Intra-Stack Encapsulation for IC Package Warpage Mitigation

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Solution Overview

Problem

Integrated circuit package-on-package systems face challenges with warpage due to mismatched thermal expansion coefficients, leading to poor yields, device failures, and increased costs, especially in harsh environmental conditions.

Innovation Solution

A mountable integrated circuit package system is designed with an interposer having a central aperture, intra-stack interconnects, and intra-stack encapsulation surrounding the interposer and integrated circuit devices, providing additional planar rigidity and thermal management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If multiple integrated circuits are mounted on a single substrate to increase density, then integrated circuit density is improved, but warpage occurs due to mismatched thermal expansion coefficients

Engineering Contradiction:

Improveintegrated circuit densityVSAvoidsubstrate warpage

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

An interposer substrate is introduced as an intermediary component between the first substrate and the second substrate. The interposer has a coefficient of thermal expansion that matches both substrates, acting as a thermal expansion buffer that prevents warpage while enabling high-density mounting of multiple integrated circuits

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The package system uses a composite structure with three different substrate materials having different coefficients of thermal expansion. The interposer substrate is specifically selected or engineered to have intermediate thermal expansion properties, creating a composite structure that compensates for differential thermal expansion and prevents warpage

Inventive Principle:

Principle #40Composite materials

2Reliability

If integrated circuits are exposed to harsh environmental conditions, then device performance is maintained, but warpage increases leading to device failures

Engineering Contradiction:

Improvedevice performance under environmental conditionsVSAvoidenvironmental warpage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The interposer substrate serves as a mediator that isolates the sensitive integrated circuits from the harmful effects of thermal expansion mismatch during environmental testing. By matching the thermal expansion properties, it prevents warpage-induced failures while allowing devices to withstand harsh conditions

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The interposer substrate provides beforehand cushioning by pre-compensating for thermal expansion differences before environmental stress occurs. This preventive measure ensures that when temperature variations occur during environmental testing, the matched thermal expansion coefficients prevent warpage and protect the device

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If underfill encapsulant material is applied between IC chip stack and bottom package carrier, then connections are protected, but manufacturing complexity increases

Engineering Contradiction:

Improveconnection protectionVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The interposer substrate acts as an intermediary that provides a stable, flat mounting surface for the integrated circuit chip stack. This intermediate platform distributes mechanical stresses uniformly, protecting the delicate connections without requiring complex underfill encapsulation processes

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 mitigating warpage and reducing thermal expansion mismatches, resulting in cost-effective and efficient manufacturing with enhanced performance.

Implementation Method 1

improves yield and reliability by reducing warpage of the package carrier, the interposer, and the integrated circuit device stack

Methodology Applied

Scientific EffectPlanar rigidity: Elasticity

Implementation Method 2

mitigating warpage and reducing thermal expansion mismatches

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS8247893B2Mountable integrated circuit package system with intra-stack encapsulation

Publication Date: 2012.08.21 STATS CHIPPAC MANAGEMENT PTE LTD

AI summary

A mountable integrated circuit package system comprising: mounting a first integrated circuit device over a package carrier; mounting an interposer including a central aperture over the package carrier, an intra-stack interconnect connected between the interposer and the package carrier, and the first integrated circuit device within the central aperture; and forming an intra-stack encapsulation over the package carrier and surrounding the interposer.