What PCB Assembly Means, Definition, Types, Uses, A Helpful Guide

Did you know that almost every gadget or electronic device you use in your daily life has one basic and integral component in common? Almost any electronic device including your PC, laptop, smartphone, gaming console, microwave, TV, dishwasher, etc. cannot function without a PCB assembly. So then, what is a PCB assembly?

 

What Does PCB Assembly Mean? PCB assembly refers to the process of soldering and assembling electrical components on a pre-formatted and manufactured printed circuit board (PCB). Typically undertaken with specialist production machinery, in mass production, the printed circuit board assembly process is commonly known as PCBA.

 

Difference Between PCB and PCBA

PCB refers to the empty circuit board. In this state, the circuit board does not contain any electronic components and looks like a green slate with demarcated lines and spaces. As such, the PCB itself cannot be used to work a device unless and until the entire assembly is completed.

 

The PCBA, on the other hand, is referred to both the process of soldering and assembling electronic components on a circuit board and the finished/assembled circuit board as well. The finished PCBA is actually used in electronic devices rather than the PCB.

pcb-vs-pcba

What Is a Circuit Board Assembly

Circuit board assembly takes part in various steps. It’s a non-linear process indicating that there are considerations involved, based on which the process can change and adapt. The expected outcome and use of the PCBA is one of the main considerations which dictates the components and general circuit board assembly process.

 

Here are some of the parts and components needed to undertake a PCB assembly:

  • 1. Basic Printed circuit board, or substrate
  • 2. Electronic components which will be fitted into the board. This will vary depending on the use of the board and the complexity of the device. For example, a PCBA for radio is comparatively simpler than that of a computer. In fact, some computers can have as many as 12 different layers of circuits on the PCB.
  • 3. Soldering materials like solder wire, solder bar, paste, preforms. The preforms are dependent on the type of soldering that will be performed.
  • 4. Soldering flux
  • 5. Other soldering pieces of equipment like soldering station, wave soldering machine, inspection, and testing equipment and SMT equipment. The use of the equipment is dependent on the expected outcomes, cost and time resources. For example, the reflow soldering processes used in electronics are mainly Vapor Phase and Infrared. Depending on above-mentioned factors, one of the processes is chosen.

 

When all the necessary components have been readied, it’s time to start the assembly process. But before we move into the assembly process (and it’s different types), let’s understand a bit more about the circuit board itself.

 

Three Main Types of Printed Circuit Board

The circuit board is generally made of epoxy or other composite materials. It’s used to physically support the components, as well as electrically connect them to form a live circuit.

 

In the most simplistic sense, a PCB will consist of a thin sheet of insulating material with a layer of copper foil, jointly laminated to the underlying substrate (usually made of epoxy, fiberglass or similar composite materials). The number of layers on a PCB depends upon the use and application. The lines or circuit tracks on the PCB are created with the help of chemical etching. These lines help with the flow of electricity and connect the various components together.

 

There are different types of circuit boards or PCBs. Depending on the type of application, manufacturers will select the PCB. Here are some of the most widely used types of PCBs:

 

Multilayer PCB

PCBs come in various layers including single sided and double sided. However, single-sided is used by hobbyists due to its limited application spectrum, while double-sided are not generally used in wide scale manufacturing any longer.

 

Multilayer PCBs are more common since they pushed the envelope after double-sided PCBs. There can be numerous layers of substrate boards in such PCBs. The insulating material acts as a mediator and a separator between these boards.

 

The multilayer PCB is designed to save more space than the double-sided. Generally, multilayer boards come in 4, 6, 8, 10-layer options but can be custom-built to have more layers. Such PCBs are found in computers, medical machines, smartphones and servers.

Multi-layer PCB

 

Rigid PCB

PCBs do not only come in varying degrees of layers and side but of rigidities as well. Generally, when talking about PCBs, we are referring to the rigid PCB. These kinds of circuit boards use solid, inflexible substrate materials like fiberglass, epoxy, etc. As a result, the board doesn’t bend easily and offers mechanical support to the components and the device as a whole. A computer’s motherboard is a common example of a rigid PCB.

PCB

Flexible PCB

Flexible PCBs are the direct antithesis to rigid PCBs. As the name suggests, these boards are made with substrate materials that are flexible, such as plastic. The substrate material offers enough flexibility to the board to be fit into various shapes and sizes. However, the flexibility is retained in a way that does not damage circuits on the board.

 

Flex PCBs are usually more expensive to design and manufacture than their rigid counterparts. However, there are a number of advantages like replacing the need for heavy wiring in advanced devices to increase space and reduce weight output. Like rigid PCBs, flex PCBs too may be single-sided, double-sided and multi-layered.

Flex PCB

Metal Core PCB

Metalcore PCB or otherwise known as MCPCB are specialised PCBs that are used for definitive purposes. For example, the LED industry has been developing rapidly, but they hadn’t been able to solve heat dissipation efficiently. Using MCPCB, allows them to resolve this issue.

 

The metal core PCBs are made of a metal plate, copper foil and thermally insulating layer. Altogether, the PCB offers magnetic conductivity, superior heat dissipation, high rigidity as well as high processing power. The base material, in this case, is usually aluminium and copper. However, copper is known to perform better than aluminium and is also more expensive.

 

Type of PCB Summary
Single Side PCB Used in simple systems, Low cost, Common for Hobbyists
Double SIded PCB Less common than Multilayer. Uses both sides of one board
Multilayer PCB Commonly mass produced, Economical, Compact, up to 10 or 12 Layers
Rigid PCB A stronger substrate, High impact applications, Military, Aerospace
Flexible PCB Moving part applications, higher cost, greater longevity
Metal Core PCB Metal plate, copper, speclialist applications, such as conductive or thermal

metal-core pcb

Methods of Mounting Circuit Board Assemblies

The technology used in assembling the circuit board and it’s various components is known as mounting technology in circuit board assemblies. Depending upon the application, cost, scale and other considerations, there are different kinds of mounting methodologies used by manufacturers. Here are some of the most commonly used technologies:

SMT

Surface Mount Assembly

Surface mount assembly (or Surface Mount Technology, also known as SMT) is a method in which the electronic components that are erected on a PCB are joined directly on the surface of the board. The resulting board is called a surface-mount device (SMD). This technology was originally known as ‘planar mounting’.

 

Most of the electronic boards in production today are manufactured using SMT. It has replaced the more traditional through-hole technology (more on that in the next point) due to its increased circuit densities and ability to produce results on smaller circuit boards. Generally, SMT uses solder to joint the components with the board but in some cases, adhesive dots might also be used on the second side to keep the components together inside the reflow ovens.

 

Plate Through Hole Assembly

Through-hole technology (also referred to as “thru-hole”) is a mounting technology, where the electronic components are inserted through holes built into the circuit boards and then soldered to pads on the other side. The soldering can either be by hand or using insertion mount machines.

 

Thru-hole technology replaced the more traditional point-to-point construction. Thru-holes become popular as double-sided and multi-layer boards became more popular. It was used to join the components with the electricity conducive layers to ensure that the board functioned properly. The components are fitted with wire leads which are used to join on the other side of the thru-hole boards.

 

As opposed to SMT methodology, thru-hole technology provides more cohesion to the circuit board components as the units are placed through the board itself.

Electro-Mechanical Assembly

Electro-mechanical assemblies use electrical and mechanical units to cover a wide range of functions such as power generations, controlling switches and other mechanical tasks. Since electro-mechanical assemblies typically are used in applications which have complicated wiring and components, the assemblies need to be manually put together.

 

As a result, it can often be time-consuming. However, a major manufacturer like us here at RayPCB, use this technology and have broken down the process to various segments and use specialists of each segment. Thus we can cut down the lead time.

Common Uses for Each Type of PCB Assembly

Surface mounted technology was most commonly used in personal computers and is still used. It’s one of the most widely used technologies in electronics and has uses across a wide spectrum of consumer electronics including smartphones, computers, TV, microwaves, etc. But before SMT came, it was thru-hole technology that dominated the personal computer market.

 

In fact, it was IBM who pioneered the process and brought it to the mainstream. Currently, thru-hole technology is more used in bulkier assemblies like electrolytic capacitors and semiconductors, since it is capable of holding the components together better than SMT.

 

Electro-mechanical assemblies are typically used in AC and DC power distributions, computer interfaces and control systems due to its versatility in power-enhanced mechanical functions.

DIP

Conclusion

A PCB is a very near and dear part of our contemporary life, even though we remain oblivious to it. Over the decades, the technology of assembling and fitting components efficiently has developed rapidly from point-to-point construction to thru-hole to SMT. Furthermore, each has its own sets of advantages and disadvantages which make them perfectly suited for some task while not so much for others.

 

We produce all these different kinds of PCBs at RayPCB. If you have an idea or a prototype, then it’s only a matter of asking for a quotation or some advice on how to proceed, so get in touch with us today to make your PCBs come to life.