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How is the PCB assembly process carried out?
Every electronic device contains a printed circuit board (PCB). The PCB serves as the foundation for mounting various small electrical components. The process of mounting components onto the PCB, followed by inspection and testing, is known as PCB assembly or PCBA.
Every electronic device contains a printed circuit board (PCB). The PCB serves as the foundation for mounting various small electrical components. The process of mounting components onto the PCB, followed by inspection and testing, is known as PCB assembly or PCBA.
As electronic technology advances, so does the demand for more functionality. Consequently, PCBs and components are becoming smaller and more complex. Simultaneously, PCB assembly has become a more critical step in electronics manufacturing. Even a small assembly error can lead to poor on-site performance or failure of the electronic device.
Given the importance of this step, it is crucial for Original Equipment Manufacturers (OEMs) to partner with knowledgeable companies.
PCB Assembly Techniques
Over the years, many different techniques have been developed to attach components to a PCB. Some techniques are more automated than others. Two main techniques used are surface mount and through-hole.
Surface Mount Technology
As the name suggests, Surface Mount Technology (SMT) involves mounting components directly onto the surface of the PCB. Specialized solder paste is used to attach the components. SMT is a widely used system in PCBA. It does not require holes to be drilled in the board.
Using this method, components can be mounted on both sides of the board. Compared to other methods, this allows for more components to be mounted on a given board, resulting in smaller PCBs.
Through-Hole Technology
Through-hole technology (THT) involves inserting component leads through pre-drilled holes in the circuit board. This method is an older approach to assembling PCBs and is less popular than SMT. Nevertheless, it is known for its reliability and strong connections. In some cases, this means the PCB can withstand greater vibration and stress than boards assembled using SMT.
How is the PCB Assembly Process Carried Out?
The steps and sequence involved in the PCBA process may vary slightly depending on the technology used. However, the following outlines the key elements of any PCBA process.
1. Solder Paste Application
One step in PCBA is applying solder paste to the PCB where components will be mounted. The paste used is a mixture of solder and flux. This allows for the permanent attachment of parts to the board in subsequent steps.
Many PCB assemblies use stencils to guide the solder paste. This ensures the paste is dispensed in the correct amount to the correct areas of the board.
We design custom stencils for each PCBA we manufacture. This helps to make this step as efficient as possible.
2. Component Placement
The next step is to place the necessary components on top of the solder paste. This step is known in the industry as "pick and place".
There are many different types of components depending on the functionality of the PCB. Common ones are resistors, capacitors, inductors, and sensors. This step can be done manually or automatically.
But either way, the correct components must be placed in their designated locations on the board.
3. Soldering
The soldering step permanently bonds the components to the PCB. In this phase, SMT PCBA processes typically use a reflow oven and conveyor system. The reflow oven melts the solder paste, while the conveyor moves the board through.
With THT, component leads pass through existing holes and are attached on the other side. For this style of PCB, manufacturers typically use a wave soldering method. This soldering method uses a wave of molten solder to bond the board. The solder flows across the bottom of the board, securing the components in place.
In both cases, the molten solder joins the components and connects them to the board. The components then cool, solidifying the solder and securing the components in place.
4. Component Inspection
This phase of the PCBA assembly process is critical. Inspection is needed to verify the preceding steps. This phase may require manual, automated, and X-ray techniques to help improve inspection efficiency.
5. Testing
The final step in the PCB assembly process is testing to ensure the PCB functions as designed.
Testing methods vary, such as flying probe testing, in-circuit testing, etc. We explore the different testing techniques used in PCBA in our article, "In-Depth Exploration of PCBA Testing".
Once the PCBA passes testing, the component assembly process is complete.
PCBA Expertise
PCB assembly is one of our core competencies. We provide reliable, seamless assembly of high-precision printed circuit board systems.
Our electronics assembly expertise includes:
Surface Mount Technology (fine pitch, BGA (1mm), µBGA (.4mm), 01005, X-ray, automated rework, and Automated Optical Inspection (AOI);
Tray to tray handling;
Smart shelf floor stock control;
X-ray reel counting;
Lead automated insertion (axial, radial, DIP, and Zierick terminals);
Wave soldering and selective soldering machines (no-clean and water-soluble flux processes) RoHS and tin/lead capabilities;
Specialized application equipment (collaborative robot dispensing system);
Conformal coating (silicone, polyurethane);
Potting (epoxy, polyurethane, and silicone);
Low-pressure molding techniques;
Comprehensive product testing;
3D printing.
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