Open Cavity Bridge Placement for EMIB Bump Height Control
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Solution Overview
Problem
Embedded multi-die interconnect bridges (EMIBs) face challenges with high cumulative bump thickness variation (BTV), which worsens as more EMIBs are included in a package and as their sizes increase, and using a glass patch to reduce BTV is not effective due to low thermal conductivity, requiring alternative bonding techniques that increase bump pitch and necessitate redistribution layers, which negate the BTV benefits.
Innovation Solution
The implementation of an open cavity bridge architecture with co-planar placement of bridge dies, using pre-filled underfill/glue to adjust cavity depth, solder with accurate volume control, and excess adhesive management through trenches and reservoirs to maintain processing flexibility and prevent adhesive overflow, allowing for correct Z-height alignment and thermal compression bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If EMIBs are used to provide fine die-to-die interconnects, then integration performance is improved, but cumulative bump thickness variation (BTV) increases
Solution Approach 1:
The patent applies preliminary action by pre-filling the cavity with underfill material before placing the bridge die. This pre-filled cavity provides a controlled thickness foundation that compensates for subsequent bump thickness variations, thereby maintaining manufacturing precision while enabling high integration performance with multiple EMIBs.
2Manufacturing precision
If a glass patch is used to reduce BTV, then bump thickness variation is improved, but thermal conductivity deteriorates
Solution Approach 1:
The patent extracts the glass patch from the design and replaces it with a cavity structure filled with underfill material. This removal eliminates the thermal conductivity problem while maintaining the BTV reduction benefit, as the underfill provides controlled thickness without the thermal insulation issues of glass.
Solution Approach 2:
The patent changes the material parameter from glass to underfill material in the cavity structure. This parameter change maintains the thickness control function (reducing BTV) while improving thermal conductivity, since underfill materials have better thermal properties than glass.
3Ease of manufacture
If alternative bonding techniques are used due to low thermal conductivity, then bonding process is adapted, but bump pitch increases
Solution Approach 1:
The patent replaces the thermal compression bonding process with a simplified placement process on a pre-filled cavity. This substitution eliminates the need for high-temperature bonding, allowing maintenance of fine bump pitch while adapting the manufacturing process to a lower-temperature placement technique that avoids the thermal conductivity limitations.
4Ease of manufacture
If pitch of mid-level interconnects is increased to accommodate alternative bonding, then bonding flexibility is improved, but redistribution layers are required
Solution Approach 1:
The patent applies preliminary action by pre-filling the cavity with underfill material before bridge die placement. This preliminary preparation provides a controlled thickness foundation that enables direct bonding without requiring additional redistribution layers, thereby maintaining manufacturing flexibility while reducing device complexity.
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 lower cost, high bandwidth solutions by maintaining wider pitch processing, scaling to finer features, and avoiding thickness constraints, while minimizing complexity and heat conduction issues during thermocompression bonding.
Implementation Method 1
An adhesive layer couples the bridge die to the bottom of the open cavity
Implementation Method 2
thermocompression bonding
Data Source
AI summary
Embodiments disclosed herein include multi-die packages with open cavity bridges. In an example, an electronic apparatus includes a package substrate having alternating metallization layers and dielectric layers. The package substrate includes a first plurality of substrate pads and a second plurality of substrate pads. The package substrate also includes an open cavity between the first plurality of substrate pads and the second plurality of substrate pads, the open cavity having a bottom and sides. The electronic apparatus also includes a bridge die in the open cavity, the bridge die including a first plurality of bridge pads, a second plurality of bridge pads, and conductive traces. An adhesive layer couples the bridge die to the bottom of the open cavity. A gap is laterally between the bridge die and the sides of the open cavity, the gap surrounding the bridge die.