Electrical properties of epoxy/silver nanocomposites

We investigated the electrical properties of nanocomposites made of epoxy resin filled with 70-nm-sized silver particles. These composites were studied for the fabrication of integrated capacitors in electronics packaging. The dc conductivity was studied as a function of the filler concentration and as a function of temperature. We also studied the ac conductivity and the permittivity in the 10−1–105Hz range as a function of the filler concentration. Experimental properties were analyzed using standard percolation theories. The dc conductivity varies as (ϕ-ϕc)t, where ϕ is the filler concentration, ϕc is the percolation threshold, and t is the dc critical exponent. A very low percolation threshold is obtained (ϕc=1%) which is believed to be related to a segregated distribution of the fillers in the epoxy matrix. We also measured a very high dc critical exponent (t=5) probably related to the interparticle electrical contact. A universal scaling law is observed for σ(ω) and e(ω). Above a cutoff frequency (ω...

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