The electronics industry has many terms and abbreviations that can easily leave us confused. Knowing what each one means is essential to understanding how everything works and setting a proper price quote.
Here’s the difference between surface-mount technology (SMT), surface-mount devices (SMD), and through-hole mounting (THM) when it comes to electronics manufacturing.
What Is Surface-Mount Technology Used For?
Surface-mount technology, or SMT, is the method used to mount electric components onto a printed circuit board. This method was developed in the 1960s and became widely popular in the 1980s. Nowadays, almost every piece of electronic hardware is assembled using surface-mount technology. It’s no surprise, then, that SMT is vital to printed circuit board (PCB) design and manufacturing. It enhances PCB quality and performance for the most part while significantly reducing production and handling costs.
The most considerable distinction between surface-mounting and through-hole mounting is that you don’t have to drill holes through the PCB to secure the components with SMT. Instead, lead pieces are placed and soldered directly onto the board. SMT components are much smaller and they can be mounted on both sides of PCB. PCBs can turn into a compact, high-performance powerhouse when using surface-mount technology to double the mounting surface.
Before SMT came around, through-mount technology was used. In this method, component leads are used to connect the board’s layers. Lead wires would go through the board’s holes and join all the layers. In SMT, those leads are replaced by “vias,” which are tiny particles that allow conduction throughout the board’s layers, ultimately behaving like through-hole leads.
While SMT and THM are two opposing methods for manufacturing electronic devices, surface-mount devices are used during the SMT process.
- Components can be mounted on both sides of the board
- Allows for smaller PCB size, thus making it better for smaller devices such as smartphones and wearables
- Lower cost and fast production
- Components can be placed at rates of tens of thousands per hour
- They show more stability under vibration and shaking conditions
- Higher component density and therefore a smaller end product
- Challenging to test and visually inspect
- Significant investment in equipment to do SMT in-house
- Repairs can be costly
What Is Through-Hole Mounting?
Through-hole mounting is a process where component leads are run through drilled holes on a printed circuit board.
THM was the standard way of assembling electronics before SMT came onto the scene in the 1980s. Even though SMT took over the majority of manufacturing processes, THM is still widely used.
Since the leads are threaded into holes and not just attached to the PCB, the components are sturdier on the board, making them more resilient in harsh environmental conditions. That is why THM is best used for high-integrity devices that require layers to be strongly connected.
Perfect examples of through-hole component usage lie in aerospace and military products. Many lives depend on their reliability, and these products also need to withstand extreme conditions such as collisions, high and low temperatures, and intense accelerations.
THM is also very useful in the prototyping phase because it’s easier to make changes if necessary.
The most notable disadvantage of through-hole mounting is the need to drill holes in the PCB, which is an additional costly and time-consuming step. Other than that, the size of the printed circuit board is larger and isn’t very customizable due to the nature of the manufacturing method.
Through-hole components are segmented into two types: radial and axial lead components.
The only difference is that axial leads run through components “axially” (in a straight line), with lead wires placed on two opposing sides of the element, while radial leads are placed on one side of the component.
While both have their advantages and shortcomings, axial leads are usually used for their snug fit on the PCB board — and radial leads are used for high-density boards, as they occupy less space (but protrude more).
- Resilient to environmental impacts
- Some through-hole components are less expensive than surface-mount parts
- Stronger mechanical bond over SMT (which means they can undergo higher mechanical stress)
- Component placement rates for THM are a fraction of surface-mount placement rates
- Drilling holes in the PCB is more time-consuming and costly
- Limits the available routing area
- Requires soldering leads on both sides of the board
What Is SMD?
A surface-mount device is a device that has its electronic components mounted on the PCB by pick-and-place robotic machines using the surface-mount technology method. During this process, PCB manufacturers solder the element to the board by applying and heat-processing soldering paste.
Due to automation, the SMT method is widely used for mass manufacturing low-cost consumer electronic devices.
Soldering the component directly onto the printed circuit board instead of threading it makes manual prototype assembly and design revisions much more difficult.
Surface-mount devices also aren’t suitable for parts that are larger and run on a high voltage.
SMDs are best used in manufacturing smaller electronic devices, such as laptops, smartphones, wearables, and other mass-produced electronic appliances.
Partnering With an EMS Provider
In a nutshell, surface-mount technology and through-hole mounting are two different methods for assembling lead components on printed circuit boards.
SMT requires small PCBs and the components are mounted directly onto the board. It’s more cost-effective, so it’s used in the mass production of everyday electric appliances.
THM was the go-to method before surface-mount technology arrived in the 1960s, but it is still widely used by the military and aerospace industry. Perks of through-hole technology is that it provides devices that are more resilient to environmental impacts, as the components have stronger mechanical bonds to the board.
Understanding the fundamental processes behind electronic device assembly is crucial if you want to develop an electronic device.
Abbreviations such as SMT, SMD, and THM may sound confusing at first, but once you’re familiar with the definitions and usage, negotiating with EMS providers will come naturally to you.
If you’re looking for an EMS provider to help with your manufacturing needs, make sure you know what to look for in an EMS partner and do thorough research.