DESC:FIELD OF THE INVENTION:

[0001] The present invention generally relates to a heat transfer mechanism in rotating machines. More specifically, it relates to PCB assembly for effective heat transfer from a MOSFET to a motor housing in rotating machines without the need for a dedicated heat sink.

BACKGROUND:
[0002] MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) are commonly used in Brushless DC (BLDC) motors, which are often found in applications such as modern electronic motor drives and control systems of rotating machines, electric vehicles, drones, and computer cooling fans to control the flow of electrical current through the motor. They can be used to turn the motor on and off, as well as to adjust the speed and torque of the motor. MOSFETs are preferred over other types of transistors due to their high switching speeds and low power consumption.
[0003] It is well-known that motors generate heat due to the electrical resistance of the circuit and the movement of the motor. The heat generated is a result of conversion of electrical energy into mechanical energy. The Printed Circuit Board Assembly (PCBA) and MOSFET in PCBA should be designed in such a way that the heat transfer should be away from the critical components of the motor in order to prevent overheating and damage.
[0004] For this purpose, a heat sink is used to dissipate heat away from the electronic components, such as MOSFETs and motors. Heat sink is typically made of a material with high thermal conductivity, such as aluminium or copper, and is designed to have a large surface area in order to increase the rate of heat transfer. A heat sink helps to keep the temperature of the MOSFETs and motors within a safe range by removing the excess heat from the components and transferring it to the surrounding environment.
[0005] Below prior art uses heat sink to release heat from the circuit elements of the motor.
[0006] United States Patent Number 6998740 to Asmo Co Ltd entitled “Drive circuit device and motor having the same” discloses a drive circuit device for a motor, the drive circuit device comprising: a plurality of circuit elements that are provided to operate the motor and generate heat upon operation thereof; a heat sink member that releases the heat, which is generated from one or more of the plurality of circuit elements; a control circuit that controls operation of the motor; and a circuit board that supports the plurality of circuit elements, the heat sink member and the control circuit, wherein: the heat sink member divides the circuit board into a first circuit part and a second circuit part; the first circuit part includes at least one of the plurality of circuit elements; and the second circuit part includes the control circuit.
[0007] Existing prior art employs dedicated heat sink for heat transfer and are focused on bottom side cooling of the MOSFET. Also, with existing mechanisms, the heat transfer mechanism has high thermal resistance since the heat thermal conduction path is from MOSFET to PCB then PCB to heat sink via Thermal Interface Material (TIM) sheet and also it involves only bottom-side cooling of the MOSFET.
[0008] In order to overcome the aforementioned limitations, the present invention proposes a PCB assembly for effective heat transfer from MOSFET through direct thermal conduction path without the need of dedicated heat sink but thereby improving the thermal efficiency with better cost and enhanced reliability and better assembly feasibility.

OBJECTIVES OF THE INVENTION:
[0009] The primary objective of the present invention is to provide a PCB assembly for effective heat transfer from MOSFET without need of dedicated heat sink in rotating machines.
[0010] Another objective of the present invention is to employ thermal conductive metal for direct thermal conduction path from MOSFET to the heat sink and to improve the thermal efficiency with better cost and provide enhanced reliability and better assembly feasibility.

SUMMARY:
[0011] The following summary is provided to facilitate a clear understanding of the new features in the disclosed embodiment, and it is not intended to be a full, detailed description. A detailed description of all the aspects of the disclosed invention can be understood by reviewing the full specification, the drawing, and the claims and the abstract, as a whole.
[0012] In order to achieve the aforementioned objectives, the present invention discloses a PCB assembly for effective heat transfer from MOSFET to a thermally conductive metal.
[0013] According to present invention, effective heat transfer is possible because of direct thermal conduction path from MOSFET to the heat sink via Thermal Interface Material (TIM) sheet.
[0014] In an embodiment, effective heat transfer from MOSFET to the thermally conductive metal occurs via housing using top side cooling MOSFET package and housing act as a heat sink.
[0015] In another embodiment, effective heat transfer from MOSFET to the thermally conductive metal occurs via integrated housing using top side cooling MOSFET package and housing act as a heat sink.
[0016] In yet another embodiment, effective heat transfer is also possible by using a direct thermal conduction path from MOSFET to the intermediate thermally conductive material (may be copper plate/material, or any material having high conductive than housing material) in the heat sink via TIM sheet.
[0017] The effective heat transfer mechanism according to present invention increases the thermal efficiency with better cost, enhanced reliability and better assembly feasibility.

BRIEF DESCRIPTION OF THE DRAWINGS:
[0018] The present invention will be better understood fully from the detailed description that is given herein below with reference to the accompanying drawings of the preferred embodiments of the present invention, which, however, should not be deemed to be a limitation to the invention to the specific embodiments, but, are for the purpose of explanation and understanding only.
FIG. 1 (a) and 1(b) shows the PCB assembly with MOSFET mounted on it;
FIG. 2 illustrates the PCB assembly with thermally conductive material being integrated into the housing according to an embodiment of the present invention;
FIG. 3 shows the placement of TIM sheet and housing in PCBA;
FIG. 4 shows the placement of MOSFET in PCBA;
FIG. 5 shows the PCB assembly stacking arrangements according to present invention;
FIG. 6 shows the MOSFET and TIM material being integrated into the housing; and
FIG. 7 shows the exploded view of PCB assembly, TIM material and housing.

REFERENCE NUMERALS:

1 – MOSFET
2 – TIM Material / TIM Sheet
3 – PCB Assembly (PCBA)
4 – High Thermal Conductivity Metal (Soldered on MOSFET)
5 – Housing (Acts as heat sink) / Aluminium Housing
10 – Assembly stacking arrangements

DETAILED DESCRIPTION OF THE INVENTION:
[0019] The following is a detailed description of the present disclosure depicted in the accompanying drawings. However, it may be understood by a person having ordinary skill in the art that the present subject matter may be practiced without these specific details. In other instances, well known methods, procedures, and/or components regarding the said method have not been described in detail so as not to obscure the subject matter of the disclosure. The subject matter of the disclosure will be more clearly understood from the following description of the embodiments thereof, given by way of example only with reference to the accompanying drawings, which are not drawn to scale.
[0020] If the specification states that a component or a feature “may” or “can” be included, that particular component or feature is not required to be included or have the characteristic. The use of open-ended terms like “comprising” and variations herein is meant to encompass the steps listed thereafter and equivalents thereof as well as additional items. As used herein, the singular forms “a,” “an,” and “the” designate both the singular and the plural, unless expressly stated to designate the singular only.
[0021] The term “MOSFET” refers to metal-oxide-semiconductor field-effect transistor which is a device that act as voltage-controlled current sources, and are mainly used as switches or for the amplification of electrical signals. A Thermal Interface Material (TIM) sheet is a thin material designed to enhance the thermal conductivity between two surfaces by filling gaps and irregularities, promoting efficient heat transfer. A PCB is a "Printed Circuit Board" serving as a platform for mechanically supporting and electrically connecting electronic components.
[0022] The present invention discloses a PCB assembly for effective heat transfer from MOSFET to a thermally conductive metal in modern electronic motor drives and control systems of rotating machines.
[0023] Referring to FIG. 1 (a) and 1 (b), it shows the PCB assembly (3) with TIM (2) and MOSFET (1) placed in the assembly (3) and also includes housing (5) made up of materials like aluminium, but not limited to the same.
[0024] Referring to FIG. 2, it shows the PCB assembly (3) with thermally conductive material being integrated into the housing (5) according to an embodiment of the present invention.
[0025] In accordance with present invention, the thermally conductive material is preferably made up of copper or aluminium, but not limited to it. The heat transfer from MOSFET (1) to high thermal conductive material (4) occurs with the support of TIM sheet (2). Further, the TIM sheet (2) is preferably made up of silicone-based materials or waxes or any flexible fibres with suitable thermal conductive fillers/paste, but not limited to it.
[0026] According to present invention, effective heat transfer is possible because of direct thermal conduction path from MOSFET (1) to the heat sink via Thermal Interface Material (TIM) sheet (2). FIG. 3 shows the placement of TIM sheet (2) and housing (5) in PCBA (3).
[0027] In an embodiment, effective heat transfer from MOSFET (1) to the thermally conductive metal occurs via housing (5) using top side liquid cooling MOSFET (1) package and housing (5) act a heat sink. FIG. 4 shows the placement of MOSFET (1) in PCB Assembly (3).
[0028] FIG. 5 shows the PCB assembly (3) stacking arrangements according to present invention.
[0029] In another embodiment, effective heat transfer from MOSFET (1) to the thermally conductive metal occurs via integrated housing (5) using top side cooling MOSFET (1) package and housing (5) act as a heat sink as shown in FIG. 6. Also, the housing (5) of the rotating machines can be preferably made of copper, aluminium, iron, etc but not limited to it.
[0030] In another alternative embodiment, FIG. 7 shows the exploded view of PCB assembly (3), TIM material (2) and housing (5) without the need of high conductivity material (4).
[0031] In yet another embodiment, effective heat transfer is also possible by using a direct thermal conduction path from MOSFET (1) to the intermediate thermally conductive material (may be copper plate/material, or any material having high conductive than housing material) in the heat sink via TIM sheet (2).
[0032] Thus, the effective heat transfer mechanism according to present invention increases the thermal efficiency with better cost, enhanced reliability and better assembly feasibility.
[0033] The above description includes the preferred best mode of one embodiment of the present invention. It will be clear from this description of the invention that the invention is not limited to these illustrated embodiments but that the invention also includes a variety of modifications and embodiments thereto. Therefore, the present description should be seen as illustrative and not limiting. While the invention is susceptible to various modifications and alternative constructions, it should be understood, that there is no intention to limit the invention to the specific form disclosed, but, on the contrary, the invention is to cover all modifications, alternative constructions, and equivalents falling within the true scope of the present subject matter.
,CLAIMS:1. A printed circuit board (PCB) assembly (3) for heat transfer in rotating machines, comprising:
a. a MOSFET (1) soldered in the PCB assembly (3);
b. a housing of rotating machines (5);
c. a thermal interface material (TIM) sheet (2) placed in between a thermally conductive material (4) and the PCB assembly (3), wherein
i. the thermally conductive material (4) is placed in between the TIM sheet (2) and the housing (5) of rotating machines;
ii. the housing (5) functions as a heat sink for transfer of heat generated by the MOSFET (1) and the TIM sheet (2) transfers heat from the MOSFET (1) to the high thermal conductive material (4).

2. The PCB assembly (3) as claimed in claim 1, wherein the heat transfer from the MOSFET (1) to the thermally conductive metal (4) occurs through integrated housing (5) using top side cooling the MOSFET (1) package and the housing (5) functions as a heat sink.

3. The PCB assembly (3) as claimed in claim 1, wherein the heat transfer occurs by direct thermal conduction path from the MOSFET (1) to the thermally conductive material in the heat sink through TIM sheet (2).

4. The PCB assembly (3) as claimed in claim 1, wherein the thermally conductive material (4) is preferably made up of copper or aluminium.
5. The PCB assembly (3) as claimed in claim 1, wherein the TIM sheet (2) is preferably made up of silicone-based materials or waxes or any flexible fibres with suitable thermal conductive fillers/paste.