A CDE Definition
A circuit board packaging technique in which the leads (pins) on discrete components and chips are inserted through holes in the printed circuit board and soldered from beneath. Until the late 1980s and prior to surface mount technology, all devices on circuit boards were thru-hole. Although chips are mostly surface mounted these days, some chips are still thru-hole, and most discrete devices such as resistors and capacitors are thru-hole.
Thru-hole devices have a strong bond with the board but require an extra drilling step. They also eliminate the board real estate underneath from being used for other layers. See surface mount.
Through the Board
Thru-Hole Vs. Surface Mount
A circuit board packaging technique in which the leads (pins) on the chips and components are soldered on top of the board. Boards can be made faster because surface mount technology (SMT) eliminates drilling holes for thru-hole devices, in which the pins go through the board and are soldered underneath.
Surface mount also allows the real estate under the device to be used for other layers by the board designer. In addition, the boards can be smaller because the chips are smaller; for example, SMT packages such as BGA have no leads extending out from the sides (see BGA). Contrast with socket mount and thru-hole.
Surface Mount Vs. Thru-Hole
Gull-Wing Surface Mounts
Discrete and Surface Mounted
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