Thin Push Switch Using Ultrasonic Welded L-Shaped Substrate
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Solution Overview
Problem
Existing push switches face challenges in reducing thickness without requiring a cutout in the mounting substrate and in minimizing material and fabrication costs, particularly with the use of insert-molded metal parts and flexible printed circuit boards.
Innovation Solution
A push switch design featuring a first substrate with an accommodating recess, peripheral contacts, a movable contact spring, and a second substrate mounted perpendicular to the first, using through-holes for electrical connections and a substrate bonding sheet for enhanced adhesion and waterproofing, allowing for a thin structure with reduced material costs and increased stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a cutout is formed in the mounting substrate to reduce switch thickness, then the switch thickness is reduced, but the manufacturing complexity increases and not all mounting substrates can accommodate this design
Solution Approach 1:
The switch body is divided into an upper switch case and a lower case that can be ultrasonically welded together. This segmentation allows the lower case to be designed with a reduced thickness profile while maintaining structural integrity, eliminating the need for cutouts in the mounting substrate.
Solution Approach 2:
The lower case is nested within the mounting substrate surface, with the switch body extending upward. This nested configuration allows the switch to achieve reduced thickness by utilizing the mounting substrate surface as a support plane, rather than requiring cutouts.
2Ease of manufacture
If insert-molding is used to embed metal contacts and terminals in the switch case, then the switch can be manufactured, but the overall size cannot be further reduced
Solution Approach 1:
Traditional insert-molding processes are replaced with ultrasonic welding technology. The ultrasonic welding process joins the upper switch case and lower case through vibration-induced friction welding, eliminating the need for insert-molding and allowing for more compact dimensions.
3Ease of operation
If a flexible printed circuit board (FPC) is used to attach the push switch to the mounting substrate, then the switch can be mounted, but material and fabrication costs increase
Solution Approach 1:
The FPC component is extracted from the mounting system. Instead of using FPC, the invention uses direct ultrasonic welding between the lower case and mounting substrate, eliminating the need for FPC and associated costs.
Solution Approach 2:
The lower case and mounting substrate are merged into a single integrated structure through ultrasonic welding. This merging eliminates the need for separate FPC components and reduces overall assembly complexity and cost.
4Length of moving object
If the switch body is sunk into a cutout to reduce thickness, then the switch thickness is reduced, but the structural strength and stiffness may be compromised
Solution Approach 1:
The switch body uses composite construction with the upper switch case and lower case joined by ultrasonic welding. This composite structure maintains structural strength while achieving reduced thickness, as the welding creates a strong bond between the two case components.
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
The design achieves a thinner, more cost-effective push switch with improved stiffness and longer service life, comparable to surface-mounted switches, while offering flexibility in switch height adjustment and reduced material and fabrication costs.
Implementation Method 1
an ultrasonic welding device for ultrasonically welding the upper switch case and the lower case to each other
Implementation Method 2
a movable contact spring formed so as to extend across the pair of peripheral contacts and designed to be elastically depressed under pressure
Data Source
Figure 1~2
Figure 3(a)~4(c)
Figure 5(a)~6(b)
AI summary
Provided is a push switch that can be made thin without requiring that a notch be made into a mounting board. The push switch comprises a substrate having an L-shaped cross section, wherein said substrate has a front surface located perpendicular to a mounting surface of a mounting substrate at a side edge of the mounting substrate which does not have a cutout thereof, a back surface for mounting on the mounting substrate, and a side face. Further provided are an accommodating recess, a center contact, a pair of peripheral contacts, a movable contact spring, a protrusion, and a connection pad. A part of said back surface is located at the side edge of the mounting substrate, a portion of the mounting substrate is located just to the right of said protrusion, and a corner portion which is provided at the inside of said L-shaped cross section of said substrate is located at the side edge of the mounting substrate. The substrate is located so that a lower end of said substrate at said front surface side is flush with a lower end of the mounting substrate.