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Through-hole technology
 
 
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Through-hole technology, also spelled "thru-hole", refers to the mounting scheme used for Pin-through-hole (PTH) electronic component
Electronic component

An electronic component is a basic Electronics element usually packaged in a discrete form with two or more connecting leads or metallic pads....
s that involves the use of pin
Lead

Lead is a main-group Chemical element with symbol Pb and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metal ....
s on the components that are inserted into holes drilled in printed circuit board
Printed circuit board

A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using Conductor pathways, or signal traces, industrial etchinged from copper sheets laminated onto a non-conductive substrate....
s (PCB) and soldered
Soldering

Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a relatively low melting point....
 to pads on the opposite side.

Through-hole technology almost completely replaced earlier electronics assembly techniques such as point-to-point construction
Point-to-point construction

Point-to-point construction is the way most electronics circuits were constructed before the 1950s. Point-to-point construction is still used to construct prototype equipment with few or heavy electronic components....
. From the second generation of computers
History of computing hardware

The history of computing hardware encompasses computer hardware, its Computer architecture, and its impact on Computer software.The elements of computing hardware have undergone significant improvement over their history....
 in the 1950s until surface-mount technology became popular in the late 1980s, every component on a typical PCB was a through-hole component.

While through-hole mounting provides strong mechanical bonds when compared to surface-mount technology
Surface-mount technology

Surface-mount technology is a method for constructing Electronics circuits in which the components are mounted directly onto the surface of printed circuit boards ....
 techniques, the additional drilling required makes the boards more expensive to produce.






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Three Ic Circuit Chips
Through-hole technology, also spelled "thru-hole", refers to the mounting scheme used for Pin-through-hole (PTH) electronic component
Electronic component

An electronic component is a basic Electronics element usually packaged in a discrete form with two or more connecting leads or metallic pads....
s that involves the use of pin
Lead

Lead is a main-group Chemical element with symbol Pb and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metal ....
s on the components that are inserted into holes drilled in printed circuit board
Printed circuit board

A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using Conductor pathways, or signal traces, industrial etchinged from copper sheets laminated onto a non-conductive substrate....
s (PCB) and soldered
Soldering

Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a relatively low melting point....
 to pads on the opposite side.

Through-hole technology almost completely replaced earlier electronics assembly techniques such as point-to-point construction
Point-to-point construction

Point-to-point construction is the way most electronics circuits were constructed before the 1950s. Point-to-point construction is still used to construct prototype equipment with few or heavy electronic components....
. From the second generation of computers
History of computing hardware

The history of computing hardware encompasses computer hardware, its Computer architecture, and its impact on Computer software.The elements of computing hardware have undergone significant improvement over their history....
 in the 1950s until surface-mount technology became popular in the late 1980s, every component on a typical PCB was a through-hole component.

While through-hole mounting provides strong mechanical bonds when compared to surface-mount technology
Surface-mount technology

Surface-mount technology is a method for constructing Electronics circuits in which the components are mounted directly onto the surface of printed circuit boards ....
 techniques, the additional drilling required makes the boards more expensive to produce. They also limit the available routing area for signal trace
Signal trace

In electronics, a signal trace on a printed circuit board is the equivalent of a wire for electrical conduction signal s. Each trace consists of a flat, narrow part of the copper foil that remains after etching....
s 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 capacitor
Electrolytic capacitor

electrolytic capacitor is a type of capacitor that uses an ionic conducting liquid as one of its plates with a larger capacitance per unit volume than other types, they are valuable in relatively high-current and low-frequency electrical electrical network....
s or semiconductor
Semiconductor

A semiconductor is a material that has electrical conductivity between those of a Electrical conductor and an electrical insulation; it can vary over that wide range either permanently or dynamically....
s in larger packages such as the TO220
TO220

The TO-220 is a style of electronic component package, commonly used for transistors, silicon-controlled rectifiers, and integrated circuits....
 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
Rule of thumb

A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination....
 for creating a through-hole on a PCB is to make the drill diameter 0.008” (0.2mm) larger than the part’s lead. The installation of discrete through-hole parts (e.g. resistor, capacitors, and diodes ), is done by bending the leads 90 degrees in the same direction, inserting part in the board, bending leads located on the back of the board in opposing directions to improve the part's mechanical strength; finally, soldering the leads such that the solder seeps through to both sides of the board.

See also

  • Via (electronics)
    Via (electronics)

    In printed circuit board design, via refers to a pad with a plated hole that connects copper signal trace from one layer of the board to other layer....