Parallel Sensor Trim Using Helmholtz Coils
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Solution Overview
Problem
Current methods for testing and trimming multiple sensor packages, such as those containing accelerometers and magnetometers, are inefficient and inaccurate due to sequential testing, complex and costly gimbal equipment, and issues with magnetic field generation and stability, leading to increased cycle time and resource intensity.
Innovation Solution
A system that tests both accelerometers and magnetometers in parallel within a testing environment using a pair of Helmholtz coils to generate a continuous magnetic field, allowing for simultaneous exposure to gravitational and magnetic forces, and a series of test locations to rotate the sensor package and gather data for calibration, reducing the need for sequential testing and complex equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sequential testing of accelerometers and magnetometers is performed, then each sensor type can be tested individually, but the total testing cycle time is doubled
Solution Approach 1:
The patent combines accelerometer and magnetometer testing into a single parallel testing operation. The sensor package is positioned once in a test socket that exposes it to both gravitational field (for accelerometer) and magnetic field (for magnetometer) simultaneously, eliminating the need for separate sequential testing operations while maintaining calibration accuracy for both sensor types.
2Measurement precision
If gimbaled devices are used to orient sensor packages, then precise angular positioning is achieved, but the equipment becomes complex and costly to maintain
Solution Approach 1:
Instead of using complex gimbaled devices to actively rotate and position the sensor package, the patent inverts the approach by using simple fixed test sockets at predetermined orientations and rotating the magnetic field generation system. This eliminates the mechanical complexity of gimbals while achieving the same angular positioning functionality through field rotation rather than mechanical rotation.
3Force
If coils are started and stopped repeatedly for magnetometer testing, then magnetic field is generated, but overshoot and oscillation problems occur
Solution Approach 1:
The patent maintains continuous operation of the magnetic field generating coils throughout the testing process. Rather than repeatedly starting and stopping the coils to position sensor packages, the magnetic field remains continuously active and is rotated to different orientations. This eliminates the overshoot and oscillation problems associated with repeated coil activation while maintaining stable magnetic field strength for accurate magnetometer testing.
4Productivity
If un-singulated die are tested, then accelerometer testing can be performed, but package stress configuration does not match real-world conditions
Solution Approach 1:
The patent performs sensor testing after the sensor packages have been singulated (separated from the wafer) and are in their final packaged form. This preliminary action of testing in the actual end-product configuration ensures that the package stress conditions during testing match real-world operating conditions, providing accurate sensor response data that reflects actual product performance rather than test artifact effects.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces the testing cycle time, improves accuracy, and simplifies the testing process by allowing simultaneous calibration of both sensors in a configuration that mimics real-world stress conditions, while maintaining the uniformity of the magnetic field, resulting in more efficient and cost-effective production of singulated sensor packages.
Implementation Method 1
A testing environment is provided in which both accelerometers and magnetometers can be tested in parallel, thereby decreasing the total cycle time for testing a sensor package containing those devices... A series of device test locations within a testing region are configured to provide a known relationship with multiple fields of force
Implementation Method 2
a package incorporating an accelerometer and a magnetometer can be tested and trimmed for response to gravity (for the accelerometer)
Data Source
AI summary
A testing environment is provided in which both accelerometers and magnetometers can be tested in parallel, thereby decreasing the total cycle time for testing a semiconductor device package containing those devices. Embodiments of the present invention can also be configured to test singulated packages, thereby providing a tested and trimmed product that more accurately reflects the package delivered to the customer. In one embodiment, a series of device test locations within a testing region are configured to provide a known relationship with multiple fields of force. The device test locations are configured to provide sensitivity data from the packaged sensors in response to the directional forces. Embodiments provide a mechanism to transport the sensor packages from a device test location to a next device test location.