Leadframe Finishing Pattern to Prevent Encapsulation Delamination

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Solution Overview

Problem

Current manufacturing processes of semiconductor devices using a silver finishing layer on leadframes result in reduced adhesion between the leadframe and the encapsulation material, leading to delamination issues that can cause wire breakage and die attach material cracking.

Innovation Solution

A patterned finishing layer is applied to cover only the regions of the leadframe where electrical components are attached, with the remaining areas being cleared via laser ablation to prevent contact between the encapsulation and the finishing layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a silver finishing layer is provided on the mounting surface of the leadframe, then reliability of die attachment and wire bonding is improved, but adhesion between the leadframe and the encapsulation is reduced

Engineering Contradiction:

Improvereliability of die attachment and wire bondingVSAvoidadhesion between leadframe and encapsulation

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The leadframe surface is divided into two distinct regions: a first region with a silver finishing layer for component attachment, and a second region without the finishing layer for encapsulation contact. This segmentation allows each region to have optimized properties for its specific function, resolving the contradiction between bonding reliability and encapsulation adhesion.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different surface properties are applied to different regions of the leadframe. The first region has a silver finishing layer that provides excellent electrical and mechanical properties for die attachment and wire bonding, while the second region has a bare copper surface that provides superior adhesion for the encapsulation material. This local differentiation resolves the contradiction by allowing each region to excel at its specific function.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If the finishing layer covers the entire surface of the leadframe, then electrical components can be easily attached, but delamination of the encapsulation occurs

Engineering Contradiction:

Improveease of component attachmentVSAvoidencapsulation integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The leadframe surface is segmented into a first region with the finishing layer for component attachment and a second region without the finishing layer for encapsulation bonding. This segmentation prevents the encapsulation from contacting the finishing layer, thereby preventing delamination while maintaining ease of component attachment in the first region.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The silver finishing layer is extracted or removed from the second region of the leadframe surface where the encapsulation will contact. This removal eliminates the harmful interaction between the encapsulation and the finishing layer that causes delamination, while the finishing layer remains intact in the first region to facilitate component attachment.

Inventive Principle:

Principle #2Taking out (Extraction)

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

This approach reduces the risk of delamination, maintaining the integrity of the semiconductor device by ensuring the encapsulation material does not contact the finishing layer, thereby preventing mechanical stress on wires and die attach materials.

Implementation Method 1

the finishing layer may be removed from regions of the surface of the leadframe that are not covered by the electrical components via laser ablation

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentEP4611037A1Method of manufacturing semiconductor devices

Publication Date: 2025.09.03 STMICROELECTRONICS INT NV

Figure 1~2
Figure 3A~3B
Figure 3C~3D

AI summary

Surface finishing material (100) is provided at a surface of an electrically conductive substrate (12) wherein the surface of the electrically conductive substrate (12) comprises complementary adjacent first (120A, 120B) and second surface regions. At least one semiconductor die (14) is arranged at the first surface region (120A, 120B) of the surface of the electrically conductive substrate (12) having surface finishing material 100 thereon. The surface finishing material (100) is removed from at least one portion of the second surface region of the surface of the electrically conductive substrate (12). An electrically insulating encapsulation (20) is molded onto the electrically conductive substrate (12) having the at least one semiconductor die (14) arranged thereon at the first region (120A, 120B) of the surface of the electrically conductive substrate (12). The electrically insulating encapsulation (20) encapsulates the at least one semiconductor die (14) arranged at the first surface region (120A, 120B) of the surface of the electrically conductive substrate (12) having surface finishing material (100) thereon. The electrically insulating encapsulation (20) contacts the surface of the electrically conductive substrate (12) at said at least one portion of the second surface region of the electrically conductive substrate (12) having the surface finishing material (100) removed therefrom.