PCBA Board Manufacturing Steps / PCB Assembly Process

PCBA is the abbreviation of PCB Assembly, PCBA board refers to the complete circuit board when all components and connectors are soldered. Traditionally manual processes (hand soldered) were used to develop PCB Assemblies. In modern days this process is automated due to low-pitched ICs, small components footprints and dense circuits. As the speed of iterative updating of electronic products becomes faster, traditional electronic manufacturing companies integrating industry and trade cannot keep up with such a rhythm, making turnkey PCBA assembly companies more important. In this article, FS Technology will show you in detail how our assembly factory performs the assembly process.

PCBA assembly flow chart

PCB Assembly Process: Bare Board to PCBA

Step 1: Manufacture the Printed Wiring Board

PCB Design

Most of the turnkey orders that FS Technology receives start from concept, which means we need to start from the PCB bare board manufacturing all the way to the end of the assembly process. Since FS Technology already has an article about the PCB manufacturing process, we only briefly introduce PCB design in terms of manufacturing.

Circuit designers develop circuits using various PCB design tools including Altium, Protel, Orcad and Kicad etc. These tools can transform the designed circuits into manufacturing files. PCB manufacturing foundries use these files to draw conductive pathways (copper usually) over non-conductive substrate (like FR-4) with specific dimensions. The result is bare PCB board with all required pathways and drilled vias, which is the first requirement of PCBA. 

Step-2: PCB component procurement and storage

PCB component procurement

The first step of the process yields bare PCB and BoM (Bill of Material). The core of the PCB assembly process is to mount the PCBA components on the circuit board, so manufacturers need to purchase components before assembly. Based on the functionality you need to implement, list all the components(including ICs, passive components (R, L, C), connectors and through hole components) required for assembly and submit the list to a turnkey assembly company who can complete your PCB component procurement. In this step these components are arranged, inspected and properly stored prior to installation on the bare PCB board. 

Step-3: Cleaning the PCB board (before soldering)

Clean the bare PCB board before the assembly process begins

Cleaning before welding is easily overlooked and considered less critical. However, in the actual application process, most of the PCBA boards that are not cleaned before processing have many problems and failures due to long-term use. When the bare board for assembly is produced, it will be contaminated by various factors: oil stains on the surface of the human body, sweat, dust in the air, particles, etc. These stains can spread to where the flux needs to be applied, which can lead to potential electrical reliability issues on the board. So you need to know how to clean PCB and do the cleaning before soldering.

Step-4: SMD components stuffing

SMD plugin

The ICs, passive components and connectors can be SMD (surface mount Devices) or through hole. Both have different approaches for stuffing and soldering on the board. In this step, we will discuss SDM components stuffing only.

If the SMD only needs to be filled on one side of the PCBA board, a screening printer is used to print solder paste on the pads using stencils. After this placement of components are carried out and hot air is passed though the assembly which is called “Reflow”. This type of soldering is called Reflow Soldering which is different as compared to THT technology. 

If a PCBA board has SMD components on both sides, and additional step is involved before screening of solder paste. In this new PCBA manufacturing process, SMT Assembly adhesives are applied to bond surface mount devices (SMD) to the PCB board. These adhesives bond the components to the board and avoid their displacement during next processes. After applying adhesives solder paste is applied though screening printers and components are placed. Reflow soldering is the last step in this process. 

Step-5: X-Ray Inspection

PCBA assembly had to undergo X-ray inspection

After placing the SMD components, Multiple strategies are followed to debug the PCBA along with manual soldering. In the assembly workshop of FS Technology, manual inspection positions are arranged in the entire assembly process, and here we use X-rays for more detailed PCB testing. This way you can test for defects in ultra-fine pitch and ultra-high density boards, helping you find any shorted or unsoldered pins.

Step-6: Wave soldering

Wave Soldering During DIP Assembly

In addition to the above-mentioned SMT assembly, the complete PCB assembly process also includes DIP assembly. For THT (Through Hole Technology) components using DIP assembly technology, a different soldering process is used, called “wave soldering”. THT components have long leads, so drilled holes are made available on PCB board. Leads are inserted in these holes and that are soldered into the board and waves of molten solder is applied to attach the leads to the PCB board. 

Step-7: Manual Soldering

PCB Manual Soldering process

Due to some uneven and non-standard components and objects, manual soldering is carried out in this PCB assembly manufacturing process. This step is skipped if all components are as per standard and got proper geometry. 

Step-8: Cleaning the assembled PCBA (after soldering)

After the circuit board is soldered, some flux, ionic contaminants, organic residues, etc. will remain on its surface. These contaminants attached to the surface of the PCBA board are the main cause of circuit leakage. These substances can disrupt circuits and damage electronic components. If the board is stored in a humid environment, ionic contaminants on the surface can make it work, causing a short circuit on the PCB and even failure of the board. Therefore, not only do we have to clean the PCB before soldering, but the cleaning after soldering is also very important. 

Step-9: Comprehensive PCBA Testing

PCBA test equipment

In this last but most crucial step of PCBA development, a thorough inspection is carried out of the assembly. Although inspections are carried out during each step, but this final inspection is most important. Final inspection is carried out by most experienced and well-trained quality inspector who can point out any issue and debug before packaging. 

The above is the whole content of “Printed Circuit Board Assembly Manufacturing Process”. 

FS Technology PCBA Assembly Services

FS Technology is serving the PCBA industry since 18 years by providing cost effective solutions for low to high volume demands. Being equipped with state of the art production and inspection equipment and trained professionals for the above steps, FS tech is emerging as global partner for technology innovators. FS Tech project management exposure with international partners ensures smooth flow of the projects. Meeting high quality standards and on time completion of projects distinguishes FS Tech among other competitors. 

In addition, in order to give back to our customers for their support, FS Technology has introduced a lot of useful knowledge in the PCB ordering assistance blog.

More for newbies in the PCB industry

What is PCBA

What is PCB Board made of

How to assemble PCB

What does SMT stand for in electronics