Measuring device for printed circuit boards

Abstract

This invention discloses a measurement device for printed circuit boards (PCBs). The measurement device includes a test probe module, a signal application and acquisition module, a storage module, an index calculation module, and a thickness output module. The test probe module can contact two conductive elements at a selected interval on the PCB under test. The substrate between the two conductive elements on the PCB under test is defined as the measurement object. The signal application and acquisition module applies a test signal to the two conductive elements to obtain a capacitance value. The storage module stores a standard numerical data established by the capacitance value corresponding to one of a plurality of ideal PCBs. The index calculation module receives the capacitance value and performs calculations on the normalized capacitance value and the standard numerical data to establish a relative capacitance index. The thickness output module outputs a thickness signal based on the relative capacitance index.

Claims

1. A measuring device for printed circuit boards, suitable for measuring a printed circuit board under test, the measuring device comprising: A test probe module includes two probes, each capable of contacting two conductive elements at a selected interval on a printed circuit board under test (PCB). The PCB between the two conductive elements is defined as a measurement object. A signal application and acquisition module, electrically connected to the test probe module, applies a test signal to the two conductive elements to obtain a capacitance value. A storage module stores standard numerical data established from the capacitance values ​​corresponding to one of a plurality of ideal PCBs. An index calculation module, electrically connected to the signal application and acquisition module and the storage module, receives the capacitance value and performs calculations on the normalized capacitance value and the standard numerical data to establish a relative capacitance index. A thickness output module, electrically connected to the index calculation module, outputs a thickness signal based on the relative capacitance index.

2. The measuring device for the printed circuit board according to claim 1, wherein, The standard numerical data is a set of standard capacitance values ​​obtained by capacitance measurement of multiple ideal printed circuit boards. The index calculation module further includes a statistics and judgment unit. The statistics and judgment unit can calculate an average value and a standard deviation of the set of standard capacitance values, and define a normal fluctuation range of the standard numerical data based on the average value plus or minus three standard deviations. When the capacitance value is outside the normal fluctuation range, the statistics and judgment unit outputs an abnormality judgment signal.

3. The measuring device for the printed circuit board according to claim 1, wherein, The test probe module can establish multiple matrix regions on the surface of the printed circuit board under test; the index calculation module further includes a feature ratio calculation unit and a thickness difference analysis unit; the signal application and acquisition module obtains a first capacitance value and a second capacitance value in a first region of the multiple matrix regions, and obtains a third capacitance value and a fourth capacitance value in a second region of the multiple matrix regions; the feature ratio calculation unit calculates a first local feature ratio based on the ratio of the first capacitance value to the second capacitance value, and calculates a second local feature ratio based on the ratio of the third capacitance value to the fourth capacitance value; the thickness difference analysis unit receives and divides the first local feature ratio and the second local feature ratio to obtain a thickness difference ratio; the thickness output module outputs a relative thickness distribution profile between the first region and the second region based on the thickness difference ratio.

4. The measuring device for the printed circuit board according to claim 1, wherein, The index calculation module further includes a calibration unit. The calibration unit can identify a specific region with minimal to zero difference in differential capacitance measurement from multiple matrix regions divided on the surface of the printed circuit board under test, and write the specific region as a global zero-state calibration reference for the printed circuit board under test. The calibration unit uses the global zero-state calibration reference to cancel parasitic capacitance interference in the capacitance value.

5. The measuring device for the printed circuit board according to claim 1, wherein, The two conductive elements are two alignment targets on the printed circuit board under test, and the areas of the two alignment targets are different from each other.

6. The measuring apparatus for the printed circuit board according to claim 1, wherein, The two conductive elements are two external conductive sheets, and the two external conductive sheets are respectively disposed on opposite sides of the printed circuit board under test.

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