Thermal Compression Bonding Through Parallel Alignment and Laser Soldering
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Solution Overview
Problem
The conventional thermal compression bonding process for fine-pitch flip-chip devices has a low throughput due to the sequential nature of precision alignment and thermal compression bonding, requiring precise alignment accuracy and controlled heating and cooling, which limits the process efficiency and throughput for volume production.
Innovation Solution
A thermal compression bonding method and apparatus that enables parallel processing of precision alignment and thermal compression bonding using a precision alignment station, a thermal compression bonding station, and a buffer station, where laser soldering forms a partial bond to secure the die in position, allowing for simultaneous processing of multiple units and reducing overall cycle time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sequential precision alignment and thermal compression bonding is used, then alignment accuracy is maintained, but throughput is reduced
Solution Approach 1:
The patent performs precision alignment in advance before thermal compression bonding, securing the die in position with temporary bonds or fixtures. This preliminary alignment action allows subsequent bonding operations to proceed without realignment, maintaining precision while enabling parallel processing of multiple dies to improve throughput.
Solution Approach 2:
The bonding process is divided into separate stages: alignment stage and bonding stage. Multiple dies can be aligned and secured in parallel during the alignment stage, then bonded in sequence or parallel during the bonding stage. This segmentation allows independent optimization of each stage and enables higher overall throughput.
2Productivity
If parallel processing of alignment and bonding is implemented, then throughput is increased, but process complexity is increased
Solution Approach 1:
The patent combines multiple functions into integrated tooling fixtures that can perform alignment, positioning, and bonding operations. The fixture system integrates alignment marks, positioning mechanisms, and bonding interfaces into a single unified tool, reducing the number of separate equipment pieces needed and simplifying process control while enabling parallel processing.
Solution Approach 2:
Temporary bonding agents or fixtures serve as intermediaries between the die and substrate during parallel processing. These intermediaries hold dies in aligned positions without requiring permanent bonds, allowing multiple dies to be processed simultaneously while maintaining alignment, then removed or integrated after bonding is complete.
3Reliability
If solder volume is reduced to prevent bridging, then bridging failure is reduced, but self-alignment capability is lost
Solution Approach 1:
The patent uses alignment marks or fiducial features copied from the die design onto the substrate or fixture. These copied reference features enable precise positioning without relying on solder self-alignment, allowing reduced solder volume for fine-pitch applications while maintaining positioning accuracy through the copied reference system.
Solution Approach 2:
The patent replaces the mechanical self-alignment mechanism of solder with a precision positioning system using alignment marks, fixtures, or vision systems. This substitution allows controlled positioning independent of solder flow, enabling reduced solder volume while maintaining alignment through the mechanical or optical positioning system.
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 significantly increases the throughput of the thermal compression bonding process by allowing parallel processing of alignment and bonding, potentially doubling the output compared to conventional methods, while maintaining precise alignment accuracy and efficient solder joint formation.
Implementation Method 1
providing heat to a portion of the die to elevate a temperature at the portion of the die to above a melting point of solder comprised in the electrical contacts so as to melt at least some of the solder
Implementation Method 2
heating the whole die to above the melting point of solder of the electrical contacts so that the solder of the electrical contacts outside the said portion of the die are also melted to bond the die to the substrate
Data Source
AI summary
A die is prepared for thermal compression bonding by first aligning electrical contacts on the die to bond pads on a substrate onto which the die is to be mounted. Those electrical contacts are held against the bond pads on the substrate with a bonding tool. Partially bonding the die onto the substrate by providing heat to a portion of the die to elevate a temperature there to above a melting point of solder in the electrical contacts so as to melt at least some of the solder. Then thermally compress the whole die and heat it to above the melting point of the solder of the electrical contacts so that the solder of the electrical contacts outside the portion of the die are also melted to bond the die to the substrate.