PCB Short Circuit Location via Signal Reflection
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Solution Overview
Problem
Locating a short circuit between conductive layers in multi-layered printed circuit boards is invasive, laborious, and time-consuming, as existing methods like In-Circuit Test (ICT) can only detect the short circuit's existence but not its location, requiring physical disassembly of components.
Innovation Solution
Injecting test signals at non-collinear test points to determine the distance of signal reflections, allowing for the precise location of the short circuit by analyzing the time required for signal reflections to reach each test point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If In-Circuit Test (ICT) is used to detect short circuits, then the existence of short circuits can be detected, but the location of short circuits cannot be determined
Solution Approach 1:
The PCB is divided into multiple segments by selecting three non-collinear test points. Each test point independently measures the distance to the short circuit, creating segmented measurement zones that together provide complete location information without requiring physical disassembly of components.
Solution Approach 2:
Test signals are introduced as intermediaries to indirectly locate the short circuit. By injecting test signals at known test points and measuring the reflected signal characteristics, the system obtains distance information without direct physical contact or disassembly of the PCB components.
2Measurement precision
If physical depopulation of components is performed to locate short circuits, then the short circuit location can be identified, but the process becomes invasive, laborious, and time-consuming
Solution Approach 1:
The mechanical process of physically removing components is replaced by an electrical measurement system. Test signals are injected through existing test points on the PCB, and the reflected signals provide distance measurements, eliminating the need for manual component depopulation while maintaining precise location identification.
Solution Approach 2:
Test points are pre-established on the PCB during manufacturing, and their locations are recorded. When a short circuit needs to be located, these pre-positioned test points are immediately used for measurement, eliminating the need for preliminary physical exploration or component removal.
3Measurement precision
If physical depopulation of components is performed to locate short circuits, then the short circuit location can be identified, but the process becomes invasive and complex
Solution Approach 1:
The complex physical manipulation process is extracted and replaced by simple electrical measurements. Only the essential measurement function is retained, while all invasive physical operations (component removal, visual inspection, etc.) are eliminated, significantly simplifying the overall process.
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 method efficiently identifies the location of the short circuit with high accuracy, reducing the need for extensive physical examination and significantly speeding up the process, potentially pinpointing the location within a small sub-region of the PCB.
Implementation Method 1
A test signal is injected at each of the three test points, resulting in signal reflections at the short-circuit. The distance between each test point and the short circuit is determined from the time required for each signal reflection to reach the respective test point.
Data Source
AI summary
One embodiment provides a method of locating a short circuit in a printed circuit board. Test signals may be injected at different test points on the circuit board. The distance between each test point and the short circuit may be determined according to how long it takes for a signal reflection at the short circuit to propagate back to each test point. The distances between the various test points and the short circuit can be used to narrow the possible locations of the short circuit or even to pinpoint the location of the short circuit.