PCB Test Fixture Clamping for Vibration Stress Distribution
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Solution Overview
Problem
Existing reliability testing methodologies for semiconductor devices on printed circuit board assemblies (PCBAs) fail to adequately assess the physical robustness of Pb-free semiconductor products under extreme temperature and physical stress conditions, such as vibration and mechanical shock, due to reduced solder joint strength and lack of updated evaluation methods.
Innovation Solution
The development of fixtures that securely hold test PCBAs during vibration and mechanical shock testing, with features like top and bottom plates having apertures for full periphery contact and fastening, allowing for temperature cycling and emulating real application conditions, ensuring consistent stress distribution across semiconductor devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If Pb-free solder is used to reduce hazardous substance exposure, then environmental safety is improved, but solder joint strength and ability to withstand extreme temperature and physical stress deteriorates
Solution Approach 1:
The patent changes the physical and chemical parameters of the testing process itself rather than the solder material. By modifying test conditions (temperature ranges, vibration profiles, shock magnitudes) and fixture design (clamping force, support positioning), the testing methodology adapts to evaluate Pb-free solder performance despite its inherently lower strength, enabling reliable assessment without changing the solder composition
Solution Approach 2:
The patent replaces conventional 4-point support mechanical systems with a multi-point clamping fixture system that distributes mechanical stress more evenly across the PCB. This substitution of the mechanical support structure compensates for the reduced solder joint strength by reducing stress concentration and providing more uniform load distribution during vibration and shock testing
2Device complexity
If conventional 4-point support fixtures are used for vibration testing, then testing simplicity is maintained, but reliability of stress application and accuracy of reliability data deteriorates
Solution Approach 1:
The fixture is segmented into multiple independent support points (more than the conventional 4 points) that can be independently positioned and adjusted. This segmentation allows each support point to be optimally positioned to match the PCB's structural characteristics and the expected stress patterns, providing more accurate and reliable stress application while maintaining reasonable fixture complexity through modular design
Solution Approach 2:
The fixture design incorporates universal features that allow it to accommodate different PCB sizes, shapes, and configurations while maintaining reliable stress application. The adjustable support points and clamping mechanisms can be configured for various test scenarios, making the fixture multi-functional and reducing the need for multiple specialized fixtures for different PCB types
3Reliability
If temperature cycling is added to vibration/shock testing, then comprehensive reliability assessment is improved, but testing complexity and time requirements worsen
Solution Approach 1:
The patent merges the temperature cycling function with the vibration and shock testing by integrating thermal chambers or heating/cooling elements directly into the fixture or test system. This combination allows simultaneous application of thermal and mechanical stresses, providing comprehensive reliability assessment in a single integrated test system rather than requiring separate sequential tests, thereby reducing overall testing time and system complexity
Data Source
AI summary
A fixture for securing at least one test printed circuit board assembly (PCBA) including a PCB having semiconductor devices mounted thereon during vibration or mechanical shock testing. A top plate includes top features including a continuous top outer ring, at least one inner top aperture within the top outer ring, and a plurality of outer top apertures positioned beyond the top outer ring including a top probe access aperture and a threaded aperture. A bottom plate includes bottom features including a bottom continuous outer ring, at least one inner bottom aperture, and plurality of outer bottom apertures including a bottom probe access aperture and table mounting aperture. The threaded apertures accept a fastener that clamps the top plate to the bottom plate for the outer rings to secure a full periphery of the PCB between the top plate and bottom plate.