Modern electronic devices utilize smaller components compared to traditional ones. Traditional devices used wires to connect components from one section to another, similar to the principles used in kits and house construction. In contrast, today's electronic devices use small components mounted on the surface of circuit boards to achieve a similar purpose. This is easily accomplished through a technique called SMT or Surface Mount Technology. Technically, all electronic devices designed today employ this technology because it offers significant advantages in PCB manufacturing. This technology also brings notable advantages as the use of tiny SMT components allows multiple electronic devices to be housed in a smaller space. Besides providing ample space, SMT simplifies the soldering process and automated PCB assembly; thus saving overall costs and improving reliability.

　　 What is Surface Mount Technology (SMT)?

　　Surface Mount Technology is a sophisticated circuit technology that involves mounting components onto the surface of a PCB. It's a modern technology that has largely replaced the traditional through-hole technology in various electronic devices. Since the 1980s, using traditional through-hole technology with leads made assembling PCBs quite difficult. The components used (e.g., capacitors and resistors) required leads to integrate circuits and pass them through holes. These processes required leads to be installed at the correct spacing for easy through-hole replacement.

　　This approach was quite cumbersome as the leads failed to cooperate with the holes over time, and the holes became increasingly tight. This problem led to frequent interventions to address machine stoppages due to component misfits. This method also delayed PCB assembly and significantly increased costs.

　　For PCB assembly, this process does not involve passing leads through the board. Instead, it involves soldering components directly onto the circuit board. This led to the discovery of SMT PCB technology utilizing SMT components, and since then, the benefits of this technology have been witnessed. Currently, it is the primary technology for manufacturing electronics and assembling PCBs. Many SMT components make this easy, including SMT resistors and SMT capacitors, passive SMDS, diodes, integrated circuits, transistors, etc.

　 　Difference between SMT PCB and SMD PCB

　　Fundamentally, SMD PCBs and SMT PCBs are different. Surface Mount Technology (SMT) is a process, while Surface Mount Device is a device. In short, SMT encompasses the entire process of soldering and mounting electronic components (including capacitors, integrated circuits, resistors, transistors, etc.) onto a PCB. The components or devices used in this process can be considered SMDs. It's important to understand that Surface Mount Technology can work without reserving space for through-hole pins. Furthermore, surface mount devices are significantly smaller compared to through-hole integrated processes.

　　To help clearly differentiate the two, let's look at the characteristics of SMT:

　　The components used are lead-free or can use short leads;

　　The solder joints and component bodies are on the same side of the PCB.

　　Surface mount devices are characterized by:

　　Lead-free

　　Miniaturization

　　Highly suitable for surface mounting on PCBs

　　Electronic manufacturers use manual soldering for surface mount devices. For a batch of components, this is fairly straightforward, but placing or handling another batch is difficult. The process becomes more complex due to the need to manually place several small items on the board. With the discovery of SMDs, the process became simpler as every through-hole component adopted SMT technology.

　　 SMT PCB Assembly Process

　　The process of manufacturing PCB devices using SMT involves assembling electronic components using automated machines. The machine places these components on the surface of the circuit board, but before that, the PCB files must be checked to confirm that they do not have issues affecting the manufacturability and functionality of the device. Once everything is confirmed to be okay, the SMT PCB assembly process is not limited to soldering and placing components or compounds on the PCB board, but must follow the production process below.

　 　Solder Paste Application

　　The initial step in assembling an SMT PCB is applying solder paste. The solder paste can be applied to the PCB using screen printing techniques. Custom PCB stencils from similar CAD output files can also be used. You simply use a laser-cut stencil and then apply the solder paste to the parts where components are to be soldered. Solder paste application must be done in a cool environment. After application, you can wait for some time for assembly.

　　 Solder Paste Inspection

　　After applying the solder paste to the circuit board, the next step is always to inspect the board through solder paste inspection techniques. This process is very important, especially when analyzing the placement of the solder paste, the amount of solder paste used, and other fundamental aspects.

　　 Process Confirmation

　　If your PCB board uses SMT components on both sides, you need to consider repeating the same process for a second-side confirmation. Here, you will be able to track the ideal time to expose the solder paste to room temperature. This is when your board is ready for assembly. The components will still be prepared for the next factory.

　　 Kitting Assembly

　　This mainly deals with the Bill of Materials (BOM) obtained by the CM for data analysis. This helps in developing the BOM kitting assembly.

　　 Inventory Kit with Elements

　　The components are taken from inventory using barcodes and included in the assembly kit. Once the kit is full of components, it is sent to a pick-and-place machine called Surface Mount Technology.

　 　Preparing to Place Components

　　Here, pick-and-place tools are used to secure each component to be assembled. The machine also uses a cartridge with a key corresponding to the BOM kitting assembly. The machine is designed to tell the cartridge which components to hold.