A MEMS probe card and its impedance regulation method

Abstract

The present invention relates to a MEMS probe card and its impedance regulation method. The structure includes a PCB board, a substrate, and an interlayer therebetween. Spring pins are provided in the interlayer. The two ends of the spring pins extend out of the upper and lower sides of the interlayer respectively and are in contact with the PCB board and the substrate respectively. The interlayer includes a dielectric layer and metal layers provided on the upper and lower sides of the dielectric layer. The spring pins are divided into ground spring pins and signal spring pins. The ground spring pins are in contact with the metal layers on both sides. The signal spring pins are insulated from the metal layers on both sides. Metallized vias are also provided in the dielectric layer. The metallized vias are distributed around the signal spring pins, and the two ends of the metallized vias are in contact with the metal layers on both sides respectively. By providing metallized vias around the signal spring pins, the present invention can reduce crosstalk and impedance without changing the original number and arrangement of the spring pins; and the structure of the present invention is simple and easy to implement, and can be applied to various different styles of probe cards.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor testing, and particularly relates to a MEMS probe card and an impedance regulation method thereof. Background Art

[0002] With the improvement of semiconductor technology, integrated circuit chips are continuously developing towards high speed and high integration, and at the same time, high-frequency, small-pitch, and parallel testing design requirements are put forward for wafer testing systems. Micro-Electro-Mechanical System (MEMS) probe cards are widely used in high-frequency, high-density, and multi-chip parallel testing due to their good flatness, small X-Y alignment error, low contact force, and suitability for mass production. As an important part of the MEMS probe card, the interposer equipped with spring needles is responsible for connecting the printed circuit board (PCB) and the substrate, such as the multi-layer ceramic (MLC), and has an important impact on signal transmission. Therefore, the impedance regulation design of the interposer and the spring needles also needs to conform to the development trend of high-frequency and high-speed systems of wafer testing systems, but at present, such impedance regulation design is still an important challenge.

[0003] Most of the currently disclosed probe card impedance regulation technologies are based on vertical probe cards, and the impedance of the probe loop is regulated by increasing the number of vertical probes and fixing them with metal sheets to achieve the role of adjusting the matching. However, such methods are only applicable to vertical probe cards and are not suitable for cantilever MEMS probe cards; at the same time, the method of obtaining impedance regulation by increasing the number of probes further increases the assembly complexity of the probes. Summary of the Invention

[0004] The present invention provides a MEMS probe card and an impedance regulation method thereof to solve the above technical problems.

[0005] To solve the above technical problems, the present invention provides a MEMS probe card, including a PCB board, a substrate, and an interposer disposed between the two,

[0006] Spring needles are provided in the interposer, and both ends of the spring needles extend out of the upper and lower sides of the interposer and are respectively in contact with the PCB board and the substrate;

[0007] The interposer includes a dielectric layer and metal layers disposed on the upper and lower sides of the dielectric layer. The spring needles are divided into ground spring needles and signal spring needles. The ground spring needles are in contact with the metal layers on the upper and lower sides; the signal spring needles are isolated from the metal layers on the upper and lower sides;

[0008] The dielectric layer further has metallized vias, which are distributed around the signal spring pins, and both ends of the metallized vias are in contact with the metal layers on the upper and lower sides respectively.

[0009] Preferably, at least three metallized vias are distributed around each signal spring pin.

[0010] Preferably, the metallized vias are blocked between the signal spring pins and the ground spring pins, and between two adjacent signal spring pins.

[0011] Preferably, the ground spring pins are fixed in the dielectric layer through metal rails, and the metal rails are in contact with the metal layers.

[0012] Preferably, the signal spring pins are fixed in the dielectric layer through non-metal rails, and the non-metal rails are not in contact with the metal layers.

[0013] Preferably, a copper avoidance ring is provided at the position where the signal spring pins penetrate through the metal layer. The copper avoidance ring is sleeved on the signal spring pins and blocked between the metal layer and the signal spring pins.

[0014] Preferably, the central axis of the copper avoidance ring coincides with the central axis of the signal spring pins.

[0015] Preferably, the MEMS probe card further includes probes, which are fixed to the bottom of the substrate and matched with the chip under test.

[0016] Preferably, the MEMS probe card further includes a reinforcing plate, which fixes the PCB board and the substrate.

[0017] The present invention also provides an impedance regulation method for the MEMS probe card as described above, including: performing impedance regulation by controlling the diameter, quantity and relative position between the metallized vias and the signal spring pins.

[0018] Compared with the prior art, the MEMS probe card and its impedance regulation method provided by the present invention have the following advantages:

[0019] 1. The present invention utilizes an intermediate layer loaded with a metal layer and arranges metallized vias around the signal spring pins to realize impedance regulation of the spring pins with a simple structure, thereby improving the overall matching of the MEMS probe card;

[0020] 2. The present invention increases the signal return path and reduces the signal loop impedance by arranging the metallized vias between the ground spring pins and the signal spring pins, so that the MEMS probe card obtains broadband performance without changing the original number and arrangement of the spring pins;

[0021] 3. In the present invention, the metallized vias disposed between different signal spring pins can reduce the coupling between signals, lower crosstalk, and improve signal integrity;

[0022] 4. In the present invention, by adjusting the diameter and density of the metallized vias, the capacitive coupling between the signal spring pins and the metallized vias is regulated, thereby enhancing the low-frequency matching and then improving the transmission quality of the low-frequency components of the signals;

[0023] 5. In the present invention, the metal guide rail fixes the grounding spring pins through its own guide rail tolerance, while ensuring the electrical connection between the grounding spring pins and the metal layer, improving the grounding stability of the MEMS probe card. At the same time, the large-area metal layer can also improve the heat dissipation performance of the probe card. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic structural diagram of an MEMS probe card in a specific embodiment of the present invention;

[0025] Figure 2 is a schematic structural diagram of an interposer in a specific embodiment of the present invention;

[0026] Figure 3 is a top view of an interposer in a specific embodiment of the present invention;

[0027] Figure 4 is a schematic frequency response diagram of an MEMS probe card in a specific embodiment of the present invention.

[0028] In the figure: 10 - PCB board, 20 - substrate, 30 - interposer, 31 - dielectric layer, 32 - metal layer, 33 - metallized via, 40 - spring pin, 41 - grounding spring pin, 42 - metal guide rail, 43 - signal spring pin, 44 - non-metal guide rail, 45 - copper avoidance ring, 50 - probe, 60 - reinforcement plate. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] In order to describe the technical solutions of the above invention in more detail, specific examples are listed below to prove the technical effects; it should be emphasized that these examples are used to illustrate the present invention and not to limit the scope of the present invention.

[0030] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation and positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] The MEMS probe card provided by the present invention, as Figures 1 to 3 shown, includes a PCB board 10 (i.e., printed circuit board), a substrate 20 (such as a multi-layer co-fired ceramic MLC), and an intermediate layer 30 disposed between the two. The intermediate layer 30 can connect the PCB board 10 and the substrate 20, and then connect to a tester and a chip, and test the chip parameters by transmitting signals.

[0033] Among them: a spring needle 40 is provided inside the intermediate layer 30. Both ends of the spring needle 40 extend out of the upper and lower sides of the intermediate layer 30 and are respectively in contact with the PCB board 10 and the substrate 20. In this embodiment, the intermediate layer 30 and the spring needle 40 inside it are located between the PCB board 10 and the substrate 20, and are responsible for connecting the bottom of the PCB board 10 and the top of the substrate 20, so as to realize signal transmission.

[0034] Please refer to Figure 2 and Figure 3 for emphasis. The intermediate layer 30 includes a dielectric layer 31 and metal layers 32 disposed on the upper and lower sides of the dielectric layer 31. The dielectric layer 31 is made of a non-metallic material (such as silicon nitride, etc.), and metal layers 32 can be electroplated on the upper and lower surfaces of the dielectric layer 31. The large-area metal layers 32 can improve the heat dissipation performance of the probe card. The spring needle 40 can be divided into a ground spring needle 41 and a signal spring needle 43. In some embodiments, the ground spring needle 41 can be connected to a power supply terminal or a ground terminal according to the circuit design; the signal spring needle 43 can also include low-frequency signal needles and high-frequency signal needles to meet the needs of carrying various different signals. The ground spring needle 41 is in contact with the metal layers 32 on the upper and lower sides to ensure the electrical connection between the ground spring needle 41 and the metal layers 32; the signal spring needle 43 is insulated from the metal layers 31 on the upper and lower sides to avoid the problem of short circuit caused by the contact between the signal spring needle 43 and the metal layers 32.

[0035] Please refer to Figure 3, a plurality of metallized vias 33 are further provided in the dielectric layer 31. The metallized vias 33 are solid vias and can be entirely composed of a metal material, preferably copper. The metallized vias 33 are distributed around the signal spring pins 43. The two ends of the metallized vias 33 are respectively in contact with the metal layers 32 on the upper and lower sides, so as to play a role in reducing the loop impedance, adjusting the matching, and reducing crosstalk.

[0036] The present invention adopts the intermediate layer 30 loaded with the metal layer 32 and the metallized vias 33. Without changing the number and arrangement of the original spring pins 40, the purpose of reducing crosstalk and impedance regulation can be achieved, thereby improving the overall signal transmission quality of the MEMS probe card; at the same time, the present invention also has the characteristics of simple structure and easy implementation.

[0037] In some embodiments, at least three of the metallized vias 33 are distributed around each of the signal spring pins 43. In this embodiment, four of the metallized vias 33 are distributed around each of the signal spring pins 43, and the four metallized vias 33 are evenly distributed around the signal spring pins 43, as Figure 3 shown. For ease of observation and distinction, Figure 3 the "G" marked in the figure represents the ground spring pin 41, and the "S" represents the signal spring pin 43. In some embodiments, the metallized vias 33 are blocked between the signal spring pin 43 and the ground spring pin 41, thereby increasing the signal return path and reducing the signal loop impedance, so that the MEMS probe card obtains broadband performance without changing the number and arrangement of the original spring pins 40. In some embodiments, the metallized vias 33 are blocked between two adjacent signal spring pins 43 to reduce the coupling between signals, reduce crosstalk, and improve signal integrity.

[0038] In some embodiments, please continue to refer to Figure 2 and Figure 3 , the ground spring pin 41 is fixed in the dielectric layer 31 through a metal rail 42, and the metal rail 42 is in contact with the metal layer 32, so as to satisfy the electrical connection between the ground spring pin 41 and the metal layer 32; the signal spring pin 43 can be fixed in the dielectric layer 31 through a non-metal rail 44, and the non-metal rail 44 can satisfy the isolation effect between the signal spring pin 43 and the metal layer 32.

[0039] In some embodiments, please continue to refer to Figure 2 and Figure 3, the metal guide rail 42 and the non-metal guide rail 44 respectively fix the grounding spring pin 41 and the signal spring pin 43 by using their own rail tolerances. In this embodiment, the metal guide rail 42 fixes the grounding spring pin 41 through its own rail tolerance, further ensuring the electrical connection between the grounding spring pin 41 and the metal layer 32 and improving the grounding stability of the MEMS probe card.

[0040] In some embodiments, please continue to refer to Figure 2 and Figure 3 , a copper avoidance ring 45 is further provided at the position where the signal spring pin 43 passes through the metal layer 32. The copper avoidance ring 45 is sleeved on the signal spring pin 43 and blocks between the metal layer 32 and the signal spring pin 43, further avoiding short circuit caused by contact between the metal layer 32 and the signal spring pin 43. In some embodiments, the central axis of the copper avoidance ring 45 coincides with the central axis of the signal spring pin 43, that is, in the top view ( Figure 3 ), the center of the copper avoidance ring 45 is located on the central axis of the signal spring pin 43, further avoiding contact between the signal spring pin 43 and the metal layer 32. It should be noted that the copper avoidance ring 45 can be a real non-metal ring or a gap blocking between the signal spring pin 43 and the metal layer 32, as long as it can achieve an insulating effect.

[0041] In some embodiments, please focus on referring to Figure 1 , the MEMS probe card further includes a probe 50. The probe 50 is fixed to the bottom of the substrate 20 and matches with a chip to be tested (not shown). Connecting the probe 50 with the corresponding chip to be tested can perform the test.

[0042] In some embodiments, please focus on referring to Figure 1 , the MEMS probe card further includes a reinforcing plate 60. The reinforcing plate 60 fixes the PCB board 10 and the substrate 20, thereby fixing and protecting the overall assembly of the MEMS probe card. Without changing the number and arrangement of the original spring pins 40 in this application, the structure of this application can be adapted to various different styles of probe cards only through the design of the internal metallized vias 33.

[0043] Please continue to refer to Figures 1 to 3 , the present invention also provides an impedance regulation method for the MEMS probe card as described above, including: regulating the impedance by controlling the diameter, number and relative position between the metallized vias 33 and the signal spring pin 43. By adjusting the diameter and density of the metallized vias 33, the present invention can regulate the capacitive coupling between the signal spring pin 43 and the metallized vias 33, thereby improving the low-frequency matching and then improving the transmission quality of the signal low-frequency component.

[0044] For example Figures 1 to 3Taking the design structure of Figure 2 as an example, the frequency response shown in the figure is obtained. Among them, the dielectric layer 31 uses an FR4 substrate with a dielectric constant of 3.3, a loss angle of 0.003, and a thickness of 5.8 mm; the spring pins 40 (including the ground spring pins 41 and signal spring pins 43) have a diameter of 0.4 mm, and the distance between two adjacent spring pins 40 is 1 mm; the diameter of the metallized vias 33 is 0.2 mm. S 11 is the input matching, and S 21 is the gain / loss. As can be seen from Figure 2 , for the solution provided in this embodiment, the input matching is better than -25 dB within the 0-5 GHz passband, the input matching within the 5 GHz-10 GHz passband is better than -10 dB, the insertion loss is better than 0.53 dB, and the far-end crosstalk (FEXT) is less than -20 dB. Therefore, by reasonably designing the diameter and density of the metallized vias 33, the overall matching of the MEMS probe card can be improved and the crosstalk can be reduced.

[0045] In summary, the MEMS probe card and its impedance regulation method provided by the present invention. The structure includes a PCB board 10, a substrate 20, and an intermediate layer 30 disposed between the two. The intermediate layer 30 is provided with spring pins 40. The two ends of the spring pins 40 respectively extend out of the intermediate layer 30 and are in contact with the PCB board 10 and the substrate 20 respectively; the intermediate layer 30 includes a dielectric layer 31 and metal layers 32 disposed on the upper and lower sides of the dielectric layer 31. The spring pins 40 are divided into ground spring pins 41 and signal spring pins 43; the ground spring pins 41 are in contact with the metal layers 32 on the upper and lower sides; the signal spring pins 43 are isolated from the metal layers 32 on the upper and lower sides; the dielectric layer 31 is further provided with metallized vias 33. The metallized vias 33 are distributed around the signal spring pins 43, and the two ends of the metallized vias 33 are respectively in contact with the metal layers 32 on the upper and lower sides. The present invention can realize the impedance regulation of the spring pins 40 with a simple structure, thereby improving the overall matching of the MEMS probe card.

[0046] Obviously, those skilled in the art can make various changes and modifications to the invention without departing from the spirit and scope of the invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. A MEMS probe card, characterized in that, It includes a PCB board, a substrate, and an interposer disposed between the two. Spring pins are provided in the interposer. Both ends of the spring pins extend out of the upper and lower sides of the interposer and are respectively in contact with the PCB board and the substrate. The interposer includes a dielectric layer and metal layers disposed on the upper and lower sides of the dielectric layer. The spring pins are divided into ground spring pins and signal spring pins. The ground spring pins are in contact with the metal layers on the upper and lower sides. The signal spring pins are isolated from the metal layers on the upper and lower sides. Metalized vias are further provided in the dielectric layer. The metalized vias are distributed around the signal spring pins. Both ends of the metalized vias are respectively in contact with the metal layers on the upper and lower sides.

2. The MEMS probe card according to claim 1, characterized in that, At least three of the metalized vias are distributed around each signal spring pin.

3. The MEMS probe card according to claim 2, wherein The metalized vias are blocked between the signal spring pins and the ground spring pins, and between two adjacent signal spring pins.

4. The MEMS probe card according to claim 1, wherein The ground spring pins are fixed in the dielectric layer through metal rails, and the metal rails are in contact with the metal layers.

5. The MEMS probe card according to claim 1, wherein The signal spring pins are fixed in the dielectric layer through non-metal rails, and the non-metal rails are not in contact with the metal layers.

6. The MEMS probe card according to claim 1, wherein A copper avoidance ring is provided at the position where the signal spring pin penetrates through the metal layer. The copper avoidance ring is sleeved on the signal spring pin and is blocked between the metal layer and the signal spring pin.

7. The MEMS probe card according to claim 6, wherein, The central axis of the copper avoidance ring coincides with the central axis of the signal spring pin.

8. The MEMS probe card according to claim 1, wherein The MEMS probe card further includes probes, and the probes are fixed to the bottom of the substrate and are matched with the chip to be measured.

9. The MEMS probe card according to claim 1, wherein The MEMS probe card further includes a reinforcing plate, and the reinforcing plate fixes the PCB board and the substrate.

10. An impedance regulation method for a MEMS probe card according to any one of claims 1 to 9, characterized in that, It includes: Impedance regulation is performed by controlling the diameter, quantity, and relative position between the metalized vias and the signal spring pins.

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