PCB Assembly Process: 9 Things You Need To Know

Circuit Boards Printed on Paper (PCB)—Assembly processes are the core base for any electrical equipment, including automobiles, cellphones, computers, and gadgets. You have likely encountered a printed circuit board (PCB), which is typically green in colour and has copper wires connecting its numerous components. 

But have you ever considered the assembly process of PCBs? The components, copper layer for the lines, holes for the component installation, and layers (inner and outer layers) make up the printed circuit board (PCB). 

Knowing the different steps involved in the PCB assembly process is essential, regardless of your experience level in electronics. Therefore, you should know several crucial factors while sourcing your PCB. This article covers everything you need to know about multiple factors in the PCB assembly process.

1. Understanding the PCB Assembly Process

Creating the bare board once a designer sends the Gerber files to a manufacturer is known as PCB fabrication. The panel’s substrate, which comprises the insulating material, must be added first. After that, copper is applied to the board and chemically etched away to leave only the essential remnants. Additional steps in the PCB manufacturing process include drilling, plating, and solder mask application.

One component is installed to make the PCB operational and prepare it for your project. The electrical components are attached to the board using various technologies, including human soldering, pick-and-place machines, and surface-mount technology (SMT).

You must choose which technology to use depending on your needs and the electrical components you employ. Several assembly types to take into account while selecting a PCB assembly in the UK are laid down as follows: 

  • Through-hole technology (THT) is a conventional technique that uses parts whose leads are connected on both sides after being introduced via holes in the PCB. 
  • Surface-mount technology (SMT) is a contemporary method for soldering components with flat leads directly onto the PCB surface. 
  • Mixed Technology Assembly (MTA): Mixed Technology Assembly (MTA) provides greater design flexibility by combining THT and SMT components on a single PCB.

2. Timely Communication Is Essential 

The communication will facilitate the PCB assembly services by making it easier for a pick-and-place machine to choose and arrange the components on the PCB. Effective communication is crucial to any function, and the SMT is no exception. It would help if you got what you require from your PCB supplier. Avoid assembling your PCB before familiarising yourself with the requirements. 

Thus, kindly record their preferences and the gadgets you require, especially for the project. Discuss the multiple technologies to determine which ones are appropriate for the assembly. Additionally, you must confirm that your PCB provider can satisfy your customers’ expectations and is aware of your needs. 

3. Avoid Making the Error of Missing the DFM/DFA Check 

Do you want the best possible performance and error-free operation from your PCBs? 

The answer is yes, without a doubt, since no one wants to make a batch of defective PCBs. Doing a DFM or DFA check is one technique to ensure your PCB design and function are accurate. Most PCB assemblers adhere to standards and offer DFM tests for validation. 

By doing a DFM check, you can ensure that the faults in your PCB design are found early on and fixed, avoiding expensive mistakes and assembly delays. DFM is a thorough test that finds electrical component flaws in their footprint.

4. Conduct an Assembly Material Inspection 

The primary step in the PCB assembly process is placing the various components on the board. Alternatively, you might find them on your own. Regardless of your option, it would help to examine the specifics of constructing the PCB. 

Several facets of quality control inspection include date code verification, material functional testing, and other tests to ensure the components are in perfect functioning order. With material reviews, engineers may utilise only high-quality components, prolonging your PCBs’ shelf life. 

Engineers inspect a few things when receiving supplies, including: 

Model and quantity numbers that adhere to the BOM list 

Conducting sample testing with a multimeter, test frame, and other techniques 

Deterioration, oxidation, or broken parts of various components like IC

5. SMT Solder Paste Screening:

The solder paste is pasted to the bare board to start the PCB construction process. You understand the procedure well if you have seen how a silkscreen is used to print a t-shirt. Only the open areas where the SMT components will be attached are covered with solder. 

The procedure must be performed on the opposite side of the board when working with double-sided PCBs. Engineers check the board after soldering to make sure the solder is only put over the designated areas. To ensure enough solder is used to install the components, they will also measure the amount of solder applied to the pads.

6. Surface Mounted Device Selection and Placement in the PCB Assembly Process (SMD) 

Once the solder has been applied, it’s time to locate the SMD components on the cushions. Unlike through-hole devices, SMDs are soldered on the PCB and lack legs and leads. The SMD is the most often utilised non-connector component in PCBs. 

Using tweezers to pick and place each component took a long time and was tiring for engineers in the past. Component placement is now rapid, and with modern technology, you have to programme the machines to choose and arrange SMDs correctly.

7. PCB Assembly Process: Use Reflow Soldering to Secure SMDs 

Now that the SMDs are on the pads, the next step is to ensure they are securely fastened. This means that a procedure known as reflow soldering is required to heat and solidify the solder. Remember that the heat profile associated with this technology prevents it from being applied to many through-hole components. They must be attached by hand soldering or wave soldering. 

Additionally, you must perform stencilling and reflowing independently on each side of double-sided PCBs. Start by tending to the side with fewer and smaller components, then go on to the other side.

8. The PCB Assembly Process: X-Ray Inspection Time 

Following reflow soldering, an X-ray inspection is performed to find faults and other issues. It is also used in manufacturing for bare boards and pre-flow soldering inspection. 

By flowing through the silicone of the SMDs and bouncing off the metal in the solder, the X-rays produce a digital representation of the solder connections. To analyse the photos, you can use image processing software. 

9. Final Inspection and Wrap-Up of the PCB Assembly Process 

To ensure that clients never have an opportunity to voice complaints, a trustworthy PCB assembler will always strive to deliver the best artistic quality! Many PCB businesses use X-ray and final tests to guarantee flawless and error-free PCBs.

In conclusion, the PCB assembly process transforms a blank board into a working marvel. Knowing each step gives you the ability to get around in this world. By learning about factors like design optimisation and selecting the appropriate partner for PCB assembly in the UK, you can guarantee a seamless and fruitful conversion from idea to reality. Collaborative efforts, quality focus, and clear communication facilitate a practical electronics project.

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