What is the process and definition of SMT Printed circuit boards

18 Feb, 2022

By ren

You can all witness the fact that electronic sorts of equipment today use smaller electronics than their conventional electronic equivalents. Wire leads are used to link components from one part to another in traditional kinds, similar to how kits and house construction work. Small components installed on the board's surface, on the other hand, perform a similar role in today's electronic equipment. This is made possible by a technique known as Surface Mount Technology ( SMT)

Technically, this technique is used in every piece of electronic equipment created today since it delivers a significant benefit in the PCB process. The technology also has a significant benefit in that the notion of employing small SMT components allows for the integration of several circuits in a smaller space. Aside from providing ample space, SMT makes the soldering processes and automated PCB assembly simple, lowering overall costs and increasing dependability.

What does Surface mount technology mean?

Surface mount technology is a circuitry approach for component placement on Printed circuit board surfaces that is somewhat complicated. It's a cutting-edge technology that's mostly superseded traditional through-hole technology in a variety of electrical devices. Since the 1980s, traditional through-hole technology with leads has made PCB board assembly difficult.

Capacitors and resistors, for example, required leads to integrate the circuit and fit them through holes. To facilitate simple replacement through holes, all techniques required to lead are to be inserted at the right pitch.

This technique was difficult to use since lead did not fit into the tightening holes over time. As a result of this difficulty, devices were frequently used to remedy the problem of mismatched components causing machines to cease operating. The method also slowed Printed circuit board assembly and resulted in considerable cost increases.

The PCB assembly technique does not require the lead to be passed through the board. Rather, it refers to physically soldering parts or components to the board. This led to the development of surface mounting PCBtechnology, which uses the SMT component, and the benefits of this technology have been realized since then. It is currently the most common technique used in electronics production and PCB assembly. Many SMT components, such as SMT resistors and SMT capacitors, passive SMDS, diodes, integrated circuits, and transistors, make this possible.

How does SMT PCB differentiate from SMD PCB?

SMD and SMT PCBs are fundamentally different. Surface mount technology (SMT) is a method, and a surface mount device is a piece of equipment. Simply said, the Surface mount process refers to the technique of soldering and mounting electronic components such as capacitors, integrated circuits, resistors, and transistors on a PCB board. The SMD is a term that refers to the elements or components used in this technique. It's important to remember that surface mount technology doesn't need components to be reserved for via hole pins. Furthermore, as compared to the through-hole integration method, surface mount devices are insignificant.

Let's take a look at the features that make up SMT to assist identify the two:

  • The components utilized do not contain lead or may be used with short leads.
  • The solder junction and the component's body are both on the same side of the PCB board.

Surface mount devices include the following features:

  • There is no lead.
  • Miniaturization
  • Perfect for assembling PCBs on the surface

Initially, electronic producers soldered surface mount devices using their hands. This was rather straightforward for the first group of components, however, it was much more difficult to arrange or manage the second lot. The procedure grew more difficult when multiple little things had to be physically placed on the board. The procedure has gotten easier with the discovery of SMD, as every through-hole element has adopted the SMT approach.

SMT PCB Assembly Process

The technique of making PCB devices with SMT involves using an automated machine to assemble electrical components. This machine installs these pieces on the board surface, but first, the PCB files must be reviewed to ensure that they are free of flaws that might affect the devices' manufacturability and operation. After checking that everything is in order, the SMT PCB manufacturing process is not limited to soldering and inserting parts or compounds on the PCB board, but also includes the following manufacturing process.

Application of solder paste

Applying soldering paste is the first step in building the SMT PCB board. The silkscreen technique may be used to apply the paste on the PCB. A PCB stencil customized from a comparable CAD output file can likewise be used. All you have to do now is use a laser to cut the stencils and apply the soldering paste to the places where you'll be soldering the components. The application of solder paste must be done in a cool atmosphere. After you've finished applying, set aside some time for assembly.

Examining of the solder paste

Following the application of solder paste to the board, the following step is to inspect it using the solder paste inspection technique. This is very important when looking at the position of your solder paste, the amount of solder paste utilized, and other fundamental features.

Confirmation of the process

If your PCB board has SMT components on both sides, you'll need to repeat the process for secondary side validation. You'll be able to keep track of the appropriate period for exposing the solder paste to room temperature here. This is the point at which your board will be ready for assembly. Components will continue to be prepared for the next plant.

Kits for Assembly

This is mostly concerned with the BOM (Bill of Materials) that CM uses for data analysis. This aids in the creation of a BOM assembly kit.

Putting together element kits

 The element is pulled from stock using bar codes, which are supplied in the assembly kit. When the kit is fully loaded with components, it is transported to the pick-and-place machine for surface mount technology.

Component’s preparation

To hold each component during assembly, a pick-and-place tool is used. A cartridge with a unique key that matches the BOM assembly kit is also used by the machine. The machine's purpose is to determine which portion the cartridge contains.       

SMT PCB Assembly advantages

There are several advantages to SMT PCB assembly, and to reap these advantages, formality is required. This assembly has special requirements for the design component since it necessitates the use of specialized PCB tools. Following the completion of the assembling process, a single board test will be performed. The following are some of the reasons why SMT PCB assembly is advantageous:

It is cost-effective

One of the best reasons to adopt SMT assembly is its affordability, which is aided by reduced manufacturing costs. On the board, the technique requires fewer holes. The processing cost will be reduced since there will be fewer holes. Alternatively, it will be simpler to produce large quantities at a lower cost per unit.


Another compelling argument to use SMT assembly is the increased efficiency with which circuit board space is utilized. Manufacturers may also use the technology to produce sophisticated electrical devices and then modify them into tiny gadgets. SMT assembly is also faster, allowing engineers and/or manufacturers to increase total production. Simply said, a procedure that takes 1-2 hours using traditional methods may be completed in as little as 10-15 minutes with SMT assembly.


The lead wire is used to connect electrical through-hole components in the classic procedure. The connection of components to the board is made by soldering them to the board in SMT PCB assembly, which simplifies the procedure.

NO errors

The advantage of SMT assembly is that it does not need the use of any electrical machinery or devices. As a result, mistakes are rare because everything is usually automated.

Less weight and size

When components are soldered directly to the PCB board, a lot of space is conserved, which keeps the board's performance and durability while reducing its weight and size.

Applications of SMT PCB

Many areas have embraced SMT because of its numerous remarkable benefits. Even though these SMT components are utilized for home building, they must be soldered with caution. Furthermore, while soldering components like integrated circuits, extreme caution is essential. In general, soldering components with 5 or more pins can be difficult unless special equipment is employed.

Surface mount technology components, on the other hand, can be used for specialized home projects. This is especially true when the connections and leads on SMT parts are too large for various equipment, such as standard soldering irons.


PCB manufacture is being transformed by the SMT assembly process, which is moving it to the next level. It is a very cost-effective, efficient, and reliable method for making PCBs. The only thing that can be expected in the future is, of course, advancements in SMT PCB technology as a whole, as it is a difficult procedure. The good news is that you can still acquire dependable PCB boards at reasonable prices today. Regardless, it's vital contacting reputable engineers or manufacturers that have the right equipment and competence to suit your board's needs. To choose the best manufacturer, look for one that uses current technology, high-quality materials, reasonable prices, and timely delivery.


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