Acoustic Housing
Microelectromechanical systems use specialized surface-mount enclosures that feature an open pathway to the surrounding atmosphere. Such an arrangement, known as a qfn port package, allows sound waves or pressure changes to reach the internal silicon die while maintaining a small footprint. This design employs a molded plastic or metal lid with an engineered hole on the top or bottom surface.
It enables direct physical interaction between the environment and the sensor. An engineered port minimizes signal attenuation and phase shifts.
Internal Routing
Acoustic or pressure signals enter through the port and travel through a sealed cavity directly to the active membrane of the sensor. The physical alignment of the port with the die is critical to avoid signal attenuation or phase delay. Metal or plastic seals prevent pressure leaks inside the package housing.
Reflow Guideline
Soldering these components to printed circuit boards requires careful control of the thermal profile and stencil thickness. If solder paste flows into a bottom-ported hole, it can block the acoustic path or destroy the sensor membrane. Board designers must use protective tape or precise solder mask clearances.
Contamination Risk
The open port makes the sensor vulnerable to dust, moisture and wash solvents during board manufacturing and field operation. Protective membranes can be integrated within the package to shield the delicate silicon structures. These membranes must allow pressure transfer while blocking liquid water and particulate entry.
