Hearing Instrument MID and Mini PCB Routing
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Solution Overview
Problem
Hearing instruments face challenges with complex and costly flexible PCBs, requiring high precision and limited by single-layer MID structures, which hinder miniaturization and increase assembly complexity and costs.
Innovation Solution
A combination of an MID circuit frame and a mini rigid PCB is used, with the mini PCB enabling complex routing and additional conductive layers, reducing the need for a large Flex-PCB and facilitating 3D assembly, while the MID frame provides a mechanical structure for component placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible PCB is used for complex routing, then routing flexibility is improved, but manufacturing cost and assembly precision requirements increase
Solution Approach 1:
The patent divides the circuit board system into two segments: a rigid PCB providing structural support and basic routing, and a flexible PCB add-on layer providing complex routing where needed. This segmentation allows the system to achieve routing flexibility only in necessary areas while maintaining ease of manufacture for the majority of the board structure.
Solution Approach 2:
The flexible PCB is applied locally only to specific areas requiring complex routing, rather than making the entire PCB flexible. This local quality approach ensures that routing flexibility is provided precisely where needed while keeping the overall manufacturing process simpler and more cost-effective.
2Ease of manufacture
If a single-layer MID structure is used, then manufacturing simplicity is improved, but routing complexity and miniaturization capability worsen
Solution Approach 1:
The patent transitions from a single-layer MID structure to a multi-layer construction by adding a flexible PCB layer on top of the rigid PCB. This dimensional change from one layer to multiple layers enables complex three-dimensional routing paths while maintaining the manufacturing simplicity of standard multi-layer PCB techniques.
3Stability of the object's composition
If a rigid PCB is used, then structural stability is improved, but routing flexibility and space utilization worsen
Solution Approach 1:
The patent merges the advantages of rigid and flexible PCBs by combining a rigid PCB structure with a flexible PCB add-on layer. The rigid PCB provides structural stability and mechanical support, while the flexible layer contributes routing flexibility and space utilization, achieving a synergistic effect that combines both benefits.
4Manufacturing precision
If manual assembly is used for complex structures, then assembly precision is improved, but productivity and automation level worsen
Solution Approach 1:
The flexible PCB is pre-assembled and pre-tested before being integrated with the rigid PCB structure. This preliminary action allows complex assembly operations to be performed on a manageable scale, ensuring precision while enabling subsequent automated integration into the final product, thereby improving both precision and productivity.
Data Source
AI summary
A hearing instrument uses an MID (Molded Interconnect Device) to replace a complexly folded and expensive flexible PCB (Printed Circuit Board) inside hearing aids and enables the use of complex MID frames in hearing instruments. An additional routing building block is provided for the very complex routing around active electronic components, e.g. chips or ASICs and small passive electronic components. It includes a small, preferably rigid mini PCB provided for the complex routing. A large Flex-PCB is therefore replaced by a combination of an MID circuit frame and a mini PCB. The mini PCB enables complex routing of conducting paths and thus helps to increase integration while the MID circuit frame provides for a mechanical structure that enables and alleviates placing and connecting components such as microphones or receivers at respective mounting positions, e.g. at openings of a hearing aid housing.