Issue link: https://iconnect007.uberflip.com/i/1545206
20 SMT007 MAGAZINE I JUNE 2026 By comparison, many batch systems use tan- gential spray configurations that prioritize basket- based processing and higher assembly counts per cycle. While these systems improve throughput flexibility, they often reduce kinetic energy transfer at the board surface, limiting effectiveness be- neath BTCs. Testing performed using specialized glass test boards with 60 ±5 µm gaps demonstrates the performance differences between direct and tan- gential spray systems. Results show that tangential spray systems typically require significantly longer wash times to remove residues beneath low-stand- off components, especially during the final stages of cleaning. Complex Flux Chemistries Increase Process Demands Modern no-clean fluxes are specifically engi- neered to remain stable after reflow, but under thermal exposure, they may polymerize, harden, or become increasingly difficult to remove. Effective removal requires: • Proper solvent systems • Controlled wash and rinse temperatures • Adequate agitation to maintain chemical stability • Sufficient spray energy at the point of dissolution Maintaining these parameters consistently over time requires ongoing process optimization and feedback. One of the greatest challenges, how- ever, is that the most critical cleaning areas are directly beneath BTCs, making them often impos- sible to inspect directly. The Value of Glass Test Vehicles Glass test boards and transparent test compo- nents provide valuable insight into residue behav- ior beneath BTCs. Glass QFN chiplets, particularly when integrated into surface insulation resistance (SIR) test vehicles, allow engineers to visually evaluate flux entrapment, cleaning effective- ness, residue distribution, and process variability beneath components. These tools provide a highly effective comple- ment to traditional SIR testing by making contami- nation visible during environmental stress testing. Figure 4: Tangential spray system. Figure 5: Comparison of washing speed of direct vs. tangential spray.