Fan-Out Flexible Package With Compliant RDL and Flex Notch
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Solution Overview
Problem
Current electronic packaging solutions struggle to integrate high performance and features into increasingly smaller spaces of portable devices, where available module substrate area is restricted, and traditional flexible PCBs lack sufficient flexibility and manufacturing simplicity.
Innovation Solution
The development of flexible packages with a compliant redistribution layer (RDL) spanning a molding compound layer, including electrical routing on die landing pads, and a notch in the molding compound layer to facilitate flexibility, allowing for 3D configurations and integration with non-planar landing areas without relying on a flexible substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional rigid PCBs are used, then structural stability is maintained, but flexibility and adaptability to non-planar configurations are lost
Solution Approach 1:
The package structure is divided into discrete components: rigid dies, a molding compound layer, and a compliant RDL. This segmentation allows each component to fulfill its specific function - the dies provide stable computational cores, the molding compound provides structural support, and the compliant RDL provides flexibility for routing, thereby resolving the contradiction between overall structural stability and local flexibility.
Solution Approach 2:
The package employs a composite structure combining rigid materials (dies, molding compound) with a compliant material (RDL). This composite approach enables the package to maintain structural integrity from the rigid components while achieving flexibility through the compliant RDL layer, effectively resolving the contradiction between stability and flexibility.
2Adaptability or versatility
If flexible substrate is used to achieve flexibility, then adaptability to non-planar configurations is improved, but manufacturing complexity increases
Solution Approach 1:
The invention extracts the flexibility function from the substrate and relocates it to the RDL layer. By taking out the flexibility requirement from the entire flexible PCB concept and implementing it specifically in the RDL through a compliant layer with notches, the solution achieves flexibility without the manufacturing complexity of traditional flexible substrates.
Solution Approach 2:
The RDL is designed with local compliance - the molding compound layer includes notches at specific locations where flexibility is needed, while other areas maintain rigidity. This local quality approach allows the package to be flexible only where necessary for routing, rather than requiring the entire structure to be flexible, thereby reducing manufacturing complexity.
3Adaptability or versatility
If more performance and features are integrated, then functionality is improved, but available module substrate area is reduced
Solution Approach 1:
The package transitions from a two-dimensional planar layout to a three-dimensional vertical stacking architecture. Multiple dies are stacked vertically and connected through the compliant RDL and molding compound, enabling more functionality to be integrated within a smaller footprint by utilizing the vertical dimension rather than requiring additional horizontal substrate area.
Data Source
AI summary
Flexible packages and electronic devices with integrated flexible packages are described. In an embodiment, a flexibly package includes a first die and a second die encapsulated in a molding compound layer. A compliant redistribution layer (RDL) spans the molding compound layer and both dies, and includes electrical routing formed directly on landing pads of the dies. A notch is formed in the molding compound layer between the dies to facilitate flexure of the compliant RDL.