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What Is SMT and How to Calculate Automated SMT Assembly Cost?

Peter / 2020-12-10

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What Is Surface Mount Technology

Technology advancement has geared to the transformation of commercially made electronic equipment currently used in our society. Unlike traditional components like home kits and constructions that use wire leads, today's electronic components have employed minute devices mounted on the board's surface through the likes of a technology referred to as Surface Mount technology. What does this technology entail? Well, Surface-mount technology is primarily a constituent assembly technology that is linked to PCB. It works by attaching and linking components on the board's surface employing raft solder-reflow procedures. It is a kind of technology that provides significant benefits during PCB manufacture. In the perspective of the size, the SMT elements' utilization allows the package of extra electronics into a relatively smaller space. Besides the size, the SMT enables automated PCB assembly.

The Advantages of Surface mount Assembly

Small Size and Lightweight

Employing SMT technology to assemble the elements directly on the board is useful to minimize the whole PCB size and weight. This assembly technique enables people to set more elements in the confined space. Thus, allowing people to achieve awesome performance, reliability, and solid design. As far as size is concerned, the technology employs more elements in a small area, making these boards have a compact design and perform much better than their predecessors.

High Reliability

After the authentication of the prototype, the whole SMT assembly system is practically automated with error-free machines, reducing the manual action's fallacy. This is made possible by automation, where SMT technology guarantees the consistency and reliability of the PCBs.


SMT assemble typically works through automatic machines. Even if the machines' cost is relatively high, these machines are tailored to minimize manual procedures during the SMT process. This way, the production efficiency is improved, and the labor cost is reduced in the long-run. What happens is that many surface mount technology assemblers utilize software to digitally assemble the board prior to the actual production. This helps minimize delays and possible errors. When assembling, the designer can fix errors and get rid of issues when production starts. Errors like incorrect footprints and polarity marks can lead to project delays. Employing automated assembly still signifies that fewer workers are required for the job, causing financial savings and lower PCBs' overall cost.

Three Different SMT Package Styles

SMT components are distinct compared to their lead counterparts. Instead of connecting two points using a wire, SMT components are tailored to the board and solder component. Usually, there are three different categories of SMT package styles. These are transistors and diodes, passive SMD, and integrated circuits, learn more about SMT vs SMD here.

Passive SMDs

This encompasses various packages, however, the main passive SMDs are generally SMT capacitors and SMT resistors. Other components like crystals, coils, and others have personalized needs, hence have their own packages. Capacitors and resistors possess different package sizes, including 1812 and 1206 as the large size, 0805 and 0603 as the medium size, and 0402 and 0201 as the small sizes. Usually, the larger sizes were first used and are currently not popularly used as the smaller components. However, they can be applied where larger power components are required or where other aspects need the larger option.

Transistors and Diodes

SMT diodes and SMT transistors are usually restrained in a little plastic package. Usually, the transistor is a three-terminal semiconductor, while the diode is a two-terminal device. Diodes can enable current flow in one direction and hinder the flow on the other side. Diodes are also often used as switches, an excellent component for limiting frequency multiplication, signal levels, tuning, and securing the circuit current flow in a specific direction. Besides, diodes also work as rectifiers to change the current from AC to DC in a circuit. On the other side, transistors are versatile devices, which are made from various chemical compounds and elements like gallium arsenide, silicon, and gallium nitride. They are mostly used as switches or amplifiers where their frequency depends on the dimension, device structure, and material properties. However, the use of these two components employs surface mount technology where connections are made through the leads that originate from the package and can be bent to touch the board. These packages use up to three leads, making it easy to recognize the part that must be used.

Integrated Circuits

Integrated circuits are the backbone of modern electronic devices. They are considered the brains and the heart of most circuits. They are parts you see in ubiquitous small black chips on the circuit board. Simply put, every printed circuit board has a minimum of one IC; thus, it is easy and vital to comprehend them inside and out. Technically, there are different packages which are employed as IC. The package utilized on a board relies on the interconnectivity level needed. Several chips, such as simple logic chips, use 14 or 16 chips, while the VLSI processors can use up to 200 + pins. Thus, various packages are available to handle the perspective of a broad variety of requirements. Smaller chips can utilize a package like SOIC, an efficient SMT version of the package DIL. The larger chips like VLSI need a unique approach that employs a package referred to as the quad flat pack. This has a rectangular or square footprint with pins coming out on all four corners. The pins also use gull-wing formation, which means they are bent out to meet the board. The pins are spaced depending on the pin numbers needed. In some chips, the spacing can be up to 20 thousandths inch. Pins are fragile, which means they can easily bend. Therefore, exceptional care is needed when handling and packaging these chips. There are also other packages like BGA where its connections are underneath and not on the package side.

SMT (Surface Mount Technology) VS SMD (Surface Mounted Device)

Surface mount technology deals with a promising strategy of organizing components in the printed circuit boards. Usually, the SMT assembly way is more efficient, smaller, and faster in handling tasks. On the other hand, Surface mount devices are real components that are combined into the circuit board and use a particular method of assembly. People primarily confuse these two; however, they are somehow different. One is the real component (SMD), and the other is the mounting process (SMT). Another difference is that the right arrangement and selection of SMDs is significantly the main procedure behind the SMT. The SMT assembly is a strategy or workflow for working more efficiently with SMDs. For your prototype to improve, you will have to implement the right technique. For instance, the automated SMT machines can mount many SMDs on the electrical circuit boards quickly. The SMDs selected for the process will evaluate how efficient and whole SMT looks like. Another overlapping thing about these two is that SMDs evaluate the board's physical capability while SMT determines the timely installation.

SMT (Surface Mount Technology) VS THT (Through-Hole Technology)

THT was traditionally employed to develop the broader sense of the PCBs. Due to the rise in technology, SMT technology superseded the THT and has, up to date, remained relevant in place of THT. THT revolves around inserting components with leads and tails into PCB holes. Their components are better known as throughboard. The good side of THT is that bonds developed in THT components are relatively stronger than SMT bonds. This makes THT the right option for the component that undergoes environmental and mechanical stress. THT are also simple to swap out, hence the idea for testing and prototypes. The good side of the SMT is that SMT components can be restrained on either side of the board and in relatively higher densities. This makes it easy to assemble more powerful and smaller PCBs. Besides, the SMT components can be restrained ten times compared to the THT counterpart. The use of solder makes SMT to be considered more reliable and faster. SMT will also perform better and in a stable condition than the THT.

How Much Does Automated SMT Assembly Cost?

Several aspects influence the surface mount assembly cost. These can be technology, packaging of parts, cost of the labor, turnaround time, and the amount of PCBs needed. The utilization of the PCB calculator can help you determine the cost of the entire operation. However, the average cost of the assembly ranges from $10 - $50. This is just a rough estimation. The actual cost will vary from one PCB manufacturer to the other. Here are aspects that determine the overall cost.


This is influenced by the location of manufacturing. Since the making of these electronics encompasses a series of automated machinery and skilled human process, the labor cost cannot be ignored.

Turnaround time

This encompasses the duration of time needed to handle manufacturing procedures and satisfy customers' requests. Turnaround influences the cost in the sense that the faster the manufacturing, the higher the cost.


Manufacturing of higher quantity leads to reduced assembly cost because of economies of scale. In simple terms, when items are manufactured on a huge scale, the PCB unit price significantly drops.


The type of technology used to manufacture PCB components also influence the overall cost. However, the SMT can offer cost-saving ways since setup costs are relatively lower and automation is hugely involved.

Parts packaging

Some SMT parts require proper assembly and are more labor demanding.

Surface mount PCB assembly technology is an essential component in the fabrication of modern circuits. Its great design and exceptional performance gears to the production of awesome and simple to manufacture devices.

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