Ceramic Package Seal Ring Layout for RF EMI Shielding
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Solution Overview
Problem
Ceramic semiconductor packages face electromagnetic interference due to the exposure of high-frequency signal traces to seal rings and ground shields, leading to degraded performance in applications like radio frequency amplifiers and synthesizers.
Innovation Solution
The package design includes a ceramic substrate with a ground shield positioned between the semiconductor die and the first metal layer, featuring a seal ring vertically aligned with the ground shield but not with the orifice or empty space, mitigating electromagnetic coupling by maintaining a minimum horizontal and vertical distance between the signal traces and the seal ring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the seal ring is positioned close to the signal traces for compact packaging, then the package size is reduced, but electromagnetic interference increases causing degraded performance
Solution Approach 1:
A ground shield is introduced as an intermediary component between the signal traces and the seal ring. The ground shield acts as a barrier that blocks electromagnetic fields, preventing interference from the seal ring from coupling into the high-frequency signal traces while allowing the seal ring to remain in its necessary position for hermetic sealing.
Solution Approach 2:
The ground shield is strategically positioned only in the regions where electromagnetic interference would occur, specifically between the seal ring and the signal traces. This localized shielding approach provides targeted protection against electromagnetic interference without requiring the entire package structure to be modified, thus maintaining compact dimensions.
2Object-affected harmful factors
If the ground shield completely covers the signal traces for maximum shielding, then electromagnetic interference is reduced, but signal transmission is blocked
Solution Approach 1:
The ground shield is segmented with strategic openings or gaps that allow high-frequency signals to pass through while still providing electromagnetic shielding. The segmented structure is designed to block interfering fields from the seal ring while maintaining signal transmission paths, thus resolving the contradiction between shielding effectiveness and signal integrity.
3Ease of manufacture
If the seal ring is vertically aligned with the orifice for structural simplicity, then manufacturing is easier, but electromagnetic coupling increases
Solution Approach 1:
The ground shield is designed with an asymmetric pattern of openings and solid sections that are specifically configured to break the vertical alignment between the seal ring and the signal traces. This asymmetric design creates electromagnetic isolation zones that prevent coupling while maintaining manufacturability through standard fabrication processes.
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 design significantly reduces insertion losses and improves return losses across the 2 GHz to 38 GHz frequency range, particularly in the 20 GHz to 28 GHz range, enhancing the functional integrity and performance of the semiconductor package.
Implementation Method 1
a ground shield positioned between the semiconductor die and the first metal layer, the ground shield including an orifice above a portion of the first metal layer
Data Source
AI summary
In examples, a semiconductor package comprises a ceramic substrate and first and second metal layers covered by the ceramic substrate. The first metal layer is configured to carry signals at least in a 20 GHz to 28 GHz frequency range. The package comprises a semiconductor die positioned above the first and second metal layers and coupled to the first metal layer. The package comprises a ground shield positioned in a horizontal plane between the semiconductor die and the first metal layer, the ground shield including an orifice above a portion of the first metal layer. The package includes a metal seal ring coupled to a top surface of the ceramic substrate, the metal seal ring having a segment that is vertically aligned with a segment of the ground shield. The segment of the ground shield is between the orifice of the ground shield and a horizontal center of the ground shield. The package comprises a metal lid coupled to a top surface of the metal seal ring.