Probe matching transition structure and film probe card
By employing a grounded coplanar waveguide structure and a transition structure in the thin-film probe card, the problem of high radiation loss in high-frequency signal transmission between thin-film transmission lines and PCB transmission lines is solved, achieving improved low radiation loss and high RF performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-03-10
AI Technical Summary
In existing thin-film probe cards, the coplanar waveguide structure of the thin-film transmission line and the PCB transmission line suffers from high radiation loss and poor isolation under high-frequency signal transmission, which affects RF performance.
By adopting a grounded coplanar waveguide structure, an electrical connection between an outer metal layer and the ground layer is added to the thin film and PCB transmission lines to form a closed or semi-closed metal shielding structure, the transmission mode is changed to CPWG, reducing radiation loss, and a transition structure is set at the interface between the signal layer and the metal pin header to alleviate parameter jumps.
It effectively reduces radiation loss in high-frequency signal transmission, improves radio frequency performance, and is suitable for thin-film probe card products with high requirements for radiation loss, thereby improving product development efficiency and stability.
Smart Images
Figure CN121633562A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of probe cards and wafer testing technology, specifically to a probe matching transition structure and a thin-film probe card. Background Technology
[0002] A thin-film probe card is a device used for testing chips. Its main function is to receive and transmit electrical signals from the chip to external testing equipment. In the transmission path, the signal needs to be transmitted from the thin-film transmission line to the transmission line on the PCB. During the signal transmission from the thin-film transmission line to the PCB transmission line, conduction is achieved through a metal connector. However, there is an impedance discontinuity at the junction of the metal connector and the two transmission lines (due to differences in their physical structures). A transition structure needs to be designed at this junction to achieve impedance matching, thereby ensuring low insertion loss and low radiation characteristics for high-frequency signal transmission.
[0003] The main electrical performance of a probe card includes three aspects: return loss, insertion loss, and isolation. Return loss represents the amount of energy a signal returns to the input port during transmission. Insertion loss represents the amount of energy transferred from the input port to the output port. Isolation, specifically for multi-channel scenarios, measures the energy transfer relationship between different channels, i.e., the ability to suppress mutual interference, reflecting the degree to which unwanted energy is coupled from one channel to other channels. The fundamental reason affecting isolation is excessive radiative coupling between channels in the transition structure, causing signals to radiate from one channel to other unrelated channels. This results in energy loss within the channel itself and interference between channels. From an energy conservation perspective, the more energy radiated out, the higher the insertion loss.
[0004] In existing technical solutions, both thin-film transmission lines and PCB transmission lines use coplanar waveguides (CPWs), with signal and ground layers only set on one side of the dielectric layer. This setup has the following problems: the coplanar waveguide (CPW) structure has high radiation loss under high-frequency signal transmission, which leads to increased insertion loss and poor isolation. This makes the coplanar waveguide (CPW) structure increasingly unsuitable for products such as thin-film probe cards with high requirements for radiation loss, affecting the improvement of the RF performance indicators of these products.
[0005] Therefore, how to overcome the shortcomings of the existing technology is the subject of this invention. Summary of the Invention
[0006] The purpose of this invention is to provide a probe matching transition structure and a thin-film probe card.
[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A probe matching transition structure includes a thin-film transmission line, a PCB transmission line, and multiple metal pin holders; The thin-film transmission line includes a first outer metal layer, a thin-film dielectric layer and a first inner metal layer that are sequentially stacked and connected; The first inner metal layer includes a first signal layer and a first ground layer; A first metal via is provided on the thin film dielectric layer, and the first outer metal layer is electrically connected to the first ground layer through the first metal via. The PCB transmission line includes a second outer metal layer, a PCB dielectric layer and a second inner metal layer that are sequentially stacked and connected; The second inner metal layer includes a second signal layer and a second ground layer; A second metal via is provided on the PCB dielectric layer, and the second outer metal layer is electrically connected to the second ground layer through the second metal via. The first ground layer and the second ground layer, as well as the first signal layer and the second signal layer, are each electrically connected through at least one of the metal pin sockets.
[0008] "Multiple" refers to at least two. The metal vias themselves are existing and have not been improved, such as the via wall material.
[0009] The first inner metal layer includes a first signal layer and a first ground layer, which together form a coplanar waveguide (CPW). Similarly, the second inner metal layer includes a second signal layer and a second ground layer, which together form a coplanar waveguide (CPW). The first ground layer and the second ground layer, as well as the first signal layer and the second signal layer, are each electrically connected through at least one metal pin, realizing the connection between the ground layers of the thin-film transmission line and the PCB transmission line, and the connection between the signal layers.
[0010] In a coplanar waveguide (CPW) structure, an insulating gap exists between the signal layer (e.g., the first signal layer) and the corresponding ground layer (e.g., the first ground layer). This gap causes significant electromagnetic radiation during high-frequency transmission in the CPW structure. As the frequency increases, electromagnetic field leakage in the gap region intensifies, and its radiation characteristics gradually approach the radiation behavior of a slot antenna, leading to increased signal radiation loss and potential electromagnetic interference to surrounding devices. Furthermore, in a CPW structure, the signal layer (e.g., the first signal layer) and the corresponding ground layer (e.g., the first ground layer) are located on the same side of the corresponding dielectric layer (e.g., a thin-film dielectric layer), and there is no complete grounding structure to shield the radiation after it is generated.
[0011] A first outer metal layer is added to the thin-film transmission line. The first outer metal layer is electrically connected to the first ground layer through a first metal via. The first outer metal layer and the first ground layer together constitute the reference ground of the first signal layer, forming a closed or semi-closed metal shielding structure, which can suppress the radiation intensity of the first signal layer. The first outer metal layer, the first ground layer, and the first signal layer together constitute a grounded coplanar waveguide (CPWG) structure.
[0012] A second outer metal layer is added to the PCB transmission line. This second outer metal layer is electrically connected to the second ground layer through a second metal via. Together, the second outer metal layer and the second ground layer constitute the reference ground of the second signal layer, forming a closed or semi-closed metal shielding structure that can suppress the radiation intensity of the second signal layer. The second outer metal layer, the second ground layer, and the second signal layer together constitute a grounded coplanar waveguide (CPWG) structure.
[0013] By employing a grounded coplanar waveguide (CPWG) structure, the operating mode of the thin-film transmission line and PCB transmission line is changed from CPW to CPWG, reducing radiation loss at the source. Simultaneously, the first and second outer metal layers, acting as a complete ground plane, provide a degree of shielding. The first outer metal layer and the first ground layer, together through a first metal via, form the reference ground of the first signal layer, and the second outer metal layer and the second ground layer, together through a second metal via, form the reference ground of the second signal layer, further enhancing the shielding effect. The grounded coplanar waveguide (CPWG) structure exhibits low radiation loss during high-frequency signal transmission, making it suitable for products such as thin-film probe cards with high requirements for radiation loss, thus promoting improvements in the RF performance of these products.
[0014] In a further technical solution, the first ground layer is configured as two, with the two first ground layers symmetrically arranged on both sides of the first signal layer; The second ground layer is configured as two, and the two second ground layers are symmetrically arranged on both sides of the second signal layer.
[0015] For example (the second grounding layer is similarly described below), the two first grounding layers form a double-sided symmetrical grounding layer to create a "lateral encirclement shield" for the first signal layer. The electromagnetic field is confined between the first signal layer and the two first grounding layers on both sides, thus improving the ability to suppress lateral interference.
[0016] In a further technical solution, the first grounding layer is electrically connected to the first outer metal layer through a plurality of first metal vias arranged side by side and evenly spaced. The second grounding layer is electrically connected to the second outer metal layer through multiple second metal vias arranged side by side and evenly spaced.
[0017] For example, multiple parallel-distributed first metal vias form a multi-point parallel conductive path, which reduces the current carrying capacity of a single first metal via, reduces heat generation and conduction losses, and avoids transmission performance limitations caused by concentrated current in a single via. Simultaneously, the dispersed multi-point connection prevents overall grounding interruption due to the failure of a single first metal via, improving long-term stability. Furthermore, the parallel-distributed, evenly distributed first metal vias facilitate batch processing such as PCB etching and electroplating, and the via position accuracy is easily controlled. Compared to irregular layouts, this reduces the impact of process errors on conductivity. Electromagnetic waves cannot penetrate metal; by using multiple parallel-distributed, evenly distributed first metal vias and controlling the gap between adjacent first metal vias (e.g., a gap of one-tenth of the wavelength), electromagnetic waves cannot leak through the gap, reducing external radiation.
[0018] In a further technical solution, a first abrupt change structure is formed at the junction of the first signal layer and the corresponding metal needle socket, and a second abrupt change structure is formed at the junction of the second signal layer and the corresponding metal needle socket. The first signal layer includes a first transmission line fixed on the thin film dielectric layer and a first transition structure connected to the first transmission line. The first transmission line and the corresponding metal pin seat form a conductive path through the first transition structure. The second signal layer includes a second transmission line fixed on the PCB dielectric layer and a second transition structure connected to the second transmission line. The second transmission line and the corresponding metal pin socket form a conductive path through the second transition structure.
[0019] The first transmission line and the first transition structure constitute a signal line, and the second transmission line and the second transition structure constitute a signal line.
[0020] The mutation structure (in general terms, not just referring to the first mutation structure) is not an independent physical component, but rather the interface region between two adjacent physical components (such as the first signal layer and the corresponding metal pin socket). Its core feature is a "step jump in physical / electrical parameters".
[0021] A transition structure (generally speaking, not limited to the first transition structure) is a physical conductive structure with continuously varying physical / electrical parameters. It is positioned between the signal layer (e.g., the first transmission line) and the abrupt change structure (e.g., the first abrupt change structure) to mitigate parameter jumps and achieve smooth signal transmission. The transition structure can be made of the same or compatible conductive material (e.g., copper or silver alloy) as the signal layer (e.g., copper foil) and the metal pin holder (e.g., brass). The transition structure can be integrally formed with the transmission line (e.g., through PCB etching) or fixed between the transmission line and the metal pin holder through electroplating or soldering. The transition structure can be a copper gradient conductive sheet.
[0022] The first transmission line and the corresponding metal pin socket form a conductive path through the first transition structure, and the second transmission line and the corresponding metal pin socket form a conductive path through the second transition structure. The transition structure avoids signal reflection and loss at the abrupt change structure.
[0023] In a further technical solution, a plurality of metal pin sockets are provided between the first transmission line and the second transmission line; the first transmission line and each corresponding metal pin socket form a conductive path through a plurality of first transition structures; the second transmission line and each corresponding metal pin socket form a conductive path through a plurality of second transition structures.
[0024] For example, when the first transmission line simultaneously interconnects with multiple metal pin sockets, multiple independent abrupt change structures will be formed at different locations of the first signal layer (each interconnection interface corresponds to one abrupt change structure). To adapt to the parameter transitions of each abrupt change structure, multiple independent first transition structures are electrically connected at the corresponding locations of the first signal layer. Each first transition structure is specifically adapted to only one abrupt change structure, achieving smooth signal transmission in each interconnection path. If only one first transition structure is used to connect the first transmission line and multiple metal pin sockets simultaneously, the first transition structure will need to adapt to multiple different transition parameters (such as the pin diameters of different metal pin sockets), making matching difficult. Furthermore, any parameter change in any metal pin socket will cause the first transition structure to fail, making modular design impossible. In this application, the method of independently transition matching for each abrupt change structure effectively avoids this problem.
[0025] In a further technical solution, both the first and second transmission lines are selected as transmission lines with a characteristic impedance of 50Ω, forming a buffer structure. 50 ohms is the characteristic impedance of the communication system, and the buffer structure is set as a standard 50-ohm impedance transmission line. Variations in the length of the standard impedance transmission line will not affect the impedance matching of the system. By inserting a standard impedance line between multiple consecutive abrupt changes, adjacent abrupt changes can be decoupled, preventing the preceding abrupt change from affecting the following abrupt change.
[0026] In summary, existing solutions use a single transition structure to achieve matching of multi-level mutation structures. This application uses an independent transition structure for each mutation structure to achieve matching, and adds 50-ohm transmission lines at both ends to buffer and decouple, realizing the modular design of each mutation structure. This allows the probe matching transition structure in this application to be quickly ported from one product to other similar products, thereby improving product development efficiency.
[0027] In a further technical solution, the first transition structure includes a first square conductive portion, and the first transmission line and the corresponding metal pin seat form a conductive path through the first square conductive portion. The second transition structure includes a second square conductive portion, and the second transmission line and the corresponding metal pin seat form a conductive path through the second square conductive portion.
[0028] For example, the first square conductive part has three important parameters: length parameter L, width parameter W, and spacing parameter S relative to the first ground layer. The structural dimensions of the first square conductive part are related to the operating frequency band and the dielectric constant of the corresponding dielectric layer, and its optimization requires the use of specialized simulation software. It should be noted that the radiation characteristics of the first transition structure need to be considered during simulation; generally, the values of L and W should be relatively small. Based on this, the return loss of the link is optimized to achieve good performance with high frequency and low radiation. The first square conductive part can be a square conductive sheet, a shape that facilitates adjustment of the length parameter L, width parameter W, and spacing parameter S. If the first square conductive part has an irregular structure, it is difficult to accurately determine the length parameter L, width parameter W, and spacing parameter S. Because the dielectric constants of the thin film dielectric layer and the PCB dielectric layer are different, the length parameter L, width parameter W, and spacing parameter S differ between thin films and PCBs.
[0029] For example, the first transition structure may include N integrally formed and sequentially arranged first square conductive parts (hereinafter referred to as square conductive parts), with the length and width of each square conductive part gradually increasing (or gradually decreasing, but described below as gradually increasing). The square conductive part with the largest length and width (located at one end of the N-order transition structure, where the length parameter L, width parameter W, and spacing parameter S of the N-order transition structure adopt the corresponding parameters of the square conductive part) is electrically connected to the corresponding metal pin socket, and the square conductive part with the smallest length and width (located at the other end of the N-order transition structure) is electrically connected to the first transmission line, thus forming an N-order transition structure. Generally, the higher the order of the transition structure, the wider the operating bandwidth that can be achieved. The specific number of orders can be adjusted according to the actual situation. For example, when a one-order transition structure can meet the operating bandwidth, only a one-order transition structure is needed; when a one-order transition structure cannot meet the operating bandwidth, a two-order transition structure can be used for matching.
[0030] A thin-film probe card is also provided herein, including a probe matching transition structure according to any of the above embodiments.
[0031] The terms "first," "second," etc., used in this article do not specifically refer to order or sequence, nor are they intended to limit this case; they are merely used to distinguish components or operations described using the same technical terms.
[0032] The terms "connection" or "positioning" as used in this article can refer to two or more components or devices making direct physical contact with each other, or making indirect physical contact with each other, or to two or more components or devices operating or moving with each other.
[0033] The terms “include,” “including,” and “have” used in this article are all open-ended, meaning they include but are not limited to.
[0034] Unless otherwise specified, the terms used herein generally have their ordinary meaning in the context of the art, the subject matter, and the specific context. Certain terms used to describe this case will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing this case.
[0035] The terms “front,” “back,” “up,” “down,” “left,” and “right” used in this article are directional terms. In this case, they are only used to describe the positional relationship between the structures and are not intended to limit the specific direction of the protection scheme or its actual implementation.
[0036] The working principle and advantages of this invention are as follows: The first inner metal layer includes a first signal layer and a first ground layer, which together form a coplanar waveguide (CPW). Similarly, the second inner metal layer includes a second signal layer and a second ground layer, which together form a coplanar waveguide (CPW). The first ground layer and the second ground layer, as well as the first signal layer and the second signal layer, are each electrically connected through at least one metal pin, realizing the connection between the ground layers of the thin-film transmission line and the PCB transmission line, and the connection between the signal layers.
[0037] In a coplanar waveguide (CPW) structure, an insulating gap exists between the signal layer (e.g., the first signal layer) and the corresponding ground layer (e.g., the first ground layer). This gap causes significant electromagnetic radiation during high-frequency transmission in the CPW structure. As the frequency increases, electromagnetic field leakage in the gap region intensifies, and its radiation characteristics gradually approach the radiation behavior of a slot antenna, leading to increased signal radiation loss and potential electromagnetic interference to surrounding devices. Furthermore, in a CPW structure, the signal layer (e.g., the first signal layer) and the corresponding ground layer (e.g., the first ground layer) are located on the same side of the corresponding dielectric layer (e.g., a thin-film dielectric layer), and there is no complete grounding structure to shield the radiation after it is generated.
[0038] A first outer metal layer is added to the thin-film transmission line. The first outer metal layer is electrically connected to the first ground layer through a first metal via. The first outer metal layer and the first ground layer together constitute the reference ground of the first signal layer, forming a closed or semi-closed metal shielding structure, which can suppress the radiation intensity of the first signal layer. The first outer metal layer, the first ground layer, and the first signal layer together constitute a grounded coplanar waveguide (CPWG) structure.
[0039] A second outer metal layer is added to the PCB transmission line. This second outer metal layer is electrically connected to the second ground layer through a second metal via. Together, the second outer metal layer and the second ground layer constitute the reference ground of the second signal layer, forming a closed or semi-closed metal shielding structure that can suppress the radiation intensity of the second signal layer. The second outer metal layer, the second ground layer, and the second signal layer together constitute a grounded coplanar waveguide (CPWG) structure.
[0040] By employing a grounded coplanar waveguide (CPWG) structure, the operating mode of the thin-film transmission line and PCB transmission line is changed from CPW to CPWG, reducing radiation loss at the source. Simultaneously, the first and second outer metal layers, acting as a complete ground plane, provide a degree of shielding. The first outer metal layer and the first ground layer, together through a first metal via, form the reference ground of the first signal layer, and the second outer metal layer and the second ground layer, together through a second metal via, form the reference ground of the second signal layer, further enhancing the shielding effect. The grounded coplanar waveguide (CPWG) structure exhibits lower radiation loss in high-frequency signal transmission. This reduction in radiation loss further lowers the insertion loss of the transmission link, making it suitable for products such as thin-film probe cards with high requirements for radiation loss, effectively improving the RF transmission performance of high-frequency thin-film probe cards and similar products. Attached Figure Description
[0041] Appendix Figure 1 This is a schematic diagram of the probe matching transition structure according to an embodiment of the present invention; Appendix Figure 2 This is a schematic diagram of the structure of the first inner metal layer in an embodiment of the present invention; Appendix Figure 3 For the appendix Figure 2 Enlarged view of point A in the middle; Appendix Figure 4 This is a schematic diagram of the structure of the second inner metal layer in an embodiment of the present invention; Appendix Figure 5 This is a simulation comparison diagram of the return loss between the improved scheme of this invention and the existing scheme; Appendix Figure 6 This is a simulation comparison diagram of the insertion loss between the improved scheme of this invention and the existing scheme; Appendix Figure 7 This is a comparison chart of the radiation power simulation between the improved scheme of this invention and the existing scheme.
[0042] 1. Thin-film transmission line; 11. First outer metal layer; 12. Thin-film dielectric layer; 121. First metal via; 13. First inner metal layer; 131. First signal layer; 1311. First transmission line; 1312. First transition structure; 1312a. First square conductive part; 132. First ground layer; 2. PCB transmission line; 21. Second outer metal layer; 22. PCB dielectric layer; 221. Second metal via; 23. Second inner metal layer; 231. Second signal layer; 2311. Second transmission line; 2312. Second transition structure; 2312a. Second square conductive part; 232. Second ground layer; 3. Metal needle hub. Detailed Implementation
[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments: Example: The present invention will be clearly described below with illustrations and detailed description. Any person skilled in the art who understands the examples of the present invention can make changes and modifications based on the technology taught in the present invention without departing from the spirit and scope of the present invention.
[0044] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the scope of this work. Singular forms such as “a,” “this,” “this,” “the,” and “the” as used herein also include plural forms.
[0045] See appendix Figure 1 -Appendix Figure 4 A probe matching transition structure includes a thin-film transmission line 1, a PCB transmission line 2, and multiple metal pin holders 3; The thin-film transmission line 1 includes a first outer metal layer 11, a thin-film dielectric layer 12 and a first inner metal layer 13 that are sequentially stacked and connected; The first inner metal layer 13 includes a first signal layer 131 and a first ground layer 132; A first metal via 121 is provided on the thin film dielectric layer 12, and the first outer metal layer 11 is electrically connected to the first ground layer 132 through the first metal via 121. The PCB transmission line 2 includes a second outer metal layer 21, a PCB dielectric layer 22 and a second inner metal layer 23 that are sequentially stacked and connected; The second inner metal layer 23 includes a second signal layer 231 and a second ground layer 232; A second metal via 221 is provided on the PCB dielectric layer 22, and the second outer metal layer 21 is electrically connected to the second ground layer 232 through the second metal via 221. The first ground layer 132 and the second ground layer 232, and the first signal layer 131 and the second signal layer 231 are respectively electrically connected through at least one of the metal pin seats 3.
[0046] "Multiple" refers to at least two. The metal vias themselves are existing and have not been modified, such as the via wall material. The dielectric layers in this embodiment have not undergone material modifications based on existing technology.
[0047] The first inner metal layer 13 includes a first signal layer 131 and a first ground layer 132, which together form a coplanar waveguide (CPW). Similarly, the second inner metal layer 23 includes a second signal layer 231 and a second ground layer 232, which together form a coplanar waveguide (CPW). The first ground layer 132 and the second ground layer 232, as well as the first signal layer 131 and the second signal layer 231, are each electrically connected through at least one metal pin 3, realizing the connection between the ground layers of the thin-film transmission line 1 and the PCB transmission line 2, and the connection between the signal layers.
[0048] In a coplanar waveguide (CPW) structure, an insulating gap exists between the signal layer (e.g., the first signal layer 131) and the corresponding ground layer (e.g., the first ground layer 132). This gap causes significant electromagnetic radiation during high-frequency transmission in the CPW structure. As the frequency increases, electromagnetic field leakage in the gap region intensifies, and its radiation characteristics gradually approach the radiation behavior of a slot antenna, leading to increased signal radiation loss and potential electromagnetic interference to surrounding devices. Furthermore, in the CPW structure, the signal layer (e.g., the first signal layer 131) and the corresponding ground layer (e.g., the first ground layer 132) are located on the same side of the corresponding dielectric layer (e.g., the thin-film dielectric layer 12), and there is no complete grounding structure to shield the radiation after it is generated.
[0049] A first outer metal layer 11 is added to the thin-film transmission line 1. The first outer metal layer 11 is electrically connected to the first ground layer 132 through a first metal via 121. The first outer metal layer 11 and the first ground layer 132 together constitute the reference ground of the first signal layer 131, forming a closed or semi-closed metal shielding structure, which can suppress the radiation intensity of the first signal layer 131. The first outer metal layer 11, the first ground layer 132, and the first signal layer 131 together constitute a grounded coplanar waveguide (CPWG) structure.
[0050] A second outer metal layer 21 is added to the PCB transmission line 2. The second outer metal layer 21 is electrically connected to the second ground layer 232 through a second metal via 221. The second outer metal layer 21 and the second ground layer 232 together constitute the reference ground of the second signal layer 231, forming a closed or semi-closed metal shielding structure, which can suppress the radiation intensity of the second signal layer 231. The second outer metal layer 21, the second ground layer 232, and the second signal layer 231 together constitute a grounded coplanar waveguide (CPWG) structure.
[0051] By adopting a grounded coplanar waveguide (CPWG) structure, the operating mode of the thin-film transmission line 1 and the PCB transmission line 2 is changed from CPW to CPWG, which reduces radiation loss at the source. Simultaneously, the first outer metal layer 11 and the second outer metal layer 21, as a complete ground plane, provide a certain degree of shielding. The first outer metal layer 11 and the first ground layer 132 together form the reference ground of the first signal layer 131 through the first metal via 121, and the second outer metal layer 21 and the second ground layer 232 together form the reference ground of the second signal layer 231 through the second metal via 221, further enhancing the shielding effect. The grounded coplanar waveguide (CPWG) structure exhibits lower radiation loss in high-frequency signal transmission. This reduction in radiation loss further lowers the insertion loss of the transmission link, making it suitable for products such as thin-film probe cards with high requirements for radiation loss, effectively improving the RF transmission performance of high-frequency thin-film probe cards and similar products. There are two main ways to improve electromagnetic radiation, which are supplemented below: On the one hand, the generation of radiation sources can be avoided from the source. For example, the CPW structure is close to the monopole antenna structure and is itself a good radiation source. Changing the working mode of the thin film transmission line 1 and the PCB transmission line 2 from CPW to CPWG can reduce radiation loss from the source. On the other hand, if radiation has already occurred, the transmission path can be cut off, such as by using a metal shielding structure to reduce external radiation. In PCB transmission line 2, a uniformly arranged metal grounding via (such as the second metal via 221) can be used to replace the metal shielding structure. If the gap between the metal grounding vias is very small, for example, less than one-tenth of the wavelength, electromagnetic waves will have difficulty passing through the gap to penetrate and leak. However, when the gap is too large, electromagnetic waves may leak from the gap, causing radiation. The gap between the metal grounding vias can be selected according to the operating frequency band and is not limited here.
[0052] In this embodiment, two first ground layers 132 are provided, and the two first ground layers 132 are symmetrically arranged on both sides of the first signal layer 131. Two second ground layers 232 are provided, and the two second ground layers 232 are symmetrically arranged on both sides of the second signal layer 231.
[0053] For example (refer to this example for the second grounding layer 232, and the examples below are similar), the two first grounding layers 132 form a double-sided symmetrical grounding layer to form a "lateral encircling shield" for the first signal layer 131. The electromagnetic field is confined between the first signal layer 131 and the two first grounding layers 132 on both sides, thereby improving the ability to suppress lateral interference.
[0054] In this embodiment, the first ground layer 132 is electrically connected to the first outer metal layer 11 through a plurality of first metal vias 121 arranged side by side and evenly spaced. The second grounding layer 232 is electrically connected to the second outer metal layer 21 through a plurality of second metal vias 221 arranged side by side and evenly spaced.
[0055] For example, multiple parallel-distributed first metal vias 121 form a multi-point parallel conductive path, which reduces the current carrying capacity of a single first metal via 121, reduces heat generation and conduction losses, and avoids transmission performance limitations caused by concentrated current in a single via. Simultaneously, the dispersed multi-point connection prevents overall grounding interruption due to the failure of a single first metal via 121, improving long-term stability. Furthermore, the parallel-distributed first metal vias 121 facilitate batch processing such as PCB etching and electroplating, and the hole position accuracy is easily controlled. Compared to irregular layouts, this reduces the impact of process errors on conductivity. Since electromagnetic waves cannot penetrate metal, by using multiple parallel-distributed first metal vias 121 and controlling the gap between adjacent first metal vias 121 (e.g., a gap of one-tenth of the wavelength), electromagnetic waves cannot leak from the gap, reducing external radiation.
[0056] In this embodiment, a first abrupt change structure is formed at the junction of the first signal layer 131 and the corresponding metal pin seat 3, and a second abrupt change structure is formed at the junction of the second signal layer 231 and the corresponding metal pin seat 3. The first signal layer 131 includes a first transmission line 1311 fixed on the thin film dielectric layer 12 and a first transition structure 1312 connected to the first transmission line 1311. The first transmission line 1311 and the corresponding metal pin seat 3 form a conductive path through the first transition structure 1312. The second signal layer 231 includes a second transmission line 2311 fixed on the PCB dielectric layer 22 and a second transition structure 2312 connected to the second transmission line 2311. The second transmission line 2311 and the corresponding metal pin seat 3 form a conductive path through the second transition structure 2312.
[0057] The first transmission line 1311 and the first transition structure 1312 constitute a signal line, and the second transmission line 2311 and the second transition structure 2312 constitute a signal line.
[0058] The mutation structure (in general terms, such as not only referring to the first mutation structure) is not an independent physical component, but rather the interface region between two adjacent physical components (such as the first signal layer 131 and the corresponding metal pin seat 3). Its core feature is a "step jump in physical / electrical parameters".
[0059] The transition structure (general description, e.g., not just referring to the first transition structure 1312) is a physical conductive structure with continuously varying physical / electrical parameters. It is positioned between the signal layer (e.g., the first transmission line 1311) and the abrupt change structure (e.g., the first abrupt change structure) to mitigate parameter jumps and achieve smooth signal transmission. The transition structure can be made of the same or compatible conductive material (e.g., copper or silver alloy) as the signal layer (e.g., copper foil) and the metal pin holder 3 (e.g., brass). The transition structure can be integrally formed with the transmission line (e.g., through PCB etching) or fixed between the transmission line and the metal pin holder 3 through electroplating or soldering. The transition structure can be a copper gradient conductive sheet.
[0060] The first transmission line 1311 and the corresponding metal pin socket 3 form a conductive path through the first transition structure 1312, and the second transmission line 2311 and the corresponding metal pin socket 3 form a conductive path through the second transition structure 2312. The setting of the transition structure avoids signal reflection and loss at the abrupt change structure.
[0061] In this embodiment, a plurality of metal pin holders 3 are provided between the first transmission line 1311 and the second transmission line 2311; the first transmission line 1311 and each corresponding metal pin holder 3 form a conductive path through a plurality of first transition structures 1312; the second transmission line 2311 and each corresponding metal pin holder 3 form a conductive path through a plurality of second transition structures 2312.
[0062] For example, when the first transmission line 1311 is interconnected with multiple metal pin sockets 3 simultaneously, multiple independent abrupt change structures will be formed at different positions of the first signal layer 131 (each interconnection interface corresponds to one abrupt change structure). To adapt to the parameter jumps of each abrupt change structure, multiple independent first transition structures 1312 are electrically connected at the corresponding positions of the first signal layer 131. Each first transition structure 1312 is specifically adapted to only one abrupt change structure, realizing smooth signal transmission of each interconnection path. If only one first transition structure 1312 is used to connect the first transmission line 1311 and multiple metal pin sockets 3 simultaneously, the first transition structure 1312 will need to adapt to multiple different jump parameters (such as the pin diameters of different metal pin sockets 3) at the same time, which is difficult to match. Moreover, if any metal pin socket 3 changes its parameters, the first transition structure 1312 will fail, making modular design impossible. In this embodiment, the method of performing independent transition matching for each abrupt change structure effectively avoids this problem.
[0063] In this embodiment, both the first transmission line 1311 and the second transmission line 2311 are selected as transmission lines with a characteristic impedance of 50Ω, forming a buffer structure. 50 ohms is the characteristic impedance of the communication system, and the buffer structure is set as a standard impedance transmission line of 50 ohms. Variations in the length of the standard impedance transmission line will not affect the impedance matching of the system. By inserting a standard impedance line between multiple consecutive abrupt changes, adjacent abrupt changes can be decoupled, preventing the preceding abrupt change from affecting the following abrupt change.
[0064] In summary, existing solutions use a single transition structure to match multi-level mutation structures. This embodiment uses an independent transition structure for each mutation structure to achieve matching, and adds 50-ohm transmission lines at both ends to buffer and decouple, realizing the modular design of each mutation structure. This allows the probe matching transition structure in this embodiment to be quickly ported from one product to other similar products, thereby improving product development efficiency.
[0065] In this embodiment, the first transition structure 1312 includes a first square conductive portion 1312a, and the first transmission line 1311 and the corresponding metal pin seat 3 form a conductive path through the first square conductive portion 1312a. The second transition structure 2312 includes a second square conductive portion 2312a, and the second transmission line 2311 and the corresponding metal pin seat 3 form a conductive path through the second square conductive portion 2312a.
[0066] For example, the first square conductive portion 1312a has three important parameters: length parameter L, width parameter W, and spacing parameter S with the first ground layer 132. The structural dimensions of the first square conductive portion 1312a are related to the operating frequency band and the dielectric constant of the corresponding dielectric layer, and its optimization process requires the use of specialized simulation software. It should be noted that the radiation characteristics of the first transition structure 1312 need to be considered during simulation; generally, the values of L and W should be relatively small. Based on this, the return loss of the link is optimized to achieve good performance with high frequency and low radiation. The first square conductive portion 1312a can be a square conductive sheet. This shape facilitates the adjustment of the length parameter L, width parameter W, and spacing parameter S. If the first square conductive portion 1312a has an irregular structure, it is difficult to accurately determine the length parameter L, width parameter W, and spacing parameter S. Because the dielectric constants of the thin film dielectric layer 12 and the PCB dielectric layer 22 are different, the length parameter L, width parameter W, and spacing parameter S differ between the thin film and the PCB.
[0067] For example, the first transition structure 1312 may include N integrally formed and sequentially arranged first square conductive parts 1312a (hereinafter referred to as square conductive parts), with the length and width of each square conductive part gradually increasing (or gradually decreasing, but described below as gradually increasing). The square conductive part with the largest length and width (located at one end of the N-order transition structure, where the length parameter L, width parameter W, and spacing parameter S of the N-order transition structure adopt the corresponding parameters of the square conductive part) is electrically connected to the corresponding metal pin seat 3, and the square conductive part with the smallest length and width (located at the other end of the N-order transition structure) is electrically connected to the first transmission line 1311, thus forming an N-order transition structure. Generally, the higher the order of the transition structure, the wider the operating bandwidth that can be achieved. The specific number of orders can be adjusted according to the actual situation. For example, when a one-order transition structure can meet the operating bandwidth, only a one-order transition structure is needed; when a one-order transition structure cannot meet the operating bandwidth, a two-order transition structure can be used for matching.
[0068] A thin-film probe card is also provided herein, including a probe matching transition structure from any of the above embodiments.
[0069] The electromagnetic energy on the signal line is relatively concentrated, resulting in strong external radiation. The existing scheme uses a relatively wide signal line, approximately 0.36 mm, which is comparable to the wavelength at high frequencies; for example, the air wavelength at 110 GHz is 2.73 mm. Assuming the dielectric constant of the dielectric layer is 3.0, the dielectric wavelength is approximately 1.57 mm, meaning the linewidth is about 1 / 4 wavelength. According to antenna radiation theory, the length of a dipole antenna is half a wavelength, and the length of a monopole antenna is 1 / 4 wavelength. In the existing scheme, the width of the transition structure at 110 GHz is already equal to the length of a monopole antenna, leading to very strong radiation.
[0070] An optimized solution is provided to address the issue of strong radiation caused by existing technology: Based on the dielectric constants of the existing PCB dielectric layer and thin film dielectric layer, the dimensions of the second transition structure were optimized (optimizing the dimensions of the first transition structure can also achieve similar results, but optimizing both the first and second transition structures simultaneously yields better results). Both the first and second transition structures adopt a first-order transition structure. Table 1 compares the transition structure dimensions of the improved scheme and the existing scheme: Table 1 Dimensions of the transition structure
[0071] The parameters in Table 1 are affected by the dielectric layer material of the PCB transmission line and the thin film transmission line. In actual use, this solution is still applicable after changing the dielectric layer material, but the dimensional parameters of the corresponding transition structure need to be adjusted.
[0072] According to the simulation comparison chart of return loss below, the return loss of the existing solution is greater than -10dB after 100GHz, while the improved solution is less than -15dB within 110GHz, showing a significant improvement in return loss. By optimizing the size of the transition structure, the highest operating frequency band has been increased to 110GHz, effectively expanding the working range of the probe card.
[0073] Based on the following simulation comparison chart of insertion loss, after 60GHz, the insertion loss of the improved scheme is significantly better than that of the existing scheme.
[0074] Radiated power represents the ratio of the power radiated by an electromagnetic signal to the input power; the smaller the value, the less radiated energy. According to the following simulation comparison chart of radiated power, the existing scheme has a radiated power of approximately 0.183 at 110 GHz, while the improved scheme has a radiated power of approximately 0.035 at 110 GHz, which is equivalent to a reduction of 80% in radiated power.
[0075] In summary, the existing solution's transition structure is too large. Although the return loss meets the requirements, the insertion loss is high because the transition structure radiates too strongly, causing some energy to be radiated into the air or even into other unrelated channels. This not only results in energy loss but also introduces signal crosstalk. To address this issue, this solution (the improved solution) reduces the size of the transition structure, thereby suppressing radiation and ensuring that the return loss meets the requirements of current products (such as thin-film probe cards). It also allows the highest operating frequency of current products to be increased to 110GHz.
[0076] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A probe matching transition structure, characterized in that: Thin film transmission line (1), PCB transmission line (2) and a plurality of metal needle seat (3) are included. The thin film transmission line (1) includes sequentially laminated first outer metal layer (11), thin film dielectric layer (12) and first inner metal layer (13). The first inner metal layer (13) includes first signal layer (131) and first ground layer (132). The first metal via (121) is provided on the thin film dielectric layer (12), and the first outer metal layer (11) is electrically connected with the first ground layer (132) through the first metal via (121). The PCB transmission line (2) includes sequentially laminated second outer metal layer (21), PCB dielectric layer (22) and second inner metal layer (23). The second inner metal layer (23) includes second signal layer (231) and second ground layer (232). The second metal via (221) is provided on the PCB dielectric layer (22), and the second outer metal layer (21) is electrically connected with the second ground layer (232) through the second metal via (221). The first ground layer (132) and the second ground layer (232), the first signal layer (131) and the second signal layer (231) are respectively electrically connected through at least one metal needle seat (3).
2. A probe matching transition structure according to claim 1, wherein: The first ground layer (132) is provided as two, and the two first ground layers (132) are symmetrically arranged on the symmetric two sides of the first signal layer (131). The second ground layer (232) is provided as two, and the two second ground layers (232) are symmetrically arranged on the symmetric two sides of the second signal layer (231).
3. The probe matching transition structure of claim 1, wherein: The first ground layer (132) is electrically connected with the first outer metal layer (11) through a plurality of first metal vias (121) arranged side by side and uniformly distributed. The second ground layer (232) is electrically connected with the second outer metal layer (21) through a plurality of second metal vias (221) arranged side by side and uniformly distributed.
4. A probe-matched transition structure according to any one of claims 1-3, wherein: The first signal layer (131) and the corresponding metal needle seat (3) form a first mutation structure, and the second signal layer (231) and the corresponding metal needle seat (3) form a second mutation structure. The first signal layer (131) includes first transmission line (1311) fixed on the thin film dielectric layer (12) and first transition structure (1312) connected to the first transmission line (1311), and the first transmission line (1311) and the corresponding metal needle seat (3) form a conductive path through the first transition structure (1312). The second signal layer (231) includes second transmission line (2311) fixed on the PCB dielectric layer (22) and second transition structure (2312) connected to the second transmission line (2311), and the second transmission line (2311) and the corresponding metal needle seat (3) form a conductive path through the second transition structure (2312).
5. A probe matching transition structure according to claim 4, wherein: A plurality of the metal needle holders (3) are arranged between the first transmission line (1311) and the second transmission line (2311); the first transmission line (1311) and each corresponding metal needle holder (3) form a conductive path through a plurality of the first transition structures (1312); the second transmission line (2311) and each corresponding metal needle holder (3) form a conductive path through a plurality of the second transition structures (2312).
6. A probe matching transition structure according to claim 5, wherein: The first transmission line (1311) and the second transmission line (2311) are both selected as transmission lines with a characteristic impedance of 50Ω.
7. A probe matching transition structure according to claim 4, wherein: The first transition structure (1312) comprises a first square conductive part (1312a), and the first transmission line (1311) and each corresponding metal needle holder (3) form a conductive path through the first square conductive part (1312a); The second transition structure (2312) comprises a second square conductive part (2312a), and the second transmission line (2311) and each corresponding metal needle holder (3) form a conductive path through the second square conductive part (2312a).
8. A thin film probe card, characterized by: A probe matching transition structure comprising any one of claims 1-7.