Vibration-Resistant Solder Joint Failure Prediction Device
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Solution Overview
Problem
Existing failure prediction technologies for solder joint portions on circuit boards are inadequate in predicting failures caused by vibration stress, as they either require specific installation locations or do not account for vibration stress effectively.
Innovation Solution
A failure prediction device with a load amplifying portion and a sacrificial fracture portion is designed to amplify vibration stress and predict failures by ensuring the sacrificial fracture portion has a shorter lifetime than the solder joint portions, allowing for high design flexibility and effective prediction under both vibration and thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dummy joint portion is disposed at the outer peripheral edge of a package where stress is concentrated, then vibration stress can be detected, but the installation location is limited
Solution Approach 1:
The patent introduces a load amplifying portion as an intermediary structure that includes a sacrificial fracture portion. This mediator amplifies the vibration stress and transmits it to the sacrificial fracture portion, enabling detection without requiring direct placement at the outer peripheral edge. The load amplifying portion acts as a bridge between the vibration source and the detection point, providing both vibration detection capability and installation flexibility.
Solution Approach 2:
The sacrificial fracture portion is designed as a disposable element with intentionally reduced strength compared to the solder joint portions. It is meant to fracture first under vibration stress, serving as a sacrificial indicator that protects the actual solder joints. This allows the use of a weaker, simpler structure for detection purposes without compromising the reliability of the main connection.
2Reliability
If a wire with low strength structure is provided at corner regions where stress is concentrated, then failure prediction can be achieved, but the installation location is limited to outer peripheral edges
Solution Approach 1:
The load amplifying portion serves as an intermediary that concentrates and amplifies vibration stress to the sacrificial fracture portion. This mediator structure allows the failure prediction function to be decoupled from the outer peripheral edge location, as the load amplifying portion can be positioned anywhere on the circuit board and will still effectively transmit and amplify the vibration stress.
Solution Approach 2:
The patent changes the strength parameter of the sacrificial fracture portion relative to the support leg portions, creating a deliberate strength differential. The sacrificial fracture portion is designed with lower strength so it fractures first under stress. This parameter change enables the system to predict failure without requiring the structure to be at specific locations, as the strength differential ensures proper stress distribution and fracture sequence regardless of position.
3Measurement precision
If a sacrificial fracture portion is designed with shorter lifetime than solder joint portions, then failure prediction accuracy is improved, but the structure becomes more complex
Solution Approach 1:
The patent segments the structure into distinct functional parts: support leg portions with normal strength and a sacrificial fracture portion with reduced strength. This segmentation allows each part to perform its specific function - the support legs provide structural support while the sacrificial portion provides failure indication. The clear division of functions improves measurement precision without requiring overly complex integrated designs.
Solution Approach 2:
The patent applies parameter changes by modifying the strength parameter of the sacrificial fracture portion to be lower than that of the solder joint portions and support legs. This deliberate parameter differentiation ensures that the sacrificial portion fractures first, providing accurate failure prediction. The simplicity of this single parameter change (strength differential) avoids the need for complex multi-parameter control systems.
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 enables reliable prediction of solder joint failures due to vibration stress with high design freedom, ensuring timely inspection and replacement of components, thereby enhancing the operational efficiency of electric appliances.
Implementation Method 1
failure under thermal stress can be predicted because difference in the thermal expansion coefficient between component materials is utilized
Implementation Method 2
the load amplifying portion transmits, to the sacrificial fracture portion via the pair of support leg portions, vibration that is applied to the substrate
Data Source
AI summary
A failure prediction device is provided for predicting, using a structure having a high degree of design freedom, failure at a soldered joint due to vibration stress, and a circuit board using the same. The failure prediction device is disposed on a substrate having a mounting component that is fixed thereon through a solder joint. The failure prediction device is provided with a load amplifying portion that includes a pair of support leg portions each having one end to be fixed to the substrate or the mounting component, and a sacrificial fracture portion that is supported by the other ends of the pair of support leg portions, wherein the load amplifying portion transmits, to the sacrificial fracture portion via the pair of support leg portions, vibration that is applied to the substrate.