In accordance with the invention, {HEAD ~ a low dielectric constant insulation material} is provided which comprises a porous insulation layer, preferably sandwiched between {TAIL ~ non porous upper and lower insulation layers} 
In accordance with the invention , { HEAD ~ a low dielectric constant insulation material } is provided which comprises a porous insulation layer , preferably sandwiched between { TAIL ~ non porous upper and lower insulation layers }
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