Circuit board manufacturing method and circuit board

Abstract

The invention discloses a circuit board manufacturing method and a circuit board. The circuit board manufacturing method comprises the following steps: providing a daughter board; forming a first groove on the daughter board; filling the first groove with a metal filler; pressing the daughter boards to form a mother board; a plated-through hole is manufactured, the plated-through hole is provided with a metal wall used for conducting the circuit pattern of each layer, and the plated-through hole penetrates through the metal filler; forming a via hole in the mother board to expose the metal filler; a dissolving agent is introduced into the first groove through the via hole to dissolve or destroy the metal filler, and the components of the dissolving agent comprise metal; removing the metal filler to form a cavity on the mother board; and disconnecting the metal wall corresponding to the cavity. Therefore, while the conduction requirement of the circuit pattern can be met, the filler can be removed after the circuit board is pressed, and the performance of the circuit board is ensured. The circuit board is widely applied to the technical field of circuit boards.

Description

Technical Field

[0001] The present application relates to the technical field of circuit boards, and in particular to a method for manufacturing a circuit board and a circuit board. Background Art

[0002] Circuit boards use metallized holes to connect circuit patterns on different layers. In some special scenarios, circuit patterns on certain layers are required to be disconnected. In related technologies, cavities are usually made in circuit boards to achieve the effect of disconnecting specified layers. Currently, cavities are made in circuit boards by opening windows in advance. However, during the lamination process of the circuit boards, PP glue will fill the cavity area, or the circuit boards will sag in the cavity area, affecting the size of the cavity. Therefore, in order to ensure the size of the cavity, fillers are usually set at the window opening position and removed after lamination. However, since the commonly used fillers are hard gaskets, the fillers are often exposed by milling grooves to remove the fillers to form a cavity. At this time, the size of the slot must be larger than the filler, which makes it difficult to close the slot, affecting the performance of the circuit board. Summary of the invention

[0003] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a circuit board manufacturing method and a circuit board, which can meet the conduction requirements of the circuit pattern while facilitating the removal of fillers after the circuit board is pressed and ensuring the performance of the circuit board.

[0004] According to the first aspect of the present application, a circuit board manufacturing method includes:

[0005] Provide daughterboard;

[0006] forming a first groove on the daughter board;

[0007] filling the first groove with a metal filler;

[0008] Pressing the daughter boards to form a mother board;

[0009] Making a metallized hole, wherein the metallized hole has a metal wall for conducting the circuit patterns of each layer, and the metallized hole penetrates the metal filler;

[0010] forming a via hole on the motherboard to expose the metal filler;

[0011] Passing a dissolving agent into the first groove through the through hole to dissolve or destroy the metal filler, wherein the dissolving agent comprises a metal;

[0012] removing the metal filler to form a cavity on the motherboard;

[0013] The metal wall corresponding to the cavity is disconnected.

[0014] According to the circuit board manufacturing method of the embodiment of the present application, at least the following beneficial effects are achieved: by filling the cavity of the circuit board with metal fillers before lamination, the cavity can withstand the extrusion force of the flowing glue, so as to block the flowing glue during the lamination process of the circuit board and prevent the flowing glue from occupying the cavity area, and due to the incompressibility of the metal, the circuit board can be supported by the metal filler, which can prevent the circuit board from being sunken and deformed, so that the structure of the cavity remains stable to ensure the size of the cavity, and at the same time, the metal is used as a dissolving agent for the metal filler, and the metal filler is dissolved into a liquid or destroyed to form an easily crushable alloy after the circuit board is pressed, so as to be discharged from the circuit board through the small hole, thereby facilitating the removal of the metal filler, and at this time, there is no need to open a large-sized slot on the circuit board, which is conducive to maintaining the cavity shape on the circuit board to ensure the performance of the circuit board. In addition, by setting a metallized hole to penetrate the metal filler, only a metal wall is left between the cavity and the metallized hole after the metal filler is removed, which can facilitate the disconnection of the metal wall between the upper and lower layers where the cavity is located, and realize the disconnection of the circuit pattern of the specified layer to meet the conduction requirements of the circuit board.

[0015] According to some embodiments of the present application, the dissolving agent is further used to dissolve the metal wall, or to apply pressure to the metal wall corresponding to the cavity to disconnect the metal wall corresponding to the cavity.

[0016] According to some embodiments of the present application, when the solvent is used to dissolve the metal wall, the metallized hole is filled before the solvent is introduced; when the metal wall corresponding to the cavity is disconnected by pressure destruction, the filler of the metallized hole is removed before pressure is applied to the metal wall.

[0017] According to some embodiments of the present application, the filler of the metallized hole is a non-metallic material.

[0018] According to some embodiments of the present application, when the component of the metal filler includes aluminum and the component of the solvent includes mercury, the solvent reacts with the metal filler to obtain a solid alloy, which fills the conductive hole so that the metal wall is disconnected under the extrusion of the solid alloy.

[0019] According to some embodiments of the present application, the solid alloy is removed from the cavity after being pulverized by ultrasonic vibration or pressurization.

[0020] According to some embodiments of the present application, the step of making a metallized hole includes:

[0021] Drilling a first hole in the motherboard to penetrate the metal filler;

[0022] oxidizing the metal filler through the first hole;

[0023] Copper is deposited in the first hole to form a metallized hole.

[0024] According to some embodiments of the present application, the projection of the metallized hole is located within the projection of the metal filling.

[0025] According to some embodiments of the present application, the size of the metal filler is larger than the aperture of the metallized hole, and the difference between the size of the metal filler and the size of the metallized hole is 2mil-5mil.

[0026] The circuit board according to the embodiment of the second aspect of the present application is prepared by using the circuit board manufacturing method as described in the first aspect above.

[0027] The circuit board according to the embodiment of the present application has at least the following beneficial effects: while being able to meet the conduction requirements of the circuit pattern, it is also conducive to removing the filler after the circuit board is pressed together and ensuring the performance of the circuit board.

[0028] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present application is further described below with reference to the accompanying drawings and embodiments, wherein:

[0030] Figure 1 A flowchart of a circuit board manufacturing method disclosed in an embodiment of the present application;

[0031] Figure 2 A schematic diagram of the principle of the circuit board manufacturing method disclosed in the embodiment of the present application when manufacturing disconnected metallized holes;

[0032] Figure 3 An exemplary flow chart of making metallized holes on a daughter board disclosed in an embodiment of the present application;

[0033] Figure 4 for Figure 3 Schematic diagram of the principle of making metallized holes on the daughter board;

[0034] Figure 5 for Figure 3 Schematic diagram of the principle of disconnecting the metallized hole at the specified layer.

[0035] Reference numerals:

[0036] 100, daughter board; 101, core board; 102, bonding sheet; 200, metal filler; 300, via hole; 400, metallized hole; 500, metal wall; 600, oxide layer in the hole. DETAILED DESCRIPTION

[0037] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0038] In the description of the present application, it should be understood that the terms "center", "middle", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which 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 specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0039] In the description of this application, "several" means more than one, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0040] In the description of this application, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0041] In the description of the present application, if the reference terms "as an implementation", "an embodiment", "some instances", "some embodiments", "illustrative embodiment", "example", "specific example", "some examples", etc. appear, it means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0042] In order to achieve the disconnection effect between the circuit patterns of certain layers of the circuit board, a cavity is usually made in the circuit board, and a metallized hole passes through the cavity. The metal wall of the metallized hole is disconnected at the position of the cavity to achieve the disconnection effect at the specified layer. At the same time, for the method of making the cavity by opening a window in advance, in order to avoid the corresponding cavity area of ​​the circuit board from being concave and deformed during the lamination process, and the PP flow glue filling the cavity area, fillers are usually set at the window position, and the fillers are removed after lamination, and finally the metal wall of the metallized hole at the cavity position is disconnected.

[0043] In the related art, there are two ways to remove fillers: physical removal and chemical removal. Physical removal is to make an opening that completely exposes the filler by opening a window or a groove, and then take out the filler from the opening. At this time, the size of the opening needs to be larger than the size of the filler, which makes it difficult to close the opening after the filler is taken out. Chemical removal is to remove the filler by etching with a reagent. When the filler is close to the circuit pattern, chemical removal is likely to cause damage to the circuit pattern.

[0044] To this end, the present application provides a circuit board manufacturing method, which supports filling of cavities with metal fillers, and dissolves or destroys the metal fillers with a solvent including metal components to facilitate removal of the metal fillers, thereby meeting the conduction requirements of the circuit pattern while facilitating removal of the fillers after the circuit board is pressed together and ensuring the performance of the circuit board. In addition, the present application also provides a circuit board prepared using the circuit board manufacturing method.

[0045] Specifically, the circuit board manufacturing method proposed in this application achieves the technical objectives of this application based on the following chemical properties.

[0046] Amalgam, also known as mercury alloy, is an alloy formed by mercury and one or more other metals. Mercury has a unique property. It can dissolve a variety of metals (such as gold, silver, aluminum, copper, potassium, sodium, zinc, etc.), but rarely reacts with non-metallic materials (such as the plate of the sub-plate). After dissolving, it forms an alloy of mercury and these metals. This reaction phenomenon is called "amalgam reaction". Amalgam is solid when it contains less mercury, and liquid when it contains more mercury.

[0047] Similar metals can achieve the same effect, such as metallic gallium, which has a stronger ability to dissolve metals than metallic mercury. The alloy formed after dissolving the metal is liquid at room temperature. The metals that can be dissolved include aluminum, gold, silver and copper.

[0048] The present application uses metal fillers to fill the cavity of the circuit board before lamination. Since the hard metal filler has high temperature and high pressure resistance, it can provide a foundation for the cavity structure and withstand the extrusion force of the flow glue to block the flow glue during the lamination process of the circuit board to prevent the flow glue from occupying the cavity area. In addition, due to the incompressibility of the metal, it can support the circuit board during the lamination process to prevent the circuit board from being sunken and deformed, so that the structure of the cavity remains stable to ensure the size of the cavity. After the lamination is completed, a material including a dissolving agent of metal mercury is added to dissolve the hard metal filler to form a liquid alloy so that it can be discharged from the circuit board through the small hole, thereby facilitating the removal of the metal filler. At this time, there is no need to open a large-sized slot on the circuit board, which is conducive to maintaining the cavity structure on the circuit board to ensure the performance of the circuit board. In addition, by setting a metallized hole to penetrate the metal filler, only a metal wall is left between the cavity and the metallized hole after the metal filler is removed, which can facilitate the disconnection of the metal wall between the upper and lower layers where the cavity is located, and realize the disconnection of the circuit pattern of the specified layer to meet the conduction requirements of the circuit board.

[0049] It should be noted that, for most metal fillers (such as metal fillers made of at least one of gold, silver, potassium, sodium or zinc, etc.), when the material including metallic mercury is used as a solvent, a liquid alloy will be formed after the solvent contacts the metal filler. However, for some special metal fillers, such as metallic aluminum, a small amount of mercury will destroy a large amount of aluminum. At this time, the aluminum amalgam obtained is a brittle solid alloy, which will destroy the aluminum oxide protective film on the surface of the metal filler (aluminum), exposing the aluminum to the air, and then causing the aluminum to be oxidized by oxygen to generate white aluminum oxide solid. The aluminum oxide solid is very fragile and easy to crush. The crushed aluminum oxide and aluminum amalgam can be discharged through the small holes to form a cavity, thereby removing the metal filler from the circuit board.

[0050] In the embodiments of the present application, a small hole refers to a hole with a smaller size, for example, the small hole can be a via hole or a metallized hole, or it can be other holes that connect the cavity and are smaller than the cavity. Exemplarily, the via hole is used as a small hole to remove the metal filler. At this time, the size of the via hole can be smaller than the size of the cavity. The liquid alloy is formed by the solvent and the metal filler, and the flowability of the liquid alloy can be used to remove the metal filler from the small hole. Alternatively, a brittle solid alloy is formed by a solvent and a metal filler. The brittle solid alloy has the characteristic of being easy to crush. Therefore, the brittle solid alloy can also be discharged from the cavity through the small hole after crushing, so as to remove the metal filler in the cavity. By removing the metal filler in this way, the opening size of the via hole can be reduced, the difficulty of closing the via hole can be reduced, and the performance of the circuit board can be improved.

[0051] In some embodiments, optionally, the composition of the dissolving agent includes at least one of mercury or gallium, so that the dissolving agent has the ability to dissolve or destroy the metal filling, so as to facilitate the discharge of the metal filling from the small hole.

[0052] Since the reaction of mercury and gallium dissolving metal fillers to form alloys is not a chemical reaction, this alloy can be separated and processed by high-temperature evaporation or smelting, electrolysis, extraction, etc., so that the solvent is separated from the metal filler to recover metallic mercury and gallium, thereby realizing the recycling of the solvent.

[0053] In some embodiments, considering the difference in the solubility of metal mercury and gallium for different metals, it mainly depends on: (1) the crystal structure type of the single substance; (2) the closeness of the atomic radius; (3) the position of the two metals in the periodic table and the closeness of the chemical and physical properties. Since copper is a commonly used metal in circuit boards and copper is also the main material of graphic circuits, based on this, the choice of metal filler is not limited to metal aluminum, but can also be gold or silver, etc., to increase the dissolution rate of the dissolving agent on the metal filler in the circuit board, reduce the damage of the dissolving agent to the circuit board, and ensure the reliability of the circuit board.

[0054] The circuit board manufacturing method proposed in this application will be further described below in conjunction with embodiments and drawings.

[0055] For example, Figure 1 The flowcharts of some circuit board manufacturing method embodiments provided by the present application are shown. Figure 2 and Figure 3 Some circuit board embodiments produced by the circuit board production method provided in the present application are shown.

[0056] Reference Figure 1 , and combined with Figure 2 and Figure 3 The circuit board embodiment shown, the circuit board manufacturing method of some embodiments of the present application includes the following steps:

[0057] Step S110 , providing a daughter board 100 .

[0058] It can be understood that the circuit board in the related art is generally composed of a multi-layer sub-board 100, which includes a core board 101 (such as a copper-clad board) and a bonding sheet 102 (such as a semi-cured sheet). The core board 101 is used to make circuit patterns, and the bonding sheet 102 is used to bond two adjacent core boards 101.

[0059] Providing the daughter board 100 also includes the process of manufacturing the required circuit pattern on the core board 101, which will not be described in detail here.

[0060] Step S120 , forming a first groove on the daughter board 100 .

[0061] The first groove is used to form a cavity in the subsequent Figure 1 In the illustrated embodiment, the first groove is a through groove. In other embodiments, the first groove may also be a blind groove. The shape of the first groove may be flexibly designed according to actual needs and is not limited here.

[0062] Step S130 , filling the first trench with a metal filler 200 .

[0063] The metal filler 200 is used to play a supporting and space-occupying role. On the one hand, it prevents the sub-board 100 above the first groove from collapsing and deforming during pressing. On the other hand, it prevents the glue (resin produced by the softening of the adhesive sheet 102) from flowing into the first groove during the pressing process, resulting in the space of the cavity being occupied.

[0064] In the present application, the metal filler 200 can be a pure metal (such as any one of gold, silver, aluminum, potassium, sodium, zinc, etc.), or an alloy doped with other components to adjust the physical properties of the metal filler 200, as long as it does not affect the dissolution and removal of the metal filler 200 by a solvent.

[0065] In some embodiments, considering that the oxide layer on the metal surface may affect the efficiency of metal dissolution, the metal filler 200 is filled in the first groove in a low-oxygen environment to reduce the oxidation rate of the metal filler 200 and slow down the formation of the surface oxide layer of the metal filler 200, so as to improve the dissolution efficiency of the dissolving agent on the metal filler 200.

[0066] In some embodiments, in order to ensure the activity of the metal filler 200 and reduce the impact of oxidation on the metal filler 200, a step of removing the first oxide layer on the surface of the metal filler 200 is also included before pressing the sub-plate 100, thereby removing the oxide layer on the surface of the metal filler 200 and ensuring the reaction speed of the solvent and the metal filler 200.

[0067] Optionally, the first oxide layer can be removed by grinding the plate. For example, the first oxide layer can be removed by mechanically brushing or sandblasting the sub-plate 100 on the anti-oxidation line treated on the surface of the sub-plate 100. Alternatively, the first oxide layer can also be removed by adding acid, alkali or other chemical reagents to the surface of the metal filler 200 to corrode or micro-etch the surface of the metal filler 200 to remove the first oxide layer.

[0068] Step S140: Press the daughter board 100 to form a mother board.

[0069] Step S150 , manufacturing a metallized hole 400 , wherein the metallized hole 400 has a metal wall 500 for conducting the circuit patterns of each layer, and the metallized hole 400 penetrates the metal filler 200 .

[0070] Please combine Figures 3 to 5 In some embodiments, the above step S150 may specifically include the following steps S151-S152:

[0071] Step S151 : drilling a first hole in the motherboard to penetrate the metal filler 200 .

[0072] Step S152 : depositing copper on the first hole to form a metallized hole 400 .

[0073] As can be seen from the foregoing, the circuit board realizes the connection of circuit patterns of different layers through the metallized hole 400. The present application realizes the disconnection of the designated layer by setting the cavity. In order to ensure the reliability of the disconnection of the designated layer, the projection of the metallized hole 400 is set to be located within the projection of the metal filler 200. Therefore, after removing the metal filler 200, the metal wall 500 of the metallized hole 400 corresponding to the cavity position is completely exposed in the cavity, which is conducive to completely disconnecting the metal wall 500 of the metallized hole 400 at the designated layer, so as to ensure the reliability of the disconnection of the designated layer and avoid the failure of the disconnection of the designated layer.

[0074] Taking into account that the circuit board is formed by a multi-layer sub-board 100, the layers will be relatively offset during the stacking and lamination process, resulting in layer deviation. Therefore, the position of the metal filler 200 will also change compared to the preset position before lamination. Based on this, the size of the metal filler 200 is larger than the aperture of the metallized hole 400, and the size difference between the metal filler 200 and the metallized hole 400 is 2mil-5mil. Exemplarily, when the shape of the metal filler 200 is cylindrical, the outer diameter of the metal filler 200 is 2mil-5mil larger than the inner diameter of the metallized hole 400. For example, the outer diameter of the metal filler 200 is 2mil, 3mil, 4mil or 5mil larger than the inner diameter of the metallized hole 400. This can help reduce the impact of layer deviation on the relative position of the metallized hole 400 and the metal filler 200, so that even if the position of the metal filler 200 is offset, the metallized hole 400 can be drilled according to the preset position design of the metal filler 200 and can still connect to the metal filler 200, thereby ensuring that the solvent can flow through the metallized hole 400 to the surface of the metal filler 200.

[0075] There is no specific restriction on the size of the metal filler 200 and the metallized hole 400. The specific size can be referred to the standard range of the layer according to the actual situation, and combined with the dissolution effect of the solvent on the metal filler 200. When the size of the metal filler 200 is too large, the reaction time of the metal filler 200 is longer. When the size of the metal filler 200 is small, the relative position of the metallized hole 400 and the metal filler 200 is more affected by the layer deviation. Under the influence of the layer deviation, the metallized hole 400 is drilled according to the preset position of the metal filler 200, which may cause the projection of the metallized hole 400 to be staggered with the projection of the metal filler 200, that is, the projection of the metallized hole 400 cannot be completely covered by the metal filler 200, which may cause the specified layer to be disconnected and fail in the subsequent processing steps.

[0076] Step S160 , forming a via hole 300 on the motherboard to expose the metal filler 200 .

[0077] In order to prevent the solvent from reacting with the circuit pattern of the circuit board, the via hole 300 can be set in a non-functional area of ​​the circuit board to avoid damage to the circuit pattern when the solvent is passed through the via hole 300. It should be noted that the position of the via hole 300 is not required in the embodiment of the present application, and it only needs to be connected to the first groove.

[0078] In order to ensure the dissolution speed of the dissolving agent for the metal filler 200, the volume of the dissolving agent entering the first groove within a certain period of time is as large as possible. Based on this, the number of the through holes 300 can be multiple, and the multiple through holes 300 are arranged at intervals and connected to the first groove. In this way, the volume of the dissolving agent entering the first groove can be ensured, and the contact area between the dissolving agent and the metal filler 200 can be increased to ensure the reaction efficiency of the dissolving agent and the metal filler 200.

[0079] In some embodiments, the diameter of the via hole 300 is smaller than (or much smaller than) the size of the cavity, thereby reducing the size of the via hole 300 while ensuring that the metal filler 200 can be removed, so as to facilitate the subsequent plugging of the via hole 300 and reduce the impact of the via hole 300 on the cavity.

[0080] In some embodiments, the via hole 300 only needs to be connected to the first groove, so that the dissolving agent can flow into the first groove through the via hole 300 to dissolve or destroy the metal filler 200 .

[0081] In other embodiments, in order to ensure the dissolution efficiency of the metal filler 200 by the solvent, the projection of the via 300 may be located within the projection of the metal filler 200 to increase the connection area between the via 300 and the first groove and increase the speed of the solvent entering the first groove.

[0082] In some embodiments, in order to speed up the dissolution efficiency of the metal filler 200 by the solvent, a step of removing the second oxide layer on the surface of the metal filler 200 is further included before the solvent is introduced, thereby removing the oxide layer on the surface of the metal filler 200, ensuring the activity of the metal filler 200, reducing the impact of oxidation on the metal filler 200, and ensuring the dissolution efficiency of the metal filler 200 by the solvent. For some metal fillers 200 with lower oxidation efficiency, the step of removing the second oxide layer can also be omitted.

[0083] Optionally, the second oxide layer can be removed by adding acid, alkali or other chemical reagents to the surface of the metal filler 200 through the via hole 300 to corrode or micro-etch the surface of the metal filler 200 .

[0084] Step S170 , introducing a dissolving agent into the first groove through the via hole 300 to dissolve or destroy the metal filler 200 , wherein the dissolving agent includes metal.

[0085] Based on the principle of "amalgam reaction", when the dissolving agent contacts the metal filling 200, it can dissolve the metal filling 200 into a liquid alloy, or destroy the metal filling 200 to form an easily crushable alloy, so as to facilitate the removal of the metal filling 200 from the small hole. Based on this, the composition of the dissolving agent includes at least one of mercury or gallium, so that the dissolving agent has the ability to dissolve or destroy the metal filling 200.

[0086] In order to speed up the reaction efficiency between the solvent and the metal filler 200, the reaction conditions can also be adjusted according to the characteristics of the metal filler 200 or the solvent, such as applying a specific temperature or pressure, so as to achieve the effect of making the metal filler 200 or the solvent more active and the solvent flowing to the metal filler 200 faster, thereby improving the reaction efficiency of the solvent and the metal filler 200.

[0087] Exemplarily, the solvent is injected into the via 300 under pressure so that after entering the via 300, the solvent flows toward the metal filler 200 driven by pressure, which helps to control the flow direction of the solvent, speed up the speed at which the solvent reaches the surface of the metal filler 200, and reduce the volume of the solvent flowing to other layers, thereby improving the reaction efficiency of the solvent and the metal filler 200. Specifically, the solvent may be placed in the syringe of the syringe, and the needle is inserted into the conducting hole 300 and abutted against the surface of the metal filler 200, and the orifice is blocked by the syringe or other structure, and the syringe is pressurized to inject the solvent into the metal filler 200, so that the solvent is directly injected into the surface of the metal filler 200. At this time, the solvent surges and corrodes the metal filler 200, and only the metal filler 200 is dissolved or destroyed by the solvent. Due to the pressure, the solvent cannot enter other positions of the circuit board (such as the gap between the two layers of the sub-board 100), thereby achieving targeted dissolution of the metal filler 200, which is beneficial to avoid the situation where the solvent flows to other positions and causes damage to the circuit board or the circuit pattern. However, it should be noted that the layers corresponding to the inner wall of the first groove should be compacted to avoid internal stratification caused by excessive pressure when injecting the solvent.

[0088] It should be noted that the injection amount of the solvent can be calculated and controlled in advance according to the volume of the metal filling 200 and the composition of the solvent and the metal filling 200, so as to control the dissolution range of the solvent on the metal wall 500 corresponding to the cavity, and the solvent can be added in small amounts for multiple times. At the same time, based on the characteristics of amalgam being solid when containing less mercury and liquid when containing more mercury, the dissolution ratio of the solvent to the metal filling 200 will affect the morphology of the alloy. When the alloy is in a solid state, the fluidity is low, which can help control the erosion degree of the solvent, making the reaction control of the solvent more accurate.

[0089] Step S180 , removing the metal filler 200 to form a cavity on the motherboard.

[0090] Step S190: disconnect the metal wall 500 corresponding to the cavity.

[0091] It should be noted that the order of step S180 and step S190 needs to be adjusted according to the actual situation, and specifically needs to consider the alloy form formed by the reaction of the dissolving agent and the metal filler 200 and the disconnection method of the metal wall 500, etc. Specifically:

[0092] In most cases, when the content of mercury or gallium in the alloy formed by the reaction of the dissolving agent and the metal filler 200 is relatively high, the alloy is in liquid state, and the liquid alloy can be discharged through the via 300, or the liquid alloy can be discharged through the metallized hole 400 and / or the via 300 after the metal wall 500 of the metallized hole 400 corresponding to the cavity is disconnected, so as to form a cavity on the motherboard. When the metal filler 200 is composed of aluminum, the alloy formed by the reaction of the dissolving agent and the metal filler 200 is a solid brittle alloy, and the solid alloy can be discharged through the metallized hole 400 after being crushed, or the solid alloy can be discharged through the metallized hole 400 and / or the via 300 after the metal wall 500 of the metallized hole 400 corresponding to the cavity is disconnected.

[0093] In the solution where the dissolving agent reacts with the metal filler 200 to form a liquid alloy, the metal wall 500 may be broken by physical means or chemical etching.

[0094] When the metal wall 500 is physically disconnected, step S180 and step S190 may be performed first, that is, after the solvent dissolves the metal filler 200, the liquid alloy is removed first and then the metal wall 500 is disconnected, so as to reduce foreign matter or obstacles (referring to the liquid alloy) in the cavity, improve the efficiency of disconnecting the metal wall 500, and facilitate the judgment of the dissolution effect of the metal filler 200, so as to control the volume of the solvent passing into the conductive hole 300. Exemplarily, since the two sides of the metal wall 500 corresponding to the cavity lack support at this time, the resistance to pressure is weak, while the other metal walls 500 are supported by the sub-board 100 and have a strong resistance to pressure, the metal wall 500 can be destroyed by applying pressure to disconnect the metal wall 500 at the position of the metallized hole 400 corresponding to the cavity.

[0095] In one example, the metal wall 500 is disconnected by applying positive pressure or negative pressure to the cavity. Preferably, negative pressure is used, that is, the metal wall 500 is disconnected inward (i.e., away from the center of the metallized hole 400), so that the edge of the metal wall 500 is not easily pulled outward, resulting in the edge of the metal wall 500 that needs to be retained being separated from the supporting portion of the sub-board 100.

[0096] In another example, a tool such as a brush is rotated in the metallized hole 400 to apply a certain pressure to the metal wall 500. Since the metal wall 500 is relatively thin, the metal wall 500 lacking support will be destroyed, while the metal wall 500 tightly combined with the sub-board 100 can remain, thereby forming a good designated layer disconnection effect.

[0097] In this way, the presence or absence of the material to which the metal wall 500 is attached is utilized to utilize the pressure difference to break or destroy the metal wall 500. The solution is simple and easy to implement. In addition, this method is not prone to produce residual piles, thereby eliminating the subsequent step of controlling the depth of drilling to remove the residual piles, which is beneficial to improving the production efficiency of the circuit board.

[0098] The above is an implementation example in which the metal wall 500 is physically disconnected.

[0099] As can be seen from the above, the components of the dissolving agent include at least one of mercury or gallium, and mercury and gallium can dissolve metallic copper, while the component of the metal wall 500 of the metallized hole 400 is usually copper. Based on this, in order to protect the metal wall 500 from being damaged by the dissolving agent, after step S151 and before step S152, the method for manufacturing the circuit board also includes S153: when the metallized hole 400 has not been subjected to copper plating treatment, oxidizing the metal filler 200 through the first hole.

[0100] In this way, an intra-hole oxide layer 600 is formed on the hole wall where the metal filler 200 is penetrated, so as to protect the metal wall 500 of the metallized hole 400 when the dissolving agent is added later. Since the periphery of the metal wall 500 of the corresponding cavity of the metallized hole 400 is covered with a layer of intra-hole oxide layer 600, the intra-hole oxide layer 600 cannot react with the dissolving agent or the reaction efficiency is low. When the dissolving agent reacts with the metal filler 200, the intra-hole oxide layer 600 can isolate the dissolving agent from the metal wall 500 to achieve the effect of protecting the metal wall 500 and prevent the dissolving agent from corroding and damaging the metal wall 500. After the metal filler 200 is dissolved and removed, only the intra-hole oxide layer 600 and the metal wall 500 remain in the cavity. At this time, the intra-hole oxide layer 600 and the metal wall 500 at the corresponding cavity position lack support and can be directly removed by pressure destruction to form a cavity.

[0101] It should be noted that the method of forming the oxide layer 600 in the hole is only selected in the embodiment where the metal wall 500 is physically disconnected. When the metal wall 500 is disconnected by chemical etching, the above step S153 does not need to be performed when making the metallized hole 400.

[0102] When the metal wall 500 is cut off by chemical etching, step S190 may be performed first and then step S180 , that is, the liquid alloy is removed after the metal wall 500 is cut off.

[0103] In one example, the metal wall 500 is dissolved and disconnected by a dissolving agent. As mentioned above, the components of the dissolving agent include at least one of mercury or gallium. Mercury and gallium can dissolve metal copper, and the component of the metal wall 500 of the metallized hole 400 is usually copper. Based on this, the dissolving agent is also used to dissolve the metal wall 500. This can improve the production efficiency of the circuit board, reduce the types of components entering the inside of the circuit board, and avoid the reaction between the residual different components to affect the reliability of the circuit board.

[0104] In the related art, the metal wall 500 of the metallized hole 400 is selectively removed by etching or other copper reduction operations to achieve partial disconnection. Since the etching agent contacts the metal wall 500 through the metallized hole 400, the etching range of the etching agent is difficult to control, and the problem of over-etching is prone to occur. However, the present application uses a dissolving agent to gradually erode the metal wall 500 from the cavity. The position where the dissolving agent contacts the metal wall 500 is only the part corresponding to the cavity, and the other parts supported by the sub-board 100 cannot be contacted and eroded by the dissolving agent due to the limitation of the sub-board 100, so as to help control the erosion range of the dissolving agent on the metal wall 500, thereby helping to control the disconnection size of the metal wall 500, achieve disconnection of a specified layer, and improve the reliability of the circuit board.

[0105] In order to improve the accuracy of controlling the erosion range of the dissolving agent on the metal wall 500, the metallized hole 400 can also be filled before the dissolving agent is introduced. Therefore, when the dissolving agent dissolves to the position of the metal wall 500 that needs to be disconnected, the dissolving agent and the metal wall 500 have only a small copper ring contact area, so that the dissolving range of the metal wall 500 by the dissolving agent is limited, and due to the obstruction of the filling inside the metallized hole 400, when the metal copper ring here (i.e., the metal wall 500 corresponding to the cavity) is completely dissolved, the dissolving agent cannot erode upward or downward (i.e., along the center line direction of the metallized hole 400), so as to further accurately control the erosion range of the dissolving agent.

[0106] In addition, filling the metallized hole 400 before introducing the solvent can also protect the metal wall 500 in other circuit board solutions or other disconnection methods of the metal wall 500, slowing down the reaction speed of the solvent to the metal wall 500, so that the solvent can only dissolve the metal filler 200, and is removed in time after the metal filler 200 is dissolved, so as to reduce the impact of the solvent on the metal wall 500.

[0107] It should be noted that in the method of physically disconnecting the metal wall 500, based on process requirements, the metallized hole 400 can also be filled before the solvent is introduced, but the filler of the metallized hole 400 needs to be removed before pressure is applied to the metal wall 500 to avoid the filler from incorrectly supporting the metal wall 500 during the process of physically disconnecting the metal wall 500.

[0108] In order to ensure the blocking effect of the filler on the erosion of the solvent, the filler of the metallized hole 400 can be selected from non-metallic materials. For example, it can be a dense material such as ink, and this material is required to be free of bubbles and have a small particle pore size to meet the requirements of the tiny size of the metallized hole 400. In addition, this material can be solidified and can be removed without loss under certain conditions, such as being able to melt after high temperature, so as to achieve free filling and removal of the filler. Alternatively, the filler of the metallized hole 400 can also be a metal that cannot be dissolved by the solvent. For example, when the components of the solvent include mercury, the filler of the metallized hole 400 can be selected from iron, cobalt, nickel, manganese or radioactive metals, etc. When the components of the solvent include gallium, the filler of the metallized hole 400 can be selected from stainless steel, aluminum oxide, titanium oxide or some plastics (such as polytetrafluoroethylene, etc.).

[0109] It can be understood that, in another example, the metal wall 500 can also be removed by etching by introducing other chemical agents into the cavity through the via 300 .

[0110] In the solution where the solvent reacts with the metal filler 200 to form a solid alloy, the metal wall 500 can be broken by the solid alloy, or it can be broken by the physical method or chemical etching method as mentioned above, of course, the premise is to remove the solid alloy first.

[0111] When the metal wall 500 is broken by the solid alloy, step S190 may be performed first and then step S180 , that is, the solid alloy is removed after the metal wall 500 is broken.

[0112] In one example, the metal wall 500 is broken and disconnected by the pressure of the expansion of aluminum amalgam. When the components of the metal filler 200 include aluminum and the components of the solvent include mercury, the solvent reacts with the metal filler 200 to obtain a solid alloy (aluminum amalgam), which fills the via 300 at this time. The pressure after the expansion of the aluminum amalgam will push the unreacted metal filler 200 to squeeze the metal wall 500. Since the other side of the metal wall 500 lacks support, it is a good pressure release area, so that the metal filler 200 squeezes the metal wall 500 under the pressure of the expansion of the aluminum amalgam, so that the metal wall 500 is disconnected at the position of the corresponding cavity. By controlling the amount of mercury, the liquid metal mercury does not directly contact and dissolve with the metal wall 500 to ensure that the metal wall 500 is squeezed and disconnected.

[0113] In another example, the metal wall 500 is cut off by the physical method and chemical etching method as described above, and the implementation method thereof is substantially the same as the above implementation method, but the solid alloy needs to be removed first.

[0114] Since the solid alloy is brittle, it can be moved out of the cavity by ultrasonic vibration or pressurized powderization. For example, ultrasonic waves can be applied to the motherboard or the solid alloy to cause the solid alloy to vibrate and crush, and then move out of the cavity through the via hole 300 or the metallized hole 400; or, wind pressure can be applied to the solid alloy, such as blowing air to the solid alloy through the via hole 300, so that the solid alloy is crushed by the wind pressure, and then moved out of the cavity through the via hole 300 or the metallized hole 400.

[0115] It is understandable that in other embodiments, more solvents may be added to the solid alloy to increase the mercury or gallium content in the alloy, thereby changing the alloy from a solid state to a liquid state to facilitate alloy removal.

[0116] In some embodiments, when the process requires, after removing the metal filler 200 and disconnecting the metal wall 500 of the corresponding cavity, the circuit board manufacturing method further includes: filling the via hole 300 and / or the metallized hole 400 .

[0117] Finally, since the reaction of mercury and gallium dissolving the metal filler 200 to form an alloy is not a chemical reaction, in some embodiments, the alloy formed by the reaction of the dissolving agent and the metal filler 200 can also be separated and processed to recover the dissolving agent and realize the recycling of the dissolving agent.

[0118] The embodiments of the present application are described in detail above in conjunction with the accompanying drawings, but the present application is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for manufacturing a circuit board, characterized in that: include: Provide daughterboard; forming a first groove on the daughter board; filling the first groove with a metal filler; Pressing the daughter boards to form a mother board; Making a metallized hole, wherein the metallized hole has a metal wall for conducting the circuit patterns of each layer, and the metallized hole penetrates the metal filler; forming a via hole on the motherboard to expose the metal filler; Passing a dissolving agent into the first groove through the through hole to dissolve or destroy the metal filler, wherein the dissolving agent comprises a metal; removing the metal filler to form a cavity on the motherboard; The metal wall corresponding to the cavity is disconnected.

2. The method for manufacturing a circuit board according to claim 1, characterized in that: The dissolving agent is also used to dissolve the metal wall, or to apply pressure to the metal wall corresponding to the cavity to break the metal wall corresponding to the cavity.

3. The method for manufacturing a circuit board according to claim 2, characterized in that: When the dissolving agent is used to dissolve the metal wall, the metallized hole is filled before the dissolving agent is introduced; When the metal wall corresponding to the cavity is broken by pressure destruction, the filler of the metallized hole is removed before applying pressure to the metal wall.

4. The method for manufacturing a circuit board according to claim 3, characterized in that: The filler of the metallized hole is a non-metallic material.

5. The method for manufacturing a circuit board according to claim 1, characterized in that: When the metal filler includes aluminum and the solvent includes mercury, the solvent reacts with the metal filler to obtain a solid alloy to fill the via hole, so that the metal wall is disconnected under the extrusion of the solid alloy.

6. The method for manufacturing a circuit board according to claim 5, characterized in that: The solid alloy is powdered by ultrasonic vibration or pressure and then removed from the cavity.

7. The method for manufacturing a circuit board according to claim 1, characterized in that: The step of making the metallized hole comprises: Drilling a first hole in the motherboard to penetrate the metal filler; oxidizing the metal filler through the first hole; Copper is deposited in the first hole to form a metallized hole.

8. The method for manufacturing a circuit board according to any one of claims 1 to 7, characterized in that: The projection of the metallized hole is located within the projection of the metal filling.

9. The method for manufacturing a circuit board according to claim 7, characterized in that: The size of the metal filler is larger than the aperture of the metallized hole, and the difference between the size of the metal filler and the size of the metallized hole is 2mil-5mil.

10. A circuit board, characterized in that: The circuit board is prepared by the circuit board manufacturing method according to any one of claims 1 to 9.

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