Segmented Stack Tool Dumbbell for Reflow Cooling
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Solution Overview
Problem
The reflow process for semiconductor packages faces challenges in ensuring reliable bonding and efficient cooling, leading to potential separation or deformation of the package substrate and increased process time, which affects the reliability and efficiency of the semiconductor package.
Innovation Solution
A stack tool for reflow comprising a lower jig, an intermediate jig, and an upper dumbbell with a recessed design that allows for rapid cooling and improved heat dissipation, enabling precise contact and efficient heat transfer during the reflow process, thereby reducing the risk of substrate separation and deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the dumbbell is separated from the package substrate before sufficient cooling, then the reflow process time is reduced, but the package substrate and semiconductor chip may become partially separated or deformed, degrading reliability
Solution Approach 1:
The dumbbell is divided into multiple segments (first dumbbell, second dumbbell, third dumbbell) that can be separated at different times. The first dumbbell is removed after reflow while the package substrate is still hot, the second dumbbell is removed after partial cooling, and the third dumbbell is removed after complete cooling. This segmentation allows optimization of both process time and reliability by enabling early removal of pressurization elements while maintaining structural support during critical cooling phases.
2Reliability
If the dumbbell is kept on the package substrate for sufficient cooling, then the semiconductor package reliability is maintained, but the reflow process time increases and subsequent processes are delayed
Solution Approach 1:
The dumbbell pressurization system is segmented into multiple removable components that can be taken off at different stages of the cooling process. This allows the package substrate to maintain structural support during critical cooling phases (preserving reliability) while enabling earlier removal of some pressurization elements to reduce total process time and improve production efficiency.
3Device complexity
If a conventional dumbbell design is used, then the structure is simple, but rapid cooling is hindered and heat dissipation is inefficient
Solution Approach 1:
The dumbbell structure incorporates localized heat dissipation features including protrusions that contact the package substrate at specific points, recesses that facilitate air circulation, and varying thickness regions. These local structural modifications enhance heat transfer efficiency and cooling rate without requiring a complete redesign of the entire stack tool structure, thus maintaining relative simplicity while improving thermal management.
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
The solution enhances the reliability of semiconductor packages by ensuring rapid cooling of the stack tool, allowing for timely separation of the upper dumbbell without damaging the substrate, thus reducing process time and improving production efficiency.
Implementation Method 1
an upper recess stepped downward from an upper surface of the dumbbell main body on only a region corresponding to an upper surface of the semiconductor package, and a protruding support configured to protrude downward from a lower surface of the upper recess and configured to be brought into contact with an upper surface of the semiconductor package
Implementation Method 2
The reflow process is a process in which heat is applied to the semiconductor package, with a pad of the semiconductor chip being in contact with the solder bump of the package substrate. Thus the solder bump is melted and bonded to the pad.
Data Source
AI summary
A stack tool comprises a lower jig having a plurality of package seating regions configured to seat a semiconductor package, an intermediate jig configured to be seated on top of the lower jig, and having a package support hole into which the semiconductor package is configured to be inserted, the intermediate jig having a shape corresponding to the plurality of package seating regions, and an upper dumbbell. The upper dumbbell includes a dumbbell main body on top of the intermediate jig, an upper recess stepped downward from an upper surface of the dumbbell main body on only a region corresponding to an upper surface of the semiconductor package, and a protruding support configured to protrude downward from a lower surface of the upper recess and configured to be brought into contact with an upper surface of the semiconductor package.