Understanding Sulfur-Induced Surface Discoloration On Pre-Plated Leadframes After Prolonged Environmental Exposure

The booming demand for semiconductors has challenged the supply chain to meet customer needs even with tight capacity. One factory limitation in package assembly is volume of N
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storage. When cabinets are full, some products are exposed to uncontrolled environment and be susceptible to foreign matter. In this study, the surface discoloration of QFN-mr packages was thoroughly investigated by a comprehensive examination of potential root causes. Some factors like etching parameters, Cu diffusion of a defective lead frame, outgassing of organic materials, and handling were investigated mainly by surface characterization. The investigation had pinned the root cause on the drastic increase in consumption of isopropyl alcohol as disinfectant in assembly cleanroom and office areas. The presence of diisopropyl sulfate and sulfuric acid derivatives detected by TGA-MS had validated the findings.