Printed Circuit Board Design

Designing a printed circuit board was once a daunting task, but design automation tools and standard schematics for many common applications have made printed circuit board design almost commonplace. You don’t even have to own expensive software. We have state of the art schematic capture software and can translate your circuit quickly and efficiently into a printed circuit board design that follows industry standards and can be manufactured at any production facility.

There are several basic steps to printed circuit board design. With some basic information in hand, our knowledgeable professionals are ready to design a printed circuit board tailored to your needs.

A printed circuit board (or PCB) electrically connects and mechanically supports electrical or electronic components using pads, conductive tracks, and other traits etched from at least one sheet layers of copper laminated onto or between non-conductive substrate’s sheet layers. Generally, the components are soldered onto the printed circuit board to both mechanically fasten and electrically connect with them.

Characteristics of printed circuit boards

Through-hole technology

The first printed circuit boards made use of through-hole technology, mounting electronic components by leads soldered onto copper traces on one side and inserted through holes from the other side. Board may be more compact double-sided or just single-sided with an unplated component side, with components soldered on both sides.

Surface-mount technology

In surface-mount technology, the components were mechanically redesigned to have small end caps or metal tabs that could be soldered directly on the surfaces of printed circuit boards, instead of wire leads to pass through holes. The component placement on both sides of the board become common, and the components became much smaller, permitting much smaller printed circuit board design assemblies with much higher circuit densities.

Circuit properties of the printed circuit board design

In fast switching radio-frequency circuits the capacitance and inductance of the printed circuit board conductions become substantial circuit elements, often undesired; conversely, they may be utilized as an intentional part of the printed circuit board design, as in antennae, fuses, distributed element filters, and fuses, obviating the requirement for more discrete components.

Materials

  1. RoHS compliant PCB: In consumer items, the European Union bans the use of lead, among other heavy metals. If PCBs are to be sold in the EU, they must comply with RoHS (or restriction of hazardous substances).
  2. Laminates: Laminates are formed by curing under temperature layers and pressure of paper or cloth with thermoset resin to formulate an integral final piece of uniform thickness. The differences in resin percentage, cloth thickness, and cloth weaves are used to accomplish the desired final dielectric characteristics and thickness.
  3. Key substrate parameters: Usually, the circuit board substrates are composite dielectric materials. The composites comprise a reinforcement (sometimes nonwoven, usually a woven, glass fibers, sometimes even paper), a matrix (usually an epoxy resin) and in certain cases, a filler is added to the resin (for instance, ceramics; dielectric constant may be increased by using titanate ceramics).
  4. Common substrates: The materials often encountered are FR-2, phenolic cotton paper, or phenolic paper; FR-4 a woven fiberglass cloth impregnated with epoxy resin; aluminum; and flexible substrates, can be laminated to a thin stiffener or can be a standalone copper-clad foil.
  5. Copper thickness: the Copper thickness of PCBs may be directly specified or as the weight of copper per area, which is far easier to measure. Heavy copper layers are used to help dissipate heat and for high current.
  6. Safety certification (US): The component safety requirements are covered by the Safety Standard UL 796 for printed wiring boards for use as components in appliances or devices. The testing analyzes features such as live electrical parts, heat deflection, electrical tracking, maximum operating temperature, and flammability.
Circuit Design USA

Schematic Capture

Schematic capture is the process through which the electronic components are diagrammed for connection. It is like a blueprint for a complex machine or an architectural drawing for the construction of an elegant home. If you already have a drawing of your circuit, we will convert it to an electronic schematic following standard practices that will make commercial production of your printed circuit board design much easier. If you need us to design the circuit for you, our specialists will capture it electronically from the very beginning of the process.

Component Footprints

When the schematic of the circuit is completed, we place physical outlines of the electronic components onto the schematic. These outlines are called footprints. We use software with a netlist of standard components, but we also create custom component footprints and datasheets, using the IPC 7351A standard naming convention, as needed for your project.

The placement of component footprints is an essential part of board design. The footprints are ultimately transferred to the board as electrical connections to the signal traces and allow electrical contact with the board components when they are physically added to the PCB.

Board Outline

After the component footprints are prepared, we determine the dimensions of your board. We typically design standard rectangular boards, but we can also customize the shape to fit your particular design application. We match the board outline to sheet templates to determine the board density, the location of the mounting holes, and keepout requirements.

We optimize component placement to create the most compact board possible while considering the heat signature of each component. It is at this stage that we decide upon the placement of the ground plane, power plane, and the number of signal planes. Basic printed circuit board designs could require only a dual signal plane, but more complex or compact designs may require 10 or more layers.

We also determine the line impedance during the board outline stage. The impedance is a function of the copper thickness, the dielectric of the board, and the separation of the traces on the board layers. We can route traces using stripline or microstripline placement, and our specialists will explain the advantages of each technique to you when we suggest the routing plan.

Routing The Traces

We use computerized equipment to automatically route noncritical signal traces onto the PCB design. Critical traces, such as clocks and power supplies, are manually routed. The routing of traces, using stripline or microstripline techniques, is always designed to minimize electromagnetic interference and to provide the cleanest signal transfer possible.

Design Rule Checks

We periodically check for design rule violations during the entire process. When we design your board, you will never have to worry about duplicated reference designators, misconnected inputs, crowded traces, or space violations with board components. We guarantee that our PCB design will be commercially producible.

Outputing The Gerber Files – Circuit Design USA

All PCB manufacturing facilities need Gerber data to place a printed circuit board design into production. The last step in our design process is the generation of these files. The Gerber data is generated by PCB design layer. Each board layer, no matter how complex, is converted to a single file. The Gerber files tell manufacturing machines how to repetitively construct each layer to create your finished PCB. We use the RS-274X industry standard for these files.