Semiconductor Package Layout With Built-In Snubber Capacitance
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Solution Overview
Problem
Semiconductor devices face damage due to back electromotive force caused by rapid changes in current during switching, leading to voltage breakdown and malfunction, particularly in three-phase inverter circuits where wiring inductance contributes to this issue.
Innovation Solution
Incorporating snubber capacitors formed by wiring members and spacers between input and output electrodes of semiconductor chips, which absorb back electromotive force, reducing the risk of voltage breakdown and enhancing device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wiring members are used to connect semiconductor chips in a three-phase inverter circuit, then electrical connectivity is achieved, but wiring inductance causes back electromotive force during switching leading to voltage breakdown
Solution Approach 1:
An insulating substrate is introduced as an intermediary between the first and second lead frames. The insulating substrate provides a path for forming snubber capacitors that mitigate back electromotive force, while avoiding direct metal-to-metal contact that would create harmful inductance. This mediator structure enables both electrical functionality and protection against voltage breakdown.
Solution Approach 2:
The connection structure transitions from a planar two-dimensional layout to a three-dimensional configuration by stacking the first and second lead frames with the insulating substrate between them. This vertical stacking enables the formation of snubber capacitors in the third dimension (thickness direction), providing electromagnetic interference mitigation without increasing the footprint area.
2Area of stationary object
If lead frames are stacked to reduce device area, then footprint is reduced, but wiring inductance increases causing greater back electromotive force
Solution Approach 1:
The insulating substrate acts as a mediator that enables vertical stacking while minimizing harmful inductance. By providing controlled impedance paths and enabling capacitor formation, the insulating substrate allows compact three-dimensional stacking without proportionally increasing wiring inductance, thus reducing footprint while mitigating the harmful effects of inductance.
Solution Approach 2:
The structure changes the geometric parameters of the wiring paths by transitioning to vertical connections through the insulating substrate. This parameter change reduces the horizontal trace length and optimizes the current path, thereby controlling wiring inductance while achieving compact footprint through three-dimensional stacking.
3Device complexity
If direct metal-to-metal contact is used for electrical connection, then connectivity is simple, but electromagnetic interference and voltage breakdown occur
Solution Approach 1:
The insulating substrate serves as a mediator that replaces direct metal-to-metal contact with an insulated connection structure. This intermediary layer prevents galvanic corrosion and electromagnetic interference while enabling the formation of snubber capacitors that protect against voltage breakdown, thus reducing harmful effects with only moderate increase in structural complexity.
Solution Approach 2:
The insulating substrate, which initially appears to add complexity, actually converts the potential harm of direct contact (EMI and voltage breakdown) into a benefit by enabling capacitor formation. The same insulating layer that prevents direct short circuits also provides the dielectric necessary for snubber capacitor functionality, turning a structural constraint into a protective feature.
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
The implementation of snubber capacitors effectively mitigates the back electromotive force, preventing voltage breakdown and ensuring the reliability and stability of semiconductor devices during switching operations.
Implementation Method 1
wiring members 40a to 40c and spacers 43, respectively, between the input electrode 3h of the high-side semiconductor chip 3a1 and the output electrode 3g of the low-side semiconductor chip 3b1
Data Source
AI summary
A wiring member is connected to an output electrode of a semiconductor chip and to a wiring region of a main current lead frame via an insulating spacer. In this case, a snubber capacitor is formed by the wiring member and spacer between the input electrode of a (high-side) semiconductor chip and the output electrode of a (low-side) semiconductor chip. This snubber capacitor absorbs back electromotive force produced due to the wiring inductance of the wiring member and main current lead frame.