Multilayer integrated circuit packages with localized air structures

An integrated circuit package substrate, comprising:

• a plurality of dielectric layers;
• a stripline structure formed in the plurality of dielectric layers, wherein the stripline structure comprises signal conductors formed on at least one of the plurality of dielectric layers and parallel ground planes formed in at least some of the plurality of dielectric layers, and wherein the signal conductors are sandwiched between the parallel ground planes;
• alignment holes formed in at least some of the plurality of dielectric layers;
• and
• alignment pin structures formed in the alignment holes configured to ensure that the ground planes completely overlap with the signal conductors.

A method of forming an integrated circuit package, comprising:

• forming a first dielectric layer;
• forming signal traces on the first dielectric layer;
• forming a second dielectric layer over the first dielectric layer, wherein the second dielectric layer includes a region that is devoid of dielectric material, and wherein the region is formed over the signal traces;
• and
• forming a conductive via through the second dielectric layer.