Mutual capacitance and magnetic field distribution control for transmission lines

A method for forming a circuit board, comprising:

• forming a reference plane layer having opposing first and second surfaces;
• attaching the first surface of a reference plane layer to a first surface of a dielectric material layer having opposing first and second surfaces;
• attaching an electrically conductive trace on the second surface of the dielectric material;
• and
• forming a solder mask layer on the second surface of the dielectric material layer;
• wherein said forming a solder mask layer comprises
• modifying an effective dielectric constant of the solder mask layer to reduce a mutual capacitance between the first trace and a second trace on the second surface of the dielectric material.

A circuit board, comprising:

• a planar dielectric material layer having opposing first and second surfaces;
• a planar reference plane layer having opposing first and second surfaces, wherein the first surface of the reference plane layer is attached to the first surface of the dielectric material layer;
• a first electrically conductive trace on the second surface of the dielectric material;
• and
• an insulating material layer on the second surface of the dielectric material layer that covers at least a portion of the first electrically conductive trace;
• wherein a first portion of the insulating material layer over the first electrically conductive trace includes a first amount of the insulating material, and a second portion of the insulating material layer adjacent to the first portion and between the first electrically conductive trace and a second electrically conductive trace includes a second amount of the insulating material;
• and
• wherein the first amount is greater than the second amount.