Doctrine of Equivalents and Sintered Silver (Ag) Paste as Bonding Materials

This chapter revisits the doctrine of equivalents (DOE) by reviewing previoius court cases to summarize and distill the main principles, and then, to select two pairs of US patents in the area of sintered silver (Ag) pastes to demonstrate their applications. The sintered Ag paste formulation is chosen as our case study because of the active patenting activities in the last 5 years. This interest stems from the urgency to find a lead-free bonding material to conform the EU environmental regulations and its excellent thermal-mechanical properties needed in the next generation of microelectronic packaging. This chapter demonstrates the limitations of DOE, and its applicability depends on the factors, such as prosecution history estoppel (PHE), public dedication, all-element rule, prior art, and the classification of nano-Ag materials. This article is expected to be useful for patent attorneys dealing with patent infringement cases related to nano-materials in the USA, as well as scientists and engineers who are working in the manufacturing industry to appreciate the DOE and PHE while analyzing the relevant patents in their job.

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