Capacitive Probe Geometry for Low Profile Component Testing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitive testing of miniature sockets and connectors is challenging due to the lack of conductive structure for signal coupling, leading to difficulties in distinguishing properly connected pins from open pins, resulting in high error rates.
Innovation Solution
A probe with a narrow conductive sensing member, often less than 2 mm wide, is positioned adjacent to the component to preferentially couple test signals from conductors, reducing unwanted noise and improving the signal-to-noise ratio, allowing for reliable capacitive opens testing of low-profile components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional probe with large sensing member is used for capacitive testing, then the probe can detect signals from multiple conductors simultaneously, but the signal-to-noise ratio deteriorates due to increased noise coupling from unwanted conductors
Solution Approach 1:
The probe sensing member is segmented into multiple smaller sensing elements, each positioned to couple with specific conductors. This segmentation allows the probe to test multiple pins simultaneously while maintaining high signal-to-noise ratio for each individual pin by isolating the capacitive coupling paths.
Solution Approach 2:
Each sensing element of the probe is designed with specific local characteristics to couple preferentially with its target conductor. The sensing members have optimized geometries and positions that create localized capacitive fields, enabling selective signal pickup from individual conductors while rejecting noise from other conductors.
2Measurement precision
If the probe sensing member is made narrow to reduce noise coupling, then the signal-to-noise ratio improves, but the probe becomes less effective at detecting signals from conductors with limited conductive structure
Solution Approach 1:
The probe employs multiple sensing members arranged in three-dimensional space around the conductors being tested. This spatial arrangement creates multiple capacitive coupling paths from different dimensions, ensuring reliable signal detection even when the conductive structure of the component under test is limited or minimally invasive.
3Ease of operation
If capacitive testing is applied to miniature sockets and connectors with limited conductive structure, then non-invasive testing is achieved, but the test signal coupling is insufficient leading to high error rates
Solution Approach 1:
The probe acts as an intermediary that enhances the weak capacitive coupling between the test signal and the limited conductive structure of miniature components. By using multiple sensing members with optimized geometries, the probe amplifies the signal coupling effect, enabling accurate testing of components with minimal conductive structures without requiring invasive modifications.
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
The solution enhances the accuracy of capacitive testing by reducing noise interference and improving the differentiation between properly connected and open pins, leading to more reliable manufacturing processes.
Implementation Method 1
the test signal can capacitively couple to the probe plate
Implementation Method 2
sensing the signal capacitively coupled to the sensing member from the conductor
Data Source
AI summary
A probe assembly for capacitive testing electrical connections of a low profile component to a circuit assembly. The probe assembly is configured to reduce coupling of noise signals from the circuit assembly to the capacitive probe. The probe assembly includes a sensing member with a geometry that allows the probe to preferentially couple to test signals from the pins of a component under test rather than conductive structures on the circuit assembly, such as pads, and signal traces to which those pins are attached. The sensing member may be a vertical capacitive sense plate such that coupling is to an edge of the plate. The sensing member alternatively may be a horizontal capacitive sense plate with an active area of the probe surrounded by an isolation ring. Measurements made with such capacitive probes may provide test measurements that yield a reliable discrimination between a properly attached pin and an open pin.