Polyimide dielectric layer

A dielectric layer in an electrical device wherein said layer includes a polyimide comprising structural units having pendant fluorene groups, wherein said polyimide structural units have one or both of formulae I and IV ##STR22## wherein each R independently is from 0 to 4 substituents selected from the group consisting of hydrogen, halogen, phenyl, phenyl group substituted by 1 to 4 halogen atoms or alkyl groups having 1 to 10 carbon atoms, and an alkyl group having from 1 to 10 carbon atoms;

• A is a tetrasubstituted aromatic moiety having from 6 to 20 carbon atoms and moieties of Formula II:
• ##STR23## wherein B is a covalent bond, a C(R.sup.2).sub.2 group, a CO group, an O atom, an S atom, an SO.sub.2 group, a Si(C.sub.2 H.sub.5).sub.2 group or an N(R.sup.3).sub.2 group,
• R.sup.2 is H or C(R.sup.4).sub.3 ;
• R.sup.3 is H, an alkyl group having from 1 to 20 carbon atoms, or an aryl group having from 6 to 20 carbon atoms;
• and R.sup.4 is H, fluorine, or chlorine;
• and
• Ar represents a monocyclic or polycyclic aromatic nucleus having from 6 to 20 carbon atoms and moieties of Formula V:
• ##STR24## wherein Ar and B have the meaning described above, and each p is an integer 0 to 10, and
• wherein said polyimide has a dielectric constant of less than 2.75.