Metal Trace Extensions for Bump-on-Trace Peeling

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Solution Overview

Problem

Conventional Bump-on-Trace (BOT) structures without a solder mask layer face increased risk of peeling between metal traces and underlying structures, especially when bonded to extreme low-k dielectric layers, which can compromise reliability.

Innovation Solution

Incorporating metal trace extensions that are not covered by solder bumps, these extensions are configured to reduce stress and prevent peeling by extending towards the center of the package substrate, thereby enhancing mechanical support and reliability without increasing stress on low-k dielectric layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If metal trace extensions are added to prevent peeling, then mechanical support is improved, but device complexity increases

Engineering Contradiction:

Improvemechanical supportVSAvoidtrace structure complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The extended metal trace performs multiple functions simultaneously: it provides electrical connection to the solder bump, offers mechanical support to prevent peeling, and acts as a stress distribution element. By making the trace serve multiple purposes, the design avoids adding separate structural support elements, thereby improving strength without proportionally increasing device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The metal trace itself is utilized to provide mechanical support through its extension, rather than requiring a separate support structure. The trace's own geometry is modified to serve the dual purpose of electrical conduction and mechanical reinforcement, allowing the structure to support itself and reducing overall device complexity.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS8970033B2Extending metal traces in bump-on-trace structures

Publication Date: 2015.03.03 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A device includes a work piece, and a metal trace on a surface of the work piece. A Bump-on-Trace (BOT) is formed at the surface of the work piece. The BOT structure includes a metal bump, and a solder bump bonding the metal bump to a portion of the metal trace. The metal trace includes a metal trace extension not covered by the solder bump.