SiC Current-Sensing Layout Avoiding Bond Pad Heat Transfer
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Solution Overview
Problem
The detection accuracy of current values in semiconductor devices is compromised due to differences in heat escape through bonding wires, affecting the on-resistance between the current sensing portion and the source portion, which is exacerbated by the disparity in pad sizes and wire occupation areas.
Innovation Solution
The current sensing portion in the semiconductor device is positioned to avoid direct alignment under the wiring member's joint, using a SiC semiconductor substrate to maintain a fixed distance and reduce heat transfer, with additional insulation and structural arrangements to prevent shock and breakage, ensuring accurate current detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the current sensing portion is made smaller in area than the source portion to achieve proper sensing ratio, then the detection capability is improved, but the on-resistance error increases due to differential heat escape through bonding wires
Solution Approach 1:
The patent applies local quality by positioning the current sensing portion at a specific location where heat escape characteristics differ from the source portion. The sensing portion is deliberately placed in a region with different thermal properties (away from large pads with significant heat sinking) to create a measurable resistance difference that correlates with current flow, while maintaining accurate current detection capability
Solution Approach 2:
The patent implements preliminary action by pre-positioning the current sensing portion at a predetermined location during device fabrication, where the thermal characteristics are optimized to minimize on-resistance errors. The sensing portion is pre-configured with specific geometric parameters and spatial relationships to bonding wires and pads to establish favorable heat escape conditions before operation
2Device complexity
If the current sensing portion is positioned directly under the wiring member joint to simplify structure, then the device complexity is reduced, but the detection accuracy deteriorates due to heat transfer and shock effects
Solution Approach 1:
The patent applies the taking out principle by extracting the current sensing portion from the direct path under the wiring member joint. The sensing portion is positioned at a offset location that removes it from the primary heat transfer path and mechanical shock path of the bonding wire joint, thereby eliminating the adverse thermal and mechanical effects while maintaining electrical functionality
Solution Approach 2:
The patent introduces an intermediary positioning strategy where the current sensing portion is placed at an intermediate location between the source portion and the direct joint area. This intermediate position serves as a thermal and mechanical buffer zone, reducing the direct influence of joint-generated heat and shock on the sensing region while maintaining electrical connectivity
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 enhances the detection accuracy of current values by minimizing errors in on-resistance and preventing structural damage, while allowing for a smaller sensing portion to achieve the necessary sensing ratio, thus improving reliability and precision.
Implementation Method 1
the occupation area of the bonding wire with respect to the pad becomes large. This causes a difference in the amount of heat escaping through the bonding wire
Data Source
AI summary
A SiC semiconductor device is provided that is capable of improving the detection accuracy of the current value of a principal current detected by a current sensing portion by restraining heat from escaping from the current sensing portion to a wiring member joined to a sensing-side surface electrode. The semiconductor device includes a SiC semiconductor substrate, a source portion including a principal-current-side unit cell, a current sensing portion including a sensing-side unit cell, a source-side surface electrode disposed above the source portion, and a sensing-side surface electrode that is disposed above the current sensing portion and that has a sensing-side pad to which a sensing-side wire is joined, and, in the semiconductor device, the sensing-side unit cell is disposed so as to avoid being positioned directly under the sensing-side pad.