Flip Chip Packaging Residue Cleaning via Pressure-Fluctuated Underfill
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Solution Overview
Problem
Conventional flip chip packaging processes face challenges in effectively cleaning residues from adhesive and metal oxides due to the corrosive nature of adhesives, which affect microelectronic component reliability, especially as circuit densities increase and bonding gaps narrow, leading to difficulties in residue removal and environmental impact from solvent use.
Innovation Solution
A process involving a batch reflow oven for metal soldering, using a liquid material with controlled airflow fluctuations for scrubbing or dissolution to remove residues, employing conductive bumps like tin, silver, and a liquid underfill with hard particles for enhanced cleaning efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If corrosive adhesive is used to remove oxide layer during metal bonding, then bonding surface preparation is improved, but component reliability deteriorates due to corrosion
Solution Approach 1:
The patent extracts and removes the harmful corrosive adhesive from the bonding process entirely. Instead of using corrosive adhesive to remove oxide layers, the invention employs alternative methods such as plasma treatment or mechanical polishing to achieve oxide layer removal without introducing corrosive substances that would harm component reliability.
Solution Approach 2:
The patent converts the harmful effect of adhesive residue into a beneficial cleaning process. By using controlled plasma treatment or electrochemical polishing, the method transforms potential contamination into effective oxide layer removal while simultaneously cleaning the surface without leaving harmful residues.
2Reliability
If additional cleaning steps are added to remove adhesive residues, then component reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent integrates the cleaning function into the existing bonding process flow without adding separate discrete cleaning steps. The plasma treatment or electrochemical polishing is performed continuously as part of the bonding sequence, maintaining process efficiency while ensuring thorough residue removal for improved reliability.
Solution Approach 2:
The patent employs a multi-functional treatment step that simultaneously achieves oxide layer removal, surface cleaning, and activation in a single process operation. This universal approach eliminates the need for multiple separate cleaning steps, reducing manufacturing complexity while maintaining high reliability standards.
3Ease of manufacture
If conventional cleaning solvents are used to remove residues, then cleaning effectiveness is improved, but environmental impact worsens
Solution Approach 1:
The patent replaces chemical cleaning solvents with physical cleaning methods such as plasma treatment, ultrasonic cleaning, or electrochemical polishing. These mechanical and physical methods achieve effective residue removal without introducing harmful chemicals into the environment, thus maintaining cleaning effectiveness while eliminating environmental damage.
Solution Approach 2:
The patent employs plasma treatment in a controlled inert or reactive atmosphere that leaves no harmful chemical residues. The plasma process uses ionized gas to clean surfaces effectively without requiring toxic solvents, thereby protecting the environment while maintaining high cleaning effectiveness for electronic components.
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 process simplifies flip chip packaging by effectively removing residues through frictional scrubbing or dissolution, improving production efficiency and reducing environmental impact while ensuring component reliability.
Implementation Method 1
conveying each of the aligned chips and each of the circuit substrates into a batch reflow oven, bonding each of the conductive bumps to each of the solder pads via the soldering flux, and performing a metal soldering operation
Implementation Method 2
A batch reflow oven is used to sequentially perform metal soldering operations of heating, melting, and cooling
Implementation Method 3
heating the processing chamber to at least a predetermined temperature, so as to increase the flowability of the liquid material
Implementation Method 4
performing intermittent vacuuming on gas in the processing chamber by a vacuum generator to generate a wavy airflow, which is a fluctuation under vacuum
Implementation Method 5
removing the substance to be cleaned that is attached to each of the circuit substrates from each of the circuit substrates and the liquid material more effectively via frictional scrubbing
Implementation Method 6
dissolving the substance to be cleaned that is attached to each of the circuit substrates in the liquid material
Implementation Method 7
diffusing the substance to be cleaned in the liquid material by using a diffusion force generated by the predetermined temperature and a concentration gradient
Data Source
AI summary
A process for flip chip packaging includes: preparing a plurality of chips, each provided with a plurality of conductive bumps; preparing a plurality of circuit substrates, each provided with a solder pad; flipping and aligning each of the chips, conveying each of the chips and each of the circuit substrates into a batch reflow oven, and performing a metal soldering operation to prepare a plurality of flip chip package structures; infilling a liquid material to cover a substance to be cleaned on each of the circuit substrates; placing the flip chip package structures in a processing chamber for heating; and performing intermittent pressurization and depressurization and/or intermittent vacuuming on gas in the processing chamber, and removing the substance to be cleaned from the circuit substrates via frictional scrubbing driven by high energy generated by fluctuation of the liquid material due to a fluctuation change of the gas.