MRAM Magnetic Shielding Package Structure
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Solution Overview
Problem
Existing MRAM package designs fail to provide comprehensive magnetic shielding on all six sides, leading to exposure to stray electromagnetic fields and increased package thickness due to inefficiencies in wire-bonding and flip-chip shielding methods.
Innovation Solution
A method involving the formation of a first metal layer with laterally separated metal-filled vias between PCB substrate portions, attaching a semiconductor die, and forming a second metal layer over the die on all opposing sides, using a nickel-iron alloy to ensure comprehensive magnetic shielding without thickening the package.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If wire-bonding shielding approach is used, then magnetic shielding is provided, but package thickness increases and shielding efficiency decreases
Solution Approach 1:
The patent transitions from planar shielding layers to a three-dimensional enclosed cage structure formed by side walls extending vertically from the bottom shield. This dimensional change allows the shielding to enclose the MRAM structure on all six sides (top, bottom, and four lateral sides) without requiring excessive thickness in any single dimension, achieving comprehensive shielding while maintaining a compact profile.
Solution Approach 2:
The side walls are formed by removing substrate material down to the bottom shield layer, creating nested structures where the bottom shield, side walls, and top shield form an integrated enclosed volume. This nesting approach allows multiple shielding functions to be combined in a space-efficient manner, providing complete enclosure without adding excessive package thickness.
2Object-affected harmful factors
If wire-bonding shielding is used, then some protection is provided, but shielding on all six sides is not achieved
Solution Approach 1:
The shielding structure is segmented into distinct functional components: a bottom shield layer, four side walls extending upward, and a top shield layer. This segmentation allows each component to be optimized for its specific shielding function while collectively providing complete six-sided protection. The side walls are further segmented into portions removed from the substrate to create the enclosed structure.
Solution Approach 2:
The patent applies different shielding configurations to different locations: the bottom shield provides base protection, the side walls provide lateral protection by removing substrate material down to the bottom shield, and the top shield provides upper protection. This localized approach ensures that each region of the MRAM structure receives appropriate shielding coverage tailored to its specific exposure risks.
3Ease of manufacture
If flip-chip MRAM package is used, then connection is achieved, but bottom shield opening area increases reducing magnetic shield efficiency
Solution Approach 1:
The side walls act as flexible shielding boundaries that can be configured to accommodate flip-chip packaging requirements. By removing substrate material to form side walls extending from the bottom shield, the structure provides enclosed shielding while allowing the necessary opening area for flip-chip connections. The thin film nature of the side walls (formed by substrate removal) maintains magnetic shielding efficiency while enabling manufacturing flexibility.
4Ease of manufacture
If larger wire-bonding pad area is used, then wire bonding is facilitated, but package thickness increases
Solution Approach 1:
The patent resolves the pad area-thickness tradeoff by transitioning to a three-dimensional enclosed structure. The side walls provide the necessary structural support and shielding function vertically, allowing the top and bottom shields to be positioned closer together without compromising shielding effectiveness. This dimensional reorganization enables smaller pad areas while maintaining adequate wire bonding capability and reducing overall package thickness.
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 approach achieves higher shielding efficiency with a thinner package profile, suitable for both wire bonding and flip-chip packages, reducing the risk of electrical shorts and enhancing magnetic shield efficiency.
Implementation Method 1
forming a first metal layer embedded between an upper and a lower portion of a PCB substrate... forming a second metal layer over and on four opposing sides of the semiconductor die... using a nickel-iron alloy to ensure comprehensive magnetic shielding
Data Source
AI summary
Methods of magnetically shielding an MRAM structure on all six sides in a thin wire or thin flip chip bonding package and the resulting devices are provided. Embodiments include forming a first metal layer embedded between an upper and a lower portion of a PCB substrate, the first metal layer having a pair of metal filled vias laterally separated; attaching a semiconductor die to the upper portion of the PCB substrate between the pair of metal filled vias; connecting the semiconductor die electrically to the PCB substrate through the pair of metal filled vias; removing a portion of the upper portion of the PCB substrate outside of the pair of metal filled vias down to the first metal layer; and forming a second metal layer over and on four opposing sides of the semiconductor die, the second metal layer landed on the first metal layer.