Multi-Die QFN Leadframe Package for Lower Cost and Better Heat Flow
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Solution Overview
Problem
Existing hybrid packages face challenges with high costs due to expensive package substrates and unsatisfactory thermal performance, while also seeking to reduce overall package height.
Innovation Solution
A multi-die quad-flat no-lead (QFN) hybrid package design featuring a copper leadframe carrier with flip-chip and wire-bonding leads, where two integrated circuit dies are mounted in a flip-chip manner, and a third die is stacked and connected via bond wires, encapsulated within a mold cap with exposed leads for external connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a package substrate is used in hybrid package, then functionality and performance are improved, but manufacturing cost increases
Solution Approach 1:
The patent extracts and removes the expensive package substrate from the hybrid package structure, replacing it with a cost-effective leadframe carrier while maintaining the essential functionality of die stacking and electrical connections
Solution Approach 2:
The patent employs a leadframe carrier as a cost-effective alternative to the expensive package substrate, using a simpler, cheaper structure that accomplishes the same mechanical support and electrical connection functions
2Reliability
If a package substrate is used in hybrid package, then functionality and performance are improved, but thermal performance deteriorates
Solution Approach 1:
The patent removes the package substrate that caused thermal performance issues and replaces it with a leadframe carrier that provides superior thermal conduction pathways from the dies to the external environment
Solution Approach 2:
The patent uses a composite structure combining the leadframe carrier with mold compound, where the metal leadframe provides excellent thermal conduction while the mold compound provides mechanical protection and electrical insulation
3Reliability
If traditional hybrid package structure is used, then functionality is achieved, but package height increases
Solution Approach 1:
The patent transitions from a planar two-dimensional package layout to a three-dimensional stacked configuration, arranging multiple dies vertically on the leadframe carrier to reduce the horizontal footprint and overall package height
Solution Approach 2:
The patent implements a stacked die configuration where the third die is positioned directly over the first and second dies, creating a nested vertical arrangement that minimizes package height while maintaining all necessary electrical connections
Data Source
AI summary
A multi-die QFN hybrid package includes a carrier having flip-chip leads and wire-bonding leads. A first die and a second die are mounted on the flip-chip leads, respectively, in a flip-chip manner. The first die is spaced apart from the second die. A third die is stacked over the first die and the second die. The third die is electrically connected to the wire-bonding leads around the first die and the second die through bond wires. A mold cap encapsulates the first die, the second die, the third die, the bond wires, and partially encapsulates the carrier. The flip-chip leads and the wire-bonding leads are exposed from a bottom mold cap surface.