Surface mounting technology
Surface mount technology (SMT) concept evolved from through-hole manufacturing continues to provide significant improvements. By using SMT, the PCB does not need to be drilled. Instead, all SMT needs is to use solder paste. In addition to increasing a lot of speed, it significantly simplifies the process. Although SMT mounting components may not have the strength of through-hole mounting, they provide many other advantages to counteract this problem.
Surface mounting technology needs to go through 5 steps, the process is as follows: 1. PCB production---this is the stage where the PCB actually produces solder joints; 2. Solder is deposited on the pads, allowing components to be fixed to the circuit board; 3. With the help of the SMT machine, the components are placed precisely on solder joints; 4. Baking the PCB to harden the solder; 5. Checking the finished components.
The differences between SMT and through-hole include:
The widespread space problem in through-hole mounting is solved by using surface mounting technology. SMT also provides design flexibility because it provides PCB designers with the freedom to create dedicated circuits. Reducing component size means that more components can be accommodated on a single circuit board, and fewer circuit boards are required.
The components in the SMT are leadless. The shorter the lead length of SMC, the smaller the propagation delay, the smaller the package noise.
The density of components per unit area is higher because it allows components to be mounted on both sides, and it is suitable for mass production, thereby reducing costs.
The size reduction can increase the circuit speed. This is actually one of the main reasons why most manufacturers choose this method.
The surface tension of the molten solder pulls the component into alignment with the pad. This in turn will automatically correct any small errors that may have occurred in component placement.
SMT has proven to be more stable under vibration or large vibrations.
SMT parts are generally lower in cost than similar through-hole parts.
Importantly, SMT can greatly shorten the production time because no drilling is required. In addition, SMT components can be placed at a rate of thousands of placements per hour, while the installation volume for through-hole mounting is less than a thousand. This in turn leads to products being manufactured at the envisaged speed, which further shortens the time to market. If you are considering speeding up PCB production time, then SMT is clearly the answer. By using design for manufacturability (DFM) software tools, the need for rework and redesign of complex circuits is significantly reduced, and the speed and the possibility of complex designs are further improved.
All this is not to say that SMT has no inherent shortcomings. When SMT is used as the only attachment method for components facing a large amount of mechanical stress, SMT may be unreliable. It is impossible to mount components that generate a lot of heat or endure high electrical loads using SMT. This is because the solder can melt at high temperatures. Therefore, in the presence of special mechanical, electrical and thermal factors that make SMT invalid, through-hole mounting may continue to be used. In addition, SMT is not suitable for prototyping, because components may need to be added or replaced during the prototyping stage, and high-component density boards may be difficult to support.
With the powerful advantages provided by SMT, they have become today's main design and manufacturing standard, which is surprising. Basically they can be used in any situation where high reliability and high-volume PCBs are required.