A repeated stripe or local print variation deserves a review of the squeegee edge as well as the program settings. Record where the suspect blade feature sits relative to the board. Increasing pressure can change the print without explaining the original defect.
Preserve the direction and location
Alpha’s SMT troubleshooting guide identifies damaged squeegee blades as a potential source of uneven print pressure. It also calls for consistent print performance in both stroke directions, making blade-specific evidence useful during diagnosis.
Photograph the installed blade and mark its orientation in the record. Note which blade and stroke produced each inspected board. A combined average across alternating strokes can conceal a problem associated with only one direction.
Create a location comparison
| Observation | Map to retain |
|---|---|
| Blade nick or deformation | Distance from a defined blade end |
| Print anomaly | Board coordinates and affected apertures |
| Stroke | Blade identity and movement direction |
| Stencil surface | Residual paste or visible contact pattern |
Inspect the edge using the approved maintenance method. Avoid unapproved polishing or reshaping that changes the blade geometry and removes evidence. Retain a suspect blade for review if replacement is used as part of the investigation.
Run a controlled replacement comparison
Use the approved replacement blade and preserve the intended paste, stencil, support and printer setup. Record the restart sequence and inspect the relevant deposits. If several settings change at once, a better result cannot be attributed confidently to the blade.
Compare the local pattern as well as overall deposit statistics. For example, disappearance of a narrow recurring defect at the mapped edge location is more informative than a small improvement in a board-wide average.
If the pattern remains, review other location-dependent contributors such as support and stencil condition. Do not continue replacing blades without using the comparison evidence to revise the hypothesis.
If a blade is removed before photography, retain its installed orientation on a tag or sketch. Reversing it on the inspection bench can make a left-side defect appear on the wrong side of the board map and weaken the comparison.
Define inspection and replacement evidence
Set blade inspection and replacement requirements from equipment guidance and process experience. The criterion should describe observable condition and print performance rather than relying only on elapsed calendar time.
Retain blade identity when parts move between machines. A repaired or previously used blade should have a known condition before entering another qualified setup. This helps prevent the same intermittent problem from migrating between lines.
The separation-speed guide addresses a different print variable, and dryness review helps identify defects concentrated immediately after cleaning.
Move from reading to a build-ready project
Use the fabrication and assembly checklists to prepare drawings, production files and test requirements.
Open the DFM checklist