Home - Blog

What is SMT–A Must Have Guide For PCB Beginners

If you look at the latest commercial electronic equipment, you’ll find them filled with several minute devices. Even your iPhone, microwave, and personal computer has them on their circuit boards. As opposed to using standard components, PCB makers mount these components onto the boards’ surfaces using specialized machines.  Of importance to note is that most of them are relatively small when it comes to size. The technology used to mount these devices goes by the name Surface Mount Technology (SMT). So, what is SMT in detail and its advantages? This article highlights more about SMT technology. At the end of this article, you’ll learn more about the advantages and disadvantages of SMT. You’ll get to understand its applications and much that you previously never knew about SMT technology. 

(what is smt–a close-up of surface technology)

1. What is SMT technology?

Surface Mount Technology (SMT) is a standard procedure in electronics circuit assembly today. Many PCB makers lately rely on SMT technology to manufacture their boards. Surface Mount Technology is the process of mounting electronic components to surfaces of PCBs. Surface Mount Technology is different from Plated Through-Hole Technology and the best replacement or option to PTH. With Surface Mount Technology, it’s possible to build even some of the most complex electronic circuit boards with a lot of ease. 

By using this technology, you can achieve smaller assemblies with excellent repeatability. All this is due to the high levels of automation and precision that comes with Surface Mount Technology technology. Many makers now use this technology as it enables them to design small PCBs that are lightweight and compact quickly. Better yet, it’s a much faster process compared to through-hole technology. Surface Mount Technology doesn’t call for too much work during the assembly. SMT is a simple process of just picking and placing PCB components on the board. 

A surface mount technology machine

(A surface mount technology machine)

2. Advantages of SMT technology 

Several advantages come with SMT technology that you need to know. If you are thinking of using SMT technology in your PCB assembly, then you are bound to enjoy some of its benefits. Some of its merits include the following:

Reduced manufacturing costs 

Surface Mount Technology comes with the promise of reduced manufacturing costs. SMT gives room for the creation of small PCB designs, hence reduced manufacturing costs. By using SMT, it’s possible to place components close to each other on the board. Therefore, manufacturers who use SMT technology enjoy the advantage of highly reduced manufacturing costs. 

Improve work efficiency 

SMT technology is also one of the best circuit assembly technologies as it improves work efficiency. It’s another reason why many PCB makers lately seem to prefer it. By relying on SMT, it’s possible to complete tasks in a single workday and within the shortest time possible. Unlike PTH technology, which may take some time, such is not the case for SMT. If you choose to assemble using Surface Mount Technology, work efficiency is a significant assurance that you’ll get. 

The overall structure is more straightforward. 

The overall structure of the boards you get to manufacture under SMT is simple. Unlike PTH assembled panels, the design of SMT made boards tends to be very simple. Surface Mount Technology assembled boards don’t demand too many technicalities such as drilling. In comparison to panels manufactured using other means, those made under SMT have more superficial structures.

Less error-prone 

There’s nothing more demanding than having to do circuit board re-works due to errors. Another advantage of SMT technology is the fact that it’s less prone to errors. Unlike detailed PTH, Surface Mount Technology isn’t into too much detail as such. It’s possible to correct small mistakes for boards made under SMT. Manufacturers prefer this method as it makes them produce many boards without many errors. 

Adaptable to smaller components/high component density 

It’s possible to place components on both sites of the circuit board using SMT quite easily. Better yet, you can do all this in higher density. The ability to identify parts close to each other is another advantage that comes with SMT. You can quickly achieve more connections per area and more features per unit area using SMT. 

Higher connection density 

SMT technology comes with the promise of higher connection density. Boards made using SMT technology can deliver a message of specific sizes within a particular time. Surface Mount Technology technology allows the delivery of notices, even in constrained locations. 

Need to drill fewer holes 

SMT technology is cheap. Here, you won’t have to drill many holes in your circuit board. SMT technology doesn’t call for many spots to carry signals to other parts of the board. Mounting holes that you can find on SMT assembled PCBs are few. With this technology, there’s no need to drill many holes. 

Low radiation emission 

Perhaps, one of the most significant advantages that come with SMT technology is low radiation emission. When assembling parts using SMT, you’ll encounter low radiation emissions. Therefore, it means that SMT is slightly a safer assembly method compared to other assembly methods.

Electromagnetic compatibility (EMC) performance is better than the old technology assembly method.

With SMT, it’s possible to achieve a compact package coupled with lower lead induction. Here, you get the assurance of a small radiation loop area, meaning an excellent EMC compatibility. Again, this is another merit that applies if you use SMT technology. 

PCB SMT assembly

(PCB SMT assembly)

3. Disadvantages of SMT technology

Even though SMT technology comes with several advantages, as highlighted above, SMT has some demerits. The following are some disadvantages that you’ll encounter if you use SMT. While they aren’t many, they are worth noting, especially if you are considering using it.

Mechanical stress on the board 

Since SMT technology ensures the placement of components close to each other, mechanical stress chances are high. Mechanical stress is disadvantageous, and many PCB makers hope to avoid it. Mechanical stress affects the overall functionality of a printed circuit board. On a PCB, mechanical stress brings about board fatigue. 

Unfortunately, this issue comes with SMT technology. With the placement of components so close to each other, the avoidance of mechanical stress becomes impossible. Much worse, due to mechanical stress, the solder tends to weaken quite quickly. Such, therefore, make SMT somewhat undesirable in some way. 

Environmental pressure 

To some extent, SMT is not suitable for the environment. Unfortunately, this is another disadvantage of SMT. The mounting components using SMT requires too much heat. A lot of heat is not only dangerous to the assembler but also to the environment. Unfortunately, that’s the problem that comes with SMT. While this technology may be cost-effective, at times, it’s not ideal for the environment. That’s the reason why PTH technology does well when it comes to environmental protection. 

Temperature stress  

Temperature stress affects electromechanical components, limiting their functionality. The same is true when it comes to printed circuit boards assembled under SMT. Since SMT involves the assembly of parts close to each other, temperature stress is a strong possibility. Matters concerning temperature stress accompanies PCBs manufactured under Surface Mount Technology. 

Incompatible with some parts 

Finally, yet importantly, the use of SMT makes other parts incompatible with others. Picking and placing components on a board come with its challenges. There are claims of some features failing to fit or be inconsistent with each other when using SMT. Parts incompatibility is also another significant disadvantage that accompanies Surface Mount Technology. 

 

Factory workers checking for SMT faults

(Factory workers checking for SMT faults)

4. The necessary process of SMT 

SMT is not a difficult undertaking, as you may imagine. Even though PCB assemblers do it differently, it mostly involves eight necessary processes

Print solder paste on board

The first process involves printing the solder paste on the board. Here, producers use a screen-printing machine. This step aims at ensuring that the welding of components on the pad goes well. 

Mount the parts

Secondly, the mounting of parts follows. Parts mounting involves careful component placement on a fixed PCB. 

Solidification

After parts placement, the process of solidification follows. The function of solidifying is to melt the SMT adhesives. This way, manufacturers ensure that surface mount components stick correctly on the board. A curing oven located at the back of the placement machine carries out solidification. 

Reflow welding

After solidification, reflow welding follows. The purpose of reflow welding is to ensure that the solder melts and the PCB board’s splicing. 

Automatic Optical Inspection

The fifth step after reflow soldering is Automatic Optical Inspection (AOI). The primary purpose of AOI is to check both the welding and assembly quality. With Automatic Optical Inspection, it’s possible to detect errors early enough before releasing the boards to the market. That’s necessary before going into mass production of circuit boards. 

Board cutting

After Automatic Optical Inspection, they are cutting the board follows. Designers cut the board to form a single individual. There are several machine-cutting methods used here. 

Grind the board

After cutting the board to the required shape, grinding soon follows. Grinding is one of the essential SMT processes. The primary role of grinding is to ensure the milling off the burr. Milling off burr ensures that you end up with a smooth board. During board production, you’ll undoubtedly encounter rough edges. Milling ensures the smoothening of rough edges. 

Milling of the board

After milling, then the last process follows. The final process involves washing the board. Cleaning the board ensures the removal of harmful welding residues such as flux. You can do board cleaning either manually or by using a machine. There are special machines that can help you to get the best cleaning results. Luckily, you can do the cleaning manually if you cannot afford such specialized cleaning machines. 

SMT machine at work

(SMT machine at work)

5. What is the difference between SMT and SMD?

There’s a considerable difference between SMT and SMD. Unfortunately, many don’t understand the difference between the two. If you are here, count yourself lucky. Here, you’ll appreciate the difference between SMT and SMD. 

Let’s begin with SMT. SMT (Surface Mount Technology) is the entire technology that involves the soldering and mounting of electronic components on a circuit board. Electronic features include capacitors, resistors, and transistors on a PCB, to mention but a few. Even though you can place pieces manually, mostly, manufacturers use special machines. With machines, the results are primarily perfect and of high quality. 

Special SMT machines, mostly known as Pick-and-Place machines, carefully pick and place all the components and places them on a circuit board. Again, you may do this manually if you so wish or have experience of doing it manually. However, you may have to go for the required pick and place machines for the best results for the best products for the best results. 

Surface Mount Devices (SMD) are components that manufacturers mount on electronic circuits for the circuit to work. SMT is the technology, while SMD is the parts that fit onto a bare circuit board. The fundamental components must find their way to the board using the SMT process. Mostly, manufacturers willing to remain competitive use machines to mount and solders SMD on a bare board. 

In the early stages, the placement of surface mount devices was mostly by hand. However, with improved technology, pick and place machines assumed this role. These machines are perfect for picking and putting all the parts on a circuit board. They do the job faster and much more efficiently than picking and manually placing the components. 

6. Common SMD components 

There are plenty of surface mount device components. All these devices work in unison to make up a functioning circuit. Some of the most common SMD components that you’ll on a board include the following:

Passive components: passive SMD 

Most passive components include inductance, capacitance, and composite devices. On a circuit board, passive SMD components are mostly cylindrical and rectangular. The mass of these components is also ten times lower in comparison to through-hole members. 

Transistors and resistors 

Transistors and resistors are also standard SMD components. If you look around, you won’t miss resistors and transistors on a PCB. Resistors divide voltages, reduce the current flow, and adjust signal levels. Apart from resistors, you’ll also find transistors on a PCB. Transistors amplify and switch electronic power and electronic signals on a printed circuit board. A transistor can work as a switch and an amplifier at the same time. The moment there’s no current to the base, then little to current will flow between the emitter and the collector. 

Diode

You’ll always find diodes on printed circuit boards. But what are the functions of diodes? Diodes are two-terminal devices that allow fluent electric flow, but only in one direction. They mostly convert Alternating Current (AC) to Direct Current (DC). Diodes mix signals. They also isolate sig.

Integrated circuits  

Integrated circuits are simple logic chips. Without integrated circuits, a board will not function as they help passing signals and reducing board temperature. 

Common SMD components: transistors ad resistors

(Common SMD components: transistors ad resistors)

7. The equipment we need for SMT technology

For SMT to go well or the way you want, you’ll need several essential equipment types. If you desire to produce in high volume, then you must have the best tools in place. Some of the equipment that you’ll need to include the following:

Placement Machines 

Placement machines pick and place PCB components into their required paces. This machine efficiently picks the entire surface mount components and puts them to their required place on the board. You need to understand that these machines tend to be costly. But at the end of the day, it will give you the perfect results. 

Programmers 

You can’t ignore the quality of input programmers bring in Surface Mount Technology as a manufacturer. Programmers do help in writing and subsequently testing PCB components. Also, they help in the maintenance of SMD in one place as they function on a circuit board. 

Wave soldering machines 

The Wave soldering machines are also essential equipment necessary in PCB production. Wave soldering involves the passing of circuit boards over a pan of molten solder. Wave soldering comes with its advantages. The most significant benefit that comes with this process is the possibility of designing many circuit boards. Manufacturers can make these boards in the shortest time possible. 

Printers 

Printers are also essential equipment in Surface Mount Technology technology. Manufacturers use them to print SMDs during PCBA. Without printers, you’ll experience a complicated assembly process. Your work may not come out as desired at all. 

Ovens  

Ovens play a significant role in the manufacture of PCBs. Mostly, ranges ensure proper solidification of solder paste on the circuit board. With proper solidification, the placement and adequate drying for SMD components take place as planned. 

Automated Optical Inspection System Machine 

Just as the name suggests, AOI machines check for the quality of the boards. These machines ensure that manufacturers make high-quality boards before releasing them to the market. 

The moment you have all the above equipment in place, then you’ll be able to produce high volume boards. Better yet, you stand a chance of making boards that adhere to ISO standards. As said earlier, you can achieve board mounting manually. However, for the best results, you may want to consider the use of particular machines. 

Failure to employ special machines may see you producing faulty or malfunctioning boards. If not mistaken, then you may end creating panels that don’t meet the market value. If you look around, you’ll notice that notable PCB makers use some of the market’s market’s market’s best equipment. Some of the best names in the industry use the latest equipment to manufacture their products. 

SMT placement machine at work

(SMT placement machine at work)

8. Application of SMT technology

Surface mount technology finds a lot of use in the production of nearly all electronics circuits today. Surface Mount Technology is usable for the mounting of almost all electrical components on a PCB. If you desire the perfect PCBA process, then you’ll apply SMT. Surface Mount Technology finds practically exclusive use in WellPCB. We will provide you with one-stop service and high-quality products. You can send us the documents you need to make and get a quote immediately! What are we waiting for? We have ten years of PCB manufacturing and assembly. 

This technology encapsulates more electronic components into smaller spaces on a PCB. SMT is a technology that will continue to grow in years to come as it is not ending anytime soon. If you are a printed circuit board assembler, then that is the best way to go is by using this technology. Even though it may cost you more, SMT is one of the best technologies to use. 

SMT technology at hand

(SMT technology at hand)

9. The future development trend of SMT technology

Surface Mount Technology isn’t hitting a reverse gear anytime soon based on predictions. SMT is driving thin, lightweight, reliable, and complex functionality in electronic products. Such is bound to even increase in the years to follow. Based on projections, Surface Mount Technology will increase by US$5.42 billion by the year 2022. In the future, they’ll be high on efficiency and further acceptability of SMT technology. They’ll also be the development of environmentally friendly Surface Mount Technology Bill Of Materials (BOM) of a PCB get fitted onto a board. PCB assembly in a few years ahead. 

Development and checking of PCBs manufactured under SMT technology

(Development and checking of PCBs manufactured under SMT technology)

Summary

SMT comes with several advantages. SMT is cost-effective and time manufacturing. With SMT, you can utilize both sides of the board for placing your electrical components. The lesser cost of setup, as well as manufacturing, is another advantage that accompanies SMT technology. 

Do you have any upcoming SMT PCB project at hand? Call us today to discuss more knowledge about PCBs.

Hommer
Hi, I am Hommer, the founder of WellPCB. So far we have more than 4,000 customers worldwide. Any questions you can feel free to contact me. Thanks in advance.

Services