Conductive Bump Shielding for Low-Resistance EMI/RFI Grounding
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Solution Overview
Problem
The increasing concern of electromagnetic interference (EMI) and radio frequency interference (RFI) in semiconductor devices due to their smaller size and higher operating frequencies is not effectively addressed by existing shielding methods, as oxidation layers on copper pads increase contact resistance, reducing the effectiveness of EMI/RFI shielding.
Innovation Solution
The use of gold or other non-oxidizing conductive bumps formed on peripheral contact pads through ultrasonic welding, coupled with a conductive coating around the periphery of the semiconductor device, ensures low contact resistance and effective shielding against EMI/RFI by removing oxidation layers and providing a direct conductive path to ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper pads are used for EMI/RFI shielding, then cost and conductivity are improved, but oxidation layers form increasing contact resistance
Solution Approach 1:
The patent applies composite materials by combining copper pads with a protective non-oxidizing coating layer (such as gold, nickel, or palladium) to create a multi-layer structure. The copper provides excellent electrical conductivity for EMI/RFI shielding, while the outer coating layer prevents oxidation and maintains low contact resistance over time. This composite approach resolves the contradiction by integrating the benefits of both materials.
Solution Approach 2:
The patent employs a thin sacrificial protective coating layer applied over the copper pad. This outer layer is designed to be non-oxidizing and resistant to environmental degradation, serving as a permanent protective barrier rather than a disposable element. The coating prevents the copper from oxidizing, thereby maintaining low contact resistance throughout the device's operational life.
2Productivity
If device size is reduced for portability, then productivity and versatility are improved, but EMI/RFI interference increases
Solution Approach 1:
The patent applies local quality by implementing EMI/RFI shielding measures specifically at critical locations where interference is most problematic. Rather than shielding the entire device uniformly, the invention focuses on protecting specific pads, traces, and signal pathways that are most susceptible to electromagnetic interference. This localized approach maintains small device size while effectively addressing EMI/RFI concerns at critical points.
Solution Approach 2:
The patent employs parameter changes by modifying the electrical and physical characteristics of specific components to reduce EMI/RFI susceptibility. This includes adjusting trace geometry, impedance matching, and using materials with specific electromagnetic properties. By changing these parameters locally rather than redesigning the entire device, the patent maintains compact size while improving electromagnetic compatibility.
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 solution significantly enhances the shielding effectiveness against EMI/RFI by eliminating oxidation layers and maintaining low contact resistance, thereby improving the reliability of semiconductor devices in portable electronics.
Implementation Method 1
conductive bumps formed on the contact pads, for example using ultrasonic welding to remove an oxidation layer between the contact pads and the conductive bumps
Data Source
AI summary
A semiconductor device has shielding to prevent transmission and/or reception of EMI and/or RFI radiation. The semiconductor device comprises a substrate including grounded contact pads around a periphery of the substrate, exposed at one or more edges of the substrate. A bump made of gold or other non-oxidizing conductive material may be formed on the contact pads, for example using ultrasonic welding to remove an oxidation layer between the contact pads and the conductive bumps. The conductive bumps electrically couple to a conductive coating applied around the periphery of the semiconductor device.