Common Nomenclature in the PRC World
You’ll likely see a lot of printed circuit board terminology if you’re just starting out as a PCB designer. It’s not always easy to understand what these terms actually mean. Many engineering courses don’t focus on PCB design but instead focus on systems design or semiconductors. These are all important areas, but circuit boards are what binds them together. It is, therefore, important to be familiar with basic terminology.
Below is a list of terms for printed circuit boards that we have compiled for new designers. Understanding these terms will allow you to communicate better with colleagues and help you understand the manufacturing process of printed electronics.
Vias allow current to flow from one layer to the next. It is important to select the best PCB via options for board development. This can affect turnaround times and increase manufacturing costs.
A trace on a PCB is a small transmission line that the fabricator creates by cutting from a copper layer. The parameters of the trace on a PCB are length, width, impedance, and copper weight. This determines the board’s signal integrity. High-speed applications such as those that use high-speed designs require coordination between trace design, material selection, and signal routing to ensure integrity and the best possible signal routing.
Silkscreen is an image layer that depicts polarity symbols and component orientation indicators. It also includes labels, component footprints, reference indicators, labels, labels, and other identifications. The silkscreen component is used to complete the manufacturing process of the board. This top layer of information does not impact the functionality of a PCB. However, designers and fabricators should include it to eliminate assembly problems and optimize the board’s manufacturing.
Pitch refers to the distance between adjacent pins or pads of a component. As PCBAs become smaller and denser, so do component packages. The space between adjacent pins or pads has also changed. This makes pitch an important design parameter. The pitch is important for components with high pin density. It determines the solder mask process that will be used to prevent assembly problems such as solder bridging.
During the design phase, it is crucial to have a precise PCB layout pattern. This includes the footprint pad layout or actual footprint for each package of components in the circuit. This pattern determines the location of each component during assembly and may include a reference indicator or polarity marking.
PCB MANUFACTURING FILES
The PCB manufacturing files contain all the information, specifications, and images required by the contract manufacturer for fabricating and assembling boards. The most popular formats are Gerber which can carry multiple files, or the IPC2581, which is one CAD file.
The location of the pin or lead for a component is defined by a pad on a board. The combination of the pads forms the component’s footprint. The designer will decide which footprint the component will use early in the design process. Each footprint contains a number of pads that can be used to solder the component to the board. The pads for SMT components are made of solid copper shapes. Through-hole components require pads with PTH vias that run the length of the entire board. While pads can be seen for most components even after they are assembled, packages such as BGAs or CSP may conceal them beneath their bodies.
Two identifiers, or part numbers, are assigned to each component of a board. The manufacturer assigned a component number to each component. The second is the reference number that identifies each component and its specific locations on the Bill of Materials. A board can contain multiple components that have the same manufacturer’s part numbers, but each component will have its own unique reference identifier to locate its location on the board. As the main means to ensure supply chain integrity, traceability is provided by the manufacturer’s part numbers. This number is essential for the selection of components during the design phase. A good selection determines the success, quality, reliability, and functionality of the board.
DESIGN RULE OR DRC CHECK
Design rule checks compare the design specifications to a set of guidelines that have specific limitations. These guidelines may be based on standards or DFM parameter ranges. These restrictions or design rules must be followed by designers when designing PCB layouts. These constraints ensure regulatory compliance and manufacturing capability for a PCB assembly.
Cutouts can be used to remove board areas by design and may also include slots. These may be required for installation purposes. Sometimes cutouts are necessary for installation purposes. Sometimes, cutouts are necessary to reduce board thickness. While most boards are rectangular in shape, there are many other forms of PCBs that can be used.
The shortest distance along the board’s surface between two entities is called creepage. For assembly and reliable operation, creepage standards are established by design and manufacturing guidelines.
Clearance is the distance between two entities on a board. This could include the distance between two entities in the air, such as the clearance across a slot. Another example is how far a component is from the board’s edge.
Copper weight refers to the amount of copper in a PCB’s stack-up. Copper weight refers to the amount of copper per 1 ft x 1 ft area. It is not the total copper weight on the layer surface. Copper thickness is directly proportional to its weight.
Controlled impedance is essential for signal integrity in high-speed signal transmission applications. It is possible to maximize signal fidelity and minimize interference by matching trace geometry and material impedance.
The total height of a board is its thickness, including any components. Because of the smaller size of electronic circuit boards, they have been reduced. Designers are required to increase the number and thickness of multilayer boards in order to route more signals. This allows for greater functionality and greater complexity.
BILL OF MATERIALS (BOM)
A BOM, also known as a bill of materials, is a list that lists all the items required to make a printed circuit board. This list contains information about the component part numbers and the reference identifiers of all the components that will be used in the PCBA.