Asymmetric Key Structure Sidewall Design for Plug Stress Management
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Solution Overview
Problem
Mechanical key structures face issues with yield rate and quality due to the rupture of the slot's sidewall under horizontal stress from the plug, leading to increased process variation and reduced reliability.
Innovation Solution
The key structure design incorporates a base with asymmetric sidewall thicknesses, featuring a first sidewall thickness perpendicular to the actuating direction and a second sidewall thickness perpendicular to the inner wall, which generates friction and prevents rupture by using a cross-shaped plug and slot configuration, ensuring secure engagement without excessive stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the plug and slot are tightly engaged to ensure secure connection, then the connection reliability is improved, but the sidewall of the slot may rupture due to excessive engaging stress
Solution Approach 1:
The base is designed with non-uniform sidewall thickness, where the first sidewall thickness (parallel to inner wall) is greater than the second sidewall thickness (perpendicular to inner wall). This local quality variation allows the base to have enhanced strength specifically at the critical region where the plug engages, preventing rupture while maintaining secure connection.
Solution Approach 2:
The base structure employs asymmetric sidewall thicknesses rather than uniform thickness. The first sidewall thickness is intentionally made greater than the second sidewall thickness, creating an asymmetric geometry that optimizes stress distribution during plug engagement and prevents sidewall rupture.
2Ease of operation
If the plug is inserted into the slot to enable keycap movement, then the mechanical key structure functionality is achieved, but process variation increases due to sidewall rupture
Solution Approach 1:
By concentrating additional material strength at the critical engagement region through increased first sidewall thickness, the design ensures consistent plug-slot connection without sidewall rupture, thereby reducing process variation and improving manufacturing precision.
3Strength
If the base sidewall thickness is increased to prevent rupture, then the base strength is improved, but the device complexity increases
Solution Approach 1:
Instead of uniformly increasing the entire base sidewall thickness, the design applies additional thickness only at the critical first sidewall region where stress concentration occurs during plug engagement. This localized approach enhances base strength where needed while minimizing overall device complexity.
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 enhances the yield rate and quality of mechanical key structures by preventing base rupture and ensuring reliable operation, thereby improving the overall performance and durability of the key structure.
Implementation Method 1
The slot has an inner wall pressing the plug and generating friction
Data Source
AI summary
A key structure includes a keycap and an actuator. The actuator is coupled with the keycap and enables the keycap to move reciprocally along an actuating direction. One of the actuator and the keycap has a base and a slot formed therein, and the other one of the same has a plug. The plug is inserted into the slot in a direction parallel to the actuating direction. The slot has an inner wall pressing the plug and generating friction. The base has a first sidewall thickness perpendicular to the actuating direction and parallel to the inner wall and a second sidewall thickness perpendicular to the actuating direction and perpendicular to the inner wall, wherein the first sidewall thickness is greater than the second sidewall thickness. The disclosure can avoid the horizontal stress generated by the plug when it is inserted into the slot to squeeze against the bas.