What is SMT–A Must Have Guide For PCB Beginners

What is SMT technology?

Surface Mount Technology (SMT) is a standard procedure in electronic 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 the surfaces of PCBs. It is different from Plated Through-Hole Technology and is the best replacement or option for PTH.

With Surface Mount Technology, it’s easy to build even the most complex electronic circuit boards. 

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 come with Surface Mount Technology technology.

Many makers now use this technology, which enables them to design small, lightweight, and compact PCBs 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 picking and placing PCB components on the board. 

(A surface mount technology machine)

Diving Into Surface Mount Technology’s History

SMT entered electronics between 1976 and 1980 before slowly taking over through-hole technology.

Of course, the worldwide rise of SMT electronics gave this PCB assembly technique a striking reputation.

It made those products more functional while shrinking their footprint. At this time, digital cameras, camcorders, and video recorders had SMT circuits.

Since 1995, 3D, high-density, and micro-assembly have quickly advanced.

We’re seeing a decline in electronics with through-hole technology—dropping 11% per year!

Meanwhile, those using surface-mount technology are growing by 8%.

More Terms For SMT PCBs

PCB with active/passive components.

Everyone might use other ways to describe the process behind PCB component assembly. All of these are listed below:

TIME

Surface-mount equipment (SME) uses assembling machinery to add components to the circuit boards. 

SMA 

When dealing with surface-mount assembly, you’re making a circuit board with all the components attached to its surface. This involves gathering those pieces and checking them for quality after assembling everything.

SMD

Another one is surface-mount devices (SMD), which have electromechanical, active, and passive components.

You should note that SMD is more about those specific parts than additional binding materials, like solder. 

SMC

Surface-mount components (SMC) attach each circuit part to the PCB when everything is together. However, the solder doesn’t go on simultaneously with the components.

SMP 

You’ll use surface-mount packages (SMP) to connect components like chips more easily. These are case forms with a 4-digit ID. The first two numbers indicate the component length, while the last two indicate the width.

Ways To Fabricate

SMT has three fabrication techniques for PCB assembly. Each category, type 1A/1 B, type 2, and type 3, attaches all the parts differently.

• Type 1A: Each component gets added on the PCB’s primary side. 

• Type 1B: The components can be placed on any of the board’s sides. Once the paste is applied, the secondary side will need adhesive.

• Type 2: This one puts the surface mount and through-hole components on the primary side of the PCB. However, if you have SMT types, they will go on the secondary side.

• Type 3: All the components are added on both the primary and secondary sides, but the through-hole ones are placed on the primary side. 

SMT IC Package Types

Ball grid array integrated circuit on a board.

There are a lot of surface-mount technology packages out there that help with mounting circuit chips. You can look at a few of the more common ones for your PCB:

• Ball Grid Array (BGA): This type has tiny balls soldered on the chip’s bottom surface, which makes it denser. 
• Quad Flat Package (QFP): A QFP is a rectangle or square with leads reaching outward from each side.
• Small Outline Package (SOP): SOP is small-sized, so it doesn’t take up much space on a circuit board and has better mechanical stability.
• Quad Flat Non-leaded package (QFN): QFN doesn’t use any leads and has small metal pads to attach an IC on the board. 
• Small Outline J-lead package (SOJ): These packages have leads that look like a ‘J’ and come from two sides opposite each other. 
• Lead Grid Array (LGA): The lead grid array connects to the PCB via metal pads.

Advantages of SMT technology 

Several advantages come with SMT technology that you need to know. If you are considering 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 promises reduced manufacturing costs. SMT allows for the creation of small PCB designs, reducing manufacturing costs.

By using SMT, components can be placed close to each other on the board. Therefore, SMT technology manufacturers 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. This is another reason why many PCB makers lately seem to prefer it.

Relying on SMT, tasks can be completed in a single workday and within the shortest time possible. Unlike PTH technology, which may take some time, this 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 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. Compared 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 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 on boards made under SMT. Manufacturers prefer this method because it allows them to 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.

Another advantage of SMT is the ability to identify parts close to each other. Using SMT, you can quickly achieve more connections per area and more features per unit area. 

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. You won’t have to drill many holes in your circuit board here, and it doesn’t require 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, achieving a compact package coupled with lower lead induction is possible. Here, you get the assurance of a small radiation loop area, meaning excellent EMC compatibility. Again, this is another merit that applies if you use SMT technology. 

(PCB SMT assembly)

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 there aren’t many, they are worth noting, especially if you consider using them.

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 is associated with SMT technology. Because components are placed so close to each other, avoiding mechanical stress becomes impossible.

Much worse, due to mechanical stress, the solder tends to weaken quite quickly. This makes SMT somewhat undesirable. 

Environmental pressure 

SMT is not suitable for the environment to some extent. Unfortunately, this is another disadvantage of SMT.

The mounting components using SMT require too much heat.

A lot of heat is dangerous to the assembler and to the environment. Unfortunately, that’s the problem 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 for printed circuit boards assembled under SMT.

Since SMT involves assembling parts close to each other, temperature stress is a strong possibility.

Matters concerning temperature stress accompany 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 comes 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)

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 ensures that the components’ welding 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 solidifies the components. 

Reflow welding

After solidification, reflow welding follows. Reflow welding aims to ensure that the solder melts and the PCB board splices. 

Automatic Optical Inspection

The fifth step after reflow soldering is Automatic Optical Inspection (AOI). AOI’s primary purpose is to check the quality of the welding and assembly.

With Automatic Optical Inspection, errors can be detected early enough before the boards are released to the market. This is necessary before the boards are mass-produced. 

Board cutting

After Automatic Optical Inspection, the board is cut. Designers cut the board to form a single individual. Several machine-cutting methods are 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 of 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, the last process follows: 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. Special machines can help you get the best cleaning results.

You can do the cleaning manually if you cannot afford such specialized cleaning machines. 

(SMT machine at work)

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 (Surface Mount Technology, which involves soldering and mounting 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, most manufacturers use special machines.

With machines, the results are primarily perfect and of high quality. 

Special SMT machines, mostly called Pick-and-Place machines, carefully pick and place all the components on a circuit board.

Again, you may do this manually if you wish or have experience 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.

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. 

How Are SMT and Through-hole PCB Different From Each Other?

Circuit board assembled via SMT.

Surface-mount technology isn’t the same as through-hole, and they offer special approaches and features. 

• An SMT component may have more pins compared to the through-hole ones.
• The price for SMT production machines is costly.
• SMT uses less space on the circuit board. 
• There’s a higher cost when it comes to producing through-hole components.
• Choosing surface mount technology means you will need better design and manufacturing skills.
• Surface mount technology makes your circuit faster — it will have a smaller size with no holes. 
• Because of their high compactness, SMT components are denser.
• Through-hole technology is ideal for large/hefty components, which may go through recurring mechanical stresses.
• Assembly automation is possible with SMT, which works best for bulk manufacturing. 

Common SMD components 

There are plenty of surface-mount device components. All these devices work together to make a functioning circuit.

Some of the most common SMD components that you’ll find 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 than through-hole members. 

Transistors and resistors 

Transistors and resistors are also standard SMD components. Looking 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 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 pass signals and reduce board temperature. 

(Common SMD components: transistors and resistors)

The equipment we need for SMT technology

For SMT to go well or the way you want it, you’ll need several essential equipment types. If you desire to produce in high volume, 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 in their required place on the board.

You need to understand that these machines tend to be costly. But they will ultimately give you the perfect results. 

Programmers 

You can’t ignore the quality of input programmers bring to Surface Mount Technology as a manufacturer.

Programmers help in writing and subsequently testing PCB components. They also help maintain SMDs in one place as they function on a circuit board. 

Wave soldering machines 

Wave soldering machines are also essential equipment in PCB production. Wave soldering involves passing circuit boards over a pan of molten solder.

Wave soldering has advantages. The most significant benefit is the possibility of designing many circuit boards.

Manufacturers can make these boards in the shortest time possible. 

Printers 

Ovens  

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

Automated Optical Inspection System Machine 

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

Once you have all the above equipment, you can 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, you may want to consider using particular machines for the best results. 

Failure to employ special machines may result in producing faulty or malfunctioning boards. If not mistaken, you may end up 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)

Application of SMT technology

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, the best way to go is to use this technology. Even though it may cost you more, SMT is one of the best technologies. 

(SMT technology at hand)

The future development trend of SMT technology

(Development and checking of PCBs manufactured under SMT technology)

Summary

SMT technology has several advantages. It is cost-effective and time-consuming to manufacture. With SMT, you can utilize both sides of the board for placing your electrical components.

The lesser cost of setup and manufacturing is another advantage of SMT technology. 

Do you have an upcoming SMT PCB project? Call us today to learn more about PCBs.