Multilayer printed circuit board

Abstract

The invention relates to the technical field of printed circuit boards, in particular to a multi-layer printed circuit board, which comprises a circuit board body and is characterized in that the circuit board body comprises a top layer board, a bottom layer board, N core board layers and N-1 separation layers, the top layer board, the bottom layer board and the core board layers are electrically connected, and at least four positioning holes are formed in the board surfaces, fastening bolts and fastening nuts are arranged on the upper sides and the lower sides of the positioning holes; through the arrangement of the positioning holes, the fastening bolts and the buckles, when internal stress is generated in the multi-layer printed circuit board to cause regional deformation of the multi-layer printed circuit board, the inner diameter of the positioning holes is enlarged, and when the locking bolts and the fastening nuts fasten the multi-layer printed circuit board, the buckles are attached to the inner walls of the positioning holes under the extrusion action of the locking bolts, so that the multi-layer printed circuit board is fixed. Therefore, the multi-layer printed circuit board is repositioned and fastened, the accuracy and the stability of the electrical connection positions between the layers of printed circuit boards are ensured, and the product quality and the service life of the multi-layer printed circuit board are ensured.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit boards, in particular to a multi-layer printed circuit board. Background Art

[0002] A multilayer printed circuit board is a circuit board that is composed of three or more circuit layers stacked together and electrically connected through vias. A multilayer printed circuit board makes the wiring in the circuit more compact and is more suitable for circuits that require high density, high stability and high reliability. In existing conventional multilayer printed circuit boards, the connection between the layers of printed circuit boards includes lamination bonding and mechanical connection. Among them, lamination bonding: a resin-impregnated fiber material with bonding function is coated on the surface of each layer of the printed circuit board, and then all the stacked circuit layers are placed in a laminator for heating and pressurization, and finally the bonding of the multilayer printed circuit board is completed to form a stable multilayer structure; mechanical connection: coaxial through holes are set on each layer of the printed circuit board, and fastening bolts are coaxially set in the through holes. The multilayer printed circuit board is clamped with fastening bolts to complete the fastening connection of the multilayer printed circuit board.

[0003] Due to the different materials, thicknesses and bonding qualities of each layer of printed circuit boards, multilayer printed circuit boards are susceptible to internal stress caused by different temperature differences of each layer of printed circuit boards during actual application. For multilayer printed circuit boards made by lamination bonding process, the inner layer of printed circuit boards is susceptible to cracking or breaking due to the internal stress. When the inner layer of printed circuit boards is damaged by short circuit or open circuit, it is not easy to troubleshoot and repair the damaged inner layer of printed circuit boards. The cost of removing and maintaining each layer of printed circuit boards or replacing the entire multilayer printed circuit board is high. For multilayer printed circuit boards made by mechanical connection process, after the inner layer of printed circuit boards is damaged, it is only necessary to release the mechanical fixation, repair or replace the damaged inner layer of printed circuit boards, and then re-fix the multilayer printed circuit boards mechanically to reuse them. The maintenance cost is low. However, after the size of the inner layer of printed circuit boards changes under the action of internal stress, or after replacing the new inner layer of printed circuit boards, the size changes of the original layers of printed circuit boards are inconsistent, which easily causes the electric contacts on each layer of printed circuit boards to be unable to align or offset, thereby causing the signal of the multilayer printed circuit boards after maintenance to fluctuate, and even cause damage to the multilayer printed circuit boards. Summary of the invention

[0004] The object of the present invention is to provide a multi-layer printed circuit board to solve the problem that when the multi-layer printed circuit board is produced by a mechanical connection process, the layers of the printed circuit board are easily deformed due to different deformation amounts, which causes internal stress inside the multi-layer printed circuit board, thereby causing the electrical connection points of the layers of the printed circuit board to shift, causing unstable signals of the printed circuit board and reducing the service life.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A multilayer printed circuit board comprises a circuit board body, wherein the circuit board body comprises a top plate, a bottom plate, N core plate layers and N-1 separation layers, wherein the top plate is located at the uppermost side, the bottom plate is located at the lowermost side, the core plate layer is located between the top plate and the bottom plate, and the separation layer is located between two adjacent core plate layers, the top plate, the bottom plate and the core plate layer are electrically connected, and at least four positioning holes are opened on the board surface, and a plurality of the positioning holes are coaxially arranged with fastening bolts, one end of the fastening bolt is threadedly connected with a fastening nut, and a plurality of buckles are arranged on the fastening nut, and the plurality of buckles are arranged in a circular array along the axis center line of the fastening nut, and the plurality of buckles extend into the positioning hole, the height of the buckle is H1, and the thickness of the circuit board body is B1, wherein H1≥B1, and the buckle is designed so that when the fastening bolt and the fastening nut are threadedly connected, the buckle expands to fit with the inner wall of the positioning hole.

[0007] Preferably, the buckle includes a fastening portion and an elastic portion, the elastic portion is connected to the upper end surface of the fastening nut, the fastening portion is located on the upper side of the elastic portion, the fastening bolt includes a conical surface section and a threaded section, the threaded section is located on the lower side of the fastening bolt, and the threaded section is threadedly connected to the fastening nut, the conical surface section is frustum-shaped, and the small end of the conical surface section is connected to the threaded section, the inner side walls of the plurality of fastening portions are frustum surfaces, and the inner side walls of the plurality of fastening portions have the same taper as the conical surface section, and the wall thickness of the elastic portion is 1 to 3 mm.

[0008] When the top plate, bottom plate, core plate layer and separation layer are bolted together, the clip and locking bolt are inserted into the positioning hole, and the fastening bolt is rotated to engage with the fastening nut for threaded engagement, and the conical surface section of the fastening bolt engages with the conical surface of the fastening portion of the clip. As the threaded connection length of the fastening bolt and the fastening nut increases, the outer diameter of the fastening portion gradually increases until the outer side wall of the fastening portion fits with the inner side wall of the positioning hole, thereby completing the positioning and fastening of the multi-layer printed circuit board by the clip; by arranging the fastening bolt, the fastening nut and the clip, the horizontal position offset between the layers of printed circuit boards caused by the gap between the fastening bolt and the positioning hole is avoided, and since the height H1 of the clip is higher than the thickness B1 of the circuit board body, the outer side wall of the clip can expand to cover the positioning holes of the layers of printed circuit boards, thereby ensuring the accuracy and stability of the electrical connection position between the layers of printed circuit boards, and ensuring the product quality and service life of the multi-layer printed circuit boards.

[0009] Furthermore, in the actual application process, affected by the changes in ambient temperature and factors such as the material of the board material, deformation of each layer of the printed circuit board is likely to occur. Since the thickness and working area of ​​the top board, bottom board, core board layer and separation layer are different, this easily causes differences in the deformation of each layer of the printed circuit board, thereby forming internal stress inside the multi-layer printed circuit board; for this reason, when internal stress is generated inside the multi-layer printed circuit board, causing the multi-layer printed circuit board to warp in a certain area, the inner diameter of the positioning hole is increased by expanding the hole, and the ratio between the inner diameter increment of the positioning hole and the deformation amount of the circuit board with the maximum deformation is 1:2. , through the tapered surface cooperation between the fastening part and the tapered surface section, when the fastening bolt and the fastening nut are threadedly connected, the fastening part is squeezed by the tapered surface section, and the elastic part is elastically deformed. As the threaded cooperation length of the fastening bolt and the fastening nut increases, the outer wall of the fastening part fits with the inner wall of the positioning hole, thereby completing the positioning and fastening of the multi-layer printed circuit board, thereby avoiding the warping deformation caused by the internal stress in the multi-layer printed circuit board due to the difference in the deformation amount of each layer of the printed circuit board, thereby ensuring the accuracy and stability of the electrical connection position between each layer of the printed circuit board, and ensuring the product quality and service life of the multi-layer printed circuit board.

[0010] Preferably, the lower end surface of the head of the fastening bolt and the upper end surface of the fastening nut are both provided with a mounting groove and a plurality of embedded grooves, the plurality of embedded grooves are all connected with the mounting groove, and the plurality of embedded grooves are arranged in a circular array along the axial line of the mounting groove and the outer side of the mounting groove, and the plurality of mounting grooves are each provided with a rubber ring, the rubber ring comprising a mounting portion and an embedded portion, the mounting portion is interference fit in the mounting groove, the embedded portion is located in the embedded groove, the thickness of the rubber ring is B2, the depth of the mounting groove is H2, wherein B2>H2.

[0011] When the fastening bolts and the fastening nuts are threadedly connected, since the positioning between the layers of printed circuit boards is carried out in the horizontal plane, and the fastening between the layers of printed circuit boards is carried out in the vertical direction, and since the outer diameter increment of the buckle is related to the thread matching length of the fastening bolts and the fastening nuts, if the fastening force applied by the fastening bolts and the fastening nuts on the layers of printed circuit boards does not reach the design value after the outer wall of the buckle is fitted with the inner wall of the positioning hole, the fastening effect is poor; if the fastening force of the fastening bolts and the fastening nuts on the layers of printed circuit boards is further increased, the extrusion pressure on the inner wall of the positioning hole exceeds the design value, which is likely to cause the internal stress of the positioning hole to increase or be damaged, and the positioning effect is reduced; if the fastening force applied by the fastening bolts and the fastening nuts on the layers of printed circuit boards reaches the design value When measuring the value, if the extrusion force applied by the buckle on the inner wall of the positioning hole does not reach the design value, the positioning effect is not good. For this reason, by arranging rubber rings on both the fastening bolts and the fastening nuts, the length accuracy requirement of the fastening bolts is reduced. After the fastening force applied by the fastening bolts and the fastening nuts on each layer of the printed circuit board reaches the fastening requirement, the thread matching length of the fastening bolts and the fastening nuts is continued to increase. During the process, the rubber ring absorbs the increased fastening force and converts it into the deformation of the rubber ring until the extrusion force applied by the buckle on the inner wall of the positioning hole reaches the design value. The fastening bolts and the fastening nuts complete the positioning and fastening of the multi-layer printed circuit board, thereby ensuring the accuracy and stability of the electrical connection positions between the layers of the printed circuit boards, and ensuring the product quality and service life of the multi-layer printed circuit boards.

[0012] Furthermore, compared with the spring washer, the rubber ring is provided with a mounting portion and an embedding portion, the contact area between the rubber ring and the multilayer printed circuit board is larger, and under the condition of satisfying elastic compensation, the impact resistance of the rubber ring and the multilayer printed circuit board is better than that of the spring washer, and the friction between the rubber ring and the multilayer printed circuit board is greater than that of the spring washer. Under vibration conditions, it is more conducive to the non-return of the fastening bolts and the fastening nuts, thereby ensuring the fastening effect of the fastening bolts and the fastening nuts on the multilayer printed circuit board, and ensuring the product quality and service life of the multilayer printed circuit board.

[0013] Preferably, the top plate, bottom plate, core plate layer and separation layer are each provided with a plurality of through holes, a plurality of the through holes are each provided with an electroplating ring, a plurality of the electroplating rings are each provided with a resin filler, a plurality of the electroplating rings are welded with a cap at the upper end or the lower end, and the top plate, bottom plate and core plate layer are electrically connected via the electroplating rings and the caps.

[0014] Electrical connection between layers is achieved by arranging electroplating rings and caps on the top board, bottom board, core board layer and separation layer. Since the top board, bottom board, core board layer and separation layer are produced in layers and then locked by fastening bolts and fastening nuts to form a multi-layer printed circuit board, the through holes on each layer of the printed circuit board are all through holes, which is conducive to the processing of the through holes, reduces the processing difficulty, and helps to reduce the processing cost; further, by arranging resin fillers in the electroplating rings, the structural strength of the through holes is increased, the probability of damage or cracking of the through holes due to vibration or impact is reduced, and the overall reliability of the multi-layer printed circuit board is improved. At the same time, the resin filler reduces the air gap in the through hole, which helps to reduce signal and noise interference.

[0015] Preferably, at least one group of coaxial through holes is provided on the top plate, bottom plate, core plate layer and separation layer, and the electroplated rings in the coaxial through holes are electrically connected through caps on upper and lower sides.

[0016] When the top board and the bottom board are electrically connected, the electrical connection between the top board and the bottom board is completed through the coaxial through holes set on each layer of the printed circuit board, combined with the electroplating ring and the cap; compared with the multi-layer printed circuit board produced by the lamination bonding process, the through holes of the multi-layer printed circuit board using the lamination bonding process can only be processed after the multi-layer printed circuit board completes all the lamination, and the processing technology of the through holes can only be in the form of drill processing to ensure that the inner diameter of the previous through hole is consistent, and the smaller the diameter of the through hole, the higher the processing cost; and the multi-layer printed circuit board produced by the present technical solution, because the through holes on each layer are all through holes, and the thickness of each layer of the printed circuit board is relatively thick The through hole processing technology can be laser processing to obtain a lower cost through hole diameter under the condition of the same through hole inner diameter. The reduction of the through hole diameter is conducive to denser wiring, thereby improving the design flexibility and wiring density of the circuit board; and the through hole formed by laser drilling helps to improve the flatness of the hole wall and the electroplating quality, thereby improving the stability of the electroplating ring in the through hole and ensuring the stability of the electrical connection between each layer of the printed circuit board; further, the smaller the diameter of the through hole, the more conducive it is to reduce the interference on the signal transmission path, reduce the parasitic capacitance and parasitic inductance of the through hole, and improve the signal stability and response speed of the multi-layer printed circuit board in high-frequency transmission.

[0017] Preferably, at least one group of coaxial through holes is provided on the top plate, bottom plate, core plate layer and separation layer, and no resin filler is provided in the electroplated rings in the coaxial through holes, and copper rivets are riveted in the electroplated rings in the coaxial through holes.

[0018] For rectangular multilayer printed circuit boards or multilayer printed circuit boards with different length-to-width ratios greater than 1.5, since the fastening area of ​​each set of fastening bolts and fastening nuts is limited, if positioning holes, fastening bolts and fastening nuts are only set at the four corners of the multilayer printed circuit board, the fastening effect of the middle part of the multilayer printed circuit board may not meet the fastening requirements; the fastening of the middle part of the multilayer printed circuit board can be strengthened by increasing the number of positioning holes, but the additional positioning holes, fastening bolts and fastening nuts will increase the production cost of the multilayer printed circuit board; for this reason, coaxial through holes are set on each layer of the printed circuit board, and the through hole structure is set in the middle position of the multilayer printed circuit board as much as possible, and copper rivets are riveted in the coaxial through holes. Through the restrictive effect of the copper rivets on the multilayer printed circuit board, the fitting effect of the middle area of ​​the multilayer printed circuit board is improved, thereby ensuring the accuracy and stability of the electrical connection position between each layer of the printed circuit board, and ensuring the product quality and service life of the multilayer printed circuit board; when the multilayer printed circuit board is inspected or maintained, the rivet head at one end or both ends of the copper rivet only needs to be removed to remove the restrictive effect of the copper rivet on the multilayer printed circuit board.

[0019] Preferably, gaskets are provided on the upper end surfaces of the bottom plate, core plate layer and separation layer in an area 1 to 2 mm away from the outer edge, the gaskets are all closed, and the gaskets are made of elastic material. Under pressure-free conditions, the height of the gasket is higher than the height of the cap, and the inner side of the upper end surface of the gasket is provided with a groove.

[0020] By arranging gaskets between the top board, the bottom board, the core board layer and the separation layer, hard contact between the layers of printed circuit boards is avoided, and soft contact is achieved between the layers of printed circuit boards, thereby improving the seismic resistance and impact resistance of the multi-layer printed circuit board; at the same time, the annular sealing gasket can prevent dust or water vapor in the environment from entering the gaps between the layers of printed circuit boards, thereby ensuring the stability and service life of the multi-layer printed circuit board.

[0021] Preferably, a groove is provided on the inner side of the upper end surface of the gasket, the slope of the groove is 45°, and the ratio of the groove width to the gasket thickness is 1:2; by setting the rubber ring and the gasket, the space between each layer of the printed circuit board is a closed structure, and during the operation of the multi-layer printed circuit board, the temperature of the core board layer rises, causing the temperature of the gas in the gap between each layer of the printed circuit board to rise and expand, combined with the setting of the groove, the contact area between the upper end surface of the gasket and the top board, the core board layer or the separation layer is small, and the groove has a diversion effect, and the high-temperature gas in the gap between each layer of the printed circuit board passes through the groove and the top board, the core board layer, and the separation layer. The gas outside the multi-layer printed circuit board is discharged from the mating place of the gasket and the top layer or the separation layer. After the temperature of the multi-layer printed circuit board drops, it is not easy for the gas outside the multi-layer printed circuit board to enter the multi-layer printed circuit board from the mating surface between the gasket and the top layer, the core layer or the separation layer, thereby causing the gas pressure inside the multi-layer printed circuit board to be lower than the atmospheric pressure, which is beneficial to improving the fit between the layers of printed circuit boards. The gas density inside the multi-layer printed circuit board is relatively high and the air density is low. When the multi-layer printed circuit board is working, it is beneficial to reduce the heat conduction between the layers of printed circuit boards and reduce the temperature influence between the layers of printed circuit boards, thereby improving the stability of the multi-layer printed circuit board.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention provides positioning holes, fastening bolts and buckles. When internal stress is generated inside the multilayer printed circuit board and causes regional deformation of the multilayer printed circuit board, the inner diameter of the positioning hole is enlarged. When the locking bolt and the fastening nut are used to fasten the multilayer printed circuit board, the fastening portion fits with the inner wall of the positioning hole under the extrusion of the conical surface section, thereby completing the repositioning and fastening of the multilayer printed circuit board, avoiding the warping deformation caused by the internal stress in the multilayer printed circuit board due to the difference in the deformation amount of each layer of the printed circuit board, thereby ensuring the accuracy and stability of the electrical connection position between each layer of the printed circuit board, and ensuring the product quality and service life of the multilayer printed circuit board.

[0024] 2. The present invention provides rubber rings on both the fastening bolts and the fastening nuts. After the fastening force applied by the fastening bolts and the fastening nuts on each layer of the printed circuit board reaches the fastening requirement, the thread matching length of the fastening bolts and the fastening nuts is continuously increased, and the rubber ring absorbs the increased fastening force and deforms until the extrusion force applied by the buckle on the inner wall of the positioning hole reaches the design value, thereby completing the positioning and fastening of the multi-layer printed circuit board by the fastening bolts and the fastening nuts, thereby ensuring the accuracy and stability of the electrical connection position between each layer of the printed circuit board, and ensuring the product quality and service life of the multi-layer printed circuit board.

[0025] 3. The present invention provides washers between the layers of printed circuit boards, so that the layers of printed circuit boards are in soft contact, thereby improving the seismic resistance and impact resistance of the multi-layer printed circuit board; combined with the groove design on the washers and the setting of the rubber rings, the gaps between the layers of printed circuit boards are sealed, and the gas in the multi-layer printed circuit board is expanded and discharged when working. The gas density inside the multi-layer printed circuit board is relatively large and the air density is relatively low. When the multi-layer printed circuit board is working, it is beneficial to reduce the heat conduction between the layers of printed circuit boards and reduce the temperature influence between the layers of printed circuit boards, thereby improving the stability of the multi-layer printed circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the overall structure of the multilayer printed circuit board in the present invention;

[0027] Figure 2 An exploded view of a multi-layer printed circuit board in the present invention;

[0028] Figure 3 A top view of a multi-layer printed circuit board in the present invention;

[0029] Figure 4 for Figure 3 Full section view at AA in the middle;

[0030] Figure 5 for Figure 4 A partial enlarged view of point C in the middle;

[0031] Figure 6 A schematic diagram of a printed circuit board via structure in another embodiment of a multi-layer printed circuit board of the present invention;

[0032] Figure 7 for Figure 3 Full section view at the middle BB;

[0033] Figure 8 It is an exploded view of the fastening bolts and fastening nuts of the multi-layer printed circuit board in the present invention.

[0034] In the figure: 1. circuit board body; 11. top board; 111. top signal layer; 112. No. 1 substrate layer; 12. upper core board layer; 121. upper ground layer; 122. No. 2 substrate layer; 123. middle signal layer; 13. separation layer; 14. lower core board layer; 141. power layer; 142. No. 3 substrate layer; 143. lower ground layer; 15. bottom board; 151. No. 4 substrate layer; 152. bottom signal layer; 16. positioning hole; 17. electroplating ring; 18. resin filler; 19. cap; 2. fastening bolt; 21. conical section; 22. threaded section; 23. mounting groove; 24. embedded groove; 3. fastening nut; 31. buckle; 311. fastening part; 312. elastic part; 4. rubber ring; 41. mounting part; 42. embedded part; 5. rivet; 6. washer. DETAILED DESCRIPTION

[0035] See also Figures 1 to 8 The following describes two specific embodiments of the present invention in conjunction with the accompanying drawings. A multilayer printed circuit board provided by the present invention is as follows:

[0036] As a specific embodiment of the present invention, a square six-layer printed circuit board is provided, wherein the overall size of the multi-layer printed circuit board is 70mm*70mm*7.5mm, the area size of the copper area of ​​each layer of the printed circuit board is 60mm*60mm, and the width of the copper-free area in the four horizontal directions of each layer of the printed circuit board is 5mm.

[0037] For details, please refer to Figure 4 and Figure 5, including a circuit board body 1, the circuit board body 1 includes a top board 11, a bottom board 15, two core board layers and a separation layer 13, the top board 11 is located at the uppermost side, the bottom board 15 is located at the lowermost side, the two core board layers are located between the top board 11 and the bottom board 15, and the separation layer 13 is located between two adjacent core board layers; wherein the top board 11 includes a top signal layer 111 and a No. 1 substrate layer 112, the top signal layer is located on the upper surface of the No. 1 substrate layer 112, and the two are connected by a lamination bonding process; the two core board layers include an upper core board layer 12 and a lower core board layer 14, the upper core board layer 12 includes an upper grounding layer 121, a No. 2 substrate layer 122 and a middle signal layer 123, the three are arranged from top to bottom, and the three are connected by a lamination bonding process The lower core board layer 14 includes a power layer 141, a third substrate layer 142 and a lower ground layer 143, which are arranged from top to bottom and connected by a lamination bonding process; the bottom board 15 includes a fourth substrate layer 151 and a bottom signal layer 152, and the fourth substrate layer 151 is located on the upper surface of the bottom signal layer 152, and the two are connected by a lamination bonding process; the first substrate layer 112, the second substrate layer 122, the third substrate layer 142, the fourth substrate layer 151 and the separation layer 13 are all made of polyimide, and the thickness of the first substrate layer 112 and the fourth substrate layer 151 is 0.8mm, the thickness of the second substrate layer 122 and the third substrate layer 142 is 0.5mm, and the thickness of the separation layer 13 is 1.0mm.

[0038] See also Figure 1 , Figure 2 and Figure 8, four positioning holes 16 are provided on the top plate 11, the upper core plate layer 12, the separation layer 13, the lower core plate layer 14 and the bottom plate 15, and the four positioning holes 16 are respectively located at the four corners of the board surface, and the distance from the axis of the positioning hole 16 to the outer edge of the printed circuit board is 2.5 mm, and the diameter of the positioning hole 16 is 3.0 mm. A fastening bolt 2 is coaxially arranged in the four positioning holes 16, and the fastening bolt 2 is inserted into the positioning hole 16 from top to bottom. The lower end of the fastening bolt 2 is threadedly connected with a fastening nut 3, and four buckles 31 are provided on the upper end surfaces of the four fastening nuts 3, and the four buckles 31 are arranged in a circular array along the axis of the fastening nut 3, and multiple buckles 31 extend into the positioning hole 16, and the buckles 31 The height is 7.8mm, and the outer diameter of the virtual circle of the four buckles 31 is 3.0mm; the buckle 31 includes a fastening portion 311 and an elastic portion 312, the elastic portion 312 is connected to the upper end surface of the fastening nut 3, the fastening portion 311 is located on the upper side of the elastic portion 312, the fastening bolt 2 includes a conical surface section 21 and a threaded section 22, the threaded section 22 is located on the lower side of the fastening bolt 2, and the threaded section 22 is threadedly connected to the fastening nut 3, the conical surface section 21 is frustum-shaped, and the taper is 1:10, and the small end of the conical surface section 21 is connected to the threaded section 22, the inner side walls of multiple fastening portions 311 are frustum surfaces, and the inner side walls of multiple fastening portions 311 have the same taper as the conical surface section 21, and the wall thickness of the elastic portion 312 is 1.0mm.

[0039] For further information, see Figure 2 , Figure 7 and Figure 8 The lower end surface of the head of the fastening bolt 2 and the upper end surface of the fastening nut 3 are both provided with a mounting groove 23 and a plurality of embedded grooves 24. The plurality of embedded grooves 24 are all connected with the mounting groove 23, and the plurality of embedded grooves 24 are arranged in a circular array along the axis of the mounting groove 23 and the outer side of the mounting groove 23. The plurality of mounting grooves 23 are each provided with a rubber ring 4. The rubber ring 4 includes a mounting portion 41 and an embedded portion 42. The mounting portion 41 is interference-fitted in the mounting groove 23, and the embedded portion 42 is located in the embedded groove 24. The thickness of the rubber ring 4 is 1 mm, and the depth of the mounting groove 23 is 0.8 mm.

[0040] See also Figures 3 to 5 A plurality of through holes are provided on the top board 11, the upper core board layer 12, the separation layer 13, the lower core board layer 14 and the bottom board 15, the inner diameter of the through holes is 0.3 mm, and electroplating rings 17 are provided in the plurality of through holes, and resin fillers 18 are provided in the plurality of electroplating rings 17, and caps 19 are welded on the upper and lower ends of the plurality of electroplating rings 17, and the electrical connections between at least two layers among the top signal layer 111, the upper ground layer 121, the middle signal layer 123 and the power layer 141, the lower ground layer 143 and the bottom signal layer 152 are completed by the electroplating rings 17 and the caps 19 (due to limited drawing, all electrical connection forms between the layers are not shown in the figure).

[0041] For further information, see Figure 5 When vias are designed on the circuit board body 1, at least one set of coaxial through holes is provided on the top board 11, the upper core board layer 12, the separation layer 13, the lower core board layer 14 and the bottom board 15. The electroplated rings 17 in the coaxial through holes are electrically connected through the caps 19 on the upper and lower sides, thereby completing the electrical connection from the top signal layer 111 to the bottom signal layer 152.

[0042] See also Figure 2 and Figure 7 The upper end surfaces of the bottom plate 15, the lower core plate layer 14, the partition layer 13 and the upper core plate layer 12 are all provided with gaskets 6, the gaskets 6 are in a closed ring shape, and the gaskets 6 are made of elastic material. Under pressure-free conditions, the thickness and height of the gaskets 6 are both 0.3mm, the distance from the outer edge of the gasket 6 to the outer edge of the circuit board body 1 is 1mm, the height of the cap 19 is 0.25mm, and the inner side of the upper end surface of the gasket 6 is provided with a 45° groove, and the groove width is 0.15mm.

[0043] When fastening the circuit board body 1, the top plate 11, the upper core plate layer 12, the partition layer 13, the lower core plate layer 14 and the bottom plate 15 are arranged in a top-down order, and the four positioning holes 16 are aligned, the buckle 31 is inserted into the positioning hole 16, and then the fastening bolt 2 is inserted into the positioning hole 16, and the fastening bolt 2 is rotated clockwise until the fastening bolt 2 presses the top plate 11, the upper core plate layer 12, the partition plate, the lower core plate layer 14 and the bottom plate 15, the washer 6 is elastically deformed under the locking force of the fastening bolt 2, the height of the washer 6 becomes lower, and the adjacent two layers of circuit boards are electrically connected through the cap 19, and the rubber ring 4 is elastically deformed under the locking force of the fastening bolt 2, thereby completing the locking of the fastening bolt 2 on each layer of printed circuit boards; when the circuit board is overhauled or maintained, the four fastening bolts 2 are rotated counterclockwise until the fastening bolts 2 are disengaged from the fastening nuts 3, thereby releasing the locking effect between the layers of printed circuit boards.

[0044] See also Figure 6As another specific embodiment of the present invention, a rectangular six-layer printed circuit board is provided, wherein the overall size of the printed circuit board is 70mm*130mm*7.5mm, the area size of the copper area of ​​the printed circuit board is 60mm*120mm, and the width of the copper-free area in four horizontal directions of the printed circuit board is 5mm. Different from the previous specific embodiment, the length of the six-layer printed circuit board provided by this specific embodiment is longer than that of the previous specific embodiment, in order to avoid the circuit board body 1 being affected by external factors such as temperature changes, environmental vibrations or material expansion during actual application, resulting in excessive spacing between the layers of the printed circuit board; for this purpose, vias must be provided on the circuit board body 1, and at least one group of coaxial through holes is provided on the top board 11, the upper core board layer 12, the separation layer 13, the lower core board layer 14 and the bottom board 15, and the electroplating ring 17 in the coaxial through hole is not provided with a resin filler 18, and the electroplating ring 17 in the coaxial through hole is riveted with a copper rivet 5, and the vias need to be provided in the middle area of ​​the circuit board.

[0045] When fastening the circuit board body 1, the top plate 11, the upper core plate layer 12, the separation layer 13, the lower core plate layer 14 and the bottom plate 15 are arranged in a top-to-bottom order, and the four positioning holes 16 are aligned, and the copper rivet 5 is riveted to the coaxial through holes on the top plate 11, the upper core plate layer 12, the separation layer 13, the lower core plate layer 14 and the bottom plate 15, and the upper and lower ends of the copper rivet 5 are rivet-shaped, thereby completing the pre-locking of the copper rivet 5 on each layer of the printed circuit board; insert the buckle 31 into the positioning hole 16, and then insert the fastening bolt 2 into the positioning hole 16, and turn the fastening bolt 2 clockwise until the fastening bolt 2 fixes the top plate 11, the upper core plate layer 12, the separation layer 13, the lower core plate layer 14 and the bottom plate 15. The partition, the lower core board layer 14 and the bottom board 15 are pressed together, and the gasket 6 is elastically deformed under the locking force of the fastening bolt 2, the height of the gasket 6 becomes lower, and the two adjacent layers of circuit boards are electrically connected through the cap 19. The rubber ring 4 is elastically deformed under the locking force of the fastening bolt 2, thereby completing the locking of the fastening bolt 2 on each layer of printed circuit boards; when the circuit board is overhauled or maintained, it is necessary to use a drill to drill out the upper end or the upper and lower ends of the copper rivet 5, and after releasing the locking effect of the copper rivet 5 on each layer of printed circuit boards, turn the four fastening bolts 2 counterclockwise until the fastening bolts 2 are disengaged from the fastening nuts 3, thereby releasing the locking effect between the layers of printed circuit boards.

[0046] The above two specific embodiments of the present invention are described in detail in conjunction with the accompanying drawings, but the present invention is not limited to the embodiments described above. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments without departing from the principles and ideas of the present invention should still fall within the scope of protection of the present invention.

Claims

1. A multilayer printed circuit board, comprising a circuit board body (1), characterized in that: The circuit board body (1) comprises a top board (11), a bottom board (15), N core board layers and N-1 separation layers (13), wherein the top board (11) is located at the uppermost side, the bottom board (15) is located at the lowermost side, the core board layer is located between the top board (11) and the bottom board (15), the separation layer (13) is located between two adjacent core board layers, the top board (11), the bottom board (15) and the core board layer are electrically connected, and at least four positioning holes (16) are provided on the board surface, and a plurality of the positioning holes (16) are coaxially provided with fastening bolts (2), so that One end of the fastening bolt (2) is threadedly connected to a fastening nut (3), and a plurality of buckles (31) are provided on the fastening nut (3). The plurality of buckles (31) are arranged in a circular array along the axis of the fastening nut (3), and the plurality of buckles (31) all extend into the positioning hole (16). The height of the buckle (31) is H1, and the thickness of the circuit board body (1) is B1, wherein H1≥B1. The buckle (31) is designed such that when the fastening bolt (2) and the fastening nut (3) are threadedly connected, the buckle (31) expands to fit the inner wall of the positioning hole (16).

2. A multilayer printed circuit board according to claim 1, characterized in that: The buckle (31) comprises a fastening portion (311) and an elastic portion (312), wherein the elastic portion (312) is connected to the upper end surface of the fastening nut (3), and the fastening portion (311) is located on the upper side of the elastic portion (312). The fastening bolt (2) comprises a conical section (21) and a threaded section (22), wherein the threaded section (22) is located on the lower side of the fastening bolt (2), and the threaded section (22) is threadedly connected to the fastening nut (3). The conical section (21) is in a frustum shape, and the small end of the conical section (21) is connected to the threaded section (22). The inner side walls of the plurality of fastening portions (311) are frustum surfaces, and the inner side walls of the plurality of fastening portions (311) have the same taper as the conical section (21), and the wall thickness of the elastic portion (312) is 1 to 3 mm.

3. A multilayer printed circuit board according to claim 2, characterized in that: The lower end surface of the head of the fastening bolt (2) and the upper end surface of the fastening nut (3) are both provided with a mounting groove (23) and a plurality of embedded grooves (24); the plurality of embedded grooves (24) are all connected to the mounting groove (23), and the plurality of embedded grooves (24) are arranged in a circular array along the axis of the mounting groove (23) and the outer side of the mounting groove (23); a rubber ring (4) is provided in each of the plurality of mounting grooves (23); the rubber ring (4) comprises a mounting portion (41) and an embedded portion (42); the mounting portion (41) is interference-fittedly mounted in the mounting groove (23); the embedded portion (42) is located in the embedded groove (24); the thickness of the rubber ring (4) is B2, and the depth of the mounting groove (23) is H2, wherein B2>H2.

4. A multilayer printed circuit board according to claim 1, characterized in that: The top plate (11), the bottom plate (15), the core plate layer and the separation layer (13) are all provided with a plurality of through holes, each of the plurality of through holes is provided with an electroplating ring (17), each of the plurality of electroplating rings (17) is provided with a resin filler (18), and each of the plurality of electroplating rings (17) is welded with a cap (19) at the upper and lower ends, and the top plate (11), the bottom plate (15) and the core plate layer are all electrically connected via the electroplating ring (17) and the cap (19).

5. A multilayer printed circuit board according to claim 4, characterized in that: At least one group of coaxial through holes is provided on the top plate (11), the bottom plate (15), the core plate layer and the separation layer (13), and the electroplated rings (17) in the coaxial through holes are electrically connected via caps (19) on the upper and lower sides.

6. A multilayer printed circuit board according to claim 4, characterized in that: At least one group of coaxial through holes is provided on the top plate (11), the bottom plate (15), the core plate layer and the separation layer (13); the electroplated ring (17) in the coaxial through hole is not provided with a resin filler (18); and the electroplated ring (17) in the coaxial through hole is riveted with a copper rivet (5).

7. A multi-layer printed circuit board according to claim 3, characterized in that: Gaskets (6) are provided on the upper end surfaces of the bottom plate (15), the core plate layer and the separation layer (13) in an area 1 to 2 mm away from the outer edge. The gaskets (6) are all closed and made of elastic material. Under no-pressure conditions, the height of the gaskets (6) is higher than the height of the cap (19).

8. A multi-layer printed circuit board according to claim 1, characterized in that: The inner side of the upper end surface of the gasket (6) is provided with a groove, the slope of the groove is 45°, and the ratio of the groove width to the thickness of the gasket (6) is 1:2.

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