Anisotropic Conductive Membrane for Semiconductor Die Interconnects

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Solution Overview

Problem

Existing methods for connecting semiconductor dice to substrates, such as mass reflow and thermo-compression, face challenges including high temperature-induced stresses, long cycle times, and reliability issues due to shear and traction stresses from differing expansion coefficients, leading to potential electrical connection failures.

Innovation Solution

The use of an anisotropic conductive membrane between the semiconductor die and the substrate, compressed by electrical contact pillars, provides a more reliable and flexible electrical connection, allowing for less stringent positioning accuracy and accommodating thermal expansion mismatches.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If mass reflow or thermo-compression is used to connect dice to substrate, then electrical contact is achieved, but high temperature operation induces stresses on joints and leads to reliability issues

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidthermal stress on joints

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an anisotropic conductive membrane as an intermediary layer between the die and substrate. This membrane provides electrical conductivity in the vertical direction while mechanically accommodating thermal expansion differences, thereby reducing thermal stress transmission to the joints while maintaining reliable electrical contact.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the mechanical and thermal parameters of the connection system by using a soft, compliant anisotropic conductive membrane instead of rigid solder joints. This allows the connection structure to deform elastically under thermal stress, changing from a rigid stress-bearing connection to a compliant stress-absorbing connection.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If traditional pillar connection methods are used, then electrical contact is established, but positioning accuracy requirements are stringent and assembly is complex

Engineering Contradiction:

Improveelectrical contact reliabilityVSAvoidpositioning accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent employs a flexible anisotropic conductive membrane that can deform to accommodate positioning variations. The membrane's compliance allows it to conform to slight misalignments between die pillars and substrate pads, maintaining electrical contact reliability while significantly reducing the required positioning accuracy compared to rigid direct pillar-to-pad connections.

Inventive Principle:

Principle #30Flexible shells and thin films

3Ease of manufacture

If anisotropic conductive membrane is used between die and substrate, then positioning accuracy requirements are reduced and assembly is simplified, but additional material and process steps are introduced

Engineering Contradiction:

Improveassembly simplicityVSAvoidstructure complexity

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The anisotropic conductive membrane serves multiple functions simultaneously: it provides electrical conductivity, mechanical compliance, thermal stress absorption, and positioning tolerance compensation. By consolidating these multiple functions into a single component, the overall device complexity is managed while achieving simplified assembly and improved ease of manufacture.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enhances package reliability by absorbing shear stresses and maintaining electrical performance even with thermal expansion coefficient mismatches, while simplifying assembly and reducing the risk of connection failures.

Implementation Method 1

The anisotropic conductive membrane is compressed between the electrical contact pillars and the substrate to provide electrical contact

Methodology Applied

Scientific EffectCompression: Compression

Implementation Method 2

the anisotropic membrane may allow for differences in thermal expansion coefficients (and relative mismatch during package life) while providing satisfactory electrical performance also in offset conditions with shear stress absorbed by the membrane

Methodology Applied

Scientific EffectShear stress absorption: Shear Stress

Implementation Method 3

differences in thermal expansion coefficients (and relative mismatch during package life)

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS10522504B2Semiconductor device and corresponding method

Publication Date: 2019.12.31 STMICROELECTRONICS SRL

AI summary

In an embodiment, a semiconductor device includes: a mounting substrate having electrically conductive formations thereon, a semiconductor die coupled with the mounting substrate, the semiconductor die with electrical contact pillars facing towards the mounting substrate, an anisotropic conductive membrane between the semiconductor die and the mounting substrate, the membrane compressed between the electrical contact pillars and the mounting substrate to provide electrical contact between the electrical contact pillars of the semiconductor die and the electrically conductive formations on the mounting substrate.