Why Rework Can Lead to Failures in Electronic Assemblies
Rework—modifying or repairing an electronic assembly after initial production—is a necessary part of electronics manufacturing. Whether it's due to design revisions, component replacement, or correcting defects, rework is sometimes unavoidable. However, it also introduces risks. In this blog, we’ll examine the key reasons rework can compromise the reliability of electronic assemblies and how Magnalytix helps manufacturers manage and mitigate those risks.
1. Thermal Stress
One of the most significant risks associated with rework is thermal stress. Each time a printed circuit board (PCB) is subjected to the heat of soldering or desoldering, the materials experience thermal expansion and contraction.
- How It Affects Reliability: Repeated heating and cooling cycles can weaken solder joints, cause delamination between PCB layers, and damage heat-sensitive components. These issues may result in intermittent connections, shorts, or complete failure of the assembly over time.
- Magnalytix’s Solution: We apply Surface Insulation Resistance (SIR) testing to assess the impact of thermal stress on reworked assemblies. SIR testing allows us to detect early signs of degradation that might not be visible through visual inspection alone, helping you address potential issues before they lead to failures.
2. Contamination and Cleanliness Issues
The rework process often introduces new sources of contamination—including flux residues, particulates, and chemical agents—that can remain on the board and impact performance.
- Why It Matters: Residual flux can retain moisture, which may lead to corrosion or electrical leakage. Particulate matter can also cause shorts or physical damage to components over time.
- Additional Risks During Rework: When paste or liquid flux is applied, there's a risk of it wetting under adjacent components. If flux remains beneath components without being heat-activated, it is particularly susceptible to moisture uptake. This can lead to leakage currents and dendritic growth. Flux residue around the rework area is often heavy, and topical cleaning (typically done with a brush) may spread dissolved contaminants to nearby parts. These residues are especially vulnerable under humid or variable environmental conditions.
- Magnalytix’s Approach: We use a combination of SIR, C3 testing (Cleanliness, Coating, and Contamination), and Ion Chromatography (IC) testing to evaluate reworked boards. While C3 focuses on localized contamination, IC provides a comprehensive view of the entire board. By combining these methods with SIR testing, we can gain an understanding of active contamination risks and failures.
3. Mechanical Stress
Rework can also introduce mechanical stress. Physical handling, component removal, and re-soldering all carry the potential for structural damage.
- The Risks: Micro-cracks in solder joints, lifted pads, trace damage, and misaligned components are all common mechanical issues introduced during rework. These defects may remain hidden during inspection but become failure points when the assembly is exposed to vibration or thermal cycling.
- Our Expertise: Through testing, Magnalytix may be able to uncover the effects of mechanical stress damage by detecting changes in surface insulation behavior. When combined with the right follow-up analysis, such as visual inspection, component removal with microscopy, and X-ray imaging if needed, we can provide an early warning for hidden defects caused by mechanical stress.
4. Material Degradation
Repeated rework cycles can contribute to material degradation, especially in components and substrates exposed to elevated temperatures or chemical treatments.
- Understanding the Consequences: Materials such as solder, PCB laminates, and component coatings may lose integrity over time. Common signs include weakened solder joints, layer delamination, and changes to electrical performance, any of which can reduce reliability and shorten product lifespan.
- How Magnalytix Can Help: Using SIR and IC testing together, we can track changes in material performance by identifying where electrochemical failure is occurring (through SIR testing) and what ionic contamination on the board may be driving that failure (through C3 or IC testing). Providing this data can help you make informed decisions about the long-term reliability of reworked products.
Conclusion
While rework is sometimes necessary, it carries risks that must be actively managed. Thermal stress, contamination, mechanical damage, and material degradation are all failure modes that can be introduced or worsened during the rework process.
At Magnalytix, we help manufacturers address these challenges with comprehensive testing and insight-driven guidance. Our goal is not only to identify where problems exist, but to help you resolve them through data-supported, practical solutions. Whether you’re refining a process or troubleshooting a persistent issue, we’re here to support the reliability of your assemblies—every step of the way.
To learn more about how we can help you manage the risks associated with rework, reach out to us. Together, we can make sure your products meet the highest standards of reliability—even after rework.