Semiconductor Package RDL Recesses Prevent Solder Bridging
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Solution Overview
Problem
Current semiconductor packaging methods face challenges in achieving efficient and cost-effective integration of multiple semiconductor devices within a single package, particularly in preventing solder bridging between contact pads during reflow processes.
Innovation Solution
The method involves forming recesses around the perimeter of contact pads in a second redistribution layer (RDL) within the packaged semiconductor device, using wafer level packaging techniques to create a package-on-package (PoP) or system-in-a-package (SiP) configuration, which prevents solder bridging and enhances manufacturing yields without requiring additional lithography masks or processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wafer level packaging is used to integrate multiple semiconductor devices, then packaging efficiency and integration density are improved, but solder bridging between contact pads occurs during reflow processes
Solution Approach 1:
The contact pad structure is segmented by forming recesses around the perimeter of each contact pad in the second RDL. This segmentation creates isolated regions that prevent solder from bridging between adjacent contact pads during reflow, while maintaining the overall integration density of the wafer level packaging approach.
Solution Approach 2:
The recesses formed in the second RDL act as intermediary structures between adjacent contact pads. These recesses create physical barriers that mediate the solder flow during reflow, preventing direct contact between solder on neighboring pads while still allowing the compact PoP or SiP configuration to be achieved.
2Reliability
If traditional packaging methods are used, then solder bridging is avoided, but integration density and packaging efficiency decrease
Solution Approach 1:
Instead of relying solely on lateral spacing between contact pads (2D approach), the invention introduces a vertical dimension by forming recesses into the second RDL. This dimensional change creates depth-based isolation that prevents solder bridging while maintaining the close proximity needed for high integration density in PoP and SiP configurations.
3Reliability
If additional lithography masks or processes are used to prevent solder bridging, then reliability is improved, but manufacturing complexity and costs increase
Solution Approach 1:
The formation of recesses around contact pads is merged with the existing second RDL fabrication process. The same lithography and etching steps used to create the second RDL pattern are utilized to define the recesses, eliminating the need for additional masks or separate processing sequences. This integration maintains reliability improvement while avoiding increased manufacturing complexity.
Solution Approach 2:
The second RDL layer serves multiple functions: it provides electrical redistribution and simultaneously creates the recess structures that prevent solder bridging. This multi-functionality eliminates the need for dedicated anti-bridging structures or additional process steps, reducing manufacturing complexity while maintaining reliability.
Data Source
AI summary
Packaged semiconductor devices and packaging methods are disclosed. In some embodiments, a packaged semiconductor device includes an integrated circuit die and through-vias disposed in a molding compound. A first redistribution layer (RDL) is disposed over a first side of the through-vias, the integrated circuit die, and the molding compound. A second RDL is disposed over a second side of the through-vias, the integrated circuit die, and the molding compound. Contact pads are disposed over the second RDL. An insulating material of the second RDL includes a recess around a perimeter of one of the contact pads.