Collet Force Alignment for Flip Chip Reflow Warpage
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Solution Overview
Problem
Semiconductor devices face challenges in achieving reliable and high-density interconnects due to warpage issues during manufacturing, which can lead to misalignment and poor joint reliability, especially in flip-chip applications with high input/output counts or fine interconnect pitches.
Innovation Solution
A method involving the use of conductive columns and bumps, where a collet with a cavity is applied to hold the bumps to the conductive columns while reflowing them to form electrical connections, reducing misalignment and improving joint reliability, and involving the use of a collet to apply force and align the semiconductor die with the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If thinner semiconductor die or substrates are used to produce thinner semiconductor devices, then the device thickness is reduced, but warpage susceptibility increases leading to misalignment of interconnect structures
Solution Approach 1:
The collet is positioned over the semiconductor die before the reflow process begins, establishing proper alignment and applying preliminary force to counteract warpage effects before they occur during heating. This preventive approach ensures that even thin substrates maintain correct interconnect alignment throughout the subsequent reflow process.
Solution Approach 2:
The system applies controlled mechanical force through the collet to counteract thermal warpage effects. By dynamically adjusting the supporting force parameter during the reflow process, the method compensates for warpage-induced misalignment in thin substrates, maintaining precise interconnect alignment despite reduced substrate thickness.
2Productivity
If reduced volume of solder is used in flip-chip applications, then cost is reduced and interconnect density is increased, but misalignment tolerance decreases and joint reliability deteriorates
Solution Approach 1:
The collet establishes precise alignment between bumps and conductive columns before the reflow process begins. By pre-positioning components correctly and applying initial force, the system ensures that even with reduced solder volume and tighter tolerances, the interconnects form reliable joints without misalignment issues.
Solution Approach 2:
The method applies controlled mechanical force through the collet to maintain precise alignment during reflow. This force parameter control compensates for the reduced misalignment tolerance inherent in high-density interconnect structures with minimal solder volume, ensuring reliable joint formation despite increased density requirements.
3Ease of manufacture
If conductive columns with reduced solder volume are used, then interconnect cost is reduced and density is increased, but misalignment tolerance during manufacture decreases
Solution Approach 1:
The collet is positioned and force is applied before reflow to establish and maintain precise alignment. This preliminary positioning action ensures that the reduced alignment tolerance of high-density conductive column structures is compensated for, enabling cost-effective manufacturing without sacrificing precision.
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 enables reliable, high-density interconnects with reduced misalignment and improved joint reliability, even in thin semiconductor devices and substrates susceptible to warpage, by ensuring proper alignment and metallurgical connections between conductive columns and bumps.
Implementation Method 1
applying a force to the collet to hold the bumps to the conductive columns while reflowing the bumps
Implementation Method 2
reflowing the bumps to make electrical connection to the conductive columns
Data Source
AI summary
A semiconductor device comprises a substrate and a semiconductor die. Bumps are formed over the substrate or a first surface of the semiconductor die. Conductive columns devoid of solder are formed over the substrate or the first surface of the semiconductor die. The semiconductor die is disposed over the substrate. A collet including a first cavity and a second cavity formed in a surface of the first cavity is mounted over the semiconductor die with a second surface of the semiconductor die opposite the first surface disposed within the first cavity. The bumps are reflowed. A force is applied to the collet to hold the bumps to the conductive columns while reflowing the bumps to make electrical connection to the conductive columns. The collet is removed. An underfill material is deposited between the semiconductor die and substrate. An encapsulant is deposited over the semiconductor die and substrate.