A low-impedance multilayer circuit board and a manufacturing process thereof

Abstract

This invention discloses a low-impedance multilayer circuit board and its manufacturing process, belonging to the field of multilayer circuit boards. The device includes a substrate with connecting tenons protruding at both ends for snap-fitting. Both ends of a first solder mask layer and a second solder mask layer are provided with mortises. The connecting tenons and mortises interlock. High thermal conductivity insulating resin is alternately disposed at both ends of the mortises to interlock the interlocking action between the first solder mask layer, the second solder mask layer, and the substrate. By employing the interlocking design of the connecting tenons and mortises, combined with the secondary positioning of the limiting protrusions and mortises, displacement of the thermally conductive material and solder mask layer is effectively prevented during lamination. Simultaneously, high thermal conductivity insulating resin is injected through the first and second filling grooves, and after curing, an interlocking structure is formed, enhancing the bonding strength between the first solder mask layer, the second solder mask layer, and the substrate, resisting shear stress caused by differences in thermal expansion coefficients, and improving the overall structural reliability and heat dissipation alignment accuracy.

Description

Technical Field

[0001] This invention relates to the field of multilayer circuit boards, and in particular to a low-impedance multilayer circuit board and its manufacturing process. Background Technology

[0002] A specially designed printed circuit board employs specific stack-up structures, materials, wiring processes, and termination techniques to rigorously control the impedance of signal paths (especially power / ground loops) and stabilize them at low values ​​(typically in the range of 10Ω to 50Ω) in complex multilayer PCBs. Its purpose is to provide a smooth and stable current loop for high-speed signals, minimizing power supply noise, signal integrity issues (such as reflections and crosstalk), and electromagnetic interference.

[0003] As electronic devices develop towards high performance, high integration, and miniaturization, their power density continues to increase. Heat dissipation has become a key bottleneck restricting further breakthroughs in equipment reliability, lifespan, and performance. In order to effectively manage heat, modern high-end multilayer circuit boards (PCBs) have evolved from traditional passive heat dissipation to active and integrated heat dissipation designs. In the current PCB manufacturing process, high thermal conductivity metal blocks (such as copper and aluminum blocks), heat spreaders, or other heterogeneous heat dissipation structures are directly embedded into the board to construct an ultra-short, low thermal resistance path from the heat source to the heat dissipation interface.

[0004] In summary, existing technologies typically place the thermally conductive structure within a pre-milled cavity on the PCB core board. Subsequently, the resin flow of the prepreg during lamination encapsulates and cures the structure. Under the high temperature and pressure conditions applied during lamination, the thermally conductive structure is prone to sliding or shifting within the cavity, leading to misalignment with the designed heat source position and severely impacting heat dissipation efficiency. Furthermore, relying solely on the adhesive force of the resin is insufficient to resist the enormous shear stress generated by the mismatch in thermal expansion coefficients between the metal and the PCB material.

[0005] Invention Content This invention provides a low-impedance multilayer circuit board and its manufacturing process, which can solve the problem in the prior art where the heat-conducting structure is usually placed in a pre-milled cavity of the PCB core board, and then wrapped and cured by the resin flow of the prepreg during the lamination process. Under the high temperature and high pressure environment applied during lamination, the heat-conducting structure is prone to sliding or shifting in the cavity, resulting in misalignment with the designed heat source position and seriously affecting the heat dissipation efficiency.

[0006] A low-impedance multilayer circuit board includes a circuit board body for providing mechanical support and electrical insulation. The circuit board body includes a substrate. The substrate has protruding connecting tenons at both ends for snap-fitting. A first solder mask layer and a second solder mask layer are symmetrically disposed on the front and back of the substrate. Both ends of the first solder mask layer and the second solder mask layer are provided with mortises. The connecting tenons and mortises are interlocked. The two ends of the mortises are alternately provided with high thermal conductivity insulating resin for interlocking the interlocking action between the first solder mask layer, the second solder mask layer and the substrate.

[0007] Preferably, thermally conductive vias are uniformly formed on the surfaces of the first and second solder resist layers, and limiting grooves for limiting are formed on both the front and back sides of the first solder resist layer.

[0008] Preferably, the limiting groove is embedded with a heat-conducting material for heat dissipation, and the surface of the heat-conducting material has a plurality of copper pillars for conducting heat. Preferably, the two sides of the connecting tenon are provided with staggered first filling grooves, and the inner walls of the tenon are provided with corresponding second filling grooves. The high thermal conductivity insulating resin is filled at the connection between the substrate and the first solder resist layer and the second solder resist layer through the second filling groove and the first filling groove.

[0009] Preferably, one end of the connecting tenon is provided with a groove, and one end of the groove is provided with a limiting protrusion, which is engaged inside the groove.

[0010] A fabrication process for a low-impedance multilayer circuit board includes the following steps: S1. Prepare a substrate, process connecting tenons at both ends, and open the first filling groove on both sides of the tenons; S2. Make the first solder resist layer and the second solder resist layer respectively, and make mortise grooves at both ends of the first solder resist layer and the second solder resist layer respectively, and make second filling grooves on both sides of the inner wall of the mortise grooves. S3. The first and second solder resist layers are symmetrically attached to both sides of the substrate so that the connecting tenon is embedded in the tenon groove. S4. Embed thermally conductive material in the limiting groove so that the copper pillars on its surface face outwards; S5. High thermal conductivity insulating resin is injected through the corresponding positions of the first filling groove and the second filling groove, and an interlocking structure is formed after curing. S6. Perform lamination, drilling, electroplating, and pattern transfer to complete the fabrication of the multilayer circuit board.

[0011] Preferably, one end of the connecting tenon is also provided with a groove, and one end of the groove is provided with a matching limiting protrusion, which is engaged with the groove during assembly.

[0012] Preferably, the heat-conducting material is a copper block or an aluminum block, the surface of which is formed with multiple copper pillars by stamping or etching to increase the heat dissipation area.

[0013] Preferably, the high thermal conductivity insulating resin is an epoxy resin filled with aluminum nitride or aluminum oxide particles, which forms a mechanical interlock and thermal conduction path after curing.

[0014] Preferably, in step S5, after injecting the high thermal conductivity insulating resin, a vacuum-assisted process is used to remove air bubbles.

[0015] Beneficial effects: 1. This invention employs a tenon and mortise interlocking design, combined with secondary positioning using limiting protrusions and slots, to effectively prevent the thermally conductive material and solder resist layer from shifting during the lamination process. Simultaneously, by injecting highly thermally conductive insulating resin into the first and second filling slots, an interlocking structure is formed after curing, enhancing the bonding strength between the first and second solder resist layers and the substrate, resisting shear stress caused by differences in thermal expansion coefficients, and improving the overall structural reliability and heat dissipation alignment accuracy.

[0016] This invention achieves efficient heat conduction by setting thermally conductive materials and copper pillars in the first and second solder resist layers, and forming a continuous heat dissipation path through thermally conductive vias and high thermal conductivity insulating resin. While improving heat dissipation performance, it maintains the low impedance characteristics of the multilayer circuit board, which is beneficial to the integrity of high-speed signal transmission, reduces power supply noise and electromagnetic interference, and makes the application range of multilayer circuit boards wider. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the overall structure of a low-impedance multilayer circuit board and its manufacturing process provided by the present invention. Figure 2 A side view of a low-impedance multilayer circuit board and its fabrication process provided by the present invention. Figure 3 A disassembled view of the overall structure of a low-impedance multilayer circuit board and its manufacturing process provided by the present invention. Figure 4 A schematic diagram of the top structure of a low-impedance multilayer circuit board and its manufacturing process provided by the present invention. Figure 5 This is an enlarged view of the structure at point A of a low-impedance multilayer circuit board and its manufacturing process provided by the present invention. Explanation of reference numerals in the attached figures: 1. Circuit board body; 100. Substrate; 1010. Limiting groove; 1001. Slot; 1002. Connecting tenon; 1003. First filling groove; 101. First solder mask layer; 102. Second solder mask layer; 1020. Thermally conductive via; 1011. Tenon groove; 1012. Limiting protrusion; 1013. Second filling groove; 103. Thermally conductive material; 1030. Copper pillar; 104. High thermal conductivity insulating resin. Detailed Implementation

[0019] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0020] like Figures 1 to 5 As shown in the figure, an embodiment of the present invention provides a low-impedance multilayer circuit board and its manufacturing process, including a circuit board body 1 for providing mechanical support and electrical insulation. The circuit board body 1 includes a substrate 100, and both ends of the substrate 100 have protruding connecting tenons 1002 for snap-fitting. The substrate 100 uses an insulating substrate commonly used in multilayer circuit boards (such as FR-4 epoxy glass cloth copper-clad laminate). Its two ends are processed by mechanical milling or laser cutting to form symmetrical protruding connecting tenons 1002. The connecting tenons 1002 and the substrate 100 body are integrally formed, which has high mechanical strength. The front and back sides of the substrate 100 are shown. A first solder resist layer 101 and a second solder resist layer 102 are symmetrically arranged. Both ends of the first solder resist layer 101 and the second solder resist layer 102 are provided with tenons 1011, and the tenons 1002 and the tenons 1011 are interlocked. The two ends of the tenons 1011 are alternately provided with high thermal conductivity insulating resin 104 for interlocking the interlocking action between the first solder resist layer 101, the second solder resist layer 102 and the substrate 100. The high thermal conductivity insulating resin 104 is not only used for bonding, but also forms a transverse thermal conductive structure at the interlayer joint, which helps to quickly conduct the heat generated by local hot spots to the entire surface or edge of the substrate 100.

[0021] Thermally conductive vias 1020 are uniformly formed on the surfaces of the first solder resist layer 101 and the second solder resist layer 102. Limiting grooves 1010 for positioning are formed on both the front and back sides of the first solder resist layer 101. The limiting grooves 1010 can be simultaneously etched during the fabrication of the solder resist layer to precisely secure the thermally conductive material 103. Thermally conductive material 103 for heat dissipation is embedded inside the limiting grooves 1010. Multiple copper pillars 1030 for heat conduction are raised on the surface of the thermally conductive material 103. The copper pillars 1030 directly contact the external heat sink. The copper pillars 1030 are arranged in an array to enhance heat dissipation. The effective heat dissipation area greatly enhances convective heat transfer. The copper pillars 1030 serve multiple purposes: First, the copper pillars 1030 are directly exposed to the circuit board surface or in contact with external heat sinks or air, significantly increasing the heat exchange area between the thermally conductive material 103 and the external environment, thus strengthening the convective heat transfer effect. Second, the gaps between the copper pillars 1030 can accommodate air or additional thermally conductive media, forming a microscale heat dissipation structure. Third, the copper pillars 1030 can also play a certain capillary role, assisting in the spreading of the thermally conductive media in subsequent dispensing or potting processes. After the thermally conductive material 103 is embedded in the limiting groove 1010, its bottom surface is in close contact with the thermally conductive path in the substrate 100 or solder mask layer, forming a low thermal resistance channel from the heat source to the outside. First filling grooves 1003 are staggered on both sides of the connecting tenon 1002, and second filling grooves 1013 are correspondingly formed on both sides of the inner wall of the tenon 1011. High thermal conductivity insulating resin 104 fills the connection between the substrate 100 and the first solder resist layer 101 and the second solder resist layer 102 through the second filling grooves 1013 and the first filling grooves 1003. The staggered first filling grooves 1003 and second filling grooves 1013 form a three-dimensional, non-planar cavity network. After the high thermal conductivity insulating resin 104 is injected and cured, the resin forms a series of "I" or "T" shaped structures in these grooves. The anchor bolts firmly lock the substrate 100 to the first solder mask layer 101 and the second solder mask layer 102 together like "bolts" or "pins", mechanically locking the substrate 100 and the solder mask layer together, significantly enhancing the bonding strength and resisting shear stress caused by the difference in thermal expansion coefficients. One end of the tenon 1002 is provided with a slot 1001, and one end of the slot 1001 is provided with a limiting protrusion 1012. The limiting protrusion 1012 is engaged inside the slot 1001. After the limiting protrusion 1012 is engaged in the slot 1001, it can effectively resist the shear stress in the plane of the board and prevent interlayer misalignment.

[0022] During assembly, the first solder resist layer 101 and the second solder resist layer 102 are aligned and pressed together from both sides of the substrate 100, so that the connecting tenon 1002 is fully embedded in the mortise 1011. At the same time, the limiting protrusion 1012 is engaged with the slot 1001. This structure achieves two-layer positioning: first, the engagement of the connecting tenon 1002 with the mortise 1011 restricts the translation of the solder resist layer relative to the substrate 100 in all directions in the plane; second, the engagement of the limiting protrusion 1012 with the slot 1001 further restricts the solder resist layer along the connecting tenon. The sliding along the length of 1002, the above-mentioned dual positioning mechanism can effectively prevent the solder mask layer and the embedded thermal conductive material 103 from shifting position under the high temperature and high pressure environment applied in the subsequent lamination process, and ensure the high-precision alignment of the thermal conductive material 103 with the designed heat source position. The surfaces of the first solder mask layer 101 and the second solder mask layer 102 are also uniformly provided with thermal conductive vias 1020, the inner walls of the vias are plated with copper, and the thermal conductive vias 1020 further guide the heat of the thermal conductive material 103 to the copper layer or heat dissipation path on the surface of the circuit board.

[0023] The inner wall of the thermal vias 1020 is plated with a copper layer. These thermal vias 1020 penetrate the solder mask layer. Their lower ends are in contact with the thermal conductive path in the thermal conductive material 103 or the substrate 100, and their upper ends are connected to the copper layer or component pads on the surface of the circuit board. The function of the thermal vias 1020 is to further guide the heat absorbed by the thermal conductive material 103 to a wider area on the surface of the circuit board, avoiding heat accumulation in local areas. At the same time, the thermal vias 1020 and the high thermal conductivity insulating resin 104 together form a three-dimensional and continuous heat dissipation network. Heat can start from the heat-generating element, enter the thermal conductive material 103 through the copper pillar 1030, and then diffuse to the entire circuit board plane through the thermal vias 1020 and the high thermal conductivity insulating resin 104, and finally dissipate through natural convection or contact heat sink.

[0024] A fabrication process for a low-impedance multilayer circuit board includes the following steps: S1. Prepare a substrate 100, process connecting tenons 1002 at both ends of the substrate, and open first filling grooves 1003 on both sides of the tenons; S2. First solder resist layer 101 and second solder resist layer 102 are made respectively. Tenon grooves 1011 are opened at both ends of the cured first solder resist layer 101 and second solder resist layer 102 by screen printing. Second filling grooves 1013 are opened on both sides of the inner wall of the tenon groove 1011 by laser engraving. S3. The first solder resist layer 101 and the second solder resist layer 102 are symmetrically attached to both sides of the substrate 100, so that the connecting tenon 1002 is embedded in the tenon groove 1011. At this time, the first filling groove 1003 and the second filling groove 1013 form a connected cavity channel. S4. Embed thermally conductive material 103 in the limiting groove 1010, so that the copper pillars 1030 on its surface face outwards and the copper pillars 1030 on the surface of the copper block face outwards. The copper block and the limiting groove 1010 adopt a transition fit and are pre-fixed by applying a small amount of thermally conductive adhesive. S5. Through the corresponding positions of the first filling groove 1003 and the second filling groove 1013, inject high thermal conductivity insulating resin 104 into the connecting channel of the first filling groove 1003 and the second filling groove 1013 from the injection port, maintain the injection time for 30 seconds, and stop after all overflow ports show uniform resin. Then cure in an oven at 120°C for 90 minutes, and cool naturally. After curing, an interlocking structure is formed. S6. Perform lamination, drilling, electroplating, and pattern transfer to complete the fabrication of the multilayer circuit board.

[0025] One end of the connecting tenon 1002 is also provided with a slot 1001, and one end of the slot 1011 is provided with a matching limiting protrusion 1012. During assembly, the limiting protrusion 1012 is inserted into the slot 1001.

[0026] The heat-conducting material 103 is a copper or aluminum block, and its surface is formed with multiple copper pillars 1030 by stamping or etching to increase the heat dissipation area.

[0027] The high thermal conductivity insulating resin 104 is an epoxy resin filled with aluminum nitride or aluminum oxide particles, which forms a mechanical interlock and thermal conduction path after curing.

[0028] In step S5, after injecting the high thermal conductivity insulating resin 104, a vacuum-assisted process is used to remove air bubbles. The assembled plate is placed in a vacuum chamber, and the pressure difference is used to make the high thermal conductivity insulating resin 104 completely penetrate into the first filling groove 1003 and the second filling groove 1013, ensuring that there are no air bubbles after filling.

[0029] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A low-impedance multilayer circuit board, comprising a circuit board body (1) for providing mechanical support and electrical insulation, characterized in that, The circuit board body (1) includes a substrate (100). The substrate (100) has protruding connecting tenons (1002) for snap-fitting at both ends. The substrate (100) has a first solder resist layer (101) and a second solder resist layer (102) symmetrically arranged on its front and back sides. The first solder resist layer (101) and the second solder resist layer (102) are provided with tenons (1011) at both ends. The connecting tenons (1002) and the tenons (1011) are interlocked. The two ends of the tenons (1011) are provided with high thermal conductivity insulating resin (104) for interlocking the interlocking action between the first solder resist layer (101), the second solder resist layer (102) and the substrate (100).

2. The low-impedance multilayer circuit board as described in claim 1, characterized in that, The surfaces of the first solder resist layer (101) and the second solder resist layer (102) are uniformly provided with heat-conducting vias (1020), and the front and back surfaces of the first solder resist layer (101) are provided with limiting grooves (1010) for limiting.

3. A low-impedance multilayer circuit board as described in claim 2, characterized in that, The limiting groove (1010) is embedded with a heat-conducting material (103) for heat dissipation, and the surface of the heat-conducting material (103) has a plurality of copper pillars (1030) for conducting heat.

4. A low-impedance multilayer circuit board as described in claim 3, characterized in that, The connecting tenon (1002) has a first filling groove (1003) staggered on both sides, and the inner wall of the tenon (1011) has a second filling groove (1013) corresponding to both sides. The high thermal conductivity insulating resin (104) is filled in the connection between the substrate (100) and the first solder resist layer (101) and the second solder resist layer (102) through the second filling groove (1013) and the first filling groove (1003).

5. A low-impedance multilayer circuit board as described in claim 4, characterized in that, One end of the connecting tenon (1002) is provided with a slot (1001), and one end of the slot (1011) is provided with a limiting protrusion (1012), which is engaged inside the slot (1001).

6. The manufacturing process of a low-impedance multilayer circuit board as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Prepare a substrate (100), process connecting tenons (1002) at both ends of the substrate, and open first filling grooves (1003) on both sides of the tenons. S2. First solder resist layer (101) and second solder resist layer (102) are made respectively, and mortises (1011) are opened at both ends of the first solder resist layer (101) and the second solder resist layer (102). Second filling grooves (1013) are opened on both sides of the inner wall of the mortises (1011). S3. The first solder resist layer (101) and the second solder resist layer (102) are symmetrically attached to both sides of the substrate (100) so that the connecting tenon (1002) is embedded in the tenon (1011); S4. Embed thermally conductive material (103) in the limiting groove (1010) so that the copper pillars (1030) on its surface face outward; S5. High thermal conductivity insulating resin (104) is injected through the corresponding positions of the first filling groove (1003) and the second filling groove (1013), and an interlocking structure is formed after curing. S6. Perform lamination, drilling, electroplating, and pattern transfer to complete the fabrication of the multilayer circuit board.

7. The fabrication process of a low-impedance multilayer circuit board as described in claim 6, characterized in that, One end of the connecting tenon (1002) is also provided with a slot (1001), and one end of the slot (1011) is provided with a matching limiting protrusion (1012). During assembly, the limiting protrusion (1012) is inserted into the slot (1001).

8. The fabrication process of a low-impedance multilayer circuit board as described in claim 6, characterized in that, The thermally conductive material (103) is a copper or aluminum block, and its surface is formed with multiple copper pillars (1030) by stamping or etching to increase the heat dissipation area.

9. The fabrication process of a low-impedance multilayer circuit board as described in claim 6, characterized in that, The high thermal conductivity insulating resin (104) is an epoxy resin filled with aluminum nitride or aluminum oxide particles, which forms a mechanical interlock and thermal conduction path after curing.

10. The fabrication process of a low-impedance multilayer circuit board as described in claim 9, characterized in that, In step S5, after injecting the high thermal conductivity insulating resin (104), a vacuum-assisted process is used to remove air bubbles.

Images