Circuit Board and Plated-Through Hole (PTH) Information
printed circuit board, or PCB, is used to mechanically support
and electrically connect electronic components using conductive
pathways, tracks or signal traces etched from copper sheets
laminated onto a non-conductive substrate. It is also referred
to as printed wiring board (PWB) or etched wiring board.
PCB populated with electronic connectors and components
is called a printed circuit assembly (PCA), printed circuit
board assembly or PCB Assembly (PCBA). In informal use the
term "PCB" is used both for bare and assembled
boards, the context clarifying the meaning.
vast majority of PCBs are manufactured with "1 ounce
copper" on the outer layers. If there are inner layers,
they are almost always manufactured with "1/2 ounce
thickness of the copper layer on the PCB affects the behaviour
of the circuit. PCB copper thickness is usually measured
in ounces per square foot, or frequently, just ounces. It
can also be given in micrometres, inches or mils.
layer" printed circuit boards have trace layers inside
the board. One way to make a 4-layer PCB is to use a two-sided
copper-clad laminate, etch the circuitry on both sides,
then laminate to the top and bottom prepreg and copper foil.
of Circuit and Design of PCB
efficient laying out of traces on a PCB is a complex skill,
and requires much patience. This task has been made vastly
easier with the advent of readily available PCB layout software,
but it is still challenging.
or electrical engineer design the circuit, and a layout
specialist design the PCB. PCB design is a specialized skill.
There are numerous techniques and standards used to design
a PCB that is easy to manufacture and yet small and inexpensive.
PTH (plated-through holes), additional steps of electroless
deposition are done after the holes are drilled, then copper
is electroplated to build up the thickness, the boards are
screened, and plated with metal. The metal becomes the resist
leaving the bare copper to be etched away.
picture above is a Plated-Through Hole in an ten layer board.
The amount of plating used in the hole depends on the number
of layers in the printed circuit board, however only the
least amount of metal is used for this process. Holes through
a PCB are typically drilled with small-diameter drill bits
made of solid coated tungsten carbide.