Low-Temperature Oxidation-Sintering Behaviors of Cu Fine Particles

Cu fine-par t icle paste is a promising material to form a low-cos t i nte rconnect for fle xi ble el ect ronics device s. I t has bee n repo rted that Cu par ticles can be sin tered at l o w temperature (well belo w t he hal f of t h e m el t i n g po i nt ) t hr ou gh t w o-st ep hea t tre a tment proces s es of oxidat ion a n d redu cti on. However, the mechanism of the low temperature sin tering is not clear yet. In t hi s stud y, we i nv esti gat ed the oxidati on sin te ring proces s of Cu fine par t i cl es by t herm al gravimetri c a nal ysi s ( T G A) i n t he temperature range of 200 degrees C WAVE DASH 300 degrees C, X-ray diffraction (XRD), and m icr ostr uc tur al obse r v ation. It wa s found f rom TGA that the oxidation proces s was initially rate-controlled by sur face react ion and t hen by Cu di ffusi on at grai n boundari es of Cu2O. Trans mission electron microscopy obse rvation reve aled the formati on of a c o re ( Cu)-s hell ( Cu2O) str uct ure duri ng t he oxi da tion proces s. The adjace nt Cu2O s hel l s we re bon ded to eac h ot her res ulti ng i n a c ros s-li nked str uc t ure. The subse que nt redu cti o n proces s led t o t he formati on of a poro us str uct ur e by oxygen r emoval, but t he c ros s-li nked str uc t ure wa s maint ai ned, which would make the low-tempera ture sin t ere d Cu body a s robu st as soli dified solde r and sin tered Ag paste.