Cooling device
The cooling device addresses the issue of thermal expansion-induced delamination by using a metal intermediate layer and protrusions or hybrid thermal conduction layer with metal springs to maintain contact and enhance heat dissipation.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-09-24
- Publication Date
- 2026-04-06
AI Technical Summary
The difference in thermal expansion coefficients between power supply circuits and heat sinks causes deformation and delamination, leading to ineffective heat dissipation in cooling devices due to dynamic temperature fluctuations.
A cooling device with a metal intermediate layer connected by a solder layer between the power supply circuit and the heat conduction layer, and protrusions or a hybrid thermal conduction layer with embedded metal springs to ensure permanent contact and prevent delamination.
The solution effectively maintains reliable connection and enhances heat dissipation by compensating for thermal expansion, preventing delamination and ensuring efficient heat transfer.
Smart Images
Figure 2026059025000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a cooling device including a power supply circuit, a heat sink, and a heat conduction layer disposed between the power supply circuit and the heat sink and formed of a heat conduction material.
Background Art
[0002] The electric drive of a vehicle involves the use of power semiconductors or other electronic or electrical components that lose heat during operation. The heat loss is dissipated through a heat sink. The heat sink is usually made of aluminum. The power supply circuit may be disposed on a support such as a printed circuit board. A heat conduction layer formed of a heat conduction material is disposed between the heat sink and the power supply circuit and can compensate for the difference in temperature-dependent expansion between the heat sink and the power supply circuit within a certain limit.
[0003] The carrier on which the power supply circuit is mounted may be a copper-based circuit board or an AMB layer (active metal brazing). To ensure good heat transfer, the power supply circuit is mounted flat on the heat sink. However, the coefficient of thermal expansion of the power supply circuit carrier and the coefficient of thermal expansion of the heat sink are significantly different. The difference in expansion between the power supply circuit and the heat sink can cause deformation or distortion of the power supply circuit and its carrier. The heat conduction layer itself is also exposed to deformation or movement. Under the influence of periodic temperature fluctuations, there is a risk that the power supply circuit separates from the heat conduction layer and weakens heat dissipation. Therefore, measures are needed to prevent delamination that may occur under the influence of dynamic temperature fluctuations. For the cooling device to function properly, sufficient connection and close bonding between the power supply circuit and the heat sink are required.
Summary of the Invention
[0004] Therefore, the present invention is based on the object of providing a cooling device that ensures permanent contact between the power supply circuit and the heat sink.
[0005] To achieve this objective, a cooling device having the features of claim 1 is provided.
[0006] The cooling device according to the present invention is identified by the placement of a metal intermediate layer between the power supply circuit and the heat conduction layer, which is connected to the power supply circuit by a solder layer.
[0007] The metal interlayer provided by the present invention has the effect of reducing distortion in the power supply circuit when the power supply circuit is subjected to dynamic temperature fluctuations. The metal interlayer is selected so that it can be connected to the power supply circuit with high reliability by a soldering process.
[0008] Preferably, the intermediate layer is made of copper or molybdenum copper. Alternatively, the intermediate layer may be coated with copper or molybdenum copper. The intermediate layer may be thin with respect to the carriers of the power circuit and, in particular, may be formed as a metal sheet. The intermediate layer has good adhesion to the thermal conductive layer so that the thermal conductive layer does not delaminate or get damaged even under conditions of dynamic temperature fluctuations.
[0009] The solder layer may be formed from a zinc-titanium nitride alloy or a zinc-aluminum alloy. These alloys provide particularly reliable soldered connections.
[0010] The power supply circuit may have an AMB (Active Metal Brazing) layer on the surface facing the intermediate layer. The AMB layer enables good connectivity with the intermediate layer.
[0011] Furthermore, within the scope of the present invention, the heat sink may also have a protrusion embedded in the heat conduction layer on the surface facing the power supply circuit. This engagement creates a particularly good mechanical connection between the heat conduction layer and the heat sink, preventing delamination of the heat conduction layer.
[0012] If the cooling device according to the present invention has two spaced-apart protrusions, the result is particularly good retention between the heat conduction layer and the heat sink.
[0013] In this context, it is preferable that the protrusion be located at the same position as the semiconductor components of the power supply circuit. The protrusion may also be located between two semiconductor components of the power supply circuit. Heat dissipation is better at the location of the protrusion than at an intermediate position. For this reason, it is advantageous to place the protrusion at the same position as the semiconductor components.
[0014] Preferably, the protruding portion of the cooling device according to the present invention may be formed as a stepped portion having a rectangular cross-section. The corners of the stepped portion may also be rounded.
[0015] Further improvements can be achieved with a hybrid thermal conduction layer that incorporates a gel with embedded metal springs extending across the thermal conduction layer. The metal springs allow heat to dissipate across the thermal conduction layer. The springs extend from one end of the thermal conduction layer to the other, thereby enabling direct heat conduction from the power circuit to the heatsink.
[0016] Along with a hybrid thermal conductive layer, silicone gel can be used as the gel. Silicone gel is also suitable for the high temperatures that occur during the operation of power circuits.
[0017] The springs of the hybrid thermal conductive layer may be made from one of the following materials: titanium nitride, indium, copper, or beryllium copper. These materials allow for good heat dissipation from the power circuit. Preferably, springs made of copper or beryllium copper are made from bent flat material.
[0018] The present invention will be described below based on embodiments with reference to the drawings. The drawings are schematic diagrams. [Brief explanation of the drawing]
[0019] [Figure 1] A cross-sectional view of a first embodiment of the cooling device according to the present invention is shown. [Figure 2]A cross-sectional view of a second embodiment of the cooling device according to the present invention is shown. [Figure 3] Figure 2 shows the cooling system under different operating conditions. [Figure 4] A cross-sectional view of a third embodiment of the cooling device according to the present invention is shown. [Modes for carrying out the invention]
[0020] The cooling device 1 shown in the cross-sectional view in Figure 1 comprises a power supply circuit 2 and a heat sink 3, as schematically shown. The power supply circuit 2 may be part of an inverter that converts, for example, a DC voltage supplied by a battery into a multiphase AC voltage capable of driving the vehicle's electric motor.
[0021] During operation of the power supply circuit 2, lost heat exists and must be dissipated in order to maintain a temperature below a certain limit. The power supply circuit 2 has a carrier, which is an AMB (Active Metal Brazing) substrate, on the side facing the heat sink 3. The carrier may be made of copper or may have a copper coating. The heat sink 3 is usually made of aluminum or an aluminum alloy. The thermal expansion coefficients of the power supply circuit 2 and the heat sink 3 are significantly different. If the power supply circuit 2 is fixedly connected to the heat sink 3, the different expansions will cause mechanical stress. For this reason, a thermal conductive layer 4, formed from a thermal interface material (TIM), is placed between the power supply circuit 2 and the heat sink 3.
[0022] To ensure a good connection of the heat conduction layer 4 to the power supply circuit 2, a metal intermediate layer 5 is disposed between the power supply circuit 2 and the heat conduction layer 4. In the present embodiment, the intermediate layer 5 is made of copper. In other embodiments, the intermediate layer 5 may be made of molybdenum copper. The intermediate layer 5 is a thin metal sheet and is connected to the heat conduction layer 5 by a solder layer 6. In the present embodiment, a zinc-titanium nitride alloy is used as the solder layer. The intermediate layer 5 has the effect that the temperature-dependent expansion of the power supply circuit 2 does not lead to delamination of the heat conduction layer 4. Due to the good connection of the thin intermediate layer 5 of the power supply circuit 2, the heat conduction layer 4 can compensate for different expansions. The loss heat generated during the operation of the power supply circuit 2 is dissipated to the heat sink 3.
[0023] Figures 2 and 3 show a second embodiment of a cooling device 7 configured in the same manner as the cooling device 1. For overlapping components, no detailed description will be given here again. The cooling device 7 includes a power supply circuit 8, a heat sink 9, and a heat conduction layer 10 disposed therebetween. A metal intermediate layer 11 is disposed between the power supply circuit 8 and the heat conduction layer 10.
[0024] Unlike the first embodiment, the heat sink 9 has two spaced-apart protrusions 12 on the surface facing the power supply circuit 8. The protrusions 12 are arranged in the transverse direction of the heat sink 9 and a stepped portion is formed. The positions of the protrusions 12 are selected such that each protrusion is located under the chip 13 of the power supply circuit 8. During operation, since the distance between the hot chip 13 and the protrusion 12 is small, any generated loss heat can be surely dissipated.
[0025] In FIGS. 2 and 3, the warpage of the power supply circuit 8 under the influence of temperature is exaggeratedly shown. FIG. 2 shows a state where no current is flowing at a temperature of 150°C. In this case, the power supply circuit warps convexly. The intermediate layer 11 prevents the heat conduction layer from separating when this occurs.
[0026] FIG. 3 shows the cooling device 7 when a current of 250 A is flowing at a temperature of 25°C. In this state, the power supply circuit 8 exhibits opposite behavior, that is, it deforms into a concave shape. The protruding portion 12 in this case functions as a base point to which the heat conduction layer 10 is fixed, and the outer periphery of the heat conduction layer 10 can be bent at least slightly. In both cases, reliable contact between the cooling device 7 and the heat conduction layer 10 is ensured by the intermediate layer 11.
[0027] The cooling device 14 shown in FIG. 4 is configured in a manner similar to the first embodiment. However, it is different in the heat conduction layer 15, which is a hybrid heat conducting layer. This means that the heat conduction layer 15 includes a gel in which the metal spring 16 is embedded. The spring 16 is double angled and extends in opposite directions from the central portion. The outer legs of the spring 16 are parallel to the surfaces of the power supply circuit 2 and the heat sink 3. The central portion of the spring 16 extends across the hybrid heat conduction layer 15. In the embodiment shown, the spring 16 is made of beryllium copper. Titanium nitride, indium or copper can also be used as alternative materials. The loss heat generated during the operation of the power supply circuit 2 can be dissipated to the heat sink 3 through the spring 16. The spring 16 integrated within the heat conduction layer 15 can compensate for the temperature-dependent displacement of the power supply circuit 2 with respect to the heat sink 3. This ensures the integrity of the heat conduction layer 15 and prevents delamination.
Claims
1. Power supply circuit (2, 8), Heatsink (3, 9) and Displaced between the power supply circuit (1, 7, 14) and the heat sink (3, 9), a thermal conductive layer (4, 10, 15) formed from a thermal conductive material is provided. Equipped with, A cooling device (1, 7, 14) is provided, in which a metal intermediate layer (5, 11) connected to the power supply circuit (1, 7, 14) by a solder layer (6) is arranged between the power supply circuit (1, 7, 14) and the heat conductive layer (4, 10, 15).
2. The cooling device according to claim 1, wherein the intermediate layers (5, 11) are made of copper or molybdenum copper, or are coated with copper or molybdenum copper.
3. The cooling device according to claim 1 or 2, wherein the solder layer (6) is formed as a zinc-titanium nitride alloy or a zinc-aluminum alloy.
4. The cooling device according to any one of claims 1 to 3, wherein the power supply circuit (1, 7, 14) has an AMB (activated metal brazing) layer on the surface facing the intermediate layer (5, 11).
5. The cooling device according to any one of claims 1 to 4, wherein the heat sink (3, 9) has a projection (12) on the surface facing the power supply circuit (1, 7, 14) that extends longitudinally and is embedded in and interlocked with the heat conductive layer (10).
6. The cooling device according to claim 5, wherein two spaced-apart protrusions (12) are present in the cross-sectional direction of the heat sink (3, 9).
7. The cooling device according to claim 5 or 6, wherein the protruding portion (12) is located at the position where the semiconductor component (13) of the power supply circuit (7) is located, or between the two semiconductor components of the power supply circuit (7).
8. The cooling device according to any one of claims 5 to 7, wherein the protruding portion (12) is formed as a stepped portion having a rectangular cross-section.
9. The cooling device according to any one of claims 1 to 8, wherein the heat conductive layer (15) is in a hybrid form and comprises a gel incorporating an embedded metal spring (16) extending across the heat conductive layer (15).
10. The cooling device according to claim 9, wherein the gel is a silicone gel.
11. The cooling device according to claim 9 or 10, wherein the spring (16) is made from one of the following materials: titanium nitride, indium, copper, or beryllium copper.
12. The cooling device according to any one of claims 9 to 11, wherein the spring (16), which is made of copper or beryllium copper, is made from a bent flat plate material.