Overmolded PCB Motor Power Pack Thermal Sealing
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Solution Overview
Problem
Electrical components such as motor power packs in vehicles are susceptible to moisture ingress and failure when exposed to water, as the sealing gaskets distort and allow moisture entry, lacking redundancy and functionality after failure.
Innovation Solution
A motor electronics unit with a printed circuit board, heat sink, and pre-molded electrical connector shroud, housed in a thermally conductive polymeric material, where the housing encapsulates the board and connector shroud, providing a hermetic seal and efficient heat transfer while allowing exposed heat sink fins for cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing gasket is used to seal the housing cavity, then the electrical components are protected from moisture, but the gasket distorts when the housing contracts due to thermal cooling, allowing moisture to enter
Solution Approach 1:
The patent changes the material parameter of the housing from traditional metal to thermally conductive polymer, which has different thermal expansion characteristics. This material substitution resolves the contradiction by providing a housing that maintains dimensional stability during thermal cycling, preventing gasket distortion while still allowing effective heat transfer to the heat sink.
Solution Approach 2:
The patent uses composite material construction with thermally conductive polymer housing combined with heat transfer pads and thermal interface materials. This composite approach enables the housing to simultaneously achieve moisture sealing stability and thermal conductivity, resolving the contradiction between sealing integrity and heat dissipation.
2Reliability
If the housing is sealed to protect electrical components, then moisture protection is improved, but heat transfer from electrical components becomes less efficient
Solution Approach 1:
The patent introduces heat transfer pads as intermediary elements between the electrical components and the housing, and between the housing and external heat sinks. These thermal interface materials mediate the heat transfer process while maintaining the sealed enclosure, allowing efficient heat conduction without compromising the moisture protection provided by the sealed housing.
Solution Approach 2:
The patent changes the thermal conductivity parameter of the housing material by using thermally conductive polymer instead of traditional non-conductive materials. This parameter change enables the sealed housing to actively participate in heat dissipation, maintaining both moisture protection and improved heat transfer efficiency.
3Ease of manufacture
If traditional sealing methods are used, then manufacturing is simpler, but the system lacks redundancy and functionality after failure when subjected to water impingement
Solution Approach 1:
The patent implements beforehand cushioning by using overmolded connectors that are integrally formed with the housing, creating a redundant sealing system. This prior cushioning approach ensures that even if the primary gasket sealing fails under water impingement conditions, the overmolded connector seals provide backup protection, maintaining functionality after failure.
Solution Approach 2:
The patent uses composite construction combining molded housing, gasket seals, and overmolded connector seals. This multi-layer composite sealing approach provides both ease of manufacture through integral molding and enhanced reliability through redundant sealing mechanisms that maintain functionality after failure.
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 solution effectively protects electrical components from moisture, enhances heat transfer efficiency, and eliminates the need for additional heat transfer pads, while maintaining an environmental seal around connectors, thus addressing the failure mode due to water exposure.
Implementation Method 1
a housing molded from a low pressure injection molded thermally conductive polymeric material
Implementation Method 2
A heat sink is positioned proximate to the printed circuit board
Implementation Method 3
the sensor is a Hall Effect sensor
Data Source
AI summary
A motor electronics unit includes a printed circuit board having a first side and a second side with electronic components connected to the printed circuit board. An electrical conductor is connected to the printed circuit board. A heat sink is connected to the printed circuit board. A pre-molded electrical connector shroud has a portion of the electrical conductor positioned within the electrical connector shroud. A housing has an endcap, both co-molded in a low pressure injection molding process of a thermally conductive polymeric material. The endcap encapsulates the printed circuit board including the electronic components connected to the printed circuit board and covers a first portion of the heat sink, with a second portion of the heat sink uncovered by the polymeric material of the endcap to permit heat transfer away from the printed circuit board. The endcap also encapsulates a portion of the electrical connector shroud.