Design method of multifunctional asymmetric laminated structure high-speed test fixture

Abstract

The application discloses a design method of a multifunctional asymmetric laminated structure high-speed test fixture. The application comprises the following steps: firstly, designing an asymmetric laminated PCB high-speed test fixture for a specific device; then, calculating specific PCB size parameters, establishing a three-dimensional simulation model to comprehensively analyze transmission performance, and completing actual processing and product inspection; finally, completing accelerated degradation test and corresponding high-frequency high-speed test analysis of the communication electronic device with the help of the test fixture. The method has the following characteristics: the environmental stress of the high-frequency high-speed communication electronic device in various application scenarios is considered; the test fixture meets the thickness requirement of the specific device, and the test fixture realizes good mechanical and electrical performance at a low manufacturing cost. Through the method, the high-frequency high-speed signal transmission performance of the communication electronic device before and after degradation in different application environments can be effectively detected, and the test fixture design in the device reliability detection has reference value.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electromagnetic field and microwave technology and high-speed interconnection technology, and in particular to a design method of a multifunctional asymmetric laminated structure high-speed test fixture. BACKGROUND

[0002] With the rapid development of integrated circuits, the data transmission rate of communication systems is becoming higher and higher, and the requirements of electronic products in terms of high density and high reliability are increasing. In order to cope with different integrated scenarios, electronic devices usually design special interconnection structures, so whether it is mechanical quality inspection or electrical performance test, a fixture that meets the structural interconnection requirements of the communication electronic device needs to be designed. In addition, the physical channel structure of the wire is difficult to avoid damage to the device due to external factors during long-term use, which will change the high-frequency performance of the device and affect the transmission of high-speed signals. According to different use occasions, the material performance and contact performance of communication electronic devices may be affected by environmental stresses such as temperature, humidity, salt spray, and vibration, resulting in degradation or even failure, thereby affecting the overall performance of the system. Therefore, for various environmental factors that may cause interconnection degradation or even product failure, corresponding environmental stress accelerated degradation tests need to be designed, and corresponding auxiliary fixtures are also essential in order to better simulate the actual application scenarios of electronic devices and their degradation mechanisms. For example, the adapter structure used in the plug-in mode and in pairs (such as the use of high-speed backplane connectors) is more susceptible to vibration stress, whether it is the inevitable vibration stress in the natural working environment or the random vibration caused by human operation and system maintenance. At the same time, such interconnection adapter structures are usually specially designed according to the thickness of the working circuit board, so it is very important to research and develop a test fixture that can not only detect the high-frequency and high-speed performance of such special adapter structures but also simulate the vibration scenarios in the actual application process.

[0003] At present, for the ever-increasing integrated interconnection device structure, the manufacturing process and theoretical basis of the test fixture have been perfected, but in the field of electromagnetic field and microwave technology and high-speed interconnection, researchers pay more attention to the high-frequency and high-speed signal transmission performance of the test fixture, and less attention to the degradation and failure of the device caused by environmental stress, resulting in a single function of the test fixture. At the same time, the design of the test fixture usually adopts the traditional symmetric structure, which will bring additional manufacturing cost for some application scenarios. Therefore, after considering the environmental stress in the actual application scenario of the communication electronic device and the test requirements of its high-frequency and high-speed transmission performance, the present application proposes a design method of a multifunctional asymmetric laminated structure high-speed test fixture. SUMMARY

[0004] In order to solve the above problems in the prior art, the application provides a design method of a multifunctional asymmetric laminated structure high-speed test fixture, which processes and manufactures a PCB high-speed test fixture sample according to the actual use scene of a communication electronic device, combines theoretical calculation and modeling simulation results, and verifies the excellent function of the designed asymmetric laminated test fixture through accelerated degradation test and high-frequency high-speed experiment multi-angle, and the technical scheme adopted by the application is as follows:

[0005] According to the actual use scene of a high-frequency high-speed communication electronic device, the thickness and corresponding asymmetric laminated structure of a PCB high-speed test fixture are determined, and the specific laminated information and size parameters of the test fixture are determined by combining theoretical calculation and simulation modeling, including: based on the microwave generalized transmission line theory, the PCB transmission line size parameters meeting the high-frequency impedance matching requirement are calculated; then, a three-dimensional electromagnetic field finite element model of the PCB high-speed test fixture is established, the characteristic impedance curve is simulated and analyzed through TDR technology, and the high-frequency high-speed transmission performance is comprehensively studied, so as to ensure from the simulation angle that the PCB high-speed test fixture can meet the specific board thickness use requirement of the device and the characteristic impedance and other electromagnetic performance requirements of the microwave radio frequency band.

[0006] Based on the three-dimensional structure parameters of the electromagnetic field numerical calculation model, appropriate dielectric materials are selected to process and manufacture the PCB high-speed test fixture, and in order to guarantee the operation quality and efficiency of the entire experimental test system, the mechanical performance and electrical performance of the PCB high-speed test fixture product need to be further tested, so as to guarantee from the measured angle that the PCB high-speed test fixture can meet the special structure connection requirement of the communication electronic device and the use condition in the high-speed interconnection field, including: product thickness, plate curvature test, PCB wiring line width, gap test, via size test, line characteristic impedance detection, etc. Among them, the single-ended characteristic impedance of the line can be tested by using TDR instrument, and according to the use requirement of different communication electronic devices, the differential impedance can be further tested by using differential TDR accessories; in addition, except for the ground layer, the scheme of laying copper in the bottom layer non-signal wiring interconnection area can be adopted, so as to further reduce the influence of the in-plate stress of the asymmetric laminated structure on the PCB warping degree.

[0007] Finally, with the help of the test fixture, the high-frequency high-speed signal transmission performance of the device before and after degradation is comprehensively analyzed through accelerated degradation test and high-frequency high-speed test, and the excellent function of the designed asymmetric stacked test fixture is verified from multiple angles. Among them, in order to make the test results closer to the actual use of the device, the high-speed transmission channel with the test fixture is tested by using the cross method of accelerated degradation test and high-frequency high-speed test. In addition, in the actual PCB interconnection system, in addition to the interconnection with external instruments, the interconnection structure inside the system generally does not need a radio frequency connector, but the radio frequency connector is necessary in the non-probe test. Therefore, in order to strictly control the variables, the fixture reserves a position and formulates a corresponding connection structure at the beginning of the design, so that the fixture can use a high-performance microwave radio frequency connector that can be repeatedly disassembled without welding. The radio frequency connector used to connect with other experimental instruments is removed in the accelerated degradation test, thereby avoiding the degradation influence of the welding points, radio frequency connectors and other parts, and further improving the reliability and practical application value of the method.

[0008] Compared with the prior art, the design method of the multifunctional asymmetric stacked structure high-speed test fixture has the following advantages:

[0009] (1) Unlike the common PCB symmetric stack, the asymmetric stack structure adopted in the present application can meet the allowable characteristic impedance error of edge-coupled differential microstrip line single-ended 50Ω, differential 100Ω and common mode 25Ω in engineering application under the premise of meeting the actual use scene of the electronic device. The design of the asymmetric stack not only saves cost, but also realizes a PCB warping degree of only 0.28% without additional copper paving in the non-signal layer wiring interconnection area.

[0010] (2) The test fixture designed in the present application not only has high-frequency high-speed test function, but also considers the degradation mechanism of communication electronic devices and their interconnection structure under environmental stress, and can be used to design corresponding accelerated degradation test, and has the auxiliary function of studying the damage influence of environmental stress on the transmission performance of electronic devices. In addition, the reserved structure of the test fixture for the detachable radio frequency connector connected to the outside for measurement can strictly control the variables in the degradation test, so as to focus the influence of environmental stress on the device itself, and enhance the accuracy of reliability quantitative analysis of the device under degradation conditions. In summary, the method of the present application provides technical support for predicting the performance change of the interconnection structure between different PCB sub-boards and main boards and the long-term working performance of electronic devices in system-level design in the communication, big data transmission, automobile industry and medical instrument industries. BRIEF DESCRIPTION OF DRAWINGS

[0011] Other features, objects, and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments thereof, when read in conjunction with the accompanying drawings:

[0012] Figure 1 is a specific flow chart of one embodiment of the present application.

[0013] Figure 2 is a three-dimensional schematic diagram of a PCB asymmetric stack structure designed according to the present application, wherein (a) shows a test fixture structure with connectors, and (b) is a perspective view of the PCB with the fixture removing the dielectric layer.

[0014] Figure 3 is a TDR simulation result schematic diagram of a three-dimensional electromagnetic field model of a high-speed test fixture of an asymmetric stack PCB designed using the method of the present application, which uses microstrip lines as signal transmission lines of the test fixture, and examples 2, 3, and 4 represent edge-coupled differential lines in tight coupling states with line-to-line spacings of one, two, and three times the line width, respectively, and example 1 shows a better three-type impedance matching condition. DETAILED DESCRIPTION

[0015] The present application will be described in detail below with reference to the accompanying drawings and embodiments.

[0016] Figure 1 is a specific flow chart of one embodiment of the present application, which mainly includes the following steps.

[0017] Step 101: According to the actual application scenario of high-frequency high-speed communication electronic devices, the thickness of the PCB high-speed test fixture is determined and the corresponding asymmetric stack is designed. A structure schematic diagram of a multifunctional PCB high-speed test fixture designed using the method of the present application is shown in Figure 2 .

[0018] Step 102: Based on the PCB stack information designed in step 101, the transmission line size parameters that meet the high-frequency impedance matching requirements are calculated based on the transmission line theory. Because differential signals have stronger anti-electromagnetic interference capability, they are less affected by ground bounce and switch noise during interconnection and packaging. Therefore, edge-coupled differential microstrip lines are used as signal paths in this embodiment, and their impedance information and structure parameters are analyzed and extracted.

[0019] Step 103: Based on the calculation results of step 102, a three-dimensional electromagnetic field finite element model of the PCB high-speed test fixture is established, and the TDR impedance curves of the edge-coupled differential lines under different structure designs are obtained as shown in Figure 3 . Subsequently, a comprehensive analysis of the simulation results of the fixture transmitting high-frequency high-speed signals is carried out. Figure 3Under different differential line spacing conditions given in the middle, the three kinds of matching impedance of microstrip line can meet the fluctuation error within ±10%, conform to the industrial standard, and illustrate the good electrical performance of the PCB high-speed test fixture.

[0020] Step 104: According to the relevant data of the three-dimensional model established in step 103, the PCB high-speed test fixture is processed and manufactured, and the mechanical and electrical properties of the finished product are verified. The factory inspection report shows that the warpage of the PCB high-speed test fixture product is 0.28%, which is less than the 0.7% shipment standard; the maximum value of the line single-ended characteristic impedance is 51.94Ω, and the minimum value is 47.15Ω, which meets the error standard requirement of ±10% of the engineering application 50Ω.

[0021] Step 105: For the communication electronics that connect the signal transmission between the components of the complex system in the highly integrated application scenarios such as large servers or supercomputers, considering the interconnection degradation failure problems that may be caused by environmental stresses such as temperature, humidity and vibration, with the help of the PCB high-speed test fixture, the corresponding accelerated degradation test is designed and completed, and then the passive and active experimental test platform is built, and the high-frequency high-speed performance test analysis of the device affected by different environmental stresses is completed.

[0022] It should be noted that the above only describes one embodiment of the present application and does not limit the present application; without departing from the concept of the present application, any modification, equivalent replacement, improvement, etc. made by anyone within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A design method of a multi-functional asymmetric laminated structure high-speed test fixture, characterized in that: The thickness of the PCB high-speed test fixture is determined and the corresponding asymmetric laminated structure is designed according to the size of the high-frequency high-speed communication electronic device and the actual application scenario; The PCB wiring structure of the test fixture is designed according to the specific microwave radio frequency application function of the communication electronic device, and the PCB transmission line structure size parameters that meet the high-frequency impedance matching are calculated based on the generalized transmission line theory, then the three-dimensional electromagnetic field finite element numerical calculation model of the PCB high-speed test fixture is established, and the high-frequency high-speed transmission performance of the fixture is comprehensively simulated and analyzed; The actual processing and manufacturing of the PCB high-speed test fixture are completed based on the three-dimensional structure data and material parameters of the electromagnetic field model, and the mechanical and electrical performance of the finished product passes the engineering inspection standard, realizing the signal transmission function of the PCB high-speed test fixture that can be applied to the high-frequency high-speed parameter experimental test of the device; The degradation mechanism of the communication electronic device suffering from environmental stress in actual application is considered, and the PCB high-speed test fixture is specially designed accordingly, realizing the auxiliary function of the PCB high-speed test fixture that can be applied to the accelerated degradation test of the communication electronic device; According to the different application scenarios of various communication electronic devices, the corresponding accelerated degradation test is completed with the help of the designed PCB high-speed test fixture, then the high-frequency high-speed experimental test platform of the device is built using the test fixture, and the transmission performance and reliability analysis of the electronic device under the influence of different environmental stresses are completed.

2. The design method of a multi-functional asymmetric stacked structure high speed test fixture according to claim 1, wherein, The PCB high-speed test fixture with asymmetric laminated structure has the functions of providing mechanical support, ensuring electrical contact of device signal and return path, assisting in completing the degradation accelerated test research of communication electronic devices, and testing the high-frequency high-speed signal transmission performance.

3. The method of claim 1, wherein the method is characterized by: According to the degradation mechanism of the communication electronic device in the actual application environment, the test fixture is specially designed, and a detachable connector is used as the connection port of the PCB high-speed test fixture and other instruments, so as to focus on the degradation of the device itself, and to realize the quantitative research of the damage influence of environmental stress on the transmission performance of the electronic device in the form of strictly controlled variables.

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