Shielded Microphone Assembly for Mobile Device EMI Isolation
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Solution Overview
Problem
Existing mobile communications devices face challenges in shielding microphones from electromagnetic noise emitted by nearby antennas and achieving cost-effective electrical connections that accommodate manufacturing tolerances during assembly.
Innovation Solution
A shielded microphone assembly using a conductive electromagnetic shield with a resilient, insulating separator that cooperates with the device housing and circuit board to establish an electrical connection and absorb assembly pressures, effectively isolating the microphone from electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive gasket is used to provide electrical connection between the electromagnetic shield and circuit board, then electrical connection is achieved, but manufacturing cost increases and assembly complexity increases
Solution Approach 1:
The electromagnetic shield is designed with an integrated conductive lip that directly contacts the circuit board, eliminating the need for a separate conductive gasket. This merging of the shield and connection element reduces both cost and assembly steps while maintaining reliable electrical connection for electromagnetic shielding.
Solution Approach 2:
The conductive lip on the electromagnetic shield serves multiple functions: it provides electromagnetic shielding, establishes electrical ground connection, and accommodates assembly tolerances through its resilient design. This multi-functionality replaces what previously required separate components.
2Reliability
If a conductive gasket is used to provide electrical connection between the electromagnetic shield and circuit board, then electrical connection is achieved, but assembly difficulty increases
Solution Approach 1:
The electromagnetic shield is designed with an integrated conductive lip that directly contacts the circuit board, eliminating the need for a separate conductive gasket. This merging of the shield and connection element reduces both cost and assembly steps while maintaining reliable electrical connection for electromagnetic shielding.
Solution Approach 2:
The conductive gasket intermediary component is extracted and eliminated from the assembly. The shield's integrated lip directly establishes the electrical connection, simplifying the assembly process by removing a critical placement step.
3Strength
If resilient parts are included to absorb stack pressure, then damage from excess pressure is prevented, but device complexity increases
Solution Approach 1:
The electromagnetic shield incorporates a resilient lip made of flexible conductive material that absorbs stack pressure between rigid components. This flexible element prevents damage from excess pressure while maintaining electrical connection, eliminating the need for separate resilient parts.
Solution Approach 2:
The conductive lip on the electromagnetic shield serves multiple functions: it provides electromagnetic shielding, establishes electrical ground connection, and accommodates assembly tolerances through its resilient design. This multi-functionality replaces what previously required separate 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 solution provides effective shielding against electromagnetic noise while reducing manufacturing costs by using a resilient separator to manage assembly tolerances and ensure reliable electrical connections.
Implementation Method 1
a resilient separator (e.g., an o-ring-type separator) positioned over the shield, forming an assembly configured to co-operate with the housing and the circuit board
Implementation Method 2
a grounded shield (hereinafter alternatively referred to as an 'electromagnetic shield') is typically used to surround or enclose the microphone so as to isolate the microphone, electromagnetically, from such radiation
Implementation Method 3
The electromagnetic shield, when formed as a shielding can, may have a lip whereby the shielding can electrically connects to the circuit board by means of the lip
Data Source
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AI summary
A shielded microphone, and method for shielding a microphone, are provided for use in a communications device having a circuit board and a microphone, especially where the device also has an antenna in close proximity to the microphone. The microphone is provided in an electromagnetic shield (e.g. formed as a shielding can) and a resilient separator (e.g. o-ring or disk) is provided over the shield. The device housing is stacked over the separator and shield, while the latter are stacked over the circuit board so that the separator and shield, with microphone there under, are sandwiched between the housing and the circuit board. By this sandwiching the separator is loaded onto the shield to drive the shield directly against the circuit board to make an electrical ground connection therewith, the microphone also being electrically connected to the printed circuit board. The microphone is thereby enclosed between the circuit board and the shield, such that the shield shields the microphone against electromagnetic energy radiated by the proximate antenna. The resilience of the separator accommodates the variation in the stacking of the components.