Silicon Substrate Thermal Expansion Mechanics in Inertial Sensors
Substrate thermal expansion creates packaging shear stress that warps MEMS proof masses, demanding central single-anchor isolation and polynomial offset calibration.
Plastic Quad Flat No-Lead
Package Format
Surface-mount integrated circuit housings use a leadframe with pads on the bottom instead of projecting pins. A plastic quad flat no-lead package offers a small footprint and low profile for high-density electronic assemblies. The central thermal pad provides an efficient path for heat transfer to the circuit board.
Thermal Performance
Low thermal resistance allows for higher power dissipation in a compact size. Using a plastic quad flat no-lead package requires solder paste application to ensure a connection to the thermal pad.
Assembly Challenge
Inspection of the solder joints is difficult because the connections are hidden beneath the package body. Soldering a plastic quad flat no-lead package often requires X-ray inspection to verify the integrity of the hidden pads.
Standard Verification
Dimensions and tolerances are governed by JEDEC standards to ensure compatibility with automated placement machines. A plastic quad flat no-lead package must pass moisture sensitivity testing before it can be used in a production line. Coplanarity of the bottom pads is verified to prevent open circuits or shorts.
Testing also includes a solderability check where the pads are dipped into a solder bath and inspected for uniform wetting. The absence of compliant leads means that the board material must be selected to match the expansion of the plastic to prevent solder fatigue over time.