Package Redistribution Layer Via Routing for Stress Mitigation
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Solution Overview
Problem
Wafer level packaging technologies face challenges with shear and peeling stress in package redistribution layers, particularly when formed with soft dielectric materials, leading to potential failure of vias closest to the electronic component due to smaller dimensions and stress concentration.
Innovation Solution
The implementation of via lines with greater line width and longitudinal length than line width, along with staggered, U-turn, cantilever, symmetrical, and jogged routing configurations within the package redistribution layer to mitigate stress, including arrangements that distribute stress over a larger area and provide alignment tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If via dimensions are reduced to increase pin count and shrink package size, then package density and integration are improved, but stress concentration and reliability of vias deteriorate
Solution Approach 1:
The via structure is segmented into multiple components: a via opening through the dielectric layer, a via liner coating the via opening walls, and a via fill material. This segmentation allows each component to be optimized independently - the via liner and fill material can be designed to mitigate stress while maintaining small overall via dimensions for high density packaging.
Solution Approach 2:
The via structure uses composite materials consisting of a via liner material (such as tungsten, copper, or cobalt) combined with a via fill material. This composite approach enables the via to simultaneously achieve small dimensions for high density and enhanced mechanical properties for stress mitigation in miniature packages.
2Adaptability or versatility
If via dimensions are reduced to increase pin count, then integration capability is improved, but stress concentration increases leading to via failure
Solution Approach 1:
The via structure implements local quality by applying a via liner specifically to the via opening walls and using different fill materials in different regions. This allows the local area around the via to have enhanced strength and stress resistance properties, while the overall via dimension remains small for high integration capability.
Solution Approach 2:
The via uses composite materials with the via liner providing localized reinforcement at the stress concentration points (via walls) while the fill material provides structural integrity. This composite structure enables small via dimensions for high integration while maintaining sufficient strength through material composition rather than size.
3Ease of manufacture
If soft dielectric materials are used for package RDL, then manufacturing ease and cost are improved, but stress mitigation capability deteriorates
Solution Approach 1:
The package RDL uses a composite structure combining soft dielectric materials (easy to manufacture) with reinforced via structures (high stress resistance). The via liner and fill material create a composite via that can withstand stress concentrations while the soft dielectric provides manufacturing ease and cost benefits.
Solution Approach 2:
The via liner acts as a beforehand cushioning layer that prevents stress concentration at the via-dielectric interface. This protective layer is applied in advance during manufacturing, cushioning against the stress that will occur during package operation, especially important when using soft dielectric materials that may deform more easily.
Data Source
AI summary
Electronic packages and electronic systems are described in which a package redistribution layer of the electronic package includes structural features such a via line connections to reduce stress concentration, particularly when the package redistribution layer is formed of organic dielectric materials.