Nanostructured fumed metal oxides for thermal interface pastes

2008

Journal of Elec Materi

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A paste in the form of a polyol ester vehicle (liquid) containing 0.6 vol.% nanoclay is an effective thermal interface material. Nanoclay with a high conformability and hence a small bond line thickness is preferred, namely montmorillonite containing a quarternary ammonium salt organic modifier (dimethyl dehydrogenated tallow) at 125 meq/100 g clay, after exfoliation by using the vehicle. When it is used between smooth (0.009 lm) copper surfaces at a pressure of 0.69 MPa, the thermal contact conductance reaches 40 9 10 4 W/m 2 K, in contrast to the corresponding values of 28 9 10 4 W/m 2 K, 28 9 10 4 W/m 2 K, 25 9 10 4 W/m 2 K, and 24 9 10 4 W/m 2 K previously reported for carbon black, fumed alumina, fumed zinc oxide, and graphite nanoplatelet pastes. Between rough copper surfaces (12 lm), the conductance provided by the nanoclay paste is slightly below those of the other pastes. The superiority of the nanoclay paste for smooth surfaces is attributed to the submicron bond line thickness; the inferiority for rough surfaces is due to the low thermal conductivity. The conductance provided by the nanoclay paste increases from 31 9 10 4 W/m 2 K to 40 9 10 4 W/m 2 K when the pressure is increased from 0.46 MPa to 0.92 MPa. This pressure dependence is stronger than that of any of the other pastes studied.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nanoclay Paste as a Thermal Interface Material for Smooth Surfaces

Lin

2008

Journal of Elec Materi

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“…2,3,[5][6][7]10,50 ) also tested between copper surfaces with the same surface roughness and same contact pressures as in this work. The other TIM materials include thermal pastes, unmodified flexible graphite, thermal-paste-penetrated flexible graphite, thermal-paste-coated flexible graphite, and thermal-paste-coated metal foils.…”

Section: Comparison With Prior Workmentioning

confidence: 99%

“…The comparison involves a large variety of TIMs, due to the extensive prior work of one of the authors (D.D.L.C.). [1][2][3][4][5][6][7]10,11,20,21 EXPERIMENTAL PROCEDURES…”

Section: à6mentioning

confidence: 99%

“…Silver particles, 2,3 carbon black, [4][5][6] and graphite nanoplatelets 7,8 are effective particles for formulating thermal pastes. Due to the attraction of a paste that is electrically nonconductive, zinc oxide particles 9 and fumed alumina particles 10 are also used to formulate thermal pastes. Carbon black and fumed alumina have the particular advantage of compressibility (squishability), which results from the fact that they are in the form of porous aggregates of nanoparticles.…”

Section: Introductionmentioning

confidence: 99%

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Solder–Graphite Network Composite Sheets as High-Performance Thermal Interface Materials

Sharma

2015

Journal of Elec Materi

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Low-cost solder-graphite composite sheets ( ‡55 vol.% solder), with solder and graphite forming interpenetrating networks to a degree, are excellent thermal interface materials (TIMs). Solders 63Sn-37Pb and 95.5Sn-4Ag-0.5Cu are separately used, with the latter performing better. In composite fabrication, a mixture of micrometer-size solder powder and ozone-treated exfoliated graphite is compressed to form a graphite network, followed by fluxless solder reflow and subsequent hot pressing to form the solder network. The network connectivity (enhanced by ozone treatment) is lower in the through-thickness direction. The electrical conductivity obeys the rule of mixtures (parallel model in-plane and series model through-thickness), with anisotropy 7. Thermal contact conductance £26 9 10 4 W/(m 2 K) (with 15-lm-roughness copper sandwiching surfaces), through-thickness thermal conductivity £52 W/ (m K), and in-plane thermal expansion coefficient 1 9 10 À5 /°C are obtained. The contact conductance exceeds or is comparable to that of all other TIMs, provided that solder reflow has occurred and the composite thickness is £100 lm. Upon decreasing the thickness below 100 lm, the sandwich thermal resistivity decreases abruptly, the composite through-thickness thermal conductivity increases abruptly to values comparable to the calculated values based on the rule of mixtures (parallel model), and the composite-copper interfacial thermal resistivity (rather than the composite resistivity) becomes dominant.

Performance of Thermal Interface Materials

2022

Small

The thermal interface materials (TIMs) used for improving thermal contacts are considered in terms of the performance, performance consideration criteria, performance evaluation methods, and material development approaches. The performance is described mainly by the thermal contact conductance, which refers to the conductance across the thermal contact surfaces that sandwiches the TIM. This conductance depends on the conformability, thermal conductivity, and small‐thickness feasibility. However, the vast majority of published work does not consider this conductance, but only the thermal conductivity within the TIM. The highest TIM performance is exhibited by the thermal pastes and low‐melting alloys.