The annoying PCB, also known as the printed circuit board, is an essential component of most modern electronics. Despite its ubiquity and necessity, the PCB can also be a source of frustration for engineers, designers, and hobbyists alike. This article will explore what exactly a PCB is, why they can be annoying to work with, and some tips and tricks to make working with them a little easier.
What is a PCB?
A printed circuit board, or PCB, is a board made of fiberglass or other composite materials that houses and connects electronic components using conductive pathways etched from copper sheets laminated onto the non-conductive substrate. PCBs are used in almost every electronic device, from cell phones to computers to airplanes.
PCBs provide both the physical structure to mount components like integrated circuits as well as the electrical connections between them. The board itself is non-conductive, while the copper lines etched on the surface act as wires to route power between components. The components themselves are soldered onto pads or holes on the PCB to mechanically attach them and complete the circuit.
Types of PCBs
There are several types of PCBs, including:
- Single-sided – Copper traces on one side only
- Double-sided – Copper traces on both sides
- Multilayer – Multiple copper layers laminated together
- Flexible – PCBs made with flexible substrate materials
- Rigid-flex – Combination of rigid and flexible materials
The type used depends on complexity and production volume. Multilayer PCBs are common in complex, compact devices like smartphones.
PCB Manufacturing Process
The PCB fabrication process consists of several steps, including:
- Design – The circuit is designed in CAD software.
- Etching – Copper foil is laminated to the substrate, then etched to form the conductive traces.
- Drilling – Holes are drilled for component leads and vias.
- Plating – Through-holes are plated to connect layers.
- Solder mask – A protective layer is added over the copper.
- Silkscreen – Component outlines, labels, and markings are printed.
- Testing – Boards are electrically tested.
- Assembly – Components are soldered onto the finished PCB.
Why are PCBs Annoying to Work With?
Despite their necessity in electronics, PCBs can often be frustrating to design and troubleshoot for a variety of reasons:
Modern PCBs are extremely complex, making proper design difficult and time consuming. Routing connections on multilayer boards requires specialized skills and software. High density components leave little margin for error.
PCB fabrication capabilities impose several design constraints:
- Minimum trace width and spacing
- Limitations on number of layers
- Minimum hole size for vias and component leads
- Requirements for trace angles and shapes
Designing within these rules is challenging, especially with tight space constraints.
Lack of Flexibility
Once a PCB is fabricated, it is fixed and cannot be changed easily. Any design flaws require a full board respin. No moving or adding traces like on a breadboard.
Finding issues on a PCB is tedious, requiring multimeter tests, microscope inspection, and schematic analysis. Shorts, opens, and faulty connections can be hard to locate.
While producing PCBs in volume is cheap, prototypes with low quantities can be expensive. Small projects may not justify the cost.
Long Lead Times
Even with rush orders, PCB fabrication can take days or weeks. Errors mean another full cycle to get new boards.
Tips for Working with PCBs
Despite their challenges, following some basic design and debugging guidelines can help make working with PCBs less frustrating:
Use Good Design Principles
- Follow manufacturer design rules and guidelines
- Keep high speed signals away from noise sources
- Use bypass/decoupling capacitors for IC power pins
- Carefully route clock and other critical signals
- Isolate analog and digital circuits
Leave Adequate Margins
- More space between traces and pads
- Wider trace widths than strictly necessary
- Extra unused board area
Margins decrease the chance of errors while allowing room for fixes and changes.
Design With Testing in Mind
- Add test points and pads
- Follow good schematic and layout conventions
- Clearly label components, connectors, and test points
A well-designed PCB will be easier to validate and troubleshoot if issues arise.
Use Design Best Practices
- One signal per net name
- Minimize net name crossings
- Consistent component orientation
- Group associated circuitry
Following best practices makes the design and layout cleaner and more understandable.
Validate Before Sending to Manufacturing
- Thoroughly inspect design files
- Check footprint correctness
- Compare schematic and PCB netlists
- Use design rule checking
The most expensive problems to fix are those not caught until after boards are fabricated.
Assemble With Care
- Use proper soldering technique
- Double check component values and orientation
- Visually inspect before applying power
Many issues can be avoided with careful board population and inspection.
Perform Methodical Debugging
- Compare to known good boards
- Thoroughly check power and ground connections
- Methodically isolate sections of circuitry
- Check signals with oscilloscope
Following a structured troubleshooting procedure minimizes frustration.
Example PCB Applications
PCBs are used in an incredibly diverse range of electronic devices. Here are some examples of products that depend on printed circuit boards and the types of PCBs they utilize:
Smartphones are packed full of PCBs to connect components like the application processor, storage, wireless modules, display drivers, cameras, and more. They make heavy use of multilayer boards to interconnect over 1000 components in a compact form factor.
The core PCB in computers is the motherboard, which interconnects the CPU, memory, expansion slots, storage, ports, and more. High layer counts over 20 layers allow routing intricate connections between hundreds of components at high speeds.
Modern slim LED and OLED TV designs are enabled by flexible PCBs. These bend and fold to fit into tight spaces and allow cabling to route signals to the ultra-thin display panels. Rigid PCBs mount components like the power supply and LED driver electronics.
Drones make extensive use of PCBs in their flight controllers, motor drivers, telemetry systems, cameras, and other on-board electronics. The PCBs used must be lightweight yet rugged enough to withstand vibration.
Cars contain dozens of PCBs to run systems like engine control modules, infotainment systems, radar, safety systems, and more. Auto-grade PCBs withstand temperature extremes, vibration, and electrical noise.
|Application||PCB Types Used||Key Considerations|
|Smartphones||Multilayer, high density||Compact size, EMI control, high speed signals|
|Computer Motherboards||High layer count, fine features||Many layers for connections, matched trace lengths, impedance control|
|TVs||Flexible PCBs, rigid PCBs||Foldable flex PCBs, low EMI, thermal design|
|Drones||Double-sided, multilayer||Lightweight, durable construction, power delivery|
|Automotive||High reliability PCBs||Withstand vibration, temperature extremes, electrical noise|
In summary, PCBs play a crucial role in electronics by providing the pathways to route signals and power between components. However, their complexity, lack of flexibility, manufacturing constraints, and difficulty troubleshooting makes working with them frustrating at times.
Following design best practices, building in margin for error, thoroughly validating boards, carefully assembling, and methodically debugging helps ease some of the challenges of designing, building, and fixing PCBs. With the right approach, PCBs don’t need to be quite so annoying after all.
PCBs enable the incredible electronics we use everyday, from phones to cars to cutting edge technologies. So while they can be irritating, printed circuit boards will continue to be a necessity of the electronics world for the foreseeable future.