Tilted Polymer Sidewalls in Fan-Out Packaging for Dense I/O
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Solution Overview
Problem
As semiconductor dies become smaller and more functional, packaging technologies face challenges in increasing the number of I/O pads in a limited area, leading to issues such as solder bridges and limited solder ball packing density.
Innovation Solution
The development of fan-out packages, where the I/O pads on a die are redistributed to a larger area, allowing for increased I/O pad density, and the use of tilted sidewalls in the encapsulating material to facilitate smoother encapsulation and reduce stress on the die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fan-in packaging is used with smaller dies, then throughput and cost are improved, but the number of I/O pads is limited due to area constraints and pitch limitations
Solution Approach 1:
The patent transitions from fan-in packaging (I/O pads confined to die surface area) to fan-out packaging (I/O pads redistributed to a larger area beyond the die boundaries). This dimensional expansion allows the same die to support significantly more I/O pads by utilizing the substrate area rather than being constrained to the die footprint, directly resolving the contradiction between maintaining high throughput and increasing I/O pad quantity.
2Quantity of substance
If I/O pad pitch is decreased to increase pad density, then more pads can be packed, but solder bridges occur
Solution Approach 1:
By redistributing I/O pads to a larger area through fan-out packaging, the patent increases the effective spacing between pads without requiring smaller pitch on the die itself. This maintains solder joint reliability while achieving higher overall pad density, as pads are spread across a larger footprint rather than being compressed into a smaller area.
3Device complexity
If vertical sidewalls are used in encapsulating material, then packaging structure is simple, but stress on die during encapsulation is high
Solution Approach 1:
The patent replaces vertical sidewalls with tilted sidewalls in the encapsulating material structure. This geometric modification distributes the encapsulation stress more evenly across the die surface, reducing peak stress concentrations that would occur with abrupt vertical transitions. The tilted angle provides a gradual transition zone that mitigates mechanical stress while maintaining structural integrity.
4Quantity of substance
If fan-out packaging is used to increase I/O pad area, then I/O pad density is improved, but device complexity increases
Solution Approach 1:
The patent divides the packaging structure into distinct functional layers and regions: the die itself, the encapsulating material with tilted sidewalls, and the substrate area for I/O redistribution. This segmentation allows each component to be optimized independently - the die maintains its original compact design while the surrounding encapsulation and substrate provide the expanded I/O interface, thereby achieving high I/O density without proportionally increasing overall device complexity.
Data Source
AI summary
A method includes forming a polymer layer covering a metal via in a wafer, grooving the wafer to form a trench, wherein the trench extends from a top surface of the polymer layer into the wafer, and performing a die-saw on the wafer to separate the wafer into a plurality of device dies. A kerf passes through the trench. One of the device dies is placed over a carrier. An encapsulating material is dispensed over and around the device die. The method further includes pressing and curing the encapsulating material. After the encapsulating material is cured, a sidewall of the polymer layer is tilted. A planarization is performed on the encapsulating material until the polymer layer and the metal via are exposed. A redistribution line is formed over and electrically coupled to the metal via.