A Unified DMAIC-Based Conceptual Framework for Lean Six Sigma and Industry 4.0 Integration in Electronics Manufacturing Services

The convergence of Lean Six Sigma and Industry 4.0 has emerged as a critical pathway toward intelligent manufacturing transformation. However, existing integration studies remain fragmented across technologies, DMAIC phases, and industrial contexts, with limited deployment architectures tailored to Electronics Manufacturing Services environments. This study addresses this gap by conducting a systematic literature review of Lean Six Sigma–Industry 4.0 integration research and developing a unified DMAIC-based conceptual framework specifically designed for EMS. Using a PRISMA-guided systematic review methodology, the selected studies were evaluated through quality appraisal, multidimensional analytical coding, quantitative diagnostic analysis, and cross-dimensional synthesis to move beyond descriptive literature mapping toward mechanism-based interpretation. The findings reveal that Industry 4.0 technologies are heavily concentrated in the Measure and Analyze phases, whereas Define and Control remain underdeveloped, resulting in structurally imbalanced maturity. To address these limitations, this study proposes an EMS-oriented conceptual framework that adapts established DMAIC practices by integrating Industry 4.0 technologies, deployment readiness criteria, digital traceability, and data-driven decision support into unified conceptual architecture. Rather than introducing a new DMAIC methodology, the framework contextualizes existing Lean Six Sigma principles for Electronics Manufacturing Services (EMS), providing a structured approach for intelligent continuous improvement in defect-sensitive manufacturing environments. Unlike previous frameworks that primarily associate Industry 4.0 technologies with individual DMAIC phases, the proposed framework introduces deployment readiness assessment, adaptive decision-gate mechanisms, enterprise-specific conceptual guidance, and EMS-oriented operational integration within a unified conceptual architecture.