Electronic component assembly technologies

Publish date 2021-11-16

How are electronic circuits built?

Along with the advancement of technology, various methods of connecting electronic components into circuits have evolved. The most common of them is the use of printed circuit boards (PCBs). This extremely versatile method of building electronic circuits has been with us for decades. Currently PCBs are the basic structural and functional part of almost all electronic devices. In this article we will talk about methods of mounting electronic components on PCBs. Below you will find the description and characteristics of the most popular technologies in this field.  

Through-hole technology (THT)

THT (through-hole technology) is one of the oldest technologies of printed circuit board assembly. It involves placing the leads in galvanized through-holes and soldering them on the other side of the board. Although more modern methods exist, THT still offers some significant advantages over them. One of these is a solid mechanical connection between the component and the board. Mechanical stability is important for larger components, as well as various types of connectors. Another advantage of through-hole components is their ease of manual handling. They don't require much experience or any special equipment beyond a typical soldering iron. They can be easily mounted on breadboards or prototype boards, making them an excellent choice for circuit prototyping and various hobby projects. However, through-hole components have some disadvantages. Although automated assembly methods and wave soldering technology exist, the assembly of through-hole components is still often done by hand. In addition, the large size of the parts does not allow for efficient use of PCB space or building compact devices.  

Surface-mount technology (SMT)

SMT (surface-mount technology) is currently the most common method of PCB assembly. The use of surface-mounted devices (SMD) offers many advantages. The far-reaching miniaturization of components allows for building compact circuits with a high density of connections. Furthermore, the assembly process is fully automatic, which allows for efficient, fast and cheap production of boards in large quantities. The most commonly used technique of SMD part assembly is reflow soldering. The board has precisely placed, exposed fields of copper (solder pads). The soldering compound in the form of paste is applied on those pads. SMD components are then placed in their designated places on the board. Soldering takes place in special reflow ovens, where the paste melts and forms permanent mechanical and electrical bonds. Manual assembly of SMD components, although still possible, requires a lot of precision and experience. The lack of markings on some types of components presents another difficulty, making them difficult to distinguish.  

Chip on board and WLCSP

Looking at a typical integrated circuit, we often don't realize that the vast majority of its casing is occupied by thin wires connecting the chip with the leads. The silicon chip itself, located in the middle of the package, is much smaller. It is possible to save a significant amount of space and costs by completely abandoning the casing along with the leads, especially in large production series. It is possible thanks to WLCSP and COB technologies. WLCSP (wafer-level chip scale package) is based on creating connections and chip packages while still on the silicon wafer, before it is cut. Integrated circuits created this way have exactly the same dimensions as their silicon chips. This allows for much greater levels of device miniaturization. COB (chip on board) technology, on the other hand, involves mounting a bare silicon chip directly onto the surface of a printed circuit board. Electrical connections are then made between them, using thin interconnecting wires or reflow soldering (flip-chip method). COB technology is also used to make high-performance LEDs for lighting products. However, integrated circuits without the enclosure are vulnerable to damage. Moreover, their semiconductor junctions can act as photodiodes when exposed to light. Photocurrents induced by them can cause the chip to malfunction. Therefore, integrated circuits without housing must be properly shielded. For this purpose, special "glob-top" epoxies are used. They create a coating that encapsulates the silicon chip, protecting it from light and mechanical damage.  

Fig. 1. Chip-on-board integrated circuit, covered in black glob-top coating



Which mounting technology to choose?

Component selection is an important aspect of any electronic project. We must often choose between many available packages and mounting technologies for a given component. The choice determines how well the component will perform its function. As this is not an easy task, our specialists at InterElcom are at your service. We offer a wide range of services and professional assistance in electronic circuit design, component choice and PCB assembly. We invite you to familiarize yourself with our wide service portfolio. In case of any questions, feel free to contact us through the form on our website.