Through-hole technology
From Wikipedia, the free encyclopedia
Through-hole technology, also spelled "thru-hole", refers to the mounting scheme used for electronic components that involves the use of pins on the components that are inserted into holes drilled in printed boards and soldered to pads on the opposite side.
While through-hole mounting provides strong mechanical bonds when compared to surface-mount technology techniques, the additional drilling required makes the boards more expensive to produce. They also limit the available routing area for signal traces on layers immediately below the top layer on multilayer boards since the holes must pass through all layers to the opposite side. To that end, through-hole mounting techniques are now usually reserved for bulkier components such as electrolytic capacitors or semiconductors in larger packages such as the TO220 that require the additional mounting strength.
Design engineers often prefer the larger through-hole to surface mount parts when prototyping because they are easier to handle, insert, and solder. A rule of thumb for creating a through-hole on a PCB is to make the drill diameter 0.008” larger then the part’s lead. To install a SIL through-hole part (e.g. resistor, capacitors, and diodes ), bend leads 90 degrees in the same direction, insert the part in the board, bend leads located on the backside of the board in opposing directions to improve the part's mechanical strength; finally, solder the leads such that the solder seeps through to both sides of the board.
