Sacrificial Anode Protects Copper Wire Bond from Corrosion
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Solution Overview
Problem
Copper wire bond corrosion occurs due to corrosive species migration from surrounding materials, leading to open failures during temperature/humidity reliability testing, as existing technologies fail to effectively protect the intermetallic compound (IMC) from corrosion.
Innovation Solution
A sacrificial anode with a higher redox potential than the wire bond materials is formed to attract and corrode corrosive species instead of the IMC, thereby protecting the wire bond from corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper wire bond technology is used, then electrical connectivity is achieved, but corrosive species from surrounding materials migrate to the intermetallic compound causing corrosion and open failures
Solution Approach 1:
A sacrificial anode layer is introduced as an intermediary between the corrosive species and the wire bond IMC. This sacrificial layer preferentially reacts with corrosive species (such as sulfur from encapsulant materials), preventing them from reaching and corroding the wire bond IMC, thereby resolving the contradiction between maintaining wire bond reliability and preventing corrosive species migration
Solution Approach 2:
The invention converts the harmful effect of corrosive species migration into a beneficial protective mechanism. By designing a sacrificial anode that deliberately attracts and reacts with corrosive species, the harmful migration process is redirected to protect the wire bond IMC, transforming the corrosion threat into a protective sacrificial reaction
2Reliability
If sacrificial anode is formed to protect wire bond, then corrosion protection is improved, but device structure complexity increases
Solution Approach 1:
The sacrificial anode layer is merged with the encapsulant formation process. The same encapsulant material that provides environmental protection also serves as the source of sacrificial protection by containing materials that react with corrosive species, thereby providing corrosion protection without significantly increasing structural complexity
Solution Approach 2:
The encapsulant material serves multiple functions: it provides environmental sealing and simultaneously acts as a source of sacrificial protection through controlled chemical reactions with corrosive species. This multi-functionality reduces the need for separate protective structures, maintaining device simplicity while achieving corrosion protection
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 sacrificial anode effectively diverts corrosive species away from the IMC, enhancing the reliability and durability of the wire bond by preferentially corroding itself, thus preventing open failures.
Implementation Method 1
a sacrificial anode with a higher redox potential than the wire bond materials is formed to attract and corrode corrosive species instead of the IMC
Data Source
AI summary
A packaged semiconductor device is made by forming a conductive pad on an external surface of an integrated circuit device, forming a passivation layer over the conductive pad, removing a portion of the passivation layer over a bond area on the conductive pad, forming a sacrificial anode around a majority of a periphery surrounding the bond area, forming a conductive bond in the bond area, and forming an encapsulating material around the conductive bond and an exposed portion of the sacrificial anode.