Rigid-Flex Die Stack Assembly for Reduced Substrate Footprint

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Solution Overview

Problem

As the number of electrical connectors connecting stacked semiconductor dies to a substrate increases, the area needed for attaching these connectors also increases, leading to reduced space for other components and connections, and making it difficult to keep the connectors separate.

Innovation Solution

The use of a rigid flex circuit with alternating rigid and flexible portions allows for the vertical alignment of die stacks, reducing the length of electrical connectors and minimizing the number of connections needed, thereby conserving space on the substrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple electrical connectors are used to connect stacked dies to substrate, then electrical connectivity is improved, but the area needed for attaching connectors increases

Engineering Contradiction:

Improveelectrical connectivityVSAvoidattachment area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent combines multiple electrical connectors into a single integrated connector structure that connects multiple stacked dies to the substrate simultaneously. This merging approach maintains full electrical connectivity for all dies while reducing the total attachment area required on the substrate, directly resolving the contradiction between connectivity and area usage.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The integrated connector is designed to perform multiple functions: it electrically connects multiple dies to the substrate, provides mechanical support for the die stack, and enables signal routing between different dies. This multi-functionality allows a single connector structure to replace what would traditionally require multiple separate connectors, thereby reducing attachment area while maintaining connectivity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If more electrical connectors are used to connect stacked dies, then connectivity capacity increases, but difficulty in keeping connectors separate increases

Engineering Contradiction:

Improveconnectivity capacityVSAvoidconnector separation difficulty

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges multiple separate connectors into a single integrated connector assembly where the individual connector elements are structurally unified. This integration eliminates the complexity of keeping multiple separate connectors aligned and separated, as the unified structure inherently maintains proper spacing and alignment while providing multiple connection points.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The integrated connector is segmented into distinct connection regions for each die, with each region providing dedicated electrical pathways. This segmentation allows the connector to handle multiple connections independently within a unified structure, maintaining connectivity capacity while simplifying the overall assembly process by reducing the number of separate components that must be managed.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12293992B2Semiconductor assemblies with systems and methods for managing high die stack structures

Publication Date: 2025.05.06 MICRON TECHNOLOGY INC

AI summary

A semiconductor device includes a rigid flex circuit that has a first rigid region and a second rigid region that are electrically connected by a flexible portion. A first die is mounted to a first side of the first rigid region. A second die is mounted to a second side of the second rigid region. The first and second sides are on opposite sides of the rigid flex circuit. The flexible portion is bent to hold the first and second rigid regions in generally vertical alignment with each other.