Stacked RDL Die Assembly Without Spacer
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Solution Overview
Problem
The use of spacers in stacked die packages occupies space, limiting the reduction in overall height of electronic component packages, as they are necessary to space upper dies away from lower bond wires connected to the lower die's bond pads.
Innovation Solution
A stacked redistribution layer (RDL) die assembly package design that includes a substrate with first and second level RDL die assemblies, where the second level die assembly is smaller than the first, allowing for effective stacking without a spacer by exposing terminals for wire bonding, thereby minimizing the package height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spacer is used to space the upper die away from the lower bond wires, then the upper die can be properly positioned, but the overall height of the package increases
Solution Approach 1:
The patent removes the spacer component entirely from the package structure. Instead of using a spacer to position the upper die, the design relies on the fan-out support structure and trace routing to provide the necessary spacing and support, eliminating the need for a separate spacer element.
Solution Approach 2:
The fan-out support structure serves multiple functions: it provides mechanical support for the traces, positions the upper die at the correct height, and eliminates the need for a separate spacer. This multi-functional approach reduces overall package height while maintaining proper die positioning.
2Ease of manufacture
If the second level RDL die assembly is made smaller than the first level, then wire bonding is facilitated, but the stacking efficiency is reduced
Solution Approach 1:
The patent uses the horizontal dimension (footprint area) to solve a vertical positioning problem. By making the second level assembly smaller in footprint, the bond wires from the first level remain accessible in the horizontal plane, allowing wire bonding to proceed without interference while maintaining vertical stacking.
Data Source
AI summary
A stacked redistribution layer (RDL) die assembly package includes a substrate, a first level RDL die assembly mounted to the substrate and a second level RDL die assembly mounted to the first level RDL die assembly. The first level RDL die assembly includes a first die comprising bond pads, a first fan out support extending outwardly from sides of the first die, and first traces electrically connected to the bond pads, the first traces being supported by the first fan out support. Similarly, the second level RDL die assembly includes a second die comprising bond pads, a second fan out support extending outwardly from sides of the second die, and second traces electrically connected to the bond pads of the second die, the second traces being supported by the second fan out support.