblique milling of the end surface of the coaxial cable 3. The connecting portion 6 is fixedly connected to the mounting plane 11 by soldering. The contact piece and the coaxial cable 3 are interconnected by welding. Both contact surfaces are flat. The cable welding surface processing process is simple, the processing efficiency is high, and the processing cost is low. The assembly by welding is easy to assemble and the assembly efficiency is high.

[0027] The needle tips 8 are arranged at the ends of the extension parts 7. Each needle tip 8 is in a flush state and located in the same plane. The needle tips 8 are used to contact with the pad to be tested to transmit signals.

[0028] The microwave probe is generally fixed on a probe table and a probe holder for needle insertion operation. The probe is controlled to move downward, and the needle tip 8 contacts the chip pad and then slides forward to achieve stable needle insertion. Since there is a height difference when the tested pad is processed, in the prior art, when the flatness of the test surface of the pad is poor, the microwave probe is made to contact the pad stably, which can easily cause deformation of the contact piece after needle insertion. Moreover, due to the poor flatness of the pad, the microwave probe generally slides a long distance, thereby causing greater damage to the pad.

[0029] In order to make each needle tip 8 of the probe stably contact the pad to be tested at the same time and reduce the damage to the pad, the present invention designs an additional extension part 7 in the contact sheet on the basis of the prior art, and designs a hollowing out in the extension part 7 of the ground contact sheet 2. The extension part 7 is designed to improve the elasticity of the ground contact sheet 2 so that the probe can return to the same plane after piercing the pad with a certain height difference. The shape of the hollowing out can be circular or polygonal, and at least one hollowing out part is provided in the extension part 7 of each ground contact sheet 2. If the hollowing out part is a polygon, it is necessary to round the inner corners of the polygon to reduce the discontinuity of the circuit, thereby reducing the influence of parasitic effects. At the same time, the rounded corners can disperse stress, avoid structural damage caused by stress concentration, and extend the service life. The hollowing out design reduces the stress of the ground contact sheet 2 on the basis of ensuring the strength of the ground contact sheet 2, thereby improving the elasticity of the ground contact sheet 2. The hollow area of ​​the ground contact sheet 2 is proportional to the distance between the ground contact sheet 2 and the pinpoints 8 of the signal contact sheet 1. When the distance between the pinpoints 8 of the contact sheet increases, the size of the signal ground contact sheet will also increase. At this time, a larger hollow area is required to reduce stress.

[0030] The extension part 7 of the signal contact piece 1 adopts a gradual contraction structure along the width direction to gradually contract from both sides to the middle, thereby improving the elasticity of the signal contact piece 1 and reducing the downward pressure. The extension part 7 adopts a gradual contraction structure to maintain impedance continuity and avoid signal reflection caused by sudden width changes. The grounding contact piece 2 extends toward the signal contact piece 1 along the width direction on the side close to the signal contact piece 1, and the grounding contact piece 2 contracts toward the signal contact piece 1 along the width direction away from the side close to the signal contact piece 1. The grounding contact piece 2 provides a low-impedance loop path for high-frequency signals and forms a shielding layer, which helps to reduce the interference of external electromagnetic fields on the transmitted signals, while reducing the radiation of signals to the external environment, maintaining the impedance matching of the transmission line, and reducing signal reflection and loss, so as to ensure the stability and accuracy of microwave signals during transmission.

[0031] As a preferred embodiment of the present invention, a first hollow 9 and a second hollow 10 are provided in the extension portion 7 of the ground contact sheet 2. The first hollow 9 and the second hollow 10 are arranged along the length direction. The first hollow 9 is a quadrilateral, and the second hollow 10 is a triangle. The inner angles of the first hollow 9 and the second hollow 10 are both chamfered.

[0032] When the contact piece contacts the pad, it is subjected to the upward reaction force from the pad, and the contact piece bends and deforms. Within the elastic limit, the degree of bending is related to the magnitude of the external force. Assuming that the contact pieces of the same material and different lengths require the same downward pressure when the needle is stable, the longer the contact piece extends from the cable end face, the smaller the deformation distance, the less damage to the device under test, and the better the appearance after the chip test.

[0033] On the basis of ensuring the strength of the contact sheet, the thickness of the contact sheet is 0.04mm-0.12mm, and the length of the contact sheet extending out of the coaxial cable 3 (the length of the extension part and the needle tip 8) is between 0.6mm-1.2mm. The thickness of the contact sheet is crucial to controlling the contact resistance and ensuring the elasticity of the contact sheet, which can ensure that the electrical and mechanical properties are still good after multiple needle insertions, and achieve stable testing.

[0034] The microwave probe provided by the present invention improves the compatibility with the test surface. When the height difference is small, this hollow needle tip 8 structure can make the contact piece easily contact the pad at the same time. When the height difference of the tested pad is less than 100 microns, stable needle insertion can still be achieved, and each contact piece can be restored to a flush state after needle insertion, which has higher compatibility and can significantly reduce the probe leveling time. Compared with the microwave probe with an ordinary needle tip 8, it is easier to stably insert needles, and it can still maintain good electrical and mechanical properties after multiple needle insertions, which can effectively ensure the stability of the test. In addition, traditional microwave probes generally can only stably contact after sliding a distance of 30 microns to 60 microns. The microwave probe of the present invention can stably insert needles after sliding 10 microns to 30 microns, which will not only reduce damage to the pad, but also effectively reduce wear on the contact piece, thereby improving the service life of the probe.

[0035] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A high flatness adaptable microwave probe, characterized in that: It comprises a coaxial cable and a contact piece arranged at the end of the coaxial cable, wherein the contact piece comprises at least one ground contact piece and at least one signal contact piece, wherein the ground contact piece and the signal contact piece are provided with a connecting portion, an extending portion and a needle tip in sequence along their length direction, wherein the connecting portion is connected to the coaxial cable, the extending portion and the needle tip extend from the end of the coaxial cable, and a hollow portion is provided in the extending portion of the ground contact piece.

2. The high flatness adaptable microwave probe according to claim 1, characterized in that: The bottom surface of the coaxial cable end is provided with a mounting plane, and the connecting portion is welded to the bottom of the mounting plane.

3. The high flatness adaptable microwave probe according to claim 1, characterized in that: The hollowed-out shape is a circle or a polygon with rounded inner corners.

4. The high flatness adaptable microwave probe according to claim 1, characterized in that: The thickness of the contact sheet is 0.04 mm-0.12 mm.

5. The high flatness adaptable microwave probe according to claim 1, characterized in that: The length of the contact piece extending out of the coaxial cable portion is 0.6 mm to 1.2 mm.

6. The high flatness adaptable microwave probe according to claim 1, characterized in that: The extended portion of the signal contact piece adopts a gradual shrinkage structure along the width direction, shrinking from both sides to the middle, the ground contact piece extends toward the signal contact piece along the width direction close to the signal contact piece, and the ground contact piece shrinks toward the signal contact piece along the width direction away from the signal contact piece.

7. The high flatness adaptable microwave probe according to claim 1, characterized in that: The hollow area is proportional to the distance between the ground contact sheet and the signal contact sheet.

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