Patent Landscape of sintered Cu and Ag as Die-Attach Materials in Microelectronics Packaging

This research provided the latest development of sintered silver (Ag) and copper (Cu) as die-attach materials based on the patent data retrieved from www.lens.org using the two criteria of patent claims of “silver” or “copper”, “sinter*” and cooperative patent classification (CPC) of H01L2224/8384 (die-attach application with sintering technique). Based on these two criteria, the patent filing trend of sintered Cu mirrored those of sintered Ag, including the peak in 2015. Closer data inspection revealed that this mirroring reflected the patent claims technique, which included Cu and Ag, and sometimes other elements, such as gold, nickel, palladium, aluminium and platinum, as metal particles to be sintered for die-bonding applications. At the same time, patents that claimed either the Cu or Ag exclusively for their paste formulation or used these sintered joints as part of the microelectronic packaging designs, were also available, but generally restricted to sintered Ag joints. However, the obviousness or “equivalences” between sintered Cu and Ag in the patent prosecution process might pose a problem in patent infringement cases, but none had been reported. In addition, other “valuable” patents based on patent family size and forward-citations counts, were also identified and discussed in developing these sintered metal technologies. In conclusion, the rapid development of sintered Ag and Cu as die-attach joints in the microelectronic packaging industry, especially among power module manufacturers, had matured in their technology life-cycle, based on the patent filing data.