Blog  /  PCBA: A PCB with Electronic Components

PCBA: A PCB with Electronic Components

PCBs are crucial parts of electronic circuits because they hold and provide all the electrical connections between different components. Although some people use PCB and PCBA interchangeably, the two do not mean the same thing.

In simple terms, a Printed Circuit Board Assembly builds on a PCB and forms a complete circuit with all the components. We will look at the PCBA in detail below, including how it differs from a PCB. Take a look!

 

PCB vs. PCBA: What is the Difference

 

A PCB is a blank board consisting of conductive copper pathways sandwiched in fiberglass or epoxy laminate material (base material). It forms the mechanical foundation to mount various electrical components for your circuit.

 

A PCB

A PCB

 

When you fit in the electrical components by soldering them to the contact fingers on the outer edge of a PCB, the outcome is a PCB assembly. Therefore, a PCBA is a PCB that has gone through the assembly process. In simple terms, it is a complete electronic assembly.

 

A PCBA with capacitors, resistors, and integrated circuits mounted on the PCB

A PCBA with capacitors, resistors, and integrated circuits mounted on the PCB

 

Differences Between PCBAs: THT Assembly, SMT Assembly, and Mixed Technology

 

Although all PCBAs are the same, there are some differences in the assembly process, and there are three ways to do it.

 

Thru-Hole Technology

 

Thru-Hole Technology is a traditional assembly process that involves manual and automatic procedures to mount the components.

The process requires drilling holes into the PCB and comes in handy when installing parts with leads that need plugging into the board. These include coils, capacitors, and the like.

 

A thru-hole mounted component

A thru-hole mounted component

Source: Wikimedia Commons

 

Even though the process is old, it creates a stronger bond between the board and its components. THT assembly has four steps:

  • Hole drilling
  • Component placement
  • Inspection and rectification
  • Wave soldering

 

Surface Mount Technology

 

As the name suggests, Surface Mount Technology involves fixing the electronic components on the surface of the PCB. It is a fully automatic and flexible process that makes it possible to have higher assembly densities because manufacturers can fit complex circuitries into small boards.

 

Surface-mounted components

Surface-mounted components

 

SMT assembly has four steps:

  • Solder paste printing
  • Component placement
  • Reflow soldering
  • Inspection

 

Mixed Technology

 

With advancements in science and technology, circuits have become increasingly complex, so having only one component type is impossible.

Therefore, modern electronic products usually have PCBAs with both Thru-hole components (THC) and surface mount device (SMD) components. These components include a mix of capacitors, integrated circuits, coils, resistors, etc.

 

Assembly Types of PCBA

 

Since surface mount technology is a more practical assembly technique than THT, assembly services usually implement SMD only or a mix of the two.

Assembly Types of PCBA

PCBA Process

 

Step 1: Solder Paste Stencil

 

This process is like screen-printing a t-shirt, and it prepares the board for soldering by applying solder paste to the exact places in the right quantities. The screen, in this case, is a thin stainless steel stencil that enables assemblers to place the paste at the right spots.

 

A stencil for soldering chips

A stencil for soldering chips

 

The soldering paste consists of tiny grey balls of metal that are 96.5% tin, 3% silver, and 0.5% copper. Application and spreading of the paste happen in an assembly line, so everything is automated.

 

Step 2: Pick and Place

 

With the solder paste in place, the next step is picking and placing SMD using a robotic machine. Traditionally, assembly experts used to pick and place SMD by hand, but robots automated the process making it faster and more accurate. They set the electronic components over the spots with solder paste applied earlier.

 

Step 3: Reflow Soldering

 

Reflow soldering is a process that solidifies the solder paste to bond the SMD permanently to the board. The board goes into an oven and gets heated at about 250°C or 450°F to melt the solder paste.

 

A reflow oven

Source: Wikimedia Commons

 

Molten solder paste fuses with the SMD, then cools to form a permanent solder joint between the components and the board.

If making a two-sided PCB assembly, the process gets repeated to fit the components on the other side.

 

Step 4: Inspection and Quality Control

 

Poor connections, no connections, or short circuits might occur due to movements in the assembly line, which cause soldering of SMD in the wrong spots. Therefore, checks and tests are necessary before the board moves to the next step.

Checks usually include manual, automatic optical (for larger batches of PCBAs), and X-ray (for complex, layered PCBAs). Malfunctioning PCB assemblies either get discarded or reworked.

 

Vision measuring instrument inspecting PCBA

Vision measuring instrument inspecting PCBA

 

Step 5: Through-Hole Component Insertion

 

If the board has a mixed assembly, the next step is to fit the plated thru-hole components (PTHC). Using soldering paste is not practical for mounting PTHC because the paste would melt right through the drilled holes.

Instead, manufacturers either use manual soldering, a lengthy process done by hand, or wave soldering. The latter is faster because it runs the boards with PTHC inserted over a molten solder wave on a conveyor belt. Liquid solder washes the underside of the PCBs, fusing the components permanently.

 

A wave soldering machine

A wave soldering machine

 

Step 6: Final Inspection and Functional Test

 

The last step is to inspect and test the complete board by checking its electrical characteristics (current, voltage, and signal output). These factors must be within the predetermined range, or else the board gets discarded or recycled.

 

How to Get a Custom PCBA?

 

If you want to get a custom PCBA, these steps will guide you through the process.

 

Step 1: Create a Schematic

 

Using software like CAD (computer-aided design), Eagle, or Multisim, begin designing the PCBA by creating a schematic view. Layout all the required components on a canvas, then join their pins with lines representing the electrical connections.

 

Step 2: Board Layout Check

 

After creating the schematic, check the board layout via the electrical rule check to ensure no evident faults.

 

Step 3: Rearrange Components

 

Next, move the components to the right places that make good sense for the PCBA.

 

Green printed circuit board (PCB) with components. 

Green printed circuit board (PCB) with components. 

 

Step 4: Assign Signals

 

Assign signals to each PCB layer while ensuring varying signals on a single layer don't come into contact.

 

Step 5: Design Check

 

Use the design rule check to check and approve the layout, and if you have a flawless assembly, upload the design files. These are usually multiple Gerber files, one for each layer. Also, generate the drill file, which shows where to drill the holes.

 

A PCBA design file image

A PCBA design file image

Source Wikimedia Commons

 

Step 6: Go to OurPCB and Upload Design Files

 

Compress the files, upload them to OurPCB, fill in your details, specify your needs in the message section, then submit the form.

 

Benefits of PCBA

 

Saves Time

 

Building PCBAs takes significantly less time compared to connecting components using wires.

 

Gives a Compact Design

 

PCBAs pack multiple components in a compact space, resulting in smaller electronic devices.

 

Maximizes Durability

 

Since the design lacks hanging wires that can easily cut, PCBAs create a durable and more reliable electronic component setup.

 

Simplifies Repairs

 

Removing a damaged component and soldering a new one is relatively easy on a board compared to handling wire connections.

 

Affordable

 

PCBAs are cheap to build, which translates to lower costs for your project.

 

Applications of PCBA

 

  • Medical sector
  • Vehicles
  • Electrical equipment
  • Military
  • Aerospace
  • Consumer electronics
  • Safety and security equipment
  • Maritime

 

PCBA Manufacturing Defects and Solutions

 

It is almost impossible not to have manufacturing defects when building PCBAs. These are the most common issues and how to deal with them.

 

Wire Breaks Issue

 

Wire breaks are common in PCB fabrication & assembly, and the only way to deal with them is by doing a thorough inspection.

 

Poor Pin and Connector Placement

 

Pin misplacement can damage the connectors, but you can avoid this by using a pattern-matching tool. It helps to locate and accurately group the patterns for correct pin alignment.

 

Open Solder Joints

 

The separation between the component leads and the PCB, poor soldering, insufficient solder paste, or inconsistent paste use can lead to open joints. To avoid this, use the right PCB design, prevent solder paste contamination, and use the right manufacturing equipment.

 

Solder joints of the modern circuit board

Solder joints of the modern circuit board

 

Component Shift

 

Components usually move when soldering due to several reasons. However, maintaining the correct humidity, melting the paste at the proper temperature range, and minimizing movement can eliminate this problem.

 

Overheating

 

PCB components can get extremely hot when in use. An SMD heat sink can keep the temperature under control, so the board should have one that has undergone a heat dissipation analysis.

 

A computer motherboard heat sink

A computer motherboard heat sink

 

Chemical Fluid Leakage

 

Traces of chemical fluids on the PCBA can significantly corrode the metal parts, so as a manufacturer, you should clean the board thoroughly to ensure no damages.

 

Shorting

 

The only way to eliminate shorting on circuit boards is by separating leads and solders before solidification. Use the required design rules and modify stencils to prevent solder bridging.

 

What To Consider For the Best PCB for PCBA Manufacturer

 

If you find it cheaper and more convenient to outsource PCBA manufacturing, you need to ensure the company:

  • Is the actual PCB manufacturer and assembler, not a broker
  • Knows different PCB assembly techniques
  • Has no limits the minimum/maximum number of orders you can make
  • Offers reasonable and competitive pricing, sometimes negotiable
  • Delivers the PCBA on time and with the DFM (Design for Manufacturability) details

 

Summary

 

All in all, PCBAs are the basic building blocks of most modern electronic circuits because they hold components in a compact, durable structure.

If you need one of these built for your project, contact us to get authentic PCB assemblies at unbeatable and affordable prices.