IC Pad Structure With Hollow Conductive Layer for Wire Bonding
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Solution Overview
Problem
Conventional IC die pad structures, especially those with ultra-thick metal (UTM) layers, are prone to damage during wire bonding due to mechanical stress, which affects reliability and yield.
Innovation Solution
A pad structure featuring a first conductive layer with a hollow portion and a dielectric layer, where the second conductive layer is electrically connected to the first conductive layer through conductive portions, and a passivation layer with an opening to expose the bonding region, reducing mechanical stress and enhancing electromagnetic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an ultra-thick metal (UTM) layer is used in the pad structure, then electromagnetic performance is enhanced, but the pad structure becomes more susceptible to damage during wire bonding due to mechanical stress
Solution Approach 1:
The conductive layer is segmented into a solid peripheral portion and a hollow interior portion, creating a composite structure that combines the electromagnetic benefits of thick metal with the mechanical advantages of a hollow design, thereby resolving the contradiction between electromagnetic performance and damage resistance
Solution Approach 2:
The pad structure employs a composite conductive layer combining solid and hollow regions, leveraging the electrical conductivity of the solid peripheral portion while utilizing the stress-absorbing characteristics of the hollow interior to simultaneously achieve electromagnetic performance and mechanical reliability
2Power
If the conductive layer is made thicker to enhance electromagnetic performance, then power handling capability improves, but the mechanical stress during wire bonding increases causing more damage
Solution Approach 1:
The conductive layer is divided into a solid peripheral portion for electrical connectivity and a hollow interior portion for stress relief, enabling the structure to handle high power while maintaining mechanical strength during wire bonding operations
Solution Approach 2:
Different regions of the conductive layer are assigned different properties: the solid peripheral portion provides electrical conductivity and power handling, while the hollow interior portion provides mechanical flexibility and stress absorption, allowing simultaneous optimization of power and strength
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A pad structure is formed on an IC die and includes a first conductive layer, a dielectric layer, a second conductive layer and a passivation layer. The first conductive layer is formed on an upper surface of the IC die and having a hollow portion. The dielectric layer covers the first conductive layer. The second conductive layer is formed on the dielectric layer and electrically connected to the first conductive layer. The passivation layer covers the second conductive layer and has an opening exposing the second conductive layer for receiving a bonding wire.