The manufacturing of electronics requires the use of surface-mount technology. This technology is a core aspect of electronics production. SMT electronics has gained popularity in the engineering field. Electronic manufacturers now make use of SMT electronics due to the growing need for smaller electronics designs.
SMT has been a preferred choice in the industry to date. Most components in devices feature SMT electronics. In this article, we will discuss everything you need to know about SMT electronics.
What is SMT?
To get a vivid explanation of SMT electronics, it is important to know what SMT is. SMT means Surface Mount Technology. SMT designs electronic circuits in which components are mounted on PCBs. SMT electronics are often lightweight. The use of SMT in electronics manufacturing has helped to replace the use of traditional components.
Most electronic devices utilize SMT. This is because of the benefits this technology offers. SMT is an important aspect of electronic assembly. SMT is different from through-hole technology. In SMT, automated machines help to assemble electronic components on the surface of the PCB. This type of technology is very common in the industry.
SMT has been the mainstay in the electronics industry since the late 1980s. Most components in electronic devices feature SMT electronics assembly. It is important to understand how SMT electronics assembly works. Today’s electronic equipment features minute devices. Most consumer electronics are manufactured using SMT.
SMT provides a lot of benefits to users. Since the use of traditional components isn’t easy for PCB assembly, SMT has been a preferred option. SMT is the primary technology for the assembly of PCB in electronics manufacturing.
This technology is now the standard for PCB manufacturing. SMT was invented to make PCB manufacturing easier.
Benefits of SMT Electronics
SMT electronics offer a lot of benefits. Generally, SMT has helped in the production of smaller and lightweight devices.
Smaller size
This is one of the most common benefits of SMT electronics. With this technology, it is easy to create small PCB designs. With the use of SMT, it is easy to increase the density of the component on the board. It is very easy to place more components in a smaller space. However, this board still offers the capabilities of a larger board.
This makes it easy to produce smaller and lightweight electronic devices. These days, a very small device can be very complex. The size of a device doesn’t determine its complexity. For instance, some medical devices are very small, yet they are high-performance devices.
SMT reduces the weight of most devices. This provides more opportunities for designers to improve their skills. For example, if drones feature lighter and smaller circuit boards, they will need less power to fly. Reducing the weight of some electronic devices can also help to reduce the cost of shipping. SMT has helped in the production of smaller and lightweight electronic devices.
Better design flexibility
This is one of the benefits of SMT electronics. This technology offers designers more opportunities to be creative. When it comes to the production of PCB, flexibility is important. SMT helps in the production of rigid-flex and flex circuit boards.
This technology has contributed to the innovation of great designs. In those days, the traditional way of mounting components limited the ideas of designers. These days, the production of advanced electronics has continued to increase.
Lower cost
The ease of assembling these circuit boards helps to reduce costs. When it takes less time to assemble these components on the circuit board, the cost of production reduces in the long run. There is also a cost reduction in terms of the packaging, handling, and delivery of SMT devices. Since SMT requires drilling fewer holes, this makes SMT PCBs more affordable.
High frequency and high signal transmission
SMT electronics deliver high frequency and high signal transmission. This technology also enhances high density on multilayer and double sided PCB. These boards can offer high-speed signal transmission due to short delays.
SMT electronics can withstand vibration and impact. This is a major reason it is used in high-performance applications.
Easier automated assembly
SMT eliminates the need for custom wire layout, so it results in easier automated assembly. Since human assembly is eliminated, automated assembly is enabled. This also helps to reduce the time required for PCBs production.
Disadvantages of SMT Electronics
SMT electronics also has its downsides despite the benefit it offers.
Vulnerable to damage
Surface mount devices can damage easily. These devices are very sensitive to ESD. Therefore, manufacturers need to handle these devices with much care and caution.
Less power
The power of surface mount device components is less. Not all passive and active electronic components include SMT.
Difficult inspection
It is very hard to inspect components on a surface mount device because of its many solder joints and small size. Also, SMT inspection equipment is very costly.
Difficult to repair
Repairing surface mount electronics can be very difficult. This is because there is a small amount of lead space.
What is the Difference Between Surface Mount Technology and Surface Mount Devices?
Surface mount technology is different from surface mount devices. These two terminologies have confused a lot of people. In this section, we will talk about the difference between these two terms. SMD is one of the components of SMT. A surface mount device is a part attached to a circuit board during the manufacturing of electronics.
SMDs are much smaller than previous components. SMDs utilize surface mount technology. SMT involves the entire process of soldering and mounting electronic components onto a board. These components are surface mount devices.
Surface mount device is ideal for surface assembly on a printed circuit board. It is a small part fixed to a circuit board in electronics production. These devices are much smaller than previous components. Several different packages for passive surface mount devices. But, most passive SMDs are SMT capacitors or SMT resistors.
Surface Mount Assembly Process
SMT involves attaching electronic components to PCB’s surface. It uses reflow soldering to weld the surface-mount assembly to the plate. SMT is a common process in the electronics industry. SMT assembly process starts at the design stage. Here, the manufacturer selects different components and uses software packages for the design. The process of SMT assembly includes;
Preparation and inspection of material
You need to prepare the PCB and SMC. After this, ensure you check for any defects.
Prepare the template
In solder paste printing, the steel mesh helps to fix a position in solder paste printing. The design position of the pad on the circuit board determines the steel mesh production.
Printing the solder paste
The solder paste printer helps to apply the solder paste to the solder pad on the circuit board. This machine uses a scraper and a template to apply solder paste. Solder paste printing is a common method of applying solder paste. However, spray printing is another method that is becoming more popular.
Spray printing is commonly used in sub-contract departments. Here, you don’t need a template. You can use a mixture of tin and flux to connect SMC and solder pads.
Inspection
You can include automatic detection to most solder paste presses. But, this process can consume more time depending on the PCB’s size. You can use a separate machine to achieve this. The spray printing machine uses 3D technology to detect more problems. The solder paste printer’s detection system uses 2D technology.
Components location
After inspecting, the next stage is the placement of components. A clamping nozzle or vacuum helps you to remove every component from the package. Then, the visual system checks them and places them in a programmed position.
Reflow soldering
The next step here is to transfer the PCB assembly to the reflow welder. The welder then heats the assembly to a good temperature. The electric welding connections form between the circuit board and the component.
Reflow soldering is one of the less complicated stages in the SMT assembly process. However, the correct reflux profile ensures acceptable solder joints that don’t damage the assembly.
Cleaning and final inspection
After you have wielded and checked the board for any defect, clean the board. Repair any defects. This stage is very important in SMT assembly.
Applications of SMT
Surface mount technology is common in the electronics industry. This technology helps in the production of electronic circuits. SMT has grown so popular in the electronics industry due to the benefit it offers.
Since this technology helps in the production of smaller devices, it is a preferred choice among engineers. SMT also provides improved performance. With the introduction of SMT, the manual invention is not needed in the assembly process. It is very difficult to join wired components. This is because you need to pre-form them before fitting them into drilled holes.
SMT is ideal in the production of home devices and other electronic components. Most lightweight and small electronics feature surface mount technology. SMT is used in the production of medical, military, automotive, and industrial devices.
In terms of reliability, cost, weight, and volume, SMT is the best option. This technology has helped to improve the performances and life spans of electronic devices. Surface mount technology is used in the applications below;
Consumer electronics
SMT is the commonest method of mounting components on circuit boards. This technology helps in the production of tablets, computers, and smartphones. Since it is lightweight, it is the best option for the production of most consumer electronics. SMT allows for the production of smaller devices.
Medical devices
The introduction of SMT in the electronics industry has led to improvement in the production of medical devices. Surface mount technology has proved to be reliable for medical devices. Devices such as monitors, imaging systems, and infusion pumps feature SMT.
SMT has contributed to the production of more advanced and smaller electronic devices. Most medical devices today feature surface mount technology.
Industrial equipment
SMT technology is used in the industrial sector. This sector makes use of high-performance industrial devices. Electrical components help to power equipment in manufacturing centers and other industrial environments. Circuit boards in the industrial sector have to be durable enough. These PCBs feature properties that help them tolerate extreme temperatures.
More Facts About SMT Electronics
To date, surface mount technology is a popular technique in the PCB industry. This technology was introduced into the market in the 1970s. SMT has continued to be the mainstay of modern electronic assembly. Since its advent, it has replaced wave soldering assembly.
Surface mount technology is a revolution of the electronic assembly technology. One can say this technology has been a global trend in printed circuit board assembly. Therefore, it has led to a great development in the electronic industry.
The transformation in the electronic industry is attributed to the advent of SMT. More so, the use of SMT indicates the scientific progress degree of a nation. This technology made electronic components to be highly reliable and lightweight.
Almost all devices in today’s world feature surface mount technology. SMT has helped manufacturers to design small electronic devices that can be used in high-performance applications.
Techniques of SMT
SMT has different types of techniques. These techniques can be classified according to assembly and soldering method.
- Assembly method
SMT techniques are categorized into double-sided mix assembly and single-sided mix assembly.
- Soldering method
Here, SMT are in two categories, which are: Wave soldering and reflow soldering
Some elements that influence the quality of soldering include:
- Solder quality
- PCB design
- Flux quality
- Equipment and administrating
- Oxidation degree on soldered metal surface
Factors that influence reflow soldering quality
Several factors affect the quality of reflow soldering. These factors are explained below;
Technological requirement for setting temperature curve for reflow soldering
Soldering quality depends on temperature curve. Before 160 degree Celsius, one should control the rising rate of temperature to 2 degree Celsius per second. PCB and electronic components suffer heat when the temperature increases too quickly. This damages components and leads to PCB deformation. Meanwhile, that kind of high solvent evaporation speed makes metal powder spilled with solder ball.
The peak value of temperature should be more than melting point of alloy by 40 degree Celsius. A low peak value of temperature can result in incomplete soldering without producing a metal alloy layer. Sometimes, solder paste can fail to melt. A long reflow soldering time or high temperature value can make metal alloy extremely thick.
Soldering paste quality’s effect on reflow soldering technique
Statistics revealed that printing technique related problems account for 70 percent of surface assembly quality issues. During the printing process, edge subsiding and insufficient printing cause disqualification. PCBs having these kinds of defects need to receive work. Certain inspection standards should be according to IPC-A-610C.
Technological requirement for SMDs
Some techniques need to meet certain requirements to achieve ideal mounting quality. Some of these requirements are accurate positions, ideal pressure, and accurate components. Certain inspection standards should working in accordance with IPC-A-610C.
Features of SMT Electronics
The through hole technology requires inserting pins of components into through-hole vias on PCBs. THT features high weight and large volume which make it difficult to assemble. Surface mount technology provided solutions to the issues of THT. SMT includes the following features;
- Strong vibration resistance
- Low rate of defect for soldering points
- Electromagnetic and RF interference reduction
- High assembly density
- Automation accessibility
Surface Mount Electronic Components and Types
In terms of functions, SMT is similar to components for THT. However, the two techniques are comparatively better when it comes electric performance. Package types, use of components, and lead configurations make it hard to form a product.
For instance, they should tolerate high temperature and well-soldered to help products meet requirements. Surface mount technology has continued to evolve. This has helped to resolve several problems that arise from components standardization.
There are two major types of surface mount electronic components. They are passive and active surface mount electronic components.
Passive surface mount electronic components
Passive components don’t offer additional power benefit to the device. The shapes of these components are either cylindrical or rectangular. The weight of these components is much lower than their counterparts.
Surface mount capacitors and resistors are available in different sizes. This helps to meet the demands of different applications in the industry.
- Surface mount resistor networks
These networks serve as replacements for a group of discrete resistors. It is a combination of different resistors. The body dimensions may change. Most times, they are available in 16-20 pins.
- Surface mount discrete resistors
These discrete resistors are in two types. They are thin film resistors and thick surface mount resistors. Thin film resistors feature resistive element on a ceramic base. They also have soldered terminations on their sides. Thick surface mount resistors require screening a resistive film on an alumina surface. You can then get the resistance value by examining the variance between the compositions of resistive paste.
Active surface mount electronic components
For this type of component, they are various categories.
- Ceramic leaded chip carriers
Ceramic leaded chip carriers are in postleaded and preleaded formats. The user fixes the leads to the leadless ceramic chip carriers’ castellations in the postleaded chip carriers. In the preleaded chip carriers, the manufacturer attaches the Kovar leads or copper alloy. The dimensions of leaded ceramic packages are similar to plastic leaded chip carriers.
- Leadless ceramic chip carriers
These carriers don’t have any leads. They only feature castellations that offer shorter signal paths. These paths enable higher operating frequencies. Based on the packages’ pitch, the leadless ceramic chip carriers are in different categories. The commonest category is 50 mil. Others can be 20, 25, and 40 mil.
SMD Active Components for SMT
Plastic SMD packages are commonly used for nonmilitary applications. While ceramic packages have their own issues, plastic packages can be a better option.
Small outline transistors
Small outline transistors or SOT are four or three lead devices. The four lead devices are SOT 143 while the three lead SOT devices are SOT 23. These packages are suitable for transistors and diodes. SOT 89 and SOT 23 packages have become popular for surface mounting small transistors.
Small outline J packages
This package is like a combination of PLCC and SOIC. Small outline J package provides the benefits of both.
Small outline integrated circuit
This integrated circuit has leads on 0.050” centers. SOIC are suitable for housing several small outline transistors. Small outline integrated circuit needs careful handling to avoid any lead damage. SOICs have different body widths. The 150 mil is the one with less than 16 leads. The package with more than 16 leads is the 300 mil.
Fine pitch SMD packages
These packages feature a greater number of leads and finer pitch. They also have land pattern designs and thinner leads.
Plastic leaded chip carriers
This is a better option to ceramic chip carriers. These leads absorb the solder joint stress which helps to prevent any solder joint crack.
Ball grid array
The ball grid array is a package without any leads. BGAs are available in ceramic and plastic types. BGAs are ideal for self alignment when there is reflow.
Frequently Asked Questions
When should you use SMT electronics assembly?
Surface mount technology assembly is suitable for manufacturing smaller and lightweight electronics products. SMT assembly is a great technique for complex electronic devices. SMT is ideal for use in several applications. This technology is widely used in the electronics industry.
Does SMT require the drilling process?
Yes, SMT requires the drilling process. But, fewer holes are drilled into the PCB. This helps to reduce the cost of handling and processing. Through-hole technology requires more holes to be drilled. Therefore, SMT is a better alternative.
Conclusion
SMT electronics are the commonest technique in the electronics world. SMT has helped in the production of small, and yet complex devices. It is no doubt that most devices today feature surface mount technology. The advent of SMT has led to the production of better and more effective electronic devices. SMT is now the order of the day in today’s electronic industry.
