<s>
In	O
electronics	O
,	O
through-hole	B-Algorithm
technology	I-Algorithm
(	O
also	O
spelled	O
"	O
thru-hole	B-Algorithm
"	O
)	O
is	O
a	O
manufacturing	O
scheme	O
in	O
which	O
leads	O
on	O
the	O
components	O
are	O
inserted	O
through	O
holes	O
drilled	O
in	O
printed	O
circuit	O
boards	O
(	O
PCB	O
)	O
and	O
soldered	O
to	O
pads	O
on	O
the	O
opposite	O
side	O
,	O
either	O
by	O
manual	O
assembly	O
(	O
hand	O
placement	O
)	O
or	O
by	O
the	O
use	O
of	O
automated	O
insertion	O
mount	O
machines	O
.	O
</s>
<s>
Through-hole	B-Algorithm
technology	I-Algorithm
almost	O
completely	O
replaced	O
earlier	O
electronics	O
assembly	O
techniques	O
such	O
as	O
point-to-point	O
construction	O
.	O
</s>
<s>
From	O
the	O
second	B-Architecture
generation	I-Architecture
of	I-Architecture
computers	I-Architecture
in	O
the	O
1950s	O
until	O
surface-mount	O
technology	O
(	O
SMT	O
)	O
became	O
popular	O
in	O
the	O
mid	O
1980s	O
,	O
every	O
component	O
on	O
a	O
typical	O
PCB	O
was	O
a	O
through-hole	B-Algorithm
component	O
.	O
</s>
<s>
Components	O
with	O
wire	O
leads	O
are	O
generally	O
used	O
on	O
through-hole	B-Algorithm
boards	O
.	O
</s>
<s>
Originally	O
,	O
radial	O
leads	O
were	O
defined	O
as	O
more-or-less	O
following	O
a	O
radius	B-Protocol
of	O
a	O
cylindrical	O
component	O
(	O
such	O
as	O
a	O
ceramic	O
disk	O
capacitor	O
)	O
.	O
</s>
<s>
Extra	O
insulation	O
with	O
heat-shrink	O
tubing	O
may	O
be	O
used	O
to	O
prevent	O
shorting	B-Application
out	I-Application
on	O
nearby	O
components	O
.	O
</s>
<s>
These	O
improvisations	O
are	O
often	O
seen	O
in	O
breadboard	O
or	O
prototype	B-Application
construction	O
,	O
but	O
are	O
deprecated	B-General_Concept
for	O
mass	O
production	O
designs	O
.	O
</s>
<s>
For	O
electronic	O
components	O
with	O
two	O
or	O
more	O
leads	O
,	O
for	O
example	O
,	O
diodes	O
,	O
transistors	O
,	O
ICs	O
,	O
or	O
resistor	O
packs	O
,	O
a	O
range	O
of	O
standard-sized	O
semiconductor	B-Algorithm
packages	I-Algorithm
are	O
used	O
,	O
either	O
directly	O
onto	O
the	O
PCB	O
or	O
via	O
a	O
socket	O
.	O
</s>
<s>
While	O
through-hole	B-Algorithm
mounting	O
provides	O
strong	O
mechanical	O
bonds	O
when	O
compared	O
to	O
SMT	O
techniques	O
,	O
the	O
additional	O
drilling	O
required	O
makes	O
the	O
boards	O
more	O
expensive	O
to	O
produce	O
.	O
</s>
<s>
To	O
that	O
end	O
,	O
through-hole	B-Algorithm
mounting	O
techniques	O
are	O
now	O
usually	O
reserved	O
for	O
bulkier	O
or	O
heavier	O
components	O
such	O
as	O
electrolytic	O
capacitors	O
or	O
semiconductors	O
in	O
larger	O
packages	O
such	O
as	O
the	O
TO-220	B-Algorithm
that	O
require	O
the	O
additional	O
mounting	O
strength	O
,	O
or	O
for	O
components	O
such	O
as	O
plug	O
connectors	O
or	O
electromechanical	O
relays	O
that	O
require	O
great	O
strength	O
in	O
support	O
.	O
</s>
<s>
Design	O
engineers	O
often	O
prefer	O
the	O
larger	O
through-hole	B-Algorithm
rather	O
than	O
surface	O
mount	O
parts	O
when	O
prototyping	B-Application
,	O
because	O
they	O
can	O
be	O
easily	O
used	O
with	O
breadboard	O
sockets	O
.	O
</s>
<s>
Ultra-compact	O
designs	O
may	O
also	O
dictate	O
SMT	O
construction	O
,	O
even	O
in	O
the	O
prototype	B-Application
phase	O
of	O
design	O
.	O
</s>
<s>
Through-hole	B-Algorithm
components	O
are	O
ideal	O
for	O
prototyping	B-Application
circuits	O
with	O
breadboards	O
using	O
microprocessors	O
such	O
as	O
Arduino	O
or	O
PICAXE	B-Device
.	O
</s>
