Circuit Housing Fixing Points for Thermal Stress Relief
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Solution Overview
Problem
Electronic devices with different thermal expansion coefficients for circuit housings and molding compounds can lead to mechanical stress and detachment, causing potential moisture penetration and electrical damage due to thermal expansion mismatches.
Innovation Solution
The electronic device fixes the molding compound to the circuit housing at spaced-apart points with activated surfaces, using a combination of adhesive substances and thermal deformation counteraction to minimize mechanical stress and prevent moisture ingress, while ensuring secure bonding through surface activation and roughening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the molding compound is fixed to the circuit housing at entirely two-dimensional fixing arrangement, then the connection between molding compound and circuit housing is strengthened, but mechanical stress acts upon the electrical circuit and loads the circuit accordingly
Solution Approach 1:
The fixing arrangement is segmented from a continuous two-dimensional surface into discrete fixing points or localized fixing surfaces spaced apart from one another. This segmentation allows the molding compound to be fixed securely to the circuit housing while creating stress-relief zones between the fixing points that prevent mechanical stress from acting upon the electrical circuit.
2Reliability
If adhesive substance is used to fix molding compound to circuit housing, then detachment is prevented, but manufacturing complexity increases
Solution Approach 1:
The surface properties of the circuit housing are changed through activation (e.g., plasma treatment, chemical etching, or laser treatment) to enhance adhesion between the molding compound and the housing. This parameter change in surface energy or surface roughness allows for strong bonding without requiring additional adhesive substances or complex manufacturing processes.
3Stress or pressure
If spaced-apart fixing points are used, then mechanical stress on circuit is reduced, but connection stability under thermal expansion may be compromised
Solution Approach 1:
The spacing and positioning of the fixing points are specifically designed to accommodate differential thermal expansion between the molding compound and the circuit housing. The fixing points are arranged to allow controlled movement and expansion while maintaining secure attachment, preventing detachment during thermal cycling while still protecting the circuit from excessive mechanical stress.
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 solution effectively minimizes mechanical loads on the electronic circuit, reduces mechanical interference errors, and prevents moisture-induced corrosion or short circuits by ensuring a secure and stable connection between the circuit housing and molding compound, even under thermal expansion.
Implementation Method 1
The circuit housing is activated at at least two fixing points that are spaced apart with respect to one another... the activated circuit housing with a molding compound in such a manner that the enclosed region of the circuit housing comprises at least the fixing points
Implementation Method 2
said molded body having a second coefficient of thermal expansion that is different to the first coefficient of thermal expansion... as a result of the different coefficients of expansion between molding compound and the circuit housing, the two become mechanically stressed with respect to one another
Data Source
AI summary
An electronic device including: an electronic circuit accommodated in a circuit housing having a first thermal expansion coefficient, and a molded body which surrounds the circuit housing, the body having a second thermal expansion coefficient that differs from the first thermal expansion coefficient. The molded body is fixed to the circuit housing at least at two different mutually spaced fixing points on the circuit housing.