Investigating a rise in BGA defects
Equipment: REFLOW-C-01
Example period: Aug 10–25, 2026
Why did the defect rate rise, and which boards need attention?
How the agent investigates
Check the metric
Compare the BGA defect rate with the operation’s 0.35% ceiling to define the investigation.
Compare process conditions
Examine V6 and V7 together: temperature setpoints, measured temperatures, and defect rates.
Trace the exposed production
Trace all 42 boards processed under V7, including the 36 that passed initial inspection.
Prepare the report
Separate possible causes, affected production, and the questions the factory still needs to resolve.
What the analysis found
The evidence points first to a setpoint change.
V7’s Zone 6 setpoint was 245℃, compared with 232℃ for V6. Measured temperatures were close to the setpoints in both versions, making the unapproved recipe change an earlier investigation priority than equipment failure.
Thirty-six boards passed inspection under the same settings.
Of the 42 boards processed under V7, 36 passed their first inspection. Their shared process conditions make their location, shipping status, and need for reinspection relevant to the review.
What changed?
Two versions of the equipment's process recipe, as compared in the original case.
| Measure | V6 | V7 |
|---|---|---|
| Approval status | Approved | Unapproved |
| Zone 6 setpoint | 232℃ | 245℃ |
| Zone 6 measured average | 231.97℃ | 244.97℃ |
| BGA defect rate | 0.28% | 14.29% |
| Boards processed | 6,408 | 42 |
V7 has a small sample of 42 boards. The difference alone does not establish a cause.
How far does the exposure extend?
Processed under V7
3 work orders · 3 lots
- Passed inspection
- 36boards Review for reinspection
- Defects confirmed
- 6boards 2 scrapped · 4 for rework
The current locations and shipment status of the 36 boards that passed inspection still need checking. Trace all production that shared the conditions, including units with no defect recorded.
What still needs checking
Review the full temperature profile, the history of the recipe change, and shipment records. Possible causes identified in the analysis need validation on the factory floor.
Review the evidence and data limitationsSource: HEARTCOUNT's “Defects found. What happens next?” blog case, based on synthetic SMT data. The source article is in Korean.