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What is the Difference between SMT Vs. SMD?

SMT technology equipment and board

In the PCB industry, the initials SMT and SMD are often used. But what do they mean? Also, what is the difference between SMD vs. SMT? In this post to compare the two acronyms, we will show the differences between them. Not only that, but also the ins and outs of each term, starting with their definitions.

What is SMT?

The initials SMT stand for Surface Mount Technology. In order to acquaint you with this PCBA technology, we’ll start by explaining its meaning before taking a look at the steps involved in the surface mount pcb assembly process.

SMT Definition

SMT, surface mount technology, is a type of PCBA assembly method in which electrical and electronic components are mounted directly onto the surface of printed circuit boards (PCBs).

The technology involves placing and soldering tiny parts, known as surface-mount devices (SMDs), directly to the board’s conductor pads.

The SMT technology is the most modern and cost-effective way of assembling printed circuit boards, as it requires fewer labor steps and has the ability to accommodate components with very small geometries.

SMT PCBA Process

SMT, as already mentioned, refers to the technology to mount a PCB board with electronic devices, usually automatically using robotic machines. The SMT PCBA process involves a few steps: Solder paste application, component placement, parts soldering and, finally, inspection and testing.

1. Applying solder on to PCB – A solder paste is applied to the PCB board. This is usually done with a stencil by hand or automatically using an automatic paste applicator or screen printer.

2. Placing Components on the Board – This is where SMT components are placed onto the board. The process involves using a pick and place machine to locate and place each component into its designated area on the PCB.

3. Reflow soldering – The SMT components are then soldered with a reflow oven, which uses heat to melt and form the solder paste over the pads of the components. During this process, the flux burns of while the solder melts to fuse with the component leads.

4. Inspection & Testing – After assembling, quality control teams inspect the PCBAs and then they are tested to make sure they are functioning properly. SMT PCBA testing methods include automated optical inspection, X-ray inspection, in-circuit testing, flying probe testing, and functional testing.

SMD components
SMD components
Resource: https://www.youtube.com/watch?app=desktop&v=8VN-enQnMWY

What is SMD?

Now that you understand what SMT means and the SMT PCB assembly process, let’s look into SMD and its meaning. After that, we will compare how the two terms, SMT and SMD, differ.

SMD Meaning in Electronics

SMD stands for Surface Mount Device. This is used to refer to the electronic component that has been designed to be mounted directly onto the surface of ta PCB board so that it can be soldered in place with a single step process.

These components are generally much smaller than those used in traditional through-hole method. To ensure their proper attachment to the board, SMD components have metalized leads that are soldered directly onto the surface.

The components used for SMD must be capable of withstanding high temperature. Hermetically sealing the SMDs also helps to protect them from environmental contaminants

SMD Components

The components used for SMD soldering are usually resistors, capacitors, inductors, and integrated circuits. They come in a variety of shapes and styles, such as rectangular or quad flat packages (QFPs) and ball grid arrays (BGAs). The SMD components can be divided into the following

1. Passive SMD Components – Resistors, capacitors and inductors

2. Active SMD Components – Diodes, transistors and integrated circuits

The primary advantage of using SMD components is that they offer a much higher level of packaging density than through-hole parts. They also require less space on the printed circuit board, allowing for more efficient use of the available area.

Additionally, surface mount components generally have a much lower profile than through-hole parts, allowing for greater flexibility in design and layout. This can be especially beneficial when designing smaller, more compact electronics products.

The SMT SMD difference in one photo
The SMT SMD difference in one photo
Resource: https://www.home-barista.com

SMT Vs. SMD

At this point, you understand the definitions for both SMT and SMD. Now let’s compare the differences between these two terms because, as you can see, they are closely related but still have quite a few distinctions.

SMT Vs. SMD: Meaning

The main difference between SMT and SMD lies in their meaning. SMT stands for Surface Mount Technology, while SMD stands for Surface Mount Device.

In other words, SMT is the method of attaching an electronic component to a PCB while SMD are the components themselves that are used in this process.

Despite this different in SMD and SMT meaning, the terms will often come up when talking about the same processes, such as the placement and soldering of components to a printed circuit board.

SMT Vs. SMD: Functionality

Another difference between SMT and SMD is that their functions are also different. The primary purpose of the SMT process is to provide a higher level of component density and faster assembly speeds than traditional through-hole construction.

SMD components, on the other hand, are designed specifically for surface mounting and offer superior electrical performance due to their smaller size and increased contact area.

As you can see, SMT and SMD are both important terms in the field of electronics. They both refer to different elements of the PCB assembly process, and understanding both terms is essential for a successful electronics project.

Conclusion

To conclude this SMT vs. SMD comparison, here’s what you need to know: SMT and SMD are closely related acronyms but with distinct meanings. SMT is the process of applying and soldering surface mount components to a board, while SMD are the actual electronic components used in this process.

That means the terms will usually come up together when discussing the process of assembling a PCB. However, by understanding the differences between these two terms and how they work together, you can get a better idea of what’s involved in creating an electronic device.

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