Nonlinear Die Attach Pad Linking Structure for Coplanarity

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Solution Overview

Problem

Existing lead frame designs face issues with non-coplanarity of die attach pads due to thermal expansion, warpage, and internal stress during the molding process, leading to mold flash and prevention of electrical connections.

Innovation Solution

A lead frame with a nonlinear die attach pad linking structure comprising interconnected segments attached at angles, such as a zigzag shape, which absorbs stresses and prevents die attach pads from moving out of plane, ensuring coplanarity and minimizing mold flash.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a direct linear connection is used between die attach pads, then structural simplicity is improved, but coplanarity stability deteriorates due to thermal expansion and warpage

Engineering Contradiction:

Improvelinking structure complexityVSAvoidcoplanarity of die attach pads

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent applies curvature by replacing straight linear connections with nonlinear curved linking structures. The curved geometry allows the linking structure to flex and absorb thermal expansion stresses while maintaining coplanarity of the die attach pads during the molding process.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The patent changes the geometric parameters of the linking structure from linear to nonlinear configurations. This parameter change enables the structure to accommodate dimensional changes during molding while preserving pad coplanarity, resolving the contradiction between structural simplicity and manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If rigid linear connections are used between die attach pads, then structural stability is improved, but adaptability to thermal stress deteriorates

Engineering Contradiction:

Improvestructural stability of lead frameVSAvoidresponse to thermal expansion

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The patent transforms the rigid static linear connection into a dynamic nonlinear structure that can adapt its configuration in response to thermal stresses. The curved geometry allows controlled deformation during molding while maintaining overall structural stability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent modifies the geometric parameters of the linking structure to enable controlled deformation under thermal stress. The nonlinear geometry provides parameter flexibility that allows the structure to absorb expansion forces while maintaining structural integrity.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If linear tie bar structures are used, then ease of manufacture is improved, but reliability of coplanarity maintenance deteriorates under molding stress

Engineering Contradiction:

Improvefabrication of linking structureVSAvoidcoplanarity maintenance under stress

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies curved geometries to the tie bar structures, which maintain ease of manufacture through standard fabrication processes while significantly improving their ability to absorb molding stresses and maintain pad coplanarity during the molding process.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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

The nonlinear die attach pad linking structure effectively maintains coplanarity of die attach pads under stress, preventing mold flash and ensuring reliable electrical connections by absorbing thermal expansion and internal stress through flexible deformation.

Implementation Method 1

the segments are attached to each other at an angle such as in a zigzag shape... absorbs stresses and prevents die attach pads from moving out of plane... absorbing thermal expansion and internal stress through flexible deformation

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

The nonlinear DAP linking structure includes two or more interconnected segments, wherein the segments are attached to each other at an angle such as in a zigzag shape... effectively maintains coplanarity of die attach pads under stress... through flexible deformation

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS20230197579A1Nonlinear structure for connecting multiple die attach pads

Publication Date: 2023.06.22 TEXAS INSTRUMENTS INC

AI summary

An integrated circuit package includes a first die attach pad (DAP) having a first bottom surface, a first semiconductor die attached to the first DAP, a second DAP having a second bottom surface, wherein the first bottom surface and the second bottom surface are coplanar, and a second semiconductor die attached to the second DAP. A nonlinear DAP linking structure couples the first DAP to the second DAP, wherein the DAP linking structure does not include any direct linear connections between the first DAP and the second DAP. The nonlinear DAP linking structure is configured to deform without causing the first DAP and the second DAP to become non-coplanar. A mold compound covers the first and second DAPs, the first and second semiconductor dies, and the nonlinear DAP linking structure.