Diagnosing Underfill Spreading Issues Caused by Conveyor Vibration
Overview
A leading electronics manufacturer approached Solderstar Ltd after encountering intermittent underfill spreading during the curing stage of production. Although the process had historically been stable, recent batches showed inconsistent material behaviour, with underfill migrating beyond the intended area and causing contamination, cosmetic defects, and reduced process reliability.
With thermal profiles and dispense parameters appearing correct, the engineering team needed deeper insight into what was happening on the line. Using Solderstar’s real‑time verification technology, they uncovered a mechanical issue that standard thermal analysis alone could not reveal.
The Challenge
Underfill materials are highly sensitive before gelation. Any disturbance during this early phase can cause the material to flow unpredictably, leading to:
- Contamination outside the target area
- Inconsistent fillet formation
- Increased rework and inspection time
- Reduced overall process stability
Initial troubleshooting focused on the most common contributors: temperature uniformity and dispense volume accuracy. Both were confirmed to be within specification. Despite parameter adjustments, the spreading issue continued to appear sporadically across multiple production runs, making the root cause difficult to isolate.
Deploying Real-Time Diagnostics
To gain a clearer picture of the process environment, the engineering team introduced the Reflow Shuttle profiling system directly onto the conveyor. Unlike traditional profiling tools, the Shuttle captures multiple parameters—including temperature, conveyor speed, and vibration—while travelling through the oven under real production conditions.
The data quickly revealed a pattern: abnormal vibration spikes were occurring as assemblies moved through the curing oven. These mechanical disturbances aligned precisely with the zones where underfill spreading was most frequently observed.
Identifying the Root Cause
Further investigation traced the vibration to a worn conveyor drive component. The deterioration had developed gradually, making it difficult to detect through routine maintenance checks. However, the vibration was significant enough to disturb the uncured underfill before it could stabilise, causing it to spread beyond the intended boundaries.
This mechanical instability had gone unnoticed because traditional thermal profiling alone does not capture vibration or mechanical movement—highlighting the value of multi‑parameter verification.
Corrective Action and Results
After identifying the worn conveyor drive component as the source of the vibration, the maintenance team carried out targeted repairs to restore mechanical stability. Once the component was replaced, the line was re‑profiled using the Solderstar Reflow_Shuttle to verify that transport conditions had returned to normal. The follow‑up measurements confirmed smooth, consistent conveyor movement with no recurrence of the vibration spikes previously detected.
With stable transport conditions restored, production trials demonstrated that the underfill remained correctly positioned throughout the curing cycle. The spreading issue was fully eliminated, process reliability improved, and rework levels dropped significantly. The manufacturer also incorporated periodic vibration checks into its preventive maintenance routine, ensuring long‑term confidence in the curing process and overall line performance.
Conclusion
This case demonstrates how hidden mechanical factors can significantly impact material behaviour during critical process stages. By using Solderstar’s real‑time diagnostic tools, the manufacturer was able to identify a non‑obvious root cause that traditional thermal analysis would not have detected.
The result was a fast, accurate resolution and a more robust, predictable underfill process moving forward.
If you’d like to explore how multi‑parameter verification can help diagnose hidden process issues, you can learn more about process verification or thermal profiling solutions.
