Slanted Die Stack Assembly for Overhang Warpage Mitigation
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Solution Overview
Problem
Semiconductor die stacks experience deformation, such as bending, sagging, and warping, leading to defects and electrostatic discharge events due to overhanging portions, which can increase the risk of electrical failures and damage.
Innovation Solution
Implementing a slanted die stack orientation relative to the mounting surface, shifting the neutral axis to a slanted plane, reduces deformation and pressure on lower dies, and creates a gap to prevent contact with underlying devices, using a slanted spacer and shorter bond wires to minimize material cost and manufacturing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a die stack is arranged horizontally on a mounting surface, then the structure is simple and easy to manufacture, but the overhanging portion deforms due to pressure from upper dies causing warpage and electrostatic discharge
Solution Approach 1:
The die stack is oriented at an angle (e.g., 45 degrees) relative to the mounting surface rather than horizontally, creating an asymmetric configuration. This angular orientation shifts the neutral axis to a slanted plane, reducing deformation and warpage in the overhanging portion while preventing electrostatic discharge events.
2Manufacturing precision
If the die stack is oriented at an angle to reduce warpage, then deformation is minimized, but the manufacturing process becomes more complex
Solution Approach 1:
A slanted spacer structure is formed on the mounting surface before the die stack is assembled. This pre-formed angled support structure facilitates the angular orientation of the die stack, reducing warpage and deformation while simplifying the overall assembly process by providing a ready-made guiding structure.
3Stability of the object's composition
If a slanted spacer is used to support the die stack, then warpage is reduced, but the device complexity increases
Solution Approach 1:
The slanted spacer has a curved or angled upper surface that matches the desired orientation of the die stack. This curved geometry provides mechanical support while guiding the die stack into the correct angular position, reducing warpage and improving structural stability without requiring complex external fixtures.
4Reliability
If longer bond wires are used to connect the slanted die stack, then electrical connections are maintained, but material cost and manufacturing time increase
Solution Approach 1:
The die stack is oriented at an angle rather than horizontally, which changes the spatial dimension of the bond wire routing. This angular configuration allows bond wires to connect to the die stack more directly, reducing the required wire length while maintaining reliable electrical connections and lowering material costs.
Data Source
AI summary
A semiconductor device assembly includes a circuit substrate including a first substrate surface and a second substrate surface; a wedge structure arranged on the first substrate surface, wherein the wedge structure has a slanted upper surface that is slanted with respect to the first substrate surface; a die stack arranged on the slanted upper surface, wherein the die stack comprises a plurality of dies, wherein the die stack is oriented at an angle corresponding to the slanted upper surface, and wherein the die stack has a first lateral portion coupled to the slanted upper surface and a second lateral portion that overhangs from the slanted upper surface; a package casing disposed over the first substrate surface, wherein the package casing encapsulates the die stack and covers at least part of the first substrate surface; and a plurality of conductive interconnect structures coupled to the second substrate surface.