The miniaturization of technology does not slow down and continues to surprise us. The devices we know are often released to the market in the “mini” version without losing properties and functions. Progressive miniaturization is possible only thanks to the appropriate assembly technique, which, instead of using traditional elements with conductive wires, allows you to mount small-sized details on the surface of the panels. This technology is called the surface mount, and we’ll take a closer look at it in this article.
Virtually all commercially produced devices today use SMT (Surface Mount Technology) because it offers significant manufacturing benefits. First of all, the size of SMT components allows you to pack much more electronics in a much smaller space, allowing the miniaturization of devices. In addition to an extent, surface mount technology enables production to be automated, resulting in a significant improvement in reliability. However, it is worth considering whether SMT assembly is only a source of benefits or whether this technology is associated with some challenges.
What is SMT?
The prerequisites for the emergence of surface mount technology were the growing requirements for the micro miniaturization and feasibility of printed circuit board assemblies during automated assembly in the context of the expanding range of electronics applications for individual and home needs in the second half of the 20th century. However, miniaturization, where the component wires had to pass through the board, was practically impossible. Therefore, an SMT assembly was developed, requiring just individual components to be soldered directly to the board.
Surface Mount Technology is based on the automatic placement of components directly on the board’s surface after applying the template with solder paste. The tile prepared goes to the furnace, and the entire production process is completed with AOI control. Assembly of electronics using this method requires materials dedicated to this solution:
- PCB (Printed Circuit Board): A plate made of insulating material, covered with a conductive foil, intended for the assembly of electronic components
- Solder paste: A mixture of flux and small solder particles. The paste dedicated to the SMT assembly process also has the addition of tin alloys
- Cleaner: Based on isopropyl alcohol, used for wet cleaning
Advantages of SMT assembly
To help you understand Surface Mount Technology even better, we have listed a few of its essential benefits below.
- Possibility of full automation – one of the main advantages of such an assembly system is the possibility of full automation of this process. What influences, among other things, the speed of production of electronic components
- Electric noise reduction -SMT provides a significant weight reduction and a reduction in electrical noise. In addition, the compact housing and lower cable inductance in the SMT mean it will be easier to achieve electromagnetic compatibility (EMC)
- Possible miniaturization – SMT electronic components’ geometric size and volume are much smaller than pass-through interpolation components. As a result, SMT assembly components can weigh as little as one-tenth of their regular through-hole counterparts
- SMD elements can be set on both sides of the PCB – the absence of threading increases the surface that you can use
- Higher arrangement of components – the components used during SMT assembly are much smaller, so it is possible to arrange them more densely. At the same time, the surface mount technology, thanks to the use of solder paste, provides many more connections per component.
Disadvantages of SMT assembly
There are not many disadvantages of SMT assembly, but it is worth mentioning them. First of all, the main disadvantage of this type of assembly is that in the event of any errors during automatic assembly on the tape, manual repair of such elements is significantly tricky or even impossible. Therefore, SMT assembly requires extraordinary attention to detail. Therefore, such an assembly is usually not used in short-series production due to the low cost-effectiveness of such a solution.
SMT assembly is also associated with significant investments in equipment. Most SMT types of equipment such as reflow oven, pick and place machine, solder paste screen printer, even hot air SMD soldering station are expensive. Therefore, the SMT PCB assembly line requires a considerable investment. Surface Mount Technology is also not recommended for large-size components with high power or high voltage. Usually, the power of SMD components is lower. In addition, not all active and passive electronic components are available in SMD. Therefore, a significant proportion of SMD components cannot be used for high-power devices.
STM assembly: Good practices
As mentioned above, SMT assembly is, in most cases, fully automatic. However, it does not change the fact that to use one of the most effective methods of electronics assembly, you should follow several good practices.
Protection Againest Electrostatic Discharge
The abbreviation ESD (Electro Static Discharge) refers to the rapid energy transfer from a body or material charged with static electricity to another body or fabric with a different charge level. When installing sensitive components, use grounded mats to avoid damaging the parts. A good EMS provider will also have a resin-based floor system to counteract static electricity.
Securing MSD Components
MSD (Moisture Sensitive Devices) components are sensitive to moisture. Therefore they are factory vacuum packed. After packaging, the MSD components should be mounted and soldered within the appropriate time frame or placed in a unique drying cabinet if they are not used.
Double Quality Control
As we mentioned above, the entire production process ends with an AOI inspection; however, in the case of SMT assembly, it is worth using additional assembly checks with X-rays, which can identify errors that the AOI inspection will miss. Further review reduces the risk of duplicating costly mistakes in subsequent production processes.
There is no doubt that today there are still everyday situations in which it is necessary to use through-hole assembly. These two methods complement each other. In addition, SMT assembly requires large financial outlays and exceptional attention to every detail during the process. Therefore, manufacturers of original equipment should cooperate with a contract electronics manufacturer with the appropriate machinery, specialists, know-how, and work by world quality and safety standards. Thanks to cooperation with a contractor, companies can take advantage of the advantages of SMT assembly, eliminating disadvantages and thus increasing their profitability by optimizing costs.
For more information visit also: https://asselems.com/en/smd-assembly