Leadframe Groove Structure for Die Attach Resin Bleed 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, which compromises the reliability and robustness of the semiconductor packages.

Innovation Solution

Implementing grooves that straddle the topside and sidewall surfaces of the leadframe, restricting the flow of die attach adhesive and resin bleed, thereby maintaining a higher fillet height and improving adhesion between the leadframe and mold compound.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

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:

StrengthVSManufacturing precision

Solution Approach 1:

The leadframe surface is engineered with different local properties: roughened areas (including grooves) where mold compound adhesion is needed, and smoother areas where die attach adhesive should be contained. This spatial differentiation of surface quality allows simultaneous achievement of strong mold compound bonding and controlled adhesive fillet formation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The leadframe surface is segmented into distinct functional zones: grooves that channel and restrict adhesive flow, smooth areas that maintain adhesive containment, and roughened areas that provide mold compound anchoring. This segmentation resolves the contradiction by assigning different surface characteristics to different functional requirements.

Inventive Principle:

Principle #1Segmentation

2Strength

If the leadframe surface is roughened to improve adhesion between the leadframe and mold compound, then adhesion is improved, but resin bleed increases and delamination susceptibility increases

Engineering Contradiction:

Improveadhesion between leadframe and mold compoundVSAvoidsusceptibility to delamination

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The grooves act as intermediary structures that mediate between the roughened surface (which promotes adhesion) and the die attach adhesive (which should be contained). The grooves provide a controlled pathway that allows resin to be channeled to specific areas while preventing uncontrolled bleed that would compromise reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If chemical etching is used to roughen the leadframe surface selectively, then adhesion is improved in selected areas, but the process becomes more complex and expensive due to mask application

Engineering Contradiction:

Improveadhesion between leadframe and mold compoundVSAvoidmanufacturing process complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The leadframe structure itself is designed to serve multiple functions: the grooves simultaneously provide adhesion enhancement, adhesive flow restriction, and resin bleed control. This multi-functionality eliminates the need for separate masking processes, reducing manufacturing complexity while maintaining adhesion benefits.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The leadframe structure provides its own adhesion enhancement features through integrated grooves and surface roughening, eliminating the need for external masking processes. The structure serves its own functional requirements without requiring additional complex manufacturing steps.

Inventive Principle:

Principle #25Self-service

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 grooves enhance the mechanical interlocking of the mold compound with the leadframe, reducing resin bleed and delamination risks, thus improving the reliability and robustness of semiconductor packages.

Implementation Method 1

The grooves enhance the mechanical interlocking of the mold compound with the leadframe

Methodology Applied

Scientific EffectMechanical interlocking:

Implementation Method 2

die attach adhesive flows more readily across a roughened leadframe surface than a smooth leadframe surface due to protuberances of the roughened surface interfering with surface tension forces of the liquid die attach adhesive

Methodology Applied

Scientific EffectSurface tension: Surface Tension

Data Source

PatentUS20260090401A1Semiconductor package substrate with a smooth groove straddling topside and sidewall

Publication Date: 2026.03.26 TEXAS INSTRUMENTS INC

AI summary

A semiconductor package includes a metallic substrate, the metallic substrate including a roughened surface, a semiconductor die including bond pads, and an adhesive between the roughened surface of a topside of the metallic substrate and the semiconductor die, therein bonding the semiconductor die to the metallic substrate. The adhesive includes a resin. The metallic substrate further includes a groove about a perimeter of 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 substrate. The groove straddles the topside and a sidewall of the metallic substrate.