No abstract

No abstract

No abstract

Thermal characterisation of thermal interfaces becomes even tougher a challenge at low bond line thicknesses and higher thermal conductivities of the interface materials as more accurate measurement techniques are required. As in parallel the quest for high conductivity adhesives and greases is ongoing, a correlation between thermal bulk or interface properties and structure is in high demand. We have developed test-stands for various classes of thermal interface materials. These permit characterisation for materials with thin bond line thickness and high thermal conductivity still using steady state techniques. The methods are benchmarked for greases, adhesives and sintered silver. For the latter, the technology development is described. Then, structural features such as particle density and porosity are examined. It will be the aim to compare and correlate them to thermal resistance. Part of the work has been accomplished within the running EU. Project "Nanopack"

The stability of Au20Sn eutectic cap formed during reflow of Sn/Au bump was studied under multiple reflow cycles. For a 5 mu m thick Sn layer, the eutectic caps formed for the bumps of 60 and 40 mu m in diameters were quite stable up to 10 reflows and the zeta compound layer at the interface was a good barrier layer to prevent the exhaustion of the eutectic solders. However for 20 mu m bumps, the relative larger eutectic volume resulted in side wall wetting. Therefore only small part of eutectic alloy was left on the top of the Au socket after one reflow. After three reflows Au socket was almost covered by a single zeta compound layer. The results identified that the maximum cap height formed during reflow should be smaller than half of the bump diameter to maintain it on the Au socket