Metallic Stiffener Ring for PoP Substrate Flatness

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Solution Overview

Problem

The challenge is to maintain the flatness and prevent flexing and damage of thin Package-on-Package (PoP) electronic stacks during assembly and operation, while also preventing overflow of polymeric under-fill material from contaminating conductive interconnects, without increasing production complexity, cost, or failure rate.

Innovation Solution

A metallic stiffener ring is disposed around the outer periphery of the substrate, made from materials like copper, which provides sufficient stiffness and strength to prevent warping and flexing, and extends above the substrate surface to act as a dam for the under-fill material, ensuring electrical integrity and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If plastic, polymeric or ceramic stiffener rings are used to maintain flatness and prevent flexing, then structural stability is improved, but device complexity increases and operational space is reduced

Engineering Contradiction:

Improveflatness maintenanceVSAvoidpackage structure

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent combines the stiffening function and the under-fill dam function into a single integrated structure. The raised rim of the substrate serves both to maintain flatness/prevent flexing and to contain the under-fill material, eliminating the need for separate stiffener rings and dams.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The substrate's raised rim performs multiple functions: it provides structural stiffening to maintain flatness, acts as a dam to contain under-fill material, and defines the boundary between the central area and the pad area. This multi-functionality reduces overall device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Strength

If plastic, polymeric or ceramic stiffener rings are used to prevent warping and flexing, then structural strength is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveresistance to warpingVSAvoidfabrication process

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The stiffening structure is integrated into the substrate itself during the substrate fabrication process, rather than being added as a separate component. This eliminates the need for additional assembly steps and reduces manufacturing complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The raised rim is formed as part of the substrate manufacturing process before assembly. This preliminary formation of the stiffening structure simplifies subsequent assembly operations and reduces the number of manufacturing steps required.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If an insulating material dam is added to block under-fill overflow, then electrical integrity is improved, but device complexity and manufacturing steps increase

Engineering Contradiction:

Improveelectrical integrityVSAvoidpackage structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The substrate's raised rim serves as both a mechanical barrier and an electrical isolation structure. The rim's height and positioning prevent under-fill overflow onto the pad area, eliminating the need for separate insulating dams while maintaining electrical integrity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The raised rim acts as an intermediary structure between the central area and the pad area. It physically separates these regions and prevents contamination, serving as a built-in protective barrier that simplifies the overall design.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Reliability

If a polymeric dam is used to block under-fill material, then electrical integrity is improved, but the dam material lacks sufficient stiffness and additional removal process steps are needed

Engineering Contradiction:

Improveelectrical integrityVSAvoidmodulus of stiffness

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent changes the material parameter (stiffness) by using the substrate's rigid structure instead of a soft polymeric dam. The raised rim's mechanical properties provide both the necessary containment function and sufficient stiffness to maintain structural integrity during assembly.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9760132B2Stiffening electronic packages by disposing a stiffener ring between substrate center area and conductive pad

Publication Date: 2017.09.12 NVIDIA CORP

AI summary

Stiffening is provided for an electronic package assembly having a substrate. A first electronic package, having a first function, is electromechanically fastened to a first surface of the substrate with a first array of electrically conductive interconnects, which is disposed over a central area of the substrate first surface. A second electronic package, having a second function, is fastened to the first substrate surface with a second conductive interconnect array. At least a pair of the first array conductors is electrically coupled to at least a pair of the second array conductors for data/signal exchange and at least a component of the first electronic package interacts with at least a component of the second package. A metallic stiffener ring is disposed about an outer periphery of at least the central area of the substrate.