Probe Head Inductance Reduction via Ground Pin Impedance Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The inductance of test probes can affect the frequency of test signals provided to and sensed from electronic devices under test, leading to inefficiencies in testing, particularly at high frequencies.
Innovation Solution
The use of multipath probes with electrically conductive signal and secondary paths, where the secondary path is electrically insulated from the signal path by a gap of less than 50 microns, and the incorporation of ground pins connecting conductive guide plates to improve impedance matching without mechanical contact with the device under test or the test apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional test probe structure is used, then the probe can provide test signals to the device under test, but the loop inductance of the probe is excessive which limits the testing frequency
Solution Approach 1:
The probe structure is segmented into multiple functional components: signal path, secondary path, ground pins, and insulating materials. This segmentation allows each component to be optimized independently for its specific function while collectively reducing loop inductance and enabling high-frequency testing
Solution Approach 2:
An electrically insulating material is introduced as an intermediary between the signal path and secondary path. This intermediary maintains electrical insulation while allowing the paths to be positioned close together, reducing loop area and inductance without causing electrical interference
2Speed
If the gap between signal path and secondary path is reduced to decrease loop inductance, then testing frequency can be increased, but electrical insulation between the paths may be compromised
Solution Approach 1:
The gap dimension is precisely controlled within a specific range (less than 50 microns) to optimize the balance between reducing loop inductance and maintaining electrical insulation. This parameter optimization enables high-frequency operation while preventing electrical breakdown
3Reliability
If ground pins are added to improve impedance matching, then signal integrity at high frequencies is improved, but the probe structure becomes more complex
Solution Approach 1:
The ground pins serve multiple functions simultaneously: they provide impedance matching for signal probes, establish reference potentials, and reduce loop inductance. This multi-functionality justifies the additional structural elements by delivering multiple benefits from a single design feature
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 reduces loop inductance, enabling more effective impedance matching and allowing for higher frequency testing by minimizing excess probe inductance, thereby enhancing the performance of test probes in high-frequency applications.
Implementation Method 1
An electrically insulating material can be disposed between the signal path and the secondary path
Implementation Method 2
ground pins connecting the guide plates to improve impedance matching between the probes and the test apparatus or the device under test
Data Source
AI summary
Improved impedance matching is provided in vertical probe arrays having conductive guide plates by providing ground pins connecting the guide plates that do not mechanically touch the device under test or the input test apparatus. Such ground pins can be disposed in predetermined patterns around corresponding signal probes to improve an impedance match between the probes and the test apparatus and/or the device under test. Preferably all impedances are matched to 50Ω as is customary for high frequency work.