Radial Chip Resistor Array for CDM Current Sensor Impedance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CDM testers face challenges in providing consistent measurement results due to the inconsistent electrical characteristics of FR4 laminate materials at higher frequencies, leading to inaccurate waveform peak values and the need for calibration techniques, which affects the accuracy of electrostatic discharge (ESD) simulations for semiconductor devices.
Innovation Solution
A current sensor using a radial array of 10-ohm microwave chip resistors mounted between the inner and outer conductors of a signal output transmission line, eliminating the need for FR4-type circuit boards and ensuring uniform frequency response and impedance, thereby minimizing reflections up to 3 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If FR4 laminate material is used to mount chip resistors in conventional current sensors, then mechanical support and structural stability are provided, but electrical characteristics become inconsistent at higher frequencies due to dielectric loss and water content variations
Solution Approach 1:
The patent removes the FR4 laminate material from the current sensor assembly entirely. The chip resistors are mounted directly to the sensor housing without an intermediate circuit board, eliminating the source of high-frequency electrical instability while maintaining mechanical support through direct mounting structures.
Solution Approach 2:
The patent transitions from using FR4 composite material (glass-reinforced epoxy) to using metal housing structures with direct mounting capabilities. This replaces the hygroscopic, frequency-sensitive composite material with conductive, stable metal structures that provide both mechanical support and electrical connectivity.
2Ease of manufacture
If conventional FR4 circuit board material is used, then ease of manufacture and structural support are achieved, but high frequency losses increase impedance and decrease measurement accuracy
Solution Approach 1:
The FR4 circuit board is completely removed from the design. The patent mounts chip resistors directly to the sensor housing or uses alternative support structures that do not involve high-frequency signal paths through lossy dielectric materials, thereby eliminating the impedance variation problem while maintaining manufacturing simplicity.
3Measurement precision
If tuning cavities are added to compensate for FR4 material variations, then waveform peak values can be calibrated to meet legacy values, but device complexity increases and calibration procedures become excessive
Solution Approach 1:
The patent eliminates the need for tuning cavities and calibration procedures by removing the FR4 material that causes the variations in the first place. The direct-mount design provides inherently stable electrical characteristics that do not require additional compensating structures or calibration steps.
Solution Approach 2:
The redesigned sensor provides inherently stable measurements without requiring external calibration or adjustment mechanisms. The elimination of FR4 material creates a self-calibrating system where the electrical characteristics remain consistent across different environmental conditions and manufacturing batches.
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 provides consistent and accurate measurement results without the need for calibration, maintaining uniform impedance and frequency response, enhancing the reliability of ESD simulations for semiconductor devices.
Implementation Method 1
A current sensor having microwave chip resistors in parallel radial arrangement
Implementation Method 2
a radial array of resistors mounted directly between the inner and outer conductors of a signal output transmission line
Data Source
AI summary
A current sensor for use with a charged device model (CDM) tester includes an outer conductor and a cylindrical inner conductor. The inner conductor is positioned within a central cylindrical bore of the outer conductor to provide a characteristic transmission line impedance of approximately 50 ohms. A test probe conductor extends from the distal end of the inner conductor and is electrically connected to the inner conductor. An array of self-supporting ceramic chip resistors is radially positioned between the distal ends of the inner conductor and the outer conductor to provide a uniformly distributed resistance between the inner conductor and the outer conductor. When the test probe conductor is applied to a pin of a charged device under test (DUT), a discharge current passes through the resistors and produces a voltage on the inner conductor that is provided as a signal voltage proportional to the discharge current.