Surface Mounted Switch Assembly Stress Reduction
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Solution Overview
Problem
Mechanical switches mounted on printed circuit boards (PCBs) using surface mount technology face stress issues due to the activation mechanism, leading to potential failure of the epoxy bond between copper foil and glass-filled substrate materials.
Innovation Solution
A switch assembly comprising a housing and a support member mounted on the PCB, where the support member, formed of plastic with a T-shaped portion, limits the movement of the switch member to reduce stress on the adhesive, using fasteners to secure the assembly and minimize movement in the direction of the activating force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pushbutton switch is mounted directly onto PCB surface using surface mount technology, then manufacturing process is simplified, but stress on epoxy bond between copper foil and glass filled substrate material increases causing connection failure
Solution Approach 1:
A support member is introduced as an intermediary element between the pushbutton switch and the PCB. This support member absorbs and distributes the stress generated during switch activation, preventing direct transmission of stress to the epoxy bond between copper foil and substrate material, thereby maintaining connection reliability while preserving surface mount manufacturing simplicity
Solution Approach 2:
The switch assembly is segmented into distinct functional components: the pushbutton switch, the support member, and the PCB. This segmentation allows the support member to independently handle mechanical stress while the electrical connection components remain separate, reducing stress concentration on the epoxy bond and improving overall reliability
2Ease of operation
If pushbutton switch is activated by pressing, then switching function is achieved, but stress is induced into the cured epoxy bond causing eventual connection failure
Solution Approach 1:
The support member is positioned beforehand to provide cushioning support to the pushbutton switch during activation. This pre-positioned support member absorbs the pressing force and distributes it across a larger area, preventing excessive stress concentration on the epoxy bond before failure can occur, thus maintaining both ease of operation and bond strength
Data Source
AI summary
A switch assembly for an electronic device is described. The switch assembly includes a switch member, a housing and a support member. The housing is mounted on a printed circuit board and the switch member is attached to the housing. The support member is mounted on the surface of the printed circuit board adjacent to a back surface of the switch member.