Package Substrate Warpage Control via Preliminary RDL Formation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in semiconductor package technology is warpage reduction in package substrates due to mismatch of Coefficient of Thermal Expansion (CTE) among different material layers during fabrication.
Innovation Solution
Forming a redistribution layer (RDL) before metal pillars are created, and using a thicker core substrate to suppress warpage, followed by forming metal pillars and subsequent layers, including a top and bottom RDL with metal pads and dielectric layers, and encapsulating with a molding compound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a redistribution layer is formed after metal pillars are created (prior art method), then the fabrication process follows conventional sequence, but warpage occurs due to CTE mismatch among different material layers
Solution Approach 1:
The redistribution layer is formed before the metal pillars are created, reversing the conventional sequence. This preliminary formation of the RDL allows the thicker core substrate to suppress warpage that would otherwise occur during subsequent processing steps, while the overall fabrication process remains manageable through systematic reordering of operations
2Stability of the object's composition
If a thicker core substrate is used to suppress warpage, then warpage is effectively reduced during fabrication, but the final package substrate thickness increases
Solution Approach 1:
The redistribution layer is formed preliminarily before metal pillar creation, allowing the thicker core substrate to provide warpage suppression during critical fabrication steps. The subsequent thinning process then removes excess substrate material to achieve the desired final thickness while maintaining the stability benefits gained during fabrication
3Productivity
If multiple material layers with different CTE are processed during fabrication, then circuitry density increases, but warpage management becomes more difficult
Solution Approach 1:
By forming the redistribution layer before creating metal pillars and other subsequent layers, the patent establishes a stable baseline structure early in the fabrication process. This preliminary action allows multiple high-density material layers to be added afterward while the RDL and core substrate combination suppresses cumulative warpage effects
Solution Approach 2:
The patent employs a composite structure consisting of the core substrate and redistribution layer formed in a specific sequence. This composite approach leverages the mechanical properties of different materials to achieve both high circuitry density and effective warpage management through the interaction of layers with different CTE characteristics
Data Source
AI summary
A core substrate is prepared first, a bottom redistribution layer RDL1 is formed. Any warpage of the RDL1 is suppressed by the core substrate. In a later process, warpage is further suppressed by a molding compound encapsulating the core substrate. A plurality of metal pillars are formed passing through the core substrate longitudinally; a top redistribution layer RDL2 is then formed on a top surface of the metal pillars.