Coreless Substrate Marchand Balun for Wideband RF Packaging
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Solution Overview
Problem
The design and implementation of Marchand baluns are complex, and they occupy valuable space on semiconductor dies, while relocating them to cored substrates faces inefficiencies and costly design challenges.
Innovation Solution
A semiconductor package with a Marchand balun integrated into a coreless substrate, using a first and second metal layer coupled via vias with insulation, forming a serpentine configuration to achieve efficient space usage and improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Marchand baluns are integrated into semiconductor dies, then performance is improved, but space occupancy increases and design complexity increases
Solution Approach 1:
The Marchand balun is extracted from the semiconductor die and relocated to a cored substrate, freeing up valuable die space while maintaining the balun's performance benefits. The substrate becomes the host for the balun structure, separating the RF function from the active device area.
Solution Approach 2:
The balun design transitions from a planar two-dimensional layout on the die to a three-dimensional multi-layer substrate structure. This allows the transmission lines to be routed through multiple layers via vias, achieving the required quarter-wavelength or half-wavelength path lengths without occupying excessive surface area on a single layer.
2Area of stationary object
If Marchand baluns are relocated to cored substrates, then space is saved, but manufacturing complexity and cost increase
Solution Approach 1:
The substrate is divided into multiple discrete layers (first substrate layer, second substrate layer, insulation layers) that can be manufactured and assembled separately. The metal layers are formed on different substrate layers and connected via vias, allowing each layer to be optimized independently and simplifying the overall manufacturing process.
Solution Approach 2:
Insulation layers are introduced as intermediary elements between the metal layers carrying different signals. These insulation layers provide electrical isolation and mechanical support, enabling the multi-layer structure to be manufactured using standard PCB techniques without requiring complex through-substrate via processes.
3Adaptability or versatility
If multi-layer metal structure is used in coreless substrate, then bandwidth is improved, but manufacturing steps increase
Solution Approach 1:
The multi-layer metal structure serves multiple functions simultaneously: the first and second metal layers form the balanced and unbalanced signal paths, the vias provide both electrical connection and mechanical alignment, and the insulation layers provide both electrical isolation and structural support. This multi-functionality achieves wide bandwidth performance without proportionally increasing manufacturing complexity.
Data Source
AI summary
In examples, a semiconductor package comprises a conductive terminal; a semiconductor die including a device side having circuitry formed therein, the device side facing toward the conductive terminal; and a substrate coupled to the conductive terminal and to the device side of the semiconductor die. The substrate includes a first metal layer coupled to first and second vias extending toward and coupled to either the device side of the semiconductor die or the conductive terminal. The substrate includes a second metal layer electrically isolated from the first metal layer by an insulation layer between the first and second metal layers, the second metal layer coupled to a third via extending toward and coupled to either the conductive terminal or the semiconductor die. The first and second metal layers form a Marchand balun.