Junction Box Thermal Management via Insulated Relay Mounting
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Solution Overview
Problem
In electrical junction boxes used in vehicles, heat generated by semiconductor relays can transfer to control circuits, causing thermal issues when large currents are handled.
Innovation Solution
The design includes a conductive input and output busbar with a semiconductor relay mounted on at least one of them, separated from a substrate with a control circuit, and an insulating portion with higher thermal conductivity than the busbars, which covers the semiconductor relay's connections and is molded to create a thermal barrier, preventing heat transfer to the control circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the semiconductor relay is mounted directly on the busbar to reduce device complexity, then the device complexity is reduced, but heat generated by the semiconductor relay transfers to the control circuit
Solution Approach 1:
An insulating portion made of insulating material is introduced as an intermediary between the semiconductor relay and the control circuit. This insulating portion covers the connection portions of the semiconductor relay with the busbar and has a leg portion that protrudes toward the substrate, separating the busbar from the substrate and preventing heat transfer to the control circuit while maintaining electrical insulation.
Solution Approach 2:
The insulating portion is segmented into a main body portion covering the connection areas and a leg portion protruding toward the substrate. This segmentation allows the insulating structure to both cover the electrical connections and provide thermal separation by extending the insulating barrier between the heat-generating busbar and the control circuit substrate.
2Volume of stationary object
If the busbar and substrate are positioned close together to reduce the volume of the electrical junction box, then the volume is reduced, but heat from the busbar transfers to the control circuit on the substrate
Solution Approach 1:
The insulating portion extends in the vertical dimension with a leg portion protruding from the main body toward the substrate. This dimensional extension creates thermal separation between the busbar and substrate without requiring horizontal spacing, thus preventing heat transfer while maintaining compact volume.
3Temperature
If an insulating portion with higher thermal conductivity than the busbar is used to cover the semiconductor relay connections, then heat transfer to the control circuit is prevented, but the manufacturing complexity increases
Solution Approach 1:
The insulating portion is made of insulating material that provides both electrical insulation and thermal management properties. By using material with higher thermal conductivity than the busbar in specific regions, the design directs heat away from the control circuit while maintaining ease of manufacture through a molded single-piece structure.
Solution Approach 2:
The insulating portion serves multiple functions simultaneously: it provides electrical insulation for the connection portions, acts as a thermal barrier with its leg portion to prevent heat transfer to the substrate, and simplifies manufacturing by being molded as a single integrated component that covers all necessary areas.
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 effectively suppresses heat transfer from the semiconductor relay to the control circuit, ensuring reliable operation even under high current conditions.
Implementation Method 1
the insulating portion has thermal conductivity higher than thermal conductivity of the input busbar, the output busbar, and the semiconductor relay
Data Source
AI summary
An electrical junction box includes a conductive input busbar, a conductive output busbar electrically connectable to the input busbar, a semiconductor relay electrically connected to the input busbar and the output busbar and configured to switch a connected state and a disconnected state of the input busbar and the output busbar, a substrate having mounted thereon a control circuit configured to output a control signal for controlling the semiconductor relay, and a control terminal electrically connecting the control circuit and the semiconductor relay to each other to output the control signal to the semiconductor relay. The semiconductor relay is mounted on at least one of the input busbar and the output busbar. The input busbar, the output busbar, and the semiconductor relay are disposed away from the substrate.