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What Is IC Packaging?

Integrated circuits pack millions of transistors onto silicon chips a few millimeters square. You cannot, however, use the chip by itself; it must have packaging to protect the chip from the environment and carry signals to the circuitry in which it operates. Electronics manufacturers have developed many types of standard packaging that enhance the reliability and usability of ICs.

Package Body
- IC chips are sensitive to humidity and are easily contaminated. In addition, the microscopic features on the chip are fragile. The body of the IC packaging seals the chip within a rectangular block of hard plastic or ceramic material, preventing any contact between the device and the outside world. The packaging allows easy, safe handling of the IC, by automated machinery or assembly technicians. Manufacturers label the outside of the part body with logos, part numbers and other information.
Leads
- During manufacturing, machines bond tiny wires to points on the IC chip, creating paths into the package for signals and electrical power. Metal leads or other conductive contacts on the outside of the package provide a connection to the IC̵7;s wiring and a sturdy mounting system for the part. Simple ICs have three to eight leads, more complex ICs such as microprocessors have hundreds of leads. When an equipment maker builds a circuit, they solder the IC directly to a printed circuit board or mount the part in a socket. Soldered ICs are more rugged though difficult to replace; sockets add cost but ease replacement.
Through-Hole and Surface Mount Device
- IC packages come in two basic varieties: through-hole and surface-mound device. The leads in a through-hole are long enough to pass through circuit board holes and protrude slightly on the other side to facilitate soldering. An SMD package has no protruding leads; instead it uses flat metal contacts that sit directly on the surface of a circuit board. SMD parts are generally smaller and less expensive than through-hole components.
Heat Management
- Some ICs, especially microprocessors, become hot during use. The IC packaging helps prevent the components from overheating and burning up. These ICs usually have a heat-resistant ceramic body with metal strips or tabs that conduct heat away from the IC. External parts such as heat sinks and fans fit onto the IC̵7;s packaging. The heat sink clamps or bolts onto the IC to make good thermal contact with the part.

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