Cavity BGA Substrate for Flip Chip Die Stack Integration
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Solution Overview
Problem
Existing methods for passive device integration, such as back side on active side die stacking with wire bond interconnection or surface mount on laminate substrates, limit direct electrical connections between mother and daughter dies, preventing efficient integration and PCB real estate reduction.
Innovation Solution
A method involving flip chip attachment of a mother die and a smaller daughter die to a laminate substrate with a laser-drilled cavity, allowing direct active surface contact and forming an inverted pyramid die stack, which is then attached to a Ball Grid Array or Land Grid Array substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If back side on active side die stacking with wire bond interconnection is used, then passive device integration is achieved, but direct electrical connection between mother and daughter die is limited
Solution Approach 1:
The patent extracts and eliminates the wire bond interconnection layer from the traditional stacking method. By directly bonding the active surface of the daughter die to the active surface of the mother die, the intermediate wire bond structure is removed, enabling direct electrical connection and simplifying the integration structure.
Solution Approach 2:
The patent inverts the traditional stacking approach by placing the daughter die's active surface in direct contact with the mother die's active surface, rather than using the conventional back-side-to-active-side configuration. This inversion enables direct electrical connection while maintaining integration functionality.
2Area of stationary object
If surface mount of passive components to top layer of laminate substrate is used, then integration is achieved, but PCB real estate reduction is limited
Solution Approach 1:
The patent transitions from two-dimensional surface mounting to three-dimensional vertical stacking. By stacking the daughter die directly on the mother die in the vertical dimension, the solution achieves significant PCB real estate reduction while maintaining manufacturing feasibility through direct bonding processes.
3Manufacturing precision
If laser or mechanical drilling of cavity into laminate substrate with BT core is performed, then cavity creation is achieved, but mechanical and reliability integrity may be compromised
Solution Approach 1:
The patent replaces mechanical drilling with laser drilling for cavity creation in the laminate substrate. Laser drilling achieves precise cavity positioning and dimensions while minimizing mechanical stress and damage to the substrate, thereby maintaining both manufacturing precision and substrate integrity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables better electrical performance and reduces PCB space requirements by allowing direct electrical connections between dies, while advancements in substrate drilling ensure accurate cavity creation without mechanical damage or package dimension increase.
Implementation Method 1
a laser drilled cavity laminate Ball Grid Array/Land Grid Array substrate
Data Source
AI summary
An integrated passive device and power management integrated circuit are directly connected, active surface to active surface, resulting in a pyramid die stack. The die stack is flip-chip attached to a laminate substrate having a cavity drilled therein wherein the smaller die fits into the cavity. The die to die attach is not limited to IPD and PMIC and can be used for other die types as required.