Understencil wipes and SMT stencil rolls are designed specifically for under-side cleaning and wiping of SMT electronics during assembly. Solder paste printing is a crucial step of the SMT assembly. In recent decades, up to 50% of all the defects in the final SMT assembly were attributed to the stencil printing process. Smaller circuit designs and component density create challenges when wipes leave behind residual solvents, solder balls, or excess solder paste.
PDF: Stencil and Misprinted Board Cleaning Handbook
SMT printers range between manual action and fully automated systems: manual SMT screen printers, semi-automated SMT screen printers, and fully automated screen printers.
Understencil Wipe Properties and Solvents
An under stencil wipe must be well suited for solvent compatibility but also be low-lint. Small and large fibers deposited into solder from a wipe stencil roll may hamper, bridge, or produce uneven solder deposits. Cleaning and excess removal is important for the SMT stencil wash processes, as any residual material affects the chemical and adhesive properties.
In higher pitch assemblies, wiping the bottom side of the stencil works well. On larger features, a small degree of solder paste on the aperture wall does not materially affect the printing process.
Consistency of the stencil wipe material is important for drying wiping and wet wiping. When wet wiping, it’s important that the stencil wiping material wicks quickly and evenly. Presaturated stencil wipes allow more tactile cleaning with fewer VOC emissions and wetting variability. VOC emissions are not only irritating and noxious for workers, but present asphyxiation and fire hazards.
Stencil Roll Wiper Materials
Polycellulose stencil wipes allow sorbency yet still provide a tough, abrasion-resistant, fabric with low fiber counts.
Dissipative wipe materials reduce dust and particulate attraction during fast-moving assemblies.
New ESD stencil wiper materials such as virgin rayon and polyester blended fibers allow more dense roll assemblies, more effective solder trapping, and cleaner wiper materials.
New Stencil Roll Materials SMT Stencil Printing
Green Monster stencil rolls are an emerging favorite for SMT printers. Polymeric resin-bonded stencil wipes improve porosity and fiber structure when capturing solder pastes and adhesives. The fabric density performs better under vacuum than paper-based products. Air is able to pass through the microstructures and permit uniform contact with the board under squeegee pressure for a controlled removal.
GREEN MONSTER!™
Rayon-Polyester Bonded Stencil Wipes
Green Monster stencil wipes include sizes for DEK, MPM, EKRA, and most major SMT stencil printing equipment. A synergistic blend of virgin rayon and polyester fibers bonded with polymeric resin improve wipe performance under vacuum.
Other Stencil Wipe Considerations
Sometimes, a pre-saturated SMT stencil cleaning wipe is a more tactile approach for cost-effective removal of thick-film pastes, partially cured epoxies and most inks used in screen printing operations. Stencil wipes prevent smearing, bridging, and solder balls when removing residual solder paste.
Othertimes, absorbent foam wipes are well suited for stencil or thick film screen wiping. Unique pore structures allow a controlled solvent transfer to screen and metal masks which aid spot removal of conductive adhesives, thick inks, and metal mesh.
Where to Buy Stencil Wipes Online
The most common stencil roll sizes for printers include, but not limited to:
- DEK Printers
- EKRA Printers
- FUJI Printers
- Hitachi Printers
- MPM Printers
- Panasonic Printers
- SMTECH Printers
- Yamaha Printers
For help selecting the correct stencil roll wipe size, view the Width / Depth selector here, (left side of the page)
Stencil Rolls
