Troubleshooting the Stencil Printing Process - SMTA

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Poor GasketingIf you suspect…Board SupportBad alignmentSolder mask higherthan padsStencil apertureslarger than PWB padsHot Air Solder Levelfinish creates unevenprinting surfaceLabels, inks, or othersurface featuresprevent stencil fromseating on PWBThen investigate:Check (clean or improve) PWB supportSee section on alignmentCheck solder mask height and compare tospecificationMeasure and compare to specificationMore planar, non-HASL finishes. Consult withPWB vendor on improving doming effect ofHASL process.Proximity of features to defects. Considerchanging locations of those features or halfetchingthe bottom of the stencil toaccommodate them.
Poor Alignment
Page 1 and 2: Troubleshooting the StencilPrinting
Page 3 and 4: Solder Paste Properties• Solder p
Page 5 and 6: PWBPads: Flat, RightSize, Free of D
Page 7 and 8: Solder PasteFormulation, Rheology,
Page 9 and 10: A Good Mechanical Setup isEssential
Page 11 and 12: Stencil SeparationIf printer has st
Page 13 and 14: Results16-mil pitch QFP
Page 15 and 16: Preventing The Bad and The Uglywith
Page 17 and 18: PSI and Solder Paste“Chops” eac
Page 19 and 20: Process ControlWith Automatic Solde
Page 21 and 22: Still Making Defects?Check the easi
Page 23 and 24: Check the ToolingNext: Remove the s
Page 25 and 26: Didn’t find the Root Cause?Time t
Page 27 and 28: Solder Bridges
Page 29 and 30: Poor Print DefinitionPeaks and “D
Page 31 and 32: InsufficientsPoor Aperture FillBonu
Page 33 and 34: InsufficientsPoor Aperture Release
Page 35: Poor Gasketing
Page 39 and 40: Summary - Troubleshooting• Unders
Page 41: Questions?Contact Chrys at:chrys@sh

Troubleshooting the Stencil Printing Process - SMTA

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