ASICS face to face self assembly

A die structure, comprising:

• a first semiconductor die including a first surface and a second surface opposite the first surface, the first semiconductor die including sidewalls extending between the first and second surfaces;
• conductive ink printed traces including a first group of the conductive ink printed traces on the first surface of the first semiconductor die, the first group of conductive ink printed traces having a first thickness extending outward from the first surface, a second group of the conductive ink printed traces on the second surface of the first semiconductor die, and a third group of the conductive ink printed traces on the sidewalls of the first semiconductor die;
• conductive ink printed contacts on the first surface of the first semiconductor die, the conductive ink printed contacts having a second thickness extending outward from the first surface, the second thickness being greater than the first thickness;
• a second semiconductor die having a first surface and a second surface, the first surface of the second semiconductor die facing the first surface of the first semiconductor die and including a plurality of conductive traces on the first surface of the second semiconductor die;
• and
• an anisotropic conductive paste positioned between the first surfaces of the first semiconductor die and the second semiconductor die, the anisotropic conductive paste including an encapsulant and a plurality of magnetic beads extending through the encapsulant to electrically couple the conductive traces on the first surface of the second semiconductor die and the conductive ink printed contacts on the first surface of the first semiconductor die, the encapsulant of the anisotropic conductive paste covering the third group of the conductive ink printed traces on the sidewalls of the first semiconductor die except for a first portion of the third group of the conductive ink printed traces exposed from the encapsulant as a sidewall contact, the sidewall contact being more adjacent to the second surface of the first semiconductor die than to the first surface of the first semiconductor die.

A method, comprising:

• forming a plurality of trenches in a first surface of a first wafer, the first wafer including a first surface and a second surface opposite the first surface and each of the plurality of trenches extending from the first surface partially towards the second surface;
• printing a plurality of conductive ink contacts on the first surface of the first wafer, each of the plurality of conductive ink contacts having a first thickness;
• printing a plurality of conductive ink traces in the plurality of trenches and on the first surface of the first wafer, the plurality of conductive ink printed traces including a first group of the conductive ink printed traces on the first surface of the first wafer and electrical contact with but not overlying some of the plurality of conductive ink contacts, each of the plurality of conductive ink printed traces having a second thickness that is less than the first thickness, and the plurality of conductive ink traces including a second group of the conductive ink printed traces in the plurality of trenches;
• dispensing an anisotropic conductive paste on the first surface of the first wafer and on the printed plurality of conductive ink traces, the anisotropic conductive paste including an encapsulant and a plurality of electrically conductive and magnetic beads, the anisotropic conductive paste filling the plurality of trenches over the plurality of conductive ink traces printed in the plurality of trenches;
• placing a second wafer on the dispensed anisotropic conductive paste, the second wafer including a first surface facing the anisotropic conductive paste and including a plurality of traces on the first surface of the second wafer;
• applying a magnetic field to the first and second wafers and the anisotropic conductive paste to align the plurality of magnetic beads to form electrical connections between the plurality of conductive ink contacts on the first surface of the first wafer and the plurality of traces on the first surface of the second wafer;
• curing the anisotropic conductive paste;
• and
• forming a die by cutting the first and the second wafers through a first trench of the plurality of trenches, a sidewall of the die including the anisotropic conductive paste and an exposed portion of at least one of the plurality of conductive ink traces printed in the first trench.