A process for the preparation of 7.beta.-acylamino-3-substituted-3-cephem-4-carboxylic acid compounds comprising reacting at -70.degree. C. to 0.degree. C. in an inert organic solvent phosphorus pentachloride with a cephalosporin compound in the presence of an olefinic compound having at least one carbon-carbon double bond having not more than three hydrogen atoms attached thereto capable of removing chlorine at least in part by addition to a carbon-carbon double bond.

In order to form a (flexible) electrical interconnect structure a flexible dielectric substrate having a plurality of windows is laminated between a first, relatively thin flexible conductor layer and a second, relatively thick conductor layer. The first flexible conductor layer is patterned into a plurality of flexible conductor lines The second conductor layer is patterned into first and second pluralities of spaced apart terminals, which overlie the windows. Conductive vias are formed through the flexible dielectric substrate between the terminals and the flexible conductor lines, thereby connecting the terminals on one side of the flexible substrate to the flexible conductor lines on the other side of the substrate .