Process engineers looking to clean electronics assemblies typically start by identifying the cleaning equipment and cleaning material. Many use a small subset of test vehicles to qualify the process. This technique worked well when qualifying a cleaning process for conventional designs but typically fails to address numerous factors when designing leading edge cleaning processes. The design of the cleaning process must dig into critical factors such as the electronic assemblies being cleaned, characterization of the flux residue, cleaning agent options, materials compatibility, confirmation in the cleaning equipment, and process validation.
This case study will demonstrate a lean sigma approach to designing a cleaning process. The methodology follows five steps for selecting the best fit cleaning agent for a demanding Class 3 high reliability OEM. The first step is to establish the solubility parameter for the flux residue in question. Once the solubility parameter for the flux residue is established, solubility data on cleaning agents with solubility parameters similar to the flux residue will be tested at various levels to determine the best fit cleaning agent parameters. Materials compatibility testing on part hardware is the third step in the process. If materials compatibility testing meets stated objectives, validation in selected cleaning equipment on customer hardware is confirmed. If the each of these steps meets the stated objectives, process validation is run to qualify the process.