Investigating Tombstoning with Pad and Process Comparisons

When a small passive stands up during reflow, replacing it fixes the individual board but leaves the production mechanism unresolved. Compare the two ends of the affected component and look for a repeatable imbalance. This review should include the board geometry and the actual assembly process.

Describe the defect precisely

Tombstoning involves a component lifting onto one end rather than forming the intended pair of solder joints. Indium connects the mechanism with unequal wetting forces and discusses pad geometry and thermal-process adjustments as investigation areas. The relevant issue is the balance during soldering, not merely whether both pads have the same name in the library. Indium: recognizing tombstoning.

Record the reference designator, which end lifted, component orientation, board position, and frequency of occurrence. Compare several panels rather than relying on one photograph. If the same end consistently lifts, preserve that directional information when reviewing copper and reflow data.

Compare the complete pair of terminations

• Check pad dimensions and their relationship to the actual component termination geometry.
• Inspect copper connections, nearby vias, and local copper mass at each end.
• Compare paste aperture geometry and measured deposits.
• Review placement offset, rotation, and seating in the paste.
• Check whether nearby features create different heating conditions.

For example, a symmetric footprint may have one pad connected directly to a broad plane and the other to a narrow trace. That is a reason to investigate thermal behavior, not automatic permission to add thermal reliefs. Any copper change must still meet the circuit’s electrical and thermal requirements.

Separate design effects from process drift

If only one component location fails repeatedly, compare it with similar parts elsewhere on the board. If many locations deteriorate during a run, examine printing consistency, material handling, and process changes. Confirm the actual component dimensions and termination condition when a new supplier or package suffix has been introduced.

Run controlled trials with a documented hypothesis. A stencil adjustment, placement correction, and profile change should not all be introduced at once if the objective is to learn the cause. Review solder quality at both ends and check nearby components after each trial.

Turn the result into a controlled release

Update the footprint or process record only after the evidence supports the change. Keep the accepted component, stencil, placement program, and profile revisions together. Do not use extra solder added by hand as proof that the printing process is adequate. The production objective is consistent wetting and stable joints on the full assembly, with an investigation record that can be reused if the same pattern returns on a later lot.