Flexible interconnect circuits comprising welded connections

A method of fabricating a flexible circuit assembly comprising a stacking axis, the method comprising:

• providing an electrical component subassembly comprising an electrical component and an interconnecting structure, wherein:
• the electrical component comprises a base, a contact pad comprising copper and stacked with the base, and a component opening, extending through each of the base and the contact pad,
• the component opening comprises a largest cross-sectional dimension, perpendicular to the stacking axis, fully overlapping with the interconnecting structure, and
• the interconnecting structure is soldered to the contact pad by a solder patch and comprises one or more materials selected from the group consisting of nickel, brass, and copper;
• aligning a flexible circuit with the electrical component subassembly, wherein:
• the flexible circuit comprises a first insulating layer, a conductive layer, and a second insulating layer,
• the conductive layer comprises aluminum and is stacked between the first insulating layer and the second insulating layer along a stacking axis, and
• the first insulating layer comprises a first-layer opening;
• pressing the conductive layer against the interconnecting structure, wherein:
• the interconnecting structure is stacked between the contact pad and the conductive layer along the stacking axis, and
• at least a portion of the interconnecting structure, which is aligned with the electrical component, directly interfaces the conductive layer;
• and
• welding the conductive layer against the interconnecting structure through the component opening.