Bi-directional Battery Switch Side-by-Side Die Layout
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Solution Overview
Problem
Conventional bi-directional and reverse blocking battery switches face challenges with high series drain resistance, which necessitates the use of backmetal, increasing costs and potential failure modes, while also limiting pin connections and pin pitch, thereby affecting electrical and thermal resistance.
Innovation Solution
The improved die layout orients two switches side-by-side within a die package, eliminating the need for backmetal by reducing total switch resistance, allowing for more pin connections and increased pin pitch, and enabling redundant connections for higher current handling, thus minimizing costs and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If two MOSFETs are connected end-to-end in a die package, then the package fits within desired footprint dimensions, but the internal drain connection resistance becomes high
Solution Approach 1:
The patent transitions from a one-dimensional end-to-end arrangement to a two-dimensional side-by-side arrangement of MOSFETs on the die. This dimensional change allows the drains to be positioned adjacent to each other rather than separated by the length of two devices, significantly reducing the drain connection resistance while maintaining a compact footprint.
2Reliability
If backmetal is used to reduce drain resistance, then resistance specifications are met, but manufacturing complexity and potential failure modes increase
Solution Approach 1:
The patent extracts and eliminates the backmetal layer from the die structure. By adopting a side-by-side MOSFET configuration, the design achieves low drain resistance through direct adjacent connections without requiring the additional backmetal infrastructure, thereby simplifying manufacturing and reducing potential failure modes associated with backmetal deposition and bonding.
3Reliability
If pin pitch is increased to accommodate more connections, then electrical and thermal resistance improve, but die area increases
Solution Approach 1:
The patent merges the drain connections of multiple MOSFETs by positioning them side-by-side with adjacent drains. This consolidation allows multiple current paths to share common connection points and reduces the overall distance current must travel, improving electrical and thermal resistance without requiring increased pin pitch or additional die area.
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 configuration reduces electrical and thermal resistance, eliminates potential manufacturing failures, and fits within desired die footprints, enhancing the reliability and cost-effectiveness of battery switch assemblies.
Implementation Method 1
two N-channel Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) 108 and 109
Implementation Method 2
N-channel MOSFETs include source inputs 101 and 106, and gate inputs 102 and 105
Implementation Method 3
utilizing an intrinsic body diode that inherently blocks the flow of current in one direction
Implementation Method 4
common drains 103 and 104 are connected by die-attaching two standard MOSFETs 108 and 109 to a common copper die pad 107
Implementation Method 5
This configuration achieves both a direct thermal path for heat sinking
Data Source
AI summary
Embodiments of the present invention relate to an improved package for a bi-directional and reverse blocking battery switch. According to one embodiment, two switches are oriented side-by-side, rather than end-to-end, in a die package. This configuration reduces the total switch resistance for a given die area, often reducing the resistance enough to avoid the use of backmetal in order to meet resistance specifications. Elimination of backmetal reduces the overall cost of the die package and removes the potential failure modes associated with the manufacture of backmetal. Embodiments of the present invention may also allow for more pin connections and an increased pin pitch. This results in redundant connections for higher current connections, thereby reducing electrical and thermal resistance and minimizing the costs of manufacture or implementation of the die package.