Stacked Die Isolation Layer for Galvanic Isolation
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Solution Overview
Problem
Existing integrated circuit packaging technologies face challenges in maintaining galvanic isolation between stacked die while allowing effective communication, particularly when dealing with high voltage domains and the risk of electrical arcing, especially when packaging multiple die in a single package.
Innovation Solution
The use of a preformed isolation layer extending beyond the edges of the top die, combined with a conductive ring on the isolation layer, provides galvanic isolation and minimizes the risk of electrical arcing by controlling the thickness and proximity of the die, ensuring sufficient creepage distance and electrical isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the die are placed in close proximity for effective communication, then communication effectiveness is improved, but the risk of destructive arcing increases due to higher electrical fields
Solution Approach 1:
An isolation layer is introduced as an intermediary between the first and second die. This isolation layer provides a physical barrier that increases the creepage distance between conductive elements on different die, thereby reducing the risk of electrical arcing while allowing the die to remain in close proximity for effective inductive coupling communication.
Solution Approach 2:
The isolation layer is applied in advance to the substrate before placing the die, creating a pre-established protective barrier. This preliminary action prevents the formation of direct conductive paths between die operating at different voltages, proactively counteracting the potential for arcing before it can occur.
2Reliability
If galvanic isolation is provided between stacked die, then electrical isolation and safety are improved, but the complexity of the packaging structure increases
Solution Approach 1:
The isolation layer serves multiple functions simultaneously: it provides galvanic isolation between die at different voltage levels, acts as a mechanical support structure for mounting die, and creates the necessary creepage distance for high voltage isolation. This multi-functionality reduces the need for additional separate isolation components, thereby limiting the increase in packaging complexity.
3Productivity
If multiple die are packaged in a single package, then productivity and integration are improved, but the difficulty of maintaining sufficient isolation between high voltage domains increases
Solution Approach 1:
The packaging structure is segmented into isolated zones using the isolation layer, which extends between and under multiple die. This segmentation creates distinct electrical domains that can be independently managed, allowing multiple high voltage domains to coexist in a single package while maintaining sufficient isolation between them.
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 solution effectively maintains galvanic isolation and prevents dielectric breakdown, enabling safe and efficient communication between inductors in stacked die while allowing for the packaging of multiple high voltage domains within a single package.
Implementation Method 1
In order for the communication to be effective, the die must be in close proximity. However, the closer in proximity the die are, the higher the electrical fields between the die and hence the greater chance of destructive arcing. Therefore, the galvanic isolation should be sufficient to prevent destruction of the isolation between the die
Implementation Method 2
Communication between integrated circuit (IC) die can be achieved using inductive coupling in which two die can use transmitting and receiving inductors to communicate
Data Source
AI summary
A packaged integrated circuit (IC) device includes a first set of stacked die having a first IC die, a first inductor in the first IC die, an isolation layer over the first IC die, a second IC die over the isolation layer, and a second inductor in the second IC die aligned to communicate with the first inductor, and a second set of stacked die having a third IC die, a third inductor in the third IC die, a second isolation layer over the third IC die, a fourth IC die over the second isolation layer, and a fourth inductor in the fourth IC die aligned to communicate with the third inductor. The isolation layer extends a prespecified distance beyond a first edge of the second IC die, and the second isolation layer extends a second prespecified distance beyond a first edge of the fourth IC die.