When heated, neat or in hydrocarbon solvent, cis,trans-\,3-cyclooctadiene underwent both dimerization and isomerization. The structures of the 2 + 2 cyclodimers were assigned as the trans.cis, trans.trans, and cis,cis dimers. The ratio of the three dimers was found to be independent of the reaction temperature. The reaction followed good second-order kinetics and has /í* = 19 kcal/mol and 5+ = -10 eu. The results have been rationalized on the basis of a stepwise mechanism for dimer formation.he concerted, suprafacial, thermal fusion of two olefins to form a cyclobutane ring is a symmetryforbidden process.4 In accord with this prediction, thermal "1,2" cycloadditions of simple olefins have been shown to involve diradical intermediates.5 Thermal cycloaddition can, in theory, proceed in a concerted symmetry-allowed fashion by a (tt2s + ir2a) combination of the two 7 bonds.4 The high degree of stereospecificity in the 2 + 2 cycloaddition of olefins with alienes,6-12 ketenes,13-19 and reactive isocyanates20'21 points toward the possibility that these reactions are concerted. It appears that a cumulative -bond system can function more readily as a Tr2a donor than an isolated double bond. Orbital symmetry theory applied to the concerted fragmentation of cyclobutane demands that the process occur via the (

The peracid oxidation of 7-substituted norbornadienes has been found to afford exo-4,endo-6-disubstituted bicyclo[3.1.0]hex-2-enes. The photo-and thermal chemistry of eav-4-methylbicy clo [3.1.0]hex-2-ene-encfc>-6carboxaldehyde (10) has been studied. The photolysis of 10 results in photoepimerization by external cyclopropyl bond cleavage whereas the thermolysis proceeds predominantly by a suprafacial homo [1,7] hydrogen shift.

The reaction of norbornenone and morpholine without an acid catalyst results in formation of a tricycloenamine, a normal enamine, an enamine reduction product, and an amino ketone. The amino ketone is apparently formed via a homoenolate ion. Treatment of bicyclo[2.2.2] oct-5-en-2-one with morpholine and an acid catalyst gives the thermodynamic product, A'-phenylmorpholine, in refluxing xylene and the kinetic product, 2-Ar-morpholinobicyclo[2.2.2]octa-2,5-diene, at room temperature.

The complexity of microelectronic circuits, their scale of integration, and clock speed re quirements have been increasing steadily. All of these changes have the effect of increasing the power density of the micro-circuits. IC's with a power of several watts and area of over a square centimeter are quite common. Thus, there is more heat generated per device at die, component, and substrate-attach levels of electronic packaging.In order to maintain reliability of finished products, the junction temperature of the con stituent devices must be kept low. It has been demonstrated that thermal management can be one key to lowering the cost and increasing the performance life of microelectronic products. The cost effectiveness of lowering device temperature has been demonstrated to be dramatic in comparison to the cost of thermal management materials(l,2).Proper thermal management of advanced microelectronic devices has to be addressed at all levels. One should address the problem from the basic level of die-attach, through com ponent attach, and eventually substrate-attach to thermal drains.Thermal management is almost invariably coupled with a thermally induced stress problem. The increase in temperature at the device level also means a larger fluctuation of tempera ture from the ambient. Each cycle of on-off for the device represents one thermal cycle. Stress induced failures due to coefficient of thermal expansion (CTE) mismatch is much more acute for higher power devices.In this paper, we will also address the thermally induced stress on the microelectronic product at all levels of packaging with major emphasis on component and substrate levels.We will demonstrate various ways and examples of reducing or eliminating this stress, which is a major cause of device failures. One of the proven methods is through the use of low Tg epoxies with high thermal stability.

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