Rotation Detector Recessed Resin Sealing Thermal Stress
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Solution Overview
Problem
Conventional rotation detectors face junction failures and part failures due to differences in material expansion and shrinkage between the board and resin, causing thermal stresses as temperature varies.
Innovation Solution
The solution involves forming recessed regions adjacent to electrode forming areas and filling resin within these regions to minimize thermal stress differences between the circuit forming portion and the sealing resin, using electrically conductive adhesives for surface mounting, and designing a casing with specific recess portions to accommodate the resin for effective stress reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resin is used to seal the signal processing circuit, then the circuit is protected and coated, but differences in expansion and shrinkage between the board and resin generate thermal stresses causing junction failures
Solution Approach 1:
The invention introduces a recess portion with a lower expansion coefficient than both the board and resin in the specific region where thermal stress occurs. This local modification creates a stress-absorbing zone that reduces thermal stress concentration at junction portions, thereby improving reliability without compromising the overall sealing function.
Solution Approach 2:
The recess portion acts as an intermediary material between the board and the resin. It mediates the thermal expansion mismatch by providing a transition zone with intermediate expansion characteristics, reducing the direct stress transmission between the board and resin that would otherwise cause junction failures.
2Ease of manufacture
If the board and resin have different material qualities for sealing, then sealing is achieved, but expansion and shrinkage differences cause stresses on parts and junction portions
Solution Approach 1:
The invention maintains the simplicity of using different materials for board and resin while locally introducing a recess portion with specific material properties. This local modification preserves the ease of manufacture through material differentiation while specifically addressing junction strength issues through targeted stress reduction.
Solution Approach 2:
The invention creates a composite structure consisting of three different materials: the board, the resin, and the recess portion material. This composite approach allows each material to be optimized for its specific function while working together to reduce thermal stress, thereby maintaining manufacturing ease while improving junction strength.
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 design effectively reduces thermal stresses on parts and junctions, enhancing reliability and reducing manufacturing costs by minimizing expansion and shrinkage issues and simplifying assembly.
Implementation Method 1
differences in expansion and shrinkage quantities are generated between the board and the resin. These differences cause stresses to be generated on the parts mounted on the board
Implementation Method 2
thermal stresses generated at the part and the junction portion can be reduced
Data Source
AI summary
A rotation detector includes: a magnet to form a magnetic field between the magnet and a rotary member; a magnetism detection element positioned in the proximity of the magnet to detect a variation in the magnetic field due to a rotation of the rotary member; and a signal processing circuit 3 to process a signal from the magnetism detection element and which is coated and sealed with a resin 7, recess portions 14a, 14b which are lower than electrode forming regions 15 are formed at adjoining regions adjacent to electrode forming regions 15 on which surface electrodes 4 are installed and resin 7 is filled within recess portions 14a, 14b. Thus, the rotation detector which can suppress the deficiency generated at a part mounted on a circuit forming portion, at junctions between the part and surface electrodes, or so forth due to expansion and shrinkage involved in a temperature variation can be provided.