Laser-Treated Leadframe Surfaces for Semiconductor Adhesion

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Solution Overview

Problem

Current methods for improving adhesion between leadframes and encapsulation compounds in semiconductor packages are costly, negatively impact wire bonding, and are not suitable for small component sizes, especially in automotive and medical applications where moisture sensitivity is critical.

Innovation Solution

A computer-controlled laser is used to create selective rough regions on the leadframe surface, forming amorphous metal piles that enhance adhesion without the need for masks or chemicals, allowing for precise control over surface roughness and reducing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If chemical etching is used to roughen the leadframe surface, then adhesion to encapsulation compound is improved, but manufacturing complexity increases due to mask application and proprietary process requirements

Engineering Contradiction:

Improveadhesion to encapsulation compoundVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces chemical etching processes with mechanical abrasion using abrasive particles. Instead of using chemical solutions and masks to roughen the leadframe surface, the invention applies mechanical force through abrasive particles to achieve the desired surface roughness. This substitution eliminates the need for proprietary chemical processes and mask application steps, reducing manufacturing complexity while maintaining adhesion improvement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the method of surface roughening from chemical to mechanical parameters. By controlling the mechanical abrasion parameters such as abrasive particle size, concentration, and application method, the invention achieves consistent surface roughness without requiring complex chemical process control, mask materials, or proprietary chemical formulations.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If nickel plating is used to deposit rough surface, then adhesion is improved, but cost increases due to material intensity and mask requirements

Engineering Contradiction:

ImproveadhesionVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces the additive nickel plating process with a mechanical abrasion process. Instead of depositing additional nickel material to create surface roughness, the invention uses mechanical abrasion to roughen the existing leadframe surface. This eliminates the need for nickel plating baths, masks, and the associated material and equipment costs.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent eliminates the need for expensive nickel plating materials and mask materials by using a mechanical abrasion process that works directly on the leadframe surface. The abrasive particles can be recovered and reused, reducing material costs compared to the consumable nature of plating chemicals and mask materials.

Inventive Principle:

Principle #34Discarding and recovering

3Reliability

If general surface roughening is applied, then adhesion is improved, but wire bonding quality deteriorates due to vision system difficulties and capillary life reduction

Engineering Contradiction:

ImproveadhesionVSAvoidwire bonding quality

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent applies local quality by selectively roughening only specific areas of the leadframe surface that require enhanced adhesion, rather than uniformly roughening the entire surface. This allows the invention to improve adhesion in critical bonding areas while leaving wire bonding areas smooth, thereby maintaining wire bonding quality and vision system compatibility.

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 laser-roughening technique provides reliable adhesion, inhibits delamination, and is cost-effective, applicable at any stage of semiconductor assembly, and compatible with various leadframe materials, enhancing moisture sensitivity and reducing logistical complexities.

Implementation Method 1

A laser is used to heat and melt selected regions of the original leadframe surface

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

The laser heats and melts the leadframe surface material, forming amorphous metal piles through controlled ablation and re-deposition

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 3

The laser heats and melts the leadframe surface material, forming amorphous metal piles through controlled ablation and re-deposition

Methodology Applied

Scientific EffectPhase change (melting and solidification): Phase Change

Data Source

PatentUS8158460B2Method of forming metallic leadframes having laser-treated surfaces for improved adhesion to polymeric compounds

Publication Date: 2012.04.17 TEXAS INSTRUMENTS INC

AI summary

A leadframe for the assembly of a semiconductor chip has regions (112) with an original smooth surface of glossy appearance and regions (113, 114, 210) of a frosty appearance with rough surface contours. The regions of rough surface contours include two-dimensional arrays of spots (401) comprising a central area (402) below the original surface (400) and a piled ring (403) above the original surface. The piled ring (403) consists of the leadframe material in amorphous configuration.