A ground isolation transmission line package device includes (1) ground isolation planes between, (2) ground isolation lines surrounding, or (3) such ground planes between and such ground isolation lines surrounding horizontal data signal transmission lines (e.g., metal signal traces) that are horizontally routed through the package device. The (1) ground isolation planes between, and/or (2) ground isolation lines electrically shield the data signals transmitted in signal lines, thus reducing signal crosstalk between and increasing electrical, isolation of the data signal transmission lines. In addition, data signal transmission lines may be tuned using eye diagrams to select signal line widths and ground isolation line widths that provide optimal data transmission performance. This package device provides higher frequency and more accurate data signal transfer between different horizontal locations of the data signal transmission lines, and thus also between devices such as integrated circuit (IC) chips attached to the package device.