The use of magnesium oxide (MgO) as a filler in an epoxy molding compound (EMC) was considered to identify the maximum thermal conductivity that could be achieved without compromising rheological or processing control and processing flexibility. MgO is an attractive candidate filler for EMCs used in automotive and other applications because MgO is inexpensive, electrically insulative, has relatively high thermal conductivity, is nontoxic, and is a relatively soft filler material meaning it will be less abrasive to surfaces it contacts during its processing and shape molding. A maximum bulk thermal conductivity of 3 W/mK was achieved with a 56% volume fraction of MgO filler. This 56 vol% MgO-filled EMC has a thermal conductivity approximately twice that of traditional silica-filled EMCs with the same volume fraction of filler and has equivalent electrical insulative, thermal expansion, and water absorption characteristics. It is concluded that if a thermal conductivity greater than 3 W/mK is needed in an EMC, then a much more expensive filler material than MgO must be used.Index Terms-Epoxy molding compound (EMC), fillers, magnesium oxide (MgO), original equipment manufacturer, thermal conductivity, thermal management.

During the dissolution process, polymer in the glassy state is, transported into a dilute solution. In some cases, a transition layer can be measured using laser interferometry. This layer is seen as a difference in reflected light intensity between the bare substrate and the maximum during dissolution. When poly(methyl methacrylate) dissolves in methyl ethyl ketone, the layer is not detectable below a polymer number‐average molecular weight of about 30,000. The layer becomes more pronounced as molecular weight of polymer increases.

SynopsisThe technique of laser interferometry is now used routinely by the microelectronics industry for the measurement of the dissolution rates of thin polymer films. In addition to the rate of dissolution, laser interferometry can also provide quantitative information on the thickness of the transition layer between the dissolving glassy polymer and the liquid solvent. This paper describes how observed patterns of reflected light intensity may be analyzed to calculate the thickness of the transition layer for polymers that dissolve with little or no swelling. The technique requires knowledge of the shape of the concentration profile in the transition layer. However, by assuming various simple model profiles one may obtain a reasonable estimate. Experimental measurements of poly(methy1 methacrylate) (PMMA) films dissolving in methylethyl ketone indicate transition layers of thicknesses 0 to 0.1 pm for PMMA of molecular weights Mu, = 37,000 to 1,400,000.

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