pcb types

  PCB Introduction and Categories

PCB, short for printed circuit board, is the supplier of electronic components and electronic connections. The key advantage of PCBs is to greatly reduce the errors of routing and assembly and to increase the degree of automation and fabrication efficiency.

PCBs can be classified into different types according to different classification standards. Based on the number of layers, PCBs can be classified into single-layer PCBs, double-layer PCBs and multi-layer PCBs. Based on the substrate material, PCBs can be classified into rigid PCBs, flexible PCBs and flex-rigid PCBs. Based on application fields, PCBs can be divided into low-frequency PCBs and high-frequency PCBs. With the development of technology and the advent of new material, some special types of PCBs come into being, such as metal core PCBs, smt PCBs carbon-film PCBs, etc.

Following lines share major types of circuit boards and quickly review their advantages and disadvantages.

1. Single-layer PCBs

Single-layer PCBs are the most basic type of PCB. They contain only one conductive layer and as such constrict their use to simple low density designs. Accordingly, they are low cost and well suited to simple and high volume products.

2. Double-layer PCBs

Double-layer PCBs probably are the most common type of PCB. They allow for the routing of traces around each other by jumping between a top and bottom layer by way of vias. The ability to cross paths from top to bottom greatly increases the PCB designer's flexibility in circuits designing and lends itself to greatly increased circuit densities. This type of board is relatively low cost, but only allows an intermediate level of circuit complexity and does not lend itself to electromagnetic interference reduction techniques.

3. Multi-layer PCBs

Multi-layer PCBs further increase the complexity and density of PCB designs by adding additional layers beyond the top and bottom layers seen in a double-sided configuration. With the availability of over thirty layers in multilayer PCBs configurations, multi-layer PCBs allow designers to produce very dense and highly complex designs. Quite often the extra layers in these designs are used as power planes, which both supply the circuit with power and also reduce the electromagnetic interference levels emitted by designs. Lower EMI levels are achieved by placing signal levels in between power planes. It's also of note that increasing the number of power planes in a PCB design with increase the level of thermal dissipation a PCB can provide, which is important in high power designs.

4. Aluminum Backed PCBs

Typically used in high power applications, aluminum packed PCBS are the ultimate solution to thermal heat dissipation issues. Consisting of a thin circuit layer adhered to a thick aluminium backing by way of a thermally conductive dielectric, aluminium backed designs can keep high power components cool under heavy loads. Aluminum backed PCBs are often found in high power LED products and switching power supplies. This kind of PCBs also offer high levels of mechanical rigidity and low levels of thermal expansion, making them ideal for applications with very tight mechanical tolerances. Finally, aluminum backed PCBs are perfect for applications where the PCB is going to be subject to a great deal of mechanical stress.

5. Flexible PCBs

Flexible PCBs present the perfect solution to creating reliable and repeatable interconnections between electronics boards. They allow for complicated interconnections to be printed rather than made using discrete conductors. The result is a greatly reduced level of complexity in device assemblies and more reliable operation. Flexible PCB designs can also be very complex, with very high signal trace densities and multilayer configurations available to designers.

6. Rigid Flexible PCBs

Rigid-flex PCBs allow for the use of flexible PCBs for the majority of a design while protecting a section of the PCB design that is not intended to be bent. This is of great benefit when you want to use a flexible PCB as the basis of your design. Often flexible PCBs are designed to include surface mount devices in a portion of the flexible board. This section will then be reinforced with a rigid backing to protect the ICs from flexing during use. Flexible PCBs are also much lighter and can fit into tighter housing than their traditional counter parts. Using flexible PCBs, three dimensional designs can also be accommodated in a single PCB. When size and weight are a point of emphasis, flexible PCBs are a great starting point.

7. Flex-rigid PCBs

Flex-rigid designs allow for an interconnection flexible PCB to be permanently connected to a rigid multilayer PCB board. This type of configuration is used when a design calls for very complex PCB, but the designer wants to reduce the complexity of final product assembly by including the flexible interconnection PCB in the fabricated PCB. As such, using a flex-rigid PCB allows for the complete design to be ready upon receipt from the PCB fabricator. Flex-rigid designs also allow for the creation of three dimensional designs and can include multiple rigid and flexible sections.

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