What is the difference between SMT and SMDSMT stands for Surface Mount Technology, the entire technology of mounting and soldering electronic components, such as resistors, capacitors, transistors, integrated circuits, onto a printed circuit board or PCB. The components used are also referred to as surface-mount devices (SMD, surface-mount devices). It should be noted that SMT does not need to reserve corresponding through holes for component pins, and SMD is much smaller than through-hole insertion technology.
Features of SMT:
- Components have no leads or only short leads;
- The main body of the component and the solder joint are on the same side of the PCB;
Features of SMD:
- No lead (flat or short lead);
- Suitable for surface assembly on PCB;
The actual process of SMT
- Firstly, a PCB stencil is aligned on the surface of the boards and solder paste is applied using a squeegee to ensure the pads are coated with a uniform and controlled amount of solder paste.
- Secondly, via a pick and place machine or hand placement, the components are mounted onto the boards in their respective locations. The wet solder paste will act as a temporary adhesive but it is still important to ensure that the boards are moved gently to prevent misalignment.
- Thirdly, the boards are passed through a reflow oven which subjects the boards to infrared radiation, melting the solder paste and forming solder joints.Then the boards are passed through an AOI machine, or Automatic Optic Inspection machine which runs a number of quality checks on the boards visually, such as component alignment and checking for solder bridges. The boards then proceed to further testing.
Types of SMD
- Composite device
- integrated circuit
- Active device
Advantages of SMT
- Reduce PCB area;
- Reduced weight
- Installation is easy to automate;
- Reduce parasitic capacitance and parasitic inductance;
- Improve product quality and reliability;
SMT brought with it a new generation of electronic assembly technology, which is widely applied in applications from aviation, communications, automotive and medical electronics, down to household appliances and other fields.
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