Process Parameters Optimization For Mass Reflow Of 0201 Components

The research summarized in this paper will help to address some of the issues associated with solder paste mass reflow assembly of 0201 components. Attachment pad design, stencil design, component to component spacing, component orientation, flux type, and solder paste reflow atmosphere were the major variables researched during the project. The two major responses from the experimentation were assembly yield and assembly quality. Assembly yield defects, such as tombstones (open solder joints), solder bridges, and solder balls (beads) were used to determine the assembly yield. Solder joint shape, solder appearance, and solder volume (unacceptable low, acceptable or unacceptable high) responses were used to determine the quality of the assembly process. The combination of flux type and reflow environment were found to have the largest impact in the number of assembly defects produced. Boards assembled with no-clean solder paste and reflowed in an air atmosphere exhibited the best yields with the highest tolerance for attachment pad dimension variation. Conversely, assembly processes using no-clean solder paste with a Nitrogen reflow atmosphere generated the largest number of assembly defects and was found to be the most sensitive to changes in the attachment pad design.