Electronics

SMT

Surface-mount technology (SMT) is a method to design and assemble electronic circuits in which the components are mounted directly onto the surface of the printed circuit board (PCB). Such components are called Surface Mount Devices (SMDs). In portable electronics such as mobile phones, notebook PCs, cameras, camcorders or MP3 players it has largely replaced the Through Hole (TH) technology of fitting components with wire leads into holes in the circuit board. TH technology is currently widely used in e.g. desktop PCs, TVs, or entire industry segments such as automotive, white goods, medical, military and aerospace.

An SMT component is usually smaller than its through-hole counterpart because it may have smaller leads, short leads, flat-stamped contacts, a solder ball grid array (BGA), or terminations incorporated in the body of the component.

Advantages of SMT	Disadvantages of SMT
Smaller parts Denser layout Cheaper PCBs (no holes to drill for single-layer PCBs) Improved shock and vibration characteristics Improved frequency response More efficient soldering (difficult to heat holes in multilayer boards Easier to shield from EMI / RFI High productivity manufacturing	More heat generated Small clearance makes cleaning difficult Visual inspection difficult Good joint formation important for mechanical reliability of assembly Harder to handle assembly Greater number of materials to match CTE’s

These advantages are moving an increasing number of new applications to SMT technology, such as shown by Stocko with the world wide first SMT RAST Connector for the Whitegood industry.