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Printed Circuit Board Assembly (PCBA) – Process, Technology, Tips and Techniques

Printed circuit board assembly, also known as PCBA, is the process of soldering or assembly of electronic components to a PCB or printed circuit board.

Printed circuit board assembly, also known as PCBA, is the process of soldering or assembly of electronic components to a PCB or printed circuit board.

What is PCB Assembly?

A circuit board prior to assembly of electronic components is known as PCB. Once electronic components are soldered, the board is called Printed Circuit Assembly (PCA) or Printed Circuit Board Assembly (PCBA) or PCB Assembly. Different Manual and Automatic PCB Assembly Tools are used in this process.

A PCB Assembly

It has to be noted that assembly of a circuit board is different from PCB Manufacturing Process. Manufacturing printed circuit boards involve several processes including PCB designing and creating PCB prototype. Once a PCB is ready, Active and Passive Electronic Components need to be soldered onto it before it can be used in any electronic equipment or gadget. This assembly of electronic components depends on Type of Printed Circuit Board, type of electronic components and purpose of the circuit board.

Printed Circuit Board Assembly Tools, Equipment and Consumables

Following PCB Assembly Tools, electronics parts and consumables are needed for PCB assembly –

  1. Printed Circuit Board
  2. Basic Electronic components
  3. Soldering materials including solder wire, solder paste, solder bar, solder balls for BGA, solder preforms (depending on the type of soldering to be done)
  4. Soldering flux
  5. Soldering equipment including soldering station, wave soldering machine, SMT equipment, inspection and testing equipment etc.

Once all of the above equipment, electronic parts and all raw materials are arranged, it is time to start the printed circuit board assembly process.

Printed Circuit Board Assembly for Thru-Hole Electronic Components

Electronic components that have leads coming out and are inserted through tiny holes in the PCB for soldering are called thru-hole electronic components.

The assembly or soldering process for these components include wave soldering and hand soldering.

Wave Soldering

A Wave Soldering Machine

A Wave Soldering Machine

Assembly process in which solder in the form of solder bar are put in a high-temperature bath. This solder remains in the bath in molten form and forms a wave at very high temperature. The range of temperature depends on the type of solder. Traditional tin / lead (Sn/Pb) solder has lower melting point than lead-free (Pb-Free) solder. The PCB with all the thru-hole electronic components in holes is passed over molted solder with a help of a conveyor belt.

The whole wave soldering PCB Assembly Process includes following steps:

  1. Inserting of electronic components
  2. Flux application
  3. Preheat
  4. Wave Solder
  5. Cleaning
  6. Testing

Once the wave soldering is done, the PCBA is cleaned and tested. If any fault or solder joint defect such as Pin Hole or Blow Hole Wave Soldering Defect is found, it is sent for rework, which is generally done by hand.

Dip Soldering

A Solder Pot is used for Dip Soldering

A Solder Pot is used for Dip Soldering

In dip soldering, a solder pot with molder solder is used. Simpler PCBs with less components are dipped in the solder post to solder all the thru-hole components all at once.

Hand Soldering

A Soldering Station for Hand Soldering

A Soldering Station for Hand Soldering

Hand Soldering is done in manufacturing units with less work load or in rework / repair jobs. A good quality soldering station or soldering iron and solder wire and flux are used in the process.

Surface Mount Technology (SMT) for Printed Circuit Board Assembly

Surface Mount Technology or SMT is a PCB assembly process for SMD electronic components. SMD components don’t have leads or legs. They are mounted on the surface of the circuit board. The equipment, electronic components and other soldering material used in this assembly process is different from thru-hole soldering process.

Reflow Soldering

A Reflow Soldering Machine

A Reflow Soldering Machine

Reflow soldering is a soldering technique used in electronics manufacturing. It involves applying solder paste to component pads on a circuit board, placing components onto the paste, and then heating the board to melt the solder, creating electrical connections.

Selective Soldering

PCB Assembly Process (Selective Soldering)

PCB Assembly Process (Selective Soldering)

Selective soldering is a soldering process used in electronics manufacturing to selectively apply solder to specific components on a printed circuit board (PCB). This automated technique is employed for components that cannot withstand the heat of traditional wave soldering or reflow soldering processes.

PCB Assembly Process Flow Chart (PCBA Process)

PCB Assembly Process Flow Chart (PCBA Process)

PCB Assembly Process Flow Chart (PCBA Process)

Video: SMT PCB Assembly Process

Turnkey PCB Assembly Service

Bittele Electronics focuses on Full Turnkey services, including PCB Fabrication, Parts Procurement, and PCB Assembly. By choosing their Turnkey PCB service, you can save both time and money.

FAQs: PCB Assembly Process

The main steps in the PCB assembly process include:

  1. Component Placement: Placing electronic components onto the PCB according to the design layout.
  2. Solder Paste Application: Applying solder paste to the board's solder pads, which acts as an adhesive for components.
  3. Reflow Soldering: Subjecting the board to controlled heat to melt the solder paste, forming a secure connection between components and the board.
  4. Inspection and Testing: Checking for proper component alignment and solder quality, followed by functional testing to ensure the circuit's functionality.
  5. Cleaning and Packaging: Removing excess solder flux and contaminants, then packaging the assembled PCB for distribution or further manufacturing.

Automated PCB assembly offers several advantages, including:

  1. Speed and Efficiency: Automation speeds up the assembly process, reducing production time.
  2. Consistency: Automated machines ensure uniform component placement and soldering, minimizing errors.
  3. Higher Precision: Automated systems can handle fine-pitch components and smaller parts with high accuracy.
  4. Labor Savings: Reduced need for manual labor leads to cost savings and potential reduction in human errors.
  5. Complex Designs: Automation allows for the assembly of intricate and densely populated PCBs that may be difficult to assemble manually.

Some common challenges in PCB assembly include:

  1. Soldering Defects: Poor soldering can lead to connections that are weak or faulty.
  2. Component Misalignment: Incorrectly placed components can lead to circuit malfunction.
  3. Quality Control: Ensuring consistent quality across large production facilities requires robust inspection processes.
  4. Temperature Sensitivity: Sensitive components may be damaged during reflow soldering due to high temperatures.
  5. Design Changes: Last-minute design changes can disrupt production schedules and may require reprogramming automated equipment.

Surface finishes are crucial in PCB assembly for ensuring proper solderability and preventing corrosion. Common surface finishes include:

  • HASL (Hot Air Solder Leveling): A cost-effective finish that involves coating pads with solder and leveling it using hot air.
  • ENIG (Electroless Nickel Immersion Gold): Offers excellent solderability and corrosion resistance, commonly used for complex PCBs.
  • OSP (Organic Solderability Preservatives): A thin protective layer that prevents oxidation, suitable for lead-free soldering.
  • Immersion Tin and Silver: Provide flat surfaces for component placement and good solderability.
  • Lead-Free Finishes: With the move towards environmental friendliness, finishes like lead-free HASL and lead-free ENIG are becoming more popular.

Useful Articles

PCB Design Guidelines

  • PWB/PCB Design – Analog, RF & EMC Considerations in Printed Wiring Board Design
  • PCB Design/Layout Tutorial (PDF)

PCB Standards and Specifications

  • MIL-PRF-31032, Performance Specification Printed Circuit Board/Printed Wiring Board
  • MIL-PRF-55110, Performance Specification for Rigid Printed Circuit Board/Printed Wiring Board
  • MIL-PRF-50884, Performance Specification for Flexible and Rigid-Flexible Printed Circuit Board/Printed Wiring Board
  • GR-1274, Requirements for Reliability Qualification Testing of Printed Wiring Assemblies

Other Useful Links:

Santosh Das

Santosh, founder of this Electronics Tutorial Website, is an Electronics Geek, Blogger and Young Entrepreneur. He possesses vast experience in the field of electronics, electronic components, PCB, Soldering, SMT, Telecommunication, ESD Safety, and PCB Assembly Tools, Equipment and Consumables. Keep visiting for daily dose of Tips and Tutorials.

Also Read:

63 Responses

  1. katy Radcliff says:

    Thanks for sharing these tips and techniques for PCBA. And, the step by step guide video you have shared is also very effective and interesting.

  2. BEST Inc says:

    Really very helpful blog for everyone. You beautifully explained everything in brief. Thanks

  3. Kavya Vardhan says:

    Thank You for the sharing this blog

    These tips and tricks for PCB Assembly Process and Guidelines and even
    the sheered video is very effective to understand the things in easy way.

  4. MR BOBOY says:

    Thank You for the sharing this blog.

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