Shunt Resistor Bonding Wire Orientation for Noise Reduction
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Solution Overview
Problem
Current shunt resistor designs face challenges in accurately measuring current values due to increased heating and noise induction from magnetic flux, particularly when bonding wires are extracted orthogonally to the shunt resistor's extension direction, leading to reduced accuracy and feasibility in size reduction.
Innovation Solution
A shunt resistor configuration where bonding wires are extracted parallel to the extension direction of the bridging part, reducing the loop area of the sense current and minimizing induced electromotive force, thereby enhancing measurement accuracy and allowing for a more compact design by directly connecting the shunt resistor to a lead frame with high heat capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If bonding wires are extracted in a direction substantially perpendicular to the extension direction of the shunt resistor, then the current detection structure is simplified, but the enclosed area by the sense current path becomes large and electromotive force is readily induced by magnetic flux
Solution Approach 1:
The bonding wires are extracted asymmetrically in a direction substantially parallel to the extension direction of the shunt resistor rather than perpendicular to it. This asymmetric arrangement minimizes the enclosed area by the sense current path, thereby reducing the electromotive force induced by magnetic flux while maintaining structural simplicity
Solution Approach 2:
The extraction direction of the bonding wires is changed from the conventional perpendicular direction to a parallel direction along the extension direction of the shunt resistor. This dimensional reorientation fundamentally reduces the loop area enclosed by the sense current, solving the electromagnetic interference problem
2Measurement precision
If current flowing through the resistive element is increased to improve measurement sensitivity, then the heating value of the resistive element increases, but measurement sensitivity is improved
Solution Approach 1:
The lead frame serves as an intermediary heat dissipation component between the resistive element and the external environment. By directly connecting the resistive element to the lead frame with high heat capacity and thermal conductivity, the lead frame acts as a heat sink that efficiently conducts away the heat generated by high current flow, enabling sustained high-current operation for improved measurement sensitivity
3Volume of moving object
If the shunt resistor is designed with compact dimensions to reduce size, then the enclosed area is reduced and less magnetic flux is induced, but the heat dissipation capability may be compromised
Solution Approach 1:
The lead frame is designed to serve multiple functions simultaneously: it provides mechanical support for the compact shunt resistor structure, acts as a heat sink for efficient heat dissipation from the resistive element, and serves as an electrical connection element. This multi-functionality enables compact dimensions while maintaining adequate heat dissipation capability
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 noise interference in potential difference measurements, enabling more accurate current detection and allowing for a smaller, more efficient shunt resistor design that effectively dissipates heat.
Implementation Method 1
A current value is measured by using a shunt resistor according to a resistance value of a resistive element forming the shunt resistor and a potential difference across the shunt resistor
Implementation Method 2
two connecting parts affixed to the electrodes via a conductive adhesive, respectively, and the connecting parts electrically connected to the affixed electrodes
Implementation Method 3
a heating value of the resistive element is also increasing. A need is thus arising from a viewpoint of heat dissipation to directly connect the shunt resistor to a member having a large heat capacity and relatively high heat conductivity, such as a lead frame
Implementation Method 4
Density of a magnetic flux induced by a current also becomes higher as a current flowing through the resistive element increases and the magnetic flux induces an electromotive force to a peripheral circuit
Data Source
AI summary
A shunt resistor, at least a part of which has a resistive element with pre-set resistivity, is configured to bridge between two electrodes and detect a current value of a current flowing between the electrodes by detecting a voltage drop in the resistive element. The shunt resistor includes two connecting parts affixed to the electrodes via a conductive adhesive, respectively, and the connecting parts electrically connected to the affixed electrodes, a bridging part bridging between the connecting parts by being extended from one of the connecting parts to the other one of the connecting parts, and two bonding wires used to detect a voltage drop in the resistive element. The two bonding wires are extracted parallel to an extension direction of the bridging part to a same direction.