Leadframe Die Pad Groove for Adhesive Flow Control

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Solution Overview

Problem

Roughened leadframe surfaces in semiconductor packages facilitate excessive flow of die attach adhesive and resin bleed, leading to reduced fillet height and increased susceptibility to delamination, compromising the reliability and robustness of the semiconductor packages.

Innovation Solution

Incorporating a groove on the leadframe pad surface that restricts the flow of die attach adhesive and resin bleed, thereby maintaining a controlled adhesive thickness and enhancing adhesion between the leadframe and mold compound.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the leadframe surface is roughened to improve adhesion between the leadframe and mold compound, then adhesion is improved, but die attach adhesive flows excessively and fillet height is reduced

Engineering Contradiction:

Improveadhesion between leadframe and mold compoundVSAvoidfillet height of die attach adhesive

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The leadframe surface is segmented into two distinct zones: a roughened surface area for improved adhesion and a smooth groove area for adhesive flow control. This segmentation allows the package to simultaneously achieve both improved adhesion and controlled fillet height by assigning different surface properties to different functional regions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different surface qualities are applied to different locations on the leadframe pad. The groove portion maintains a smooth surface to restrict adhesive flow and maintain fillet height, while the surrounding pad area has a roughened surface to enhance adhesion between the leadframe and mold compound.

Inventive Principle:

Principle #3Local quality

2Reliability

If the leadframe surface is roughened to enhance adhesion, then adhesion is improved, but resin bleed increases

Engineering Contradiction:

Improveadhesion between leadframe and mold compoundVSAvoidresin bleed from die attach adhesive

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The leadframe surface is divided into functional zones where the groove acts as a barrier to resin bleed while the roughened surrounding area provides adhesion. This segmentation contains the harmful resin bleed effect within the groove area while preserving adhesion benefits in the roughened zones.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The groove serves as an intermediary structure that mediates between the conflicting requirements of adhesion and resin bleed control. It acts as a physical barrier that restricts resin flow while allowing the roughened surface to provide adhesion in adjacent areas.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If a groove is added to the leadframe pad to restrict adhesive flow, then fillet height is improved, but device complexity increases

Engineering Contradiction:

Improvefillet height of die attach adhesiveVSAvoidleadframe surface structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The groove structure segments the pad surface into functional zones, achieving adhesive flow control through a relatively simple geometric modification rather than requiring complex multi-component structures. This segmentation approach maintains manufacturing simplicity while achieving the desired flow restriction.

Inventive Principle:

Principle #1Segmentation

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 groove on the leadframe pad surface allows for increased fillet height of the adhesive and reduces resin bleed, improving the adhesion and reliability of the semiconductor package by minimizing delamination.

Implementation Method 1

adhesion between leadframe elements and epoxy-based mold compounds can be improved by adding a roughened surface to some or all leadframe elements

Methodology Applied

Scientific EffectMechanical interlocking:

Implementation Method 2

roughening of the whole leadframe surface by chemically etching the leadframe surface

Methodology Applied

Scientific EffectSurface area increase:

Implementation Method 3

Incorporating a groove on the leadframe pad surface that restricts the flow of die attach adhesive and resin bleed, thereby maintaining a controlled adhesive thickness

Methodology Applied

Scientific EffectPhysical containment: Physical Containment

Implementation Method 4

The groove on the leadframe pad surface allows for increased fillet height of the adhesive and reduces resin bleed

Methodology Applied

Scientific EffectFlow restriction:

Data Source

PatentUS12476204B2Semiconductor package substrate with groove on die pad

Publication Date: 2025.11.18 TEXAS INSTRUMENTS INC

AI summary

A semiconductor package includes a metallic pad and leads spaced from the metallic pad by a gap, the metallic pad including a roughened surface. The semiconductor package further includes a semiconductor die including bond pads, and an adhesive between the roughened surface of the metallic pad and the semiconductor die, therein bonding the semiconductor die to the metallic pad, wherein the adhesive includes a resin. The metallic pad further includes a groove surrounding the semiconductor die on the roughened surface, the groove having a surface roughness less than a surface roughness of the roughened surface of the metallic pad.