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CN-122017527-A - PCB electrical performance test system based on multichannel signal feedback

CN122017527ACN 122017527 ACN122017527 ACN 122017527ACN-122017527-A

Abstract

The invention relates to the technical field of electrical measurement, in particular to a multi-channel signal feedback-based PCB electrical performance test system, which comprises a data acquisition unit and a control unit, wherein the data acquisition unit is used for acquiring impedance deviations of a plurality of differential line pairs on a printed circuit board through multi-channel time domain reflection test. The data screening unit is used for screening effective impedance deviation related to dielectric layer thickness fluctuation from impedance deviation of a plurality of differential line pairs. The model construction unit is used for constructing a lamination alignment error model based on the effective impedance deviation and the space position information of the differential line pair corresponding to the effective impedance deviation on the printed circuit board. The process optimization unit is used for determining process compensation parameters according to the lamination alignment error model and the newly acquired impedance deviation of the printed circuit board, and outputting adjustment guidance for the subsequent printed circuit board design or manufacture according to the process compensation parameters. The invention can accurately identify the PCB impedance change caused by the fluctuation of the thickness of the dielectric layer and provides basis for process optimization.

Inventors

  • LUO CHENGBO

Assignees

  • 惠州市联达金电子有限公司

Dates

Publication Date
20260512
Application Date
20260205

Claims (10)

  1. 1. A PCB board electrical performance test system based on multichannel signal feedback is characterized by comprising: the data acquisition unit is used for acquiring impedance deviations of a plurality of differential line pairs on the printed circuit board through a multi-channel time domain reflection test, wherein the impedance deviations are used for representing the deviation degree of measured impedance of the differential line pairs and preset reference impedance; A data screening unit, configured to screen effective impedance deviation related to thickness fluctuation of the dielectric layer from impedance deviation of the plurality of differential line pairs; the model construction unit is used for constructing a lamination alignment error model based on the effective impedance deviation and the space position information of the differential line pair corresponding to the effective impedance deviation on the printed circuit board, wherein the lamination alignment error model is used for representing the mapping relation between the dielectric layer thickness fluctuation and the impedance deviation; And the process optimization unit is used for determining process compensation parameters according to the lamination alignment error model and the newly acquired impedance deviation of the printed circuit board, and outputting adjustment guidance for the subsequent printed circuit board design or manufacture according to the process compensation parameters.
  2. 2. The PCB electrical performance testing system based on multi-channel signal feedback of claim 1, wherein the data acquisition unit is specifically configured to: For each differential line pair on the printed circuit board, controlling a multi-channel time domain reflectometer to test two signal lines of the differential line pair in a synchronous triggering mode to obtain respective single-ended impedance curves of the two signal lines, wherein the single-ended impedance curves are used for representing impedance change characteristics of a single signal line at different transmission line positions; Determining a differential impedance curve of the differential line pair according to the single-ended impedance curves of the two signal lines of the differential line pair; and determining the impedance deviation of the differential line pair according to the difference between the differential impedance curve of the differential line pair and the preset reference impedance.
  3. 3. The PCB electrical performance testing system based on multi-channel signal feedback of claim 1, wherein the data screening unit is specifically configured to: for each differential line pair, determining a single-ended impedance symmetry index according to single-ended impedance curves of two signal lines of the differential line pair; determining an impedance smoothness index according to the change data of the impedance of the differential line pair along with the position of the transmission line; And determining the impedance deviation of the differential line pair as the effective impedance deviation under the condition that the single-ended impedance symmetry index is larger than a first preset threshold value and the impedance smoothness index is larger than a second preset threshold value.
  4. 4. The system for testing the electrical performance of the PCB based on the multi-channel signal feedback of claim 3, wherein the determining the single-ended impedance symmetry index comprises determining an impedance difference sequence according to the impedance values of the two signal lines of the differential line pair at each sampling point, and performing exponential decay mapping processing based on the impedance difference sequence to generate a first quantized value as the single-ended impedance symmetry index; Determining an impedance smoothness index, which comprises determining a first-order differential sequence according to impedance changes of adjacent sampling points on a single-end impedance curve of one signal line in the differential line pair, and performing exponential decay mapping processing based on standard deviation of the first-order differential sequence to generate a second quantized value as the impedance smoothness index.
  5. 5. The multi-channel signal feedback based PCB board electrical performance testing system of claim 1, wherein the model building unit comprises a spatial interpolation module for: determining deviation influence weights of the printed circuit board in the first axial direction and the second axial direction according to all effective impedance deviations, wherein the deviation influence weights are used for representing the overall strength of dielectric layer thickness fluctuation on impedance influence in different axial directions; Aiming at the position to be interpolated on the printed circuit board, except for the position corresponding to the effective impedance deviation, where a differential line pair is not arranged but the impedance deviation is required to be obtained, determining an adjusted distance between the position to be interpolated and each position corresponding to the effective impedance deviation according to the deviation influence weight, wherein the adjusted distance is a spatial distance weighted by combining axial deviation strength; and determining an impedance deviation estimated value of the position to be interpolated by adopting an inverse distance weighted interpolation algorithm according to the adjusted distance so as to generate impedance deviation space distribution data covering the region to be measured of the printed circuit board.
  6. 6. The multi-channel signal feedback based PCB electrical performance testing system of claim 5, wherein determining the bias impact weight comprises: for each effective impedance deviation, according to the direction of the connecting line of the start point and the end point of the differential line pair corresponding to the effective impedance deviation on the plane of the printed circuit board, decomposing the value of the effective impedance deviation into a projection component in the first axial direction and a projection component in the second axial direction; Determining a deviation influence weight corresponding to the first axial direction according to projection components of all effective impedance deviations in the first axial direction; And determining the deviation influence weight corresponding to the second axis according to the projection components of all effective impedance deviations in the second axis.
  7. 7. The multi-channel signal feedback based PCB electrical performance testing system of claim 5, wherein the model building unit further comprises a model fitting module for: converting the impedance deviation space distribution data into dielectric layer thickness fluctuation distribution data according to a preset conversion coefficient, wherein the preset conversion coefficient is used for representing dielectric layer thickness variation corresponding to unit impedance deviation; Fitting the dielectric layer thickness fluctuation distribution data by adopting a quadric function; And determining the coefficient of the quadric function through a least square method to obtain the lamination alignment error model, wherein the least square method is used for minimizing the residual square sum between the theoretical predicted value of the quadric function and the dielectric layer thickness fluctuation distribution data.
  8. 8. The multi-channel signal feedback based PCB electrical performance testing system of claim 1, wherein the process optimization unit comprises: the error back-pushing module is used for inputting the impedance deviation of the newly acquired printed circuit board into the lamination alignment error model and determining the dielectric layer thickness fluctuation distribution of the newly acquired printed circuit board; The compensation determining module is used for determining the process compensation parameters according to the statistical characteristics of the dielectric layer thickness fluctuation distribution and a preset process capacity boundary, and the preset process capacity boundary is used for defining the limit range of dielectric layer thickness fluctuation which can be controlled by the current production process.
  9. 9. The multi-channel signal feedback based PCB electrical performance testing system of claim 8, wherein the process optimization unit further comprises a design adjustment module for: And determining an adjustment amount for the subsequent printed circuit board design according to the process compensation parameters, wherein the adjustment amount comprises a compensation value of at least one of a wiring width, a wiring interval or a preset thickness of a dielectric layer.
  10. 10. The multi-channel signal feedback based PCB electrical performance testing system of claim 8, wherein the process optimization unit further comprises a closed loop control unit for: continuously collecting impedance deviation and corresponding process parameters of each batch of printed circuit boards, updating and maintaining a process parameter database, and monitoring the stability of the lamination process by a statistical process control method; and periodically updating the lamination alignment error model based on the new batch data accumulated in the process parameter database.

Description

PCB electrical performance test system based on multichannel signal feedback Technical Field The invention relates to the technical field of electrical measurement, in particular to a PCB electrical performance test system based on multichannel signal feedback. Background A printed circuit board (Printed Circuit Board, PCB) is the core base component of an electronic device that enables electrical interconnection, the electrical performance of which directly affects signal transmission quality and system reliability. In a high-speed digital circuit, a differential signal transmission mode is widely applied due to the advantages of strong anti-interference capability and the like, and the impedance matching of a differential pair is a key parameter for guaranteeing the signal integrity, and is usually required to be evaluated by a time domain reflection test method and the like. In the prior art, a multi-channel test device is often used to measure impedance of a differential line pair on a PCB board, and the matching degree is evaluated by comparing the deviation between the actually measured impedance and the designed target impedance. However, the process links such as lamination in the PCB board manufacturing process may introduce systematic errors such as dielectric layer thickness fluctuation, and such physical layer changes may be directly and complexly reflected on the electrical impedance characteristics. The existing test evaluation method is difficult to effectively distinguish and quantify the impedance change caused by specific process deviation, so that the test result lacks sufficient accuracy and pertinence when guiding the subsequent process optimization, and the further improvement of the PCB impedance control level and the product yield is restricted. Disclosure of Invention In order to solve the technical problems of inaccurate evaluation of impedance matching of a PCB and lack of accurate basis of process optimization caused by thickness fluctuation of a dielectric layer, the invention aims to provide a PCB electrical performance test system based on multichannel signal feedback, and the adopted technical scheme is as follows: In a first aspect, a system for testing electrical performance of a PCB board based on multichannel signal feedback is provided, including a data obtaining unit, configured to obtain impedance deviations of a plurality of differential line pairs on the PCB board through multichannel time domain reflection test, where the impedance deviations are used to characterize deviation degrees of measured impedance of the differential line pairs and preset reference impedance. And the data screening unit is used for screening effective impedance deviation related to the fluctuation of the thickness of the dielectric layer from the impedance deviation of the plurality of differential line pairs. The model construction unit is used for constructing a lamination alignment error model based on the effective impedance deviation and the space position information of the differential line pair corresponding to the effective impedance deviation on the printed circuit board, wherein the lamination alignment error model is used for representing the mapping relation between the dielectric layer thickness fluctuation and the impedance deviation. And the process optimization unit is used for determining process compensation parameters according to the lamination alignment error model and the newly acquired impedance deviation of the printed circuit board and outputting adjustment guidance for the subsequent printed circuit board design or manufacture according to the process compensation parameters. In one possible design, the data acquisition unit is specifically configured to control the multichannel time domain reflectometer to test two signal lines of the differential line pair in a synchronous trigger mode for each differential line pair on the printed circuit board, obtain respective single-ended impedance curves of the two signal lines, wherein the single-ended impedance curves are used for representing impedance change characteristics of the single signal line at different transmission line positions, determine differential impedance curves of the differential line pair according to the single-ended impedance curves of the two signal lines of the differential line pair, and determine impedance deviation of the differential line pair according to differences between the differential impedance curves of the differential line pair and preset reference impedance. In one possible design, the data screening unit is specifically configured to determine, for each differential pair, a single-ended impedance symmetry index according to a single-ended impedance curve of two signal lines of the differential pair, determine, according to data of a change of an impedance of the differential pair along with a transmission line position, an impedance smoothness index, and determine, as an effect