SMT has become popular due to numerous advantages over through-hole technology (THT).
SMT components are also easier to assemble. They can be placed closer together on a printable circuit board (PCB), allowing for more complex designs.
But what does SMT stand for? What are its advantages? How it differs from through-hole technology? Let’s find out!
What is SMT?
SMT stands for Surface-Mount Technology. It was before known as Planer mounting. It is a method of mounting electronic components on a PCB.
SMT involves soldering electrical parts on the surface of a PCB while THT involves passing leads through holes in the circuit board and soldering them on the other side.
Surface-Mount Technology offers many benefits over THT. They have better EMC performance, and mechanical performance. They are also cheaper, easier to assemble and align, smaller, and lighter in weight.
SMT Components
Surface-mount technology (SMT) components are electronic parts designed to be connected onto a printed circuit board (PCB). They are also called Surface-Mount Devices (SMD).
Unlike through-hole components, SMD doesn’t need wiring between two points.
SMT components are of different types, such as:
● SMT Resistors:
They are passive components that limit current in a circuit. They come in an array of sizes, tolerances, and resistance values.
● SMT Capacitors:
They are passive components that store electrical energy. They are used for decoupling and frequency control applications. They are available in an array of sizes, such as 1206 or 0805, and types, including ceramic, tantalum, and electrolytic.
● SMT Diodes:
They are active components used for controlling voltage signals in PCBs. They act as one-way switches for current. They come in various types, including Schottky, Zener, and rectifier diodes.
● SMT Transistors:
SMT Transistors are active components that regulate the flow of electrons and electricity. They are used for amplifying or switching electrical signals in PCBs.
SMT Transistors are available in an array of types, including BJTs, FETs, IGBTs, and MOSFETs.
When compared to through-hole (THT) components, SMDs offer several benefits, such as:
- Size:SMT components are much smaller than through-hole components. They allow for smaller, more compact designs. Besides, this also increases the component density or allows much more parts to be mounted in a unit area.
- Performance:SMDs often have better electrical performance than THT components. It is because they can be placed closer together on a PCB. So reducing parasitic capacitance and inductance.
- Cost:SMT components are often less expensive than through-hole components. They need less material and manufacturing time.
- Weight:SMDs are generally lighter than THT components.
- Assembly:These components can be assembled more accurately than THT components. It is because they are placed and soldered by machines rather than by hand.
SMT PCB Assembly Process
The Surface Mount Technology (SMT) assembly process involves several steps that include:
- Step # 1 – Solder paste printing:
The first step involves applying solder paste onto the Printed Circuit Board (PCB). Solder paste is a sticky mixture of small solder particles and flux.
Solder paste printing uses a stencil made from nickel or stainless steel. The stencil has openings that allow the solder paste to deposit onto the PCB in precise locations.
- Step # 2 – Component placement:
Next, the electronic components are placed onto the PCB in their correct positions. This can be done using automated equipment called a pick-and-place machine (PCB SMT assembly machine).
- Step # 3 – Reflow soldering:
The final step involves heating the PCB and its parts to a temperature that melts the solder paste. It forms a permanent bond between the parts and the circuit board (PCB).
Common challenges with SMT assembly include:
- Tombstoningoccurs when one end of a component lifts off the PCB during reflow soldering. It usually happens with components like inductors, resistors, and capacitors.
- Bridginghappens when two or more adjacent leads are connected by excess solder. It is usually fixed by minimizing the solder paste volume.
- Insufficient solderoccurs when insufficient solder material forms a reliable joint between the component and PCB.
- Voidsform when gas bubbles are trapped in the solder joint during the process of “reflow soldering”. This problem is prevented by modifying the circuit board stencil. Avoiding outdated or inferior-quality solder paste also works.
It is a must to use high-quality materials and equipment to address these challenges. Optimizing the process parameters and performing regular inspections and testing are also helpful.
Applications of SMT Technology
PCB SMT technology has been used in various industries, such as:
- 1. The automotive industry uses SMT technology in producing sensors, lighting systems, infotainment systems, and Electronic Control Units (ECUs).
- 2. The aerospace industry uses SMT technology for various purposes, including satellites and spacecraft, engine and propulsion systems, and Unmanned Aerial Vehicles (UAVs). Besides this technology is also used for Avionics systems that control flight and navigation.
- 3. The medical device industry has adopted SMT technology for implantable devices such as defibrillators and pacemakers.
- 4. SMT technology is used in smartphones, tablets, and laptops in consumer electronics.
Future of SMT technology
SMT technology is poised to flourish in the future as it continues to improve and evolve.
The increasing demand for consumer electronics such as smartphones and tablets and the development of new technologies, such as 5G networks and artificial intelligence (AI), is driving the growth of the SMT market.
According to GlobalNewWire, the estimated global Surface Mount Technology (SMT) Equipment market was around US$3.0 billion in 2020. It is expected to reach US$4.5 billion by 2027 with a CAGR of 6.2%.
In conclusion
SMT stands for Surface Mounting technology. It is used to mount electrical components onto a printed circuit board (PCB) surface.
It has several benefits over through-hole technology. It is used in various industries, such as medical devices, telecommunication, automotive, aerospace and defense systems, and consumer electronics.
The PCB SMT assembly process involves solder paste printing, chip mounting, and reflow soldering. Besides, it also requires tremendous quality control, cleaning, inspection, and testing for the best results.
The future of SMT technology is in the direction to flourish. It continues to evolve and improve with new technologies such as advanced weapon and defense systems, artificial intelligence, smartphones, and 5G networks.