Semiconductor Package Copper Strap Solder Joint Reliability

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Solution Overview

Problem

Semiconductor device packages using wirebonds exhibit high resistance due to the connections between the source electrode and terminal leads, which is addressed by transitioning to copper strap-based packages, but there is a need to improve the solder joints and stress management in these copper strap packages.

Innovation Solution

The copper straps feature formations like dimples, grooves, slanted or curved extensions, and through holes to enhance solder joints and stress release between the die electrode and lead frame, and include large area contacts to improve connectivity and molding compound flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If wirebonds are used to connect source electrode to terminal leads, then ease of manufacture is maintained, but package resistance increases

Engineering Contradiction:

Improvepackage resistanceVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent extracts the wirebond connection method and replaces it with a copper strap-based connection system. The copper strap directly connects the source electrode to the terminal leads, eliminating the need for wirebonds and thereby reducing package resistance while maintaining manufacturing feasibility through standardized copper strap assembly processes

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The copper strap acts as an intermediary component between the source electrode and terminal leads. This intermediate copper strap structure provides a low-resistance electrical path while enabling mechanical attachment through solder joints, thus resolving the contradiction between low resistance and ease of manufacture

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If copper straps with formations are used, then solder joint control improves, but device complexity increases

Engineering Contradiction:

Improvesolder joint controlVSAvoidstrap structure complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The copper strap is segmented into distinct functional regions: contact areas with dimples/grooves for solder joint formation, web regions for structural support, and leg regions for attachment to terminal leads. This segmentation allows each region to be optimized for its specific function while maintaining overall manufacturing feasibility through standardized fabrication processes

Inventive Principle:

Principle #1Segmentation

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 enhanced copper strap designs reduce package resistance, improve solder fatigue, and maintain cost-effectiveness, making them a superior alternative to wirebonded packages.

Implementation Method 1

drain electrode 108 is directly attached through a conductive adhesive, such as solder or conductive epoxy, to die pad 118

Methodology Applied