Stackable Low-Profile Lead Frame Package Without Paddle
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Solution Overview
Problem
Current stacked integrated circuit (IC) packaging technologies face challenges in achieving low profile, cost-effectiveness, and efficient airflow for cooling, especially when stacking multiple die, as they often require increased package thickness and are not suitable for applications requiring minimal height and high functionality in a small footprint.
Innovation Solution
A low profile IC package design using a lead frame with inwardly extending metal I/O leads and bump features that allow for efficient encapsulation and stacking without a paddle, enabling the use of existing assembly infrastructure, reducing material costs, and allowing for easy testing and burn-in before assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional lead frame packages with paddles are used for stacking, then the package can accommodate larger numbers of die, but the package thickness increases and cross section profile increases, preventing sufficient airflow for cooling
Solution Approach 1:
The invention removes the paddle component from the lead frame package structure. By extracting the paddle, the package thickness is significantly reduced while maintaining the ability to stack multiple die. The lead frame directly supports the die without requiring an additional paddle layer, enabling low-profile stacking configurations that allow sufficient airflow for cooling while still accommodating multiple die.
Solution Approach 2:
The invention transitions from a traditional three-dimensional package structure with paddles extending outward to a flattened, two-dimensional lead frame configuration. This dimensional change allows the package to maintain structural integrity and stacking capability while minimizing thickness in the vertical dimension, enabling better airflow pathways for thermal management.
2Volume of moving object
If stacked IC packages are designed with minimal height, then the footprint is reduced, but existing assembly infrastructure cannot be utilized and manufacturing complexity increases
Solution Approach 1:
The lead frame package structure is designed to be universally compatible with existing assembly infrastructure while enabling low-profile stacking. The standardized lead frame configuration can be processed by conventional assembly equipment, and the same structure supports both traditional and stacked package configurations, making the manufacturing process adaptable without requiring entirely new infrastructure.
Solution Approach 2:
The invention modifies key structural parameters of the lead frame package, specifically reducing the vertical height parameter while maintaining horizontal dimensions compatible with existing assembly tools. By changing the thickness parameter and removing the paddle component, the package achieves minimal height while remaining manufacturable with current infrastructure through adjusted processing parameters.
3Volume of moving object
If small I/O terminals are used in lead frame packages, then the package size is reduced, but reliable capture of leads in resin becomes difficult and leads may be inadvertently removed
Solution Approach 1:
The lead frame structure incorporates asymmetric design elements where the lead configuration and anchoring features are specifically shaped to provide reliable mechanical interlocking with the resin encapsulant. The leads are formed with specific geometries that create friction and mechanical resistance against inadvertent removal, while the asymmetric arrangement optimizes the capture mechanism for small terminal dimensions.
Solution Approach 2:
The leads are formed with curved or rounded terminations rather than sharp edges, creating a spheroidal geometry that enhances resin capture. The curved surfaces allow the resin to flow around and mechanically lock onto the leads more effectively, providing reliable anchoring for small I/O terminals while maintaining compact package dimensions.
Data Source
AI summary
In an embodiment, an IC assembly comprises an IC having a top surface comprising a plurality of input/output terminations, a plurality of leads arranged around the IC, a plurality of bond wires, and an encapsulant. Each lead has a first surface and a second surface opposite the first surface, and has a feature protruding from the first surface proximate an inward end of the lead nearest the IC. The feature extends from the first surface to approximately a plane that includes a bottom surface of the IC. Each bond wire connects a respective lead to a respective I/O terminal on the IC. The encapsulant seals the bond wires, the IC, and a first portion of the leads that includes the feature. The feature creates on offset from the bottom of the IC to permit the encapsulant to surround the first portion.