A walkthrough to the PCB Assembly Process

A PCB assembly is the mounting of electrical components such as integrated circuits (IC), resistors, and capacitors, on the circuit board. PCB manufacturers use either the surface mount technology (SMT) or through-the-hole assembly. Each assembly method has similar procedures and uses almost the same raw materials except on some of the following instances:

PCBOne, through-hole technology requires thicker PCB since we need to drill the boards with holes.

Second, in SMT, we, at PCBnet.com, use surface pads to mount the components.

Third, the electrical components in through-the-hole technology have longer pins since these pins have to go through the holes before soldering.

Fourth, we use SMT if you require double sided PCB. Since electronic components in SMT are mounted on the surface, we can use the other side of the board to mount other electronic components.

Lastly, if you need electronic devices for heavy-duty equipment, we suggest through hole technology because of the stronger binding of the components on the PCB.

In our assembly team, we use both of the technologies, depending on your PCB requirements. What are the processes involved in the assembly stage? Below are the steps that our qualified and highly skilled individuals follow.

Preparing of the Raw Materials

The mounting technology schematic is forwarded to the assembly team. This schematic describes the manner of mounting the components, the stencil printing procedures, the comprehensive description of the electrical components (or the Bill of Materials) and other instructions that are important in the PCB assembly stage.

Printing the Stencil

Stencil printing refers to the squeezing of the solder paste on the board. This process is a critical stage since the stencil determines how much paste are placed on the board. The stencil used should be right because the paste contributes to the setting up of electrical connection on the board. Too much paste may overwhelm the electrical components.

Placing of the Components

During the preparation of the materials, the placing of the components in the machine placement is the second priority. This step follows immediately after paste stenciling to avoid solidifying of the solder paste on the board.


This process is the melting of the solder paste to connect the electronic components to the board. The right temperature is necessary to melt the solder paste. In connection with this step, the solder paste should have a lower melting point than the metals of the board and the components. Otherwise, the outcome may become faulty. In Through-the-hole technology, cutting off the extra pins of the electrical components is necessary.

Inspecting and Testing the PCBs

We inspect and test due to two reasons. One, we inspect and test your PCBs to follow the government quality standards and that our team takes extra measures to meet these standards. Two, we examine your PCBs to ensure that we deliver the highest quality of PCBs. In this stage, we use computers to detect any defects. In some instances, we manually inspect PCBs, especially for the prototypes. When the PCBs do not function accordingly, we send the PCBs to the rework area for repair. The PCBs that pass the testing stage are sent straight to the washing and packaging area.


In PCB assembly that uses washable solder paste, this is an important step to remove the excess solder paste and other accumulated dirt during the process. This washing step involves special chemical solutions to remove unwanted materials on the board.


This process is essential in keeping the service life of the PCB. We use packaging materials that protect your PCBs from shock, moisture and electrical discharges. We make sure that our personnel handles your PCB carefully. For handling purposes of the delivery team, we place instructions on the outer packaging. We know that no matter how good our assembly practices are, external factors may affect the quality of your PCBs.

Manual assembly

PCB assemblyThis stage may or may not happen, depending on three factors. One, if your PCBs do not pass the quality check, we forward the defective items to the repair and rework areas. Two, despite the use of SMT, we may still perform manual assembly on components that are so tiny for the pick-and-place machine to load. Three, manual assembly is practical on demo products.

These steps are general. For the highest quality of our PCB assembly, we may include more thorough inspection methods and other essential steps. We may even perform methods that are unique to our assembly company.