Dual-Layer Underfill EMI Cage for Microstrip Package Routing

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Solution Overview

Problem

The reduction in package layer count in semiconductor packaging leads to increased risks of electromagnetic interference (EMI) and radio frequency interference (RFI) due to microstrip routing, especially when the metal stiffener is not properly grounded, prompting the need for additional layers that increase cost and Z-height.

Innovation Solution

Implementing an EMI/RFI cage formed with conductive epoxy or ink over the microstrip routing, which contacts the stiffener and is electrically coupled to a ground voltage, providing effective shielding without adding layers, thus mitigating interference risks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If package layer count is reduced to lower cost and Z-height, then manufacturing cost and package height are reduced, but electromagnetic interference and radio frequency interference risks increase

Engineering Contradiction:

Improvemanufacturing costVSAvoidelectromagnetic interference risk

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an EMI/RFI cage as an intermediary structure between the microstrip routing and the external environment. This cage acts as a mediator that blocks electromagnetic and radio frequency interference from affecting the microstrip routing, thereby resolving the contradiction between reduced layer count and increased interference risk without adding manufacturing complexity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The EMI/RFI cage is implemented as a thin, flexible shielding structure that can be integrated into the reduced layer count package design. This thin film approach provides effective electromagnetic shielding while maintaining the compact form factor and low cost associated with reduced layer count packaging

Inventive Principle:

Principle #30Flexible shells and thin films

2Length of stationary object

If microstrip routing is implemented at the surface to reduce layer count, then Z-height and cost are reduced, but the antenna effect increases EMI/RFI risk

Engineering Contradiction:

ImproveZ-heightVSAvoidantenna effect

Core Design Contradiction:

Length of stationary objectVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful antenna effect generated by the microstrip routing into a beneficial configuration by enclosing it within the EMI/RFI cage. The cage structure transforms the potential interference source into a controlled environment where the microstrip can operate without radiating interference, effectively turning the problem into a solution

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The microstrip routing is nested within the EMI/RFI cage structure, creating a hierarchical arrangement where the vulnerable microstrip is protected by the enclosing cage. This nesting approach allows the microstrip to maintain its surface-level position for compact Z-height while being shielded from generating or receiving interference

Inventive Principle:

Principle #7Nested doll (Nesting)

3Stability of the object's composition

If metal stiffener is added to mitigate warpage, then structural stability is improved, but ungrounded stiffener creates antenna effect increasing EMI/RFI risk

Engineering Contradiction:

Improvestructural stabilityVSAvoidEMI/RFI interference

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The EMI/RFI cage serves multiple functions simultaneously: it provides electromagnetic shielding for the microstrip routing, grounds the metal stiffener to prevent it from acting as an antenna, and maintains structural integrity. This multi-functionality resolves the contradiction by making the stiffener beneficial for both structural stability and EMI reduction

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

The EMI/RFI cage significantly reduces or eliminates interference risks while maintaining low cost and minimizing Z-height, offering a cost-effective solution to the interference challenges posed by lower layer counts.

Implementation Method 1

an electrically conductive layer around the non-conductive underfill

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

EMI cage for microstrip routing via dual layer underfill concept

Methodology Applied

Scientific EffectElectromagnetic shielding: Faraday Cage

Data Source

PatentUS20230395524A1EMI cage for microstrip routing via dual layer underfill concept

Publication Date: 2023.12.07 INTEL CORP

AI summary

Embodiments disclosed herein include electronic packages. In an embodiment, an electronic package comprises a package substrate, and a die coupled to the package substrate. In an embodiment, a stiffener is around the die and over the package substrate. In an embodiment, an electrically non-conductive underfill is around first level interconnects (FLIs) between the package substrate and the die. In an embodiment, an electrically conductive layer is around the non-conductive underfill.