High thermal conductive circuit board with embedded ceramic thermal conductive block and hollow copper clad layer

Abstract

The application discloses a high-thermal-conductivity circuit board with embedded ceramic heat-conducting blocks and a hollow copper-clad layer, mainly comprising a circuit substrate body, heat-dissipating ceramic blocks corresponding to through holes in the circuit substrate body, fixing parts for embedding and fixing the heat-dissipating ceramic blocks in the through holes of the circuit substrate body, a metal circuit layer and a hollow high-thermal-conductivity metal layer. The circuit substrate body comprises a dielectric material layer, which is respectively plated with the metal circuit layer and the hollow high-thermal-conductivity metal layer. The hollow part of the hollow high-thermal-conductivity metal layer corresponds to the fixing parts and part of the heat-dissipating ceramic blocks. In addition, the heat-conductivity coefficient of the heat-dissipating ceramic blocks is higher than that of the dielectric material layer, and the heat-conductivity coefficient of the hollow high-thermal-conductivity metal layer is higher than that of the heat-dissipating ceramic blocks. The fixing parts and part of the heat-dissipating ceramic blocks are exposed to the outside, so that the problem of board explosion during high-temperature baking is effectively solved.

Description

Technical Field

[0001] This invention relates to a high thermal conductivity circuit board, and more particularly to a high thermal conductivity circuit board having an embedded ceramic thermal conductive block and a hollowed-out copper-clad layer. Background Technology

[0002] A printed circuit board (PCB) is a device that uses a copper foil substrate as its primary base material to house electronic components. This copper foil substrate typically uses a dielectric material as the insulating layer and copper foil conductors as the conductive layer, with the conductive layer arranged within the dielectric insulating layer. The dielectric material is often formed by impregnating paper, bakelite, fiberglass, rubber, or other polymer insulating materials with resin.

[0003] Because the insulating material of the copper foil substrate of a typical printed circuit board is mostly dielectric material, not a good conductor of heat, the heat generated by high-heat components tends to accumulate near the high-power components, making the operating environment far from ideal. At the same time, excessive heat buildup usually leads to the expansion of the printed circuit board. However, the different coefficients of thermal expansion between the printed circuit board and the circuit components inevitably create a risk of damage to the contacts due to thermal stress.

[0004] To address the aforementioned issues, Taiwanese invention patents I670998 and I690246 disclose an embedded structure. This structure embeds a high thermal conductivity ceramic block into a dielectric material, such as the commonly known FR4 board, to increase heat dissipation. High-heat-generating components are positioned above the high thermal conductivity ceramic block, effectively dissipating the heat generated by these components through the underlying high thermal conductivity layer (copper), thus significantly improving overall heat dissipation. Based on this, current manufacturing processes for printed circuit boards with heat-dissipating ceramic blocks primarily involve filling the gap between the outer periphery of the ceramic block and the FR-4 dielectric material layer with epoxy resin. After the resin cures, the ceramic block is securely bonded to the FR-4 dielectric material layer. However, during the actual operation, it was found that after the printed circuit board completes the installation of the heat dissipation ceramic block and enters the reflow oven, the high temperature of the reflow oven will cause the moisture that may be buried in the high thermal conductivity ceramic block or epoxy resin to be vaporized / or some compound materials to be released. As a result, due to the local release of gas or water vapor, the FR-4 dielectric material layer with the embedded ceramic block and the underlying copper layer expand and separate, resulting in a board bursting state.

[0005] To address the issue of expansion and cracking between the FR-4 dielectric material layer and the copper plating layer caused by the generation of gas and moisture, the applicant has made gradual modifications, referencing... Figure 1As shown, the applicant attempted to mesh the copper-clad laminate, that is, to perforate a large number of holes in the copper-clad laminate, so that the bottom copper plate 1 (high thermal conductivity layer) is meshed. The meshed copper plate 1 has multiple holes 10 and gaps. Some of the holes 10 and gaps corresponding to the heat dissipation ceramic block 2 can allow the gas and water vapor mentioned above to be quickly discharged, so that the board will not explode. However, in contrast, because the copper plate is meshed, the amount of thermally conductive copper is reduced, which greatly reduces the heat conduction effect and cannot improve the problem that the heat generated by the high-heat-generating components accumulates near the high-power components, resulting in a high-temperature operating environment.

[0006] Considering the structural issues mentioned above regarding avoiding board explosion but reducing thermal conductivity, please refer to... Figure 2 The applicant further modified the copper-clad laminate to a longitudinal and transverse slotted structure. The main feature is that the copper plate 1 is slotted 12 to allow gas and water vapor to be discharged quickly. The slots 12 are positioned in a transverse and longitudinal manner through each heat dissipation ceramic block 2. Therefore, the copper plate 1 has a cross-shaped slot 12 pattern at the position corresponding to the heat dissipation ceramic block 2. While the crisscrossing slots 12 on the copper plate 1 corresponding to the positions of the heat sink ceramic block 2 can indeed solve the problem of board bursting caused by gas and moisture, and reduce the thermal conductivity degradation problem caused by the significant reduction in copper plating in the previous solution, it still leads to the following two shortcomings: First, the center of the heat sink ceramic block 2, which is usually the core position of the high-heat-generating components above, cannot be dissipated through the copper plate 1 because of the slots 12. Therefore, it will still cause local heat accumulation and uneven heat flow distribution, and the heat conduction effect will be relatively reduced, failing to effectively improve the risk of damage caused by heat accumulation from high-heat-generating components. More importantly, since the slots 12 are cross-shaped and connect each heat sink ceramic block 2, each group of four heat sink ceramic blocks 2 is divided by the cross of the slots 12, resulting in an independent heat dissipation area 3. If this independent heat dissipation area 3 is not properly fixed by screws or thermally conductive adhesive to the heat dissipation fins (not shown in the figure), the heat dissipation efficiency of each independent block will be different, and because the copper plate 1 is divided into multiple thermal islands, it is impossible to ensure average heat dissipation over a large area.

[0007] Therefore, the objective of this invention is to ensure that the printed circuit board will not explode due to the release of gas or moisture after the heat dissipation ceramic block is installed and it enters the reflow oven, while also ensuring the heat conduction and heat dissipation effect of the circuit board with the heat dissipation ceramic block. Summary of the Invention

[0008] In view of the above-mentioned shortcomings of the prior art, according to the embodiments of the present invention, it is intended to provide a high thermal conductivity circuit board with embedded ceramic heat-conducting blocks and hollow copper-clad laminate, aiming to achieve the following objectives: (1) the hollow part of the high thermal conductivity metal layer corresponds to the fixing part and part of the heat dissipation ceramic block, solving the problem of gas release and board explosion during high-temperature baking of the reflow oven, and improving the product yield; (2) ensuring that the bottom of each heat dissipation ceramic block has a thermally conductive metal layer, ensuring that the central position of the heat dissipation ceramic block is well thermally connected to the copper-clad laminate, so that the heat generated by the heat-generating element can be quickly and reliably discharged to achieve a better heat dissipation effect; (3) the copper-clad laminate is completely connected except for the hollow part, so that the heat energy of the entire circuit board can be easily discharged through the rear heat dissipation fins, solving the problem of uneven heat dissipation of heat islands.

[0009] According to an embodiment, the present invention provides a high thermal conductivity circuit board with an embedded ceramic heat-conducting block and a hollowed-out copper-clad layer, comprising: a circuit substrate body, including a first upper plate surface and a first lower plate surface opposite to the first upper plate surface, and at least one through hole formed on the circuit substrate body penetrating the first upper plate surface and the first lower plate surface, wherein the circuit substrate body includes at least one dielectric material layer; at least one heat-dissipating ceramic block corresponding to the through hole, including a second upper plate surface and a second lower plate surface, wherein the thermal conductivity of the heat-dissipating ceramic block is higher than that of the dielectric material layer; at least one fixing part for embedding and fixing the heat-dissipating ceramic block in the through hole of the circuit substrate body, such that the second lower plate surface corresponds to the first lower plate surface, wherein the circuit substrate body has a connection between the first upper plate surface and the first lower plate surface and surrounds the through hole. The perforated inner edge of the hole, and the heat dissipation ceramic block has an outer periphery connecting the second upper plate surface and the second lower plate surface, and the fixing part is a fixing material between the inner edge of the perforation and the outer periphery for fixing and connecting the two; a metal circuit layer plated on the first upper plate surface and the second upper plate surface for providing a plurality of circuit elements, wherein at least one of the circuit elements includes a high-power element, and the high-power element is provided at the metal circuit layer on the second upper plate surface; and a hollow high thermal conductivity metal layer provided below the first lower plate surface and the second lower plate surface, wherein the thermal conductivity of the hollow high thermal conductivity metal layer is higher than that of the heat dissipation ceramic block, and the hollow high thermal conductivity metal layer forms at least a plurality of hollow portions corresponding to the fixing part, such that at least a portion of the fixing part and the heat dissipation ceramic block are exposed through the hollow portions.

[0010] Compared to existing technologies, this invention, due to the special design of the hollowed-out portion, exposes part of the fixing portion, allowing any gas and moisture that may be released to find a channel for release, completely solving the problem of board bursting and significantly improving manufacturing yield, while also effectively reducing manufacturing costs; in particular, the hollowed-out holes avoid the center of the embedded ceramic heat-conducting block, allowing the heat generated by the heating element to be effectively discharged, ensuring the working efficiency of the final circuit board product; and without cutting the copper-clad part into thermal islands, the heat sink fins added behind can completely carry away the heat from the circuit board as long as there are multiple good thermal contact points with the copper-clad board, without the problem of uneven heat dissipation, allowing the high-temperature heating element to operate in an ideal temperature environment.

[0011] According to one embodiment of the present invention, in the aforementioned high thermal conductivity circuit board having an embedded ceramic heat-conducting block and a hollowed-out copper-clad layer, the fixing part is a mechanical buffering hybrid material formed by filling and curing with resin glue, which has greater flexibility than the aforementioned heat-dissipating ceramic block.

[0012] According to an embodiment of the present invention, in the aforementioned high thermal conductivity circuit board having an embedded ceramic thermal conductive block and a hollow copper-clad layer, the circuit board body is a multilayer circuit board including multiple dielectric material layers and multiple metal conductive layers.

[0013] According to an embodiment of the present invention, in the aforementioned high thermal conductivity circuit board having an embedded ceramic heat-conducting block and a hollowed-out copper-clad layer, the hollowed-out portion includes at least a plurality of hollowed-out holes corresponding to the aforementioned heat-dissipating ceramic block and surrounding the aforementioned fixing portion, and the aforementioned plurality of hollowed-out holes are radially symmetrically distributed.

[0014] According to an embodiment of the present invention, in the aforementioned high thermal conductivity circuit board having an embedded ceramic heat-conducting block and a hollowed-out copper-clad layer, the circuit board body has a plurality of through holes, the heat dissipation ceramic block and the corresponding fixing part are respectively embedded in the plurality of through holes, and the hollowed-out part is arranged by a dotted line that penetrates at least part of the plurality of heat dissipation ceramic blocks and the fixing part. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of copper plate meshing in Taiwan Invention Patent I670998.

[0016] Figure 2 This is a schematic diagram of the slotted copper plate structure in Taiwan Invention Patent I690246.

[0017] Figure 3 This is a cross-sectional structural diagram of the high thermal conductivity circuit board of the present invention.

[0018] Figure 4 This is a three-dimensional exploded view of the high thermal conductivity circuit board of the present invention.

[0019] Figure 5 This is a schematic diagram of another high thermal conductivity circuit board of the present invention.

[0020] Figure 6 This is a schematic diagram of the structure of the present invention, showing the arrangement of multiple through holes with dashed lines.

[0021] Wherein: 1 is a copper plate; 10 is a hole; 12 is a slot; 2 is a heat dissipation ceramic block; 3 is an independent heat dissipation area; 4, 4', and 4” are the circuit board body; 40 is a dielectric material layer; 41, 41', and 41” are heat dissipation ceramic blocks; 42, 42', and 42” are fixing parts; 43 is a metal conductive layer; 44 and 44' are hollowed-out high thermal conductivity metal; 400 and 400” are through holes; 401 is the first upper plate surface; 402 is the first lower plate surface; 404 is the inner edge of the through hole; 410 is the second upper plate surface; 412 is the second lower plate surface; 414 is the outer perimeter; 440, 440', and 440” are hollowed-out parts; 5 is a high-power component. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. These embodiments should be understood as illustrative only and not as limiting the scope of protection of the present invention. After reading the description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

[0023] like Figures 3-4 As shown in the preferred embodiment of the present invention, a high thermal conductivity circuit board with an embedded ceramic heat-conducting block and a hollowed-out copper-clad layer is provided. The circuit board body 4 is based on a multi-layer FR-4 dielectric material layer 40 in each figure. Through-holes 400 are pre-cut into the dielectric material layer 40, for example, using a laser. A corresponding heat-dissipating ceramic block 41 (square columnar shape), such as aluminum nitride (AIN), is then embedded into the through-holes 400. However, as those skilled in the art will readily understand, the size of the FR-4 substrate in this embodiment can be greater than 10 cm. 2 less than 3600cm 2 Simple replacement within the range. The circuit board body 4 mentioned above is mainly a multilayer circuit board with multiple layers of dielectric material 40 and multiple layers of metal conductive layer 43.

[0024] For ease of explanation, following the orientation of the figures, the surface of the dielectric material layer 40 located above the figure is referred to as the first upper plate surface 401, and the opposite lower surface is referred to as the first lower plate surface 402. The upper and lower surfaces of the heat dissipation ceramic block 41 are referred to as the second upper plate surface 410 and the second lower plate surface 412, respectively, and the thickness of the dielectric material layer 40 is similar to the thickness of the heat dissipation ceramic block 41. Of course, those skilled in the art will easily understand that the dielectric material layer 40 can be replaced with epoxy resin or glass fiber prepreg substrates such as FR-1 (commonly known as bakelite board), FR-3, FR-6, and G-10; the cutting method can also be mechanical cutting or similar methods; and the heat dissipation ceramic block 41 can be replaced with silicon nitride (Si3N4), alumina (Al2O3), silicon carbide (SiC), beryllium oxide (BeO), etc., without hindering the implementation of the present invention.

[0025] Subsequently, a fixing material such as epoxy resin is used to fill the gap between the outer periphery 414 of the aluminum nitride heat dissipation ceramic block 41 and the inner edge 404 of the perforation of the FR-4 dielectric material layer 40. After the adhesive cures, the outer periphery 414 and the inner edge 404 of the perforation of the heat dissipation ceramic block 41 are firmly bonded together. Moreover, the fixing part 42 formed by the cured adhesive itself has greater flexibility than the heat dissipation ceramic block 41. Therefore, it is a good mechanical buffering hybrid material, which can still provide buffering protection even if the two different materials have different coefficients of thermal expansion, and will not cause problems in subsequent heating treatment and operation. Of course, those skilled in the art can easily deduce that although this embodiment uses epoxy resin as an example, it is a simple modification to use silicon as a base or other flexible adhesives, which does not hinder the implementation of the present invention.

[0026] After the aforementioned heat dissipation ceramic block 41 is fixed by the fixing part 42 into the through hole 400 of the dielectric material layer 40, it can be polished to make the first upper plate surface 401 and the second upper plate surface 410 flush with each other. In this embodiment, a titanium layer and a copper layer are sequentially formed on the first upper plate surface 401 and the second upper plate surface 410 by, for example, sputtering. Then, the metal seed layer is thickened by electroplating to form an electroplated copper layer. In order to protect the copper layer from easy oxidation, a nickel and gold layer is added above the copper layer in this embodiment to form a multi-layer metal layer. Of course, those skilled in the art will easily understand that the above-mentioned protective copper layer material can be replaced by organic solderability preservatives (OSP), silver, tin, etc., without hindering the implementation of the present invention. The aforementioned metal layer, after a series of subsequent conventional processing procedures such as patterning, becomes the metal circuit layer 43 in this embodiment. Of course, those skilled in this technology may also use common methods such as vapor deposition or other feasible methods, and use a suitable metal to form the metal circuit layer 43 of the above-mentioned multilayer structure.

[0027] Since the first lower plate surface 402 and the second lower plate surface 412 are flush with each other, and copper has a good thermal conductivity (380Wm), -1 K -1 Therefore, in this embodiment, a copper metal layer is also formed below the first lower plate surface 402 and the second lower plate surface 412, thereby forming a hollow high thermal conductivity metal 44 with a thermal conductivity higher than that of the aforementioned dielectric material layer 40. Since the hollow high thermal conductivity metal 44 connects the dielectric material layer 40 and the heat dissipation ceramic block 41 with good thermal conductivity, but the thermal conductivity of the heat dissipation ceramic block 41 and the hollow high thermal conductivity metal 44 is much higher than that of the dielectric material layer 40, the hollow high thermal conductivity metal 44 mainly conducts the heat energy transmitted from the heat dissipation ceramic block 41 outward from the horizontal direction of the diagram. In contrast, the general circuit components disposed above the dielectric material layer 40 will not be easily disturbed by the heat energy transmitted from the heat dissipation ceramic block 41, thereby isolating the high heat generated by the high power component 5 from other surrounding general circuit components.

[0028] After the dielectric material layer 40 is set, it can be used to install the required circuit components. The aforementioned circuit components include at least one high-power component 5. In this example, the high-power component 5 is an IGBT, which is soldered and fixed to the metal circuit layer 43 and the corresponding pad above the heat sink ceramic block 41 by surface-mount technology (SMT). The electrodes of the IGBT are connected to the corresponding pads via metal leads. Because IGBTs have advantages such as high efficiency and fast switching speed, they are often used in electronic devices with high power consumption, such as air conditioners, refrigerators, audio equipment, and motor drivers. Therefore, when the aforementioned electronic devices are operating, the IGBTs will generate a large amount of heat. This heat will pass directly through the alumina heat sink ceramic block 41 and be conducted downwards to the hollow high thermal conductivity metal 44, and then be conducted away from the position of the heat sink ceramic block 41. The aforementioned heat will be further dissipated by the large area of ​​the hollow high thermal conductivity metal 44. Even if the lower heat sink fins are only screwed to the circuit board with multiple bolts, good heat conduction can be achieved in the screwed pressure part, allowing the heat generated on the entire circuit board to be carried away by the rear heat sink fins, thereby increasing the heat dissipation efficiency.

[0029] The hollowed-out portion 440 formed by the hollowed-out high thermal conductivity metal 44 corresponds to the fixing portion 42 and part of the heat dissipation ceramic block 41, so that the fixing portion 42 and part of the heat dissipation ceramic block 41 are exposed through the hollowed-out portion 440. The so-called part of the heat dissipation ceramic block 41 is only around the heat dissipation ceramic block 41 and does not penetrate the entire heat dissipation ceramic block 41, so that the gas and water vapor generated when entering the reflow oven for high temperature baking can be discharged through the hollowed-out portion 440 without the problem of board explosion due to expansion. At the same time, the hollowed-out high thermal conductivity metal 44 attached to the center of the heat dissipation ceramic block 41 can dissipate heat over a large area, thereby increasing the heat dissipation efficiency.

[0030] like Figure 5 The figure shows a schematic diagram of another high thermal conductivity circuit board of the present invention. As can be seen from the figure, the hollow portions 440' formed on the circuit board body 4' are mainly numerous and surround the fixing portion 42' and partially correspond to the four corners of the heat dissipation ceramic block 41'. That is to say, the periphery of part of the heat dissipation ceramic block 41' and the entire fixing portion 42' are exposed. In addition, the hollow portions 440' can be radially and symmetrically distributed on the hollow high thermal conductivity metal 44'. Except for the aforementioned locations around part of the heat dissipation ceramic block 41' and the entire fixing portion 42', the remaining hollow portions 440' are arranged radially to increase the efficiency of gas and water vapor discharge without affecting the heat dissipation effect.

[0031] like Figure 6 The diagram shows a schematic of the structure of the plurality of through holes arranged in dashed lines according to the present invention. Taking the circuit board body 4” as an example, a plurality of through holes 400” are formed. Each through hole 400” is provided with a heat dissipation ceramic block 41” and a corresponding fixing part 42”. The hollow part 440” connects the heat dissipation ceramic blocks 41” in a cross shape in a dashed manner. More importantly, the hollow part 440” corresponding to the heat dissipation ceramic block 41” is only located around the heat dissipation ceramic block 41” and the central position is not exposed. As for the position covered by the fixing part 42”, it is completely exposed. In this way, connecting the heat dissipation ceramic blocks 41” in a cross shape in a dashed manner can increase the efficiency of the aforementioned gas and water vapor discharge, while not affecting the heat dissipation effect.

Claims

1. A high thermal conductivity circuit board with an embedded ceramic heat-conducting block and a hollowed-out copper-clad layer, characterized in that, include: A circuit board body includes a first upper plate surface and a first lower plate surface opposite to the first upper plate surface, and at least one through hole is formed on the circuit board body through the first upper plate surface and the first lower plate surface, wherein the circuit board body includes at least one dielectric material layer. At least one heat dissipation ceramic block is embedded in the aforementioned through hole, comprising a second upper plate surface and a second lower plate surface, wherein the thermal conductivity of the aforementioned heat dissipation ceramic block is higher than that of the aforementioned dielectric material layer. At least one fixing part is provided for embedding and fixing the heat dissipation ceramic block into the through hole of the circuit board body, such that the second lower plate surface corresponds to the first lower plate surface respectively, wherein the circuit board body has an inner edge of a through hole that connects the first upper plate surface and the first lower plate surface and surrounds the through hole, and the heat dissipation ceramic block has an outer periphery that connects the second upper plate surface and the second lower plate surface, and the fixing part is a fixing material that is located between the inner edge of the through hole and the outer periphery for fixing and connecting the two. A metal circuit layer plated on the first upper plate surface and the second upper plate surface is provided for mounting a plurality of circuit elements, wherein at least one of the circuit elements includes a high-power element, and the high-power element is mounted on the metal circuit layer on the second upper plate surface; and A perforated high thermal conductivity metal layer is disposed below the first lower plate surface and the second lower plate surface, wherein the thermal conductivity of the perforated high thermal conductivity metal layer is higher than that of the heat dissipation ceramic block, and the perforated high thermal conductivity metal layer has at least a plurality of perforations corresponding to the aforementioned fixing portion, such that at least a portion of the fixing portion and the heat dissipation ceramic block are exposed through the perforations.

2. The high thermal conductivity circuit board as described in claim 1, characterized in that, The aforementioned fixing part is a mechanical buffer mixture material formed by filling and curing resin glue, which has greater flexibility than the aforementioned heat dissipation ceramic block.

3. The high thermal conductivity circuit board as described in claim 1, characterized in that, The aforementioned circuit board body is a multilayer circuit board comprising multiple layers of dielectric material and multiple layers of conductive metal.

4. The high thermal conductivity circuit board as described in claim 1, 2, or 3, characterized in that, The aforementioned hollow portion includes at least a plurality of hollow holes corresponding to the aforementioned heat dissipation ceramic block and surrounding the aforementioned fixing portion, and the aforementioned plurality of hollow holes are radially symmetrically distributed.

5. The high thermal conductivity circuit board as described in claim 1, 2, or 3, characterized in that, The circuit board body has a plurality of through holes, the heat dissipation ceramic block and the corresponding fixing part are respectively embedded in the plurality of through holes, and the hollow part is arranged by a dotted line that penetrates at least part of the heat dissipation ceramic block and the fixing part.

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