Bottom-Ported MEMS Microphone: What You Need to Know

Bottom-ported MEMS microphones are increasingly popular in compact consumer electronics, wearables, and IoT devices. Unlike top-ported designs—where sound enters through a hole on the package’s surface—bottom-ported microphones capture acoustic signals through an opening on the underside of the package. This configuration offers unique advantages and design considerations.

How Bottom-Ported MEMS Microphones Work

A bottom-ported MEMS microphone houses its acoustic inlet on the PCB-facing side of the package. Sound travels through a dedicated via in the PCB before reaching the microphone’s diaphragm. On-chip, a piezo-resistive or capacitive sensor converts diaphragm movement into an electrical signal, which is then digitized by the integrated ADC (PDM or I²S).

Key Advantages

Smaller Footprint
– Eliminates the need for a PCB cutout directly beneath the microphone can, enabling tighter layouts.
Improved Package Protection
– The acoustic port faces the PCB, shielding it from direct contamination (dust, debris) on the device surface.
Uniform Acoustic Field
– Allows tuning of the acoustic path length via PCB hole design, optimizing frequency response.

Design Considerations

PCB Via Quality
Ensure the via diameter and plating process minimize acoustic damping and resonance peaks.
Acoustic Enclosure
Use an acoustic back volume or damping material beneath the PCB to smooth low-frequency response.
Sealing & Conformal Coating
If your device requires liquid protection, plan for selective conformal coating to protect the microphone inlet.

Typical Applications

Wearable Devices (Smartwatches, Fitness Bands)
Bottom-ported designs preserve a sleek exterior while delivering clear voice pickup for calls and voice assistants.
True-Wireless Earbuds
Integration in multi-layer PCBs with minimal height constraints.
IoT Sensors & Smart Home
Discreet placement inside enclosures where surface mounting isn’t possible.

SISTC Bottom-Ported MEMS Microphone Options

Explore our full lineup of MEMS microphones—including both bottom- and top-ported models—on the SISTC MEMS Microphone Category. Our digital series supports PDM and I²S output, with SNR up to 64 dB and AOP to 130 dB SPL.