Flexible Rigid Circuit Board Assembly for Waterproof Personal Care
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Solution Overview
Problem
Existing electronic personal care products, such as razors, face challenges in assembling and sealing electronic components effectively to prevent water ingress while maintaining reliability and cost-effectiveness, especially when exposed to wet environments.
Innovation Solution
A method involving a hollow housing with a first circuit board inserted through one open end and a second circuit board subassembly inserted through the opposing end, where the first circuit board is connected to the second within the chamber, allowing for efficient assembly and sealing of electronic components without the need for complex fixtures, using injection molding and insert molding techniques to create a strong bond and fluid seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If electronic components are made small to fit within a personal care product, then the product size is reduced, but the components become delicate and can break easily
Solution Approach 1:
The circuit board is divided into a rigid end portion and a flexible portion, allowing each section to serve its specific function while maintaining overall reliability. The rigid end provides structural support for connection, while the flexible portion accommodates movement without breaking.
Solution Approach 2:
Different portions of the circuit board have different mechanical properties - the end portion is rigid for stable connection, while the portion extending into the chamber is flexible to prevent breakage. This local differentiation of material properties resolves the contradiction between small size and durability.
2Reliability
If electronic components are sealed against water ingress, then reliability in wet environments is improved, but assembly complexity increases
Solution Approach 1:
The housing simultaneously serves as both the sealing barrier against water and the structural framework for component assembly. The chamber defined by the housing integrates the sealing function with the mounting function, eliminating the need for separate sealing mechanisms and reducing assembly complexity.
Solution Approach 2:
The housing performs multiple functions: it provides the external protective barrier against water, defines the internal chamber for component placement, and structurally supports the circuit board connections. This multi-functionality reduces the number of separate components needed.
3Reliability
If circuit boards are connected within a sealed chamber, then water resistance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The rigid end of the first circuit board is prepared in advance with connection interfaces that match the connector on the second circuit board. This preliminary preparation of connection features allows for straightforward alignment and connection within the chamber without requiring high-precision manufacturing during final assembly.
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
An electronic subassembly for a personal care product with a housing defining a chamber having an open end. A first circuit board having a rigid end is positioned within the chamber and a flexible portion is positioned outside the chamber. A second circuit board is positioned within the chamber. The second circuit board has a connector dimensioned to receive the rigid end of the first circuit board.