Flip Chip Package With Metallic Routing Layers

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Solution Overview

Problem

Conventional flip chip packages face challenges such as increased thickness, interference from induced voltages, difficulty in achieving high-density routing, and poor thermal performance due to limitations in substrate materials like leadframe and laminate substrates.

Innovation Solution

The use of a photoresist layer to create very fine metallic traces on a metallic base layer, allowing for high-density routing within a single layer while minimizing thickness and layer count, and incorporating raised metallic pads to support multiple thin routing layers without direct coupling to IC die bond pads, thereby combining the advantages of leadframe and laminate substrates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If laminate substrates are used to provide multiple layers for routing, then routing density is improved, but manufacturing cost increases and thermal performance deteriorates

Engineering Contradiction:

Improverouting densityVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The substrate is divided into two functional layers: a leadframe base layer providing mechanical support and thermal conduction, and a separate routing layer deposited on top providing multiple copper planes for high-density routing. This segmentation allows each layer to optimize its specific function without the compromises of traditional laminate substrates.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite structure combining leadframe material (providing thermal and mechanical properties) with deposited copper routing layers (providing electrical connectivity). This composite approach achieves the routing density of laminate substrates while maintaining the thermal and cost advantages of leadframe construction.

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If laminate substrates are used to provide multiple layers for routing, then routing density is improved, but thermal performance worsens

Engineering Contradiction:

Improverouting densityVSAvoidthermal performance

Core Design Contradiction:

Manufacturing precisionVSTemperature

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The leadframe substrate maintains its homogeneous metallic structure throughout, ensuring consistent thermal conduction paths from the IC die through the substrate. Unlike laminate substrates with heterogeneous materials (organic core + metal traces), the homogeneous metal construction provides superior and uniform thermal performance.

Inventive Principle:

Principle #33Homogeneity

3Ease of manufacture

If leadframe substrates are used for routing, then manufacturing cost is reduced, but routing density is limited due to single layer constraint

Engineering Contradiction:

Improvemanufacturing costVSAvoidrouting density

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The invention transitions from two-dimensional routing on a single leadframe layer to three-dimensional routing by depositing multiple copper layers on top of the leadframe substrate. This vertical stacking of routing layers enables high-density routing comparable to laminate substrates while maintaining leadframe cost advantages.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

Inventive Principle:

Principle #1Segmentation

4Device complexity

If conventional flip chip packages are used, then package structure is simplified, but thickness increases due to substrate requirements

Engineering Contradiction:

Improvepackage structureVSAvoidpackage thickness

Core Design Contradiction:

Device complexityVSLength of stationary object

Solution Approach 1:

The invention replaces thick laminate substrates with thin deposited copper routing layers on a flexible leadframe substrate. This thin-film approach reduces the overall package thickness while maintaining the necessary routing functionality, enabling more compact flip chip packages.

Inventive Principle:

Principle #30Flexible shells and thin films

Data Source

PatentUS9153530B2Thermal enhanced high density flip chip package

Publication Date: 2015.10.06 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

Systems and methods according to embodiments of the invention enable flip chip packaging using high density routing while minimizing the thickness and layer count of the flip chip package. By using a photoresist layer to create very fine traces on a metallic base layer, embodiments of the present invention combine advantages of leadframe substrates and laminate substrates by supporting high-density routing while minimizing layer count and manufacturing cost. Additionally, the use of raised metallic pads in a routing layer enables embodiments of the present invention to include highly compact traces that pass over IC die bond pad connection sites without directly coupling to these bond IC die bond pad connection sites. Further, embodiments of the present invention can support multiple thin routing layers without the need for organic (e.g., laminate) material separating these routing layers.