Thermal Conductance Management Architecture for Electronic Devices

Abstract

To provide an electronic assembly capable of dissipating heat without using convective heat transfer.SOLUTION: An electronic assembly includes a first printed wiring board (PWB) on a first side of the electronic assembly, and a first stiffener secured to the first PWB. The electronic assembly also includes a second PWB on a second side of the electronic assembly opposite the first side, a second stiffener secured into the second PWB, and a center stiffener seated in the second stiffener and between the first stiffener and the second stiffener. The center stiffener has a first side facing the first stiffener, a second side that is opposite the first side and faces the second stiffener, a first end, and a second end opposite the first end. Electronic devices are secured to the center stiffener. The center stiffener dissipates heat from the electronic devices, and the electronic devices include power dies.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] Exemplary embodiments relate to the technology of electronic devices, and more particularly, to a thermal conduction management architecture for electronic devices.

Background Art

[0002] Electronic devices such as power dies and diodes are used in a wide range of applications. When these devices are installed, they are prone to exposure to the surrounding atmosphere, and convective heat transfer can be used to cool these heat-generating devices. However, such exposure, and thus the resulting convective heat transfer, may not be possible based on specific applications. In these cases, thermal conduction management must be used.

Summary of the Invention

Means for Solving the Problems

[0003] In one embodiment, an electronic assembly includes a first printed wiring board (PWB) on a first side of the electronic assembly. The electronic assembly also includes a first reinforcing material fixed to the first PWB, a second PWB on a second side of the electronic assembly opposite the first side, a second reinforcing material fixed to the second PWB, and a central reinforcing material within the second reinforcing material and mounted between the first reinforcing material and the second reinforcing material. The central reinforcing material has a first side facing the first reinforcing material, a second side opposite the first side and facing the second reinforcing material, a first end, and a second end opposite the first end. An electronic device is fixed to the central reinforcing material. The central reinforcing material dissipates heat from the electronic device, and the electronic device includes a power die.

[0004] Additionally or alternatively, in this embodiment or other embodiments, the electronic assembly includes a wedge lock for securing a central reinforcement between a first reinforcement and a second reinforcement based on a compressive force, a first wedge lock attachment rail extending from a first end of the central reinforcement to support a first set of wedge locks, and a second wedge lock attachment rail extending from a second end of the central reinforcement to support a second set of wedge locks.

[0005] Additionally or alternatively, in this embodiment or other embodiments, the central reinforcement is on a first side and a second side, transferring heat from an electronic device closer to the first end of the central reinforcement to the first wedge lock attachment rail, and transferring heat from an electronic device closer to the second end of the central reinforcement to the second wedge lock attachment rail on the first side and the second side.

[0006] Additionally or alternatively, in this embodiment or other embodiments, the second reinforcement includes a wedge-shaped slot for accommodating the first and second ends of the central reinforcement.

[0007] Additionally or alternatively, in this embodiment or other embodiments, the electronic assembly also includes a ceramic plate fixed to the central reinforcement, and each ceramic plate is fixed to the first side or the second side and closer to the first end or the second end of the central reinforcement.

[0008] Additionally or alternatively, in this embodiment or other embodiments, the central reinforcement is copper, the ceramic plate is silicon nitride or aluminum nitride, and is fixed to the central reinforcement by direct bonding of copper (DBC) technology.

[0009] Additionally or alternatively, in this embodiment or other embodiments, the electronic assembly also includes a copper plate fixed to the ceramic plate. The electronic device is attached to the copper plate.

[0010] Further or alternatively, in this embodiment or other embodiments, the copper plate is fixed to the ceramic plate by DBC technology, and the electronic device is soldered to the copper plate.

[0011] Further or alternatively, in this embodiment or other embodiments, the electronic device includes a diode, the first gate drive PWB is on the first side of the central reinforcement, and the second gate drive PWB is on the second side of the central reinforcement.

[0012] Further or alternatively, in this embodiment or other embodiments, the electronic assembly also includes spring-type electrical contacts held by holders on the first and second sides of the central reinforcement. The spring-type electrical contacts carry current between the first PWB on the first side of the central reinforcement and the power die, and between the second PWB on the second side of the central reinforcement and the power die.

[0013] In another embodiment, a method of assembling an electronic assembly includes fixing a first printed wiring board (PWB) to a first side of the electronic assembly, fixing a first reinforcement to the first PWB, fixing a second PWB to a second side of the electronic assembly opposite the first side, fixing a second reinforcement to the second PWB, and placing a central reinforcement within the second reinforcement and between the first and second reinforcements. The central reinforcement has a first side facing the first reinforcement, a second side opposite the first side and facing the second reinforcement, a first end, and a second end opposite the first end. The electronic device is fixed to the central reinforcement. The central reinforcement dissipates heat from the electronic device, and the electronic device includes a power die.

[0014] Further or alternatively, in this embodiment or other embodiments, the method also includes configuring a wedge lock to fix the central reinforcement between the first and second reinforcements based on a compressive force. A first set of wedge locks is supported by a first wedge lock mounting rail extending from a first end of the central reinforcement, and a second set of wedge locks is supported by a second wedge lock mounting rail extending from a second end of the central reinforcement.

[0015] Furthermore or alternatively, in this embodiment or other embodiments, the method is on a first side and a second side, and transfers heat from an electronic device closer to a first end of the central reinforcement to a first wedge lock mounting rail, and on the first side and the second side, transfers heat from an electronic device closer to a second end of the central reinforcement to a second wedge lock mounting rail, and also includes configuring the central reinforcement.

[0016] Furthermore or alternatively, in this embodiment or other embodiments, the method also includes forming a wedge-shaped slot in a second reinforcement to accommodate a first end and a second end of the central reinforcement.

[0017] Furthermore or alternatively, in this embodiment or other embodiments, the method also includes fixing a ceramic plate to the central reinforcement, and each ceramic plate is fixed on a first side or a second side and closer to a first end or a second end of the central reinforcement.

[0018] Furthermore or alternatively, in this embodiment or other embodiments, the method also includes fabricating the central reinforcement from copper, fabricating the ceramic plate from silicon nitride or aluminum nitride, and fixing the ceramic plate to the central reinforcement by a direct bonding of copper (DBC) technique.

[0019] Furthermore or alternatively, in this embodiment or other embodiments, the method also includes fixing a copper plate to the ceramic plate and attaching an electronic device to the copper plate.

[0020] Furthermore or alternatively, in this embodiment or other embodiments, fixing a copper plate to the ceramic plate includes using the DBC technique, and attaching an electronic device includes soldering the electronic device to the copper plate.

[0021] Additionally or alternatively, in this embodiment or other embodiments, the method also includes including a first gate drive PWB on a first side of the central reinforcement member and including a second gate drive PWB on a second side of the central reinforcement member.

[0022] Additionally or alternatively, in this embodiment or other embodiments, the method also includes including spring-type electrical contacts held by holders on the first and second sides of the central reinforcement member, and the spring-type electrical contacts carry current between a first PWB on the first side of the central reinforcement member and the power die, and between a second PWB on the second side of the central reinforcement member and the power die.

Brief Description of the Drawings

[0023] The following description should not be regarded as limiting in any way. Regarding the accompanying drawings, like elements are numbered alike.

Figure 1A

Figure 1B

Figure 2

Figure 3A

Figure 3B

Figure 3C

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Figure 6C

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Figure 7B

DETAILED DESCRIPTION OF THE INVENTION

[0024] A detailed description of one or more embodiments of the disclosed apparatus and method is presented herein by way of example and not limitation with reference to the drawings.

[0025] As described above, an electronic device generates heat that could be dissipated by convective heat transfer if the device were installed such that it is exposed to an air flow. In certain applications such as deep space applications, for example, high power density electronic devices (e.g., power dies and diodes) as well as other components are arranged within an assembly such that convective heat transfer is not possible. The embodiments detailed herein relate to a thermal conduction management architecture for electronic devices. The electronic devices are power dies and diodes having a gate drive electronic circuit according to an exemplary embodiment. However, the conductive heat transfer facilitated by the architecture detailed herein is equally applicable to other electronic devices and modules that dissipate heat. Exemplary applications of these embodiments include deep space applications, underwater applications, and terrestrial applications.

[0026] FIG. 1A is an isometric view of an exemplary electronic assembly 100 that includes a thermal conduction management architecture according to one or more embodiments. A primary backplane connector 110a attached to a primary printed wiring board (PWB) 120a and a secondary backplane connector 110b attached to a secondary PWB 120b (generally referred to as backplane connectors 110 and PWBs 120) are shown. Between the two PWBs 120 are an outer reinforcement 210, a central reinforcement 230, and an additional reinforcement 130. The central reinforcement 230 promotes conductive heat transfer, as will be further described, for example, in connection with FIG. 5.

[0027] The outer reinforcement 210 and the additional reinforcement 130 may be aluminum reinforcements, while the central reinforcement 230 may be copper. Wedge locks 140 are shown at both ends of the electronic assembly 100, with openings 145 for wedge lock screws (not shown). These may be used when securing the electronic assembly 100, for example, to a rack. The wedge locks 140 are supported by wedge lock attachment rails 240 formed as part of the central reinforcement 230 and by wedge lock attachment edges 220 formed as part of the outer reinforcement 210. The wedge locks 140 may be aluminum, like the outer reinforcement 210 and the additional reinforcement 130. For the sake of explanation, the two PWBs 120 are said to be on opposite sides, while the wedge locks 140 are said to be at opposite ends.

[0028] FIG. 1B is a side view of an exemplary electronic assembly 100 including a heat conduction management architecture according to one or more embodiments. As described above, the wedge lock 140 facilitates installation of the electronic assembly 100 into the chassis within the electronic box. Specifically, wedge lock screws are inserted into the openings 145 of each wedge lock 140 and torque is applied. As a result of applying this torque, the wedge lock 140 receives both an axial force and a perpendicular resistance force (indicated by the arrow). The perpendicular resistance force, which is a compressive force, is transmitted to the central reinforcement 230 and the outer reinforcement 210 at the wedge lock mounting rail 240 and the wedge lock mounting edge 220. This compressive force ensures that the electronic assembly 100 is securely held in the slotted hole of the electronic box.

[0029] FIG. 2 is an exploded view of the central reinforcement 230 and the outer reinforcement 210 of the electronic assembly 100 according to one or more embodiments. The central reinforcement 230 has wedge lock mounting rails 240 on each side. The tray 250 is formed at both ends of the opening 260 as shown. Electronic components are disposed within the tray 250, for example, as shown in FIGS. 4 and 5. The inclined edge 245 of the central reinforcement 230 that fits into the wedge-shaped slotted hole 225 of the outer reinforcement 210 is shown. The outer reinforcement 210 with two wedge lock mounting edges 220 at each end is shown. At a given end, there are two wedge lock mounting edges 220 at both ends of the wedge lock mounting rail 240 of the central reinforcement 230. The inclined edge 227 forming the wedge-shaped slotted hole 225 is shown. The outer reinforcement 210 is formed as a frame having an opening 205 as shown.

[0030] Figures 3A, 3B, and 3C show different views of the central reinforcement 230 mounted on the outer reinforcement 210. Figure 3A is an isometric view of the central reinforcement 230 mounted on the outer reinforcement 210. Figure 3B is a top view of the central reinforcement 230 within the outer reinforcement 210, and Figure 3C is a side view. Although the opposite side of the central reinforcement 230 is not visible, the trays 250 for housing the electronic components are also on the opposite sides of both ends of the opening 260. These trays 250 on the opposite side of the central reinforcement 230 are mostly exposed due to the opening 205 of the outer reinforcement 210, but the frame of the outer reinforcement 210 intersects each tray 250.

[0031] As Figure 3B reveals, the wedge lock mounting rails 240 at both ends of the central reinforcement 230 fit between two wedge lock mounting edges 220 formed as part of the outer reinforcement 210. As shown in Figure 3C, the inclined edge 245 of the central reinforcement 230 aligns with the inclined edge 227 of the outer reinforcement 210. The central reinforcement 230 is not fixed or attached to the outer reinforcement 210. Instead, as described above, the central reinforcement 230 and the outer reinforcement 210 are firmly held within the complete electronic assembly 100 based on the wedge lock 140. Thus, easy access can be had to the components attached to the central reinforcement 230. For illustrative purposes, the mounting of the central reinforcement 230 within the outer reinforcement 210 is shown, but as shown in the rest of the figures, the central reinforcement 230 is actually mounted on the outer reinforcement 210 after the components are attached to the central reinforcement 230.

[0032] Figure 4 shows one side of the central reinforcement 230 having electronic components according to an exemplary embodiment. The gate drive PWB 410 is shown together with the power die 420 and the diode 440 fixed (e.g., soldered) to the copper plate 430. The gate drive PWB 410 may include, for example, a very small circuit and a transformer. The gate drive PWB 410 can provide a low-impedance drive signal to the power die 420 and can also be used for signal conditioning. Although the opposite side of the central reinforcement 230 is not visible, the electronic components are attached on both sides as more clearly illustrated in Figure 5.

[0033] FIG. 5A is a cross-sectional view taken along line A-A shown in FIG. 4. In FIG. 5B, a part of the cross-sectional view at one end is enlarged. As shown, the cross-section A-A passes through the opening 260 rather than between the openings 260. The cross-sectional view illustrates the gate drive PWB 410a on one side and the gate drive PWB 410b on the opposite side (generally referred to as the gate drive PWB 410). The cross-sectional view also illustrates that the power die 420 and the diode 440 are attached to the copper plate 430 separated from the central reinforcement 230 by the ceramic plate 450. The ceramic plate 450 may be, for example, silicon nitride or aluminum nitride. The bond wires 460 extend from the power die 420 and the diode 440 to the PWB 410. The power die 420, the diode 440, and the bond wires 460 are disposed in the trays 250 at both ends on both sides of the central reinforcement 230.

[0034] The enlarged view of FIG. 5B shows the conductive heat transfer generated from the power die 420 and the diode 440 through the central reinforcement 230 from both sides of the central reinforcement 230. As indicated by the arrows, the heat is ultimately transferred to the wedge lock mounting rail 240 that functions as a heat sink. The efficiency of this heat transfer benefits from the high thermal conductivity of the materials involved and the low interfacial thermal resistance of the interfacial surfaces involved. The thermal conductivity of the materials selected for the ceramic plate 450 (e.g., silicon nitride, aluminum nitride) and the central reinforcement 230 (e.g., copper) is high compared to other materials that could be used. Further, the copper plate 430 and the ceramic plate 450 that separate the heat source (i.e., the power die 420 and the diode 440) from the central reinforcement 230 are fabricated with a thickness indicated by the temperature requirements of the electronic assembly 100.

[0035] The interface between the heat source and the central reinforcement 230 includes a first interface between the heat source (i.e., the power die 420 and the diode 440) and the copper plate 430, a second interface between the copper plate 430 and the ceramic plate 450, and a third interface between the ceramic plate 450 and the central reinforcement 230. Since the heat source is soldered to the copper plate 430, the interfacial thermal resistance at the first interface (between these heat sources and the copper plate 430) is reduced. The copper plate 430 can be bonded to the ceramic plate 450 using direct copper bonding (DBC) technology. This reduces the interfacial thermal resistance at the second interface. The ceramic plate 450 can also be bonded to the central reinforcement 230 using DBC technology. Therefore, the interfacial thermal resistance at the third interface is also reduced.

[0036] By selecting materials and using bonding techniques between the materials to increase the thermal conductivity and reduce the interfacial thermal resistance, the heat dissipation from the heat source increases. As a result, the junction temperature of the electronic device, which is the heat source, is maintained below a predetermined maximum value. This heat dissipation ability based on the central reinforcement 230 facilitates the use of high-power devices (i.e., the power die 420 and the diode 440). Although one end of the central reinforcement 230 is enlarged, it should be clear that heat transfer to the wedge lock mounting rail 240 occurs at both ends of the central reinforcement 230.

[0037] Figures 6A, 6B, and 6C are different views of the result of adding spring-type electrical contacts 620 to the assemblies illustrated in Figures 4, 5A, and 5B, according to an exemplary embodiment. Figures 6A and 6B are isometric views of opposite sides, and Figure 6C is a top view. The slanted edges 245 in Figures 6A and 6B indicate that the opposite sides are illustrated by each figure. The spring-type electrical contacts 620 are held within holders 610. Two spring-type electrical contacts 620 are illustrated on the upper side of each tray 250 at each end on each side. That is, in an exemplary case, a total of eight holders 610 are used. The holders 610 are made from a high-performance insulator material. The spring-type electrical contacts 620 carry current between the primary PWB and the secondary PWB 120 and the drain and source terminals of the corresponding-side power die 420.

[0038] Figure 6C clarifies that each holder 610 basically encloses a set of power die 420 and diodes 440 attached to the copper plate 430 in a frame and holds the spring-type electrical contacts 620 that supply the set of power die 420. The ceramic plate 450 directly below the copper plate 430 associated with each set is visible between the sets. The number of power die 420 and diodes 440, as well as the number of holders 610 and spring-type electrical contacts 620, are not limited by the exemplary figures. The electronic assembly 100 can be adjusted and sized according to the number of devices required by a given design.

[0039] Figure 7A is a cross-sectional isometric view of an exemplary electronic assembly 100 according to one or more embodiments. An enlarged view of one end is illustrated in Figure 7B. The cross-sectional view is from end to end through the central reinforcement 230. Thus, one of the two wedge-lock attachment edges 220 at each end, and one of the slanted edges 245 at each end are not visible. The cross-sectional view illustrates the outer reinforcement 210 on one side of the central reinforcement 230. As described above, the components (e.g., ceramic plate 450, copper plate 430, power die 420, diodes 440, bond wires 460, holders 610, spring-type electrical contacts 620) are attached on both sides of the central reinforcement 230, and then the central reinforcement 230 is installed within the outer reinforcement 210. The additional reinforcement 130 is then added, followed by the PWB 120 and the backplane connector 110.

[0040] The outer reinforcement 210 is fixed to one of the PWBs 120 (e.g., the secondary PWB 120b according to the figures of Figures 1A and 1B), and the additional reinforcement is fixed to the other PWB 120 (e.g., the primary PWB 120a according to the figures of Figures 1A and 1B). The central reinforcement 230 facilitates heat transfer from the electronic components attached on both sides to the wedge-lock attachment rails 240 at both ends. As illustrated in Figures 7A and 7B, the central reinforcement 230 is between the outer reinforcement 210 and the additional reinforcement 130.

[0041] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. Further, the terms "comprises" and / or "comprising", when used herein, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0042] The present disclosure has been described with reference to exemplary embodiments or embodiments, but it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for its elements without departing from the scope of the present disclosure. Further, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from its essential scope. Therefore, the present disclosure is not limited to the particular embodiments disclosed as the best mode contemplated for carrying out the present disclosure, but the present disclosure is intended to cover all embodiments falling within the scope of the "claims".

Claims

**Claim 1** An electronic assembly, a first printed wiring board (PWB) on a first side of the electronic assembly, a first reinforcing material fixed to the first PWB, a second PWB on a second side of the electronic assembly, opposite the first side, a second reinforcing material fixed to the second PWB, a central reinforcing material within the second reinforcing material and mounted between the first reinforcing material and the second reinforcing material, the central reinforcing material having a first side facing the first reinforcing material, a second side opposite the first side, a second side facing the second reinforcing material, a first end, and a second end opposite the first end, an electronic device fixed to the central reinforcing material, the central reinforcing material dissipating heat from the electronic device, the electronic device including a power die, a wedge lock configured to fix the central reinforcing material between the first reinforcing material and the second reinforcing material based on a compressive force, a first wedge lock mounting rail extending from the first end of the central reinforcing material configured to support a first set of the wedge locks, and a second wedge lock mounting rail extending from the second end of the central reinforcing material configured to support a second set of the wedge locks, the electronic assembly. **Claim 2** The electronic assembly according to claim 1, wherein the central reinforcing material is on the first side and the second side and is configured to transfer heat from the electronic device closer to the first end of the central reinforcing material to the first wedge lock mounting rail, and is on the first side and the second side and is configured to transfer heat from the electronic device closer to the second end of the central reinforcing material to the second wedge lock mounting rail. **Claim 3** The electronic assembly according to claim 1, wherein the second reinforcing material includes a wedge-shaped elongated hole configured to accommodate the first end and the second end of the central reinforcing material. **Claim 4** The electronic assembly according to claim 1, further comprising a ceramic plate fixed to the central reinforcing material, each ceramic plate being fixed closer to the first side or the second side and to the first end or the second end of the central reinforcing material. **Claim 5** The electronic assembly according to claim 4, wherein the central reinforcing member is copper, the ceramic plate is silicon nitride or aluminum nitride, and is fixed to the central reinforcing member by a direct bonding (DBC) technique of copper.

6. The electronic assembly according to claim 5, further comprising a copper plate fixed to the ceramic plate, wherein the electronic device is attached to the copper plate.

7. The electronic assembly according to claim 6, wherein the copper plate is fixed to the ceramic plate by the DBC technique, and the electronic device is soldered to the copper plate.

8. The electronic assembly according to claim 1, wherein the electronic device includes a diode, a first gate drive PWB is on the first side of the central reinforcing member, and a second gate drive PWB is on the second side of the central reinforcing member.

9. The electronic assembly according to claim 8, further comprising spring-type electrical contacts held in holders on the first side and the second side of the central reinforcing member, the spring-type electrical contacts being between the first PWB on the first side of the central reinforcing member and the power die, and between the second PWB on the second side of the central reinforcing member and the power die to carry current.

10. A method of assembling an electronic assembly, comprising: fixing a first printed wiring board (PWB) to a first side of the electronic assembly; fixing a first reinforcing member to the first PWB; fixing a second PWB to a second side of the electronic assembly, which is opposite to the first side; fixing a second reinforcing member to the second PWB; placing a central reinforcing member within the second reinforcing member and between the first reinforcing member and the second reinforcing member, the central reinforcing member having a first side facing the first reinforcing member, a second side opposite to the first side, a second side facing the second reinforcing member, a first end, and a second end opposite to the first end; fixing an electronic device to the central reinforcing member, the central reinforcing member dissipating heat from the electronic device, the electronic device including a power die.

11. Further comprising configuring a wedge lock to fix the central reinforcing member between the first reinforcing member and the second reinforcing member based on a compressive force, wherein a first set of the wedge locks is supported by a first wedge lock mounting rail extending from the first end of the central reinforcing member, and a second set of the wedge locks is supported by a second wedge lock mounting rail extending from the second end of the central reinforcing member. The method according to claim 10.

12. The method according to claim 11, further comprising configuring the central reinforcing member to transfer heat from the electronic device closer to the first end of the central reinforcing member to the first wedge lock mounting rail on the first side and the second side, and to transfer heat from the electronic device closer to the second end of the central reinforcing member to the second wedge lock mounting rail on the first side and the second side.

13. The method according to claim 10, further comprising forming a wedge-shaped slot in the second reinforcing member to receive the first end and the second end of the central reinforcing member.

14. The method according to claim 10, further comprising fixing a ceramic plate to the central reinforcing member, each ceramic plate being fixed closer to the first side or the second side and the first end or the second end of the central reinforcing member.

15. The method according to claim 14, further comprising fabricating the central reinforcing member from copper, fabricating the ceramic plate from silicon nitride or aluminum nitride, and fixing the ceramic plate to the central reinforcing member by a direct bonding of copper (DBC) technique.

16. The method according to claim 15, further comprising fixing a copper plate to the ceramic plate and attaching the electronic device to the copper plate.

17. The method according to claim 16, wherein fixing the copper plate to the ceramic plate includes using the DBC technique, and attaching the electronic device includes soldering the electronic device to the copper plate.

18. The method according to claim 10, further comprising including a first gate drive PWB on the first side of the central reinforcing member and a second gate drive PWB on the second side of the central reinforcing member.

19. The method according to claim 18, further comprising including spring-type electrical contacts held within holders on the first side and the second side of the central reinforcing member, wherein the spring-type electrical contacts carry current between the first PWB on the first side of the central reinforcing member and the power die, and between the second PWB on the second side of the central reinforcing member and the power die.

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