Leadframe Oxide Patterning for Semiconductor Package Adhesion

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Solution Overview

Problem

The delamination of the protective plastic package from the leadframe in semiconductor devices due to poor adhesion of the electrically insulating molding compound, exacerbated by the formation of a non-etching adhesion promotion (NEAP) layer which can dissolve in acidic processing baths, is a significant issue in leadframe-based semiconductor devices.

Innovation Solution

Selective exposure of the surface metallic layer on the leadframe to an oxidizing plasma to form an oxide layer, enhancing adhesion between the leadframe and the molding compound, thereby reducing the risk of delamination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a non-etching adhesion promotion (NEAP) layer is formed at the surface of the leadframe to enhance adhesion of the molding compound, then adhesion between the molding compound and leadframe is improved, but the manufacturing process becomes time- and cost-ineffective and the NEAP layer may dissolve when exposed to acidic processing baths

Engineering Contradiction:

Improveadhesion between molding compound and leadframeVSAvoidmanufacturing process efficiency and cost

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The invention changes the chemical state of the leadframe surface by forming an oxide layer through exposure to oxidizing plasma or chemical oxidation, transforming the metallic surface into an oxidized surface that provides better adhesion for the molding compound without requiring complex multi-step NEAP processing

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention extracts the essential function of the NEAP layer (adhesion promotion) and achieves it through a simpler oxidation process, eliminating the need for complex NEAP processing baths and multiple processing steps while maintaining the adhesion enhancement effect

Inventive Principle:

Principle #2Taking out (Extraction)

2Strength

If a non-etching adhesion promotion (NEAP) layer is formed to enhance adhesion, then adhesion between the molding compound and leadframe is improved, but the process becomes time-consuming and costly

Engineering Contradiction:

Improveadhesion between molding compound and leadframeVSAvoidmanufacturing cycle time

Core Design Contradiction:

StrengthVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a simple, inexpensive oxidation process (using common oxidizing agents like hydrogen peroxide or plasma) instead of complex, expensive NEAP processing equipment and multiple processing baths, reducing both time and cost while achieving the same adhesion enhancement effect

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Ease of operation

If a metallic finishing layer (such as silver) is formed on the leadframe to facilitate processing steps, then die attachment and wire bonding are facilitated, but adhesion of the molding compound to the leadframe deteriorates

Engineering Contradiction:

Improvedie attachment and wire bonding facilitationVSAvoidadhesion of molding compound to leadframe

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The invention segments the leadframe surface into two functional zones: a metallic finishing layer area for die attachment and wire bonding, and an oxidized area for molding compound adhesion, allowing each zone to optimize its specific function without compromising the other

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention applies oxidation selectively to specific portions of the leadframe surface (such as the leadframe body and lead fingers) while preserving the metallic finishing layer on areas where it is needed for electrical connections, creating different surface properties in different locations to satisfy different functional requirements

Inventive Principle:

Principle #3Local quality

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 oxide layer formed through selective oxidizing plasma exposure improves the adhesion of the molding compound to the leadframe, effectively preventing delamination and maintaining the integrity of the semiconductor device.

Implementation Method 1

selectively exposing the surface metallic layer to an oxidizing plasma in order to form an oxide layer at a portion of the surface of the leadframe

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

exposing the surface metallic layer to an oxidizing plasma

Methodology Applied

Scientific EffectPlasma: Plasma

Data Source

PatentUS20260026354A1Method of manufacturing semiconductor devices and corresponding semiconductor device

Publication Date: 2026.01.22 STMICROELECTRONICS INT NV

AI summary

A semiconductor die is arranged at a mounting region of a surface of a substrate. A substrate includes electrically conductive leads around a die pad including a mounting region. A metallic layer is located at one or more portions of the substrate including the mounting region. A semiconductor die is arranged at a mounting region. The metallic layer is selectively exposed at portions less than all of the metallic layer to an oxidizing plasma to produce a patterned oxide layer including oxides of metallic material in the metallic layer. An electrically insulating encapsulation is molded onto the surface of the substrate to encapsulate the semiconductor die. The oxides of metallic material in the patterned oxide layer facilitate adhesion of the electrically insulating encapsulation to the surface of the substrate.