Copper block embedded printed circuit board and processing technology

Abstract

The invention relates to the field of printed circuit boards, in particular to a copper block embedded printed circuit board and a processing technology, the copper block embedded printed circuit board comprises a substrate and a copper block embedded in the substrate, the embedding edge of the copper block and the substrate is provided with an embedding locking part, and the substrate is provided with a substrate embedding groove; the interlocking part comprises a clamping groove formed in the outer edge of the copper block and a containing groove formed in the inner wall of the embedding groove of the base plate; the containing groove and the clamping groove are jointly filled with a filling material which is heated, melted and expanded and solidified after being cooled, and three-dimensional mechanical interlocking is formed. An interlocking part comprising a clamping groove and a containing groove is arranged on the embedding edge of a copper block and a substrate, and a modified epoxy hot melting material which is heated to melt and expand and is solidified after being cooled is filled to form a three-dimensional mechanical interlocking structure; the problems that in a traditional copper block embedding technology, the attaching degree is insufficient due to the fact that the slotting machining precision of the base plate is deviated, thermal cycle stress accumulation is caused by the difference between the thermal expansion coefficients of the copper block and the base plate, and the binding force is insufficient due to the fact that pressing technology parameters are not accurate are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of printed circuit boards, and in particular to a copper-embedded printed circuit board and its processing technology. Background Technology

[0002] In computer hardware connectivity, data transmission and power distribution between the hard drive and motherboard are typically achieved via an adapter circuit board. This type of adapter circuit board must simultaneously ensure stable data signal transmission, power supply during hard drive operation, heat dissipation during hard drive operation, and current carrying capacity during startup and operation. During hard drive operation, the interface area is a critical area with concentrated heat and high current density. Currently, to address heat dissipation and high current transmission in this area, some adapter circuit boards incorporate a copper-embedded structure in the area corresponding to the hard drive interface. Utilizing copper's high thermal conductivity and low resistance, this structure dissipates heat from the vicinity of the hard drive interface and ensures stable high current transmission during startup and operation, thus preventing hard drive malfunctions due to localized overheating or current fluctuations. Currently, in the processing of the copper-embedded block and the substrate, the copper block is cut, polished, and tin / gold plated before being embedded into the corresponding slot on the substrate and then solidified using a high-temperature, high-pressure process. However, certain structural stability issues still exist. On the one hand, if there are slight deviations in the processing precision of the substrate mating groove, even if the copper block is polished, its fit with the inner wall of the groove cannot be fully guaranteed, which may lead to stress concentration at the joint later. On the other hand, there is a significant difference in the coefficient of thermal expansion between the copper block and the substrate. In the actual use of the adapter circuit board, the heat generated by the hard drive and the fluctuation of the ambient temperature will cause the two to expand and contract to different degrees. Repeated thermal cycles will continuously aggravate the stress accumulation at the joint interface. At the same time, if the parameter control of the high temperature and high pressure bonding process is not precise, it may lead to insufficient bonding force between the copper block and the substrate. Combined with the adhesion decay caused by uneven tin / gold plating, the copper block and the substrate are very likely to detach. Once detachment occurs, it will not only directly interrupt the high current transmission path and block the heat dissipation channel, but may also cause circuit short circuits and other faults, seriously threatening the stable operation of the computer hard drive. Summary of the Invention

[0003] In view of the problem of insufficient bonding force between the copper block and the substrate in the above or existing technologies, the present invention is proposed.

[0004] Therefore, the purpose of this invention is to provide a copper-embedded printed circuit board and its processing technology.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A copper-embedded printed circuit board includes a substrate and a copper block embedded in the substrate. The copper block has a locking part at the edge where it is fitted with the substrate, and a substrate fitting groove is formed on the substrate. The locking part includes a slot formed on the outer edge of the copper block and a receiving slot formed on the inner wall of the substrate fitting groove. The receiving groove and the card slot are both filled with a filling material that melts and expands when heated and solidifies after cooling, forming a three-dimensional mechanical interlock.

[0006] In a preferred embodiment of the copper-embedded printed circuit board of the present invention, the cross-sectional shape of the receiving groove and the card slot are both trapezoidal.

[0007] In a preferred embodiment of the copper-embedded printed circuit board of the present invention, the filling material is a modified epoxy hot-melt filler material.

[0008] In a preferred embodiment of the copper-embedded printed circuit board of the present invention, the single-sided gap between the copper block and the substrate fitting groove is 10-100 micrometers.

[0009] As a preferred embodiment of the copper-embedded printed circuit board of the present invention, wherein: the surface of the copper block is provided with a nickel plating layer, and the inner wall of the substrate fitting groove is provided with a roughening treatment layer.

[0010] The present invention also provides a processing technology for a copper-embedded printed circuit board, used to process the above-mentioned copper-embedded printed circuit board, specifically including the following steps: S1: Substrate mating groove processing: A substrate mating groove for accommodating copper blocks is processed on the substrate, and a receiving groove structure is processed on the inner wall of the substrate mating groove. S2: Copper block pretreatment: Cut and grind the copper block, and process a groove on its outer edge; S3: Surface treatment: The surface of the copper block is plated, and the inner wall of the substrate fitting groove is cleaned. S4: Pre-filling material: Pre-filling material in the receiving groove; S5: Fitting Assembly: Embed the copper block into the substrate receiving groove and perform alignment correction; S6: Hot pressing curing: The hot pressing process melts, expands and fills the space of the receiving groove and slot, and the cooling rate is controlled to cure the filling material to form a mechanically interlocked structure.

[0011] As a preferred embodiment of the processing technology for the copper-embedded printed circuit board of the present invention, the substrate mating groove is processed by a high-precision CNC milling machine, and the dimensional tolerance is controlled within ±0.05mm.

[0012] As a preferred embodiment of the processing technology for the copper-embedded printed circuit board of the present invention, the hot pressing curing is carried out in a vacuum environment, and the hot pressing temperature is set according to the melting point of the filler material.

[0013] As a preferred embodiment of the processing technology of the copper-embedded printed circuit board of the present invention, the pressure applied during the hot pressing curing process is 0.5-5MPa, the holding time is 30-180 seconds, and the cooling rate is 1-5℃ / minute until the temperature drops below 50℃.

[0014] As a preferred embodiment of the processing technology of the copper-embedded printed circuit board of the present invention, it further includes the following follow-up processing steps: cleaning the completed circuit board and performing interface quality inspection by ultrasonic scanning microscope.

[0015] The beneficial effects of the copper-embedded printed circuit board and its processing technology of the present invention are as follows: In this application, by setting an interlocking part including a slot and a receiving groove at the interlocking edge of the copper block and the substrate, and filling it with a modified epoxy hot melt material that expands upon heating and solidifies upon cooling to form a three-dimensional mechanical interlocking structure, the technical problems in the traditional copper block interlocking process, such as insufficient adhesion caused by deviations in the substrate slotting processing accuracy, accumulation of thermal cycle stress caused by the difference in thermal expansion coefficients between the copper block and the substrate, and insufficient bonding force caused by inaccurate pressing process parameters, are effectively solved. The hot melt expansion characteristics of the filling material compensate for the processing gap, and the multi-directional interlocking effect of the trapezoidal groove is used to evenly disperse the interface stress. Combined with the nickel plating layer and the roughening treatment layer, the interface adhesion is enhanced, thereby significantly improving the mechanical bonding strength and long-term working reliability of the copper block structure, ensuring the continuity of the high current transmission path and the stability of the heat dissipation channel. It is particularly suitable for printed circuit board applications in high power density and high current operating environments. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a process flow diagram of the present invention.

[0018] Figure 2 This is a three-dimensional structural diagram of the present invention.

[0019] Figure 3 This is an exploded view of the three-dimensional structure of the present invention.

[0020] In the figure: 11, substrate; 12, copper block; 2, locking part; 21, substrate fitting groove; 22, slot; 23, receiving groove. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] Reference Figures 1-3 This embodiment provides a copper-embedded printed circuit board and its processing technology, which can achieve the effect of filling the space between the substrate 11 and the copper block 12 with a modified epoxy hot melt material that expands when heated and solidifies after cooling to form a three-dimensional mechanical interlocking structure. It includes a substrate 11 and a copper block 12 embedded in the substrate 11. The copper block 12 and the substrate 11 are provided with an interlocking part 2 at their interlocking edge. The interlocking part 2 includes a slot 22 formed on the outer edge of the copper block 12 and a receiving groove 23 formed on the inner wall of the substrate interlocking groove 21. The receiving groove 23 and the slot 22 are filled with a filling material that expands when heated and solidifies after cooling to form a three-dimensional mechanical interlock.

[0023] In this embodiment, the locking part 2 refers to the interlocking structure provided at the edge where the copper block 12 and the substrate 11 fit together, which can realize the mechanical engagement between the copper block 12 and the substrate 11 to enhance the stability of the fitting interface. The slot 22 refers to the groove-shaped structure formed on the outer edge of the copper block 12, which is formed by mechanical processing technology such as milling, laser cutting or stamping.

[0024] Furthermore, the receiving groove 23 refers to a groove-shaped structure formed on the inner wall of the substrate fitting groove 21, which is formed by etching, drilling or molding processes. The shape of the groove is complementary to the slot 22 to form an interlocking fit. The filling material is a material that melts and expands when heated and solidifies after cooling. Its main purpose is to fill the gap between the slot 22 and the receiving groove 23 after melting, and to form a continuous three-dimensional mechanical interlocking body after cooling. Thus, this application constructs a three-dimensional mechanical interlocking mechanism between the copper block 12 and the substrate 11 through the collaborative design of the interlocking part 2 and the filling material. This can compensate for the small gaps caused by the deviation of processing accuracy and evenly distribute the stress to the entire interface during thermal cycling, thereby avoiding the risk of separation caused by the difference in thermal expansion coefficient and temperature fluctuation, and ensuring the reliability of the high current transmission path and heat dissipation channel. Specifically, the filling material fully fills the gap after melting and expanding when heated, and forms a multi-directional interlocking effect according to the groove structure when cooled and solidified, thereby effectively addressing the structural stability hazards mentioned in the background art.

[0025] In one embodiment, the copper-embedded printed circuit board comprises a substrate 11 and copper blocks 12 embedded in the substrate 11, wherein the interlocking edge of the copper block 12 and the substrate 11 is provided with an interlocking portion 2. The interlocking portion 2 includes a slot 22 formed on the outer edge of the copper block 12 and a receiving groove 23 formed on the inner wall of the substrate interlocking groove 21. The receiving groove 23 and the slot 22 are both filled with a filler material, which has the characteristics of melting and expanding when heated and solidifying after cooling. When heated, the filler material melts and expands, fully filling the gap space between the slot 22 and the receiving groove 23, compensating for the small gaps caused by the machining accuracy deviation of the substrate interlocking groove 21; after cooling and solidification, the filler material forms a continuous three-dimensional mechanical interlocking body in the groove. Due to the constraint of the groove shape, the solidified material produces a multi-directional interlocking effect, which evenly disperses the stress caused by the difference in thermal expansion coefficient and temperature fluctuation during hard disk operation to the entire bonding interface, avoiding separation caused by local stress concentration, thereby ensuring that the copper block 12 and the substrate 11 maintain a stable connection under current load and thermal cycling conditions.

[0026] Furthermore, as a specific embodiment, the slot 22 can be a dovetail-shaped slot opened on the outer edge of the copper block 12, and the receiving slot 23 is correspondingly designed with a complementary dovetail-shaped profile, so that the filling material can completely fill the slot space after melting and expanding in the hot pressing process, and form a strong mechanical interlocking structure during the cooling and solidification process; thus, this design not only adapts to the unilateral gap change between the copper block 12 and the substrate 11, but also strengthens the interface bonding strength through the three-dimensional interlocking mechanism.

[0027] Specifically, through the synergistic effect of the locking part 2 and the filling material, the bonding interface between the copper block 12 and the substrate 11 maintains a reliable connection under temperature fluctuations and current loads during hard disk operation, effectively preventing the risk of separation caused by accumulated stress from thermal cycling. This technical solution significantly improves the mechanical stability of the bonding interface, maintaining the continuity of the high current transmission path and ensuring the integrity of the heat dissipation channel, thereby solving the structural stability problem and ensuring the stability of data transmission and the reliability of heat dissipation function.

[0028] In the above scheme, the cross-sectional shape of the locking part 22 and the receiving groove 23 is not limited. However, if a straight edge shape is adopted in this process, the thermal cycle stress caused by the difference in thermal expansion coefficient is easily concentrated at the right-angle edge, causing the filling material to separate from the groove wall, which ultimately increases the risk of the copper block 12 detaching from the substrate 11.

[0029] Reference Figures 1-3 This application further proposes that the cross-sectional shape of the receiving groove 23 and the card slot 22 are both trapezoidal.

[0030] Specifically, a trapezoidal profile refers to a geometric shape with a parallel upper and lower base and inclined sides. It is achieved by using variations such as isosceles trapezoids or right trapezoids. Its purpose is to use the geometric properties of the inclined plane to disperse stress during thermal cycling and avoid stress concentration at the right-angled edges, thereby providing basic stability for mechanical interlocking structures.

[0031] Specifically, the solution of this application designs the cross-sections of the receiving groove 23 and the slot 22 as trapezoids, forming a wedge-shaped locking structure after the filling material melts, expands, cools, and solidifies. When the copper block 12 and the substrate 11 undergo relative displacement due to the difference in their coefficients of thermal expansion, the trapezoidal slope converts the tensile stress into normal pressure, thereby effectively dispersing the thermal cycle stress, avoiding stress concentration at the right-angle edge, preventing the filling material from separating from the groove wall, and ensuring that the three-dimensional mechanical interlocking function of the locking part 2 remains reliable during long-term use.

[0032] As a specific implementation method, the solution of this application is implemented as follows: the cross-section of the receiving groove 23 and the card slot 22 is designed as an isosceles trapezoid, and its two sides are inclined at a gradually changing angle, so that the locking structure formed after the filling material is cured can evenly distribute the stress generated during the thermal cycle, effectively coping with the thermal expansion difference between the copper block 12 and the substrate 11.

[0033] Through the above solution, this application effectively avoids the concentration of thermal cycling stress at the right-angle edge, prevents the filling material from separating from the groove wall, thereby reducing the risk of the copper block 12 detaching from the substrate 11, and ensuring the long-term stability of the heat dissipation and high current transmission function of the copper block printed circuit board in the hard disk interface area.

[0034] In some of the embodiments described above in this application, a filling material is proposed to form a three-dimensional mechanical interlock. However, in the process of its implementation, the general filling material may fail in the interlock structure due to the mismatch between the coefficient of thermal expansion of the copper block 12 and the substrate 11 or insufficient mechanical strength after curing. This can exacerbate the accumulation of interface stress, cause the copper block 12 to detach, and thus interrupt the high current transmission path and block the heat dissipation channel.

[0035] Reference Figures 1-3 Furthermore, this application proposes that the filler material is a modified epoxy hot melt filler material.

[0036] Among them, the modified epoxy hot melt filler material refers to a hot melt material based on epoxy resin matrix that has undergone chemical modification. It achieves optimized control of the coefficient of thermal expansion by adding silane coupling agents or inorganic oxide fillers. Its purpose is to make the material properties closer to the physical parameter range of copper block 12 and substrate 11, thereby effectively buffering thermal stress and improving the reliability of interface bonding in temperature fluctuation environment.

[0037] Specifically, the modified epoxy hot-melt filler material is heated and melted during the hot-pressing process, resulting in controlled expansion. It fully fills the tiny gap between the slot 22 and the receiving slot 23, and forms a dense three-dimensional interlocking structure after cooling and solidification. Since the thermal expansion coefficient of the material is adjusted to match the range of the copper block 12 and the substrate 11, it can absorb the stress caused by the difference in thermal expansion and contraction during repeated thermal cycles, avoiding interface peeling. At the same time, the high cohesive strength and interface adhesion of the material ensure that the interlocking structure remains intact during long-term use, thereby working together with the trapezoidal cross-sectional structure of the locking part 2 to maintain the overall bonding stability.

[0038] As a preferred embodiment, the solution of this application is specifically implemented as follows: the filling material can be a type of epoxy resin system containing an organosilicon modifier. After the material melts during the hot pressing process, it can completely fill the trapezoidal groove 22 and the receiving groove 23. After cooling, it forms a strong mechanical interlocking structure. The epoxy resin matrix achieves precise control of thermal expansion characteristics through the introduction of organosilicon components.

[0039] Through the above solution, this application effectively prevents the failure of the interlocking structure due to mismatch in thermal expansion coefficients or insufficient mechanical strength, significantly reduces the risk of interface stress accumulation and copper block 12 detachment, and ensures the continuity of the high current transmission path and the long-term reliability of the heat dissipation channel.

[0040] In some of the embodiments described above in this application, a single-sided gap control between the copper block 12 and the substrate fitting groove 21 is proposed to optimize the filling effect of the filling material and alleviate the accumulation of thermal stress. However, in the process of its implementation, if the gap size is too small, the flow of the filling material will be obstructed when it expands due to heat and it will not be able to fully fill the fitting edge. If the gap size is too large, it will cause uneven distribution of the filling material or insufficient bonding force. Combined with the difference in thermal expansion coefficient between the copper block 12 and the substrate 11, the interface stress concentration will be aggravated during temperature cycling, which will eventually lead to the risk of the copper block 12 detaching.

[0041] Reference Figures 1-3 This application further proposes that the single-sided gap between the copper block 12 and the substrate fitting groove 21 is 10-100 micrometers.

[0042] In practical applications, the single-sided gap refers to the reserved gap size on one side between the copper block 12 and the substrate fitting groove 21. It is achieved by using a micron-level gap controlled by precision machining technology. The purpose is to ensure that the filling material can flow fully and fill the space of the locking part 2 evenly during the hot pressing process, while providing a buffer space for the deformation caused by the difference in thermal expansion coefficients between the copper block 12 and the substrate 11.

[0043] Specifically, the solution of this application precisely limits the single-sided gap to the range of 10 to 100 micrometers, so that the filling material can expand uniformly and completely fill the space of the receiving groove 23 and the slot 22 when it is heated and melted during the hot pressing process. This avoids the material flow restriction caused by the gap being too small or the filling voids caused by the gap being too large. At the same time, this gap range fully considers the difference in thermal expansion coefficients between the copper block 12 and the substrate 11, which promotes a more uniform stress distribution during the cooling and solidification process and reduces the tendency of interface peeling caused by temperature fluctuations, thereby significantly improving the stability of the interlocking structure under long-term thermal cycling environment.

[0044] As a specific embodiment, the solution of this application is implemented as follows: the single-sided gap between the copper block 12 and the substrate fitting groove 21 can be controlled at about 50 micrometers. This gap can be precisely set when the substrate fitting groove 21 is processed by a high-precision CNC milling machine, and the size can be adjusted by precision grinding during the pre-processing stage of the copper block 12 to ensure that the gap is within the optimized range, so that the filling material can fully fill the trapezoidal cross-sectional structure of the locking part 2 during the hot pressing process.

[0045] Through the above solution, this application effectively ensures the ability of the filling material to form a complete three-dimensional mechanical interlocking structure, significantly reduces the risk of interface stress concentration caused by thermal cycling, improves the long-term reliability of the interface between the copper block 12 and the substrate 11, and avoids circuit interruption or short circuit failure caused by the detachment of the copper block 12.

[0046] In practical applications, gap control is proposed in some embodiments of this application to optimize the distribution space of the filling material. However, in this process, the interface adhesion between the surface of the copper block 12 and the inner wall of the substrate fitting groove 21 is insufficient, which leads to the weakening of the bond between the filling material and the substrate. Under the difference in thermal expansion coefficient and temperature fluctuation, the interface stress is easily accumulated, which in turn causes the copper block 12 to detach.

[0047] Reference Figures 1-3 This application further proposes that the surface of the copper block 12 is provided with a nickel plating layer and the inner wall of the substrate fitting groove 21 is provided with a roughening treatment layer.

[0048] Among them, the nickel plating layer refers to the nickel metal layer formed on the surface of the copper block 12, which is achieved by electroplating or chemical plating. The purpose is to provide a uniform and stable metal interface and avoid the adhesion decay caused by uneven traditional plating treatment. The roughening treatment layer can be understood as the micro-roughening structure of the inner wall of the substrate fitting groove 21, which is achieved by sandblasting or chemical etching. The purpose is to increase the contact area with the filling material and promote the anchoring effect.

[0049] Specifically, the solution of this application, through the cooperation of the nickel plating layer on the surface of the copper block 12 and the roughening treatment layer on the inner wall of the substrate interlocking groove 21, allows the filling material to adhere more reliably to the surface of the nickel plating layer during the hot pressing and curing process, while anchoring in the microstructure of the roughening treatment layer, thereby enhancing the stability of the three-dimensional mechanical interlocking structure and effectively resisting the accumulation of interface stress caused by thermal cycling.

[0050] As a specific implementation, the surface of the copper block 12 can be plated with a nickel layer by electroplating, and the inner wall of the substrate fitting groove 21 can be roughened by sandblasting.

[0051] Through the above solution, this application effectively strengthens the interface adhesion, solves the problem of weakened bonding of the filler material, reduces the accumulation of interface stress under the difference of thermal expansion coefficient and temperature fluctuation, and prevents the risk of copper block 12 detaching.

[0052] In another embodiment, this application also discloses a processing technology for a copper-embedded printed circuit board, including the following steps: Substrate fitting groove 21 processing: A substrate fitting groove 21 for accommodating copper block 12 is processed on substrate 11, and a receiving groove 23 structure is processed on the inner wall of substrate fitting groove 21. Pre-treatment of copper block 12: Cut and grind the copper block 12, and process the groove 22 on its outer edge; Surface treatment: The surface of the copper block 12 is plated, and the inner wall of the substrate fitting groove 21 is cleaned. Pre-filling material: Pre-filling material is placed in the receiving groove 23; Fitting assembly: The copper block 12 is embedded into the receiving groove 23 of the substrate 11 and alignment is performed; Hot pressing curing: The hot pressing process melts, expands and fills the space of the receiving groove 23 and the slot 22, and the cooling rate is controlled to cure the filling material to form a mechanical interlocking structure. The core innovation of this embodiment lies in the complementary geometry design of the slot 22 on the outer edge of the copper block 12 and the receiving groove 23 on the inner wall of the substrate fitting groove 21. By utilizing the thermal expansion characteristics of the filling material, a three-dimensional mechanical interlocking structure is formed during the hot pressing and curing process. This effectively compensates for the small gaps caused by the deviation in processing accuracy, evenly disperses the stress accumulation caused by the difference in thermal expansion coefficient, and enhances the interface bonding strength. This achieves the effect of maintaining a stable connection between the copper block 12 and the substrate 11 under the working thermal cycle and current load conditions of the hard disk.

[0053] Specifically, in some embodiments of this application, a substrate fitting groove 21 is processed to form an embedding space for the copper block 12. However, insufficient control of processing precision during this process can lead to dimensional deviations in the substrate fitting groove 21, resulting in incomplete contact between the copper block 12 and the inner wall of the groove. This can create a stress concentration risk at the subsequent bonding interface, thereby increasing the risk of the copper block 12 detaching and affecting the structural stability and heat dissipation and conductivity of the circuit board.

[0054] Reference Figures 1-3 This application further proposes that the substrate fitting groove 21 is processed by a high-precision CNC milling machine, and the dimensional tolerance is controlled within ±0.05mm.

[0055] Among them, the high-precision CNC milling machine adopts a five-axis linkage CNC milling machine or a CNC milling machine with thermal deformation compensation function. Its purpose is to accurately control the machining path through digital program, eliminate human operation error and mechanical vibration interference, and ensure the high consistency of the geometric contour of the fitting groove. The purpose of the dimensional tolerance within ±0.05mm is to match the single-sided gap requirement between the copper block 12 and the substrate fitting groove 21, so that the two form a tight fit and reduce the uneven gap phenomenon during assembly.

[0056] Specifically, the solution of this application uses a high-precision CNC milling machine to precisely generate the geometric contour of the substrate fitting groove 21. Combined with strict dimensional tolerance control, it ensures that the size of the fitting groove is highly matched with the size of the copper block 12, reducing the uneven gap between the copper block 12 and the substrate fitting groove 21. This allows the filling material to uniformly fill the space of the slot 22 and the receiving slot 23 during subsequent assembly, thereby forming a reliable three-dimensional mechanical interlocking structure and effectively preventing interface failure caused by stress accumulation during thermal cycling.

[0057] As a specific implementation method, the solution of this application is implemented as follows: the substrate mating groove 21 can be processed by a CNC milling machine equipped with a high-precision spindle, and the milling operation is performed through a preset processing program. The dimensional tolerance is controlled within ±0.05mm to ensure that the dimensional accuracy of the mating groove meets the requirements.

[0058] Through the above solution, this application effectively solves the problem of insufficient processing precision of substrate fitting groove 21, ensures tight bonding between copper block 12 and substrate 11, reduces the risk of stress concentration at the bonding interface, and thus improves the structural stability and reliability of heat dissipation and conductivity of copper-embedded printed circuit board.

[0059] In some embodiments of this application, a hot-press curing step is proposed to melt and expand the filler material and form a mechanically interlocked structure. However, if hot-press curing is carried out in an atmospheric environment, air, moisture or impurities are easily introduced, causing the filler material to oxidize or generate bubbles, which weakens the interfacial bonding strength. At the same time, if the hot-pressing temperature is not precisely controlled according to the melting point of the filler material, it may cause insufficient melting or excessive pyrolysis, resulting in the filler material failing to fill the gaps evenly or the structure becoming sparse after curing, which ultimately exacerbates the stress concentration and separation risk between the copper block 12 and the substrate 11.

[0060] Reference Figures 1-3 This application further proposes a hot-press curing step including: Hot pressing curing is carried out in a vacuum environment, and the hot pressing temperature is set according to the melting point of the filler material.

[0061] In practical applications, a vacuum environment means placing the hot pressing process in a sealed space at a pressure lower than atmospheric pressure. This is achieved using a vacuum chamber in conjunction with a mechanical pump system to eliminate interference from oxygen, water vapor, and particulate matter, and to prevent oxidation of the filler material or the retention of internal air bubbles during the high-temperature melting stage. The hot pressing temperature is set according to the melting point of the filler material, meaning that the hot pressing temperature threshold is strictly matched with the material properties. This is achieved by using an infrared temperature sensor to monitor the melting state in real time and combining it with a closed-loop control system to dynamically adjust the heat source output. The purpose is to ensure that the filler material is fully melted near its melting point to exert its expansion and filling capacity, while preventing temperature deviations that could lead to insufficient fluidity or thermal degradation.

[0062] Specifically, the solution of this application eliminates atmospheric interference through a vacuum environment, allowing the molten filling material to penetrate unimpeded into the microscopic gap between the slot 22 on the outer edge of the copper block 12 and the receiving groove 23 on the inner wall of the substrate fitting groove 21. At the same time, the hot pressing temperature is set according to the melting point of the filling material, which causes the material to fully expand during the melting stage to fill the single-sided gap, and achieves uniform shrinkage and high-strength solidification during the cooling stage, thereby synergistically ensuring the continuous density of the mechanical interlocking structure and the integrity of the interface bonding.

[0063] As a specific implementation method, the hot pressing curing process of this application is implemented as follows: The assembled circuit board is placed in a stainless steel vacuum chamber using a vacuum hot press, and a stable vacuum environment is established through the air extraction system; according to the material type of the filler material, a hot pressing temperature curve is preset. For example, when the filler material is a modified epoxy hot melt material, the hot pressing temperature is set in a range slightly higher than its melting point. Pressure is applied evenly using a heating plate so that the molten material fully fills the space between the slot 22 and the receiving groove 23.

[0064] Through the above solution, this application effectively avoids the oxidation and bubble retention problems of the filler material during the hot pressing process, ensures that the molten material penetrates uniformly into the micro gaps of the three-dimensional mechanical interlocking structure, thereby significantly improving the interface bonding strength between the copper block 12 and the substrate 11, reducing the risk of stress accumulation caused by thermal cycling, and ensuring the long-term structural stability and high current transmission reliability of the copper block printed circuit board in the hard disk interface area.

[0065] Specifically, in some of the embodiments described above in this application, hot pressing curing is carried out in a vacuum environment and the hot pressing temperature is set according to the melting point of the filler material. However, in the process of implementation, the control of pressure, holding time and cooling rate lacks precision, which can easily lead to the filler material not being able to fully melt and expand or to solidify unevenly, causing stress concentration at the interface between the copper block 12 and the substrate 11, and ultimately leading to the risk of detachment.

[0066] Reference Figures 1-3 This application further proposes that the pressure applied during the hot-press curing process is 0.5-5 MPa, the holding time is 30-180 seconds, and the cooling rate is 1-5℃ / minute until the temperature drops below 50℃.

[0067] Specifically, the pressure refers to the mechanical pressure applied between the copper block 12 and the substrate 11 during the hot-press curing process. It is achieved using a hydraulic system or a pneumatic pressure device. The purpose is to ensure that the molten filler material fully fills the tiny gaps between the locking groove 22 and the receiving groove 23 of the interlocking part 2 during the expansion stage, avoiding the material not being able to completely cover the interlocking area due to insufficient pressure or abnormal material extrusion due to excessive pressure. The heat preservation time refers to the duration for which the filler material is maintained at its melting point temperature. It is achieved using a temperature feedback control unit combined with a timing module. The purpose is to ensure that the filler material has sufficient melting and flow capacity to uniformly cover all interlocking interfaces, while preventing the material from thermally decomposing due to excessive time and affecting the curing quality. In practical applications, the cooling rate refers to the gradient control of temperature reduction after hot-press curing. It is achieved by adjusting the flow rate of the cooling medium using a programmable temperature control system. The purpose is to alleviate the accumulation of internal stress caused by the difference in thermal expansion coefficients between the copper block 12 and the substrate 11 through a controllable cooling process, avoiding microscopic cracking of the interface caused by rapid cooling.

[0068] Specifically, the solution of this application ensures that the molten filler material completely fills the three-dimensional space of the slot 22 and the receiving groove 23 during the expansion process through pressure parameters, avoiding the formation of unfilled areas; at the same time, the holding time parameter ensures that the filler material is maintained at the melting point temperature for a sufficient time to achieve full flow and interface wetting, satisfying the need for complete melting of the material while avoiding the risk of thermal degradation; on this basis, the cooling rate parameter precisely controls the cooling process, so that the filler material forms a uniform and dense structure during the solidification stage, effectively dispersing the thermal stress between the copper block 12 and the substrate 11. The synergistic effect of the above parameters enables the filler material to form a complete and continuous three-dimensional mechanical interlocking structure after cooling, significantly enhancing the interfacial bonding strength between the copper block 12 and the substrate 11.

[0069] As a specific implementation method, the solution of this application is implemented as follows: In the vacuum hot pressing equipment, a closed-loop pressure control system is used to apply stable pressure, and an infrared temperature sensor is used to monitor the state of the filling material in real time and automatically trigger the heat preservation timer. During the cooling stage, a multi-level temperature control strategy is adopted. First, the temperature is reduced to the glass transition temperature range of the material at a moderate rate, and then the cooling intensity is gradually adjusted until the safe temperature threshold is reached, so as to ensure that the filling material maintains a uniform physical state transformation during the curing process.

[0070] Through the above solution, this application effectively solves the stability problem of the filling material when forming a three-dimensional mechanical interlocking structure, significantly reduces the risk of stress concentration at the interface between the copper block 12 and the substrate 11, improves the structural reliability of the copper-embedded printed circuit board under the thermal cycling environment of hard disk operation, and avoids the interruption of high current transmission and failure of heat dissipation function caused by interface detachment.

[0071] In some of the embodiments described above in this application, subsequent processing steps are proposed for quality control of the mating interface. However, in the implementation process, failure to perform interface quality inspection may leave latent defects, thereby affecting the long-term reliability of the circuit board under thermal cycling environment.

[0072] In response, this application further proposes the following follow-up processing steps: cleaning the assembled circuit board and inspecting the interface quality using an ultrasonic scanning microscope.

[0073] Cleaning refers to removing residual impurities and debris from the surface of the circuit board. This is achieved through physical wiping, airflow purging, or solvent cleaning. The purpose is to avoid signal interference or misjudgment caused by residues in subsequent testing, ensuring a true reflection of the interface condition. Interface quality testing refers to using sound waves to detect internal defects in the mating interface. This is achieved using an ultrasonic scanning microscope. This device identifies abnormalities such as bubbles, cracks, or insufficient bonding by emitting and receiving ultrasonic signals. The purpose is to accurately capture early potential problems and intervene in time before the problem escalates.

[0074] Specifically, the solution of this application first performs a cleaning process to remove surface impurities, avoids residues from obscuring minor defects, and ensures the accuracy of subsequent testing. Then, the non-destructive detection capability of an ultrasonic scanning microscope is used to perform a deep scan of the interlocking interface. Based on the reflection or attenuation characteristics of sound waves in the defect area, internal anomalies are identified, thereby forming a complete quality control chain and effectively preventing functional interruption caused by interface detachment.

[0075] As a specific embodiment, the solution of this application is implemented as follows: the cleaning process can be specifically to use a lint-free cloth dipped in isopropyl alcohol to gently wipe the surface of the circuit board; the interface quality detection can be specifically to use an ultrasonic scanning microscope to scan, and adjust the sound wave frequency and gain parameters to adapt to the detection requirements inside the multi-layer structure.

[0076] Through the above solution, this application effectively identifies and eliminates the potential risks of the mating interface, improves the structural stability of the circuit board under thermal cycling conditions, and avoids the problem of heat dissipation channel interruption or current transmission path failure caused by latent defects.

[0077] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A copper-embedded printed circuit board, comprising a substrate (11) and copper blocks (12) embedded in the substrate (11), characterized in that: The copper block (12) and the substrate (11) are fitted with a locking part (2), and the substrate (11) is provided with a substrate fitting groove (21). The locking part (2) includes a slot (22) formed on the outer edge of the copper block (12) and a receiving slot (23) formed on the inner wall of the substrate fitting slot (21). The receiving groove (23) and the card slot (22) are both filled with a filling material that melts and expands when heated and solidifies after cooling, forming a three-dimensional mechanical interlock.

2. The copper-embedded printed circuit board as described in claim 1, characterized in that: The cross-sectional shape of the receiving groove (23) and the card slot (22) is trapezoidal.

3. The copper-embedded printed circuit board as described in claim 2, characterized in that: The filler material is a modified epoxy hot melt filler material.

4. The copper-embedded printed circuit board as described in claim 3, characterized in that: The single-sided gap between the copper block (12) and the substrate fitting groove (21) is 10-100 micrometers.

5. The copper-embedded printed circuit board as described in claim 4, characterized in that: The copper block (12) has a nickel plating layer on its surface, and the inner wall of the substrate fitting groove (21) has a roughening treatment layer.

6. A processing method for a copper-embedded printed circuit board as described in claim 5, characterized in that, Includes the following steps: S1: Substrate mating groove processing: A substrate mating groove (21) for accommodating copper block (12) is processed on the substrate (11), and a receiving groove (23) structure is processed on the inner wall of the substrate mating groove (21); S2: Copper block (12) pretreatment: Cut and grind the copper block (12) and process the groove (22) on its outer edge. S3: Surface treatment: The surface of the copper block (12) is plated, and the inner wall of the substrate fitting groove (21) is cleaned. S4: Pre-filling material: Pre-filling material in the receiving groove (23); S5: Fitting Assembly: Insert the copper block (12) into the receiving groove (23) of the substrate (11) and perform alignment correction; S6: Hot pressing curing: The filling material is melted, expanded and filled into the space of the receiving groove (23) and the card slot (22) by hot pressing process, and the cooling rate is controlled to solidify the filling material to form a mechanical interlocking structure.

7. The processing technology of the copper-embedded printed circuit board as described in claim 6, characterized in that: The substrate fitting groove (21) is processed by a high-precision CNC milling machine, and the dimensional tolerance is controlled within ±0.05mm.

8. The processing technology of the copper-embedded printed circuit board as described in claim 7, characterized in that: The hot-pressing curing is carried out in a vacuum environment, and the hot-pressing temperature is set according to the melting point of the filler material.

9. The processing technology of the copper-embedded printed circuit board as described in claim 8, characterized in that: The pressure applied during the hot-press curing process is 0.5-5 MPa, the holding time is 30-180 seconds, and the cooling rate is 1-5℃ / minute until the temperature drops below 50℃.

10. The processing technology of the copper-embedded printed circuit board as described in claim 9, characterized in that: It also includes subsequent processing steps: cleaning the completed circuit board and inspecting the interface quality using an ultrasonic scanning microscope.

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