Copper Adhesion to Dielectric Using Partially Cured Epoxy Microspheres
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Solution Overview
Problem
The adhesion of copper metallization to dielectric materials in integrated circuit packages is challenging due to the shrinking width of copper traces, as higher average roughness alone does not necessarily result in better adhesion or higher peel strength, and existing methods like desmear are insufficient to ensure strong mechanical bonding.
Innovation Solution
Incorporating partially cured epoxy microspheres into the dielectric material, which are preferentially etched during the desmear process to create microsphere cavities, allowing for deeper copper penetration and improved mechanical anchoring, thereby enhancing the adhesion of copper plating to the dielectric substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If copper trace width is reduced to increase circuit density, then productivity and functionality are improved, but adhesion of copper to dielectric becomes more difficult
Solution Approach 1:
The patent introduces a porous dielectric material containing cavities or voids that preferentially etch during the desmear process. This creates an enhanced roughness profile with deeper anchors for copper plating, improving adhesion strength while allowing reduced copper trace widths for higher circuit density.
Solution Approach 2:
The patent applies local quality by creating non-uniform roughness distribution through the porous dielectric structure. The cavities provide localized deep anchors at critical adhesion points while maintaining smoother regions elsewhere, optimizing the balance between adhesion strength and copper trace geometry for high-density circuits.
2Strength
If average roughness is increased to improve adhesion, then adhesion may be enhanced, but peel strength does not necessarily improve and surface profile control becomes more difficult
Solution Approach 1:
The porous dielectric material provides a controlled roughness profile through its cavity structure. The desmear process selectively etches these cavities to create consistent deep anchors with controlled depth and distribution, improving both adhesion strength and peel strength while maintaining manufacturing precision through repeatable cavity formation.
Solution Approach 2:
The dielectric material is formulated as a composite containing organic polymer matrix and inorganic filler particles, creating a porous structure that combines the benefits of polymer etchability with inorganic structural stability. This composite structure enables controlled cavity formation that improves adhesion while maintaining surface profile control.
3Strength
If desmear process is applied to increase surface roughness, then adhesion is promoted, but higher average roughness alone does not ensure better adhesion or higher peel strength
Solution Approach 1:
The porous dielectric with controlled cavities transforms the desmear process outcome from random surface roughness to structured deep anchors. The cavities etch preferentially to create consistent penetration depths that reliably improve both adhesion strength and peel strength, overcoming the limitations of conventional desmear approaches.
Solution Approach 2:
The patent changes the physical parameters of the dielectric material by incorporating porous structure with specific cavity size distributions (e.g., 0.1-10 micrometers). This parameter change ensures that the desmear process creates optimal anchor depths for copper plating, reliably improving peel strength beyond what conventional smooth or uniformly rough surfaces achieve.
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 results in improved mechanical adhesion and higher peel strength between copper metallization and dielectric materials, enabling more reliable and durable integrated circuit packages by creating a controlled roughness profile and deep anchors for copper plating.
Implementation Method 1
treating an organic substrate surface with a sweller to infiltrate polymer free volume and prepare the surface for oxidation
Implementation Method 2
an oxidizing agent such as permanganate or chromate to promote micro roughness by oxidizing polar species on the surface and near the surface of the dielectric
Implementation Method 3
a neutralizer to remove any reaction by-products or solvents from the previous steps and de-swell the matrix
Implementation Method 4
Adhesion is strongly dependent on the surface profile formed on the surface after desmear
Data Source
AI summary
In some embodiments, an improved mechanical adhesion of copper metallization to dielectric with partially cured epoxy fillers is presented. In this regard, a substrate build-up film is introduced having epoxy material and a plurality of epoxy microspheres, wherein an interior of the microspheres is not fully cured. Other embodiments are also disclosed and claimed.