Microwave Heat Spreader Grounding to Suppress Cavity Resonance
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Solution Overview
Problem
The power amplifier module in existing microwave devices lacks measures to prevent cavity resonance within the conductive shield, leading to unstable operations at certain frequencies.
Innovation Solution
A microwave device design incorporating a first multilayer resin substrate, a semiconductor substrate with ground through holes, a conductive heat spreader, and a conductive film connected to ground via holes, which stabilizes operations by reducing resonance frequencies and enhancing heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conductive shield is used to cover the power amplifier and surface acoustic wave duplexer, then heat dissipation is enhanced, but cavity resonance occurs inside the shield causing unstable operations
Solution Approach 1:
The conductive shield is segmented by providing multiple ground connection points (ground via holes in the substrate and ground contact portions on the shield surface) instead of a single continuous ground connection. This segmentation divides the shield into multiple smaller resonant cavities, raising the resonance frequency and eliminating cavity resonance issues while maintaining effective heat dissipation across the shield surface.
2Object-affected harmful factors
If the conductive shield is electrically connected to ground, then electromagnetic shielding is improved, but resonance frequency decreases causing unstable operations
Solution Approach 1:
The ground connection is segmented into multiple discrete points (multiple ground via holes and multiple ground contact portions) rather than a single large ground connection. This segmentation maintains effective electromagnetic shielding by providing multiple ground paths while dividing the shield surface into smaller sections, thereby raising the resonance frequency and preventing unstable operations.
Solution Approach 2:
The grounding approach transitions from a two-dimensional planar ground connection to a three-dimensional multi-point ground system extending through the substrate thickness. Ground via holes provide vertical ground paths through the substrate, creating a multi-dimensional ground network that maintains shielding effectiveness while controlling resonance characteristics.
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 design achieves stable microwave device operations by minimizing resonance frequencies and improving heat dissipation, ensuring efficient thermal management and electromagnetic shielding.
Implementation Method 1
a conductive heat spreader disposed at an opposite face of the semiconductor substrate from a face of the semiconductor substrate that faces the first multilayer resin substrate, the heat spreader being electrically connected to the semiconductor substrate
Implementation Method 2
the power amplifier module does not, however, have any measures against cavity resonance inside the conductive shield, which serves as a covering. Therefore, unstable operations may occur depending on the operating frequency
Data Source
AI summary
A microwave device can include: a first multilayer resin substrate including a ground via hole; a semiconductor substrate at the first multilayer resin substrate and including a high frequency circuit; a conductive heat spreader at an opposite face of the semiconductor substrate from a face of the semiconductor substrate facing the first multilayer resin substrate; a resin over the first multilayer resin substrate and covering the semiconductor substrate and the heat spreader such that an opposite face of the heat spreader from a face of the heat spreader facing the semiconductor substrate is exposed as an exposed face; and a conductive film covering the resin and the heat spreader and touching the exposed face. The semiconductor substrate can include a ground through hole extending through the semiconductor substrate. The conductive film can be electrically connected to the ground via hole via the heat spreader and the ground through hole.