Multi-Chip Module Assembly Using Sacrificial Alignment Features
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Solution Overview
Problem
Existing 3D chip stacking techniques face challenges in achieving ultra-high alignment accuracy and high-throughput manufacturing due to difficulties in chip-to-wafer and chip-to-chip bonding, particularly with the target pad size/pitch decreasing to 5-10 μm, which increases the cost and complexity of multi-chip systems.
Innovation Solution
A multi-chip module (MCM) assembly technique that uses a negative feature on one substrate and a positive feature, such as a spherically shaped coupling component, with a bulk modulus less than the substrates, to facilitate mechanical coupling and alignment, allowing for accurate alignment in the XY plane and co-planarity control, and sacrificing the positive feature to achieve Z-direction alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing flip-chip bonders are used to achieve alignment accuracy of ±1-3 μm, then alignment precision is improved, but manufacturing throughput deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-forming sacrificial features (such as sacrificial material in recesses or protrusions) on the substrates before the bonding process. These pre-formed features automatically provide alignment guidance when substrates are brought together, eliminating the need for complex real-time alignment systems during bonding, thus improving throughput while maintaining precision.
Solution Approach 2:
The patent uses sacrificial features as intermediary elements that facilitate alignment between substrates. These features act as temporary mediators during the bonding process, providing mechanical guidance and alignment references that simplify the bonding operation and enable high throughput without sacrificing alignment accuracy.
2Manufacturing precision
If alignment techniques ensuring high bonding accuracy are used, then manufacturing precision is improved, but manufacturing time increases
Solution Approach 1:
The patent implements self-service by designing substrates with self-aligning sacrificial features that automatically guide alignment during bonding. The features themselves (such as interlocking protrusions and recesses) perform the alignment function without requiring external alignment equipment or complex control systems, thereby reducing bonding time while maintaining high accuracy.
Solution Approach 2:
The sacrificial features are prepared in advance on the substrates, creating predetermined alignment paths and reference points. This preliminary preparation eliminates the need for time-consuming alignment adjustments during the bonding process, directly reducing bonding time while ensuring consistent high accuracy.
3Manufacturing precision
If low manufacturing throughput is accepted, then alignment accuracy can be maintained, but assembly cost increases
Solution Approach 1:
The patent employs sacrificial features made from inexpensive materials that are intentionally designed to be temporary or consumable during the bonding process. These cheap sacrificial elements (such as organic materials or soft metals) provide precise alignment guidance but are sacrificed or removed after serving their alignment purpose, enabling high-volume manufacturing at low cost without compromising alignment accuracy.
Solution Approach 2:
The patent applies the discarding principle by intentionally sacrificing the sacrificial features after they have fulfilled their alignment function. These features are discarded after bonding, as their temporary presence enables high-accuracy alignment at low manufacturing cost and high throughput. The sacrificial nature allows the system to achieve precision without the high costs associated with reusable precision alignment systems.
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 technique enhances alignment accuracy, increases manufacturing throughput, and reduces assembly costs, enabling the integration of smaller TSVs with lower capacitance and higher communication bandwidth, while improving manufacturing tolerance and reducing yield loss.
Implementation Method 1
the first material may have been, at least in part, mechanically compressed and/or melted when the mechanical coupling was established
Implementation Method 2
the first material may have been, at least in part, mechanically compressed and/or melted when the mechanical coupling was established
Data Source
AI summary
A multi-chip module (MCM) is described. This MCM includes two substrates, having facing surfaces, which are mechanically coupled. Disposed on a surface of a first of these substrates, there is a negative feature, which is recessed below this surface. A positive feature in the MCM, which includes an assembly material other than a bulk material in the substrates, at least in part mates with the negative feature. For example, the positive feature may be disposed on the surface of the other substrate. Alternatively, prior to assembly of the MCM, the positive feature may be a separate component from the substrates (such as a micro-sphere). Note that the assembly material has a bulk modulus that is less than a bulk modulus of the material in the substrates. Furthermore, at least a portion of the positive feature may have been sacrificed when the mechanical coupling was established.