Surface Mount Manufacturing Basics


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The basics of SMT/circuit board assembly.

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Surface Mount Manufacturing Basics

  1. 1. August 13, 2013 Surface Mount Manufacturing Basics Familiarization information for SMT printed circuit board production
  2. 2. August 13, 2013page 2 / SMT Production Processes 1. Screen Printing 2. Adhesives/Epoxy Dispensing (Optional) 3. Pick and Place 4. Reflow 5. Inspection Post-Reflow (Optional) 6. Secondary PCB assembly (Optional) 7. Cleaning (Optional) 8. Depaneling 9. Product Sub Assembly / Product Assembly 10.Testing 11.Packaging 12.Shipping
  3. 3. August 13, 2013page 3 / Processes Defined • Step #1 Screen Printing – A bare PCB with all of the pads for surface mount components is placed into a screen printer where solder, in a paste form, is forced through a screen (with artwork to match the PCB) and onto the pads of the PCB.
  4. 4. August 13, 2013page 4 / Processes Defined • Step #2 Adhesives / Epoxy Dispensing (Optional) – A PCB with solder paste on the pads has adhesive or epoxy dispensed onto select locations. – This is typically only used when components are known to move prior to reflow (MELFS) or more commonly used to hold components prior to and during wave soldering.
  5. 5. August 13, 2013page 5 / Processes Defined • Step #3 Pick and Place – The PCB with the solder paste on the pads is presented to a pick and place machine. This machine picks up, inspects, and places components onto the solder paste.
  6. 6. August 13, 2013page 6 / Processes Defined • Step #4 Reflow The PCB with components basically on top of solder paste enters the oven and is gradually introduced to temperatures that cause the solder paste to become liquidous, once the paste is liquidous, the parts settle into the paste and make electrical contact with the SMT pads. The result when the paste cools as the PCB exits the oven is a mechanical and an electrical bond between the component(s) and the PCB.
  7. 7. August 13, 2013page 7 / Processes Defined • Step #5 Inspection (Optional) – The inspection or AOI (Automated Optical Inspection) can be performed pre or post reflow. This is typically an automated machine that uses a camera and verifies correct component placement and rotation. – Pre-reflow inspection allows for easier rework if needed
  8. 8. August 13, 2013page 8 / Processes Defined • Step #6 Secondary Manufacturing / Insertion – The SMT assembled PCB May have pins, tabs, connectors or other press fit type items installed. – This step is application dependant and may happen pre or post inspection, dependant upon the final product and custom application specifications
  9. 9. August 13, 2013page 9 / Processes Defined • Step #7 Cleaning (Optional) – The assembled PCB is run through an aqueous cleaning unit to ensure no contaminents or flux reside is left on the PCB. – This step is optional because a “no-clean” solder may be used whereas no cleaning is necessary, many customers clean PCB’s regardless of the type of solder and flux used
  10. 10. August 13, 2013page 10 / Processes Defined • Step #8 Depaneling – Individual images are depaneled or separated from the multi-up array by various means including hand separation, breaking, routing, or punching. – This step is very often overlooked even though the PCB is complete and very expensive at this point in the manufacturing process.
  11. 11. August 13, 2013page 11 / Processes Defined • Step #9 Product Subassembly / Assembly – The assembled, depaneled PCB is placed into a housing or made part of the larger assembly being built by the manufacturer – This step is different depending upon the product(s) being manufactured
  12. 12. August 13, 2013page 12 / Processes Defined • Step #10 Testing – The final product is tested • Step #11 Packaging – The final product is packaged for shipment • Step #12 Shipping – The final product is shipped to the end user, distributor, or customer