Solder Array Thermal Interface Structure to Prevent STIM Flow-Out

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional solder thermal interface materials (STIM) used in microelectronic packages melt and flow out during high-temperature BGA solder ball attach and board assembly processes, leading to voids and degraded thermal performance, and further degrade due to temperature cycling, resulting in reduced thermal efficiency.

Innovation Solution

A solder array thermal interface material (SA-TIM) is employed, comprising 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, 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 high-temperature BGA solder ball attach and board assembly processes, leading to voids and degraded thermal performance

Engineering Contradiction:

Improvethermal performanceVSAvoidstructural integrity of STIM

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent divides the continuous STIM layer into discrete solder bumps arranged in an array pattern. This segmentation prevents the STIM from flowing out during high-temperature processes while maintaining thermal contact between the IHS and silicon die. The solder bumps are positioned at specific locations to ensure thermal performance without the structural integrity issues of a continuous STIM layer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses a composite structure combining solder material with a polymer underfill material. The solder bumps provide thermal conduction and mechanical bonding, while the polymer underfill protects the solder bumps from oxidation, provides mechanical support, and prevents flow-out during assembly processes. This composite approach resolves the contradiction between thermal performance and structural stability.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If SA-TIM with polymer underfill is used to protect solder contacts, then structural integrity is improved, but the z-height of the STIM layer is reduced to less than 150 microns

Engineering Contradiction:

Improvestructural integrityVSAvoidz-height of STIM layer

Core Design Contradiction:

Stability of the object's compositionVSLength of stationary object

Solution Approach 1:

The patent employs a thin polymer underfill material that acts as a protective shell around the solder bumps. This thin film provides mechanical protection and structural integrity while maintaining a compact z-height of less than 150 microns. The flexible nature of the polymer allows it to conform to the solder bump structures without adding excessive height.

Inventive Principle:

Principle #30Flexible shells and thin films

3Adaptability or versatility

If SA-TIM is used to accommodate chip height variations in multi-chip packages, then adaptability is improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improveaccommodation of chip height variationsVSAvoidarray pattern alignment

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent creates a dynamic thermal interface structure where the solder bumps and polymer underfill can accommodate variations in chip height through elastic deformation and compression. The array pattern of solder bumps allows for differential height compensation at each contact point, providing adaptability to multi-chip package variations while maintaining reliable thermal and electrical connections.

Inventive Principle:

Principle #15Dynamics

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 preventing STIM degradation, maintaining structural integrity, and allowing for thinner bond lines, thereby improving the thermal efficiency and reliability of microelectronic packages.

Implementation Method 1

The plurality of STIM thermal interconnects may be coupled with the silicon die... The IHS may be coupled with the plurality of STIM thermal interconnects... The SA-TIM enhances thermal performance

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

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

Methodology Applied

Scientific EffectMechanical protection:

Data Source

PatentUS20250096178A1Microelectronic package with solder array thermal interface material (sa-tim)

Publication Date: 2025.03.20 INTEL CORP

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.