Flip-chip QFN structure using etched lead frame

A lead frame, comprising:

• a plurality of monolithic lead fingers extending in a plane of the lead frame, each lead finger having a fan-out portion and a chip connection portion,
• each fan-out portion extending in the lead frame plane, the fan-out portions having first and second opposed surfaces and a first thickness in a first direction between the opposed surfaces,
• each chip connection portion extending in the lead frame plane, the chip connection portions having a second thickness smaller than the first thickness, the chip connection portions defining a recess below the first surface,
• wherein the chip connection portions have bumps integral therewith projecting in the first direction from the chip connection portions, the chip connection portions and the bumps being formed of the same material.

A method of fabricating a lead frame, comprising:

• removing material from a metal element to form a plurality of monolithic lead fingers extending in a plane of the metal element,
• the lead fingers having fan-out portions and chip connection portions extending from the fan-out portions,
• the fan-out portions having first and second opposed surfaces and a first thickness in a first direction between the opposed surfaces, and
• the chip connection portions having a second thickness in the first direction, the second thickness smaller than the first thickness, and the chip connection portions defining a first recess below the first surface and a second recess below the second surface, the chip connection portions including first and second subsets of chip connection portions, the first subset being longer than the second subset.

A method of fabricating a lead frame, comprising:

• removing material from a metal element to form a plurality of monolithic lead fingers extending in a plane of the metal element,
• the lead fingers having fan-out portions and chip connection portions extending from the fan-out portions,
• the fan-out portions having first and second opposed surfaces and a first thickness in a first direction between the opposed surfaces, and
• the chip connection portions having a second thickness in the first direction, the second thickness smaller than the first thickness and defining a recess below the first surface,
• wherein the step of removing material forms the chip connection portions having bumps integral therewith projecting in the first direction from the chip connection portions, the chip connection portions and the bumps being formed of the same material.

A method of fabricating a microelectronic unit, comprising:

• joining contacts of a first device chip with chip connection portions of lead fingers of a lead frame, the first device chip having a plurality of at least one of passive devices or active devices, the contacts of the first device chip facing the chip connection portions;
• and
• joining contacts of a second device chip with the chip connection portions of the lead fingers of the lead frame,
• wherein at least a portion of a thickness of the first device chip extends within a first recess defined by the chip connection portions, and at least a portion of a thickness of the second device chip extends within a second recess defined by the chip connection portions,
• wherein the lead fingers further include fan-out portions extending in a lead frame plane from the chip connection portions, the fan-out portions having first and second opposed surfaces, the first recess extending below the first surface and the second recess extending below the second surface, and
• wherein the fan-out portions have a first thickness in a first direction between the opposed surfaces, and the chip connection portions have a second thickness in the first direction smaller than the first thickness.