LONDON – STMicroelectronics NV has claimed it is the first company that has mass-produced MEMS microphones in plastic packages. ST has patented a technology development that allows this while, at the same time, saves space and increases durability, the company said.
Typical applications are mobile phones and tablet computers, noise-level meters and noise-cancelling headphones.
ST's plastic-packaged MEMS, soon to arrive on the market, measure 2-mm by 2-mm. This gives rise to the possibility of embedding silicon membrane microphones inside silicon cavities in other devices, the company said.
ST's MEMS microphones are suitable for assembly on flat-cable printed-circuit boards and the package technology allows the sound-hole to be in either the top or the bottom of the package. Top-port packaging tends to suit applications in laptops and tablet computers, while bottom-port microphones are more suitable for mobile phones, ST said.
Compression and drop test show that the plastic-packaged microphones are more durable than traditional metallic-lid devices. When subjected to 40-newtons force microphones in metallic packages collapsed whereas ST microphones in plastic packages did not. Similarly when devices in both categories were exposed to 40 drops from a height of 1.5 meters with a static force of 15N applied on the package. The superior robustness holds for both flat-cable printed-circuit boards (PCB) and traditional rigid PCB designs.
The plastic-package microphones integrate an internal shielding cage for electromagnetic immunity and are compatible with standard surface-mount assembly machinery and conventional pick-and-place equipment.
It is hard to dismiss the lackluster performance of metal can packages without knowing more on the design geometry. But it is good to know that plastic packages performed / met the specifications.