Fluxless Die Bonding With In-Situ Plasma for Clean Solder Joints
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Solution Overview
Problem
The use of flux in bonding semiconductor dies to packaging substrates can lead to structural damage, contamination, corrosion, and reliability issues due to impurities, residue, and improper cleaning, resulting in poor electrical performance and device failure.
Innovation Solution
Atmospheric Pressure Plasma Jet (APPJ) treatment is used to clean and modify the surface chemistry of bonding structures before thermocompression bonding, eliminating the need for flux by simultaneously performing plasma treatment and bonding processes in a low-oxygen environment, ensuring a clean and reliable bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flux is used during bonding, then bonding process can proceed, but impurities contaminate bonding surfaces leading to poor electrical performance
Solution Approach 1:
The patent removes flux entirely from the bonding process and replaces it with plasma treatment. The bonding is performed in a vacuum environment without any flux material, extracting the harmful contaminating agent while maintaining bonding capability through alternative plasma-based surface preparation and protection methods.
Solution Approach 2:
The patent uses a vacuum environment as an inert atmosphere during bonding. The chamber is evacuated to create a fluxless, contamination-free environment. Plasma treatment is applied in this vacuum environment to prepare surfaces and protect them from oxidation without introducing flux impurities.
2Reliability
If flux is used during bonding, then bonding can be achieved, but flux residue remains causing corrosion and reliability issues
Solution Approach 1:
The patent eliminates flux residue corrosion by completely removing flux from the process. Instead of dealing with residue cleanup, the vacuum-based fluxless bonding approach prevents residue formation at the source, and plasma treatment ensures clean, activation-ready surfaces without organic flux contaminants.
Solution Approach 2:
The patent replaces the chemical flux-based bonding system with a physical plasma-based system. Plasma treatment provides surface activation and protection without leaving chemical residues, substituting a cleaner physical process for the contaminating chemical flux approach.
3Reliability
If heat and pressure are applied during bonding, then bonding is achieved, but semiconductor die or package substrate warps causing structural damage
Solution Approach 1:
The patent optimizes bonding parameters by using plasma treatment to enable bonding at reduced temperatures and pressures compared to conventional flux-based processes. The plasma activation allows for lower energy bonding conditions that minimize thermal stress and prevent warping while maintaining bond strength.
4Productivity
If flux is used during bonding, then bonding process can complete, but improper use causes poor soldering leading to device failure
Solution Approach 1:
The patent applies plasma treatment as a preliminary action before bonding to prepare surfaces for optimal soldering. The plasma activation cleans and activates surfaces in advance, ensuring proper wetting and adhesion without the need for flux, thereby preventing soldering defects before they occur.
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 method enhances the cleanliness and reactivity of bonding surfaces, reduces structural damage, and improves the reliability of the bond, leading to improved electrical performance and extended device lifespan by eliminating flux-related issues.
Implementation Method 1
Atmospheric Pressure Plasma Jet (APPJ) treatment is used to clean and modify the surface chemistry of bonding structures
Implementation Method 2
bonding processes in a low-oxygen environment
Data Source
AI summary
A bonded assembly may be formed by providing at least a first packaging substrate in a low-oxygen ambient; providing at least a first semiconductor package in the low-oxygen ambient; performing a first plasma package-treatment process on the first semiconductor package in the low-oxygen ambient by directing at least one first plasma jet to first solder material portions bonded to the first semiconductor package; and bringing the first solder material portions onto, or in proximity to, first substrate-side bonding structures located on the first packaging substrate while the at least one first plasma jet is directed to the first solder material portions. The first substrate-side bonding structures are treated with the first plasma jet. The first semiconductor package is bonded to the first packaging substrate while, or after, the first substrate-side bonding structures are treated with the first plasma jet.