Interfacial Hygroscopic Swelling Stress Analysis in Surface Mount Encapsulants
Interfacial hygroscopic swelling stress arises from differential moisture expansion, compounding thermal mismatch and driving package delamination during reflow.
Thin Small Outline Package
Component Housing
Low profile rectangular enclosures provide a space efficient way to mount memory chips and logic devices onto circuit boards. The thin small outline package is defined by its reduced height which often measures approximately 1 millimeter. This form factor is common in portable electronics where vertical space is restricted.
Lead Configuration
Gull wing terminals extend from the longer sides of the body to make contact with the mounting pads. Within a thin small outline package the leads are spaced at a fine pitch of 0.5 or 0.65 millimeters.
Thermal Path
Heat generated by the silicon die must travel through the plastic molding or the lead frame to reach the ambient air. Small dimensions of a thin small outline package limit the surface area available for cooling which necessitates careful board layout for heat dissipation. Designers often add thermal vias or copper planes to the circuit board to help pull heat away from the package pins.
Board Density
Footprint area is minimized by the narrow body width while maintaining enough lead length for reliable solder joints. Using a thin small outline package allows designers to place components closer together and reduce the overall size of the electronic assembly.