Asymmetrical Capture Pad for Flip Chip Copper Column Bonding

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Solution Overview

Problem

Conventional flip chip technologies using copper columns for bonding face challenges with poor bonding contact due to the presence of dimples, which can be exacerbated by increasing the column diameter to improve contact, thereby compromising the advantage of increased bonding area.

Innovation Solution

The use of asymmetrical capture pads plated over via openings in the carrier, allowing copper columns to contact only one side of the capture pads, ensuring no overlap with via openings, thereby enhancing bonding contact and stability while maintaining the advantage of increased bonding area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the diameter of copper columns is increased to improve bonding contact, then bonding contact quality improves, but bonding area advantage is compromised

Engineering Contradiction:

Improvebonding contact qualityVSAvoidbonding area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The capture pad is designed with an asymmetrical shape relative to the via opening, creating a larger bonding surface area on one side. This allows the copper column to make contact with a larger area of the capture pad without increasing the column diameter, thereby maintaining both good bonding contact and maximizing bonding area.

Inventive Principle:

Principle #4Asymmetry

2Reliability

If copper columns are positioned to overlap via openings, then bonding contact area increases, but electrical isolation and structural stability deteriorate

Engineering Contradiction:

Improvebonding contact areaVSAvoidstructural stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The asymmetrical capture pad design positions the majority of the pad area on one side of the via opening, allowing the copper column to contact the capture pad without overlapping the via opening. This maintains electrical isolation while providing sufficient bonding contact area.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The capture pad has different properties in different regions: a larger area on one side for bonding contact and a smaller or absent area over the via opening for electrical isolation. This local differentiation allows the copper column to achieve good contact without compromising structural stability.

Inventive Principle:

Principle #3Local quality

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 approach achieves improved electrical connectivity and mechanical stability by maximizing copper column-capture pad contact without overlapping via openings, allowing for more copper columns on each capture pad and reducing stress on Extra Low K (ELK) layers, thus enhancing the overall performance of the flip chip package.

Implementation Method 1

the capture pad is plated over the via

Methodology Applied

Scientific EffectPlating: Electroplating

Data Source

PatentUS9064757B2Enhanced flip chip structure using copper column interconnect

Publication Date: 2015.06.23 MEDIATEK INC

AI summary

A flip chip package includes a carrier coupled to a die. The carrier includes: at least a via, for coupling the surface of the carrier to electrical traces in the carrier; and at least a capture pad electrically coupled to the via, wherein the capture pad is plated over the via. The die includes: at least a bond pad formed on the surface of the die; and at least a copper column, formed on the bond pad for coupling the die to the capture pad on the carrier, wherein the copper column is disposed on one side of the capture pad about the via opening only.