Process development and reliability study for 01005 components in a lead-free assembly environment.

摘要

The increasing consumer demand for smaller, lighter and high-function portable electronic devices has challenged electronics manufacturers to creatively arrange circuits and components to support operations, while satisfying cost and manufacturing assembly yield targets.;While 0201 size resistor and capacitor components continue to grow in popularity to meet stricter form factor design constraints, the introduction of 01005 passive components has put forth new challenges from the assembly perspective. Several researchers have developed assembly processes for 01005 components and have recommended the use of nitrogen during reflow for complete coalescence of the solder particles. Since the fluxing action involves the removal of metal oxides, soldering in an inert atmosphere, like nitrogen, minimizes the formation of metal oxide and helps in reducing the workload of fluxes. Thus, soldering in a nitrogen atmosphere improves the wetting of solder and thereby provides a wider reflow profile window. However, soldering in nitrogen introduces manufacturing concerns. The supply and carrying cost of nitrogen and the purity of nitrogen are critical considerations. Furthermore, enhanced wetting in nitrogen increases the potential for tombstoning for smaller components, such as 01005s.;The objective of this research endeavor was to develop a robust assembly process for 01005 components using solder reflow in air along with Type 3 lead free solder paste material using a 4-mil thick stencil.;This effort addresses, in detail, the development of a process for the assembly of 01005 components starting from stencil print characterization, to the pick and place operation, and finally to the reflow process. Designed experiments were used to develop process guidelines for 01005 component assembly. A successful process for assembly of 01005 passives was developed; guidelines towards different printing parameter namely, printing pressure, printing speed, separation speed, aperture shape and aperture size were demarcated. Gang relieved pads were evaluated against the non solder mask defined pads and the latter was chosen due to better gasketting. This was followed by component placement evaluation and reflow profile development. Shorter reflow profile yielded better results compared to longer reflow profile. Finally reliability study was performed, the objective of performing reliability studies was to ensure that the proposed manufacturing process is capable of producing products with acceptable long term reliability.