How Consumer PCB Assembly Is Done

How Consumer PCB Assembly Is Done

Printed circuit boards (PCBs) are found in nearly every type of consumer electronics device from smartphones to laptops, and video gaming consoles, making consumer PCB assembly a vital part of the manufacturing process. Let’s briefly dive into what makes consumer PCBs so important to the consumer electronics industry, and explore how the consumer electronics PCB assembly process is carried out. 

The Importance Of Printed Circuit Boards In Consumer Electronics

Examples Of Consumer Electronics Products That Require Printed Circuit Boards (PCBs) To Function | INQUIVIX TECHNOLOGIES
Examples Of Consumer Electronics Products That Require Printed Circuit Boards (PCBs) To Function

The worldwide market for consumer electronics products is mind-boggling, with people estimated to have spent over US $500 billion in the year 2022 on such devices according to Statista Market Research. The most popular consumer electronic devices are mobile phones, followed by laptops and desktop computers, tablet devices, smartwatches and wristbands, gaming consoles, televisions, and other smart home devices. Making these devices work is a consumer electronics PCB at the heart of them.  

Modern circuit boards provide the medium that device manufacturers use to connect the various electronic components in a tightly controlled and standardized way. This is what enables the mass production of these electronic devices across multiple assembly lines, in many different factories around the globe.    

Consumer Spending On Technology Worldwide (2020 - 2022) | INQUIVIX TECHNOLOGIES
Consumer Spending On Technology Worldwide (2020 – 2022)

Apart from the massive demand, there are also new types of consumer electronics products such as virtual reality goggles, wearable technology, smart home appliances, smart vehicle technology, and more. This means that the consumer electronics industry has to receive a steady supply of high-quality PCBs from PCB assembly service providers to meet the growing demand. 

Furthermore, the PCB assembly services providers need to develop advanced technological equipment and more efficient PCB assembly methods to produce premium quality boards that power the latest trends in consumer electronic devices of tomorrow. To learn more about the history of circuit boards, and why they’re used in the manufacture of consumer electronics products, read The Consumer PCB And Why It’s Used For Consumer Electronics Applications

What Is A Consumer Electronics PCB?

A Consumer Electronics PCB

The typical consumer electronics PCB has a sandwich structure of insulating substrate made up of glass epoxy resin composites and conductive copper layers laminated onto the substrate. The copper layers form the circuit pattern or ‘artwork’ as it is commonly called by those working in the consumer electronics PCB assembly business. These copper layers are essentially the wires that carry electrical signals between the PCB components.  

Circuit boards have conductive pads on their outer layers which can accommodate the terminals of components that will be mounted onto the PCB. These components could be transistors, LEDs, resistors, switches, sensors, transformers, and even integrated circuits (microchips) that contain millions of microscopic semiconductor devices inside them. To learn more about semiconductor devices, read The Top 5 Modern Semiconductor Devices For Integrated Circuits

The Consumer Electronics PCB Assembly Process

The PCB assembly sector utilizes software called electronic design automation (EDA) tools to design the printed circuit board layout before the PCB fabrication stage. After designing, EDA tools can even run simulations to check if the PCB components are connected to meet the complex circuit board requirements specified by the device manufacturer. To learn more about EDA tools, read How Advanced Chip Design Is Done Today. Once the design of a consumer electronics PCB is finalized and approved, the PCB assembly process is done in the following steps. 

Manufacture Of The Substrate

The consumer electronics PCB assembly process begins with the making of the substrate material. Woven glass fiber is soaked in epoxy resin by dipping it or spraying it. Once the glass fiber is saturated, it is sent through rollers which set the substrate board to the desired thickness and removes any excess deposits. 

Next, the saturated fiberglass is placed in an oven and heated to increase the strength of the material. Afterward, the hardened material is cut into large panels. Next, these panels are arranged in layers with adhesive-backed copper foil in between them and pressed together. Finally, each copper layer is bonded to the substrate by baking the materials for over an hour at a temperature of about 170°C with 1500 psi pressure.   

Drilling And Plating Of Holes

A finished PCB requires holes to mount the various circuit components like LEDs and integrated circuits. A precisely motion-controlled machine handles the drilling of the holes, according to the specified pattern. Multiple substrate panels can be stacked, positioned, and loaded into this device to be processed simultaneously. After the drilling is done, a deburring process takes place to remove any excess material still clinging to the substrate panels.

The holes are where the terminals of components will connect to the circuit pattern on the PCB. This means they have to be made of conductive materials. A copper coating is applied to the surfaces of the holes to make them conductive. If non-conductive holes need to be present, these are plugged during the plating process or are drilled at a later stage in the PCB assembly process.  

Creating The Circuit Pattern On The Substrate

The Circuit Pattern On A PCB

The next step in the consumer electronics PCB assembly process is to create the circuit pattern on the surface of the substrate. This can be done in an additive process where the copper is coated to the substrate in the desired pattern, or in a subtractive process where the entire substrate is plated with copper, and then the unnecessary areas are etched away.

In the subtractive method, a layer of photoresist material is applied to the surface of the copper-coated panel in a vacuum chamber. The vacuum ensures that no air bubbles get trapped between the copper foil and the photoresist. Next, the panel is exposed to ultraviolet light through a mask that has the same circuit pattern as the desired printed circuit board. 

The pattern mask is removed and the surface of the panels is sprayed with an alkaline solution which will dissolve the UV-irradiated photoresist according to the circuit pattern. The copper foil areas that are now exposed can act as a cathode, while the areas that are still covered by photoresist cannot act as a cathode. This allows copper to be electroplated according to the desired circuit pattern. The thickness of this copper plating is in the 0.025-0.050 mm range. 

Afterward, to prevent any copper oxidation, a shield coating of tin-lead is applied on top of the copper plating. This tin-lead coating also acts as a resistor for the next steps in the consumer electronics PCB assembly process. 

The photoresist is then removed by a solvent, and an acid solution is sprayed to remove unwanted copper foil. The copper plating in the circuit pattern is protected by the tin-lead coating. This tin-lead coating itself is very easily oxidized. This coating is fused into a shiny surface by sending the panels through an oven. This process is called ‘reflow’. 

Sealing, Stenciling, And Cutting Of Circuit Boards

At this stage, each of the panels is sealed using epoxy resin to protect the circuit patterns from being damaged by later steps in the assembly process. Markings and instructions are stenciled before the panels are finally cut into individual circuit boards.  

Component Mounting And Packaging

Surface Mount Components Being Mounted On The PCB | INQUIVIX TECHNOLOGIES
Surface Mount Components Being Mounted On The PCB
Image taken from

After the PCBs are cut and their edges smoothened, they are now ready to be fitted with electronic components like LEDs, switches, and integrated circuits. In the case of surface mount components, the boards are passed through an automated machine that applies a bit of solder paste at each contact point of each component. 

The tiniest circuit components are placed with great precision and speed using a device called a ‘chip shooter’. Components that are too large or oddly shaped are placed manually. Next, the components are soldered to fix them in place. For surface mount components, the soldering is done through another reflow process, which causes the solder paste to melt. 

Water and/or solvents are used to clean any excess residue left over from the soldering process. Next, the assembled PCBs are packaged before being shipped to the consumer electronic device manufacturers who will be using them to build their products. 

Quality Control

Quality control is done at many different stages of the consumer electronics PCB assembly process. One way of doing this is through automated optical inspection (AOI), where a camera scans the board for defects such as missing components, and poorly soldered contacts. The assembled circuit boards can be tested for their functionality through automated test equipment (ATEs). These will insert probes to make contact with the boards, apply a test electrical signal, and compare the output with the specifications to determine if there is any deviation. To learn more about ATEs, read Semiconductor Chip Testing.  

With the consumer electronics industry moving onto more advanced products, the PCB assembly services providers have had to come up with many innovations of their own to supply the ever-growing demands of device manufacturers. High-Density Interconnect PCBs allow even more densely packed boards that are needed for high-performance computing applications like artificial intelligence-based systems. 

The size and weight of the PCBs have been reduced as well to support wearable technology like smartwatches. Advanced materials that improve on the resin-coated copper are also being developed and electrostatic discharge (ESD) protection is being built-in into the substrate. With foldable smartphones now being produced, rigid-flex PCBs have become quite popular as well. 

Finally, with increasing concern for the natural environment, the manufacture of sustainable PCBs is being researched to reduce the use of hazardous substances like lead, mercury, and cadmium. If you wish to learn more about printed circuit boards, integrated circuits, or semiconductor components, visit the Inquivix Technologies Blog today!


What Is The PCB Assembly Process?

It is the manufacturing process where the glass fiber epoxy resin substrate is created, with the copper circuit patterns etched, circuit components mounted, and soldered to produce a working printed circuit board.

 What Are The Different Types Of PCB Assembly?

There are many types of consumer electronics PCB assembly such as single-sided, double-sided, multiple-layer, rigid, flexible, and rigid-flex PCBs,

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