Methods and Apparatus for Transmission Lines in Packages

A method comprising:

• forming a first insulator layer over a first substrate, the first substrate having a redistribution line;
• forming a micro-bump layer over the first insulator layer, the micro-bump layer comprising a first micro-bump line and a micro-bump structure, wherein the first insulator layer is interposed between the redistribution line and the first micro-bump line, each of the first micro-bump line and the micro-bump structure comprising one or more metallic layers and a solder layer on the one or more metallic layers, wherein the one or more metallic layers is interposed between the solder layer and the first insulator layer;
• bonding a second substrate to the micro-bump structure by the solder layer of the micro-bump structure;
• and
• placing an underfill between the first micro-bump line and the second substrate, the underfill completely separating the first micro-bump line and the second substrate.

A method comprising:

• forming a redistribution line on a first substrate;
• a first insulator layer over the redistribution line;
• forming one or more micro-bump lines;
• forming a micro-bump structure, wherein each of the one or more micro-bump lines and the micro-bump structure have a same conductive layer structure, wherein the conductive layer structure of both the one or more micro-bump lines and the micro-bump structure comprises a solder layer;
• attaching a second substrate to the micro-bump structure by the solder layer of the micro-bump structure;
• and
• placing an underfill between the micro-bump line and the second substrate, wherein the underfill extends closer to the second substrate than the one or more micro-bump lines.