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Stencil Printing - Advanced Topics

Presenter: Chrys Shea
Company: Shea Engineering Services
Date Published: 8/23/2016

Description: Presented by: Chrys Shea Shea Engineering Services

Chrys Shea

Part 1
This advanced course on SMT solder paste stencil printing builds upon the basics to give the attendees a larger toolkit for troubleshooting and process improvement. The session starts with handling incoming stencils, and the need to clean and verify them before putting them into production. A simple stencil verification method using SPI is described in detail, as is the inclusion of test coupons to aid in troubleshooting stencil quality issues.

The session continues with detailed methods of troubleshooting suspected stencil issues, showing images and data from several real-world stencil trials. It discusses the impact of aperture size and thickness variation, aperture location, and wall cut quality.

Stencil underwiping is presented, reviewing types of wipe sequences, wiper papers, and solvents, particularly as they relate to modern lead-free solder pastes and the preservation of nanocoatings. Videos and ultraviolet images of the effects of cleaning and nanocoatings are shown.

Part 2
Automated Solder Paste Inspection (SPI) is almost as important as the print process itself. SPI helps maintain process control, dial-in difficult PCBs, track defect trends and feedback positional errors or the need to perform an underwipe to the printer.

The session starts with basic methods of SPI equipment and their measurement algorithms. It continues with tips for production implementation and setting inspection tolerances. It then introduces simple experimental methods that can be performed quickly and easily to improve yields.

The differences between accuracy and repeatability are discussed, as are the effects of setting of reference planes and measurement thresholds. Finally, special features of some machines are highlighted, and their impact on the overall printing process output are discussed.

Finally, new information from current research projects, if available, will be presented.


Part 1
1. Stencil Verification
1.1. SPI verification
1.2. Test coupons
1.3. SEM images
1.4. Cleaning before using
2. Stencil Troubleshooting
2.1. Physical damage
2.2. Foil thickness
2.3. Aperture size
2.4. Aperture location
2.5. Impact on AR & TE
2.6. Cut Quality
3. Underwiping
3.1. Purpose and methods
3.2. UV Test results
3.3. Solvent requirements
3.4. Solvent compatibility with solder pastes
3.5. Solvent and paper compatibility with nanocoatings

Part 2
4. Automated Solder Paste Inspection (SPI)
4.1. SPI basics
4.2. Production implementation
4.3. Setting inspection tolerances
4.4. Improving print yields
4.5. Accuracy and Repeatability
4.6. Reference planes and measurement thresholds
4.7. Special features to improve performance

Who will benefit from this course?

  • SMT assembly process engineers and technicians responsible for production or new product introduction processes
  • Engineers and technicians just entering the SMT field who want to master the science and art of stencil printing
  • SMT quality personnel interested in helping improve print and end-of-line yields and identifying root causes of failures
  • OEM supply chain engineers responsible for supporting and/or assessing SMT assembly contractors

  • Pricing:
      Members: $200.00 (Log on to receive the member rate)
      Non-Members: $300.00

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