Optical Chip Alignment via Bond Pad Height Compensation
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Solution Overview
Problem
Semiconductor chip warpage and tilt due to coefficient of thermal expansion mismatch between the chip and the package cause alignment issues during flip-chip mounting, affecting the proper functioning of optical chips and dies.
Innovation Solution
The method involves determining the inclination angle of substrates due to warpage and configuring the size of bond pads to create a joint height difference, which accounts for the inclination, ensuring accurate alignment of optical chips with optical deflectors by adjusting the dimensions of bond pads and pillars to compensate for warpage and tilt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If uniform bond pads are used for mounting, then the manufacturing process is simple, but the chip alignment precision deteriorates due to warpage-induced tilt
Solution Approach 1:
The patent applies local quality by varying the dimensions of bond pads across different locations on the substrate. Specifically, bond pads are configured with different sizes (e.g., larger on one side, smaller on the other) to create differential joint heights that compensate for the tilt caused by warpage. This localized variation in bond pad quality allows each region to address the specific alignment needs caused by the warpage-induced inclination, thereby improving overall chip alignment precision without requiring complex external adjustment mechanisms.
2Manufacturing precision
If bond pad sizes are varied to compensate for tilt, then alignment precision improves, but the manufacturing process complexity increases
Solution Approach 1:
The patent implements parameter changes by systematically varying the dimensional parameters of bond pads (such as diameter or side length) based on their location on the substrate. The bond pad dimensions are specifically designed to create a gradient or stepped pattern that corresponds to the warpage profile. This approach allows the manufacturing process to incorporate warpage compensation directly into the bond pad design parameters, achieving improved optical chip alignment while maintaining compatibility with standard fabrication processes through controlled parameter variation rather than complex assembly steps.
3Reliability
If standard bond pads are used, then the manufacturing process is straightforward, but the joint height difference cannot compensate for warpage-induced inclination
Solution Approach 1:
The patent applies preliminary action by pre-configuring the bond pad dimensions during the substrate fabrication stage to anticipate and compensate for warpage effects before chip mounting occurs. The differential bond pad sizes are designed in advance based on predicted warpage characteristics, creating built-in joint height differences that automatically compensate for the inclination that will develop during cooling. This preliminary configuration ensures alignment reliability is achieved through the design phase rather than requiring post-fabrication adjustment or complex mounting procedures.
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 effectively adjusts the position of optical chips to ensure proper alignment and functionality by controlling chip inclination, allowing optical information signals to pass through channels at the appropriate angle, thereby enhancing the accuracy and effectiveness of semiconductor assemblies.
Implementation Method 1
The plurality of joints comprising a plurality of solder bumps
Implementation Method 2
coefficient of thermal expansion (CTE) mismatch between the chip and the package. Warpage is a global phenomenon
Data Source
AI summary
A method for alignment of a first substrate coupled to a second substrate includes determining an inclination angle for the first substrate or the second substrate due to warpage. The method includes determining a joint height difference based on the inclination angle and configuring a size for one or more bond pads based on the joint height difference.