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Surface Mount Technology (SMT) SMC/SMD Surface mount components/surface mount device. Component usually refers to passive items such as resistors, capacitors, ect. Device refers to active items such as SOIC, PLCC, ect. MELF Metalized electrode face (or most end up lying on floor). Cylindrical and usually color-coded resistors or solid-colored diodes. SOIC Small outlined integrated circuit. This smaller version of the DIP has leads that are gull-wing shaped to allow connection to the board surface. PLCC Plasitc leaded chip carrier. Normally a four-sided quad package in which an IC is installed with J-type leads extending out from the sides of the package then downand rolled under the body of the device. SOJ Small outline J leaded package similar to a DIP but for surface mount applications only. SSOL-16J Small outline, 16 J leads. Footprint The metal pads on the substrate intended for mounting specific SMC/SMDs. SOT/SOD Small outline transistor/small outline diode. A plastic leaded component in which diodes and transistors are packaged. Gull-wing leads are used. TCE(CTE) Thermal coefficient of expansion (coefficient of thermal expasnsion). The rate of expansion or contraction of a material when its temperature is increased or decreased. Coplanarity Each lead of a multileaded item being at the same level or plane. This is extremely important to ensure that all lead are properly soldered. LCCC Leadless ceramic chip carrier. A ceramic package with an IC mounted to form a surface mount device. Its termination areas for soldering are built into the ceramic material and do not allow for TCE of the device versus the substrate, especially if the component and board materials are different. QFP Quad Flat pack. Four-sided device normally with extended gull-wingtype leads. TSOP Thin shrink small outline package. Similiar to SOIC but smaller packaging and closer lead spacing (8 to 24 leads) with leads protruding from the ends of the package. Type I Assembly Circuit board with SMC/SMDs on one or both sides. Type II Assembly Circuit board with a combination of THM on the top of the board and SMC/SMDs on the top and bottom of the board. Type III Assembly Circuit board with THM on the top of the board and passive surface mount on the bottom. Solder paste/cream Semiliquid substance made up of tiny solder balls, flux, solvent and an an antislumping agent. Reflow soldering The reflowing of the solder paste.cream used to solder SMC/SMDs onto the board surface. The solder paste/cream is heated until it melts and flows, usually using an infared, convection or vapor phase heating system. Measling The damage to a circuit board caused by ovberheating. Usually shows as small white dots on fiberglass epoxy boards around the overheated area. This is the weave of the fiberglass seperating inside the board. Blind via Surface mount connection hole where the board is multilayered and the hole is attached to the surface (top or bottom) and only goes partway through the board. Buried via Similar to a blind via, except that it connects internal layers only and is not exposed to top or bottom suraces. Ball grid array A large IC carrier with small solder protrusions on the bottom of the package for attaching to the appropriate pads on the circuit board. Difficult if not impossible to remove/install without the proper equipment.