Printed circuit boards are a critical part of the electronics industry, a base component of many electronic designs. They provide mechanical support and create electronic pathways within appliances and devices (mobile phones, computers, microwaves, coffee makers, entertainment systems, smart watches, tablets, radios, satellite navigation, televisions, stereo sets, DVD players, game consoles, refrigerators, alarm clocks, X-Ray screens, CT scanners, ultrasonic scanners, etc.). They’re found everywhere! Their uses are almost endless!
What is a PCB?
A printed circuit board (PCB) is an electronic assembly that utilizes copper conductors (alternating layers of conductive copper with layers of insulating material) to create electrical connections between a variety of components. Electronic components are mounted on a board and traces connect the components together to form a working circuit or assembly. PCBs furnish rigid, mechanical support for electronic components and a compact package that can be integrated into an end product. They enable devices to be mounted in an enclosure. PCBs are designed using specialized software packages. They can be single-sided (one copper layer), double-sided (two copper layers on both sides of a substrate layer) or multi-layer (outer and inner layers of copper, alternating with layers of substrate).
What are the components of a PCB?
PCBs are made up of a variety of electrical components. Each component is essential to the function of the device, ensuring smooth operation.
- Resistors are one of the most commonly used components in a PCB. They transmit an electric current, producing a voltage and dissipating electric power as heat. They come in a variety of materials and are colour-coded according to their resistance and value. The most familiar is an axial resistor with leads on both long ends and a body inscribed with coloured rings.
- Capacitors are the second most common component in a PCB. They hold electrical charge (electrostatic energy) and release it when more power is needed in the circuit. They generally accomplish this by collecting opposite charges on two conductive layers that are separated by an insulating material. Though there are many types of capacitors (high-capacity electrolytic, diverse polymer, ceramic disc, etc.), the classic radial style with two leads protruding from the same end is the most common.
- Transistors are amplifiers that switch/control electronic signals in a PCB and are a fundamental building block of electronics. The most common is a bipolar transistor composed of three pins (base, collector, emitter). There are three main types of transistors:
- NPN-type transistors involve a small current flowing through the base to the emitter, turning on another circuit that causes a larger current to flow from the collector to the emitter.
- PNP transistors reverse this process.
- FETs use an electric field to activate another circuit.
- Inductors store energy in the form of a magnetic field, generated when current flows through. They’re essentially a coil of wire, the greater the number of windings the greater the magnetic field. Inductors are used to filter and/or block signals within the PCB.
- Transformers transfer electrical energy from one circuit to another, increasing or decreasing voltage. They consist of a soft iron core with coils of wire wound around. The primary coil is for the source circuit and the secondary coil is for the circuit the energy is being transferred to.
- Diodes allow electrical current to flow in one direction only, providing zero resistance in one direction and high resistance in the other. They’re used to block current from flowing in the wrong direction, causing damage to the board/device.
- Sensors detect changes in environmental conditions (light, humidity, air quality, sound, motion, moisture, etc.) and generate an electrical signal that corresponds to that change. The signal is then sent to the other components of the PCB.
- Silicon Controlled Rectifiers (SCRs) involve two transistors working together. They have three leads and four silicon layers and function as switches, not amplifiers, making them suited for switching large amounts of power. A single pulse activates the switch.
- Integrated Circuits (ICs) are circuits/components that are made of thin wafers of semiconductor material. They’re the brains of a wider circuit, are encased in a black plastic housing, have visible contacts (leads, contact pads) and come in all shapes and sizes. Their diminished profile allows great numbers to be fit onto a single chip.
- Crystal oscillators are the timing devices for circuits that require precise and stable timing elements. They make electronic signals by causing a crystal to oscillate at a specific frequency. They’re stable, economical, and small compared to other timing devices. Crystal oscillators are used as precise timers for microcontrollers.
- Switches are power buttons that control current flow in a circuit, by switching between an open and closed circuit. They can be a slider, rotary, push button, lever, toggle and/or key switches.
- Relays are electromagnetic switches operated via a solenoid. They work as a switch and also amplify currents.
Without these various components, circuit boards would not be fully optimized to attain all their possible potential.
How is a PCB designed?
Software aids designers in progressing through a specific process for circuit board design, beginning with basic electrical drawings and ending with manufacturing file preparation. There are a number of steps involved in the designing of a printed circuit board.
- Setting the parameters: It’s important to know/understand the parameters of the system such as:
a. Current maximums
c. Signal types
d. Capacitance limitations
e. Impedance characteristics
f. Shielding considerations
g. Type and location of circuit components and connectors
h. Detailed net wire listing and schematic
- Creating the schematic: This is the design of the electrical level of the printed circuit board’s purpose and function.
- Creating the layout: At this stage, engineers develop a schematic using a software platform. This graphic shows how the board will operate and where components will be located. The design is loaded and the engineer determines how it will fit in the device.
- Designing the PCB stack-up involves determining the arrangement of copper and insulation layers. The stack-up affects how the engineer can design and fit the PCB into the device.
- Defining design rules/requirements: IPC standards dictate electronics manufacturing, informing engineers of standards/criteria of acceptability and determining design. They are taken into account at this stage of PCB design and development.
- Placing components: Using data sheets, the PCB provider places components in the mechanical layout and sends them to the customer for approval.
- Inserting drill holes: This is the process of creating holes/slots/cavities in a PCB before soldering/mounting components. It’s done with a PCB drill bit which is an automated machine. Holes are created through electrochemical etching or mechanically (drilling, laser cutting, punching). Components and connections inform this step.
- Routing the traces takes place after the components are placed and the drill holes are created. The best route to take to complete each connection is determined. Traces on a PCB carry very specific design requirements that ensure signal integrity during routing. PCB routing connects components on the surface layer to internal layers, known as traces. Routing techniques used for a PCB depend on the signalling standard you’re working with and the required routing topology.
- Adding labels/identifiers: These reference designators show where specific components are located on the board and are essential for traceability during production, assembly, and after-sales distribution. They enable manufacturers to integrate the right units into products.
- Generating design/layout files: The final step in designing a PCB involves files that contain pertinent information. Once these files are generated, the PCB is ready for fabrication, manufacturing, and assembly.
Designing and manufacturing a printed circuit board is a complex process involving many steps, materials, and composition practices. It’s wise to contract this process and your unique requirements to an experienced and knowledgeable team that provides custom electronic manufacturing.
Need a unique PCB for your manufacturing processes? Looking for an experienced and knowledgeable team that provides custom electronic manufacturing? Contact Calgary-based Innovative Manufacturing Source (IMS). Our team of knowledgeable, skilled, dedicated people offers unsurpassed service and products. We serve you through in-house manufacturing capabilities completed on state-of-the-art equipment. Call us at 403.279.7702. Let us be your premier partner and provider of custom electronic manufacturing and metal fabrication services for all of your manufacturing needs. We support customer-specific requirements on all our products.