SA-TIM Solder Array Structure for Thin Bond-Line Heat Dissipation

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Solution Overview

Problem

Conventional solder thermal interface materials (STIM) used in microelectronic packages face challenges such as melting and flow-out during assembly processes, leading to voids and degraded thermal performance, and further degradation due to temperature cycling, which affects the reliability and efficiency of heat dissipation in high-performance processors.

Innovation Solution

The use of a solder array thermal interface material (SA-TIM) with an array of solder contacts mechanically protected by polymer underfill material, reducing the z-height of the STIM layer to less than 150 microns, preventing squeeze-out and flow-out during assembly, and accommodating chip height variations in multi-chip packages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional STIM is used to attach IHS to silicon die, then thermal performance is improved, but the STIM melts and flows out during assembly processes causing voids and degraded thermal performance

Engineering Contradiction:

Improvethermal performanceVSAvoidSTIM integrity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent divides the continuous STIM layer into discrete solder balls arranged in an array pattern. This segmentation prevents the STIM from flowing out during assembly while maintaining thermal contact points between the IHS and silicon die. The solder balls are positioned at specific locations to ensure thermal performance without the drawbacks of a continuous STIM layer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an underfill material as an intermediary substance that surrounds and secures the solder balls in place. This underfill acts as a mediator that prevents the solder balls from moving or flowing out during assembly processes while maintaining the structural integrity of the thermal interface between IHS and silicon die.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If STIM bond line thickness is increased to prevent degradation, then reliability is improved, but thermal performance is degraded due to increased thermal resistance

Engineering Contradiction:

ImproveSTIM durabilityVSAvoidthermal resistance

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

By segmenting the STIM into discrete solder balls, the patent achieves reliable thermal contact without requiring a thick continuous layer. The solder balls make direct contact with both the IHS and silicon die, creating efficient thermal pathways with minimal bond line thickness and reduced thermal resistance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent creates a composite thermal interface structure combining solder balls (high thermal conductivity) with underfill material (structural support). This composite approach provides both reliability through secure positioning and low thermal resistance through direct solder-to-surface contact, eliminating the need for thick STIM layers.

Inventive Principle:

Principle #40Composite materials

3Device complexity

If solder balls are used without underfill, then device complexity is reduced, but the solder balls move and deform during assembly processes

Engineering Contradiction:

ImproveTIM structureVSAvoidsolder ball position

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

The underfill material serves as an intermediary that surrounds and anchors the solder balls in their designated positions. This intermediary substance prevents solder ball movement and deformation during assembly while maintaining the relative simplicity of the overall TIM structure compared to continuous STIM applications.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The underfill material forms a flexible matrix that accommodates the solder balls while providing mechanical support and positional stability. This thin film-like structure secures the solder balls without adding significant complexity to the TIM assembly.

Inventive Principle:

Principle #30Flexible shells and thin films

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 SA-TIM enhances thermal performance by maintaining a thinner bond line and preventing degradation, ensuring reliable heat dissipation and structural stability in microelectronic packages, even under temperature cycling conditions.

Implementation Method 1

The array of solder contacts is thermally coupled to a backside of the silicon die and a face of the integrated heat spreader

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

The array of solder contacts is mechanically protected by polymer underfill material

Methodology Applied

Scientific EffectMechanical support and protection:

Data Source

PatentEP3758058B1Microelectronic package with solder array thermal interface material (sa-tim)

Publication Date: 2024.07.17 INTEL CORP

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AI summary

Embodiments may relate to a microelectronic package that includes a die coupled with a package substrate. A plurality of solder thermal interface material (STIM) thermal interconnects may be coupled with the die and an integrated heat spreader (IHS) may be coupled with the plurality of STIM thermal interconnects. A thermal underfill material may be positioned between the IHS and the die such that the thermal underfill material at least partially surrounds the plurality of STIM thermal interconnects. Other embodiments may be described or claimed.