Stackable IC Package Stiffener Warpage Mitigation

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Solution Overview

Problem

Integrated circuit density is limited by warpage issues in stackable package systems, leading to poor yields, device failures, and increased costs due to compromised mechanical and electrical connectivity, especially under varying environmental conditions.

Innovation Solution

A stackable integrated circuit package system is designed with a stiffener mounted over a package carrier and a mountable package carrier, maintaining a vertical gap for thermal management and additional planar rigidity, using metallic materials like copper-plated nickel for the stiffener and adhesive bonding, to mitigate warpage caused by thermal expansion mismatches.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If integrated circuits are densely packed in stackable package systems to increase integrated circuit density, then the quantity of integrated circuits per unit area increases, but warpage occurs during manufacturing or operation leading to poor yields and device failures

Engineering Contradiction:

Improveintegrated circuit densityVSAvoidyield and device reliability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A stiffener is introduced as an intermediary component between the integrated circuit device and the mountable package carrier. The stiffener acts as a mediator that absorbs and distributes thermal stresses, preventing direct transmission of warpage forces to the integrated circuit device while maintaining structural support for the stacked configuration.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The stiffener is constructed from composite materials with specific mechanical properties, combining rigidity to maintain structural integrity with appropriate thermal expansion characteristics to match the surrounding components. This composite structure provides both mechanical support and thermal stress management.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If stackable package systems are designed with multiple integrated circuits mounted closely together, then integrated circuit density increases, but mechanical properties are compromised leading to warpage and device failures

Engineering Contradiction:

Improveintegrated circuit densityVSAvoidmechanical properties

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The stiffener serves as a mechanical intermediary that reinforces the package structure. It distributes mechanical loads across the package carrier, preventing localized stress concentrations that would cause warpage in densely packed configurations.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The stiffener acts as a structural counterweight that balances the mechanical stresses generated by the dense stacking of integrated circuits. Its rigidity compensates for the weakened mechanical properties of the package carrier under high-density loading conditions.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

3Adaptability or versatility

If integrated circuit packages are exposed to harsh environmental conditions such as cold, heat, and humidity to meet portable electronics requirements, then adaptability to environmental conditions improves, but warpage increases resulting in failure and field returns

Engineering Contradiction:

Improveenvironmental condition adaptabilityVSAvoiddevice reliability under environmental stress

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The stiffener's material parameters are specifically selected to provide thermal stability across the operating temperature range. Its coefficient of thermal expansion is matched to minimize differential expansion with adjacent components, and its mechanical properties are optimized to maintain rigidity across temperature variations from cold to heat.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The stiffener mediates the thermal stresses generated by environmental exposure. It acts as a buffer that absorbs expansion and contraction forces during temperature cycling, protecting the integrated circuit device and package carrier from warpage that would otherwise occur under harsh environmental conditions.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution improves yield and reliability by providing additional planar rigidity and thermal management, reducing warpage and enhancing the mechanical and electrical integrity of the package system, thus addressing the limitations of existing technologies.

Implementation Method 1

mitigate warpage caused by thermal expansion mismatches

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

providing additional planar rigidity

Methodology Applied

Scientific EffectRigidity:

Implementation Method 3

adhesive bonding

Methodology Applied

Scientific EffectAdhesive bonding: Adhesive

Data Source

PatentUS8779570B2Stackable integrated circuit package system

Publication Date: 2014.07.15 STATS CHIPPAC MANAGEMENT PTE LTD

AI summary

A stackable integrated circuit package system including mounting an integrated circuit device over a package carrier, mounting a stiffener over the package carrier and mounting a mountable package carrier over the stiffener with a vertical gap between the integrated circuit device and the mountable package carrier.