A chip scale package comprising: - a substrate with a contact pad at a first main surface; and - a flexible interconnect structure, comprising: - a first dielectric layer on top of the first main surface; - a first via electrically contacting the contact pad, the first via extending from the contact pad through the first dielectric layer to a first planar upper main surface of the first dielectric layer; - a planar metal spring on top of the first planar upper main surface electrically contacting the first via at a first end of the planar metal spring; - a second dielectric layer on top of the first dielectric layer and covering the planar metal spring; - a second via electrically contacting at a second end of the planar metal spring, the second via extending from the planar metal spring through the second dielectric layer to a second planar upper main surface of the second dielectric layer; - a second metal on top of the second planar upper main surface and electrically contacting the second via; wherein the first and second dielectric layers (4,7) of the flexible interconnect structure have an elastic modulus below 200MPa; and - a bonding structure on top of the flexible interconnect structure, electrically contacting the second metal; characterized in that the orthogonal projection of the bonding structure on the first main surface overlaps the contact pad. - a substrate with a contact pad at a first main surface; and - a flexible interconnect structure, comprising: - a first dielectric layer on top of the first main surface; - a first via electrically contacting the contact pad, the first via extending from the contact pad through the first dielectric layer to a first planar upper main surface of the first dielectric layer; - a planar metal spring on top of the first planar upper main surface electrically contacting the first via at a first end of the planar metal spring; - a second dielectric layer on top of the first dielectric layer and covering the planar metal spring; - a second via electrically contacting at a second end of the planar metal spring, the second via extending from the planar metal spring through the second dielectric layer to a second planar upper main surface of the second dielectric layer; - a second metal on top of the second planar upper main surface and electrically contacting the second via; wherein the first and second dielectric layers (4,7) of the flexible interconnect structure have an elastic modulus below 200MPa; and - a first dielectric layer on top of the first main surface; - a first via electrically contacting the contact pad, the first via extending from the contact pad through the first dielectric layer to a first planar upper main surface of the first dielectric layer; - a planar metal spring on top of the first planar upper main surface electrically contacting the first via at a first end of the planar metal spring; - a second dielectric layer on top of the first dielectric layer and covering the planar metal spring; - a second via electrically contacting at a second end of the planar metal spring, the second via extending from the planar metal spring through the second dielectric layer to a second planar upper main surface of the second dielectric layer; - a second metal on top of the second planar upper main surface and electrically contacting the second via; - a bonding structure on top of the flexible interconnect structure, electrically contacting the second metal;