Redistribution Layer Roughness for Fan-Out Package Delamination
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Solution Overview
Problem
Fan-out packaging structures in electronic devices face issues with delamination and peeling due to stress at material interfaces, particularly at the redistribution layer and conductive pad junctions, compromising the reliability of the packaging.
Innovation Solution
The electronic device incorporates a redistribution structure with conductive layers, a polymer layer, and bumps, where the conductive layers have a side surface with roughness of 0.08 μm to 0.8 μm, and the conductive pad center is horizontally shifted, along with curved edges and specific ratios and thicknesses to distribute stress radially, enhancing adhesion and reducing peeling risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fan-out packaging structure is used to increase integration density, then the integration density of electronic components is improved, but the reliability deteriorates due to delamination and peeling at material interfaces
Solution Approach 1:
The patent applies local quality by creating a roughness structure specifically at the interface between the conductive layer and polymer layer. This localized surface modification (with roughness Rz of 0.05-1.0 μm) enhances adhesion only where needed, without affecting the overall packaging structure. The roughness is formed by selective etching or plasma treatment of the conductive layer surface, creating anchor points for the polymer layer that prevent delamination while maintaining the fan-out packaging's high integration density.
Solution Approach 2:
The patent employs composite materials by combining the conductive layer (copper or aluminum) with the polymer layer (molding compound or encapsulant) through a controlled interface. The interface composite structure consists of the roughened conductive layer surface combined with the polymer matrix, creating a hybrid structure that leverages the electrical conductivity of metals and the mechanical protection of polymers while preventing interfacial failure through the roughness-induced mechanical interlocking.
2Adaptability or versatility
If heterogeneous material interfaces are increased to achieve fan-out packaging functionality, then the functional integration is improved, but the stress concentration increases leading to delamination
Solution Approach 1:
The patent applies parameter changes by modifying the surface roughness parameter of the conductive layer interface. The roughness height (Rz) is controlled within a specific range (0.05-1.0 μm) to optimize the balance between adhesion enhancement and stress distribution. This parameter optimization allows the interface to accommodate thermal expansion differences and mechanical stresses while maintaining strong bonding, thus reducing delamination risk in the heterogeneous fan-out packaging structure.
Solution Approach 2:
The patent utilizes curvature by creating a roughened surface topology on the conductive layer. The surface is transformed from flat to curved/irregular through etching or plasma treatment, forming micro-scale protrusions and recesses. This curved interface geometry increases the contact area and creates mechanical interlocking with the polymer layer, distributing stresses more evenly across the interface rather than concentrating them at a flat boundary.
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
The solution effectively reduces the risk of peeling and improves the reliability of the electronic device by distributing stress evenly, maintaining impedance, and increasing the buffering capacity of the polymer layer, thereby enhancing the structural integrity.
Implementation Method 1
The side surface has a side edge having roughness of 0.08 μm to 0.8 μm in a cross-sectional view
Data Source
AI summary
An electronic device is provided. The electronic device includes an electronic element; a conductive pad disposed on the electronic element and electrically connected to the electronic element; and a redistribution structure disposed on the conductive pad. The redistribution structure includes a plurality of conductive layers; a polymer layer enclosing the conductive layers; and a bump electrically connected to the conductive pad through the conductive layers. The center of the conductive pad is horizontally shifted from the center of the bump. The conductive layers include a first conductive layer. The first conductive layer has a side surface contacting the polymer layer, and the side surface has a side edge having roughness of 0.08 μm to 0.8 μm in a cross-sectional view.