Thermal Conductive Substrate

Abstract

A heat-conducting substrate includes a metal bottom plate, a metal layer, a heat-conducting insulating polymer layer, and a ceramic material layer. The heat-conducting insulating polymer layer is located between the metal layer and the metal bottom plate. The ceramic material layer includes an upper ceramic layer or a lower ceramic layer, or includes both the upper ceramic layer and the lower ceramic layer at the same time. The upper ceramic layer is disposed between the metal layer and the heat-conducting insulating polymer layer, and the lower ceramic layer is disposed between the heat-conducting insulating polymer layer and the metal bottom plate.

Description

Technical Field

[0001] The present invention relates to a heat-conducting substrate, in particular to a heat-conducting substrate having the advantages of suppressing a sharp drop in volume resistivity at high temperatures and being applicable to thick copper applications. Background Art

[0002] Generally, a circuit board is fabricated by bonding electronic components such as IC chips to a heat-dissipating substrate, where the heat generated by the electronic components and accumulated thereon can be conducted to the outside through the heat-dissipating substrate. Commonly used heat-dissipating substrates include metal core printed circuit boards (MCPCBs) and directly bonded copper (DBC) ceramic substrates.

[0003] Although DBC ceramic substrates have the advantage of high temperature resistance, the ceramic is expensive, and due to its hard and brittle material properties, it is difficult to perform mechanical processing such as drilling and cutting during the fabrication of heat-dissipating substrates. Moreover, due to the large difference in the coefficient of thermal expansion between the copper foil and the ceramic layer, in thick copper applications of 0.3 mm to 10 mm, delamination problems are particularly likely to occur between the copper foil and the ceramic layer at high temperatures.

[0004] MCPCB uses a polymer as the main material of the heat-conducting insulating layer, and a heat-conducting filler is further mixed in the heat-conducting insulating layer. Metal foils are provided on the upper and lower surfaces of the heat-conducting insulating layer respectively to form a heat-dissipating substrate having a laminated structure. The polymer is much cheaper than ceramic materials. In addition, due to the inherent material properties of the polymer, it is easy to perform mechanical processing during the fabrication of the heat-dissipating substrate, and there is also a preferable adhesion between the heat-conducting insulating layer and the metal foil. Therefore, MCPCB plays a crucial role in the heat-dissipating substrate product market.

[0005] However, when the MCPCB is powered on, the electronic components gradually generate heat, causing the temperature of the heat-dissipating substrate to reach 100°C to 250°C, and an electric field is also formed between the metal foils on both sides of the heat-conducting insulating layer. Under normal circumstances, the polymer is an electrical insulator; however, under the influence of an applied electric field, the polymer will generate electric dipoles on it due to the polarization effect of the electric field, that is, the so-called electric polarization. Therefore, the polymer will have the polar groups on the polymer chain start to be arranged in a direction, and this directional arrangement makes the polymer have a small conductive ability. At low temperatures, the rotation of the electric dipole moment cannot keep up with the change of the electric field, and the conductive performance is not significant; however, as the temperature rises, the polymer is easy to move at high temperatures, and the electric dipole moment can follow the change of the electric field and turn, so the conductive performance of the polymer increases or the electrical insulation performance decreases. These factors cause the volume resistivity of the heat-conducting insulating layer at high temperatures to drop significantly compared to the volume resistivity at room temperature. For example, the ratio of the volume resistivity at 175°C to the volume resistivity at 25°C is at least less than 10.-6 。

[0006] In addition, MCPCBs have always had the problem of metal ion (such as copper ion) migration. The so-called ion migration refers to the ionization of metals such as copper and silver on the circuit board under high temperature and high humidity conditions and their migration through the insulating layer to another electrode under the action of an electric field, resulting in a decrease in insulation performance. The reason for ion migration is that after the heat dissipation substrate is energized, an electric field is formed between the metal foils on both sides of the thermally conductive insulating layer (or between two adjacent metal lines). These two sides of the metal become two electrodes, and the metal on the anode side is ionized and migrates through the thermally conductive insulating layer to the metal on the other side (cathode) under the action of the electric field. As a result, the thermally conductive insulating layer is in an ion-conductive state. Obviously, this will reduce the insulation performance of the thermally conductive insulating layer or even turn it into a conductor, causing a short circuit fault. During the high temperature and high humidity biased test (HHBT) of the product, copper ions may migrate from the copper foil, reducing the insulation of the thermally conductive insulating layer and affecting the withstand voltage characteristics accordingly.

[0007] Obviously, traditional Metal Core PCBs (MCPCBs) have many problems and urgently need to be further improved. Summary of the Invention

[0008] The present invention discloses a heat dissipation substrate, in which the withstand voltage value is improved by providing a ceramic material layer. In addition, by appropriately controlling the ratio between the roughness of the metal layer and the metal bottom plate and the thickness of the ceramic material layer, the bonding strength between layers can be increased, which is particularly suitable for use in thick copper applications. The heat dissipation substrate of the present invention also has good heat dissipation effects.

[0009] The present invention discloses a heat dissipation substrate, which includes a metal bottom plate, a metal layer, a thermally conductive insulating polymer layer, and a ceramic material layer. The thermally conductive insulating polymer layer is located between the metal layer and the metal bottom plate. The ceramic material layer includes an upper ceramic layer or a lower ceramic layer, or both the upper ceramic layer and the lower ceramic layer. The upper ceramic layer is provided between the metal layer and the thermally conductive insulating polymer layer, and the lower ceramic layer is provided between the thermally conductive insulating polymer layer and the metal bottom plate.

[0010] In one embodiment, the volume resistivity of the heat dissipation substrate at 175 °C is at least 10 9 Ω·cm.

[0011] In one embodiment, the ratio between the volume resistivity of the heat dissipation substrate at 175 °C and the volume resistivity at 25 °C is defined as the retention rate, and the retention rate is at least 10 -4 。

[0012] In one embodiment, the upper ceramic layer forms a physical contact with the metal layer, and the lower ceramic layer forms a physical contact with the metal base plate.

[0013] In one embodiment, the thickness of the upper ceramic layer and the lower ceramic layer is 3 μm to 100 μm.

[0014] In one embodiment, the total thickness of the upper ceramic layer and the lower ceramic layer added together is 5 μm to 200 μm.

[0015] In one embodiment, the upper ceramic layer and the lower ceramic layer are a single material layer, or a multi-layer composite material layer composed of multiple sub-layers, and the material of the single material layer and the multiple sub-layers is alumina, zirconia, magnesia or titanium oxide.

[0016] In one embodiment, the thickness of the metal layer and the metal base plate is 0.3 mm to 10 mm.

[0017] In one embodiment, the lower surface of the metal layer has a roughness Rz, and the upper surface of the metal base plate has the roughness Rz, and the roughness Rz is 2 μm to 80 μm.

[0018] In one embodiment, the value of the roughness Rz divided by the thickness of the upper ceramic layer or the lower ceramic layer is 0.2 to 0.8.

[0019] In one embodiment, when the heat-conducting substrate is subjected to a DC withstand voltage HHBT test at a temperature of 85 °C and a relative humidity of 85% R.H. for 1000 hours, the withstand voltage value is at least DC1000V.

[0020] In one embodiment, the thermal resistance of the heat-conducting substrate is less than 0.16 °C / W.

[0021] In the heat-conducting substrate of the present invention, a ceramic material layer is provided, which has the technical effect of suppressing the sudden drop of the volume resistivity at high temperatures. In addition, roughening the surface of the metal layer or the metal base plate can increase the bonding strength between layers, thereby providing a solution that the existing DBC ceramic substrate cannot be used for thick copper applications. Setting the ceramic material layer also enables the heat-conducting substrate to have a good heat dissipation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic cross-sectional view showing the heat-conducting substrate of the first embodiment of the present invention.

[0023] Figure 2 Schematic cross-sectional view showing the heat-conducting substrate of the second embodiment of the present invention.

[0024] Figure 3 Schematic cross-sectional view showing the heat-conducting substrate of the third embodiment of the present invention.

[0025] Figure 4Shows a schematic cross-sectional view of the heat-conducting substrate according to the fourth embodiment of the present invention.

[0026] Description of reference numerals:

[0027] 11 Metal bottom plate

[0028] 12 Heat-conducting insulating polymer layer

[0029] 13, 131, 132 Ceramic material layer

[0030] 14 Metal layer

[0031] 16, 17 Micro-rough surface

[0032] 100, 200, 300 Heat-conducting substrate Detailed implementation manners

[0033] To make the above and other technical contents, features and advantages of the present invention more obvious and understandable, the following specific embodiments are hereby given, and in conjunction with the accompanying drawings of the specification, the detailed description is as follows.

[0034] Refer to Figure 1 , Figure 1 , which shows the heat-conducting substrate 100 according to the first embodiment of the present invention. The heat-conducting substrate 100 includes a metal bottom plate 11, a heat-conducting insulating polymer layer 12, a ceramic material layer 13 and a metal layer 14. The heat-conducting insulating polymer layer 12 is disposed on the metal bottom plate 11 and is located between the metal layer 14 and the metal bottom plate 11. In this embodiment, the ceramic material layer 13 is used as an upper ceramic layer in the heat-conducting substrate, and the ceramic material layer (upper ceramic layer) 13 is disposed between the metal layer 14 and the heat-conducting insulating polymer layer 12. In one embodiment, the material of the metal layer 14 can be copper, and the material of the metal bottom plate 11 can be copper, aluminum, or copper / aluminum alloy. In this embodiment, the ceramic material layer (upper ceramic layer) 13 forms physical contact with the metal layer 14. Preferably, as shown in Figure 4 , the interface between the ceramic material layer (upper ceramic layer) 13 and the metal layer 14 may include a micro-rough surface 16. Similarly, the interface between the metal bottom plate 11 and the heat-conducting insulating polymer layer 12 may also include another micro-rough surface 17. The micro-rough surfaces 16, 17 can increase the bonding strength between the metal layer 14, the ceramic material layer (upper ceramic layer) 13, the heat-conducting insulating polymer layer 12 and the metal bottom plate 11. In one embodiment, the surface roughening of the metal layer 14 and the metal bottom plate 11 can be achieved by wet etching or mechanical grinding.

[0035] As described above, roughening can improve the bonding strength between layers, thereby avoiding the delamination problem caused by the large difference in the coefficient of thermal expansion between the metal layer and the ceramic material layer. Further, due to the increased bonding strength, it is not easy to generate gaps between layers, and the gaps will form an interfacial thermal resistance. Therefore, roughening can also enable the heat-conducting substrate to have a preferred heat-conducting path and thus reduce the thermal resistance value of the heat-conducting substrate. In addition, the undulating and inclined surface after roughening will increase the path length of the interface between layers, so that the possibility of water vapor infiltrating into the heat-conducting substrate from the side can be reduced, which helps to improve the breakdown voltage of the heat-conducting substrate in a high-temperature and high-humidity environment.

[0036] The roughness of the lower surface of the metal layer and the roughness of the upper surface of the metal bottom plate should be within an appropriate numerical range, neither too large nor too small. Too large a roughness will cause a tip discharge problem between the roughened surfaces of the metal layer and the metal bottom plate, resulting in insufficient breakdown voltage and being difficult to process; too small a roughness will not achieve the above technical effects. In one embodiment, the lower surface of the metal layer has a roughness Rz, and the upper surface of the metal bottom plate has the roughness Rz. The roughness Rz is 2 μm to 80 μm, such as 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm or 70 μm. It can be controlled that the value of the roughness Rz divided by the thickness of the ceramic material layer (upper ceramic layer) is 0.2 to 0.8, such as 0.3, 0.4, 0.5, 0.6 or 0.7, which can enable the heat-conducting substrate to have good bonding strength between layers, sufficient breakdown voltage, and easy roughening for processing.

[0037] The thermally conductive insulating polymer layer 12 includes a polymer and thermally conductive fillers dispersed in the polymer. In one embodiment, the polymer can include a thermoplastic resin, a thermosetting resin, or a combination thereof. The thermally conductive fillers can be selected from an oxide or a nitride. The oxide can use alumina, magnesia, zinc oxide, or titanium dioxide, and the nitride can use zirconium nitride, boron nitride, aluminum nitride, or silicon nitride.

[0038] The ceramic material layer (upper ceramic layer) 13 is a single material layer, and its material can be alumina, zirconia, magnesia, or titanium dioxide or other ceramic materials. Alternatively, the ceramic material layer (upper ceramic layer) 13 can be a multi-layer composite layer composed of multiple sub-layers, and the materials of the multiple sub-layers can also be alumina, zirconia, magnesia, or titanium dioxide or other ceramic materials. Different ceramic materials have their own different special properties. Therefore, according to the product requirements, the ceramic material layer (upper ceramic layer) 13 can be designed into a single material layer or a multi-layer composite layer structure composed of multiple sub-layers to meet the characteristic requirements.

[0039] According to the present invention, only the metal layer 14 and the metal base plate 11 have conductive properties. Therefore, the thermally conductive insulating layer of the thermally conductive substrate 100 can be regarded as including both the thermally conductive insulating polymer layer 12 and the ceramic material layer (upper ceramic layer) 13. It should be noted that ceramic materials can withstand high temperatures, and the volume resistivity of ceramic materials at high temperatures does not change significantly compared to room temperature. Through the structural design of the present invention, although the volume resistivity of the thermally conductive insulating polymer layer 12 decreases significantly at high temperatures of 100°C to 250°C compared to the volume resistivity at 25°C room temperature, since the volume resistivity of the ceramic material does not decrease significantly at high temperatures of 100°C to 250°C compared to 25°C room temperature, the overall volume resistivity of the thermally conductive insulating layer of the thermally conductive substrate 100 does not decrease significantly, solving the problem that the volume resistivity drops suddenly at high temperatures when only using the thermally conductive insulating polymer layer as the thermally conductive insulating layer in the traditional structural design. In addition, the ceramic material layer (upper ceramic layer) 13 is disposed between the metal layer 14 and the thermally conductive insulating polymer layer 12, and the ceramic material layer (upper ceramic layer) 13 can prevent the metal ions on the lower surface of the metal layer 14 from migrating downward, overcoming the problem of metal ion migration. Furthermore, since the thermal conductivity of ceramic materials is very high, for example, the thermal conductivities of alumina, magnesia, and titanium oxide are 32 W / m·K, 36 W / m·K, and 22 W / m·K respectively, the ceramic material layer (upper ceramic layer) 13 can further reduce the thermal resistance value of the thermally conductive insulating polymer layer 12.

[0040] An example of the manufacturing method of the thermally conductive substrate 100 is illustrated as follows. First, two metal foils are provided, one of the metal foils serving as the metal base plate 11 and the other metal foil serving as the metal layer 14. Secondly, the surfaces of these two metal foils are roughened by wet etching or mechanical grinding. Then, a ceramic material layer (upper ceramic layer) 13 is formed on the metal layer 14 by means such as thermal spraying, chemical vapor deposition, physical vapor deposition, or sputtering. Since the surface of the metal layer 14 has been roughened first, the ceramic material layer (upper ceramic layer) 13 is formed conformally on the surface of the metal layer 14 along the roughened surface of the metal layer 14, thereby forming micro-rough surfaces 16, 17 between the metal layer 14 and the ceramic material layer (upper ceramic layer) 13. Then, the metal base plate 11, the thermally conductive insulating polymer layer 12, the ceramic material layer (upper ceramic layer) 13, and the metal layer 14 are stacked in order from bottom to top and hot-pressed. Finally, the hot-pressed plate body is cut into an appropriate size by cutting or other mechanical means to form the thermally conductive substrate 100.

[0041] See Figure 2 , Figure 2 showing the thermally conductive substrate 200 of the second embodiment of the present invention. The thermally conductive substrate 200 is the same as Figure 1The difference in the first embodiment is that the ceramic material layer 13 is disposed between the thermally conductive insulating polymer layer 12 and the metal base plate 11. In this embodiment, the ceramic material layer 13 serves as a ceramic layer in the thermally conductive substrate. The ceramic material layer (lower ceramic layer) 13 makes physical contact with the metal base plate 11. Similarly, although the volume resistivity of the thermally conductive insulating polymer layer 12 decreases significantly at a high temperature of 100°C to 250°C compared to that at room temperature of 25°C, since the volume resistivity of the ceramic material does not decrease significantly at a high temperature of 100°C to 250°C compared to that at room temperature of 25°C, the overall volume resistivity of the thermally conductive insulating layer of the thermally conductive substrate does not decrease significantly, solving the problem that the volume resistivity drops suddenly at high temperatures when only using the thermally conductive insulating polymer layer as the thermally conductive insulating layer in the traditional structural design. In addition, the ceramic material layer (lower ceramic layer) 13 is disposed between the thermally conductive insulating polymer layer 12 and the metal base plate 11, and the ceramic material layer (lower ceramic layer) 13 can prevent the metal ions on the lower surface of the metal layer 14 from migrating downward, overcoming the problem of metal ion migration. Furthermore, as described above, the lower surface of the metal layer 14 and the upper surface of the metal base plate 11 can also be roughened. In addition to the technical effect of improving the bonding strength between layers, the thermally conductive substrate can also have a lower thermal resistance value and can improve the withstand voltage of the thermally conductive substrate in a high-temperature and high-humidity environment.

[0042] See Figure 3 , Figure 3 shows the thermally conductive substrate 300 of the third embodiment of the present invention. The thermally conductive substrate 300 is the same as Figure 1 the first embodiment or Figure 2The difference in the second embodiment is that the ceramic material layer 13 includes both an upper ceramic layer 131 and a lower ceramic layer 132. The upper ceramic layer 131 makes physical contact with the metal layer 14, and the lower ceramic layer 132 makes physical contact with the metal base plate 11. Similarly, although the volume resistivity of the thermally conductive insulating polymer layer 12 decreases significantly at high temperatures of 100°C to 250°C compared to that at room temperature of 25°C, since the volume resistivity of the ceramic material does not decrease significantly at high temperatures of 100°C to 250°C compared to that at room temperature of 25°C, the overall volume resistivity of the thermally conductive insulating layer of the thermally conductive substrate does not decrease significantly, solving the problem that the volume resistivity drops suddenly at high temperatures when only using the thermally conductive insulating polymer layer as the thermally conductive insulating layer in the traditional structural design. In addition, the upper ceramic layer 131 and the lower ceramic layer 132 are respectively disposed between the metal layer 14 and the thermally conductive insulating polymer layer 12 and between the thermally conductive insulating polymer layer 12 and the metal base plate 11. The upper ceramic layer 131 and the lower ceramic layer 132 can block the downward migration of metal ions on the lower surface of the metal layer 14, overcoming the problem of metal ion migration. Furthermore, as described above, the lower surface of the metal layer 14 and the upper surface of the metal base plate 11 can also be roughened. In addition to enhancing the bonding strength between layers, it can also make the thermally conductive substrate have a lower thermal resistance value and improve the withstand voltage of the thermally conductive substrate in a high-temperature and high-humidity environment.

[0043] Table 1 shows the experimental conditions, volume resistivity, and retention rate of Examples E1 to E10 and Comparative Examples C1 to C3 of the heat-conductive substrate of the present invention. The volume resistivity was measured at 25 °C room temperature and 175 °C high temperature using a 500 V voltage for 30 seconds. The ratio of the volume resistivity of the heat-conductive substrate at 175 °C to the volume resistivity at 25 °C is defined as the retention rate; the larger the retention rate, the less likely the volume resistivity of the heat-conductive substrate is to drop suddenly at high temperature compared to room temperature, that is, the volume resistivity at high temperature is less likely to decline compared to room temperature. The size of the heat-conductive substrate is 10 mm x 10 mm, and both the metal layer 14 and the metal bottom plate 11 are made of copper and have a thickness of 1.0 mm. The polymer in the thermally conductive insulating polymer layer 12 is epoxy resin, and the thermally conductive filler is alumina. The filling rate of the thermally conductive filler is 50, 66, or 72 vol%, so that the thermal conductivity of the thermally conductive insulating polymer layer 12 is 2 W / m·K, 6 W / m·K, or 12 W / m·K respectively. The thickness of the thermally conductive insulating polymer layer 12 is 30 μm, 100 μm, 150 μm, or 200 μm. The ceramic material layer includes an upper ceramic layer 131 and / or a lower ceramic layer 132. The thicknesses of the upper ceramic layer 131 and the lower ceramic layer 132 are 3 μm, 6 μm, or 100 μm. The upper ceramic layer 131 and / or the lower ceramic layer 132 is a single material layer made of materials such as alumina (Al2O3), zirconia (ZrO2), magnesia (MgO), or titanium oxide (TiO2), or a multi-layer composite layer composed of two sub-layers made of materials such as alumina / titanium oxide (Al2O3 / TiO2), alumina / magnesia (Al2O3 / MgO), alumina / zirconia (Al2O3 / ZrO2), etc. If only one ceramic material layer is provided on the heat-conductive substrate (i.e., the upper ceramic layer or the lower ceramic layer is provided), the thickness of the upper ceramic layer or the lower ceramic layer is 3 μm to 100 μm; if two ceramic material layers are provided on the heat-conductive substrate at the same time (i.e., the upper ceramic layer and the lower ceramic layer are provided), the total thickness of the upper ceramic layer and the lower ceramic layer added together is 5 μm to 200 μm. The lower surface of the metal layer has a roughness Rz, and the upper surface of the metal bottom plate has the roughness Rz. The roughness Rz is 2 μm to 80 μm, such as 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, or 70 μm, so as to control the value of the roughness Rz divided by the thickness of the upper ceramic layer or the lower ceramic layer to be 0.5 to 0.8.

[0044] Table 1

[0045]

[0046] Referring back to Table 1, C1 to C3 use a thermally conductive insulating polymer layer with a thermal conductivity of 2 to 12 W / m·K and a thickness of 100 to 200 μm. However, no ceramic material layer is provided in the thermally conductive substrate, and the test results show that the retention rate is very small, that is, the volume resistivity at 175°C decays much more compared to the volume resistivity at 25°C.

[0047] Referring back to Table 1, E1 to E4 also use a thermally conductive insulating polymer layer with a thermal conductivity of 2 to 12 W / m·K and a thickness of 30 to 200 μm, but are paired with an upper ceramic layer 131 and / or a lower ceramic layer 132 made of alumina (Al2O3) and of different thicknesses. The thickness of the thermally conductive insulating layer can be regarded as the sum of the thicknesses of the thermally conductive insulating polymer layer and the ceramic material layer, that is, the thickness of the thermally conductive insulating layer of E1 to E8 is the sum of the thicknesses of the thermally conductive insulating polymer layer and the upper ceramic layer and / or the lower ceramic layer, ranging from 153 to 230 μm. Table 1 shows that the retention rate of E1 to E4 is much larger than that of C1 to C3, which fully proves that by providing a ceramic material layer in the thermally conductive substrate, the volume resistivity at high temperature is not likely to drop suddenly relative to room temperature.

[0048] Referring back to Table 1, the conditions of E5 to E7 are the same as those of E1, but the lower ceramic layer uses a single material layer of other materials, and it also shows that the volume resistivity at high temperature is not likely to drop suddenly relative to room temperature. The ceramic material layer of E8 to E10 includes a lower ceramic layer, where the lower ceramic layer is a multi-layer composite material layer composed of two sub-layers. For example, the lower ceramic layer of E8 is a multi-layer composite material layer composed of two sub-layers with materials of alumina / titanium oxide (Al2O3 / TiO2) respectively, and it also shows that the volume resistivity at high temperature is not likely to drop suddenly relative to room temperature.

[0049] As can be seen from Table 1, by providing a ceramic material layer in the thermally conductive substrate, the volume resistivity at high temperature is not likely to drop suddenly relative to room temperature. In one embodiment, the volume resistivity of the thermally conductive substrate at a high temperature of 175°C is at least 10 9 Ω·cm, for example at least 10 10 Ω·cm, at least 10 11 Ω·cm, at least 10 12 Ω·cm, at least 10 13 Ω·cm, at least 10 14 Ω·cm or at least 10 15 Ω·cm, and the retention rate is at least 10 -4 , for example at least 10 -3 , at least 10 -2 or at least 10 -1According to the present invention, only an upper ceramic layer or a lower ceramic layer can be provided in the heat-conducting substrate, and the thickness of the upper ceramic layer or the lower ceramic layer is 3 μm to 100 μm. Alternatively, an upper ceramic layer and a lower ceramic layer can be respectively provided above and below the heat-conducting insulating polymer layer of the heat-conducting substrate, and the total thickness of the upper ceramic layer and the lower ceramic layer added together is 5 μm to 200 μm.

[0050] Table 2 shows the experimental conditions and thermal shock test results of Examples E11 - E17 and Comparative Examples C4 - C6 of the heat-conducting substrate of the present invention. The thermal shock test is used to evaluate whether the setting of the ceramic material layer can increase the bonding strength between layers. Therefore, E11 - E17 and C4 - C6 all include a ceramic material layer, and the best roughening conditions are obtained through the test. The thermal shock test is carried out according to the following parameters: -40°C to 150°C / 500 cycles, with a holding time of 30 minutes in each temperature zone, and the high / low temperature switching time < 5 seconds. The size of the heat-conducting substrate is all 10 mm x 10 mm, and both the metal layer 14 and the metal bottom plate 11 use copper and have a thickness of 1.0 mm. The polymer in the heat-conducting insulating polymer layer 12 uses epoxy resin, the heat-conducting filler uses alumina, and the filling rate of the heat-conducting filler is 50, 66 or 72 vol%, so that the heat-conducting coefficients of the heat-conducting insulating polymer layer 12 are 2 W / m·K, 6 W / m·K or 12 W / m·K respectively. The thickness of the heat-conducting insulating polymer layer 12 is 30 μm, 100 μm or 200 μm. The ceramic material layer includes an upper ceramic layer 131 and / or a lower ceramic layer 132, and the thicknesses of the upper ceramic layer 131 and the lower ceramic layer 132 are 3 μm, 7 μm, 10 μm or 100 μm. The upper ceramic layer 131 and / or the lower ceramic layer 132 is a single material layer made of materials such as alumina (Al2O3), zirconia (ZrO2), magnesia (MgO) or titanium oxide (TiO2). If only one ceramic material layer (i.e., the upper ceramic layer or the lower ceramic layer) is provided in the heat-conducting substrate, the thickness of the upper ceramic layer or the lower ceramic layer is 3 μm to 100 μm; if two ceramic material layers (i.e., the upper ceramic layer and the lower ceramic layer) are provided in the heat-conducting substrate at the same time, the total thickness of the upper ceramic layer and the lower ceramic layer added together is 5 μm to 200 μm.

[0051] Table 2

[0052]

[0053] Referring back to Table 2, C4 - C6 use a heat-conducting insulating polymer layer with a heat-conducting coefficient of 2 - 12 W / m·K and a thickness of 30 - 200 μm. The material of the ceramic material layer is alumina (Al2O3), and the roughness of the metal layer and the metal bottom plate is controlled at 1.3 μm or 1.5 μm. The thermal shock test results show that peeling occurs between the metal layer (copper layer) and the upper ceramic layer and between the metal bottom plate (copper layer) and the lower ceramic layer.

[0054] Referring to Table 2, for E11 to E14, a thermally conductive insulating polymer layer with a thermal conductivity of 2 to 12 W / m·K and a thickness of 30 to 200 μm is used. The material of the ceramic material layer is alumina (Al2O3). The roughness of the metal layer and the metal base plate is controlled within 2.1 μm to 80 μm. The thermal shock test shows that there is no peeling phenomenon between the metal layer (copper layer) and the upper ceramic layer, and between the metal base plate (copper layer) and the lower ceramic layer.

[0055] Referring to Table 2, for E15 to E17, compared with E13, the ceramic material layer (upper ceramic layer or lower ceramic layer) is a single material layer using different materials, and the other conditions are the same. The thermal shock test shows that there is no peeling phenomenon between the metal layer (copper layer) and the upper ceramic layer, and between the metal base plate (copper layer) and the lower ceramic layer.

[0056] As can be seen from Table 2, controlling the roughness of the metal layer and the metal base plate within 2 μm to 80 μm can improve the bonding strength between the metal layer and the upper ceramic layer and between the metal base plate and the lower ceramic layer. In particular, although this experiment is carried out using a metal layer 14 and a metal base plate 11 with a thickness of up to 1.0 mm, as long as the roughness of the metal layer and the metal base plate is appropriately controlled, there will be no peeling and delamination phenomenon. Obviously, the present invention can be applied to thick copper applications. The roughness of the lower surface of the metal layer and the roughness of the upper surface of the metal base plate should have an appropriate numerical range, neither too large nor too small. Too large roughness will cause a tip discharge problem between the roughened surfaces of the metal layer and the metal base plate, resulting in insufficient withstand voltage and difficult processing; too small roughness will not achieve the above technical effects. In an embodiment, the lower surface of the metal layer has a roughness Rz, the upper surface of the metal base plate has the roughness Rz, and the roughness Rz is 2 μm to 80 μm, such as 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm or 70 μm. Preferably, the value of the roughness Rz divided by the thickness of the upper ceramic layer or the lower ceramic layer is 0.2 to 0.8, such as 0.3, 0.4, 0.5, 0.6 or 0.7. The above parameters can make the heat-conducting substrate have good bonding strength between layers, and the roughening will not cause a tip discharge problem.

[0057] Table 3 shows the experimental conditions and HHBT test results of Examples E18 - E27 and Comparative Examples C7 - C8 of the heat-conducting substrate of the present invention. HHBT is used to evaluate the withstand voltage characteristics of the heat-conducting substrate under high temperature and high humidity conditions. The test conditions for HHBT are a DC withstand voltage test for 1000 hours at a temperature of 85°C and a relative humidity of 85% R.H. The sizes of the heat-conducting substrates are all 10 mm x 10 mm, where both the metal layer 14 and the metal bottom plate 11 are made of copper and have a thickness of 1.0 mm. The polymer in the thermally conductive insulating polymer layer 12 is epoxy resin, the thermally conductive filler is alumina, and the filling rate of the thermally conductive filler is 50, 66, or 72 vol%, so that the thermal conductivity of the thermally conductive insulating polymer layer 12 is 2 W / m·K, 6 W / m·K, or 12 W / m·K respectively. The thickness of the thermally conductive insulating polymer layer 12 is 30 μm, 100 μm, or 200 μm. The ceramic material layer includes an upper ceramic layer 131 and / or a lower ceramic layer 132, and the thicknesses of the upper ceramic layer 131 and the lower ceramic layer 132 are 3 μm or 100 μm. The ceramic material layer is a single material layer made of materials such as alumina (Al2O3), zirconia (ZrO2), magnesia (MgO), or titanium oxide (TiO2), or a multi-layer composite layer composed of two sub-layers made of materials such as zirconia / titanium oxide (ZrO2 / TiO2), zirconia / magnesia (ZrO2 / MgO), alumina / zirconia (Al2O3 / ZrO2), etc. If only one ceramic material layer (i.e., the upper ceramic layer or the lower ceramic layer) is provided on the heat-conducting substrate, the thickness of the upper ceramic layer or the lower ceramic layer is 3 μm - 100 μm; if two ceramic material layers (i.e., the upper ceramic layer and the lower ceramic layer) are provided on the heat-conducting substrate at the same time, the total thickness of the upper ceramic layer and the lower ceramic layer added together is 5 μm - 200 μm.

[0058] Table 3

[0059]

[0060] Referring back to Table 3, C7 - C8 use a thermally conductive insulating polymer layer with a thermal conductivity of 2 - 12 W / m·K and a thickness of 100 - 200 μm, but no ceramic material layer is provided in the heat-conducting substrate, and their HHBT test results show that C7 - C8 can only pass DC300V - DC500V.

[0061] Referring to Table 3, for E18 to E21, a thermally conductive insulating polymer layer with a thermal conductivity of 2 to 12 W / m·K and a thickness of 30 to 200 μm is used, and the ceramic material layer is made of alumina (Al2O3). If only one ceramic material layer (i.e., the upper ceramic layer or the lower ceramic layer) is provided on the thermally conductive substrate, the thickness of the upper ceramic layer or the lower ceramic layer is 3 μm to 100 μm; if two ceramic material layers (i.e., the upper ceramic layer and the lower ceramic layer) are provided on the thermally conductive substrate at the same time, the total thickness of the upper ceramic layer and the lower ceramic layer added together is 5 μm to 200 μm. The HHBT test results show that E18 can already pass DC1000V, and E19 to E21 can already pass DC2000V. The withstand voltage values of E19 to E21 are better than that of E18 because the total thickness of the ceramic material layer is thicker, so it can pass the DC withstand voltage test with a higher voltage.

[0062] Referring to Table 3, E22 to E27 use a single material layer of different materials or a multi-layer composite material layer composed of two sub-layers compared with E20, and the other conditions are the same. The HHBT test results show that E22 to E27 can all pass DC2000V.

[0063] As can be seen from Table 3, the withstand voltage of the thermally conductive substrate can be improved by providing a ceramic material layer in the thermally conductive substrate. In particular, if only one ceramic material layer is provided, the thickness of the upper ceramic layer or the lower ceramic layer is 3 μm to 100 μm; if two ceramic material layers are provided, the total thickness of the upper ceramic layer and the lower ceramic layer added together is 5 μm to 200 μm; the thickness within this numerical range can increase the withstand voltage value to at least DC1000V, or even to at least above DC2000V.

[0064] Table 4 shows the experimental conditions and thermal resistance test results of Examples E28 to E33 and Comparative Examples C9 to C10 of the thermally conductive substrate of the present invention. The thermal resistance test uses a TO-220 power transistor as the heat source. The output power W of the TO-220 power transistor is about 60 watts, and the metal layer pattern welded by the TO-220 power transistor has 10mm x 10mm = 100mm 2After measuring the temperature T1 at the top of the heat-conducting substrate (i.e., at the position between the TO-220 power transistor and the heat-conducting substrate) and the temperature T2 at the bottom of the heat-conducting substrate (i.e., at the position between the heat-conducting substrate and the heat sink below it), the thermal resistance is calculated by the following formula: Thermal resistance = (T1 - T2) / W = △T / W. The thermal resistance test does not use the ASTM D5470 standard specification for testing because the ASTM D5470 test method can only evaluate the heat dissipation effect in the longitudinal (z-axis) direction, while the TO-220 test method can evaluate the heat dissipation effect in all directions (including the z-axis, x-axis, and y-axis). From the TO-220 test results, the degree of heat dissipation impact on the heat-conducting substrate when using thick copper can be more accurately known. The sizes of the heat-conducting substrates are all 40mm x 40mm. Among them, the metal layer 14 all uses copper, and the metal bottom plate 11 uses copper or aluminum. The polymer in the thermally conductive insulating polymer layer 12 uses epoxy resin, the thermally conductive filler uses alumina, and the filling rate of the thermally conductive filler is 50, 66, or 72 vol%, so that the thermal conductivity of the thermally conductive insulating polymer layer 12 is 2W / m·K, 6W / m·K, or 12W / m·K respectively. The thickness of the thermally conductive insulating polymer layer 12 is 100μm. The ceramic material layer includes an upper ceramic layer 131 and a lower ceramic layer 132. The thickness of the upper ceramic layer 131 is 6μm, and the thickness of the lower ceramic layer 132 is 3μm. The ceramic material layer is a single material layer made of materials such as alumina (Al2O3), magnesia (MgO), etc., or a multi-layer composite layer composed of two sub-layers made of alumina / magnesia (Al2O3 / MgO) materials respectively.

[0065] Table 4

[0066]

[0067]

[0068] Referring to Table 4 again, C9 to C10 use a thermally conductive insulating polymer layer with a thermal conductivity of 12W / m·K and a thickness of 100μm. The thickness of the metal layer is not thick, being 0.1mm, and the thickness of the metal bottom plate is relatively thick, being 0.3mm. However, there is no ceramic material layer set in the heat-conducting substrate. The test results show that the thermal resistances of C9 and C10 are 0.419℃ / W and 0.471℃ / W respectively.

[0069] Referring to Table 4, for E28 - E33 compared with C9 - C10, the ceramic material layer (upper ceramic layer or lower ceramic layer) is a single material layer of different materials or a multi - composite material layer composed of two sub - layers, combined with a thermally conductive insulating polymer layer with a thermal conductivity of 2 W / m·K, 6 W / m·K or 12 W / m·K and a thickness of 100 μm. The metal layer has a relatively thick thickness of 0.3 mm or 10 mm, and the metal bottom plate has a relatively thick thickness of 0.3 mm. The test results show that the thermal resistance of E28 - E33 is 0.09 °C / W - 0.27 °C / W.

[0070] As can be seen from Table 4, even though the metal layer thickness of E28 - E33 is thicker than that of C9 - C10, the thermal resistance of E28 - E33 is much lower than that of C9 - C10. Obviously, E28 - E33 has a good heat dissipation effect in the application of thick copper with a thickness of 0.3 mm - 10 mm, that is, there is a significant effect on heat dissipation in the x - axis, y - axis and z - axis directions, and as shown in Table 2, there is no peeling or delamination phenomenon. In practical applications, the material of the metal layer can be copper, and the material of the metal bottom plate can be copper, aluminum, or copper / aluminum alloy. According to the present invention, the thick copper application means that the thickness of the metal layer and the metal bottom plate is 0.3 mm - 10 mm, such as 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm or 9 mm.

[0071] In summary, for the heat - conducting substrate of the present invention, by setting the ceramic material layer, the volume resistivity at high temperature does not drop suddenly relative to room temperature. In addition, according to the present invention, roughening the surface of the metal layer or the metal bottom plate can increase the bonding strength between layers, and there is no peeling or delamination phenomenon. The heat - conducting substrate of the present invention also has a good heat dissipation effect.

[0072] The technical content and technical features of the present invention have been disclosed above. However, those skilled in the art may still make various substitutions and modifications that do not deviate from the concept of the present invention based on the inspiration and disclosure of the present invention. Therefore, the protection scope of the present invention should not be limited to what is disclosed in the embodiments, but should include various substitutions and modifications that do not deviate from the present invention and are covered by the following claims.

Claims

1. A heat-conducting substrate, comprising: A metal base plate is a copper layer; A metal layer is a copper layer; A thermally conductive insulating polymer layer is located between the metal layer and the metal base plate; And A ceramic material layer includes an upper ceramic layer formed on the surface of the metal layer and a lower ceramic layer formed on the surface of the metal base plate; wherein: The upper ceramic layer is disposed between the metal layer and the thermally conductive insulating polymer layer, and the lower ceramic layer is disposed between the thermally conductive insulating polymer layer and the metal base plate; The metal base plate and the lower ceramic layer, the metal layer and the upper ceramic layer, and the thermally conductive insulating polymer layer are stacked by a hot pressing method; And The ratio between the volume resistivity of the thermally conductive substrate at 175 °C and the volume resistivity at 25 °C is defined as the retention rate, and the retention rate is 1.3E-03 to 7.3E-01.

2. The heat-conducting substrate according to claim 1, wherein the volume resistivity of the heat-conducting substrate at 175 °C is at least 10 9 Ω·cm.

3. The heat-conducting substrate according to claim 1, wherein the upper ceramic layer forms physical contact with the metal layer, and the lower ceramic layer forms physical contact with the metal base plate.

4. The heat-conducting substrate according to claim 1, wherein the thicknesses of the upper ceramic layer and the lower ceramic layer are 3 μm to 100 μm.

5. The heat-conducting substrate according to claim 1, wherein the total thickness of the upper ceramic layer and the lower ceramic layer added together is 5 μm to 200 μm.

6. The heat-conducting substrate according to claim 1, wherein the upper ceramic layer and the lower ceramic layer are single material layers, or are multi-layer composite material layers composed of multiple sub-layers, and wherein the materials of the single material layer and the multiple sub-layers are alumina, zirconia, magnesia or titanium oxide.

7. The heat-conducting substrate according to claim 1, wherein the thicknesses of the metal layer and the metal base plate are 0.3 mm to 10 mm.

8. The heat-conducting substrate according to claim 1, wherein the lower surface of the metal layer has a roughness Rz, and the upper surface of the metal base plate has the roughness Rz, and the roughness Rz is 2 μm to 80 μm.

9. The heat-conducting substrate according to claim 8, wherein the value of the roughness Rz divided by the thickness of the upper ceramic layer or the lower ceramic layer is 0.2 to 0.

8.

10. For the heat-conducting substrate according to claim 1, when the heat-conducting substrate undergoes a DC withstand voltage HHBT test at a temperature of 85 °C and a relative humidity of 85% R.H. for 1000 hours, the withstand voltage value is at least DC 1000 V.

11. The heat-conducting substrate according to claim 1, wherein the thermal resistance of the heat-conducting substrate is less than 0.16 °C / W.

Images