Some common PCB laminates used for PC Boards are:
- Double sided Laminate
- Two layers of copper tracks, one each side of the board
- Plated Through Hole
- PTH - each hole is copper plated providing an electrical connection
between two sides of the PCB
- Fibreglass-resin laminate (FR4)
- Solder Mask Over Bare Copper
- SMOBC - colored (often green) insulating ink everywhere except connections
- Component legend
- Identifying lettering, component outlines and values in white or yellow
- Tinning is application of Solder to all exposed copper, increasing
- Hot oil levelled
- Hot oil - or hot air - levelling makes the tinning flat, so that surface
mount components can be positioned reliably.
Different methods of PCB construction:
- A rigid PCB of thickness 0.062", with wire-leaded components mounted
on only one side of the PCB, with all the leads through holes, soldered and
clipped. Conventional circuitry is generally easier to debug and repair than
- Surface Mount Technology (SMT) or devices (SMD)
- A PCB with tag-leaded components soldered flush to PCB pads. Holes are
still needed on the PCB, but not where the component leads are attached.
Surface mount circuitry is generally smaller than conventional. Surface
mount is generally more suited to automated assembly than conventional.
- Surface mount & conventional mix
- In practice, most boards are a mix of surface mount and conventional
components. This can have its disadvantages as the two technologies require
different methods of insertion and soldering.
- Double sided Laminate
- A bare PCB laminate having tracks on both sides, normally with PTH holes
connecting circuitry on the two sides together.
- Double sided Component Assembly
- Mounting components on both sides of the PCB. Normally only surface mount
circuitry would be mounted on both sides of a PCB.
- A PCB Laminate may be manufactured with more than two layers of copper
tracks by using a sandwich construction. The cost of the laminate reflects
the number of layers. The extra layers may be used to route more complicated
circuitry, and/or distribute the power supply more effectively.
- Gold plated
- Certain areas on a PCB may be gold plated for use as contact pads. Unless
the whole PCB is gold plated before etching, this technique is limited in
its application, normally, to pads on the edge of a PCB, as an electrolytic
plating bar must be attached to the pads, and then removed part way through
the PCB manufacturing process.
- Flexible PCB
- A technique used extensively with membrane keyboards, combination
connector/circuit boards, and circuit boards to fit in awkward shapes - eg
- Chip On Board (COB)
- Where the IC die is attached direct to a PCB, and bond out wires from the
IC connect directly to PCB lands. The chip is then covered with a black blob
of epoxy. A technique used mostly with very high volume, cost sensitive
applications, eg musical greeting cards.
- Phenolic PCB
- As distinct from Fibreglass, Phenolic is a cheaper PCB laminate material.
- circuit board mounted to another circuit board - such as a plug in card.
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