Although it is not a hard and fast rule, most SMT components are reflow soldering, while through-hole components are wave soldering. In the through-hole PCB assembly technology, even if the component is inserted into the drilled hole, the circuit board will form a firm solder joint by wave soldering. Usually, through-hole components are inserted manually.
For SMT components, the solder paste is applied directly to the pad to keep the lead of the component in one place. When the PCB passes through the dedicated reflow soldering, the solder paste will reflow. Here, a strong solder joint is formed. If you are using a hybrid type, you need to use wave soldering and reflow soldering at the same time. There are ready-made automatic pick-and-place machines that can reliably handle various components.
Benefits of SMT and Through Holes
Let us understand why SMT processing types are often used:
Size: By default, SMT components or parts are small or miniature. No drilling is required. This looks clean and attractive, especially in the era of smaller electronic product board sizes.
Availability: Today, SMT has taken over the through-hole components. They are smaller, and PCB patches, which have replaced through-hole components such as resistors and capacitors, have accounted for more and more.
Performance: The use of smaller components in the patch makes the distance of electrical signal transmission shorter. This also reduces the signal flight time.
Cost-effectiveness: SMT parts are usually cheaper than through-hole parts, let us quickly understand the benefits of through-hole parts.
Availability: If you need larger parts for high-power applications, it may be difficult to find SMT equivalent parts. Through-hole parts are easy to obtain.
Strength: If the parts must withstand continuous pressure, the SMT solder joints may break. In this case, components such as connectors, switches, and other interface components require the strength that can be effectively provided from the leads soldered into the drilled hole.
Power: SMT is not a good choice for high-power circuits, because SMT soldering is difficult to achieve firm solder joints. Therefore, through-hole technology provides greater mechanical strength for thermal stability, high voltage, and mechanical stability.
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