Capacitance Measurement for Adhesive Bond Quality Verification
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Solution Overview
Problem
Existing methods fail to reliably assess the thickness and quality of the adhesive layer between a substrate and a thermally and electrically conductive body, which is crucial for ensuring effective heat dissipation and preventing damage to electronic components under high thermal loads.
Innovation Solution
A non-destructive method using capacitance measurement between the conductive body and conductor tracks, with offset compensation and dielectric constant determination, to infer the adhesive layer's thickness and quality, ensuring a thin, full-surface bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thermally conductive adhesive is used to bond the substrate to the heat sink, then heat dissipation is improved, but the adhesive layer thickness and bonding quality cannot be reliably verified
Solution Approach 1:
The patent replaces mechanical thickness measurement methods with electrical capacitance measurement. By forming a capacitor where the substrate and heat sink act as opposing plates with the adhesive layer as the dielectric, the thickness can be determined through electrical measurement rather than mechanical means, enabling non-destructive and precise verification of the adhesive layer thickness
Solution Approach 2:
The patent utilizes the dielectric properties of the adhesive material to determine its thickness. By measuring the capacitance of the formed capacitor and using the known dielectric constant of the adhesive, the thickness of the adhesive layer can be calculated, transforming the measurement problem from mechanical domain to electrical domain with higher precision
2Temperature
If the adhesive layer is made thinner to improve thermal conductivity, then heat dissipation is improved, but the risk of defects and incomplete bonding increases
Solution Approach 1:
The patent implements a feedback mechanism where the capacitance measurement provides information about the adhesive layer quality, allowing for verification and adjustment. By comparing the measured capacitance with expected values, the bonding process can be monitored and controlled to ensure sufficient quality even with thin adhesive layers
Solution Approach 2:
The patent performs capacitance measurement after the bonding process to verify the adhesive layer quality before the product is put into service. This preliminary verification ensures that thin adhesive layers have been applied correctly and are free of major defects, providing confidence in the bonding quality
3Ease of manufacture
If conventional bonding verification methods are used, then the bonding process is simple, but air inclusions and bonding defects cannot be detected
Solution Approach 1:
The patent replaces complex non-destructive testing methods with a simple electrical capacitance measurement. By using the substrate and heat sink as capacitor plates, the measurement can be performed using basic electrical equipment, maintaining ease of manufacture while enabling detection of air inclusions and bonding defects through capacitance value analysis
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 provides reliable assessment of the adhesive bond quality, ensuring sufficient heat dissipation and preventing failures in thermally sensitive components by accurately measuring the adhesive layer's thickness and detecting air pockets or impurities.
Implementation Method 1
the measured capacitance to infer the quality of the adhesive layer, a non-destructive measurement of the layer thickness and determination of the adhesive quality is easily achieved. The electrically and thermally conductive body on one side and the conductor tracks on the other serve as opposing plates of a parallel-plate capacitor
Implementation Method 2
a thermally conductive adhesive, which in turn is connected to a base plate via screws. Both the power modules and, depending on the installation location, the surrounding environment generate heat that must be dissipated by the electrical components on the substrate
Data Source
Figure 1~2
Figure 3
AI summary
The method involves arranging an electrical circuit (10) having conductive paths (12) between a substrate (6), on the upper surface (8) and electronic components (14), and fastening an electrically and thermally conductive body (2) at the rear side (16) of the substrate for forming an adhesive layer. The conductive paths and the electrically and thermally conductive body are connected to the opposing poles of a voltage source by contact tabs. The contact tabs are connected with the conductive paths by the supply contacts of the electrical circuit.