PCB Assembly (PCBA) Design Guide
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Ultimate PCB Assembly Guide
PCBs, or printed circuit boards are the unsung heroes of modern electronic devices. Most end-users have no idea how the components inside the electronics they know and love work together. However, for engineers, OEMs, and designers, there’s a lot to know — and love — about PCBs.
This PCB design guide was created to help new and seasoned engineers make more informed design decisions early on so they can end up with the perfect components for their products.
Let’s start with the basics:
What is a PCB?
functions:
• House the electronic components
• Connect components for operation
The board itself is made of a non-conducting substrate, such as fiberglass, that is coated with copper on one or both sides. The copper conducts electricity and is etched away from the board leaving the appropriate components to be connected to each other through the circuit.
PCB. PCBA. PCA. What’s the correct name for a printed circuit board with all the components?
There are many acronyms that industry pros use when it comes to printed circuit boards. The most common question head-scratcher being, what’s the difference between a PCB and PCBA?
Here’s a breakdown of what they mean:
PWB – printed wiring board. One of the first terms used when the connectivity of electronic components was simply point-to-point instead of circuit operation.
PCB – printed circuit board. Technically speaking, the term PCB refers to the etched wiring board itself without any of the components installed yet. In 1999, this term was mandated by the IPC Technical Activities Executive Committee as the go-to term for new document development, as the printed circuitry design often has an impact on device function.
PCA – printed circuit assembly. Used after the IPC change in 1999 for clarity.
PCBA – printed circuit board assembly. It’s the printed circuit board with all of the electronic components installed.
PCB is the most popular term when referring to the whole, assembled shebang. So be sure to clarify which type of PCB you need when communicating with manufacturers and outside vendors — the basic board, or the fully connected printed board assembly (PCBA).
For a deeper dive on the acronyms used for all things printed circuit board, check out this discussion from industry experts.
How does a printed circuit board work?
What are the components of a PCB?
Each of the PCB hardware components has a vital role to play in powering the electronic device. PCB components include:
Diode
LED
Resistors
Capacitors
Switches
Inductors
Battery
What is PCB made of?
- Substrate – the foundation of the PCB, a substrate is usually made of fiberglass or some other non-conductive material. Substrates can be single or multiple layers.
- Copper – used to transmit electric current, the copper within a PCB takes the place of wires.
- Solder mask – the metal used to create connections between the surface of the PCB and the electronic components. The solder mask protects the electronic traces underneath from unfavorable conditions.
- Silkscreen – a layer of ink traces that are used to label electronic components, warnings and other features unique to that device’s connectivity.
Before moving into the production of final PCB production, a prototype must be validated to ensure all components are connected and work properly to power the device.
What are the different types of PCB available?
- Rigid PCBs – designed not to bend or move from their original shape or placement.
- Flexible PCBs – made to fold, twist and flex into the desired configuration. They are thinner and more lightweight and can accommodate unique shapes.
Flexible PCB vs. Rigid Cost
Here’s how the two compare from a financial perspective:
Rigid PCBs
Flexible PCBs
Next, how many layers do you need to get the job done?
Single Layer PCB
A board made out of a single layer of base material or substrate. Typically, one side of the base material is coated with a thin layer of metal on one side of the substrate. Single-layer PCBs are ideal for rapid production due to their simplicity in design and ease of automation.
Double-layer PCB
A board that contains soldered electrical connections on both sides. This is achieved when copper or another conductive material is applied to both sides of the board. For added flexibility, double-sided PCBs can utilize a through-hole or surface mount (SMT) design.
Multi-layer PCB
Used in more complex designs, multi-layer boards include up to four layers. Multi-layer PCBs provide added benefits of a smaller footprint and fewer wiring harnesses, which reduces the overall weight. These PCBs are ideal for aerospace, handheld devices, cell and signal transmission, and many other applications.
What are the advantages of using a printed circuit board?
- Minimal space requirements – because all electronic connections occur on the board, there’s no need for multiple wires to carry the current and take up valuable real estate on the device.
- Simplified installation and troubleshooting – all components are housed on the PCB and clearly labeled, allowing for easy access during assembly and maintenance.
- Streamlined assembly – PCBs allow for quick assembly compared to other means, such as wired connections.
- Secure placement and connectivity – with a PCB, all electronic components are soldered to the board, ensuring they will stay in place.
- Manufacturing efficiency – PCBs are more cost-effective than other connectivity methods when mass quantities are needed.
- Reliable operation – the design of the PCB ensures steady operation, as the connections are made via copper tracks that will not come loose.
What color are circuit boards?
It may seem like it’s the substrate that gives the PCB the color, but it’s actually the solder mask. The substrate will typically be green, but the solder mask that goes over it can be blue, yellow, orange, purple, red, black, white, or of course, green.
Does the color of the PCB matter?
However, if you’re working with illumination, choosing a white surface of the PCB can help reflect the light. In certain instances, this additional control provides a wider selection of LEDs to choose from in optimizing your design.
Depending on the application, there may be a time when you want to reflect the light. In those applications, a white PCB is ideal.
A white PCB is commonly used for LED light engines or LED illumination systems.
The color of the substrate is just one factor to consider during the schematic phase of your PCB design.
What does the PCB design service process look like?
PCB Design for Assembly is a multi-step process, which can vary in complexity due to the requirements of the device:
PCB Design for Assembly Process
Custom Design or Concept Review of the PCB Assembly
If the customer needs a custom design for the PCBA, our experienced team will ask all the right questions up front to develop the ideal solution. Then test, validate and prototype the design.
Or, if there is already a PCBA design in place, we can ensure all designs and ideas are checked for accuracy and manufacturability before moving into assembly.
VCC’s highly trained engineers can conduct an in-depth review of the design to help minimize delays and maximize yield.
Electronic schematic creation
All logical connections between the PCB components within the circuit are laid out, and the electrical connections between each component are identified.
Once the components are identified, a bill of materials (BOM) can be initiated to secure the appropriate components for the device.
Printed circuit board layout design
It includes the tracing and placing of all components, including the copper tracks and hole layout. Once this information is finalized, a Gerber file is generated, which acts as an industry standard to communicate PCB specs with manufacturers.
Final Bill of Materials (BOM)
Often generated by the schematic design software, the BOM includes:
- All part numbers needed
- Component locations on the board
- Design specifications and limitations
- Quantities of each component
Prototyping the PCB
Prototyping only the printed circuit board (PCB)
Gerber files are used to create prototypes in two ways, depending on the design:
Simple designs – a two-layer, copper PCB prototype is developed without any of the electronic components attached.
Complex designs – additional materials are added to the copper PCB to create a rapid prototype used for design validation.
Prototyping the board + electronic components (the PCBA)
To prototype the fully assembled PCBA, each component on the PCB must be soldered to the board. Designs can include surface-mount components, through-hole components, or a combination of the two.
Using a combination of automated and manual processes, a prototype is created to validate the design as a fully assembled PCBA.
- By hand – any aspect of the process that cannot be automated is soldered manually
- SMT machine – used to apply solder to a high volume of surface-mount components
- Wave solder – Used to “solder” through-hole components to a PCB
For more complex designs, additional materials are used to create rapid prototypes used for design validation.
Evaluate Prototype
The next step is to test the custom prototype PCB in an engineering lab. Chances are, it won’t be perfect the first time. Your manufacturing team will continue to test, evaluate and optimize the design until it is ready to be programmed and brought to life.
Installing Firmware/Programming the Prototypes
If the electronic circuit has programmable components such as microcontrollers and FPGAs, VCC will upload the firmware to the prototype.
Our team will present the prototype with installed firmware to the customer for approval.
Of course, not all PCB assemblies require firmware. If that’s the case, we skip this step and move into full production.
Material Preparation
To minimize delays, VCC orders all materials upfront. This includes the PCBs as well as any other necessary components listed on the BOM.
We also provide customers with an optional production part approval process (PPAP) report or first article inspection (FIA) report for design verification and documentation of each component and its properties.
Full Assembly
After the custom PCB prototype has been approved, any necessary components have been ordered and programmed, it’s time to move into full-scale PCB assembly.
Machines used include:
- Automated solder paste machine – a specialized printer used to create the design which becomes the foundation of the substrate
- SMT pick and place – for fast, automated placement of surface-mount components
- Wave solder machine – used to quickly apply solder and seal the connections in place
This extensive assembly process is made up of the following:
1. Soldering the Components to the PCB
Depending on the design, there may be SMT, through-hole, or a combination of both technologies on the PCB assembly.
For SMTs, the process looks like this:
- Apply solder paste stencil with solder printer
- Attached pick and place SMT component
- Perform reflow soldering
- Flip PCBA over
- Add solder paste to other side
- Attach additional SMD component
- Perform reflow soldering
- Flip back over
- Add through-hole components (if applicable)
- Wash PCBA (optional)
For through-hole technology, the process is much simpler:
- Attach component to PCB
- Use wave solder machine
- Conduct heat curing
- Wash PCBA (optional)
2. Installation of Firmware
Our team of skilled specialists will apply the firmware to your PCBs in the exact specifications approved in the prototype.
3. Quality Control (QC) / Visual Inspection
A visual inspection for quality control allows the manufacturer to detect any errors or defects as early in the production process as possible. Then, those errors are corrected or the PCB assemblies are discarded.
4. Automated Visual Inspection (AOI)
To further investigate any potential defects, an automated visual inspection is used to test the PCB assemblies. With this method, a camera scans the PCBA and reports any abnormalities.
5. PCBA Wash (optional)
Depending on the application, cleaning the PCBAs is not always necessary. It requires additional time and money to add this extra step to production, so it may need to be justified. PCBA cleaning can remove resin and flux residues as well as any residues or contaminants created during production and handling. While it isn’t required, a PCBA wash can provide many benefits:
- Improved aesthetics
- Enhanced reliability
- Protection from corrosion
- Eliminate adhesion problems if using conformal coating
6. Conformal Coating (optional)
Conformal coating is a non-conductive chemical applied to PCBs to protect them from contamination, moisture, salt spray, fungus, dust or corrosion when the devices are used in extreme conditions, or underwater. Not all assemblies will need this protective coating.
7. Electrical Test
The final manufacturing step is to perform a functional test (FCT). Simulating performance in an operating environment, this pass/fail evaluation of the finished PCBs ensures only quality assemblies leave our warehouse
Packaging, Shipping, and Delivery
The last phase of production is just as important as the first. Once our PCB assemblies pass through quality and functional testing, we carefully package and ship the order for on-time delivery. And because we are headquartered in San Diego, we can FCA without you having to import.
Have questions about PCBAs? Browse FAQs
How long does it take to design and produce a custom PCB?
The turnaround time for a custom PCB will depend on the supplier you choose, as well as the complexity and quantity of your project.
At VCC, our in-house PCB capabilities start at design and end at final completion, allowing us to deliver turnarounds in as little as four weeks.
Dedicated warehouse space and advanced tools like a 3D printer empower our team to provide rapid prototyping and expedite the process.
What to Look for in Printed Circuit Board Assemblies Suppliers
Not all PCB assembly partners are the same. To make sure your boards stack up, ensure your vendor provides:
- PCB assembly, all in one place – one central point of contact for everything from concept and design to final assembly, including:
- Preliminary design and layout
- Prototype development
- Manufacturing integration
- Production
- North American manufacturing – facilities close to home can cut down on product lead times, as well as shipping and production costs.
- In-house capabilities – if your PCB manufacturer is sending your work out, you are likely paying more in time and production costs. Find a one-stop-shop with the core capabilities to handle every aspect of your PCB assembly, including surface mount technology and 3D printing for expedited prototyping and production.
- Stringent quality control processes – don’t take a chance on quality. See proof and documentation of testing and regulatory compliance, including ROHS.
- Proven track record – make sure your PCBA partner has an outstanding on-time delivery so you get your components when you need them, every time.
- UL Certification – last, but not least, look for your PCB supplier’s UL Certification to ensure your PCB has been tested to meet fire safety standards using the UL94 flammability rating and UL796 standard for PCBs specifically.
- RoHS compliance – product-level adherence to the European Union’s Directive of the use of certain hazardous substances in electrical and electronic equipment (“RoHS”) may also be required. Our team provides documentation of RoHS compliance, as well as any other regulatory requirements.
Does UL Certification for PCBAs Matter?
UL Certification and the UL mark are invaluable for manufacturers and consumers. Certification is earned only after a series of stringent safety and performance tests.
For customers:
- Identifying which manufacturers’ processes and products meet UL’s strict standards is as simple as looking for the mark.
- Only UL-certified suppliers can provide components for a UL-listed finished product, ensuring all key parts were made with the same quality and safety requirements.
- If maintenance or repair is ever needed, the UL certification helps source the appropriate parts for safe, reliable performance.
For manufacturers:
- UL certification is the perfect way to substantiate claims of quality, safety, and performance.
- Obtaining a UL certification allows the manufacturer’s PCBA products to be sold worldwide.
- Rigorous third-party testing helps improve processes and products.
VCC is UL Rated for PCBA manufacturing. Our certificate number is: E520330. All of our PCBA components use substrates and other materials that meet UL requirements. If you have specific questions or additional design requirements, please contact our team.
Advanced Equipment Drives Better Outcomes
We combine the latest manual and automated techniques to ensure you get exactly what you need. But our advanced equipment and processes aren’t the only reasons to work with us.
■ Solder Paste Application
■ Automated Pick and Place Machines
■ Automatic Dispensing Carts
■ 8-Zone SMT Solder Reflow Ovens
■ Automatic Wave and Soldering Machine
■ Advanced PCB and Stencil Cleaning Machine
■ Advanced ESD Control System
■ Conformal Coating Equipment
■ Visual Scanning Microscopes
■ Visual Camera for Quality Check
Custom PCBAs Real-World Applications
Custom PCBAs are ideal for a variety of industries and applications, including:
- Automotive and aerospace
- Food service
- Medical devices
- Industrial machinery
- Infrastructure
- Consumer products
Here are a few examples of custom printed circuit board assemblies (PCBAs) we’ve created for clients around the globe.
In-theater Food Service: Custom PCBA Design and Prototyping
To help moviegoers indulge in popcorn and other treats without missing any of the action, VCC created an innovative indication solution for the in-seat call button.
The client’s previous indicator created hot spots and light loss, ensuring a performance that didn’t receive rave reviews.
Our team designed, prototyped, and perfected a small light engine with eight SMTs to accommodate the client’s needs. And we did it all in only three weeks.
Now, the call button doesn’t distract from the main action happening on-screen.
In-seat theater food service
It’s light engine, for the win.
Non-Surgical Medical Equipment: From Component Requirement to Comprehensive PCBA Solution
When a leading non-surgical medical device OEM approached us with a design project, all the client wanted was a custom light pipe to better showcase its complex and unique logo on a piece of equipment.
By digging deeper and understanding the challenge at hand, our team quickly developed a custom PCB assembly that reused the existing tooling and delivered brighter, more uniform illumination and production efficiencies.
Streamlined + More-Efficient PCBA
Our team worked within many constraints to deliver innovation and cost savings.
Commercial Dryer Design: PCB Assembly That’s One Heck of an LED Retrofit
Alliance Laundry Systems approached us to retrofit indicators on a range of commercial dryer models from incandescents to energy-saving LEDs without a design overhaul. Due to the footprint of the existing design, our team had to customize a heat sink to offset the high-heat operation of the dryers.
We developed a solution that included a mechanical barrier between the PCB and the edge of the dryer drum. With two options — one for 120VAC and one for 240VAC, we improved the aesthetics of the dryers while ramping up operating efficiency by over 1,000%
Instead of an upgraded dryer light, the OEM got a custom and fully wired PCBA module ready to go out of the package. The new design and packaging reduced installation times by 1/3!
Innovation + Installation Speed
We designed a high-voltage PCBA to retrofit 118 retail dryer models.
Traffic Infrastructure: Seamless PCBA Production After Sudden Loss of Supplier
Before the rest of the world experienced covid-related supply chain breakdowns, one infrastructure industry OEM found itself scrambling when a key supplier disappeared without warning.
In less than a week, our team toured the facility, completed all onboarding, and had a plan in place for turnkey PCB assembly manufacturing, quality assurance, testing, and logistics.
The manufacturer was up and running in no time in our advanced North American production facility.
High-Quality PCBA Manufacturing, Fast
Our North American production facilities and expertise helped one OEM avoid a shutdown.
Lighting for Patient Rooms at Hospitals: Component-Level PCBA Customization
Being a patient in a hospital is hard enough without harsh downlighting. The VCC team worked closely with our client to develop a custom transistor assembly that would enhance the patient experience while minimizing energy consumption.
The over-molded circuit board and photocell unit also had to withstand harsh hospital conditions.
We designed and prototyped a custom circuit board and photocell unit, then designed and shipped the custom product in only 12 weeks.
Lighting that facilitates healing
VCC created the ideal custom assembly on an accelerated timeline.
Slight Product Modifications Deliver Ideal Solutions
Sometimes, you don’t need a fully-customized solution to get exactly what you need. Look for a PCB supplier that can create component-level modifications for existing LED products
For example, we’ve helped clients in the farming, heavy machinery and security industries modify our existing panel mount indicators to:
- The transition from single color to bi-color indication
- Update the lens color
- Upgrading from a single color to a tri-color option
- Change voltage options
PCB Terminology: Definitions You Can Use
There’s a lot more to PCB design terminology than PCB vs. PCBA. Here’s key PCB terminology to become familiar with:
Double-sided PCB: also known as a two-layer PCB, a double-sided PCB features components for connectivity on both sides.
Flexible PCB: a flexible printed circuit board is designed to move and bend to accommodate the design of the device. Flexible PCBs provide OEMs with more compact, lightweight and customizable solutions to suit their needs.
FPGA: a field-programmable gate array (FPGA) is an integrated circuit that can be programmed to execute one or more operations.
FR4: low-cost printed circuit board material commonly used for the substrate layer. FR4 is made from fiberglass cloth that has been embedded in epoxy resin. The term FR4 is a type of substrate, and also the rating used grade epoxy laminate sheets.
Gerber File: computer-aided manufacturing (CAM) file used to provide an industry standard for communicating board specifications with multiple manufacturers.
Light engine: similar to a PCBA, a light engine is a small board that contains a combination of LED modules and an LED driver.
Multi-layer PCB: a board that features more than two conductive metal layers. Multi-layer PCBs enable a range of interconnections ideal for many applications and industries.
Pad: the connection point for the electronic component terminal in the PCB. Components are soldered to the pad.
Rigid PCB: the opposite of a flexible PCB, a rigid circuit board made of a solid substrate material such as metal or FR4 that can not bend. Depending on the design of the device, rigid PCBs can be the most cost-effective solution for mass production.
Single-sided PCB: a simple board with electronic connections on one side.
SMT Pick and Place Machine: High-speed, automated equipment used to place surface-mount technology (SMT) devices onto a printed circuit board. These machines are highly precise and efficient, helping reduce the costs of PCB production.
Solder Paste Printing: using a printer and a stencil, solder paste is applied to a PCB and baked in an oven to seal the bond.
Substrate: the material used to create the foundation of the PCB. This base material is usually made of fiberglass, but can also be comprised of epoxy, metal, ceramic or other materials. The material selection of the substrate is dictated by the primary function and design of the PCB and its components.
Stencils: used to aid the application of solder paste to surface mount (SMT) component pads during the printed circuit board assembly (PCBA).
Wave Solder Machine: wave soldering is a bulk soldering process used in the manufacture of printed circuit boards. The wave solder machines move each board into a pan where a wave of melted solder covers it, bonding all the components of the board together.
Stay Ahead of the Competition with Custom PCB Assembly
The right PCBA partner can help you:
- Get to market faster
- Save on overall production and installation costs
- Streamline the whole process — from design to assembly
- Shrink design and development timelines
- Deliver high-quality, reliable devices
- Reduce the number of vendors required
We have a dedicated team and best-in-class technology to deliver low-cost, high-quality design, fabrication and PCB assembly from a single source.
PCB Assembly Partner
VCC can customize your components with full PCBA design and production capabilities — right here in North America
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