The printed circuit board is the long-form for PCB. The PCBs are ergonomically designed boards that are usually used as the base in electronics. The boards are commonly constructed out of composite epoxy or fiberglass.
Today, we are surrounded by electronic devices, which have become an integral part of our lives. Our phones, cars, and computers are all infused with electronic components. But within these components, lies a PCB.
PCBs are easily recognizable. They're tiny green chips carefully covered in copper parts and lines, located at the heart of electronic gadgets. The copper lines, which are made of fiberglass, are held together with a solder paste- which gives it the green color.
The Simple PCB Basics
The printed circuit board assembly(PCBA) process is sensitive and consists of several manual and automated steps. And for the circuit to be complete, several alternating layers are put together for the full functionality of the electronic device.
These layers include:
Copper ? Copper layer is added on both sides of the PCB if it's double-sided and on one side if it's single-sided.
Substrate ? The base fabric gives PCB its firmness. It protects the board from breaking for added durability and functionality.
Solder paste ? a solder mask is added on top of the copper layer to give the PCB its green color. The mask insulates the copper and prevents it from being in contact with other conductive fabrics. Any contact with conductive materials can result in a short.
Silkscreen ? Basically, this is the final and top layer on the PCB board. It forms the symbols and character on the board, which helps in indicating the functionality of every component. This prevents confusion and errors.
PCB Assembly Process
The PCB assembly is a long, critical process that involves a myriad of manual and automated steps. There are three crucial technologies used in the PCB assembly process. They are:
1. THT (Through-Hole Technology) Assembly Process
THT involves PTH components getting inserted through holes punctured into the PCBs. The leads are attached to the pads with a molten solder on the opposite side. This is the through-hole assembly process.
This technique replaced conventional processes like point-to-point construction.
The THT involves three essential steps which include:
Placement of Components
This is a manual process that is explicitly done by professional engineers. The components are required to be placed precisely and quickly on the corresponding positions. This can only be done by highly trained experts to avoid errors.
The process is required to adhere to operational standards and regulations of the THT mounting process to get an excellent end product.
After the completion of component placements, the PCB board will get inspected to determine if the components were accurately positioned. The inspection will help to determine if there are faults and get them rectified instantly.
Once the inspection is done and every component is accurately positioned, they will be soldered on the circuit board. In this process, the board will move slowly over a liquid solder at approximately 500?F.
2. SMT (Surface Mount Technology) Assembly Process
In this process, the circuits are directly placed on the surface of PCBs using a solder paste. The components are typically smaller compared to THT counterparts because SMDs have tiny or no leads at all.
The process takes place in 3 critical stages, namely:
This is where the paste is applied on the PCB board via a solder paste printer.
The components are placed on the board through reels. These reels are designed to rotate to ensure the parts are quickly sticking onto the board.
In some processes, the mounting machines add minute dots to hold the component tightly on the board. But in this process, repair of the devices becomes a taxing affair.
It?s an automated process that is quite efficient will few or no errors at all.
Once the components are positioned accurately, the board will pass through a furnace at 500?F. It ensures the solder paste is heated and melted down to form sturdy joints between the board and the components.
the major concern in this process is that parts are expected to withstand high temperatures for an extended period then it's needed in manual or wave soldering
The process is accomplished through a reflow oven that helps the components get hold firmly on the board.
SMT has a high automation degree which a myriad of benefits like;
? Reduction of the overall cost
? Minimize human error
? High-quality end products
? Ideal for mass production
Some of the industries that utilize this automation process include aviation, wireless, telecommunication, and automotive.
Any board that goes through a reflow cycle is sent of an inspection. The X-Rays inspection gives a clear image of the solder joints for quantitative analysis. The inspection detects any issues on the board and also helps in determining the root cause of any error.
3. Mixed Technology
Due to much evolution in technology, electronic devices are becoming complicated day by day. It, therefore, means these products require sophisticated PCB boards.
It?s increasingly becoming impossible for PCBs assembled in a single process to perform multifaceted tasks. As a result, mixed technology is the only viable solution.
Mixed technology is a combination of THT and SMT assembly processes to form a sturdy, reliable PCB.
The PCB assembly can either be manual or automated or the combination of both. And since human is to err, there might have error occurred in the process. It's, therefore, prudent to test the electronic devices before dispatching them to the consumers.
Reliable manufacturers use various test and measurement methods to ensure the end products are of high-quality.
Typically, the PCB assembly process is loaded with complicated processes and stages, but it has been simplified in this overview. The assembly and production processes of PCBs are highly optimized to ensure there are few or no defects. The result is having durable and functional devices.