presented by:
Salil Pant

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What is “Surface Mounting”?
Attaching electronic component to PCB
Solder Joint forms Mechanical & electrical connection.
- No use of Through holes or Terminals.
Technology used before SMT
Through hole technology
Or THT
- Components with legs soldered through holes.
- Use of Printed Wiring Boards.
- Use of wave solder bath.
- Axially or Radially leaded passive components
- Dual –in-line, single-in-line packages for IC.
- Mature technology, low price, no peak performance.
Surface Mount
Vs
Through Hole
SMT VS THT
Types of SMT Assemblies
TYPE 1
SMT boards with parts on both sides of boards
TYPE 2
TMT + SMT
SMT components on secondary sides
DIP’s + Active SMC’s on primary sides
TYPE 3
SMC’s on secondary side
Only DIP’S on primary side
Common SMT
components
May not be available as Surface mount
Some connectors
Transformers/Solenoids
Large electrolytic caps
Solder Paste and its Properties
Tiny metal spheres of allows mixed with flux,solvent and thixotropic material.
Applied before component placement.
3 Types
a-RMA-rosin mildly activated
b-OA-organic acid
c-no clean
Properties of solder paste
Viscosity
Slump
Working Life
PCB fabrication & assembly process
Component packaging.
Component placement.
Reflow Soldering.
Process Window Index.
Reflow Soldering
Parts placed on the solder paste bricks.
Boards is placed in Oven and produces temperature profile shown below.
Process Window Index
Calibrate the Heating & Cooling of soldering jobs.
Measures the specification limits
Process is accurately measured,analyzed,tracked
& analyzed.
- A lower PWI indicates a more robust profile.
Advantages of SMT
Smaller Parts.
Denser Layout.
Cheaper PCB (no holes to drill).
Improved shock & vibration characteristics.
Improved Frequency response.
Easy to shield from EMI.
Easier to automate Manufacturing.
Disadvantages of SMT
More Heat generated.
Small Clearance makes cleaning difficult.
Visual Inspection Difficult.
Demanding design and Testing.
Reliability Issues.
What is Reliability ???
Reliability Threats
Common PCB Failures
What is Next???
Smaller Critical Dimensions.
Increasing Packaging Density.
Increasing max freq/bit rate.
Increasing power dissipation/unit area.
Lower price per electrical function.
Future Trends
The assortment of standard components is ever increasing, with availability of more and more complex integrated circuits and modules as standard components, with improved performance.
Programmable standard components can be customised to specific applications.
Emerging of industrial standards for specifications and documentation of standard technologies for easier communication between users, designers, producers, and subcontractors.
- Advanced technologies are emerging offering a broader range of features from high-end specifications to low cost than available in traditional technologies.