Copper Column Flip Chip Asymmetrical Capture Pad Design
Find Innovative SolutionsGenerate Solutions
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 are exacerbated by the smaller diameter of copper columns compared to solder bumps, leading to reduced bonding area and mechanical stability issues.
Innovation Solution
The use of copper columns where part overhangs the via opening, with asymmetrical capture pads plated to accommodate the copper columns, ensuring better contact and stability by positioning the copper columns to contact capture pads on one side of the via, allowing for improved electrical connectivity and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If copper columns with smaller diameter are used to replace solder bumps, then bonding area is freed up, but bonding contact quality deteriorates due to poor contact with dimpled capture pads
Solution Approach 1:
The capture pad is designed with an asymmetrical shape that is larger on one side than the other. The copper column is positioned to contact the capture pad at the larger side, away from the via opening. This asymmetrical design allows the copper column to have a smaller diameter (freeing bonding area) while still achieving good bonding contact with the enlarged capture pad surface.
2Reliability
If copper columns are positioned to contact capture pads on one side of via openings, then bonding contact is improved, but structural symmetry is reduced
Solution Approach 1:
The invention deliberately introduces asymmetry into the capture pad design and copper column positioning. The capture pad is made larger on one side of the via opening, and the copper column is positioned to contact this larger area. This intentional asymmetry resolves the contradiction by prioritizing bonding contact quality over structural symmetry.
3Ease of manufacture
If conventional symmetrical capture pads are used, then manufacturing is simpler, but bonding contact is poor due to dimple formation
Solution Approach 1:
Instead of making the entire capture pad asymmetrical throughout, the invention applies local quality by enlarging only the specific region of the capture pad where the copper column contacts it. The rest of the capture pad can maintain conventional dimensions. This localized modification improves bonding contact while minimizing manufacturing complexity.
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 configuration enhances bonding contact and mechanical stability, freeing up bonding area while reducing stress on Extra Low K (ELK) layers, leading to improved electrical connectivity and reduced potential for cracks, thus creating a more reliable flip chip package structure.
Implementation Method 1
The copper columns enable electrical coupling to traces in the carrier by means of capture pads and vias
Implementation Method 2
each copper column has a solder bump at one end for contacting the capture pad
Data Source
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 part of the copper column overhangs the via opening.