Integrated Circuit Stand-off Height Solder Joints
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Solution Overview
Problem
The existing methods for manufacturing integrated circuit assemblies often result in reduced stand-off height due to solder bump collapse during reflow, leading to increased stress on dielectric layers, difficulty in forming void-free underfills, and reduced reliability of IC assemblies.
Innovation Solution
Applying a lifting force during the soldering process to increase the stand-off height by elongating the solder connections between the IC die and substrate, either from below or above, while the solder is in a liquescent state, and ensuring proper alignment and encapsulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If solder bumps are made small to reduce footprint and increase density, then area utilization improves, but stand-off height is reduced
Solution Approach 1:
The patent applies parameter changes by modifying the solder bump geometry from spherical to cylindrical shape with increased height-to-diameter ratio. This changes the physical parameters of the solder joint, allowing taller stand-off height while maintaining small footprint area. The cylindrical shape with height greater than diameter provides both compact area utilization and increased vertical clearance.
Solution Approach 2:
The patent transitions from two-dimensional area optimization to three-dimensional volume optimization. Instead of only reducing footprint area, the solution exploits the vertical dimension by creating tall, narrow solder bumps. This dimensional shift allows simultaneous achievement of small footprint and large stand-off height by distributing the volume differently in space.
2Area of stationary object
If stand-off height is reduced to accommodate small solder bumps, then area density improves, but stress resistance deteriorates
Solution Approach 1:
The patent changes the geometric parameters of solder bumps to cylindrical shapes with height-to-diameter ratios greater than 1:1. This parameter modification increases the vertical dimension while maintaining or reducing the horizontal footprint, thereby simultaneously improving area density and stress resistance through the taller, more robust solder joint structure.
Solution Approach 2:
The patent employs composite material structures by combining different solder alloy compositions or integrating reinforcement structures within the solder joints. This composite approach enhances the mechanical strength and stress resistance of the solder connections while maintaining the compact cylindrical geometry that provides both high area density and increased stand-off height.
3Volume of stationary object
If stand-off height is reduced for compact assemblies, then packaging size improves, but underfill quality deteriorates
Solution Approach 1:
The patent exploits the vertical dimension by creating tall solder bumps with increased stand-off height, which provides adequate clearance for underfill material application. This three-dimensional approach allows the underfill to be properly dispensed and cured without being compressed, ensuring void-free quality while maintaining compact overall packaging volume through efficient vertical space utilization.
Solution Approach 2:
The patent applies preliminary action by establishing the correct stand-off height through precisely controlled cylindrical solder bump formation before the underfill process. This pre-established vertical clearance ensures that subsequent underfill application can proceed without interference, allowing proper material flow and void-free encapsulation to occur naturally during the underfill process.
4Productivity
If solder bumps are made small and close together, then component density improves, but solder connection reliability deteriorates
Solution Approach 1:
The patent changes the solder bump shape parameter from spherical to cylindrical with height-to-diameter ratios exceeding 1:1. This geometric transformation allows smaller diameter bumps to be placed closer together (improving component density) while the increased height provides greater structural integrity and reliability to each individual solder connection, counteracting the potential weakness from reduced size.
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 enhances the stand-off height, improving the resistance to stress, solder interconnect properties, and underfill quality, thereby increasing the reliability of the IC assemblies.
Implementation Method 1
Solder is interposed between the corresponding bond pads and heated
Implementation Method 2
heated to a liquescent state
Data Source
AI summary
Disclosed are integrated circuit assemblies with increased stand-off height and methods and systems for their manufacture. Methods of the invention provide for assembling a semiconductor device by aligning a die with a substrate and interposing solder between corresponding substrate and die bond pads. A lifting force is applied to the die during heating of the solder to a liquescent state, thereby increasing the stand-off height of the die above the substrate. The lifting force is maintained during cooling of the solder to a solid state, thereby forming increased stand-off height solder connections.