What are PCBs?

A printed circuit board consists of several different layers of material. They also come in single- and double-sided designs.

The conductive material is copper, made into sheets, which are laminated onto a surface that is nonconductive. Holes called vias are drilled through the circuit board, allowing conductors located on different layers of the circuit board to be connected.

There is a variation on a printed circuit board called a printed wiring board. This is a printed circuit board that doesn't have any components embedded into the board itself.

When a printed circuit board is loaded with components, it is sometimes referred to as a printed circuit board assembly. An alternate term is circuit card assembly, which is used by the Association Connecting Electronics Industries, the IPC.

Printed circuit boards are used by manufacturers and hobbyists. The manufacturing process for printed circuit board is complex enough that some hobbyists have the circuit board designs produced by an outside source.

The easiest way to get a look at a printed circuit board is to simply open up a desktop computer and take a look at the components that make it function. The largest PCB in the computer will be the motherboard. The motherboard will be affixed to the PCB via various connectors, many of which are profiled below. These connectors provide stable electrical connections and, because of their designs, also ensure that heavy devices - such as video cards, other peripheral devices and so forth - don't damage the board or fall off of the board due to their own weight.

Newer computers tend to have different types of PCB connectors than older computers and comparing the two can provide insight into the evolution of the connectors used with printed circuit boards.

Many printed circuit board connectors are provided with a type of locking mechanism that prevents the connection from being broken accidentally. Because of the rather delicate nature of many printed circuit boards, it's important to check any connector that's hooked up to a printed circuit board for such a locking mechanism before force is used to attempt to remove it.

Producing the boards

The process used for producing printed circuit boards today is streamlined and makes it possible for manufacturers to affordably mass-produce complex electronic devices.

A design automation tool is used to capture a schematic of the circuit desired. From there, the proposed design is created, determining the dimensions of the card required and the template required.

A printed circuit board can have up to 12 layers. This allows for the creation of very complex circuitry and, in addition to determining how many layers on a printed circuit board will be needed, the plane that serves as the ground and the plane that serves as the power are decided at the next phase.

The line impedance of the circuit board is determined and the placement of the various components that will make up the circuit board is then determined. Next, signal traces are routed and, finally, a Gerber file is produced, which is used to finalize the design of the printed circuit boards.

While designing printed circuit boards is a long and labor-intensive process, the fact that the circuit boards can be manufactured very quickly and inexpensively offsets this. Once a printed circuit board has been designed, it can be manufactured repeatedly for a relatively low cost compared to having circuit boards soldered individually or circuits completed by point-to-point connections.

Manufacturing PCBs

Manufacturing PCBs is also very complex process that involves several different steps. The aforementioned Gerber file is utilized to design a circuit board, but when the circuit board is actually ready to be produced, that information is translated into a CAM system.

Using a series of additive and subtractive processes, manufacturers are able to produce printed circuit boards that are exact copies of one another, allowing for a great deal of consistency in the electronic devices that they produce.

Through-Hole versus Surface Mount

Printed circuit boards can be produced with through-hole designs or surface mount designs. Through-hole designs require that the person assembling the printed circuit board put the electric leads for each component through holes in the board. The leads are soldered on both sides for stability.

Through-hole designs were dominant until the 1980s. They have since been replaced by surface mount designs.

While surface mount printed circuit boards came about in the 1960s, they were not the dominant type of printed circuit board until the 1990s. These printed circuit boards do not require that the assembler place leads through holes in the circuit board. Rather, flat metal tabs on the ends of the components are soldered directly to the surface of the printed circuit board. This helps reduce the weight and cost of printed circuit boards.

Some components are etched into the circuit board itself, eliminating the need to have an outside component installed directly on the board or into the board through holes.

Some of the components on printed circuit boards can be removed and recycled by de-soldering them from the circuit board and attaching them to a new circuit. Many of the components on circuit boards, however, are simply recycled along with the circuit board itself, given the difficulty of de-soldering and the fact that printed circuit boards and the components that make them up are very inexpensive.

Types of PCB Connectors

There are many different types of PCB connectors, which is not surprising, given the many different types of components and devices that are attached with these connectors. Some printed circuit board connectors are designed to operate under stressful conditions, to support relatively heavy loads and to provide stability and safety under those circumstances. Other printed circuit board connectors are much more delicate.

Printed circuit board connectors often come in kits, with both ends of the connection and the hardware required to install the connector to the printed circuit board. Some printed circuit board connectors can only work with one type of a connector and others are designed to work with stripped wires, making it possible to hook up devices generically, without relying upon a specific type of connector to complete the circuit.

  • Backplane Connectors: Backplane connectors have a parallel design and are easily visible on just about any computer motherboard. These connectors are designed so that each pin in the connector has an electrical connection with the same relative pin in all of the other connectors. This creates what is called a computer bus.
  • DIN 41612 Connectors: DIN 41612 connectors are utilized in the telecom industry and in data applications. They are common sites in rack-based equipment. They can have anywhere from 1 to 3 rows of contacts and the rows of contacts can be connected if needed.
  • DIN 41617 Connectors: DIN 41617 Connectors are capable of handling high current, making it still common, despite the fact that it is an older type of connector. These connectors come with three different pin counts available and are very compact.
  • FPC Connectors: FPC stands for Flexible Printed Circuit. FPC Connectors are utilized in applications where compact connections are required. Some of the features of these connectors include zero insertion force capability, right angle versions and a very low profile height, the last aspect being one of the main reasons that these have become very popular.
  • IDC Connectors: An IDC connector is put into place by stripping wire in selected places. This creates a very reliable type of connection and completely eliminates the need for the designer to manually strip any wire insulation. These are available in many different designs. The acronym stands for insulation displacement connector.
  • Jumper & Shunts Jumpers and shunts are connectors that allow the bypassing of a particular electric circuit or closing an electrical circuit that is open. These are very common on computers and motherboards and typically have several pins that can be utilized with jumpers. These are referred to as jumper blocks. These are usually small, plastic rectangular devices with a conducting material inside of them.
  • LVDS Connectors: LVDS stands for Low Voltage Differential Signaling. LVDS Connectors are used on cables that are typically used in applications involving monitors, including industrial monitors, television monitors, gaming monitors and other, similar, uses.
  • PCB Connector Housings: PCB connector housings provide a safe and secure connection for the systems to which they are attached. Some of them are outfitted with locking mechanisms that ensure a secure connection.
  • PCB Connector Kits: PCB connector kits generally come with both sides of the connector, along with other hardware required to hook the connector up to a PCB. These provide a convenient way to order the parts required to complete a project.
  • PCB DIN Connector Accessories: PCB header accessories include devices that are designed to protect the headers from harm and that are designed to make it easier to connect devices more securely and more quickly to a motherboard or another electronic device.
  • PCB Headers: PCB headers provide the male end of the connection used on a circuit board. They typically have pins on them, corresponding to the female connector.
  • PCB Pin & Socket Strips: PCB pin and socket strips provide the pins and the receivers for many different types of PCB connectors. These are available in a wide variety of different designs, mounting styles and sizes.
  • PCB Sockets: PCB sockets receive the relevant type of connector. They can be affixed to the PCB board along with other accessories, making for a more stable and secure connection.
  • PCB Terminal Blocks PCB terminal blocks provide a versatile solution for hooking up electronic devices. They are available in a wide variety of different configurations, with pin spacings corresponding to metric and imperial measurements. Some pin blocks are also numbered, making it easier for engineers to prototype and assemble their own devices.
  • RITS Connectors: RITS stands for remote I/O terminal system. RITS Connectors make it convenient to hook up any type of terminal and consist of a system that allows a wire to be inserted into the terminal and clamped down using the device, allowing for generic connectors.
  • XFP & SFP Cage & Connector Assemblies: XFP and SFP connectors are used in telecom, notably with fiber-optic connections. The SFP is a more compact design.XFP & SFP Cage & Connector Assemblies include the various parts required to complete either type of connection. The cages provide protection for the connections.
  • XFP & SFP Cage Accessories: XFT and SFP Cage accessories include devices that are designed to make it easier to mount cages and to protect the connectors themselves from the environment.
  • XFP & SFP Cages: XFP and SFP Cages provide a safe installation environment for fiber-optic connections. They are typically made out of metal and may be designed in many different sizes and mounting configurations.
  • XFP & SFP Connectors: XFP & SFP Connectors are themselves used to connect fiber-optic lines. These are transceivers designed for 10 GB single fiber connections.