Surface Mount Circulator Using Edge Wrap Metallization
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Solution Overview
Problem
The existing methods for mounting circulators on printed circuit boards are complex, costly, and not compatible with surface mounting techniques like ball grid array (BGA) due to the geometry of circulators, which includes microstrip transmission lines on one side and a ground plane on the other, and the presence of additional components like magnets and pole pieces.
Innovation Solution
A novel circulator design that uses edge wrap metallization to connect microstrip lines from the top to the bottom of the substrate, allowing for surface mount compatibility by using a ball grid array to connect signal and ground contacts to a circuit board, with a smaller pole piece that does not cover the signal pads, enabling a simple solder flow process for mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional mounting methods (conductive epoxy with wire bonding or rigid metal tabs) are used, then circulators can be mounted on circuit boards, but the process is complex, costly, and inconsistent with standard solder re-flow attach
Solution Approach 1:
The patent transitions from conventional two-dimensional wire bonding or tab mounting to a three-dimensional ball grid array configuration, allowing multiple electrical contacts to be arranged in a grid pattern on the bottom surface of the circulator package. This enables simultaneous solder re-flow attachment of multiple contacts to the circuit board, simplifying the manufacturing process while reducing packaging complexity
Solution Approach 2:
The circulator package is designed with a standardized BGA configuration that can be mounted using the same solder re-flow process as other integrated circuits. This universal mounting approach eliminates the need for specialized mounting procedures, making the circulator compatible with standard PCB fabrication and assembly processes
2Ease of manufacture
If ball grid array mounting is used, then mounting becomes simpler and cheaper, but conventional circulator geometry (microstrip lines on one side, ground plane on the other with magnets and pole pieces) prevents BGA compatibility
Solution Approach 1:
The patent reconfigures the circulator's electrical contacts to be located on the bottom surface in a grid pattern, rather than having signal lines and ground on opposite sides of the substrate. This dimensional reorganization allows the circulator to interface with the circuit board through solder balls in a BGA configuration, achieving both simplified manufacturing and BGA compatibility
Solution Approach 2:
Instead of having the ground plane on the bottom and signal lines on the top (conventional configuration), the patent inverts the arrangement by bringing both signal and ground contacts to the bottom surface. This inversion enables the circulator to be mounted using standard BGA techniques while maintaining proper signal flow through the magnetized ferrite substrate
3Reliability
If conventional circulator packaging is used, then the circulator functions properly with microstrip lines and magnetic field, but the additional components (magnet and pole piece) make packaging and mounting more difficult
Solution Approach 1:
The patent integrates the magnet and pole piece components within the circulator package in a compact arrangement that allows the entire assembly to be mounted as a single unit using BGA technology. The magnetic components are positioned to provide the necessary magnetic field for circulator operation while maintaining a low profile that is compatible with surface mount packaging
Solution Approach 2:
The circulator uses a thin ferrite substrate that allows the magnetic field to pass through while maintaining a compact package profile. This thin-film approach enables the circulator to be mounted in a low-profile BGA configuration without requiring excessive vertical space for the magnet and pole piece components
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 allows for a less complex, less expensive, and more robust mounting of circulators using surface mount techniques, enabling multiple components to be attached in a single step, reducing fabrication costs and simplifying the packaging process.
Implementation Method 1
a magnet on top of the substrate over a resonator circuit part of the microstrip lines and a pole piece on the bottom of the substrate beneath the ground for providing a magnetic field in the substrate between the microstrip lines and the ground such that signals are coupled between the microstrip lines in a particular direction
Implementation Method 2
The chip is placed onto a circuit board having copper pads in a pattern that matches the array of solder balls, and then heated until the solder balls melt, thereby attaching the chip to the board
Data Source
AI summary
A surface mount circulator. The novel circulator includes a substrate, a predetermined number of microstrip lines disposed on a first surface of the substrate, a ground layer and a predetermined number of electrical contacts disposed on the second surface of the substrate, and a mechanism for coupling each microstrip line to one of the electrical contacts. In an illustrative embodiment, the circulator uses edge wrap metallization to wrap a microstrip line down a side of the substrate to connect with a corresponding contact. A ball grid array can then be used to connect the signal contacts and ground at the second surface of the substrate with a circuit board. The circulator also includes a magnet on first surface of the substrate over a resonator circuit connecting the microstrip lines and a pole piece on the second surface of the substrate beneath the ground to provide magnetic bias to the substrate.