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Stencil, Solder Paste & Printing Defects - Incomplete Prints Incomplete pad prints are normally a function of the paste and stencil aperture. The example shown in Figure 1 should not be particuarly demanding for the printing process or the paste technology of today.
The incomplete print is likely related to the poor cleaning of the stencil after previous use. The paste has probably been left in the stencil aperture, it has dried, and when the stencil is used again the complete pad print from the aperture is not possible. The same problem can occur with poor paste release from a stencil aperture, but not from such a coarse pitch partas the one shown. On finer pitch components, paste remains held in the stencil aperture and can be a paste stencil issue.
More Stencil, Solder Paste & Printing Defects:
Text and photos courtesy of Bob Willis |
