What is SMT Technology & Its Process?

In this tutorial we are going to learn about what is SMT Technology & Its Process?

SMT Technology:

Surface Mount technology (SMT) ( https://en.wikipedia.org/wiki/Surface-mount_technology ) is a technology all SMD components are mounted on surface at board with automatic method is called SMT technology. Nowadays largely replaced the through hole technology which components with wire leads into holes in the circuit board.

SMT components:

An SMT components is usually smaller than its though hole counterpart because it has either smaller leads or no leads at all. It may have short pins or leads of various styles, flat contacts, a matrix of solder balls (BGAs) , or leads on the body of the components.

PCB Soldering Types:

Through Hole Solder PCB – In through hole PCB which components are mounted with leads, as per below image we see all components are through hole components. This technique takes more PCB space for mounting .

SMD Solder PCB – In SMD PCB all components are mounted on surface board, there is not leads of components as per below image of SMD solder components mount PCB. This technique takes less space as compare to through mount PCB.

Electronic Components:

  • Resistor
  • Capacitor
  • Inductor
  • Transistor
  • Diode
  • MosFET
  • Fuse
  • RTC Crystal
  • Clock

All these components using in both technique like SMD & Though hole.

SMT Line Process:

As per below image of SMT line where all types PCB are assembled by machine is called SMT process where all components are assembled in SMT line.

SMT Line Process Step by Step:

As per below step for SMT Line Process

  1. Stencil Printer  – In this process are start first machine, In this machine take the stencil as per received PCB, then implemented the solder paste in board as per solder pad of SMD PCB, in this process have two types of technique Glue and paste .
  2. Pick and place machine – In this all SMD components should be reel then inserted into machine by feeder, Then make the program as per BOM , through this machine all SMD components place on PCB automated due to this we will get more productivity with best quality product.
  3. Reflows Soldering Process – PCB assemblies need to be preheated to activate the flux in the solder paste. Then they need to be heated at a higher temperature to reflow the solder.
  4. Cleaning Process – PCB Cleaning is process of removing flux residues from the PCB after the SMT process.

Electrical Testing Process of SMT:

  • ICT – Physical testing of the printed circuit board can also be carried out within SMT line, this is known as In – Line – testing, and Physical testing of the printed circuit board can also be carried out OFF line in separate testing area known as In – Circuit testing (ICT)
  • Fiber Probe Tester – In this process take the one good PCB then make the program as per good PCB, teach the all components value as per electrical circuit then tests the remains PCB.
  • Manufacturing defect analyzer – This tester offers a basic In-circuit test of resistance continuity and insulation, As per this name it is used for the detection of manufacturing defect like short circuits across tracks and open circuit connections.
  • Automated optical inspection – It is used for check the solder joint under components.
  • Automated X-Ray Inspection (AXI) – it works on same process on AOI that is used for check the solder joint under components. It also check defect the joint which can not visible by AOI .

PCB Functional Testing:

  • Identify errors in all functional aspects of a PCB
  • Identify failure threshold in a PCB when both upper and lower voltage are applied.
  • Verify speed, frequency, oscillator and other on board timing elements.
  • Verify all input and output features confirm to specification.
  • Establish all communication feature are operational.

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