NOVELTY - A ternary particle size thermally conductive filler composition (F1) with addition of nano particles have composition (c1) comprising controlled particle size ratio and volume percentage ratio as following: large thermally conductive filler, small thermally conductive filler, nano thermally conductive filler; composition (c2) comprising controlled particle size ratio and volume percentage ratio as following: large thermally conductive filler, small thermally conductive filler, nano thermally conductive filler.    USE - A ternary particle size thermally conductive filler composition (claimed) useful for making thermally conductive interface materials such as soil gel, which used for interface heat conducting purpose in applications such as LED, solar cell, microelectromechanical (MEMS) devices, and wind mill, and medical devices.    ADVANTAGE - The composition exhibits improved homogeneity, thermal conductivity and relatively low viscosity. The composition has wide range of thermally conductive filler loading constituted of chemical compounds to generate wide range of thermal conductivity of 4-8 W/mK, with relative low viscosity of less than 350 Pas, low complex storage modulus of less than 100 kPa, and good thermal stability.    DETAILED DESCRIPTION - A ternary particle size thermally conductive filler composition (F1) with addition of nano particles have a) composition (c1) comprising controlled particle size ratio and volume percentage ratio as following: a1) large thermally conductive filler (40-80, preferably 60-65 vol.%) has particle size of 1-10 (preferably 4-8) mu m, a2) small thermally conductive filler (5-30, preferably 10-15 vol.%) has particle size of 0.1-5 (preferably 0.5-2) mu m, a3) nano thermally conductive filler (10-40, preferably 15-30 vol.%) has particle size of 10-800 (preferably 50-300) nm, a4) volume ratio of large thermally conductive filler to small thermally conductive filler is 1:2-20:1 (preferably 2:1-10:1); a5) volume ratio of large thermally conductive filler to nano thermally conductive filler is 1:3-15:1 (preferably 2:3-6:1); a6) volume ratio of small thermally conductive filler to nano thermally conductive filler is 5:1-1:5 (preferably 1:1-1:3); b) composition (c2) comprising controlled particle size ratio and volume percentage ratio as following: b1) large thermally conductive filler (45-75, preferably 58-62 vol.%) has particle size of 20-40 (preferably 23-28) mu m, b2) small thermally conductive filler (5-40, preferably 15-25 vol.%) has particle size of 5-20 (preferably 8-12) mu m, b3) nano thermally conductive filler (10-50, preferably 25-30 vol.%) has particle size of 10-800 (preferably 100-300) nm, b4) volume ratio of large thermally conductive filler to small thermally conductive filler is 1:3-15:1 (preferably 3:2-8:1), b5) volume ratio of large thermally conductive filler to nano thermally conductive filler is 1:2-10:1 (preferably 2:1-5:1); b6) volume ratio of small thermally conductive filler to nano thermally conductive filler is 3:2 to 1:4 (preferably 1:1 to 1:3). INDEPENDENT CLAIMS are included for the following:    (1) a thermally conductive interface material comprising ternary particle size filler compositions (F1) and silicone polymer matrix, where thermally conductive composition (c1) mixed with silicone polymeric liquid matrix to form curable thermally conductive gel (g1), where the thermal gel (g1) comprises 65-95 (preferably 78-90) vol.% conductive filler and 5-40 (preferably 10-22) vol.% polymeric liquid, with viscosity below 350 Pas and complex storage modulus below 100 kPa; and    (2) a single chip module (SCM) or multichip module (MCM) electronic module comprising heat generating electronic component, heat spreader with pedestal and/or heat sink, and substrate with electronic component attached on it, where thermally conductive interface gel (g1) was placed at interfaces between electronic component and heat spreader, and heat spreader and heat sink. The nominal average thickness of an interface is less than or equal to 250 mu m.