Probe Device Impedance Matching for PCB Signal Inspection
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Solution Overview
Problem
Existing electrical inspection methods for printed wiring boards face challenges in efficiently and accurately measuring high-speed signal transmission characteristics, such as characteristic impedance and crosstalk, due to impedance mismatch and the need for expensive, custom-made probe cards, especially when dealing with narrow pitch wiring and high-frequency signals.
Innovation Solution
A probe device with multiple probe groups of wire probes arranged in parallel, where each probe group matches the characteristic impedance of the wiring board, allowing simultaneous contact with multiple wires, and a measuring apparatus that uses these probes to apply and detect measurement signals, ensuring efficient and accurate electrical inspection without the need for custom probe cards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a coaxial probe with signal pin and ground pin is used for electrical inspection, then the basic electrical characteristics can be measured, but the probe cannot be used for narrow pitch wiring and requires moving the probe for each signal wire, reducing inspection efficiency
Solution Approach 1:
The probe device divides the measurement function into multiple independent probe pins (first probe pin for signal, second probe pin for ground) that can simultaneously contact multiple terminals. This segmentation allows parallel measurement of multiple signal wires without moving the probe, thereby improving inspection efficiency while maintaining measurement precision.
Solution Approach 2:
The invention transitions from a single coaxial probe contacting one signal wire at a time to a multi-pin probe structure that can simultaneously contact multiple signal wires across the narrow pitch wiring board. This dimensional expansion from point-contact to multi-point contact enables efficient inspection of narrow pitch wiring without sacrificing measurement accuracy.
2Productivity
If a probe pin is used for high-frequency signal inspection, then the inspection can be conducted, but impedance mismatch causes signal reflection and reduces measurement accuracy
Solution Approach 1:
The probe device changes the electrical parameters by setting the characteristic impedance of the probe pins to match the impedance of the signal wires (e.g., both 50Ω). This impedance matching eliminates signal reflection at the contact interface, enabling accurate high-frequency signal measurement while maintaining inspection capability.
3Measurement precision
If a custom probe card is made to match the terminal arrangement of the printed wiring board, then accurate electrical inspection can be conducted, but the production cost becomes very high
Solution Approach 1:
The probe device creates a universal measurement tool with multiple probe pins that can simultaneously contact various terminal arrangements on different printed wiring boards. This multi-functional design eliminates the need for custom-made probe cards for each specific board type, significantly reducing production costs while maintaining accurate electrical inspection capability.
Solution Approach 2:
Instead of creating expensive custom probe cards that exactly replicate the terminal arrangement of each printed wiring board, the invention uses a standardized multi-pin probe structure that can adapt to different terminal configurations. This copying approach uses a single versatile probe design to replace multiple custom probe cards, reducing manufacturing costs while preserving measurement precision.
4Adaptability or versatility
If the clearance between signal pin and ground pin of coaxial probe is reduced to fit narrow pitch wiring, then the probe can be used for narrow pitch boards, but the probe structure becomes difficult to manufacture and maintain
Solution Approach 1:
The probe device segments the measurement function across multiple independent probe pins with standard spacing, rather than using a single coaxial probe with reduced clearance. This segmentation allows the use of standard manufacturing processes for each pin while maintaining compatibility with narrow pitch wiring through the multi-pin configuration, thereby easing manufacturing and maintenance.
Data Source
AI summary
Provided is a probe device used for electrical inspection of a printed wiring board, the probe device including at least one probe group including a plurality of wire probes configured to be able to simultaneously abut against a wire provided on the printed wiring board and extending in a specified direction, the plurality of wire probes abutting against the wire along the direction and being electrically connected to each other.