Optimized Solder Pads for Opto-Electronic Chip Alignment
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Solution Overview
Problem
The challenge in semiconductor chip assembly is achieving precise alignment and uniform solder distribution for optoelectronic chips, as excessive or insufficient solder can lead to electrical shorts or fragile connections, exacerbated by the miniaturization of components and sensitivity to over- or under-plating during soldering processes.
Innovation Solution
The implementation of optimized solder pads with a flow resistor and reservoir pad configuration, where the solder pad is plated with a higher height than the reservoir solder material, allowing for controlled solder flow and alignment through surface tension forces during the melting process, ensuring proper vertical and horizontal alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder material is deposited on UBM pads to form plated solder pads, then electrical and mechanical connections are established, but uniformity of solder plating becomes difficult to control, leading to potential defects or system failure
Solution Approach 1:
The patent applies local quality by creating a non-uniform solder pad structure with varying heights. The solder pad includes a first region with a first height and a second region with a second height different from the first height. This local variation in height allows different regions of the same solder pad to serve different functions: the taller region ensures reliable connection while the shorter region prevents defects, thereby achieving both connection integrity and manufacturing precision.
2Reliability
If more solder material is used to ensure complete electrical connection, then connection reliability improves, but spurious contacts between adjacent solder bumps occur, resulting in shorts
Solution Approach 1:
The patent uses local quality to differentiate the function of different regions on the solder pad. The first region with greater height ensures complete electrical connection and mechanical strength, while the second region with lesser height acts as a barrier to prevent solder from spreading to adjacent pads. This spatial differentiation of height solves the contradiction between ensuring complete connection and preventing spurious contacts.
3Object-generated harmful factors
If less solder material is used to prevent spurious contacts, then risk of shorts decreases, but electrical connections become incomplete or fragile, potentially resulting in system failure
Solution Approach 1:
The invention resolves this contradiction by implementing local quality through height variation. The first region with higher height provides sufficient solder volume for strong, complete electrical connections and mechanical strength. The second region with lower height simultaneously prevents excessive solder from causing spurious contacts. This localized differentiation allows the system to achieve both connection strength and defect prevention.
4Area of moving object
If space between solder contacts is reduced to accommodate smaller microelectronic components, then component miniaturization is achieved, but uniformity of solder plating deteriorates, increasing potential for defects
Solution Approach 1:
The patent addresses the challenge of miniaturization by applying local quality to the solder pad structure. Even as the overall size and spacing of solder contacts are reduced, the solder pad maintains internal height differentiation. The taller first region ensures adequate connection volume in the reduced space, while the shorter second region continues to prevent solder spread. This localized height variation allows the system to achieve miniaturization without sacrificing plating uniformity or increasing defect risk.
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 configuration enhances the precision and reliability of chip alignment, reducing the risk of electrical failures by self-limiting solder flow and maintaining alignment, even in constrained spaces, thereby improving the integrity of connections and reducing defects.
Implementation Method 1
allowing for controlled solder flow and alignment through surface tension forces during the melting process
Implementation Method 2
raising the temperature to a temperature above the melting temperature of the solder material
Data Source
AI summary
A technique relates to assembling a multi-chip system. A first chip stack element having two major surfaces and a first solder pad, a first vertical stop, a first lateral stop and a first waveguiding element is provided. A second chip stack element having two major surfaces and including a second solder pad, a flow resistor connected to the second solder pad, a second vertical stop, a second lateral stop, a reservoir pad connected to the flow resistor, and a second waveguiding element is provided. A solder material is plated to form a plated solder pad. A technique includes pre-aligning the first chip stack element and the second chip stack element, raising the temperature to a temperature above the melting temperature of the solder material, and flowing solder through the flow resistor. Aspects include aligning the first and second waveguiding elements and cooling the connected assembly to re-solidify the solder material.