Dual-Stage Vacuum Fixture Prevents Probe Interference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional circuit board testers using dual-stage test fixtures often fail to fully support the circuit board during non-powered tests, leading to inadequate contact force, poor signal quality, and potential electrical damage due to unbalanced probe pressure and vacuum-induced stress fractures.
Innovation Solution
A dual-stage fixture with a slide plate that moves between positions to prevent short-stroke probes from contacting the circuit board, ensuring only long-stroke probes make contact during non-powered tests, while applying a vacuum to maintain even pressure and prevent interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dual-stage test fixture with spring-loaded probes is used, then testing versatility is improved, but device complexity increases
Solution Approach 1:
The probe field is segmented into two distinct stages: long-stroke probes that contact the circuit board first, and short-stroke probes that contact only when additional vacuum force is applied. This segmentation allows different probe sets to be used for different test types (powered vs. unpowered tests), providing versatility while maintaining a relatively simple overall structure.
Solution Approach 2:
The fixture transitions from a static structure to a dynamic system where the upper stripper plate can move between positions. The spring-loaded probes provide dynamic response to varying vacuum forces, allowing the system to adapt its configuration based on test requirements without complex mechanical actuators.
2Force
If vacuum pressure is applied to drive platen with spring-loaded probes, then contact force is improved, but harmful factors increase due to vacuum-induced stress fractures
Solution Approach 1:
The long-stroke probes make initial contact with the circuit board before the vacuum force is fully applied. This preliminary action establishes a stable mechanical connection that prevents the circuit board from being subjected to unbalanced vacuum pressures, thereby avoiding stress fractures while still achieving adequate contact force when needed.
Solution Approach 2:
The spring-loaded probes act as cushioning elements that absorb and distribute the vacuum pressure forces. The springs provide compliance that prevents excessive localized stress on the circuit board, protecting it from vacuum-induced damage while maintaining sufficient contact force for reliable electrical connection.
3Adaptability or versatility
If short-stroke probes contact circuit board during unpowered test, then testing capability is improved, but measurement precision deteriorates due to transient signal interference
Solution Approach 1:
The short-stroke probes are effectively extracted or removed from the testing process during unpowered tests by positioning the upper stripper plate such that only long-stroke probes contact the circuit board. This eliminates the source of transient signal interference for unpowered tests, while the short-stroke probes remain available for powered tests where they provide additional testing capability.
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 configuration enhances electrical contact quality, reduces the risk of structural damage, and improves test reliability by maintaining consistent pressure and preventing transient signals from interfering with testing.
Implementation Method 1
Some circuit board testers use a vacuum fixture that uses atmospheric pressure, specifically a vacuum, to drive a platen with a combination of spring-loaded probes and circuit board push down features to press against the circuit board
Data Source
AI summary
A dual-stage fixture for a circuit tester includes a slide plate that can be slid between at least a first position and a second position. In the first position, an upper stripper plate is spring-loaded, and a full set of test probes, including both long-stroke and short-stroke probes, can contact the circuit board or UUT (unit under test). In the second position, the upper stripper plate becomes fixed in position, and only the long-stroke probes can contact the circuit board. The fixed positioning of the upper stripper plate prevents the short-stroke probes from contacting the circuit board even when there is unbalanced loading of probe pressure between the top and bottom of the circuit board, thereby preventing transient signals from interfering with testing. In addition, a vacuum is applied in this position during a non-powered test.