Through-hole technology

This is because of difficulties in use with automated component placement machinery, and poorer reliability because of reduced vibration and mechanical shock resistance in the completed assembly.

For electronic components with two or more leads, for example, diodes, transistors, ICs, or resistor packs, a range of standard-sized semiconductor packages are used, either directly onto the PCB or via a socket.

While through-hole mounting provides strong mechanical bonds when compared to SMT techniques, the additional drilling required makes the boards more expensive to produce.

[4] Design engineers often prefer the larger through-hole rather than surface mount parts when prototyping, because they can be easily used with breadboard sockets.

However, high-speed or high-frequency designs may require SMT technology to minimize stray inductance and capacitance in wire leads, which would impair circuit function.

Through-hole (leaded) resistors
Through-hole devices mounted on the circuit board of a mid-1980s home computer . Axial-lead devices are at upper left, while blue radial-lead capacitors are at upper right
Close-up view of an electronic circuit board showing component lead holes (gold-plated) with through-hole plating up the sides of the hole to connect tracks on both sides of the board. The holes are circa 1 mm diameter.
Axial- (top) and radial- (bottom) leaded electrolytic capacitors
Components like integrated circuits can have upwards of dozens of leads, or pins
A box of drill bits used for making holes in printed circuit boards. While tungsten-carbide bits are very hard, they eventually wear out or break. Making holes is a considerable part of the cost of a through-hole printed circuit board.