Thermocompression Bond Tip With Low Surface Energy Coating
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Solution Overview
Problem
Conventional bond tips in thermocompression bonding are prone to contamination and damage from non-conductive film (NCF) underfill material, which can lead to poor solder joints and die cracking, especially when dealing with small semiconductor dice and tight pitches, due to the inability to maintain uniform temperature and apply compressive force effectively.
Innovation Solution
The use of a bond tip with a low surface energy (LSE) material coating on its bottom surface, such as parylene, PTFE, or DLC, which prevents adhesion and wetting by the NCF underfill, allowing for a larger bond tip size and preventing contamination, while maintaining heat application and pressure for effective bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bond tip is used in thermocompression bonding, then the bonding process can be performed, but the bond tip becomes contaminated and damaged by NCF underfill material
Solution Approach 1:
A release film is introduced as an intermediary layer between the NCF underfill material and the bond tip. This release film prevents direct contact and adhesion between the underfill and bond tip surfaces, eliminating contamination and damage while allowing the bonding process to proceed normally
Solution Approach 2:
The invention changes the surface energy parameters of the bond tip by applying a release film with controlled surface properties. This parameter change reduces surface adhesion between the NCF underfill and bond tip, preventing the underfill from adhering to and damaging the bond tip during thermocompression bonding
2Manufacturing precision
If a larger bond tip is used to maintain uniform temperature and apply compressive force, then bonding quality improves, but the bond tip contacts more NCF underfill material increasing contamination risk
Solution Approach 1:
The release film serves as a protective intermediary that allows the bond tip to maintain larger contact area for uniform temperature and force application, while simultaneously preventing NCF underfill from adhering to the bond tip surface, thus resolving the contradiction between bonding quality and contamination risk
3Measurement precision
If the bond tip size is reduced to match small semiconductor dice, then alignment precision improves, but the bond tip cannot maintain uniform temperature and apply effective compressive force
Solution Approach 1:
The release film enables the use of larger bond tips for small semiconductor dice by preventing underfill adhesion. This allows the bond tip to maintain sufficient size for uniform temperature distribution and effective compressive force application, while still achieving precise alignment through the larger contact area
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 LSE material coating enables the use of larger bond tips that can handle various dice sizes, reduces contamination risk, and prevents die cracking, ensuring uniform bonding and higher yield by preventing NCF underfill from adhering to the bond tip, thus maintaining the integrity of both the bond and the semiconductor die.
Implementation Method 1
a low surface energy (LSE) material covering at least a portion of the bottom surface
Implementation Method 2
Thermocompression bonding, hereinafter also referred to merely as 'bonding' for simplicity, has been employed in semiconductor packaging technology
Implementation Method 3
applying force to the semiconductor die with the bond tip during application of heat to press the pillars against the aligned conductive elements
Data Source
AI summary
A bond tip for thermocompression bonding a bottom surface includes a die contact area and a low surface energy material covering at least a portion of the bottom surface. The low surface energy material may cover substantially all of the bottom surface, or only a peripheral portion surrounding the die contact area. The die contact area may be recessed with respect to the peripheral portion a depth at least as great as a thickness of a semiconductor die to be received in the recessed die contact area. A method of thermocompression bonding is also disclosed.