DFN Package Internally Extended Leads Flexible Bonding

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Solution Overview

Problem

Conventional Dual Flat No-Lead (DFN) packaging solutions lack flexible connection options when electrically connecting an IC die to a leadframe cell during assembly.

Innovation Solution

The DFN package design incorporates internally extended package leads that physically and electrically connect from one edge of the package to the opposite edge, terminating at the leadframe edges, with full or reduced leadframe thickness, and are connected to a tie-bar feature for stability and electrical connectivity, allowing for flexible bonding without additional components or costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional DFN packaging solutions are used, then the package structure is simple and assembly is straightforward, but flexible connection options for electrically connecting IC die to leadframe cell are not provided

Engineering Contradiction:

Improveconnection flexibilityVSAvoidpackage structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The leadframe is segmented into multiple cells, with each cell containing extended package leads that can be independently configured. This segmentation allows flexible connection options for each die while maintaining a relatively simple overall package structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Package leads are extended from the traditional peripheral configuration into the internal area of the package, creating additional connection paths in the horizontal dimension. This allows wire bonds to reach bond pads more directly without requiring additional external routing components.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If extended package leads are added to provide flexible bonding, then connection flexibility improves, but package complexity and potential cost increase

Engineering Contradiction:

Improvebonding flexibilityVSAvoidleadframe configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The extended package leads serve multiple functions: they provide mechanical support for the die, establish electrical connections, and enable flexible wire bonding paths. This multi-functionality achieves bonding flexibility without proportionally increasing package complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The extended package leads are integrated within the existing leadframe cell structure, nesting the additional functionality inside the conventional package footprint. This allows flexible bonding capabilities without adding external components or increasing overall package dimensions.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Adaptability or versatility

If additional routing dies or parts are added for flexible bonding, then connection options improve, but package cost and assembly complexity increase

Engineering Contradiction:

Improvebond-out optionsVSAvoidadditional components

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The functionality previously requiring external routing dies or additional parts is extracted and integrated directly into the leadframe structure through extended package leads. This eliminates the need for separate components while providing flexible bond-out options.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The leadframe structure itself provides the routing and connection functionality through its extended leads, making the system self-sufficient. No external routing components are needed as the leadframe performs both structural and electrical routing functions.

Inventive Principle:

Principle #25Self-service

4Strength

If extended package leads with full leadframe thickness are used, then structural strength is maintained, but manufacturing complexity increases

Engineering Contradiction:

Improveleadframe structural integrityVSAvoidleadframe fabrication

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

Different regions of the leadframe have different thicknesses optimized for their specific functions: full thickness in areas requiring structural strength and electrical connectivity, and reduced thickness in areas where flexibility and wire bonding access are prioritized. This localized differentiation maintains strength where needed while simplifying manufacturing overall.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS8174099B2Leadless package with internally extended package leads

Publication Date: 2012.05.08 ATMEL CORP

AI summary

A DFN package includes internally extended package leads. One or more package pads are physically and electrically extended from a first edge of the package to a second, opposite edge of the package. These extended package leads can terminate at the edges of the leadframe. The package pads and the extended package leads where the IC die is attached can have full leadframe thickness. Other extended package lead features can have a reduced leadframe thickness (e.g., about half the leadframe thickness). Leadframe features can be physically and electrically connected to a tie-bar feature which can be an integral part of a leadframe matrix. The tie-bar can stabilize the leadframe features during assembly. The tie-bar can also provide electrical connectivity for post assembly leadframe plating. The tie-bar can be removed during package singulation by sawing or punching techniques to free the leadframe features both physically and electrically.