Process Spotlight: PCBA (Printed Circuit Board Assembly)

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PCBA is an acronym that stands for ‘Printed Circuit Board Assembly’. This of course refers to the process of assembling circuit boards that are intended to be used in hardware products, and that provide those devices with their more advanced functionality.

PCB assembly has become an increasingly crucial for hardware startups as more and more products become ‘smart’. As electronic components become more and more affordable and the competition adds more and more functionality to their devices, it’s increasingly important to learn this process. 

How PCB Assembly Works

PCB assembly is a multi-step process that relies on SMT (surface mount technology) and through hole technology. The printed part of the term ‘printed circuit board’ refers to the way that the pathways or ‘traces’ between components are added to the board. This will usually be accomplished by laminating copper sheets onto a non-conductive substrate (a popular choice being wood). From here, the unwanted metal is then etched away to reveal the lines between the circuits boards, ‘like freeways’ in the words of Jeff Bridges. This is not normally done manually, but rather by a computer that will refer to a digital file.

These traces are what will connect the different components once they are added, and this is where the surface mount technology comes in. Surface mount technology is a method that involves placing the components directly onto the surface of the circuit boards themselves. This is as opposed to having lots of wires inside your product that might risk getting tangled up or damaged. SMT allows products to be smaller, and streamlines the process of creating the circuit boards.

An alternative process meanwhile, is through-hole technology. Here, the components use leads that are inserted into holes drilled into the PCBs. These are then soldered onto pads that are on the opposite side. This process can be accomplished manually or by insertion mount machines. This is normally accomplished by using boards that have holes in them already, allowing components with axial or radial leads to easily be added. Choosing between axial or radial leads influences the orientation of the components – with axial leads allowing for a flatter fit with the component ‘lying down’. Because the soldering occurs on the other side of the board in through-hole technology, this can reduce some bleed that might impact negatively on performance.

Soldering

Getting soldering right is one of the big challenges of using a printed circuit board. Prior to soldering, it’s important to use solder paste in the areas where the components are going to be placed. These are what will become the component pads and will be created with a solder screen. This paste is made from small grains of solder mixed with flux and helps to ensure that components end up in the right place.

This step is followed by ‘pick and place’ where the PCBA is automated. This is so named as that’s exactly what will be happening – a machine will ‘pick up’ each component and then drop it into place in the correct position on the board, once again referring to files that were created in the design stage. Soldering does not occur at this point, though in some cases the machine will add a small amount of glue to keep the components in place. The solder paste will also help to this end.

The next stage of assembly is soldering. This can be accomplished either manually or through a soldering machine. Where soldering does not occur manually, it is usually recommended that there be an inspection process which can also be handled by a machine using optical inspection techniques. This doesn’t only look for poor soldering, but also for misplaced components and other errors. Having such a system in place is important for quality assurance. Products will then normally be tested before being packaged and shipped. Here is a rundown of the steps in more detail.

Conclusion

PCBA allows for electronic circuits to be printed and mounted in large quantities for use in a range of products. This is what has enabled much of our current age of smart tech, and makes it possible for small startups and businesses to get in on the act without high up-front costs.

If you’ll be outsourcing your PCBA to a company like Berkeley Sourcing Group we can help you understand the process in more detail. Nevertheless, it pays to have an idea of what is going on as this can help you to produce the appropriate files and documents, to consider the placement of boards and components in your design, and to choose between options like SMT and through-hole technology.

If you’ve had any experiences with PCBA then we’d love to hear about them in the comments. What are any benefits and drawbacks? What kind of tech benefits most from them? As always, subscribe if you want to learn about all the relevant manufacturing processes and techniques available to hardware startups!