Plastic packaging offers several advantages. It is cost-effective, compact, lightweight, and suitable for large-scale industrial production. As a result, plastic packaging technology is now widely used in consumer and industrial circuit systems. The plastic packaging materials and processes for chip passivation in plastic packaging have reached a high level of maturity. However, the resin materials and structure of plastic packaging still present certain risks. These risks are especially concerning in high-reliability applications. Common issues include corrosion, electrochemical migration, the “popcorn” effect, interface delamination, via holes in system-level and wafer-level packaging, and micro-bumps. This chapter discusses the characteristics, failure modes, failure mechanisms, stresses, and reliability of plastic packaging in detail.