PCB Creep Corrosion Sensor With Concentric Electrodes
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Solution Overview
Problem
Conventional PCB corrosion sensors fail to accurately predict creep corrosion distance and time-to-failure in harsh environments, leading to potential short circuits and open circuits.
Innovation Solution
A creep corrosion sensor utilizing a central pad electrode and an outer ring electrode on a PCB to measure insulation resistance, exploiting galvanic corrosion principles between Cu and Ag, with a range of electrode gaps to log resistance changes over time, enabling a linear extrapolation model for failure prediction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional corrosion sensing methodologies (QCM, meander traces, electrochemical impedance) are used, then corrosion detection capability is provided, but the ability to accurately reproduce creep corrosion distance and predict time-to-failure is insufficient
Solution Approach 1:
The patent creates a simplified copy of the actual PCB structure by fabricating test coupons with identical ImAg copper surface finish and electrode geometries (central pad and outer ring electrode configurations) that replicate field PCB conditions. This copying approach allows accurate reproduction of creep corrosion behavior in laboratory settings, enabling precise measurement of corrosion distance and reliable time-to-failure prediction without requiring complex field testing
Solution Approach 2:
The patent systematically varies critical parameters including electrode gap distances (25, 50, 100, 250, 500, 1000 microns), electrode configurations (central pad radius, outer ring dimensions), and environmental conditions (temperature, humidity, sulfur concentration) to establish comprehensive data sets. These parameter changes enable the development of predictive models that accurately correlate resistance changes with creep corrosion distance and time-to-failure under different operating conditions
2Ease of manufacture
If ImAg surface finish is used on PCB to support lead-free solder, then solderability is improved, but susceptibility to creep corrosion in harsh environments increases
Solution Approach 1:
The patent converts the harmful effect of ImAg's creep corrosion susceptibility into a beneficial sensing mechanism. By deliberately exposing the ImAg surface and monitoring its galvanic corrosion behavior between copper and silver layers, the system transforms what was previously a reliability problem into a useful diagnostic tool that provides early warning of corrosion progression and predicts time-to-failure
Solution Approach 2:
The ImAg surface finish naturally performs dual functions: it provides the required solderability for manufacturing while simultaneously serving as the sensing element for corrosion detection. The galvanic corrosion that occurs between the copper substrate and silver coating in harsh environments generates measurable resistance changes, eliminating the need for separate protective layers or additional sensing components
3Measurement precision
If electrode gap distance is reduced to increase sensitivity, then measurement sensitivity is improved, but the complexity of manufacturing and maintaining precise gap dimensions increases
Solution Approach 1:
The patent transitions from measuring corrosion in one dimension (linear distance between two points) to using a two-dimensional electrode configuration (central pad surrounded by outer ring). This dimensional change increases the effective sensing area and sensitivity while providing more robust manufacturing tolerances, as the concentric geometry naturally maintains uniform gap distribution across the electrode surface
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
Provides accurate creep corrosion distance measurement and time-to-failure estimation, enhancing the reliability of telecommunications products in corrosive environments by offering early warnings and life predictions.
Implementation Method 1
The creep corrosion sensor of the present disclosure exploits, but is not limited to, the galvanic corrosion principles between Cu and Ag
Implementation Method 2
resistance monitoring means electrically coupled to the central pad electrode and the outer ring electrode and adapted to measure a resistance of the creep corrosion area
Data Source
AI summary
A creep corrosion sensor and sensing method including and utilizing: a central pad electrode disposed on a first surface of a printed circuit board (PCB or PCBA); an outer ring electrode disposed concentrically around the central pad electrode on the first surface of the PCB; where the central pad electrode and the outer ring electrode define a creep corrosion area therebetween on the first surface of the PCB; and resistance monitoring means electrically coupled to the central pad electrode and the outer ring electrode and adapted to measure a resistance of the creep corrosion area as affected by creep corrosion present in the creep corrosion area. In an embodiment, a plurality of creep corrosion sensors having varying creep corrosion area gap widths are utilized in a creep corrosion sensor coupon assembly on the PCB to determine an estimated time-to-failure of a component or product utilizing the PCBA.