Stacked PCB Die Module With Cavity Structure for Lower Height
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Solution Overview
Problem
The challenge is to reduce the size and height of solid-state modules in electronic devices, particularly due to the limitations imposed by the height of components like high Q inductors on printed circuit boards, which hinder the miniaturization of these modules.
Innovation Solution
The solution involves stacking dies on a printed circuit board with a cavity, where the first die is stacked over a second die, and both are flip-chip mounted to reduce the overall module height, with the use of interposers and molding compounds to enhance mechanical and electrical connections, and the exposure of the top die surface by grinding to minimize the module's height further.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dies and passive components are mounted on PCB top surface next to each other, then module functionality is achieved, but module size in x and y directions increases
Solution Approach 1:
The patent transitions from planar mounting of dies and components on the PCB top surface to three-dimensional stacking, where dies are mounted vertically one above another. This dimensional change allows multiple functional components to occupy the same footprint area, thereby reducing the module's x-y plane size while maintaining full functionality.
Solution Approach 2:
The patent implements nesting by placing the second die inside a cavity formed in the PCB substrate, and positioning the first die above the second die. This nested arrangement allows components to be contained within each other's spatial envelope, maximizing space utilization and minimizing the overall module footprint.
2Adaptability or versatility
If tall SMT components like high Q inductors are mounted on PCB, then required electrical functionality is achieved, but module height in z direction increases
Solution Approach 1:
The patent relocates passive components from vertical SMT mounting (z-direction height) to horizontal integration within the PCB plane and cavity structures. By forming cavities in the PCB and mounting components within these recesses, the effective height contribution of passive components is minimized while their electrical functionality is preserved.
Solution Approach 2:
The patent uses flip-chip dies with integrated passive elements that replicate the functionality of discrete tall SMT components like inductors and filters, but in a compact form factor. The flip-chip technology enables these functions to be embedded in the die structure itself, eliminating the need for tall external components.
3Area of stationary object
If die stacking is implemented to reduce module footprint, then module size in x and y directions decreases, but device complexity increases
Solution Approach 1:
The patent introduces an interposer as an intermediary substrate that facilitates the stacking of multiple dies. The interposer provides a standardized interface between dies with different pin configurations, simplifies the interconnection process, and manages the complexity of vertical integration. This mediator layer makes the stacking architecture more manageable and manufacturable.
Solution Approach 2:
The patent divides the module into distinct functional segments (first die, second die, PCB cavity, interposer) that can be manufactured and tested separately before final assembly. This segmentation allows each component to be optimized independently and simplifies the overall manufacturing process by enabling modular assembly of the stacked structure.
Data Source
AI summary
A module is described. The module includes two dies which are stacked over a top insulating layer of a PCB. When both dies are be connected to the PCB through a copper pillar, the top die has a taller interconnect and the bottom die has a shorter interconnect. To further reduce a height of the module, the bottom die and/or the top die may be placed into a cavity of the PCB and a bulk silicon layer of the top die may be grinded away.