Printed circuit board, printed circuit board manufacturing method, and server

Abstract

The application provides a printed circuit board, a printed circuit board preparation method and a server, comprising a plurality of chip mounting areas and a heat dissipation pad area arranged in each chip mounting area; the heat dissipation pad area is provided with a plurality of through holes, the through holes are provided with blind holes at the bottom surface of the printed circuit board, the center of the blind hole coincides with the center of the through hole, the diameter of the blind hole is larger than the diameter of the through hole, and the depth of the blind hole is smaller than the depth of the through hole. The printed circuit board provided by the application sets a plurality of through holes in the heat dissipation pad area, and sets blind holes at the bottom surface of the printed circuit board where the through holes are located. In the subsequent use process of the chip, the area and volume of the metal solder connected to the chip are improved. At the same time, the metal volume of the blind hole in the bottom layer of the printed circuit board is large and exposed to the external air, which is more conducive to air conduction heat dissipation, can quickly dissipate the energy consumption heat of the chip, and further improves the stability of the electrical performance of the chip.

Description

Technical Field

[0001] This application relates to the field of server technology, specifically to a printed circuit board, a method for manufacturing a printed circuit board, and a server. Background Technology

[0002] As electronic products become increasingly miniaturized and feature-rich, their circuit systems become more complex and bulky. With chip power increasing while chip size decreases, heat dissipation becomes a key design challenge for high-power chips (such as DC-DC converters and linear regulators).

[0003] Existing high-power chip heat dissipation pads typically employ vias in these areas, followed by copper traces of the same size as the heat dissipation pads laid on various inner layers of the PCB (Printed Circuit Board). The electrical network of these copper traces aligns with the heat dissipation pad network, usually using the GND network for heat dissipation. However, current PCB designs struggle to meet the rapid heat dissipation requirements of chips. Furthermore, if chip heat dissipation is inadequate, it can easily lead to a degradation in the chip's electrical performance and instability in the entire electrical system's signals. Summary of the Invention

[0004] This application provides a printed circuit board, a method for manufacturing a printed circuit board, and a server for optimizing the heat dissipation function of the printed circuit board.

[0005] This application provides a printed circuit board, including: a plurality of chip mounting areas and a heat dissipation pad area disposed in each chip mounting area;

[0006] The heat dissipation pad area is provided with multiple through holes. The through holes are located on the bottom surface of the printed circuit board and are provided with blind holes. The centers of the blind holes and the through holes coincide. The diameter of the blind holes is larger than the diameter of the through holes, and the depth of the blind holes is smaller than the depth of the through holes.

[0007] According to the printed circuit board provided in this application, the heat dissipation pad area is located on the bottom surface of the printed circuit board and a copper sheet is laid thereon, and the copper sheet is in contact with the blind via.

[0008] According to the printed circuit board provided in this application, the diameter of the through hole is 8mil-12mil, and the diameter of the blind hole is twice the diameter of the through hole.

[0009] According to the printed circuit board provided in this application, when the printed circuit board has more than or equal to ten layers, the depth of the blind via is the thickness of four layers.

[0010] When the printed circuit board has fewer than ten layers, the depth of the blind via is equal to the thickness of two layers.

[0011] According to the printed circuit board provided in this application, the junction between the inner wall of the through hole and the inner wall of the blind hole in the printed circuit board is a slope.

[0012] This application also provides a method for manufacturing the printed circuit board described above, comprising:

[0013] Drill multiple through holes in the heat dissipation pad area of ​​the chip mounting area on the printed circuit board;

[0014] Using a back-drilling method, a blind hole is drilled on the bottom surface of the printed circuit board where the through hole is located. The center of the blind hole coincides with that of the through hole. The diameter of the blind hole is larger than that of the through hole, and the depth of the blind hole is smaller than that of the through hole.

[0015] According to the printed circuit board manufacturing method provided in this application, drilling multiple through holes in the heat dissipation pad area of ​​the chip mounting area of ​​the printed circuit board includes:

[0016] Based on the trace density and trace position of the chip mounting area, the number of vias and the positional distribution of the vias in the heat dissipation pad area are determined.

[0017] Based on the number of vias and their location distribution, multiple vias are drilled in the heat dissipation pad area of ​​the chip mounting area on the printed circuit board.

[0018] According to the printed circuit board manufacturing method provided in this application, after drilling blind holes located on the bottom surface of the printed circuit board where the through holes are located, the method further includes:

[0019] Copper is electroplated onto the bottom surface of the heat dissipation pad area to form a copper sheet on the bottom surface of the heat dissipation pad area, and the copper sheet contacts the blind hole.

[0020] According to the printed circuit board manufacturing method provided in this application, after electroplating copper on the bottom surface of the heat dissipation pad area, the method further includes:

[0021] The through holes and blind holes are tinned using wave soldering or stencil soldering, so that the through holes and blind holes are filled with solder, and the contact area between the copper sheet and the blind hole is covered with solder.

[0022] This application also provides a server, including the printed circuit board described above.

[0023] This application provides a printed circuit board, a method for manufacturing a printed circuit board, and a server. By setting multiple through-holes in the heat dissipation pad area and blind vias on the bottom surface of the printed circuit board, the area and volume of the metal solder connected to the chip are increased during subsequent chip use. Simultaneously, the larger metal volume of the blind vias on the bottom surface of the printed circuit board, exposed to the external air, facilitates heat dissipation through air conduction, allowing for rapid dissipation of the chip's energy consumption heat, thereby improving the stability of the chip's electrical performance. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0025] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the heat dissipation pad area design for a high-power chip using the relevant methods provided in this application;

[0027] Figure 2 This is a schematic diagram of the printed circuit board provided in this application.

[0028] Figure label:

[0029] 101: Through-hole; 102: Thermal pad area; 103: Chip mounting area;

[0030] 104: Blind hole; 105: Copper sheet. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0032] In the description of the embodiments of this application, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0034] In the embodiments of this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0035] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0036] Semiconductor chips are evolving towards higher integration, higher power, and higher reliability to meet the high-performance requirements of electronic products. As chip power increases while chip size decreases, traditional PCB designs struggle to meet the demands for rapid heat dissipation. Furthermore, if chip heat dissipation is not ideal, it can easily lead to a decline in the chip's electrical performance and instability in the entire electrical system's signals.

[0037] In the PCB design process, the heat dissipation of high-power chips (such as DC-DC power conversion chips and LDO linear regulator chips) is both a key focus and a challenge. It is difficult to balance chip heat dissipation performance and PCB miniaturization in PCB design using related methods.

[0038] like Figure 1 The schematic diagram of the heat dissipation pad area design for the high-power chip provided in this application is shown. In the PCB design of the related method, the heat dissipation pad area of ​​the high-power chip is usually designed by drilling through holes in the area, and then laying copper foil of the same size as the heat dissipation pad on each inner layer of the PCB board. The electrical network of the copper foil is consistent with the network of the heat dissipation pad, which is usually the GND network.

[0039] In PCB design, the primary method for heat dissipation of high-power chips involves using vias on the top and bottom of their thermal pads to transfer heat generated by the chip from the top layer of the PCB to the inner copper layers and the bottom layer. This PCB fabrication method provides some heat dissipation when electronic products operate intermittently, meeting their cooling requirements. However, when electronic products operate continuously 24 hours a day (such as servers and switches), the high-power chips continuously generate heat, causing the overall temperature of the electronic device to rise, with the high-power chip area experiencing even higher temperatures. While the heat is transferred to the inner layers of the PCB through the vias, the limited copper area of ​​the inner layers cannot dissipate the heat effectively, leading to unstable electrical performance due to the high-power chip's inability to dissipate its generated heat.

[0040] Furthermore, in the PCB design of the relevant method, each inner layer below the heat dissipation pad area is covered with copper of the same size and has the same electrical network, which prevents other signal traces from passing through this area. This occupies a large amount of trace space in each layer of the PCB board, which is not conducive to the miniaturization design of the PCB board. As a result, electronic products cannot meet the development needs of miniaturization. At the same time, the increase in PCB board area will lead to an increase in its production cost.

[0041] To address the technical problems in related methods, embodiments of this application provide a printed circuit board, which is described below in conjunction with... Figure 2 The printed circuit board design schematic provided in this application describes in detail the printed circuit board of the embodiments of this application.

[0042] like Figure 2 As shown, the printed circuit board provided in this embodiment includes multiple chip mounting areas 103 and heat dissipation pad areas 102 disposed in each chip mounting area 103; the heat dissipation pad area 102 is provided with multiple through holes 101, and the through holes 101 are located on the bottom surface of the printed circuit board and are provided with blind holes 104. The center of the blind holes 104 coincides with that of the through holes 101, the diameter of the blind holes 104 is larger than the diameter of the through holes 101, and the depth of the blind holes 104 is smaller than the depth of the through holes 101.

[0043] Specifically, in the design process of multiple chip mounting areas 103 of the printed circuit board (PCB), multiple through-holes 101 are first set in the heat dissipation pad area 102 set in each chip mounting area 103. Among them, the heat dissipation pad area 102 is located inside the chip mounting area 103 and is used to dissipate heat from the chip during subsequent chip use.

[0044] Through-hole 101 is a hole that penetrates the top and bottom layers of the printed circuit board. Through-hole 101 will be soldered later. In actual use, through-hole 101 absorbs heat from the chip and dissipates heat to achieve the chip's heat dissipation process.

[0045] Optionally, multiple through-holes 101 can be provided in the heat dissipation pad area 102, which can be obtained by drilling through the top and bottom surfaces of the printed circuit board (PCB) using a conventional drill bit. The location of the through-holes 101 needs to avoid the signal traces of the inner layers of the PCB. The specific number of through-holes 101 can be designed based on the density of other components and signal traces in the surrounding area. If the surrounding signal traces are dense, the number of through-holes can be reduced. The distribution of through-holes can be adjusted according to the other signal traces in the inner layers of the PCB in the heat dissipation pad area 102, thereby increasing the space for other signal traces in the inner layers. If the number of through-holes is reduced, the diameter of the through-holes can be increased accordingly.

[0046] After setting multiple through holes 101 in the heat dissipation pad area 102, blind holes 104 are set on the bottom surface of the printed circuit board where each through hole 101 is located. The centers of the blind holes 104 coincide with those of the through holes 101, the diameter of the blind holes 104 is larger than the diameter of the through holes 101, and the depth of the blind holes 104 is smaller than the depth of the through holes 101. After constructing the through holes 101 and blind holes 104, multiple pyramidal through holes are obtained in the heat dissipation pad area 102. During subsequent chip use, these pyramidal through holes in the heat dissipation pad area 102 absorb and dissipate the chip's heat.

[0047] Optionally, after drilling the top and bottom surfaces of the PCB board to obtain through holes 101 using a conventional drill bit, laser drilling can be used on the bottom surface of the PCB board based on the diameter and depth of the blind holes 104. This is done by using skip vias on the PCB board. The skip via method has higher drilling accuracy and is more conducive to the routing design of other signals in the inner layers of the heat dissipation pad area.

[0048] Understandably, since the diameter of the blind via 104 on the bottom surface of the printed circuit board is larger than the diameter of the through via 101, during subsequent chip use, solder fills both the through via 101 and the blind via 104. The area and volume of solder connected to the chip are significantly larger than those of the solder in the design of similar methods. The thermal conductivity of metal is far higher than that of the PCB material. Furthermore, the larger metal volume of the bottom blind via 104, exposed to the external air, further facilitates heat dissipation through air conduction, resulting in a significant improvement in heat dissipation compared to the inner layers of the PCB.

[0049] The printed circuit board provided in this application increases the area and volume of the metal solder connected to the chip during subsequent chip use by setting multiple through holes in the heat dissipation pad area and blind holes on the bottom surface of the printed circuit board where the through holes are located. At the same time, the larger metal volume of the blind holes on the bottom surface of the printed circuit board, which is exposed to the external air, is more conducive to air conduction heat dissipation, which can quickly dissipate the energy consumption heat of the chip, thereby improving the stability of the chip's electrical performance.

[0050] In one embodiment, a heat dissipation pad area is located on the bottom surface of the printed circuit board, on which a copper sheet 105 is laid, and the copper sheet 105 contacts the blind via 104.

[0051] Optionally, after tinning the through-hole 101 and blind hole 104, copper plating can be performed on the bottom surface of the heat dissipation pad area of ​​the printed circuit board to form a copper sheet 105 on the bottom surface of the heat dissipation pad area of ​​the printed circuit board.

[0052] Understandably, after a copper sheet 105 is laid on the bottom surface of the printed circuit board (PCB) in the heat dissipation pad area, the copper sheet 105 will contact the blind vias 104 on the bottom surface of the PCB because it is directly located on the bottom surface. During subsequent chip use, after solder fills the vias 101 and 104, the solder in the blind vias 104 will contact the copper sheet 105. This allows the heat dissipated by the chip to be conducted through the solder in the vias 101 to the solder in the blind vias 104, and then from the solder in the blind vias 104 to the copper sheet 105 in contact with the blind vias 104, further improving the heat dissipation effect on the chip. At the same time, the large metal area of ​​the bottom copper sheet 105, exposed to the outside air, further facilitates air conduction and heat dissipation.

[0053] The printed circuit board provided in this application lays a copper sheet on the bottom surface of the printed circuit board in the heat dissipation pad area. This allows the heat dissipated by the chip to be conducted through the solder in the through holes to the solder in the blind holes, and then from the solder in the blind holes to the copper sheet in contact with the blind holes. This further improves the heat dissipation effect of the chip. At the same time, the metal area of ​​the bottom copper sheet is large and exposed to the outside air, which is more conducive to air conduction heat dissipation.

[0054] In one embodiment, the diameter of the through hole 101 is 8mil-12mil, and the diameter of the blind hole 104 is twice the diameter of the through hole.

[0055] It should be noted that the diameter of the blind via 104 needs to be larger than the diameter of the through via 101 to enhance heat dissipation. The diameter of the through via 101 is designed based on the density of other devices and signal traces around the chip, typically ranging from 8 mil to 12 mil. The diameter of the blind via 104 is generally twice the diameter of the through via 101 to improve chip heat dissipation while ensuring proper signal routing.

[0056] Optionally, the diameters of the via 101 and the blind via 104 can be designed based on the density of other devices and signal traces in the surrounding area of ​​the chip. If the signal traces in the surrounding area are dense, the number of vias can be reduced. The via distribution can be adjusted according to the other signal traces on the inner layer of the PCB board in the heat sink pad area 102, thereby increasing the space for other signal traces on the inner layer. If the number of vias is reduced, the via diameter can be increased accordingly.

[0057] The printed circuit board provided in this application determines the expected diameter of through holes and blind holes in the printed circuit board by setting the diameter of through holes to 8mil-12mil and the diameter of blind holes to twice the diameter of through holes. This provides a basis for increasing the area and volume of the metal solder connected to the chip in subsequent chip use.

[0058] In one embodiment, when the printed circuit board has ten or more layers, the depth of the blind via 104 is the thickness of four layers; when the printed circuit board has fewer than ten layers, the depth of the blind via 104 is the thickness of two layers.

[0059] After determining the diameter of the blind via, the depth of blind via 104 needs to be further determined. It can be understood that a through-hole is a hole that penetrates through the top and bottom layers of the printed circuit board. Therefore, the diameter of through-hole 101 in the printed circuit board is equal to the thickness of the printed circuit board.

[0060] The depth of the blind via 104 can be determined based on the number of layers in the printed circuit board. When the number of layers in the printed circuit board is greater than or equal to ten, the depth of the blind via 104 is the thickness of four layers; when the number of layers in the printed circuit board is less than ten, the depth of the blind via 104 is the thickness of two layers.

[0061] The printed circuit board (PCB) stack-up includes the power layer, bottom layer, and trace layers. After statistically analyzing all PCB stack-ups, when the PCB stack-up is ten or more layers, the depth of the blind via 104 is selected as the thickness of four layers. This four-layer thickness can be the thickness of the four layers counting backwards from the bottom layer of the PCB.

[0062] When the printed circuit board has fewer than ten layers, the depth of the blind via 104 is equal to the thickness of two layers. The thickness of these two layers can be the thickness of the two layers from the bottom layer of the printed circuit board.

[0063] The printed circuit board provided in this application allows for the determination of the depth of blind vias based on the number of layers in the printed circuit board. When the number of layers in the printed circuit board is ten or more, the depth of the blind via is the thickness of four layers; when the number of layers in the printed circuit board is less than ten, the depth of the blind via is the thickness of two layers. This enables the determination of the expected blind via depth in the printed circuit board, providing a foundation for increasing the area and volume of the metal solder connected to the chip during subsequent chip use.

[0064] In one embodiment, the junction between the inner wall of the through hole 101 and the inner wall of the blind hole 104 in the printed circuit board is a slope.

[0065] In the heat dissipation pad area of ​​the chip mounting area on the printed circuit board, after the vias 101 and blind vias 104 are installed, since the centers of vias 101 and blind vias 104 coincide, there will be an intersection between the inner walls of vias 101 and blind vias 104 inside the printed circuit board. The intersection of the inner walls of vias 101 and blind vias 104 is designed as a bevel.

[0066] It is understandable that by setting a bevel at the junction of the inner walls of through-hole 101 and blind hole 104, the junction of the inner walls of through-hole 101 and blind hole 104 becomes a rhomboid structure. This facilitates the subsequent soldering process of through-hole 101 and blind hole 104.

[0067] The printed circuit board provided in this application has a rhomboid structure at the junction of the inner walls of the through holes and blind holes by setting a bevel at the junction. This facilitates the subsequent soldering process for the through holes and blind holes, improving the efficiency of the soldering process.

[0068] This application also provides a method for manufacturing a printed circuit board, including:

[0069] Multiple through holes 101 are drilled in the heat dissipation pad area 102 of the chip mounting area 103 of the printed circuit board;

[0070] Based on back drilling, multiple blind holes 104 are drilled on the bottom surface of the printed circuit board where the through hole 101 is located. The center of the blind hole 104 coincides with that of the through hole 101. The diameter of the blind hole 104 is larger than that of the through hole 101, and the depth of the blind hole 104 is smaller than that of the through hole 101.

[0071] Specifically, in the design process of multiple chip mounting areas 103 of the printed circuit board (PCB), multiple through-holes 101 are first set in the heat dissipation pad area 102 set in each chip mounting area 103. Among them, the heat dissipation pad area 102 is located inside the chip mounting area 103 and is used to dissipate heat from the chip during subsequent chip use.

[0072] Through-hole 101 is a hole that penetrates the top and bottom layers of the printed circuit board. Through-hole 101 will be soldered later. In actual use, through-hole 101 absorbs heat from the chip and dissipates heat to achieve the chip's heat dissipation process.

[0073] Optionally, multiple through-holes 101 can be drilled in the heat dissipation pad area 102. These can be obtained by drilling through the top and bottom surfaces of the printed circuit board (PCB) using a conventional drill bit. The location of the through-holes 101 should avoid the signal traces on the inner layers of the PCB. The specific number of through-holes 101 can be designed based on the density of other components and signal traces in the surrounding area. If the surrounding signal traces are dense, the number of through-holes can be reduced. The distribution of through-holes can be adjusted according to the other signal traces on the inner layers of the PCB in the heat dissipation pad area 102, thereby increasing the space for these other signal traces. If the number of through-holes is reduced, the diameter of the through-holes can be increased accordingly.

[0074] After creating multiple through-holes 101 in the heat dissipation pad area 102, blind vias 104 are drilled on the bottom surface of the printed circuit board (PCB) where each through-hole 101 is located. The centers of the blind vias 104 and 104 coincide, with the diameter of the blind via 104 being larger than that of the through-hole 101, and the depth of the blind via 104 being less than that of the through-hole 101. After constructing the through-holes 101 and blind vias 104, multiple pyramidal through-holes are obtained in the heat dissipation pad area 102. During subsequent chip use, these pyramidal through-holes in the heat dissipation pad area 102 absorb and dissipate the chip's heat.

[0075] Optionally, after drilling the top and bottom surfaces of the PCB board to obtain through holes 101 using a conventional drill bit, laser drilling can be used on the bottom surface of the PCB board based on the diameter and depth of the blind holes 104. This is done by using skip vias on the PCB board. The skip via method has higher drilling accuracy and is more conducive to the routing design of other signals in the inner layers of the heat dissipation pad area.

[0076] Understandably, since the diameter of the blind via 104 on the bottom surface of the printed circuit board is larger than the diameter of the through via 101, during subsequent chip use, solder fills both the through via 101 and the blind via 104. The area and volume of solder connected to the chip are significantly larger than those of the solder in the design of similar methods. The thermal conductivity of metal is far higher than that of the PCB material. Furthermore, the larger metal volume of the bottom blind via 104, exposed to the external air, further facilitates heat dissipation through air conduction, resulting in a significant improvement in heat dissipation compared to the inner layers of the PCB.

[0077] The printed circuit board fabrication method provided in this application increases the area and volume of the metal solder connected to the chip during subsequent chip use by setting multiple through holes in the heat dissipation pad area and blind holes on the bottom surface of the printed circuit board where the through holes are located. At the same time, the larger metal volume of the blind holes on the bottom surface of the printed circuit board, which is exposed to the external air, is more conducive to air conduction heat dissipation, which can quickly dissipate the energy consumption heat of the chip, thereby improving the stability of the chip's electrical performance.

[0078] In one embodiment, drilling multiple vias 101 in the heat dissipation pad area 102 of the chip mounting area 103 of the printed circuit board includes: determining the number of vias 101 and the positional distribution of the vias 101 in the heat dissipation pad area 102 based on the wiring density and wiring position of the chip mounting area 103; and drilling multiple vias 101 in the heat dissipation pad area 102 based on the number of vias 101 and the positional distribution of the vias 101.

[0079] Understandably, the location of vias 101 needs to avoid the signal traces on the inner layers of the printed circuit board (PCB). The specific number of vias 101 can be designed based on the density of other components and signal traces in the surrounding area. If the surrounding signal traces are dense, the number of vias can be reduced. Based on the trace density and location of the chip mounting area 103, the number and location distribution of vias 101 in the heat sink area 102 are determined. Based on the number and location distribution of vias 101, multiple vias 101 are drilled in the heat sink area 102.

[0080] Based on the routing density and location of the chip surface mount area 103, the via distribution pattern is adjusted to increase the space for other signal traces in the inner layer. If the number of vias is reduced, the via diameter can be increased accordingly.

[0081] The printed circuit board fabrication method provided in this application adjusts the via distribution by adjusting the trace density and position in the chip mounting area, thereby increasing the space for other signal traces in the inner layer and enabling flexible setting of the number and position of vias in the heat dissipation pad area.

[0082] In one embodiment, after drilling a blind hole 104 on the bottom surface of the printed circuit board where the through hole 101 is located, the method further includes: electroplating copper on the bottom surface of the heat dissipation pad area 102 to form a copper sheet 105 on the bottom surface of the heat dissipation pad area 102, the copper sheet 105 being in contact with the blind hole 104.

[0083] Understandably, copper is electroplated onto the bottom surface of the heat dissipation pad area on the printed circuit board (PCB) to form a copper sheet 105 on the bottom surface of the heat dissipation pad area 102. Since the copper sheet 105 is directly located on the bottom surface of the PCB, it will contact the blind vias 104 on the bottom surface of the PCB. During subsequent chip use, after the solder fills the vias 101 and blind vias 104, the solder in the blind vias 104 will contact the copper sheet 105. This allows the heat dissipated by the chip to be conducted through the solder in the vias 101 to the solder in the blind vias 104, and then from the solder in the blind vias 104 to the copper sheet 105 that contacts the blind vias 104, further improving the heat dissipation effect on the chip. At the same time, the large metal area of ​​the bottom copper sheet 105, which is exposed to the outside air, is more conducive to air conduction and heat dissipation.

[0084] When mounting a printed circuit board, the chip heat dissipation pad area 102 can be wave soldered or locally thickened with stencils to increase the amount of solder inside the vias and on the bottom surface, which is beneficial for heat conduction. The inner layer of the chip heat dissipation pad area 102 no longer needs to be covered with a copper layer of the same size, which facilitates the routing of other network signals, allowing other signal traces to pass through, reducing the space required for peripheral signal traces, and further facilitating PCB layout design and PCB miniaturization, ultimately contributing to product miniaturization.

[0085] The method for fabricating a printed circuit board provided in this application lays a layer of copper sheet on the bottom surface of the printed circuit board in the heat dissipation pad area. This allows the heat dissipated by the chip to be conducted through the solder in the through holes to the solder in the blind holes, and then from the solder in the blind holes to the copper sheet in contact with the blind holes. This further improves the heat dissipation effect on the chip. At the same time, the bottom copper sheet has a large metal area and is exposed to the outside air, which is more conducive to air conduction heat dissipation.

[0086] In one embodiment, after copper is electroplated onto the bottom surface of the heat dissipation pad area 102, the method further includes: tinning the through holes 101 and blind holes 104 by wave soldering or stencil soldering, so that the through holes 101 and blind holes 104 are filled with solder, and the contact position between the copper sheet 105 and the blind holes 104 is covered with solder.

[0087] Optionally, if the printed circuit board has a wave soldering process on the bottom layer, the large-diameter holes on the bottom layer of the heat dissipation pad area 102 can be tinned by wave soldering, allowing the solder to flow into and fill the vias. Simultaneously, the copper foil laid on the bottom layer is completely covered with solder. This soldering method ensures that the heat dissipation pad area 102 is fully covered with solder.

[0088] If the printed circuit board does not use wave soldering on the bottom layer, then the bottom layer of the high-power heat dissipation pad area uses an SMD (Surface Mounted Devices) stencil for soldering. Sufficient solder is required here, so the stencil in this area needs to be locally thickened. In standard designs, the stencil thickness is 0.12mm-0.18mm; in this area, the stencil thickness can be made to 0.3mm-0.4mm. The specific stencil thickness in this area can be slightly adjusted based on the number of vias 101 in the heat dissipation pad area 102 and the maximum diameter of the vias, ensuring sufficient solder application.

[0089] The printed circuit board manufacturing method provided in this application tinns through-holes and blind holes by wave soldering or stencil soldering, so that the through-holes and blind holes are filled with solder and the contact area between the copper sheet and the blind hole is covered with solder, thus realizing the tinning process of through-holes and blind holes.

[0090] This application also provides a server, including the printed circuit board provided in the above embodiments. As a component of the server, the printed circuit board has a large metal volume of blind vias on the bottom layer that is exposed to the outside air, which is more conducive to air conduction and heat dissipation, allowing the energy-consuming heat of the chip to be dissipated quickly, thereby improving the stability of the chip's electrical performance.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A printed circuit board, characterized in that, include: Multiple chip mounting areas and heat dissipation pads located in each chip mounting area; The heat dissipation pad area is provided with multiple through holes. The through holes are located on the bottom surface of the printed circuit board and blind holes are provided. The center of the blind holes coincides with that of the through holes. The diameter of the blind holes is larger than that of the through holes, and the depth of the blind holes is smaller than that of the through holes. The heat dissipation pad area is located inside the chip mounting area. The heat dissipation pad area is located on the bottom surface of the printed circuit board and is covered with copper sheets. The copper sheets are in contact with all blind vias. The through vias and blind vias are filled with solder, and the contact points between the copper sheets and the blind vias are covered with solder. The copper sheets are obtained by electroplating copper onto the bottom surface of the heat dissipation pad area on the printed circuit board.

2. The printed circuit board according to claim 1, characterized in that, The diameter of the through hole is 8mil-12mil, and the diameter of the blind hole is twice the diameter of the through hole.

3. The printed circuit board according to claim 2, characterized in that, When the printed circuit board has ten or more layers, the depth of the blind via is the thickness of four layers. When the printed circuit board has fewer than ten layers, the depth of the blind via is equal to the thickness of two layers.

4. The printed circuit board according to claim 1, characterized in that, The junction between the inner wall of the through hole and the inner wall of the blind hole in the printed circuit board is a slope.

5. A method for manufacturing a printed circuit board according to any one of claims 1 to 4, characterized in that, include: Multiple through holes are drilled in the heat dissipation pad area of ​​the chip mounting area on the printed circuit board, wherein the heat dissipation pad area is located inside the chip mounting area; Based on back drilling, a blind hole is drilled on the bottom surface of the printed circuit board where the through hole is located. The center of the blind hole coincides with the center of the through hole. The diameter of the blind hole is larger than the diameter of the through hole, and the depth of the blind hole is smaller than the depth of the through hole. After drilling a blind hole located on the bottom surface of the printed circuit board, the method further includes: Copper is electroplated onto the bottom surface of the heat dissipation pad area to form a copper sheet on the bottom surface of the heat dissipation pad area, and the copper sheet contacts all blind vias. After copper is electroplated onto the bottom surface of the heat dissipation pad area, the process further includes: The through holes and blind holes are tinned using wave soldering or stencil soldering, so that the through holes and blind holes are filled with solder, and the contact area between the copper sheet and the blind hole is covered with solder.

6. The method for manufacturing a printed circuit board according to claim 5, characterized in that, Drilling multiple through-holes in the heat dissipation pad area of ​​the chip mounting area on the printed circuit board includes: Based on the trace density and trace position of the chip mounting area, the number of vias and the positional distribution of the vias in the heat dissipation pad area are determined. Based on the number of through holes and their location distribution, multiple through holes are drilled in the heat dissipation pad area.

7. A server, characterized in that, Including the printed circuit board as described in any one of claims 1 to 4.

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