Multi-layer composite board

Abstract

This utility model relates to the field of composite panels, and discloses a multilayer composite panel, including a central metal layer, a pair of metal transition layers symmetrically bonded to the two side surfaces in the thickness direction of the central metal layer, and a pair of external metal layers respectively bonded to the outer surfaces in the thickness direction of the pair of metal transition layers; wherein, the coefficient of thermal expansion of the metal transition layers is greater than that of the external metal layers and less than that of the central metal layer. The multilayer composite panel of this utility model, by setting metal layers with intermediate transition coefficients of thermal expansion, achieves a smooth gradient transition of the coefficients of thermal expansion from the center to the outer surface, thereby effectively alleviating interlayer thermal stress, improving the long-term reliability of the bonding interface under thermal cycling, and also possessing good thermal conductivity, electrical conductivity, and structural stability.

Description

Technical Field

[0001] This utility model relates to the field of composite panels, and in particular to a multi-layer composite panel. Background Technology

[0002] Cu-Al-Cu sandwich structure composite plates, which combine the excellent electrical and thermal conductivity of copper with the lightweight and low-cost advantages of aluminum, are widely used. However, copper and aluminum have significant differences in physical properties, especially in their coefficients of thermal expansion, which differ by about 40%. Under conditions of drastic temperature changes, this difference can generate huge thermal stress at the interface. Long-term cycling can easily lead to interface fatigue, cracking, or even delamination, seriously affecting the reliability and service life of the device. Summary of the Invention

[0003] Therefore, in order to overcome the defects of copper-aluminum composite plates in the prior art, which are prone to fatigue and delamination due to the large difference in thermal expansion coefficients, this utility model provides a multilayer composite plate. By setting a metal layer with a centrally transitioning thermal expansion coefficient, a gradual transition of the thermal expansion coefficient from the center to the outer surface is achieved, thereby effectively alleviating interlayer thermal stress, improving the long-term reliability of the bonding interface under thermal cycling, and also having good thermal conductivity, electrical conductivity and structural stability.

[0004] To solve the above-mentioned technical problems, this utility model provides a multilayer composite board, comprising: Central metal layer; A pair of metal transition layers, symmetrically bonded to both sides of the central metal layer in the thickness direction; A pair of external metal layers are respectively bonded to the outer surface of the pair of metal transition layers in the thickness direction; The coefficient of thermal expansion of the metal transition layer is greater than that of the outer metal layer and less than that of the central metal layer.

[0005] Preferably, the central metal layer is an aluminum layer, the outer metal layer is a copper layer, and the metal transition layer is an aluminum-silicon alloy layer.

[0006] Preferably, the central metal layer is provided with an array of through holes, which extend along the thickness direction of the central metal layer; a heat-conducting pillar is inserted through the through hole, and the two ends of the heat-conducting pillar are respectively bonded to the pair of metal transition layers.

[0007] Preferably, the heat-conducting column extends in a wavy or spiral shape along the extension direction of the through hole, and the hole shape of the through hole is adapted to the heat-conducting column.

[0008] Preferably, the heat-conducting column is a hollow column.

[0009] Preferably, the central metal layer has at least one closed cavity that extends in a plane perpendicular to the thickness direction.

[0010] Preferably, the metal transition layer is discontinuously distributed in a direction parallel to the bonding surface, forming multiple transition blocks that are separated from each other.

[0011] Preferably, the metal transition layer has multiple heat-conducting sheets embedded inside, and the two ends of the heat-conducting sheets are in contact with the central metal layer and the outer metal layer, respectively.

[0012] Preferably, the plurality of heat-conducting sheets are arranged in layers along the thickness direction; the heat-conducting sheets in the same layer are parallel to each other, and the extension directions of adjacent heat-conducting sheets intersect.

[0013] Preferably, the outer surface of the outer metal layer is provided with heat dissipation fin units.

[0014] Compared with the prior art, the above-mentioned technical solution of this utility model has the following beneficial effects: The multilayer composite plate of this invention introduces a pair of metal transition layers with thermal expansion coefficients between the central metal layer and the outer metal layer. The thermal expansion coefficient changes gradient from the center to the outside along the thickness direction, reducing the interfacial shear stress caused by the abrupt change in the thermal expansion of each layer of material. This allows the thermal stress to be released and dispersed step by step between multiple interfaces, thereby suppressing fatigue damage and delamination tendency of the interface under temperature cyclic loading from the root.

[0015] Meanwhile, the symmetrical layered structure helps maintain the overall dimensional stability and flatness of the composite board, reducing warping deformation caused by asymmetric thermal expansion.

[0016] In addition, while achieving stress relief, the structure does not sacrifice the inherent advantages of each functional layer: the central layer can still use high-rigidity or specific functional materials to provide core support, and the outer metal layer can ensure excellent surface conductivity, thermal conductivity and solderability. Attached Figure Description

[0017] To make the content of this utility model easier to understand, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1 This is a schematic diagram of the layer structure of the multilayer composite plate in a preferred embodiment of the present invention; Figure 2 for Figure 1 A schematic cross-sectional view of the central metal layer of the multilayer composite plate shown. Figure 3 This is a schematic diagram of the layer structure of a multilayer composite board in another embodiment of the present invention.

[0018] Explanation of reference numerals in the accompanying drawings: 10-Central metal layer, 11-Through hole, 12-Heat-conducting pillar, 13-Cavity; Metal transition layer, 21-transition block; 30 - External metal layer. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments are not intended to limit the present invention.

[0020] In traditional Cu-Al-Cu sandwich composite plates, the coefficients of thermal expansion of copper and aluminum are approximately 17 ppm / K and 23 ppm / K, respectively. The significant difference in their thermal expansion coefficients leads to different expansion and contraction rates during temperature cycling, generating substantial alternating thermal stress at the interface. Prolonged exposure to this stress can easily cause fatigue damage at the interface, resulting in microcracks and ultimately delamination. This disrupts the electrical and thermal conductivity paths of the composite plate, reducing its structural strength. The purpose of this utility model embodiment is to overcome the defects of the copper-aluminum composite plate in the prior art, which is prone to fatigue and delamination due to the large difference in the coefficient of thermal expansion.

[0021] Reference Figure 1 As shown in the figure, this utility model discloses a multilayer composite board, including a central metal layer 10, a pair of metal transition layers 20 and a pair of external metal layers 30. The pair of metal transition layers 20 are symmetrically bonded to both sides of the central metal layer 10 in the thickness direction; the pair of external metal layers 30 are respectively bonded to the outer surfaces of the pair of metal transition layers 20 in the thickness direction; wherein, the coefficient of thermal expansion of the metal transition layer 20 is greater than that of the central metal layer 10 and less than that of the external metal layer 30.

[0022] Specifically, in one embodiment, the central metal layer is made of pure aluminum of grade 1060 or aluminum alloy of grade 6061, with a coefficient of thermal expansion of approximately 23.6 ppm / K; the transition metal layer is made of aluminum-silicon alloy of grade A4047, with a silicon content of approximately 12% and a coefficient of thermal expansion of approximately 21.5 ppm / K; and the outer metal layer is made of pure copper of grade C11000, with a coefficient of thermal expansion of approximately 17 ppm / K. This constructs a two-step stepped thermal expansion transition from aluminum to copper. As the temperature rises, the central aluminum layer expands the most, while the intermediate aluminum-silicon alloy transition layer expands in the middle, absorbing approximately half of the expansion difference between the central aluminum layer and the outer copper layer. This decomposes the originally large aluminum-copper interface stress into two much smaller interface stresses: aluminum-aluminum-silicon and aluminum-silicon-copper. This stress decomposition and graded release effectively suppresses stress concentration at a single interface. Meanwhile, since aluminum-silicon alloys are chemically compatible with aluminum and copper on both sides, they are more likely to form a strong metallurgical bond through processes such as rolling and hot pressing, further ensuring the long-term stability of the transition interface.

[0023] Composite panels primarily rely on the lateral thermal conductivity of the layered materials themselves and limited interfacial contact for vertical heat dissipation, resulting in high Z-axis thermal resistance. To address the high Z-axis thermal resistance of composite panels, based on the aforementioned embodiments, and referring to... Figure 2 As shown, the central metal layer 10 of this embodiment has an array of through holes 11, which extend along the thickness direction of the central metal layer 10. Heat-conducting pillars 12 are inserted through the through holes 11, with each end of the pillar connected to a pair of metal transition layers 20. The heat-conducting pillars 12 serve as independent, continuous heat conduction pathways, directly penetrating the thickness direction of the central metal layer 10 and connecting their ends to the upper and lower metal transition layers 20. When heat is introduced from the surface of the outer metal layer 30, in addition to the traditional interlayer diffusion path, it can also be directly transferred to the other side through the heat-conducting pillars 12, passing through the central layer. This reduces the overall thermal resistance in the thickness direction, achieving three-dimensional heat conduction. Furthermore, the heat-conducting pillars 12 also form structural pins, mechanically locking the central metal layer 10 and the two transition layers 20 together. This partially transforms the two-dimensional shear stress on the original planar interface into compressive stress and radial binding stress on the heat-conducting pillars 12, thereby improving the interlayer shear resistance and overall structural rigidity, and preventing interface slippage or delamination under thermo-mechanical coupling loads.

[0024] Furthermore, in one embodiment, the heat-conducting pillar 12 extends in a wavy or spiral shape along the direction of the through-hole, and the shape of the through-hole 11 is adapted to the heat-conducting pillar 12. When the heat-conducting pillar 12 is wavy or spiral, its effective surface area is significantly increased compared to a straight pillar of the same diameter. This directly means a substantial increase in the heat exchange area with the hole wall of the central metal layer 10, thereby more efficiently conducting heat from the hole wall to the pillar, or vice versa. More importantly, the wavy or spiral shape forms a continuously changing curved surface contact and a tortuous mechanical path in three-dimensional space. This shape prevents the heat-conducting pillar 12 from sliding or rotating axially within the hole, improving the shear resistance and peel resistance of the bonding interface.

[0025] In another embodiment, the heat-conducting column 12 is a hollow column. The cavity inside the hollow column can form a stress buffer cavity. When the composite plate experiences temperature changes, the cavity can accommodate the small deformation of the column material caused by thermal expansion and contraction, or in extreme cases, allow the column to undergo small elastic buckling, thereby releasing a portion of the internal stress in a controllable manner and avoiding excessive stress concentration at the column-hole interface.

[0026] In other embodiments, the central metal layer 10 contains at least one closed cavity 13, which extends in a plane perpendicular to the thickness direction. That is, the cavity 13 extends parallel to the plate surface, forming an internal, flat, sealed space that is not connected to the outside. When the composite plate expands or contracts due to temperature differences, the material tends to undergo minor elastic or plastic flow in the low-stiffness region where the cavity 13 is located, thereby actively attracting and accommodating some strain. This transforms the shear stress that might otherwise lead to interface debonding into uniform compressive or tensile stress on the wall of the cavity 13. Simultaneously, when subjected to external impact, the cavity 13 can cause stress wave reflection and interference, consuming some of the impact energy.

[0027] In other embodiments, refer to Figure 3 As shown, the metal transition layer 20 is discontinuously distributed in a direction parallel to the bonding surface, forming multiple separate transition blocks 21. Each transition block 21 is independently bonded to the upper and lower layers, responsible for the expansion coordination and stress transfer of its local area; in the gap region between these blocks, the central metal layer 10 and the outer metal layer 30 are directly facing each other to a certain extent, and their thermal expansion difference is no longer rigidly constrained by the transition layer material. Multiple separate transition blocks 21 form multiple stress interruption points on the thermal stress transfer path. When the whole undergoes thermal deformation, the stress cannot accumulate and transfer continuously and uniformly on the interface, but is confined to a small range within and around each independent transition block 21. The gap between the blocks provides strain accommodation space for the differential expansion of adjacent materials, allowing the materials to undergo small relative displacements.

[0028] In other embodiments, the metal transition layer 20 has multiple heat-conducting sheets embedded within it, with both ends of the heat-conducting sheets contacting the central metal layer 10 and the outer metal layer 30, respectively. The heat-conducting sheets improve the efficiency of heat passing through the metal transition layer 20, further enhancing the vertical heat dissipation capability of the composite board.

[0029] Furthermore, multiple heat-conducting sheets are arranged in layers along the thickness direction; the heat-conducting sheets within the same layer are parallel to each other, and the extension directions of adjacent heat-conducting sheets intersect. This design forms a three-dimensional heat-conducting network, further improving the heat diffusion efficiency within the metal transition layer 20. In addition, this design effectively suppresses complex shear deformation caused by uneven thermal expansion in different directions or external loads, enhancing the overall dimensional stability and torsional resistance of the composite plate.

[0030] In the aforementioned scheme, even though the composite plate achieves excellent internal heat conduction through a multi-layered gradient structure and vertical heat-conducting columns, if the heat cannot be efficiently dissipated from its outer surface to the environment, heat accumulation and overall temperature rise will still occur, limiting the full utilization of its heat dissipation performance. To solve this problem, in the embodiment of the present invention, the outer surface of the outer metal layer 30 is provided with heat dissipation fin units, which expands the effective surface area for heat exchange between the composite plate and the external cooling medium.

[0031] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. A multi-layer composite board, characterized in that, include: Central metal layer; A pair of metal transition layers, symmetrically bonded to both sides of the central metal layer in the thickness direction; A pair of external metal layers are respectively bonded to the outer surface of the pair of metal transition layers in the thickness direction; The coefficient of thermal expansion of the metal transition layer is greater than that of the outer metal layer and less than that of the central metal layer.

2. The multilayer composite board according to claim 1, characterized in that, The central metal layer is an aluminum layer, the outer metal layer is a copper layer, and the metal transition layer is an aluminum-silicon alloy layer.

3. The multilayer composite board according to claim 1 or 2, characterized in that, The central metal layer has an array of through holes that extend along the thickness direction of the central metal layer; a heat-conducting pillar is inserted through the through hole, and the two ends of the heat-conducting pillar are respectively bonded to the pair of metal transition layers.

4. The multilayer composite board according to claim 3, characterized in that, The heat-conducting pillar extends in a wavy or spiral shape along the direction of the through hole, and the hole shape of the through hole is adapted to the heat-conducting pillar.

5. The multilayer composite board according to claim 3, characterized in that, The heat-conducting column is a hollow column.

6. The multilayer composite board according to claim 1 or 2, characterized in that, The central metal layer has at least one closed cavity that extends in a plane perpendicular to the thickness direction.

7. The multilayer composite board according to claim 1 or 2, characterized in that, The metal transition layer is discontinuously distributed in a direction parallel to the bonding surface, forming multiple transition blocks that are separated from each other.

8. The multilayer composite board according to claim 7, characterized in that, The metal transition layer has multiple heat-conducting sheets embedded inside, and the two ends of the heat-conducting sheets are in contact with the central metal layer and the outer metal layer, respectively.

9. The multilayer composite board according to claim 8, characterized in that, The plurality of heat-conducting sheets are arranged in layers along the thickness direction; the heat-conducting sheets in the same layer are parallel to each other, and the extension directions of adjacent heat-conducting sheets intersect.

10. The multilayer composite board according to claim 1, characterized in that, The outer surface of the external metal layer is provided with heat dissipation fin units.

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