As technology grows the demand for less weight and smaller size component increases. This leads to new improved technology known as surface mount technology (SMT). Surface mount components are similar to plated through hole as far as there electrical function is concerned but the key difference is in their size. The small size of surface mount components (SMC) provides better electrical performance. Surface mount components are placed or mount directly on Printed circuit board (PCB) which means they do not require hole for mounting the component. They can be directly soldered on track side. Surface mount components have different shape leads and they have little circular at bottom etc for soldering as shown in figure below.
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SMD devices are mainly found in multi-layer PCB where size of device is major concern. They can also be used on boards or devices which contain both through hole and SMC because some components like transformer, heat sink are not suitable for SMC.
It depends on the requirement of an individual which technology is suitable between through hole or SMT. Like for beginners it is easy to solder the through hole components than SMC’s, but when it goes in multilayer complicity increases and we have to chose SMT. There are some points that makes SMT different from Through hole which are summarized below.
Difference between Trough hole and Surface Mount Technology are as follows-
1. As SMC are small in size they take less space in comparison to through hole. As you can see from figure the difference between sizes of LED.
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2. Pin count of component is increased greatly in SMT as compared to old through hole for example the micro process used today in computers PGA, FPGA etc.
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3. SMC is leadless component and can be directly mounted on board surface while through hole components required drilling to mount the components. As shown in figure below.
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4. The pads on the surface in SMT are not used for connection of layers on the printed wiring boards.
5. Size of through hole component is large in comparison to SMC there component density per unit area is more in through hole component result in large size of Printed circuit board.
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6. In SMT, components can be mounted on both side of PCB, this is not possible in through hole. Therefore SMC has made application possible which seems impossible with through hole.
7. SMT technology is used where large production is required which leads to low cost of unit assemblies.
8. With the help of SMC higher performance circuit can be made in small size which is prime requirement today.
9. Soldering of SMC is quite tough through manual soldering. Hence machines are required therefore big capital investment is required.
10. Designing, production, skills and technology required in SMT is very advance as compared to through hole technology.
11. Through hole technology is basically used in prototyping.
12. Soldering and de-soldering of through hole component is easy in comparison to SMT. Hence replacement of component is easy.
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