Isolating Micro-Machined Accelerometer Zero-G Bias Shifts under Static Thermal Cycles
Static thermal zero-g bias shifts in MEMS accelerometers are isolated by enforcing prolonged thermal dwell periods to decouple stress creep from thermal gradients.
Plastic QFN Encapsulation
Overmolded Structure
Overmolded protective structure applied to a quad flat no-lead semiconductor frame. Plastic qfn encapsulation uses an epoxy molding compound to seal the die and wire bonds against physical damage. It provides a compact and low-profile form factor for surface-mount devices.
Thermal Path
Heat transfer is facilitated by an exposed pad on the underside of the device. Although plastic qfn encapsulation is less conductive than metal, the direct attachment of the die to the leadframe allows for efficient dissipation into the printed circuit board. This design supports higher power densities in small enclosures.
Moisture Sensitivity
Permeability of the epoxy makes the component susceptible to the popcorn effect during solder reflow. Before assembly, plastic qfn encapsulation requires storage in dry packs or baking to remove absorbed water. If the internal moisture vaporizes rapidly, the package may delaminate or crack.
Cost Efficiency
High-volume production is achieved through transfer molding processes that handle hundreds of units in a single cycle. Because the materials are less expensive than ceramic or glass, plastic qfn encapsulation is the standard choice for consumer electronics and industrial sensors. The manufacturing flow includes automated deflashing and singulation steps to ensure the edges are clean and the dimensions meet the JEDEC standards.