Lead Frame Sidewall Roughening for Resin Adhesion in Flip-Chip Packages

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Solution Overview

Problem

In semiconductor devices using flip chip bonding, insufficient adhesion between resin and lead frame leads to voids and solder cracks, increasing resistance and risking malfunction due to heat generation.

Innovation Solution

A lead frame with a roughened side wall surface in the opening portion is used, enhancing adhesion with resin through an anchor effect, preventing voids and solder cracks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If flip chip bonding is used to achieve high densification and high integration, then the package size can be reduced, but the chip becomes vulnerable to external stress and adhesion between resin and lead frame becomes insufficient

Engineering Contradiction:

Improvepackage sizeVSAvoidadhesion between resin and lead frame

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The invention applies local quality by creating a roughened surface specifically at the side wall surface of the lead frame in the opening portion where resin adhesion is needed, while keeping other surfaces smooth. This localized surface treatment enhances adhesion precisely where required without affecting other functional areas of the lead frame.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The roughening treatment is performed in advance on the lead frame side wall surface before resin filling. This preliminary action creates an anchor effect that prevents voids and solder cracks from forming during subsequent packaging processes, addressing the adhesion problem before it occurs.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If insufficient adhesion between resin and lead frame occurs, then voids and solder cracks are generated near the interface, but increasing adhesion strength may cause defects

Engineering Contradiction:

Improveadhesion between resin and lead frameVSAvoidvoids and solder cracks

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The roughened surface creates a porous-like structure with increased surface area and irregularities. This porous structure allows the resin to penetrate and anchor into the surface, creating mechanical interlocking that prevents void formation and solder cracks without requiring excessive adhesion strength that could cause other defects.

Inventive Principle:

Principle #31Porous materials

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

Secures sufficient adhesion between lead frame and resin, reducing defects and ensuring reliable operation of semiconductor devices.

Implementation Method 1

A side wall surface of the lead frame in the opening portion has a larger average surface roughness than an upper surface of the lead frame

Methodology Applied

Scientific EffectAnchor effect: Mechanical Fastener

Data Source

PatentUS20250218923A1Semiconductor device, method of manufacturing semiconductor device, and module

Publication Date: 2025.07.03 ROHM CO LTD

AI summary

There is provided a semiconductor device including: a lead frame including a first opening portion; a resin filled in the first opening portion; and a semiconductor element electrically connected to the lead frame, wherein a side wall surface of the lead frame in the first opening portion has a larger average surface roughness than an upper surface of the lead frame.