Since its inception in the 1960s, surface mount technology (SMT) has gradually become the preferred method for mounting electronic components on printed circuit boards (PCBs). The significant cost savings the SMT assembly offers through support for automation have driven its widespread adoption. However, despite the SMT dominance in the industry, its predecessor, through-hole technology (THT), which was instrumental in creating the first PCBs, still retains its relevance in the electronics manufacturing sector.
How does THT vs. SMT assembly compare to each other and what are their advantages and disadvantages? Find out in this article.
Component assembly
The core difference between the THT assembly and SMT assembly lies in the ways they mount electronic components on a PCB. THT involves inserting elements with leads through drilled holes in the PCB and soldering them on the opposite side. In contrast, SMT places components directly on the PCB surface, with soldering applied to the same side.
Inserting electronic components and soldering them on the opposite side of the board makes THT a more complex manufacturing process, requiring greater effort for automation and therefore often being performed manually. Meanwhile, SMT allows for streamlined production, primarily using pick-and-place automation machines. Surface mounting of electronic components also facilitates miniaturisation, which is more challenging with through-hole assembly.
Mechanical strength and electrical performance
The THT assembly provides stronger bonding between electronic components and the PCB due to through-hole leads and specific soldering techniques, enhancing mechanical strength and resistance to stress. This is typically not achievable with SMT.
On the other hand, mounting electronic elements with shorter leads directly on the PCB surface in SMT allows for better electrical performance, especially at high frequencies. The longer lead lengths typical for the components placed with THT can introduce undesirable capacitance and inductance, compromising high-frequency performance.
Rework and repair
PCBs assembled with surface-mount technology (SMT) feature a higher density of component placement, making rework and repair more complicated than with THT assembly. The miniaturised elements often used in SMT assemblies further complicate these processes.
In contrast, THT facilitates repair and rework due to the application of solder on the opposite side of the PCB. The larger size of THT components also simplifies these tasks.
THT vs. SMT assembly: which one is better?
As described in this article, there are fundamental differences between THT and SMT assemblies. Many electronics manufacturers aim to optimise production costs, which makes SMT a popular choice as it supports efficient automation. Additionally, surface-mount technology is effective for electronics miniaturisation and offers high electrical performance. These features are often preferable in modern electronics.
Despite the advantages of SMT, its predecessor, THT, is still widely used in electronics manufacturing due to its distinct benefits, such as stronger mechanical resistance and simplified repair and rework.
As a result, professional electronics manufacturers, such as Assel, prefer SMT for assembling miniaturised PCBs with more complex designs, particularly those based on multiple layers. At the same time, they leverage THT for assembling PCBs with larger components, designed to operate in harsh environmental conditions. Still, in practice, it is virtually impossible to choose exclusively between SMT and THT components, as many unique components are available only in one of these technologies.
Bottom Line
SMT and THT are two distinct technologies used for PCB assembly, each with its own advantages and disadvantages. These diverse features make it impossible to name one best manufacturing approach, as each has unique use cases. To learn more about working with a versatile contract manufacturer that can support your production with both technologies, visit asselems.com.
