Flex Prevention Ring for IC Module Mechanical Support

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Solution Overview

Problem

In silicon integrated circuit chip packaging, nonseparable module-board connections like BGA limit the module area, causing thermal stress and potential warping or cracking due to lack of mechanical support under the module, especially when the number of off-module electrical contacts diminishes, requiring innovative solutions for mechanical support and thermal interface management.

Innovation Solution

The integration of mechanical structures, such as a ring, into the regions of the module's bottom surface without electrical contacts, allowing lateral motion and inhibiting bending under vertical forces, which provides necessary mechanical support and allows for low thermal resistance contacts by distributing pressure across the module's surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If nonseparable module-board connections (BGA) are used, then electrical connectivity is achieved, but thermal stress causes warping or cracking due to insufficient mechanical support

Engineering Contradiction:

Improveelectrical connectivityVSAvoidmechanical support

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

A mechanical structure acts as an intermediary element between the module substrate and PCB, providing mechanical support in regions without electrical contacts. This mediator distributes thermal stress and prevents warping while allowing lateral motion to accommodate thermal expansion differences between materials.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Area of moving object

If module area is increased to accommodate more chip functionality, then chip capacity is improved, but thermal stress and warping increase due to larger area without proportional increase in contact support

Engineering Contradiction:

Improvemodule areaVSAvoidmodule stability

Core Design Contradiction:

Area of moving objectVSStability of the object's composition

Solution Approach 1:

The module substrate area is segmented into contact regions and non-contact regions. Mechanical structures are strategically placed in non-contact regions to provide localized support, enabling the module to achieve larger total area while maintaining stability through distributed mechanical reinforcement.

Inventive Principle:

Principle #1Segmentation

3Stability of the object's composition

If mechanical support is added to prevent warping, then structural stability is improved, but lateral motion capability deteriorates due to thermal expansion constraints

Engineering Contradiction:

Improvestructural stabilityVSAvoidlateral motion capability

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The mechanical structure is designed with dynamic characteristics that allow it to be rigid in the vertical direction (providing anti-bending support) while remaining compliant in the lateral direction (allowing thermal expansion motion). This anisotropic mechanical behavior simultaneously achieves structural stability and thermal adaptability.

Inventive Principle:

Principle #15Dynamics

4Temperature

If pressure is applied to achieve low thermal resistance contact, then thermal performance is improved, but module bending and cracking increase due to lack of mechanical support

Engineering Contradiction:

Improvethermal resistanceVSAvoidmodule integrity

Core Design Contradiction:

TemperatureVSStrength

Solution Approach 1:

Mechanical support structures are pre-installed on the module substrate before applying pressure for thermal contact. This preliminary action ensures that the substrate has adequate structural integrity to withstand the pressing force without bending or cracking, enabling achievement of low thermal resistance contacts.

Inventive Principle:

Principle #10Preliminary action

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 solution effectively prevents module deformation and thermal stress, enabling larger chip functionalities on the module surface while maintaining low thermal resistance contacts, even with reduced off-module electrical contacts, by providing mechanical support and flexibility in module design.

Implementation Method 1

The separable contacts allow for slippage between the module and the board during thermal expansion and contraction.

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

making a low thermal resistance contact requires temporary or long term pressure on the top surface of the chips. If there is no support on the bottom surface of the module, then the module will bend, warp or crack.

Methodology Applied

Scientific EffectPressure distribution: Pressure Gradient

Data Source

PatentUS11631635B2Flex prevention mechanical structure such as a ring for large integrated circuit modules and packages and methods of manufacture using same

Publication Date: 2023.04.18 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A method includes attaching an integrated circuit chip module substrate to a printed circuit board (PCB). First region(s) of a bottom surface of the module include electrical contacts to the board, and second region(s) of the bottom surface of the module lack such contacts. Mechanical structures are assembled into the second regions. These structures allow lateral motion of the module relative to the board, and are sized and placed to inhibit bending of the second regions of the module towards the board under application of a vertical force on a top surface of the module. A package for an integrated circuit may be assembled using the method.