Reading Solder-Paste Inspection Data as a Deposit Map

A single solder-paste inspection alarm identifies a deposit to investigate; a map of alarms can identify the process behind it. Before adjusting printer settings, compare where the variation occurs and how it changes over successive boards. That distinction helps avoid correcting one symptom while destabilizing the rest of the print.

Keep the measured quantities separate

Solder-paste printing creates a three-dimensional deposit. Koh Young’s inspection documentation explains the importance of volume measurement and discusses board-warp compensation and measurement conditions. Area, height, position, and volume should therefore be reviewed as different observations, not reduced to one generic “paste quality” score. Koh Young: solder-paste inspection technology.

Confirm the program revision and nominal deposit definition first. An inspection program built from an older stencil can produce convincing but misleading percentage results. Check the board side, panel orientation, aperture identities, and reference surface used by the measurement system. Preserve raw values where available instead of keeping only pass/fail counts.

Look for a pattern before choosing a cause

• A similar positional offset across many deposits suggests reviewing alignment and coordinate references.
• A cluster near one board area warrants checking local support, board condition, and measurement setup.
• Repeated difficulty at one aperture family calls for a geometry and paste-release review.
• A change over time may relate to process drift, cleaning intervals, or material condition.
• An isolated unexpected result should be inspected directly before changing global settings.

These are investigation paths, not diagnoses. For example, low reported volume beside a large cutout might be associated with board support, but it could also reflect an inspection-reference problem. Compare an actual deposit and a repeat measurement before assigning the cause.

Run a controlled correction

Choose one proposed change, state the expected effect, and print a defined trial quantity. Compare the same deposit groups before and after the change. Include features that were previously healthy so the review can detect unintended tradeoffs. Do not widen all inspection limits just to suppress an inconvenient cluster of alarms.

Connect printing evidence to the soldered result

Follow representative boards through placement and reflow, then compare the relevant joints using suitable inspection. Good paste measurements do not prove correct component orientation or a sound hidden solder interface. Equally, an acceptable solder joint on one board does not establish stable printing over a long run. Retain the trial data, final setup, and approved inspection limits together. This creates a usable baseline for the next material lot, stencil replacement, or production transfer instead of forcing the team to rediscover the same settings.