How Does the PCB Assembly Process Work?

There is a Printed Circuit Board (PCB) located inside of every electronic device. PCBs are the foundation to which various small, electrical components are attached. The process of mounting the necessary components to a bare PCB, and then inspecting and testing the board, is called PCB Assembly, or PCBA.

As electronics technologies continue to advance and the demand for more functionality increases, smaller and more complex PCBs and components are being designed. For this reason, PCB assembly has become an even more crucial step in electronics manufacturing. Even a small assembly error could lead to poor performance or failure of an electronic device in the field. Given the criticality of this step, it is important that OEMs partner with a knowledgeable company, like RiverSide Integrated Solutions (RIS), for PCBA. RIS has the requisite experience and proven processes to guide OEMs through the PCBA process and select the right assembly technologies to ensure success in the field.

PCB Assembly Technologies

There are two primary techniques for joining components to the PCB: surface mount and through-hole. Each is described in more detail below.

Surface Mount Technology (SMT): this technology is the most widely utilized for PCBA. As the name implies, SMT attaches components directly to the surface of the PCB using solder paste and does not require any holes in the board. This method allows components to be mounted to both sides of the board, allowing for more components on a given board and smaller PCBs compared to PCB assembly using THT only.
Through-Hole Technology (THT): this technique runs component leads through pre-drilled holes in the PCB. This method is not utilized as frequently as SMT but is known for its reliability and strong connections that is some cases are able to endure more vibration and stress than boards assembled with SMT.

How Does the PCB Assembly Process Work?

Below are the primary steps in the PCB assembly process. The steps and sequencing may vary slightly depending on whether SMT or THT technologies – or a combination of both – are employed; however, the following describes the key elements of any PCBA process.

Apply Solder Paste: the first step in PCBA is to apply the solder paste to the sections of the PCB where components will be surface mounted. The paste is a mixture of solder and flux that is used to permanently join the components to the board in future steps. Many PCB assemblies use a stencil to guide the solder paste and ensure it is delivered to the correct areas of the board and in the proper amount.
Place the Components: the next phase is to place the necessary components on top of the solder paste. This step is often called “pick and place”. Depending on the functionality of the PCB, the components being added to the PCB may be resistors, capacitors, inductors, sensors, or other electrical parts. This step can be performed manually or with automation, but either way it is imperative that the right components are placed in the specified location on the board.
Soldering: the purpose of this step is to permanently bond the components to the PCB. PCBA processes using SMT typically utilize a reflow oven and conveyor system during the soldering step to melt the existing solder paste. With THT, the component leads are inserted through the existing holes and a wave soldering method is often used where a wave of molten solder flows across the bottom of the board. In both cases, the molten solder joins the components and leads to the board. The assembly is then cooled to solidify the solder once again and fix the components in place.
Inspect the Assembly: this phase of the PCBA assembly process is crucial. Proper inspection is necessary to ensure the prior steps were performed effectively. This step may entail manual, automated and x-ray technology.
Testing: the final step in the PCB assembly process is testing to ensure the PCB functions as designed. There are various test methods such as flying probe, in-circuit testing, and others. Once testing is completed, the PCBA component assembly process is complete.

RIS PCBA Expertise

At RIS, PCB assembly is one of our core competencies. We provide reliable, seamlessly-assembled printed circuit board systems built with extreme precision. Our skilled engineers, technicians, and assemblers work to expertly put together a complete PCBA. When you choose RIS for your PCBA projects, you can expect the hands-on customer care of a small manufacturing operation and the capabilities characteristic of a much larger company with our complete electronics manufacturing services for OEMs in any industry. Our electronics assembly expertise includes: