A hole processing method for a circuit board and a multilayer circuit board

Abstract

The application discloses a hole processing method of a circuit board and a multilayer circuit board. The multilayer circuit board comprises a circuit board body, a conductive hole is arranged on the circuit board body, and the inner wall of the conductive hole is provided with a ring-shaped conductive layer; the inner wall of the conductive layer is provided with a resin ceramic composite part, and the resin ceramic composite part fills the inner ring surface of the conductive layer; and the ceramic powder concentration of the resin ceramic composite part gradually increases along the direction close to the axis of the conductive hole. Specifically, the resin content of the resin ceramic composite part close to the inner wall of the conductive layer is relatively high, and the ceramic powder content is relatively low; the high proportion of the resin ensures excellent interface adhesion with the copper layer, and effectively prevents the interface separation phenomenon; and along the direction close to the axis of the conductive hole, the ceramic powder concentration gradually increases, so that the thermal expansion coefficient of the composite material gradually decreases and approaches the thermal expansion coefficient of the copper layer, thereby reducing the stress accumulation in the thermal cycle process, preventing the generation of cracks and burst holes, and having good interface adhesion and thermal expansion coefficient matching.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of multilayer circuit board structure, and particularly relates to a hole processing method of a circuit board and a multilayer circuit board. BACKGROUND

[0002] The multilayer circuit board is a circuit board formed by alternately stacking a plurality of conductive pattern layers and insulating layers, and is widely used in the fields of computers, communication equipment, consumer electronics and aerospace. With the development of electronic products towards lightness, thinness, smallness, high speed, high frequency and high reliability, the design and manufacturing technology of the multilayer circuit board is also constantly innovated, and in particular, the filling technology of the conductive hole becomes a key factor affecting the performance and reliability of the product. In the multilayer circuit board, the conductive hole is an important channel connecting different conductive layers, and the inner wall of the conductive hole is usually plated with a layer of copper to form a ring-shaped conductive layer to realize the electrical interconnection function. In the high-density interconnection and high-frequency high-speed application scenarios, the conductive hole usually needs to be filled (i.e., "hole plugging") to improve the mechanical strength, flatness, heat dissipation performance and electrical performance of the multilayer circuit board.

[0003] At present, the common conductive hole filling treatment in the industry mainly has the following ways: one is pure resin filling, using organic high polymer materials such as epoxy resin and polypropylene to fill the conductive hole, and the resin has good adhesion with the copper layer, but the thermal conductivity is low, the thermal expansion coefficient is greatly different from the copper layer, and stress concentration is easily generated under thermal cycling conditions, resulting in cracks and burst holes; the other is conductive material filling, using conductive paste (such as conductive silver paste) to fill the conductive hole, which can realize the electrical conduction of the conductive hole, and the difference in thermal expansion coefficient is small, but the interface between the conductive paste and the copper layer is prone to poor contact, that is, the interface between the conductive paste and the copper layer is prone to separation.

[0004] In summary, the resin filling scheme is prone to cracks and burst holes, and the conductive material scheme is prone to interface separation. Therefore, the hole processing technology in the prior art cannot simultaneously solve the problems of easy crack and easy interface separation in the filling area of the conductive hole. SUMMARY

[0005] The present application aims to provide a hole processing method of a circuit board and a multilayer circuit board, which solves the problem that the filling area of the conductive hole in the prior art is difficult to simultaneously solve the problems of easy crack and easy interface separation.

[0006] To achieve this goal, the present application adopts the following technical scheme:

[0007] A multilayer circuit board, comprising a circuit board body, a conductive hole is formed in the circuit board body, and the inner wall of the conductive hole is provided with a ring-shaped conductive layer;

[0008] The inner wall of the conductive layer is provided with a resin ceramic composite part, and the resin ceramic composite part fills the inner annular surface of the conductive layer; the ceramic powder concentration of the resin ceramic composite part increases along the axis direction close to the conductive hole.

[0009] Optionally, the resin ceramic composite part comprises a resin ceramic column and a plurality of resin ceramic rings successively sleeved outside the resin ceramic column from inside to outside.

[0010] Optionally, the conductive layer comprises an integrally formed conductive outer layer and a conductive inner layer, the height of the conductive outer layer is the same as the depth of the conductive hole, and the height of the conductive inner layer is less than the height of the conductive outer layer, so that a connecting groove is formed between the conductive inner layer and the hole edge of the conductive hole.

[0011] Optionally, the connecting groove is provided with a resin connecting part, and the resin connecting part is connected with the conductive layer and the resin ceramic composite part, respectively.

[0012] A hole processing method of a circuit board for preparing the multilayer circuit board described above, comprising:

[0013] Step S100, providing a circuit board body, the circuit board body is provided with a conductive hole, and the inner wall of the conductive hole is provided with a conductive layer in the form of a ring;

[0014] Step S200, providing a resin ceramic composite part on the inner wall of the conductive layer, and the ceramic powder concentration of the resin ceramic composite part increases along the axis direction close to the conductive hole.

[0015] Optionally, the step S200 comprises:

[0016] Step S201, preparing a plurality of groups of mixtures of resin powder and ceramic powder with different proportions, wherein the concentration of ceramic powder in different mixtures increases successively;

[0017] Step S202, filling the mixture with the lowest concentration of ceramic powder in the area close to the inner wall of the conductive layer through a screen plate;

[0018] Step S203, slightly curing the filled first layer of mixture, and the slight curing temperature is 75-85℃;

[0019] Step S204, filling the next group of mixture with higher concentration of ceramic powder in the area close to the axis direction of the conductive hole through the screen plate;

[0020] Step S205, slightly curing the newly filled layer of mixture, and the slight curing temperature is 75-85℃;

[0021] Step S206, repeating steps S204 to S205, sequentially completing the filling of all mixture layers, forming a resin-ceramic composite part with the ceramic powder concentration increasing along the direction close to the axis of the conductive hole;

[0022] Step S207, performing a hot pressing process on the resin-ceramic composite part that has completed filling.

[0023] Optionally, the step S100 comprises:

[0024] Step S101, performing first electroplating on the circuit board body with a conductive hole, forming a conductive outer layer on the inner wall of the conductive hole, the height of the conductive outer layer being the same as the depth of the conductive hole;

[0025] Step S102, performing second electroplating on the inner wall of the conductive outer layer, forming a conductive inner layer on the inner wall of the conductive outer layer, obtaining a conductive layer; wherein the height of the conductive inner layer is less than the height of the conductive outer layer, so that a connecting groove is formed between the conductive inner layer and the hole edge of the conductive hole;

[0026] The step S200 comprises:

[0027] Step S211, providing a solvent transport part on the connecting groove;

[0028] Step S212, providing a uniform mixture of resin powder and ceramic powder, and filling the uniform mixture into the conductive hole;

[0029] Step S213, injecting cyclohexane solvent into the solvent transport part, using capillary action to make the cyclohexane solvent penetrate in the axial direction, forming a solvent concentration gradient, the solvent concentration gradient decreasing along the direction close to the axis, and the resin powder migrating away from the axis;

[0030] Step S214, removing the cyclohexane solvent and the solvent transport part, obtaining a resin-ceramic composite part.

[0031] Optionally, the process of removing the cyclohexane solvent comprises:

[0032] Step S221, placing the treated circuit board body in a volatile environment for 2-4h;

[0033] Step S222, slowly increasing the temperature to 55-65℃ and maintaining for 1-2h;

[0034] Step S223, placing the circuit board body in a vacuum environment and maintaining the temperature at 40-50℃ for 30-60min.

[0035] Optionally, the material of the solvent transport part is modified polyvinyl alcohol;

[0036] The process of removing the solvent transport part comprises:

[0037] Step S231, immerse the circuit board body in deionized water at 35-45°C, and slightly stir to promote the dissolution of the modified polyvinyl alcohol;

[0038] Step S232, use deionized water at a temperature of 40-50°C to rinse the circuit board multiple times;

[0039] Step S233, place the cleaned circuit board in an oven or dry it using nitrogen blowing, and perform drying treatment.

[0040] Optionally, the step S200 further comprises:

[0041] Step S215, after the resin ceramic composite part is formed and the solvent transmission part is removed, a resin connecting part is arranged in the connecting groove.

[0042] Compared with the prior art, the present application has the following beneficial effects:

[0043] The hole processing method of the circuit board and the multilayer circuit board provided by the present application adopt a resin ceramic composite part with a ceramic powder concentration increasing along the axis direction close to the conductive hole, the resin content is higher and the ceramic powder content is lower in the resin ceramic composite part close to the inner wall area of the conductive layer, the high proportion of the resin ensures good interface adhesion with the copper layer, and effectively prevents the interface separation phenomenon; and as extending to the axis direction of the conductive hole, the ceramic powder concentration gradually increases, so that the thermal expansion coefficient of the composite material gradually decreases and matches the thermal expansion coefficient of the copper layer, thereby reducing the stress accumulation in the thermal cycle process and effectively preventing the generation of cracks and burst holes. It can be seen that the hole processing method of the circuit board and the multilayer circuit board provided by the present application simultaneously solve the phenomena of cracks, burst holes and interface separation in the conventional plug hole process, so that the multilayer circuit board can simultaneously have good interface adhesion and thermal expansion coefficient matching. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0045] The structure, proportion, size and the like shown in the drawings of the specification are only used to cooperate with the content disclosed in the specification, to be understood and read by those skilled in the art, and do not have technical significance, and any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effects and purposes that can be achieved by the present application, should still fall within the scope of the disclosed technology.

[0046] Figure 1 A first state structure schematic diagram of a multilayer circuit board provided by an embodiment of the present application;

[0047] Figure 2 A second state structure schematic diagram of a multilayer circuit board provided by an embodiment of the present application;

[0048] Figure 3 A third state structure schematic diagram of a multilayer circuit board provided by an embodiment of the present application;

[0049] Figure 4 A fourth state structure schematic diagram of a multilayer circuit board provided by an embodiment of the present application;

[0050] Figure 5 A fifth state structure schematic diagram of a multilayer circuit board provided by an embodiment of the present application;

[0051] Figure 6 A sixth state structure schematic diagram of a multilayer circuit board provided by an embodiment of the present application;

[0052] Figure 7 A seventh state structure schematic diagram of a multilayer circuit board provided by an embodiment of the present application;

[0053] Illustration: 100, circuit board body; 110, conductive hole; 120, conductive layer; 121, conductive outer layer; 122, conductive inner layer; 130, connecting groove; 200, resin ceramic composite part; 210, resin ceramic column; 220, resin ceramic ring; 300, resin connecting part; 400, solvent transmission part. DETAILED DESCRIPTION

[0054] In order to make the invention purpose, features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the following described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0055] In the description of the present application, it should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there can be a component disposed therebetween.

[0056] The technical solutions of the present application will be further described below in conjunction with the drawings and through specific embodiments.

[0057] Embodiment one:

[0058] The multilayer circuit board in this embodiment mainly covers the fields of high-frequency, high-speed electronic products and high-reliability requirements; especially in products that require circuit boards to have excellent thermal stability, stress resistance and long service life, this multilayer circuit board has a wide application prospect. The multilayer circuit board provided in this embodiment can effectively solve the problems of cracks, burst holes and interface separation in the prior art, greatly improving the stability of the multilayer circuit board in harsh environments such as high frequency and thermal cycling, thereby meeting the requirements of high-performance electronic equipment for multilayer circuit boards.

[0059] As shown in Figure 7 The multilayer circuit board in this embodiment includes a circuit board body 100, the circuit board body 100 is provided with a conductive hole 110, and the inner wall of the conductive hole 110 is provided with a ring-shaped conductive layer 120; wherein the inner wall of the conductive layer 120 is provided with a resin-ceramic composite part 200, and the resin-ceramic composite part 200 fills the inner annular surface of the conductive layer 120; the ceramic powder concentration of the resin-ceramic composite part 200 increases along the axis direction close to the conductive hole 110. In this embodiment, the resin-ceramic composite part 200 is composed of polypropylene powder and ceramic powder, and the conductive layer 120 is a copper plating layer.

[0060] Specifically, the resin ceramic composite part 200 is adopted with the ceramic powder concentration increasing along the axis direction close to the conductive hole 110, the resin content is higher and the ceramic powder content is lower in the resin ceramic composite part 200 close to the inner wall area of the conductive layer 120, the high proportion of resin ensures the excellent interface adhesion with the copper layer, and effectively prevents the interface separation phenomenon; and as extending to the axis direction of the conductive hole 110, the ceramic powder concentration gradually increases, so that the thermal expansion coefficient of the composite material gradually decreases and matches the thermal expansion coefficient of the copper layer, thereby reducing the stress accumulation in the thermal cycle process and effectively preventing the generation of cracks and burst holes. It can be seen that the multilayer circuit board provided in the embodiment simultaneously solves the phenomena of cracks, burst holes and interface separation in the conventional plug hole process, so that the multilayer circuit board can simultaneously have good interface adhesion and thermal expansion coefficient matching.

[0061] Specifically, the resin ceramic composite part 200 includes a resin ceramic column 210 and a plurality of resin ceramic rings 220 sequentially sleeved outside the resin ceramic column 210 from inside to outside. In the embodiment, the outer side of the resin ceramic column 210 is sequentially sleeved with three resin ceramic rings 220, the size of which increases in turn, and the proportion of resin powder continuously increases. As other optional embodiments, the number of resin ceramic rings 220 is four or five, which is not limited in the embodiment.

[0062] Further, the conductive layer 120 includes an integrally formed conductive outer layer 121 and a conductive inner layer 122, the height of the conductive outer layer 121 is the same as the depth of the conductive hole 110, and the height of the conductive inner layer 122 is less than the height of the conductive outer layer 121, so that the connecting groove 130 is formed between the conductive inner layer 122 and the hole edge of the conductive hole 110. Through the above setting, the top of the conductive layer 120 is disconnected with the resin ceramic composite part 200, the disconnection is limited to the top layer, the connection between the conductive layer 120 and the bottom of the resin ceramic composite part 200 is maintained, and the structural stability between the conductive layer 120 and the resin ceramic composite part is ensured.

[0063] The resin connecting part 300 is arranged in the connecting groove 130 and connected with the conductive layer 120 and the resin ceramic composite part 200. The resin connecting part 300 arranged in the connecting groove 130 can improve the mechanical stability between the conductive layer 120 and the resin ceramic composite part 200. Specifically, the resin connecting part 300 can be made of epoxy resin material. The epoxy resin has excellent interface adhesion and can form stable chemical combination with the conductive layer 120 and the resin ceramic composite part 200. The epoxy resin has low thermal expansion coefficient and can keep good thermal expansion matching with other materials (such as the conductive layer 120 and the resin ceramic composite part 200) in the thermal cycle process, thereby reducing the accumulation of thermal stress. Therefore, the arrangement of the resin connecting part 300 can effectively avoid the interface separation between the conductive layer 120 and the resin ceramic composite part 200 and reduce the stress accumulation caused by the difference in thermal expansion coefficient.

[0064] Embodiment two:

[0065] The hole processing method of the circuit board provided in the embodiment is used for preparing the multilayer circuit board in the embodiment one, and includes the following steps.

[0066] As shown in the figure, Figures 1-2 Step S100, a circuit board body 100 is provided, and a conductive hole 110 is arranged on the circuit board body. The inner wall of the conductive hole 110 is provided with a conductive layer 120 in the form of a ring.

[0067] As shown in the figure, Figures 3-7 Step S200, a resin ceramic composite part 200 is arranged on the inner wall of the conductive layer 120. The ceramic powder concentration of the resin ceramic composite part 200 increases along the axis direction close to the conductive hole 110.

[0068] Specifically, the resin ceramic composite part 200 with the ceramic powder concentration increasing along the axis direction close to the conductive hole 110 has higher resin content and lower ceramic powder content in the region close to the inner wall of the conductive layer 120. The high proportion of resin ensures the excellent interface adhesion with the copper layer and effectively prevents the interface separation. With the extension to the axis direction of the conductive hole 110, the ceramic powder concentration gradually increases, so that the thermal expansion coefficient of the composite material gradually decreases and matches the thermal expansion coefficient of the copper layer, thereby reducing the stress accumulation in the thermal cycle process and effectively preventing the generation of cracks and burst holes. It can be seen that the hole processing method of the circuit board provided in the embodiment can solve the problems of cracks, burst holes and interface separation in the conventional hole plugging process, so that the multilayer circuit board processed by the hole processing method can have good interface adhesion and thermal expansion coefficient matching.

[0069] As an optional embodiment, step S200 includes the following steps.

[0070] Step S201, prepare a plurality of groups of mixtures of resin powder and ceramic powder with different proportions, wherein the concentration of ceramic powder in different mixtures is sequentially increased;

[0071] Step S202, fill the mixture with the lowest concentration of ceramic powder in the area close to the inner wall of the conductive layer through the screen plate; wherein the screen plate has different sizes corresponding to mixtures with different concentrations of ceramic powder, and in step S202, the screen plate has a size of the largest annular structure that can be fitted in the inner wall of the conductive layer, and the largest annular structure has a spacing with the inner wall of the conductive layer, and the spacing allows the subsequent first layer of mixture to be formed into the outermost resin ceramic ring 220;

[0072] Step S203, lightly cure the filled first layer of mixture, and the light curing temperature is 75-85℃; the light curing method is not limited, and can be selected from infrared heating, oven heating and the like, which can heat the first layer of mixture at a specified temperature;

[0073] Step S204, fill the next group of mixtures with higher concentration of ceramic powder in the area close to the axis direction of the conductive hole through the screen plate; wherein the screen plate has different sizes corresponding to mixtures with different concentrations of ceramic powder, and in step S204, the screen plate has a size of the annular structure that gradually decreases, thereby sequentially forming resin ceramic rings 220 with decreasing sizes, and finally obtaining the resin ceramic column 210 with a screen plate without annular structure;

[0074] Step S205, lightly cure the newly filled mixture layer, and the light curing temperature is 75-85℃;

[0075] Step S206, repeat steps S204 to S205 to sequentially complete the filling of all mixture layers, and form a resin ceramic composite part with the concentration of ceramic powder increasing along the direction close to the axis of the conductive hole;

[0076] For example, with a three-layer structure, after the first layer of mixture is lightly cured, a screen plate with another annular structure of the second largest size is used to fill the second layer of mixture (the concentration of ceramic powder of the second layer of mixture is reduced) inside the first layer of mixture (the outermost resin ceramic ring 220); after the second layer of mixture is lightly cured, a screen plate without annular structure is used to fill the third layer of mixture inside the second layer of mixture (the middle layer of resin ceramic ring 220), and after light curing, the resin ceramic column 210 is obtained.

[0077] Step S207, the resin ceramic composite part filled is subjected to a hot-pressing treatment. The hot-pressing treatment is implemented by a double-sided hot press, and the principle of hot-pressing is well known to those skilled in the art, which will not be specifically expanded in the present embodiment. In the process of hot-pressing, the first layer of mixture (the outermost resin ceramic ring 220) is connected with the conductive layer 120.

[0078] As another optional embodiment, as shown in Figure 3 Step S100 includes:

[0079] Step S101, first electroplating is performed on the circuit board body provided with the conductive hole 110, and a conductive outer layer 121 is formed on the inner wall of the conductive hole 110, the height of the conductive outer layer 121 being the same as the depth of the conductive hole 110;

[0080] Step S102, second electroplating is performed on the inner wall of the conductive outer layer 121, and a conductive inner layer 122 is formed on the inner wall of the conductive outer layer 121, to obtain the conductive layer 120; wherein the height of the conductive inner layer 122 is less than the height of the conductive outer layer 121, so as to form a connecting groove 130 between the conductive inner layer 122 and the hole edge of the conductive hole 110;

[0081] Step S200 includes:

[0082] As shown in Figures 3-4 Step S211, a solvent transport part 400 is provided on the connecting groove 130;

[0083] As shown in Figure 5 Step S212, a uniform mixture of resin powder and ceramic powder is provided, and the uniform mixture is filled into the conductive hole 110;

[0084] Step S213, cyclohexane solvent is injected into the solvent transport part 400, and the cyclohexane solvent is penetrated in the axial direction by capillary action, to form a solvent concentration gradient, the solvent concentration gradient decreasing in the direction close to the axis, so as to make the resin powder migrate in the direction away from the axis;

[0085] As shown in Figure 6 Step S214, the cyclohexane solvent and the solvent transport part 400 are removed, to obtain the resin ceramic composite part 200.

[0086] The solvent transport part 400 is made of modified polyvinyl alcohol, polyacrylamide, etc., and the modified polyvinyl alcohol is taken as an example. The modified polyvinyl alcohol has solvent transport capacity and structural stability, and has excellent water-soluble properties for subsequent removal. The modified polyvinyl alcohol is formed into a ring block by chemical crosslinking method, extrusion molding, mold pressing, etc., so as to be conveniently arranged on the connecting groove 130. Then injection process, dipping process, etc. can be used to make the solvent transport part 400 full of cyclohexane solvent.

[0087] Exemplarily, in the first stage, when the cyclohexane solvent is released to the hole wall area through the modified polyvinyl alcohol, the solvent molecules first contact the resin powder near the hole wall. Due to the strong affinity between the resin powder and the solvent, the solvent molecules quickly infiltrate and dissolve the resin powder near the hole wall, which follows Fick's diffusion law, and the solvent molecules diffuse from the high concentration area to the low concentration area. In this stage, the solvent forms a high concentration area in the hole wall area, while the hole center area has not yet been contacted by the solvent. The surface of the resin powder particles in the hole wall area begins to dissolve, forming a colloidal layer, and the boundary between the particles begins to blur, but no obvious flow has occurred. This stage mainly establishes the initial solvent concentration gradient, laying the foundation for subsequent material migration.

[0088] In the second stage, over time, the solvent continues to penetrate radially towards the center of the hole, but due to capillary effect and diffusion resistance, the penetration speed of the solvent gradually slows down, and the concentration also decays with the increase of distance. At this time, a solvent concentration gradient is formed from the hole wall-middle area-center area, and the solvent concentration gradient shows a downward trend. Due to the gradient setting of the solvent concentration everywhere, the resin powder can correspondingly migrate, thus forming the phenomenon of "more outside and less inside";

[0089] In the third stage, the solvent has penetrated into various areas, forming a relatively stable concentration gradient. At this time, the redistribution of the resin has been basically completed: exemplarily, the resin content in the hole wall area (corresponding to the outermost resin ceramic ring 220) reaches 95%, and the ceramic powder accounts for 5%, ensuring good adhesion with the copper layer; the middle transition area (corresponding to the intermediate layer of the resin ceramic ring 220) forms a mixed ratio of about 75% resin and 25% ceramic; the center core area (corresponding to the resin ceramic column 210) forms a mixed ratio of about 30% resin and 70% ceramic, providing low thermal expansion coefficient and good heat dissipation performance. The above-mentioned manner is different from the general multi-layer stacking method. The migration of the resin powder follows the principle of self-organization, and a continuously changing composition distribution is spontaneously formed under the driving of the solvent concentration gradient, avoiding the obvious interface and stress concentration area that may occur in the traditional multi-layer filling, thereby improving the overall performance and reliability of the filled structure, and from the process, it can be once formed without repeated operation.

[0090] Specifically, the process of removing the cyclohexane solvent includes:

[0091] Step S221, placing the processed circuit board body 100 in a volatile environment for 2-4h;

[0092] Step S222, slowly increasing the temperature to 55-65℃ and maintaining for 1-2h;

[0093] Step S223, placing the circuit board body 100 in a vacuum environment (20-30Pa) and maintaining the temperature at 40-50℃ for 30-60min.

[0094] Specifically, the material of the solvent transmission part 400 is modified polyvinyl alcohol;

[0095] The process of removing the solvent transmission part 400 includes:

[0096] Step S231, immerse the circuit board body 100 in deionized water at 35-45°C, and slightly stir to promote the dissolution of the modified polyvinyl alcohol;

[0097] Step S232, use deionized water at a temperature of 40-50°C to rinse the circuit board multiple times;

[0098] Step S233, place the cleaned circuit board in an oven or use nitrogen to dry, and perform drying treatment.

[0099] It should be noted that, as shown in Figure 7 Step S200 further includes:

[0100] Step S215, after the resin ceramic composite part 200 is formed and the solvent transmission part 400 is removed, set the resin connecting part 300 in the connecting groove 130. Specifically, the resin connecting part 300 is epoxy resin which can be formed by injection and curing. The above-mentioned forming method is well known to those skilled in the art, and will not be specifically expanded in the present embodiment.

[0101] The above-described embodiments are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A multilayer circuit board, characterized in that: It comprises a circuit board body (100), wherein a conductive hole (110) is provided on the circuit board body (100), and an inner wall of the conductive hole (110) is provided with a ring-shaped conductive layer (120); The inner wall of the conductive layer (120) is provided with a resin-ceramic composite part (200), and the resin-ceramic composite part (200) fills the inner annular surface of the conductive layer (120); the ceramic powder concentration of the resin-ceramic composite part (200) increases along the axial direction close to the conductive hole (110); The resin-ceramic composite part (200) comprises a resin-ceramic column (210) and a plurality of resin-ceramic rings (220) sequentially sleeved on the outside of the resin-ceramic column (210) from the inside to the outside; The conductive layer (120) comprises an integrally formed conductive outer layer (121) and a conductive inner layer (122), the height of the conductive outer layer (121) being the same as the depth of the conductive hole (110), and the height of the conductive inner layer (122) being smaller than the height of the conductive outer layer (121), so as to form a connecting groove (130) between the conductive inner layer (122) and the edge of the conductive hole (110); A resin connection portion (300) is provided in the connection groove (130), and the resin connection portion (300) is respectively connected to the conductive layer (120) and the resin-ceramic composite portion (200).

2. A method for processing a hole in a circuit board, characterized in that: For preparing the multilayer circuit board according to claim 1, comprising: Step S100: providing a circuit board body, wherein a conductive hole is formed on the circuit board body, and an inner wall of the conductive hole is provided with a ring-shaped conductive layer; Step S200 : providing a resin-ceramic composite portion on the inner wall of the conductive layer, wherein the ceramic powder concentration of the resin-ceramic composite portion increases gradually along the axis direction close to the conductive hole.

3. A method for processing a hole in a circuit board according to claim 2, characterized in that: The step S200 includes: Step S201: preparing multiple mixtures of resin powder and ceramic powder in different proportions, wherein the concentration of ceramic powder increases sequentially in different mixtures; Step S202: Filling the mixture with the lowest ceramic powder concentration into the area close to the inner wall of the conductive layer through the screen; Step S203: lightly curing the first layer of the mixture, wherein the light curing temperature is 75-85° C.; Step S204: Filling the area close to the axis of the conductive hole with the next group of mixtures having a higher ceramic powder concentration through the screen; Step S205: lightly curing the newly filled mixture layer at a temperature of 75-85° C.; Step S206, repeating steps S204 to S205 to sequentially complete the filling of all mixture layers, forming a resin-ceramic composite portion in which the ceramic powder concentration increases along the direction close to the axis of the conductive hole; Step S207 , performing a thermal compression process on the filled resin-ceramic composite part.

4. A method for processing a hole in a circuit board according to claim 2, characterized in that: The step S100 includes: Step S101: performing a first electroplating on a circuit board body having a conductive hole, forming a conductive outer layer on the inner wall of the conductive hole, wherein the height of the conductive outer layer is the same as the depth of the conductive hole; Step S102: performing a second electroplating on the inner wall of the conductive outer layer to form a conductive inner layer on the inner wall of the conductive outer layer to obtain a conductive layer; wherein the height of the conductive inner layer is smaller than the height of the conductive outer layer, so as to form a connecting groove between the conductive inner layer and the edge of the conductive hole; The step S200 includes: Step S211, setting a solvent transfer part on the connecting tank; Step S212: providing a uniform mixture of resin powder and ceramic powder, and filling the conductive hole with the uniform mixture; Step S213: injecting cyclohexane solvent into the solvent transfer part, and using capillary action to make the cyclohexane solvent penetrate toward the axis, forming a solvent concentration gradient, which decreases in the direction close to the axis, causing the resin powder to migrate away from the axis; Step S214: removing the cyclohexane solvent and the solvent transfer part to obtain a resin-ceramic composite part.

5. A method for processing a hole in a circuit board according to claim 4, characterized in that: The process of removing cyclohexane solvent includes: Step S221: placing the processed circuit board body in a volatile environment for 2 to 4 hours; Step S222, slowly raising the temperature to 55-65°C and maintaining it for 1-2 hours; Step S223: Place the circuit board body in a vacuum environment and maintain the temperature at 40-50° C. for 30-60 minutes.

6. A method for processing a hole in a circuit board according to claim 4, characterized in that: The material of the solvent transmission part is modified polyvinyl alcohol; The process of removing the solvent delivery section includes: Step S231: Soak the circuit board body in deionized water at 35-45° C. and gently stir to promote the dissolution of the modified polyvinyl alcohol; Step S232: rinse the circuit board multiple times with deionized water at a temperature of 40-50°C; Step S233: Place the cleaned circuit board in an oven or blow dry it with nitrogen gas for drying.

7. A method for processing a hole in a circuit board according to claim 4, characterized in that: The step S200 further includes: Step S215 : After the resin-ceramic composite part is formed and the solvent transfer part is removed, a resin connection part is provided in the connection groove.

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