Rotary Variable Resistor Size and Linearity Trade-off
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Solution Overview
Problem
Existing rotary variable resistors face challenges in reducing size while maintaining electric linearity, as smaller sizes exacerbate film thickness variations, leading to deteriorated electric linearity, particularly when resistor patterns are formed by printing.
Innovation Solution
A rotary variable resistor design featuring an insulating substrate with a resistor pattern and current collector pattern, where the resistor pattern is formed by screen printing with controlled film thickness variations, ensuring a maximum dimension of the resistor pattern and electric linearity within specific constraints (Z≦4.0 and Z×L<10), and using a metal member to lock the slider for stable contact, thereby reducing size and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the resistor pattern size is reduced to miniaturize the rotary variable resistor, then the device size is reduced, but the electric linearity deteriorates due to increased influence from film thickness variation
Solution Approach 1:
The patent applies parameter changes by carefully controlling the film thickness parameters of the resistor pattern. Specifically, it sets the film thickness within a precise range (0.5-2.0 μm) and controls the thickness variation ratio (t2/t1) to be between 0.8-1.2. By optimizing these physical parameters of the printed resistor pattern, the invention achieves both miniaturization (Z≤4.0mm) and maintains acceptable electric linearity (Z×L<10), resolving the contradiction between size reduction and precision maintenance.
2Ease of manufacture
If screen printing is used to form the resistor pattern, then manufacturing cost is reduced, but film thickness variation increases leading to deteriorated electric linearity
Solution Approach 1:
The patent resolves this contradiction by establishing specific parameter ranges for screen printing processes. It controls the paste viscosity, screen mesh count, printing pressure, and drying conditions to achieve film thickness within 0.5-2.0 μm with variation ratio (t2/t1) of 0.8-1.2. These optimized printing parameters enable cost-effective screen printing while maintaining the film thickness uniformity required for good electric linearity in miniaturized devices.
Solution Approach 2:
The patent applies preliminary action by pre-controlling the paste formulation and screen printing parameters before the actual printing process. The paste is prepared with specific rheological properties, and the screen is pre-treated with appropriate mesh specifications. This preliminary preparation ensures that when printing occurs, the film thickness is automatically controlled within the required range, preventing thickness variation issues before they can affect electric linearity.
Data Source
AI summary
A rotary variable resistor includes an insulating substrate, a resistor pattern and a current collector pattern that are provided on the insulating substrate, a rotor that is mounted on the insulating substrate in a rotatable manner, and a slider that is mounted on the rotor and makes sliding contact with the resistor pattern and the current collector pattern to cause the resistor pattern and the current collector pattern to be conducted to each other. When a maximum dimension of the resistor pattern, which defines a variable resistor, is Z [mm] and electric linearity is L [%], Z≦4.0 and Z×L<10 are satisfied.