A high-precision automated test system

Abstract

This invention relates to the field of electronic device testing technology, specifically to a high-precision automated testing system for triaxial magnetic sensor chips applied to FPCs. This system requires no adapters, has strong anti-interference capabilities, a high degree of automation, and comprehensive testing coverage. It includes the following modules: a pneumatic pressing structure and safety protection light curtain for automated and safe contact with the FPC under test; a magnetic shield made of high-permeability material to isolate external magnetic fields from interference; a test coil, built into the center of the shield to generate a uniform magnetic field in a vertical direction; a communication and data acquisition module electrically connected to the corresponding test point on the FPC via probes at the bottom of the fixture; and a control and display module for displaying the testing process and results, as well as an interface for connecting to a host computer for log storage.

Description

Technical Field

[0001] This invention relates to the field of electronic device testing technology, specifically to a high-precision automated testing system for triaxial magnetic sensor chips applied to FPCs. Background Technology

[0002] With the widespread adoption of consumer electronics such as smart wearable devices, AR / VR devices, and smartphones, the demand for more integrated, smaller, and flexible FPC components has increased dramatically. Among these, the triaxial magnetic sensor embedded in the FPC is a key component for providing orientation sensing and attitude detection. In existing production processes, functional testing of such FPC modules faces the following challenges:

[0003] 1. Environmental interference: Electromagnetic fields in a typical factory environment can severely interfere with the reading of weak signals from magnetic sensors, leading to unstable test data and a high misjudgment rate.

[0004] 2. Testing accuracy and standards: There is a lack of field methods for efficiently verifying key parameters such as chip sensitivity, linearity, and triaxial orthogonality in a controlled and standard magnetic field environment.

[0005] 3. Automation and efficiency: Traditional testing methods rely on multiple devices for switching, resulting in a fragmented testing process that cannot meet the production line's requirements for high cycle times (UPH).

[0006] 4. Test coverage: Simple continuity tests cannot cover the chip's functionality and the electrical performance of all associated devices on the FPC.

[0007] Therefore, existing testing solutions struggle to balance testing accuracy with production efficiency and ease of on-site deployment. Summary of the Invention

[0008] This invention proposes a high-precision automated testing system that requires no adapters, has strong anti-interference capabilities, a high degree of automation, and comprehensive testing coverage.

[0009] The technical solution of the present invention is as follows:

[0010] A high-precision automated testing system includes the following modules:

[0011] Pneumatic pressing structure and safety protection light curtain are used for automated and safe contact with the FPC under test;

[0012] A magnetic shield made of high permeability material is used to isolate the test from interference by external environmental magnetic fields;

[0013] The test coil is built into the center of the shield to generate a uniform magnetic field in the vertical direction;

[0014] The communication and data acquisition module is electrically connected to the corresponding test point on the FPC via probes at the bottom of the fixture;

[0015] The control and display module is used to display the test process and results, and the interface for connecting to the host computer is used to save logs.

[0016] The above system performs the following test steps:

[0017] S100: The device is placed and electrically connected to the test platform;

[0018] S200: Perform basic electrical tests;

[0019] S300: Perform chip ID verification;

[0020] S400: Performs initial magnetic field self-calibration and environmental data reading;

[0021] S500: Perform performance tests under standard magnetic fields;

[0022] S600: Result determination and recording.

[0023] Furthermore, step S100 includes:

[0024] S110: The operator or automatic feeding mechanism places the FPC module to be tested on the precise positioning fixture of the test platform, ensuring that the chip side faces upward.

[0025] S120: The positioning structure ensures that the chip body is located within 15mm of the upper surface of the coil and within the 5mm×5mm uniform magnetic field area at the very center of the coil.

[0026] S130: Triggers the pneumatic pressing structure to smoothly press down the pressure head, pressing the FPC firmly onto the test plane and keeping the chip plane parallel to the coil plane.

[0027] S140: The probe at the bottom of the fixture establishes reliable electrical contact with the test point on the FPC.

[0028] S150: After the safety light curtain is detected as correct, the system confirms that the pressing is in place and proceeds to the next step.

[0029] Furthermore, step S200 includes:

[0030] S210: The controller performs an open / short circuit test: measuring whether there is a short circuit or open circuit between each test point.

[0031] S220: Perform parameter measurements on key passive components on the FPC and compare them with preset ranges.

[0032] S230: PN junction characteristic measurement of semiconductor devices.

[0033] S240: If any of the above exceeds the threshold, it is immediately judged as a failure, the test is terminated and an alarm is issued, prompting the operator to raise the fixture to remove the defective product; if all pass, continue to the next step.

[0034] Furthermore, step S300 includes:

[0035] S310: The controller sends a command to the magnetic sensor chip to read the ID via the I²C bus;

[0036] S320: Read the device ID returned by the chip;

[0037] S330: Compare the read ID with the standard value in the specification sheet;

[0038] S340: If they match, the chip model is determined to be correct, and the test continues; if they do not match, the test fails and is terminated.

[0039] Furthermore, step S400 includes:

[0040] S410: The controller configures the chip register via I²C to exit standby mode and enter normal measurement or self-test mode;

[0041] S420: Confirm that the test coil is de-energized, i.e., no external excitation magnetic field is applied;

[0042] S430: Reads the raw values ​​of the magnetic field output of the chip's three axes;

[0043] S440: The read triaxial data is used as the initial environmental reference value for subsequent difference calculation to eliminate static environmental magnetic field offset;

[0044] S450: Determines whether the initial value is within a reasonable range. If abnormal, it will issue an alarm indicating that there may be a problem with the shielding environment or the chip.

[0045] Furthermore, step S500 includes:

[0046] S510: The controller sends a start signal to the coil drive circuit, applying a preset DC current to generate a stable Z-axis standard magnetic field above the coil. ;

[0047] S520: Waiting for the magnetic field to stabilize;

[0048] S530: Read the chip's triaxial magnetic field output data again via I²C;

[0049] S540: Calculate the difference: , , ;

[0050] S550: According to Calculate the Z-axis sensitivity and linearity of the chip: With respect to the theoretically applied magnetic field strength The allowable deviation range is set based on chip specifications and production line process capabilities for comparison.

[0051] S560: Evaluate triaxial orthogonality and mounting angle, and calculate the lateral component amplitude: and compare it with a preset threshold. In comparison, if If the angle of deviation is deemed acceptable, then it is deemed unacceptable; otherwise, it is deemed unacceptable.

[0052] S570: After the test is completed, cut off the coil current to avoid prolonged heating.

[0053] Furthermore, step S600 includes:

[0054] S610: Perform a comprehensive logical operation on all test data from steps S200, S300, and S500 and their respective preset pass thresholds;

[0055] S620: If all items are within the threshold range, the final result is "pass"; otherwise, it is "fail".

[0056] S630: During the test, the color touch screen displays the current test item, measurement value, judgment conclusion and overall progress in real time;

[0057] S640: After the test is completed, the system automatically generates a test record, which includes the product serial number, test time, raw data, intermediate calculation results and final judgment;

[0058] S650: This record is uploaded to the host computer as a file via the communication interface and saved according to date / batch for quality traceability and statistical analysis;

[0059] If the result is NG, the touchscreen can display the specific failure item, making it easier for operators or process engineers to quickly locate the cause of the failure.

[0060] Furthermore, the preset threshold in step S560 Determined based on the following mathematical model:

[0061] In the presence of pitch angle and roll angle Under the condition that the amplitude of the horizontal component satisfies ;

[0062] Assume the maximum allowable composite tilt angle is The threshold is then set to ,in The determination is made jointly by FPC surface mount technology capabilities and product application requirements;

[0063] If it is determined to be unsuccessful, further processing is performed using the formula. and The roll and pitch angles are estimated separately for failure analysis.

[0064] Furthermore, the Z-axis standard magnetic field in step S510 It is based on the Biot-Savart law.

[0065] Furthermore, the 5mm × 5mm uniform magnetic field height region in step S120 is determined in the following way:

[0066] Finite element electromagnetic field simulation was performed based on the geometric parameters of the coil, and point-by-point mapping was conducted using a high-precision gaussmeter after the actual device was built to ensure that the uniformity deviation of the Z-axis magnetic field strength in this region was controlled within ±0.5%.

[0067] The working principle and beneficial effects of this invention are as follows:

[0068] This invention efficiently and accurately determines whether the magnetic induction performance of a chip is qualified by applying a standard and controllable uniaxial (Z-axis) magnetic field to the chip under test in a magnetically shielded environment and automatically reading, analyzing, and comparing the chip's triaxial magnetic field data. Technical principle: The FPC under test (triaxial magnetic sensor chip face up) is precisely placed on a positioning platform above the test coil, ensuring that the chip plane is strictly parallel to the coil plane, and that the chip body is within 15mm above the coil and within a uniform magnetic field height area of ​​approximately 5x5mm at the very center of the coil. After the test coil is energized, a stable and spatially uniform standard magnetic field is generated along its axial direction (Z-axis).

[0069] In this system:

[0070] Ideal calibration state: If both chip manufacturing and FPC mounting are perfect, when applying... When the magnetic field is applied along the Z-axis, the chip theoretically only detects the change in magnetic field along the Z-axis (consistent with the Hall effect and the principle of magnetic field superposition). , The component read on the axis should be zero.

[0071] Actual performance and attitude diagnosis: In actual measurements, the chip's three coordinate axes are collected and analyzed ( , , Output magnetic field data:

[0072] observe Axis components can be used to calculate the chip's sensitivity and linearity.

[0073] like , If the axis produces a non-zero component, the magnitude of this component is directly related to the non-parallelism (tilt angle) of the chip / coil and the triaxial sensitivity matching error or orthogonality error inside the chip. The deviation angle can be deduced by calculation.

[0074] By comparing the readings of "Power-on Self-Test (reading zero magnetic field reference value)" and "Magnetic Field Test" in a shielded environment, static environment magnetic field offset can be eliminated, and the dynamic response performance of the chip can be accurately evaluated.

[0075] The main innovation lies in addressing the needs of "specific objects (FPC modules)" and "specific scenarios (automated screening on production lines)." By simplifying hardware (single-axis coil + magnetic shielding), simplifying algorithms (threshold judgment), and integrating testing processes (electrical + magnetic testing), the originally complex and expensive calibration technology is transformed into a highly efficient, stable, and practical production testing solution. This systematic simplification and functional integration to solve specific engineering problems constitutes a significant technological advancement that distinguishes it from existing technologies. Attached Figure Description

[0076] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0077] Figure 1 This is a schematic diagram of the flattened state of an FPC unit;

[0078] Figure 2 This is a schematic diagram of the system module structure of the present invention;

[0079] Figure 3 This is a schematic diagram illustrating the testing principle of the present invention, which allows a unidirectional magnetic field to be applied via a coil.

[0080] Figure 4 This is a schematic diagram of the principle of reading the three-axis magnetic field data of the chip according to the present invention:

[0081] Figure 5 This is a schematic diagram of the test module structure of the present invention;

[0082] Figure 6 This is a schematic diagram of the FPC bending state;

[0083] Figure 7 The amplitude of the horizontal component ( ) and cross axis error ( Comparison chart for differences.

[0084] In the diagram: 1. Safety light curtain; 2. First press button; 3. Rise button; 4. Touch screen; 5. Second press button; 6. Emergency stop button; 7. Grounding foot; 8. Lower shielding cover; 9. Coil; 10. Upper mold pressing block; 11. Upper support plate; 12. Upper shielding cover; 13. Product carrier plate; 14. Protective baffle; 15. Coil pad; 16. Test needle mold. Detailed Implementation

[0085] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0086] Example 1

[0087] like Figure 1-6 As shown in this embodiment, a high-precision automated testing system is used for automated testing of the triaxial magnetic sensor chip (such as an electronic compass chip) integrated on a flexible printed circuit (FPC) after assembly, to verify its function and performance. It is particularly suitable for mass production. For example, it can perform rapid, high-precision, and interference-resistant factory testing on FPC modules with geomagnetic sensor chips such as AK09919C mounted on them.

[0088] Includes the following modules:

[0089] Pneumatic pressing structure and safety protection light curtain are used for automated and safe contact with the FPC under test;

[0090] A magnetic shield made of high permeability material is used to isolate the test from interference by external environmental magnetic fields;

[0091] Test coil 9 is embedded in the center of the shield to generate a vertical direction ( A uniform magnetic field (axis);

[0092] The communication and data acquisition module is electrically connected to the corresponding test point on the FPC via probes at the bottom of the fixture;

[0093] The control and display module is used to display the test process and results, and the interface for connecting to the host computer is used to save logs.

[0094] Due to the flexibility, deformability, and poor rigidity of FPCs, they are prone to bending or localized unevenness during operation and testing. Therefore, the precise positioning platform and pneumatic pressing structure in this embodiment are crucial. The test fixture requires the chip body (U36500) to be strictly located within a uniform magnetic field area, a requirement achieved through physical positioning fixtures. The pressing structure ensures that the FPC maintains the required flatness at the test position, parallel to the plane of coil 9. Even if the FPCB itself has some bending, as long as the key component (sensor chip) is precisely positioned and adhered to the test plane, effectiveness can be guaranteed.

[0095] Furthermore, the presence of numerous components on the board introduces potential interference. FPCs often integrate passive and active components such as capacitors and connectors. The core measures in this embodiment are "step-by-step testing" and "isolation and shielding." The process begins with open-circuit and short-circuit tests and component parameter tests (e.g., testing the capacitance value of C36500 and verifying the connectivity of J36520). This not only eliminates problems with the components themselves but also promptly identifies local interference sources that cannot be shielded and may be caused by short-circuit high currents or other anomalies during operation. Subsequently, when a magnetic field is applied, the entire test platform is placed within an active magnetic shield made of SUS430 high-permeability material. This effectively isolates electromagnetic noise from the factory environment and also shields against weak magnetic field noise that may be generated by other components on the board, providing a clean environment for chip testing.

[0096] Furthermore, due to the high requirements for overall reliability, this embodiment designs an integrated, pass / fail test process. Within a single process, it completes comprehensive testing covering everything from circuit connectivity and component functionality to the parameters and magnetic properties of the core IC (such as the AK09919C). This design can identify all types of defects (electrical issues, ID issues, magnetic performance issues) in one go, greatly improving test coverage and overall product quality, making it particularly suitable for highly integrated components like FPCs.

[0097] Example 2

[0098] Based on the system module in Example 1, the testing method and specific steps are as follows:

[0099] S100: The device is placed and electrically connected to the test platform. The relevant parameter calibration and threshold settings are as follows:

[0100] The 5mm × 5mm high uniform magnetic field region was determined in the following way:

[0101] Finite element electromagnetic field simulation was performed based on the geometric parameters of coil 9, and point-by-point mapping was conducted using a high-precision gaussmeter after the actual device was built to ensure that the electromagnetic field within this area was accurately measured. The uniformity deviation of the axial magnetic field strength is controlled within ±0.5%, and the specific setting is based on the following:

[0102] Simulation: Based on the specific parameters of the rectangular coil 9 given in the "Test Scheme Description" (inner diameter 200mm × 200mm, height 8mm, 500 turns, current 400mA), the electromagnetic field at different positions above the coil 9 can be calculated using finite element electromagnetic field simulation software (such as Ansys Maxwell, COMSOL, etc.). Axial magnetic field intensity distribution diagram.

[0103] Experimental calibration: After the actual device is built, a high-precision single-axis gaussmeter is used to move and measure point by point on the set working surface (15mm above the upper surface of coil 9) to draw a spatial distribution map of the magnetic field strength.

[0104] Parameter settings: Based on simulation and measured data, determine a certain area above the vertical line of the axial center (e.g., Within a range of ±2.5mm, the uniformity deviation of the magnetic field strength (e.g., the difference between the maximum and minimum values ​​divided by the average) is controlled within a very small percentage (e.g., ±0.5% or ±1%). This area is called the "highly uniform magnetic field zone". Setting this zone to 5x5mm provides a reliable placement tolerance for the FPC (and the U36500 chip on it), ensuring that regardless of where the chip is located on the FPC, as long as the FPC is positioned within this window, the excitation magnetic field strength is stable and consistent, thus guaranteeing the repeatability of the test data.

[0105] Basis for setting the pass / fail (NG) threshold: This is an engineering parameter that takes into account chip specifications, application requirements and process capabilities. It is recommended to provide a clear setting logic.

[0106] Based on the chip datasheet: Refer to the specifications mentioned in the attached AK09919C chip datasheet, such as the typical sensitivity value of 0.15 μT / LSB, the measurement range of ±4900 μT, and the acceptable range of output data in self-test mode. These are the fundamental criteria for determining whether the chip meets the original performance requirements.

[0107] Considering the tolerance requirements of the application scenario: For example, if this FPC module is used in consumer electronics (such as an electronic compass), its azimuth accuracy requirement can be converted into the maximum allowable deviation range of the chip's Z-axis sensitivity, and , The maximum permissible crosstalk of the shaft (i.e., caused by tilt angle). Axial magnetic field in , The projection size of the axis), thereby setting an absolute value threshold.

[0108] Process capability (Cpk) data: Based on the "IC Angle Measurement" table in the appendix or other production statistics, the maximum permissible tilt angle range of the chip caused by FPC placement and test positioning under good process conditions can be determined. This process tolerance is converted into a magnetic field testing standard, as described above. .

[0109] Statistical analysis sets thresholds: After system calibration, automated testing is performed on a batch of FPC modules known to be of good quality, collecting a large amount of data. The data. Calculate the mean and variance of this good product data (e.g., ...). The final test threshold (threshold) can be set to the "mean". The form can be either "≤ Theoretical Maximum Projection + Deviation Margin". This provides a quantitative and reliable basis for determining "Pass / Fail".

[0110] The chip coordinate system in the text ( The definition is as follows:

[0111] ‌ Axis: Perpendicular to the chip plane (i.e., the FPC plane) and pointing upwards. When the chip is correctly positioned, this axis is theoretically parallel to the direction (vertical direction) of the standard magnetic field generated by the test coil (9).

[0112] ‌ shaft and Axes: Located within the chip plane and orthogonal to each other. Although the document does not explicitly specify their exact orientation on the chip (e.g., based on chip package markings), based on the context, they represent the two lateral sensing axes of the magnetic sensor inside the chip.

[0113] Ideally, when the chip plane is strictly parallel to the coil plane, the applied... Axial standard magnetic field It should only be on the chip The axis generates a response. Specifically, step S100 includes:

[0114] S110: The operator or automatic feeding mechanism places the FPC module to be tested on the precise positioning fixture of the test platform, ensuring that the chip side faces upward.

[0115] S120: The positioning structure ensures that the chip body is located within 15mm of the upper surface of coil 9 and within the 5mm×5mm magnetic field uniform area at the center of coil 9, so as to accommodate the FPC mounting position tolerance.

[0116] S130: Triggers the pneumatic pressing structure, causing the pressure head to press down smoothly, pressing the FPC onto the test plane and keeping the chip plane parallel to the coil 9 plane.

[0117] For safety reasons, this embodiment includes two pressing buttons: a first pressing button 2 and a second pressing button 5. During the pressing test, both buttons must be pressed simultaneously with both hands to prevent arm injury. To complete the upward movement, simply press the upward button 3 with one hand.

[0118] S140: The probes (such as 6 organ pins) at the bottom of the fixture establish reliable electrical contact with the test points on the FPC (including chip power supply, I²C communication, component measurement points, etc.).

[0119] S150: After the safety light curtain 1 is detected as correct, the system confirms that the pressing is in place and proceeds to the next step.

[0120] S200: Perform basic electrical tests;

[0121] Specifically, step S200 includes:

[0122] S210: The controller performs an open / short circuit test: measuring whether there is a short circuit or open circuit between each test point.

[0123] S220: Performs parameter measurements (capacitance value, equivalent series resistance, etc.) on key passive components (such as capacitor C36500) on the FPC and compares them with preset ranges.

[0124] S230: PN junction characteristics measurement for semiconductor components (such as the protection diode of connector J36520).

[0125] S240: If any of the above exceeds the threshold, it is immediately judged as a failure, the test is terminated and an alarm is issued, prompting the operator to raise the fixture to remove the defective product; if all pass, continue to the next step.

[0126] S300: Perform chip ID verification;

[0127] Specifically, step S300 includes:

[0128] S310: The controller sends a command to read the ID to the magnetic sensor chip (such as AK09919C) via the I²C bus;

[0129] S320: Read the device ID returned by the chip (such as a fixed value like 0x0C19);

[0130] S330: Compare the read ID with the standard value in the specification sheet;

[0131] S340: If they match, the chip model is determined to be correct, and the test continues; if they do not match, the test fails and is terminated.

[0132] S400: Performs initial magnetic field self-calibration and environmental data reading;

[0133] Specifically, step S400 includes:

[0134] S410: The controller configures the chip register via I²C to exit standby mode and enter normal measurement or self-test mode;

[0135] S420: Confirm that test coil 9 is de-energized, i.e. no external excitation magnetic field is applied;

[0136] S430: Read chip three-axis The original value of the magnetic field output (usually a 16-bit ADC code value).

[0137] S440: Use the read triaxial data as the initial environmental reference value (denoted as...). , , This is used for subsequent difference calculations to eliminate static environmental magnetic field offsets (such as geomagnetic background, residual magnetism inside the shield, etc.).

[0138] S450: Determines whether the initial value is within a reasonable range (e.g., whether it exceeds the chip's zero-drift specification). If abnormal, it will issue an alarm indicating that there may be a problem with the shielded environment or the chip.

[0139] S500: Perform performance tests under standard magnetic fields;

[0140] The magnetic field strength of the rectangular coil 9 above its geometric central axis It can be approximated or calculated precisely using a finite element model. Its strength is proportional to the structural dimensions of coil 9 (inner diameter L×W, total number of turns N) and the excitation current I (400mA).

[0141] Specifically, step S500 includes:

[0142] S510: The controller sends a start signal to the coil 9 drive circuit, applying a preset DC current (e.g., 400mA) to generate a stable current above coil 9. Axial standard magnetic field ;

[0143] S520: Wait for the magnetic field to stabilize (delay from several milliseconds to tens of milliseconds, depending on the inductance time constant of coil 9).

[0144] S530: Read the chip's triaxial magnetic field output data again via I²C (denoted as...). , , );

[0145] Figure 3 This is used to illustrate that something can be applied through coil 9. A unidirectional magnetic field is applied, and the chip is placed in a region with uniform magnetic field, with the chip plane parallel to the plane of coil 9.

[0146] Figure 4 In the middle, the upper part is the chip, and the lower part is the chip placement platform coil 9. The left side illustrates that if the chip / / (parallel) chip FPC / / (parallel) coil 9, then the chip only has The shaft has components. , The axial component is 0; the right side illustrates what happens if the chip has a tilt angle. , The axis will have a component; the larger the chip tilt angle, , The larger the components of the two axes.

[0147] S540: Calculate the difference. The general, basic form of expression is:

[0148] , , ;

[0149] in, For chips The change in magnetic field sensed by the Z-axis is used to evaluate the chip's Z-axis sensitivity and linearity. As a derivative of a specific scenario, the calculation formula is expressed as follows:

[0150] ‌ in It is the chip after applying a magnetic field Axis reading values, These are the initial environment values.

[0151] ‌ , For chips shaft and The amount of change in the magnetic field induced by the shaft.

[0152] The calculation formulas are as follows:

[0153] ;

[0154] .

[0155] Under ideal parallel conditions, , It should be zero, in the formula , , These represent the maximum, average, or measured value. Their non-zero values ​​reflect chip mounting offset or triaxial orthogonality error.

[0156] S550: According to computing chip Axis sensitivity and linearity: With respect to the theoretically applied magnetic field strength (The standard magnetic field strength generated by coil 9 within a 5mm x 5mm area at a height of 15mm above the center of coil 9 is obtained by pre-calibrating the current, number of turns, and uniform area position of coil 9.) is compared, and the allowable deviation range is set according to the chip specifications and production line process capabilities.

[0157] S560: Evaluate triaxial orthogonality and mounting angle, and calculate the lateral component amplitude: and compare it with a preset threshold. In comparison, if If the angle of deviation is deemed acceptable, then it is deemed unacceptable; otherwise, it is deemed unacceptable.

[0158] Axial standard magnetic field It is based on the Biot-Savart law.

[0159] And through analysis , The non-zero components generated by the axis can be used to determine the non-parallelism. Specifically, the simplified physical model is as follows:

[0160] In the specific design, this value is theoretically calculated using the Biot-Savart law, and determined jointly by finite element electromagnetic field simulation (such as Ansys Maxwell, COMSOL) and point-by-point measurement and calibration using an actual high-precision gaussmeter. This ensures that the preset magnetic field strength target value is achieved in the predetermined working area, and meets extremely high magnetic field uniformity requirements (such as ±0.5%).

[0161] The signal-to-noise ratio of the target magnetic field strength should be high enough to produce an output signal that is significantly higher than the noise of the sensor itself, so as to facilitate accurate interpretation.

[0162] The sensor's measurement range is within ±4900μT of the measured chip AK09919C and within the linear operating range with suitable sensitivity, ensuring that the measured magnetic field response (ΔB) is proportional to the applied magnetic field, which facilitates the assessment of sensitivity performance.

[0163] Furthermore, considering the specific parameters of coil 9 as required above, the goal is to generate a stable and uniform Z-axis standard magnetic field with a typical value (e.g., 50μT, 100μT, etc.) at the target location (chip mounting surface). The strength, stability, and uniformity of this magnetic field are fundamental to achieving a "controllable standard excitation source," ensuring that all devices under test receive the same quality test excitation. This fundamentally ensures the uniformity of the test standard, which is a prerequisite for this method to provide stable and reliable judgment on the production line.

[0164] The above-mentioned preset threshold Determined based on the following mathematical model:

[0165] In the presence of pitch angle and roll angle Under the condition that the amplitude of the horizontal component satisfies ;

[0166] Assume the maximum allowable composite tilt angle is The threshold is then set to ,in The determination is made jointly by FPC surface mount technology capabilities and product application requirements;

[0167] If it is determined to be unsuccessful, further processing is performed using the formula. and The roll and pitch angles are estimated separately for failure analysis.

[0168] S570: After the test is completed, cut off the current to coil 9 to avoid prolonged heating.

[0169] S600: Result determination and recording.

[0170] Specifically, step S600 includes:

[0171] S610: Compile all test data (open / short circuit results, component parameter values, ID comparison results) from steps S200, S300, and S500. , , The horizontal component amplitude, etc., are subjected to comprehensive logical operations with their respective preset qualified thresholds;

[0172] Horizontal component amplitude ( Defined as This value is used for comprehensive evaluation. and The residual response of the shaft.

[0173] Acceptance criteria: The document specifies the threshold conditions (judgment logic) for determining whether the deflection angle is acceptable. .in This refers to the "maximum combined tilt angle allowed by the process," determined jointly by the FPC surface mount technology (SMT) capabilities and product application requirements. If the value is less than or equal to the threshold, it is considered qualified; otherwise, it is considered unqualified (NG).

[0174] Referring to the figure, it is necessary to explain here the horizontal component amplitude mentioned above ( Its physical essence is the application of standards. When the axial magnetic field is present, , The amplitude of the residual magnetic field response appearing on the axis; the calculation source is from Axial difference magnetic field , Axial difference magnetic field The vector sum is obtained through calculation; its core purpose is to evaluate whether the chip mounting angle and triaxial orthogonality error are up to standard; the unit is consistent with the magnetic field strength (e.g., Gauss, mT).

[0175] and (Typically meaning cross-axis error / lateral error) In magnetic sensor / chip testing scenarios, it usually represents cross-axis error or lateral sensitivity error; its physical essence is the sensor's error on the sensitive axis (e.g., ... When a magnetic field is applied to the axis, , The unexpected response ratio or deviation generated by the axis; the core application is to quantify the cross-axis suppression capability of the sensor and evaluate the non-ideal characteristics of the device itself (such as material anisotropy, process deviation); the judgment logic is usually based on the percentage error threshold (such as Exy≤1%), and the unit is percentage (%) or dimensionless coefficient.

[0176] S620: If all items are within the threshold range, the final result is "Pass"; otherwise, it is "Not Pass".

[0177] S630: During the test, the color touch screen displays the current test item, measurement value, judgment conclusion and overall progress in real time;

[0178] S640: After the test is completed, the system will automatically generate a test record, which includes the product serial number (if any), test time, raw data, intermediate calculation results and final judgment;

[0179] S650: This record is uploaded to the host computer via the communication interface in .log format and saved by date / batch for quality traceability and statistical analysis;

[0180] If the result is NG, the touch screen can indicate the specific failure item (such as "open / short circuit failure", "Z-axis sensitivity out of tolerance" or "X-axis lateral component out of limit"), which makes it easier for operators or process engineers to quickly locate the cause of the failure.

[0181] Since most existing technologies focus on solving a complete magnetic sensor error model (including all 12 parameters such as triaxial sensitivity, zero bias, orthogonality error, and mounting angle error), this method uses a triaxial Helmholtz coil to generate magnetic fields in three directions and employs complex algorithms such as Newton's iteration method for solving the model. The aim is to obtain the most accurate calibration coefficients for compensation in the final application. This is a laboratory or R&D phase approach that prioritizes "ultimate accuracy."

[0182] This embodiment is specifically designed for production lines producing FPC components (material designation U36500, etc.). The core requirements are high throughput (UPH 300-400 pieces / hour), interference resistance (using SUS430 magnetic shielding), and high-reliability pass / fail (Go / No-Go) screening. Therefore, the following approach was adopted:

[0183] Single axis ( (Axis) Magnetic field: It greatly simplifies the magnetic field generating device (single planar coil 9), reduces hardware complexity and testing time, and avoids complex multi-axis magnetic field switching;

[0184] Simplified Algorithm: The core judgment logic is to compare with a preset simple threshold, which does not involve solving complex nonlinear equations. It has a fast calculation speed and is suitable for real-time implementation in embedded controllers (microcontrollers) to meet the requirements of fast production line cycle time.

[0185] Integrated testing process: It integrates basic electrical testing, chip ID verification, and magnetic performance testing into one; this means that before testing magnetic field performance, circuit connection faults (open or short circuits), key component faults (such as capacitor C36500, connector J36520), and chip model mismatch issues have been eliminated, greatly improving overall testing efficiency and product yield control accuracy, which is a function that pure magnetic sensor calibration systems do not have.

[0186] Addressing the unique challenges of FPCs: Overcoming the challenges of FPC's flexible deformation through a high-precision positioning platform and highly reliable contacts (6 probes) is a concrete manifestation of production line testing engineering practices, rather than operations in an ideal laboratory environment.

[0187] The key comparisons are as follows:

[0188]

[0189] Therefore, the above-described embodiments have the following significant advantages compared with the prior art:

[0190] 1. Accuracy and Anti-interference: An active magnetic shielding environment is constructed using high-permeability materials such as SUS430, effectively eliminating environmental magnetic field interference and ensuring the accuracy and repeatability of test results. Combined with precise mechanical positioning and a uniform magnetic field zone design, the data results are highly reliable.

[0191] 2. High Efficiency and Automation: The test fixture adopts the FCT (Functional Testing) mode, integrating all testing steps from basic electrical properties (open and short circuits, resistance and capacitance, PN junctions) to the core magnetic sensor chip functions (ID recognition, triaxial magnetic field performance), eliminating the need for an ICT tester. The test cycle time (UPH) can reach 300-400 pieces / hour, greatly improving production efficiency.

[0192] 3. Comprehensive test coverage: The test plan not only covers the core IC, but also achieves 100% electrical test coverage for all key electrical components on the FPC (such as the 6 components in the appendix), ensuring the overall reliability of the module.

[0193] 4. Strong data traceability: It automatically generates and saves log files containing detailed data from all testing phases, providing reliable data support for production process traceability, quality analysis, and process optimization.

[0194] 5. Intelligent Diagnosis: This method can not only determine "good / bad", but also detect "error modes" in the three-axis magnetic field components. , Axial component anomalies provide specific failure analysis directions for production and R&D (such as mounting angle problems, chip performance parameter drift, etc.).

[0195] The above-described operating methods can be arbitrarily adjusted according to the design, provided that the hardware module supports them; this embodiment will not elaborate further. The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-precision automated testing system, characterized in that, Includes the following modules: Pneumatic pressing structure and safety protection light curtain are used for automated and safe contact with the FPC under test; A magnetic shield made of high permeability material is used to isolate the test from interference by external environmental magnetic fields; The test coil (9) is built into the center of the shield to generate a uniform magnetic field in the vertical direction; The communication and data acquisition module is electrically connected to the corresponding test point on the FPC via probes at the bottom of the fixture; The control and display module is used to display the test process and results, and the interface for connecting to the host computer is used to save logs; The above system performs the following test steps: S100: The device is placed and electrically connected to the test platform; S200: Perform basic electrical tests; S300: Perform chip ID verification; S400: Performs initial magnetic field self-calibration and environmental data reading; S500: Perform performance tests under standard magnetic fields; S600: Result determination and recording.

2. The high-precision automated testing system according to claim 1, characterized in that, Step S100 includes: S110: The operator or automatic feeding mechanism places the FPC module to be tested on the precise positioning fixture of the test platform, ensuring that the chip side faces upward; S120: The positioning structure ensures that the chip body is located within 15mm of the upper surface of the coil (9) and within the 5mm×5mm magnetic field uniform area at the center of the coil (9); S130: Trigger the pneumatic pressing structure to press the pressure head down smoothly, press the FPC tightly onto the test plane, and keep the chip plane parallel to the coil (9) plane; S140: The probe at the bottom of the fixture establishes reliable electrical contact with the test point on the FPC; S150: After the safety light curtain (1) is detected as correct, the system confirms that the pressing is in place and proceeds to the next step.

3. The high-precision automated testing system according to claim 2, characterized in that, Step S200 includes: S210: The controller performs an open / short circuit test: measuring whether there is a short circuit or open circuit between each test point; S220: Perform parameter measurements on key passive components on the FPC and compare them with preset ranges; S230: Measurement of PN junction characteristics of semiconductor devices; S240: If any of the above exceeds the threshold, it is immediately judged as a failure, the test is terminated and an alarm is issued, prompting the operator to raise the fixture to remove the defective product; if all pass, continue to the next step.

4. The high-precision automated testing system according to claim 3, characterized in that, Step S300 includes: S310: The controller sends a command to the magnetic sensor chip to read the ID via the I²C bus; S320: Read the device ID returned by the chip; S330: Compare the read ID with the standard value in the specification sheet; S340: If they match, the chip model is determined to be correct, and the test continues; if they do not match, the test fails and is terminated.

5. The high-precision automated testing system according to claim 4, characterized in that, Step S400 includes: S410: The controller configures the chip register via I²C to exit standby mode and enter normal measurement or self-test mode; S420: Confirm that the test coil (9) is de-energized, i.e. no external excitation magnetic field is applied; S430: Reads the raw values ​​of the magnetic field output of the chip's three axes; S440: The read triaxial data is used as the initial environmental reference value for subsequent difference calculation to eliminate static environmental magnetic field offset; S450: Determines whether the initial value is within a reasonable range. If abnormal, it will issue an alarm indicating that there may be a problem with the shielding environment or the chip.

6. The high-precision automated testing system according to claim 5, characterized in that, Step S500 includes: S510: The controller sends a start signal to the coil (9) drive circuit, applies a preset DC current, and generates a stable current above the coil (9). Axial standard magnetic field ; S520: Waiting for the magnetic field to stabilize; S530: Read the chip's triaxial magnetic field output data again via I²C; S540: Calculate the difference: , , ; S550: According to computing chip Axis sensitivity and linearity: With respect to the theoretically applied magnetic field strength The allowable deviation range is set based on chip specifications and production line process capabilities for comparison. S560: Evaluate triaxial orthogonality and mounting angle, and calculate the lateral component amplitude: and compare it with a preset threshold. In comparison, if If the angle of deviation is deemed acceptable, then it is deemed unacceptable; otherwise, it is deemed unacceptable. S570: After the test is completed, cut off the current to the coil (9) to avoid prolonged heating.

7. A high-precision automated testing system according to claim 6, characterized in that, Step S600 includes: S610: Perform a comprehensive logical operation on all test data from steps S200, S300, and S500 and their respective preset pass thresholds; S620: If all items are within the threshold range, the final result is "pass"; otherwise, it is "fail". S630: During the test, the color touch screen displays the current test item, measurement value, judgment conclusion and overall progress in real time; S640: After the test is completed, the system automatically generates a test record, which includes the product serial number, test time, raw data, intermediate calculation results and final judgment; S650: This record is uploaded to the host computer as a file via the communication interface and saved according to date / batch for quality traceability and statistical analysis; If the result is NG, the touchscreen can display the specific failure item, making it easier for operators or process engineers to quickly locate the cause of the failure.

8. A high-precision automated testing system according to claim 6, characterized in that, The preset threshold in step S560 Determined based on the following mathematical model: In the presence of pitch angle and roll angle Under the condition that the amplitude of the horizontal component satisfies ; Assume the maximum allowable composite tilt angle is The threshold is then set to ,in The determination is made jointly by FPC surface mount technology capabilities and product application requirements; If it is determined to be unsuccessful, further processing is performed using the formula. and The roll and pitch angles are estimated separately for failure analysis.

9. A high-precision automated testing system according to claim 8, characterized in that, Z-axis standard magnetic field in step S510 It is based on the Biot-Savart law.

10. A high-precision automated testing system according to claim 9, characterized in that, The 5mm × 5mm uniform magnetic field height region in step S120 is determined by the following method: Finite element electromagnetic field simulation is performed based on the geometric parameters of coil (9), and point-by-point mapping is performed using a high-precision gaussmeter after the actual device is built, so as to ensure that the uniformity deviation of the Z-axis magnetic field strength in this area is controlled within ±0.5%.

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