Removable Substrate for IC Package Warpage Control

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Solution Overview

Problem

Conventional IC packaging techniques face challenges in reducing warpage caused by thermal expansion mismatches, leading to planarity issues and reduced heat dissipation, as permanent bonding of substrates can insulate the die from heat sinks, compromising performance.

Innovation Solution

A method involving temporarily coupling a rigid substrate to the IC package to reduce warpage, allowing for improved coplanarity and then removing it to enable direct heat sink coupling with a thin thermal interface, thereby enhancing thermal conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a lid is permanently bonded to the IC package to reduce warpage, then the planarity of the IC package is improved, but the thermal conductivity from the die to the heat sink is reduced

Engineering Contradiction:

ImproveplanarityVSAvoidheat dissipation

Core Design Contradiction:

Manufacturing precisionVSLoss of energy

Solution Approach 1:

The packaging structure is divided into modular components: a first substrate bonded to the die, a removable second substrate that provides warpage control during assembly, and a heat sink. This segmentation allows the second substrate to be temporarily present during packaging to control warpage, then removed before final operation to restore thermal conductivity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second substrate transitions from a permanent component to a temporary, removable component. It is bonded during the packaging process to control warpage, then deliberately removed before the IC package enters service. This dynamic approach allows the system to have warpage control during manufacturing but optimal thermal performance during operation.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the size of the die and number of electrical connections is increased, then the electrical connection capability is improved, but the thermal management becomes more difficult

Engineering Contradiction:

Improveelectrical connection capabilityVSAvoidthermal management

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The second substrate, which causes thermal insulation, is extracted from the final package structure. It is used only temporarily during the packaging process to control warpage, then removed to allow direct thermal contact between the die and heat sink, solving the thermal management issue for high-power, high-connection-count devices.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Warpage control is performed in advance during the packaging process using the second substrate. By the time the IC package is completed and enters operation, the warpage control function has already been accomplished, and the second substrate is removed to prevent thermal interference during actual device operation.

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If a lid is bonded to the IC package, then the structural stability is improved, but the rate of heat removal is reduced

Engineering Contradiction:

Improvestructural stabilityVSAvoidheat removal rate

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The structural support function is segmented between the first substrate (permanent, provides baseline stability), the second substrate (temporary, provides enhanced warpage control during assembly), and the heat sink (permanent, provides thermal management). This segmentation allows optimal structural stability during manufacturing while maintaining optimal heat removal during operation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The thermal conductivity parameter of the package structure is changed dynamically. During packaging, the structure includes the insulating second substrate for stability. Before operation, the second substrate is removed, changing the thermal conductivity parameter to maximize heat removal rate from the die to the heat sink.

Inventive Principle:

Principle #35Parameter changes

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

This approach reduces warpage and improves electrical connection reliability while increasing heat dissipation efficiency by minimizing thermal interfaces and allowing direct contact between the heat sink and IC die.

Implementation Method 1

bonding a first surface of the integrated circuit die to a first substrate via a first plurality of solder bump structures

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

enabling direct heat sink coupling with a thin thermal interface, thereby enhancing thermal conductivity

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS9425171B1Removable substrate for controlling warpage of an integrated circuit package

Publication Date: 2016.08.23 NVIDIA CORP

AI summary

One embodiment of the present invention sets forth a technique for packaging an integrated circuit die. The technique includes bonding a first surface of the integrated circuit die to a first substrate via a first plurality of solder bump structures and bonding a second substrate to a second surface of the integrated circuit die. The technique further includes bonding the first substrate to a third substrate via a second plurality of solder bump structures and, after bonding the first substrate to the third substrate, removing the second substrate from the second surface of the integrated circuit die. The technique further includes disposing a heat sink on the second surface of the integrated circuit die.