Wiring Substrate Layer Layout for Copper Diffusion Resistance

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Solution Overview

Problem

Existing wiring substrates used in semiconductor device testing face issues such as leakage current and reduced lifespan due to copper diffusion and electromigration, particularly under high temperature and humidity conditions.

Innovation Solution

The wiring substrate design includes a specific configuration with alternating layers of glass cloth and copper wiring, using a solder resist with a higher glass-transition temperature and adjusting the distances between lands and wiring layers to mitigate copper migration and electromigration, and incorporating staggered cavity patterns to reduce hillock formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional wiring substrate design is used, then manufacturing is simpler, but copper diffusion and electromigration occur under high temperature and humidity conditions, reducing reliability and lifespan

Engineering Contradiction:

ImprovereliabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The wiring substrate is divided into multiple wiring layers (first, second, third wiring layers) with different distance configurations from the surface. This segmentation allows each layer to be optimized for specific functions - the first wiring layer is positioned farther from the surface to reduce copper diffusion, while the second and third layers are positioned closer for signal transmission, thereby improving reliability without excessive complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different wiring layers are positioned at different distances from the surface based on their specific functional requirements. The first wiring layer uses a larger distance to prioritize copper diffusion prevention, while the second and third layers use smaller distances to prioritize signal transmission performance. This local optimization of positioning parameters improves overall reliability while maintaining manageable device complexity

Inventive Principle:

Principle #3Local quality

2Speed

If wiring layers are positioned closer to the surface, then signal transmission is improved, but copper diffusion and electromigration increase, reducing lifespan

Engineering Contradiction:

Improvesignal transmissionVSAvoidlifespan

Core Design Contradiction:

SpeedVSDuration of action of stationary object

Solution Approach 1:

The signal transmission function is distributed across multiple wiring layers at different positions. The second and third wiring layers are positioned closer to the surface for efficient signal transmission, while the first wiring layer is positioned farther away to ensure long-term stability. This segmentation of functions across layers allows both speed and lifespan requirements to be met simultaneously

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The problem of balancing signal transmission speed and component lifespan is resolved by adding the vertical dimension (distance from surface) as a differentiation parameter. Instead of compromising either speed or lifespan, the invention uses the third dimension (stacking direction distance) to create multiple wiring layers with optimized positions, thereby achieving both fast signal transmission and long lifespan

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Stability of the object's composition

If wiring layers are positioned farther from the surface, then copper diffusion is reduced, but signal transmission efficiency decreases

Engineering Contradiction:

Improvecopper diffusion resistanceVSAvoidsignal transmission

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

The copper diffusion resistance function is assigned to the first wiring layer positioned farther from the surface, while the signal transmission function is assigned to the second and third wiring layers positioned closer to the surface. This functional segmentation allows each layer to be optimized for its specific purpose without compromising the other

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The distance parameter is locally optimized for each wiring layer based on its function. The first wiring layer uses a larger distance to maximize copper diffusion resistance, while the second and third layers use smaller distances to maximize signal transmission efficiency. This local quality differentiation resolves the contradiction between stability and speed

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 improved design significantly extends the lifespan of the test boards by reducing copper diffusion and electromigration, thereby enhancing reliability under harsh environmental conditions.

Implementation Method 1

using a solder resist with a higher glass-transition temperature

Methodology Applied

Scientific EffectGlass-transition temperature:

Implementation Method 2

incorporating staggered cavity patterns to reduce hillock formation

Methodology Applied

Scientific EffectStress distribution:

Data Source

PatentUS12550254B2Wiring substrate

Publication Date: 2026.02.10 KIOXIA CORP

AI summary

A wiring substrate according to one embodiment includes a plurality of wiring layers and a plurality of insulating layers alternately stacked in a stacking direction. The plurality of wiring layers include a first wiring layer closest to a surface on one side in the stacking direction of the wiring substrate and a second wiring layer second closest to the surface. A distance from the surface to the first wiring layer is larger than a distance from the first wiring layer to the second wiring layer.