Offset Stacked Die IC Package with Leadframe
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Solution Overview
Problem
Current semiconductor packaging technologies face limitations in increasing die density due to space constraints and the need for extra components and assembly steps in same-size die stacking, which result in increased costs and processing times.
Innovation Solution
The implementation of an integrated circuit package system with a leadframe having short and long lead fingers, where a second die is offset and attached over the first die using an adhesive, allowing for direct stacking and simultaneous wire bonding without the need for vertical separation, thus reducing package size and manufacturing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If same-size die stacking is used to increase die density, then the number of chips per package is increased, but extra pillars and assembly steps are required which increase manufacturing complexity and cost
Solution Approach 1:
The patent removes the unnecessary pillars from the die stacking structure. By directly attaching the second die to the leadframe lead fingers without intermediate pillars, the manufacturing process is simplified while maintaining the ability to stack multiple dies vertically, thus increasing die density without the added complexity of pillar fabrication and assembly
Solution Approach 2:
The patent combines the functions of mechanical support and electrical connection into a single integrated structure. The leadframe lead fingers serve both as structural supports for stacking dies and as electrical connection paths, eliminating the need for separate pillars and reducing the number of assembly steps
2Reliability
If vertical separation is provided between stacked dies to accommodate wire bonds, then wire bonding is enabled, but the vertical height of the package increases reducing density
Solution Approach 1:
The patent transitions the wire bonding approach from vertical wire routing (which requires vertical space) to horizontal wire routing along the leadframe plane. The bond wires extend horizontally from the die bond pads to the leadframe lead fingers, allowing dies to be stacked with minimal vertical separation while maintaining reliable electrical connections
3Quantity of substance
If more components and assembly steps are added to achieve same-size die stacking, then die density is increased, but manufacturing time and cost increase
Solution Approach 1:
The patent performs preliminary actions by pre-forming the leadframe with integrated lead fingers that are positioned and configured before die attachment. The lead fingers are pre-bent and pre-positioned to receive the dies directly, eliminating the need for post-attachment pillar installation and alignment operations, thus reducing manufacturing steps and time
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables a more compact and cost-effective packaging design with increased die density, reducing the vertical size of the package and simplifying the manufacturing process while maintaining access for electrical connections.
Implementation Method 1
The offset second die is attached over the first die and the long lead finger with an adhesive
Data Source
AI summary
An integrated circuit package system provides a leadframe having a short lead finger and a long lead finger, and the long lead finger and the short lead finger reside substantially within the same horizontal plane. A first die is placed in the leadframe. A second die is offset from the first die. The offset second die is attached over the first die and the long lead finger with an adhesive. The first die is electrically connected to the short lead finger. The second die is electrically connected to at least the long lead finger or the short lead finger. At least portions of the leadframe, the first die, and the second die are encapsulated in an encapsulant.