Hydrogen Plasma Decapsulation for Silver Wire Integrity
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Solution Overview
Problem
Conventional decapsulation methods, such as acid etching and existing microwave-induced plasma (MIP) etching, cause significant damage to silver and copper bond wires due to the formation of silver oxide and silver fluoride, leading to undesired fracturing and corrosion, especially in electronic devices with silver wire bonding.
Innovation Solution
A hydrogen-containing plasma is used for decapsulation, which is induced by microwaves and directed at the plastic package to etch away the molding compound without damaging the electronic device components, utilizing a gas stream comprising hydrogen as the primary source, often with argon or helium as carrier gases, and optionally including a fluorine source for efficient etching of silica fillers, under atmospheric pressure to prevent ion-induced damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional acid etching or oxygen-based MIP etching is used to remove molding compound, then decapsulation speed is improved, but silver and copper bond wires are damaged due to formation of silver oxide and silver fluoride
Solution Approach 1:
The patent uses nitrogen-based plasma instead of oxygen-based plasma to create an inert atmosphere during etching. Nitrogen does not react with silver or copper to form damaging oxides or fluorides, while still enabling effective removal of the molding compound through plasma etching processes.
Solution Approach 2:
The patent changes the chemical composition parameter of the plasma from oxygen-based to nitrogen-based. This fundamental parameter change transforms the chemical reactivity of the plasma, preventing harmful reactions with metal bond wires while maintaining etching capability on the organic molding compound.
2Productivity
If CF4 is used as plasma etchant gas to etch silica fillers, then etching efficiency is improved, but silver fluoride is formed causing wire damage
Solution Approach 1:
The patent replaces oxygen-based plasma with nitrogen-based plasma, creating an inert environment that prevents silver fluoride formation. The nitrogen atmosphere does not promote fluoride formation on silver surfaces, eliminating the harmful effect while maintaining etching capability through alternative mechanisms.
Solution Approach 2:
The patent addresses the limitation of nitrogen plasma by combining it with ultrasonic cleaning. The plasma performs the chemical etching of organic material, while ultrasonic cleaning removes the silica fillers that would otherwise remain as residue, converting a potential disadvantage into a beneficial two-step process.
3Reliability
If hydrogen-containing plasma is used for decapsulation, then bond wire damage is reduced, but etching speed decreases compared to oxygen-based MIP
Solution Approach 1:
The patent implements a combined process where nitrogen plasma etching is followed by ultrasonic cleaning in sequence. This continuous action ensures complete removal of both organic molding compound and inorganic silica fillers, compensating for the slower etching speed of nitrogen plasma compared to oxygen plasma.
Solution Approach 2:
The patent introduces ultrasonic cleaning as an intermediary step between plasma treatment and final inspection. This intermediate process removes residual silica particles that the plasma alone cannot efficiently eliminate, achieving complete decapsulation without compromising wire integrity.
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 hydrogen-containing plasma method effectively decapsulates electronic devices with minimal damage to silver, copper, and other metal bond wires, achieving a smoother and less damaged surface compared to conventional acid decapsulation and oxygen-based MIP etching, while allowing for efficient etching of thicker plastic packages within a reasonable time frame.
Implementation Method 1
microwave-inducing a hydrogen-containing plasma stream from said gas with microwaves
Implementation Method 2
directing the hydrogen-containing plasma stream to the plastic package to etch the plastic package
Data Source
AI summary
The invention is directed to a method for treating an electronic device that is encapsulated in a plastic package, said method comprising the steps of providing a gas stream comprising a hydrogen source; inducing a hydrogen-containing plasma stream from said gas; and directing the hydrogen-containing plasma stream to the plastic package to etch the plastic package.