ANNEALING BEHAVIOR OF FINE-GRAINED ELECTROLESS COPPER-DEPOSITS

An investigation was conducted to examine the low temperature (<300-degrees-C) annealing behavior of two types of fine-grained electroless copper deposits. Heat-treatment from continuous oven-annealing was compared to that from thermal cycling in a fluidized sandbath (FSB) unit. It was found that one of the deposits, referred to as type IV electroless copper, showed considerable resistance to recrystallization. Microscopic and chemical analyses indicated that this electroless copper contained a high density of organic inclusions which were effective in pinning grain boundary movement and preventing recrystallization. Type IV electroless cop er also had high gaseous hydrogen content. The FSB experiments showed that this entrapped hydrogen could induce a local plastic deformation mechanism and cause internal fatiguing in the copper during thermal cycling. The other deposit, referred to as type I electroless copper, was relatively free of foreign incorporation. This copper recrystallized readily upon annealing. The driving force for grain growth was the surface energy released from elimination of grain boundaries.