Circuit board manufacturing method and circuit board

Abstract

The invention provides a circuit board manufacturing method and a circuit board. The circuit board manufacturing method comprises the following steps: providing a core board and a bonding sheet; a first groove is formed in the core plate or the bonding sheet and filled with first filler; laminating the core board and the bonding sheet to form a mother board; depth-controlled drilling is conducted on the mother board through a drilling tool to form a through hole, and the drilling tool stops working when moving to make contact with the first filler; and removing the first filler to form a cavity on the mother board. Therefore, the reliability of the circuit board can be improved while the drilling depth is ensured, the influence on the circuit pattern is reduced, and the design of the circuit pattern is facilitated. The invention relates to the field of circuit boards.

Description

Technical Field

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

[0002] In the process of making circuit boards, it is usually necessary to use depth-controlled drilling to drill blind holes on the circuit boards to the specified layer, that is, it is required to drill through a certain copper layer or drill to the surface of a certain copper layer without damaging the copper layer. Since the thickness of the circuit board is relatively small, the precision of depth-controlled drilling is extremely high, and the circuit board will produce glue flow during the high-temperature pressing process, causing the thickness of each layer of the core board of the circuit board to fluctuate relative to the original thickness. The thickness of the core board before pressing cannot be used as a parameter reference, resulting in a decrease in the accuracy of drilling holes on the circuit board. In related technologies, feedback signals are often triggered by the circuit graphics on the core board to control the drilling depth, but this method requires a special area to be reserved on the internal circuit graphics, which has a certain impact on the signal design of the circuit graphics. 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 improve the reliability of the circuit board while ensuring the drilling depth.

[0004] The circuit board manufacturing method provided in this application includes:

[0005] Provide core board and bonding sheet;

[0006] Arranging a first groove on the core plate or the bonding sheet and filling it with a first filler;

[0007] Laminating the core board and the bonding sheet to form a mother board;

[0008] Using a drill to control the depth of the motherboard to form a via hole, the drill stops working when it moves to contact the first filler;

[0009] The first filler is removed to form a cavity on the mother board.

[0010] According to the circuit board manufacturing method provided by the present application, at least the following technical effects are achieved: by setting a first groove on the core board or the bonding sheet and filling it with a first filler, it can provide support and space-occupying functions during pressing, and can also protect the copper layer at the bottom of the drill hole through the first filler, so as to reduce the influence of the drilling depth error on the circuit board, and at the same time, by filling the first filler in the first groove, by setting the drill to stop working when it contacts the first filler, the cavity of the first groove after the first filler is removed and the hole obtained by the drill on the motherboard by controlling the depth of the drill hole together form a via hole, so that the depth of the first groove is used to reserve sufficient allowable error for the depth of the controlled depth drilling, which can reduce the precision requirements for the drilling depth, so as to ensure the target depth of the via hole, thereby improving the reliability of the circuit board while ensuring the drilling depth. In addition, by using the circuit board manufacturing method provided by the present application, there is no need to reserve a special feedback loop area on the internal circuit pattern, so as to effectively reduce the influence on the circuit pattern and facilitate the design of the circuit pattern.

[0011] According to some embodiments of the present application, a signal hole is set on the motherboard and filled with a second filler, and the second filler is conductively connected to the first filler, so that when the drill contacts the first filler, the drill is connected to the second filler to form a feedback loop to control the drill to stop working.

[0012] According to some embodiments of the present application, the method further includes: removing the second filler.

[0013] According to some embodiments of the present application, a depth of the signal hole is greater than or equal to a distance from a cutting surface of the motherboard to a side of the first filler close to the cutting surface.

[0014] According to some embodiments of the present application, the first groove is disposed at the bottom of the core board or the bottom of the bonding sheet, and the opening of the first groove faces a direction away from the feed surface of the mother board.

[0015] According to some embodiments of the present application, the height of the first filler is greater than or equal to a safe distance at which the drill stops working.

[0016] According to some embodiments of the present application, removing the first filler to form a cavity on the motherboard includes:

[0017] A knockout hole communicating with the first groove is provided on the motherboard, or the through hole is used as the knockout hole;

[0018] The first filler is removed through the knockout hole.

[0019] According to some embodiments of the present application, before removing the first filler through the removal hole, the method further includes:

[0020] The first filler is removed by heating the first filler to melt it or cooling it to powder it.

[0021] According to some embodiments of the present application, the first filler includes tin, and the first filler is removed by any of the following methods: applying a low temperature to the area where the first filler is located, so that the first filler is converted into powder and discharged from the removal hole; or applying a high temperature to the area where the first filler is located, so that the first filler is melted and discharged from the removal hole.

[0022] The circuit board provided in the present application is manufactured by the circuit board manufacturing method provided in the present application.

[0023] The circuit board provided in the present application is manufactured by the circuit board manufacturing method provided in the present application, so the circuit board correspondingly has the beneficial effects provided by the circuit board manufacturing method, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide further understanding of the technical solution disclosed in the present application and constitute a part of the specification. Together with the embodiments disclosed in the present application, they are used to explain the technical solution disclosed in the present application and do not constitute a limitation on the technical solution disclosed in the present application.

[0025] Figure 1 It is a flow chart of a method for manufacturing a circuit board according to an embodiment of the present application;

[0026] Figure 2 This is a schematic diagram of the structure of a circuit board manufactured by a circuit board manufacturing method according to an embodiment of the present application;

[0027] Figure 3 This is a schematic diagram of the structure of a circuit board manufactured by a circuit board manufacturing method according to an embodiment of the present application during depth-controlled drilling;

[0028] Figure 4 It is a flow chart of another method for manufacturing a circuit board according to an embodiment of the present application;

[0029] Figure 5 This is a schematic diagram of the structure of a circuit board manufactured by another circuit board manufacturing method based on an embodiment of the present application.

[0030] Core plate 10, feed surface 101;

[0031] Adhesive sheet 20, first groove 21;

[0032] A first filler 30;

[0033] Signal hole 40;

[0034] The second filler 50 . DETAILED DESCRIPTION

[0035] 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.

[0036] In the description of the present application, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, 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 specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0037] In the description of this application, "several" means one or more, "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.

[0038] In the description of this application, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this application based on the specific content of the technical solution.

[0039] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" 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.

[0040] In order to meet the design of blind holes, back-drilled holes or large and small holes, the circuit board usually needs to use the method of controlled depth drilling to drill blind holes on the circuit board until they penetrate the specified layer or reach the surface of the specified layer. Since the thickness of the core board after lamination fluctuates relative to the original thickness, the thickness of the core board before lamination cannot be used as a parameter reference, resulting in the accuracy of the drilling depth being affected. It may happen that other layers of the circuit board are damaged due to excessive drilling depth, or the target position is not reached due to too small drilling depth, affecting the manufacturing quality of the circuit board. In order to solve this problem, some related technologies make a trigger feedback circuit by reserving part of the area of ​​the circuit pattern on the core board, and trigger the feedback signal when the drill reaches a certain depth to control the drilling depth. However, the trigger feedback circuit using this method usually needs to occupy a certain area on the core board, resulting in a reduction in the area of ​​the core board that can be used to make the circuit pattern, affecting the circuit pattern design on the circuit board. At the same time, due to the limitation of the location of the trigger feedback circuit, the signal design of the circuit pattern will also be affected.

[0041] To this end, the present application provides a circuit board manufacturing method, which can improve the reliability of the circuit board while ensuring the drilling depth, and reduce the impact on the circuit pattern, which is convenient for the design of the circuit pattern. In addition, the present application also provides a circuit board manufactured using the circuit board manufacturing method.

[0042] 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.

[0043] 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:

[0044] S110 , providing a core board 10 and a bonding sheet 20 .

[0045] It is understood that the circuit board in the present application is a multi-layer board, which is formed by alternately stacking and laminating a core board 10 and a bonding sheet 20, and the circuit board has at least three layers (i.e., two layers of core boards 10 sandwiching a layer of bonding sheet 20). Among them, the core board 10 is a single-sided or double-sided copper-clad board, and a circuit pattern is made on the core board 10.

[0046] S120 , setting a first groove 21 on the core board 10 or the bonding sheet 20 and filling the first filler 30 .

[0047] Therefore, the first filler 30 can be used to provide support and space-occupying function during pressing, and the copper layer at the bottom of the drill hole can be protected by the first filler 30 to reduce the influence of the drilling depth error on the circuit board. At the same time, the first groove 21 and the hole obtained by the depth-controlled drilling on the motherboard by the drill bit form a via hole together. The depth of the first groove 21 is used to reserve sufficient allowable error for the depth of the depth-controlled drilling, which can reduce the accuracy requirement for the drilling depth, so as to ensure the target depth of the via hole, thereby improving the reliability of the circuit board while ensuring the drilling depth.

[0048] Optionally, in some embodiments, the first groove 21 is disposed at the bottom of the core board 10 or the bottom of the bonding sheet 20, and the opening of the first groove 21 faces a direction away from the feed surface 101 of the motherboard. The motherboard refers to a structure formed by pressing the core board 10 and the bonding sheet 20 in the subsequent step S130, and the feed surface 101 refers to the feed surface of the drill on the motherboard when the motherboard is controlled to drill in depth in the subsequent step S150.

[0049] In this way, the opening of the first groove 21 is located on the side of the core board 10 or the bonding sheet 20 away from the cutting surface 101 of the motherboard, which can facilitate the conductive hole obtained by controlled depth drilling to pass through the layer where the first groove 21 is located (that is, the core board 10 or the bonding sheet 20), so that the first groove 21 after removing the first filler 30 and the hole obtained by controlled depth drilling of the drill on the motherboard together form a conductive hole, so that the conductive hole passes through the specified layer or reaches the surface of the specified layer, so as to improve the reliability of the circuit board.

[0050] For example, in Figure 2 In the illustrated embodiment, the first groove 21 is disposed at the bottom of the core plate 10. This allows for drilling a via hole that penetrates a designated layer. In other embodiments, the first groove 21 is disposed at the bottom of the bonding sheet 20. This allows for drilling a via hole that reaches the surface of a designated layer.

[0051] It can be understood that in other embodiments, the first groove 21 can also be arranged in the middle or top of the core board 10 or the bonding sheet 20, and the opening of the first groove 21 extends in the horizontal direction, or the opening of the first groove 21 is facing the direction of the feed surface 101 close to the motherboard.

[0052] Optionally, the height of the first filler 30 is the same or substantially the same as the depth of the first groove 21, and the depth of the first groove 21 is less than or equal to the thickness of the core board 10, or the depth of the first groove 21 is less than or equal to the thickness of the bonding sheet 20. That is, the first groove 21 can be a groove provided on the core board 10 or the bonding sheet 20, or a hole penetrating the core board 10 or the bonding sheet 20, and the first filler 30 fills the first groove 21. For example, Figure 2In the illustrated embodiment, the height of the first filler 30 is the same as the depth of the first groove 21. The first groove 21 is disposed on the bonding sheet 20 and the depth of the first groove 21 is less than the thickness of the bonding sheet 20, so that the first filler 30 can have a large enough height to reserve a sufficient allowable error for the drilling depth of the via hole, thereby reducing the precision requirement for the drilling error. This can not only facilitate the manufacturing and forming of the circuit board, but also protect the circuit board while ensuring the depth of the via hole, thereby preventing the copper layer at the bottom of the via hole from being damaged by the drill, and improving the reliability of the circuit board.

[0053] In addition, by limiting the height of the first filler 30 to be the same or approximately the same as the depth of the first groove 21, the first filler 30 can also fill the first groove 21, which can not only facilitate support during the pressing process to prevent the core board 10 or the bonding sheet 20 from collapsing and deforming at the first groove 21 to ensure the size of the first groove 21, but also occupy the first groove 21 during the pressing process to prevent the glue (resin produced by the softening of the bonding sheet 20) from flowing into the first groove 21 during the pressing process, resulting in the space of the cavity being occupied.

[0054] It can be understood that in other embodiments, the height of the first filler 30 may also be smaller than or greater than the depth of the first groove 21 .

[0055] S130 , pressing the core board 10 and the bonding sheet 20 together to form a mother board.

[0056] At this time, the first groove 21 is supported by the first filler 30 to ensure that the core board 10 or the bonding sheet 20 at the first groove 21 will not sink or deform during the pressing process, which is beneficial to improve the reliability of the circuit board.

[0057] S140, setting a signal hole 40 on the motherboard and filling it with a second filler 50, the second filler 50 is connected to the first filler 30, so that when the drill contacts the first filler 30, the drill is connected to the second filler 50 to form a feedback loop to control the drill to stop working.

[0058] In this way, the second filler 50 is connected to the drill through the first filler 30, which is conducive to the feedback loop being turned on when the drill reaches the position where the first filler 30 is located, triggering the generation of an electrical signal, indicating that the drill has reached the target position, so as to control the drill to stop working, thereby facilitating the control of the drilling depth of the drill and improving the accuracy of the drilling depth. At the same time, the second filler 50 and the first filler 30 form a feedback loop with the drill during depth-controlled drilling, which can simplify the design of the feedback loop, so as to help reduce the space occupied by the trigger feedback design on the circuit pattern of the motherboard, thereby reducing the impact on the circuit pattern and facilitating the design of the circuit pattern. Optionally, due to the thickness of the first filler 30 as a guarantee, the drilling accuracy requirement of the signal hole 40 is not high. Based on this, the depth of the signal hole 40 is greater than or equal to the distance from the feed surface 101 of the motherboard to the side of the first filler 30 close to the feed surface 101. Exemplarily, the drilling depth of the signal hole 40 can be set to be slightly larger than the theoretical distance from the cutting surface 101 of the motherboard to the upper surface of the first filler 30 (i.e., the side of the first filler 30 close to the cutting surface 101), so as to ensure that the signal hole 40 extends to the first filler 30. In this way, the thickness of the first filler 30 can be used to make the drilling depth of the signal hole 40 more flexible, reduce the precision requirement for the signal hole 40, and facilitate the manufacture of the signal hole 40.

[0059] Optionally, in order to meet the design requirement of electrical connection between the first filler 30 and the second filler 50 , the material of the second filler 50 may be any conductive material such as metal, graphite or semiconductor.

[0060] For example, the second filler 50 may be metal tin, and the conduction effect is achieved by pouring the molten metal tin into the signal hole 40. Alternatively, the second filler 50 may also be a conductive metal strip, and the conduction effect is achieved by inserting the conductive metal strip into the signal hole 40.

[0061] S150 , using a drill to control the depth of drilling holes in the motherboard to form via holes, and the drill stops working when it moves to contact the first filler 30 .

[0062] refer to Figure 3 As shown, when the drill contacts the first filler 30, the drill, the first filler 30 and the second filler 50 are turned on to turn on the feedback loop, generating an electrical signal, indicating that the drill has reached the target position, so as to control the drill to stop working, thereby facilitating the control of the drilling depth of the drill and improving the accuracy of the drilling depth. At the same time, the second filler 50 and the first filler 30 form a feedback loop with the drill during depth-controlled drilling, which can simplify the design of the feedback loop, thereby facilitating the reduction of the space occupied by the trigger feedback design on the circuit pattern of the motherboard, thereby reducing the impact on the circuit pattern and facilitating the design of the circuit pattern.

[0063] It can be understood that the method of generating feedback electrical signals in depth-controlled drilling is not limited to the method exemplified in this embodiment. In other feedback methods, the circuit board manufacturing method of the present application can play a role, which helps to more flexibly set the conductor for feedback (that is, the first filler 30) inside the circuit board, and is suitable for removal from the circuit board after the depth-controlled drilling is completed.

[0064] Optionally, the preset depth of the via hole is the distance from the cutting surface 101 of the motherboard to the side of the first filler 30 away from the cutting surface 101. That is to say, the actual required depth of the via hole is the drilling distance of the drill on the motherboard plus the thickness of the first filler 30 (i.e., the distance from the cutting surface 101 to the side of the first filler 30 away from the cutting surface 101 (i.e., the lower surface of the first filler 30)). By prefabricating the first groove 21 and the first filler 30 in advance, the precision error during depth-controlled drilling can be offset. Since the first filler 30 has a certain thickness, even if there is a partial error in the drilling depth of the depth-controlled drilling, it will not affect the depth of the via hole. In addition, the presence of the first filler 30 can protect the copper layer at the bottom of the drill hole, so as to effectively avoid the situation where the copper layer is damaged due to excessive drilling depth, thereby improving the reliability of the circuit board.

[0065] Specifically, in the motherboard, the first filler 30 is located above the copper layer, and the lower surface of the first filler 30 is the target depth for depth control. However, due to the existence of the first filler 30, the drill does not need to drill directly to the lower surface of the first filler 30, and can stop as long as it drills to the upper surface of the first filler 30, and then the first filler 30 is removed to achieve the effect of depth control to the target copper layer. In this way, the direct contact between the drill and the target copper layer is avoided, and the drill damages the copper layer during the drilling process.

[0066] Exemplarily, when drilling a via hole, the drilling depth of the drill is set to be equal to or slightly greater than the distance from the feed surface 101 to the upper surface of the first filler 30. Since the first groove 21 where the first filler 30 is located is part of the via hole, and the first filler 30 needs to be removed in a subsequent step, even if the drilling depth of the drill is greater than the distance from the feed surface 101 to the upper surface of the first filler 30, that is, the drill drills to the first filler 30, the via hole and the circuit board itself will not be affected, thereby improving the tolerance of drilling depth errors and reducing the accuracy requirements for drilling depth, which is beneficial to the manufacture of via holes and ensures the reliability of the circuit board.

[0067] Optionally, considering that the drill still has a travel distance from the time when the drill contacts the first filler 30 to trigger the feedback loop to the time when the drill stops working, and when there is a delay in the process of the electric signal controlling the drill to stop working, the travel distance of the drill is greater, based on this, the safe distance for the drill to stop working is defined as the travel distance of the drill from the time when the drill contacts the first filler to the time when the drill stops working, and the height of the first filler 30 is greater than or equal to the safe distance for the drill to stop working when the feedback loop is triggered. Thus, it can be ensured that when the drill stops working under the control of the feedback loop, there is a gap between the drill and the bottom of the first filler 30. In this way, on the one hand, it is helpful to ensure that the travel distance of the drill is less than the depth of the via hole, so as to avoid the copper layer at the bottom of the via hole being damaged by the drill, so as to improve the reliability of the circuit board. On the other hand, the thickness of the first filler 30 can also be used to reserve a sufficient buffer distance for the drill to offset the safe distance for the drill to stop working, thereby ensuring the reliability of the circuit board.

[0068] Optionally, the safety distance at which the drill stops working is 0.5 mm-2 mm, for example, 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm or 2 mm, etc. This helps to make the safety distance at which the drill stops working small enough to ensure the reliability of the circuit board.

[0069] It is understandable that controlled depth drilling also includes post-processing steps such as cleaning burrs. The specific post-processing steps can refer to the relevant prior art and will not be repeated here.

[0070] S160 , removing the first filler 30 to form a cavity on the motherboard.

[0071] Thus, the first groove 21 and the hole obtained by depth-controlled drilling form a via hole together, and the depth of the first groove 21 is used to reserve sufficient allowable error for the depth of the depth-controlled drilling, so that the drill does not need to drill directly to the lower surface of the first filler 30 when the depth is controlled on the motherboard, and it can stop as long as it drills to the upper surface of the first filler 30, and then the first filler 30 is removed to achieve the effect of controlling the depth to the target copper layer, so as to avoid direct contact between the drill and the target copper layer, and the drill damages the copper layer during the drilling process, and at the same time, it can reduce the precision requirements for the drilling depth, which is conducive to ensuring the target depth of the via hole, so as to ensure the drilling depth. Optionally, the above step S160 includes the following steps S161-S163:

[0072] S161, a knockout hole connected to the first groove 21 is provided on the motherboard, or the signal hole 40 or the conducting hole is used as the knockout hole.

[0073] Thus, in one example, by additionally setting a knockout hole on the motherboard, the size of the knockout hole can be reduced, and the material residue on the signal hole 40 or the via hole when removing the first filler 30 can be reduced. In another example, using the signal hole 40 or the via hole as a knockout hole can improve the structural reuse rate, reduce the number of holes on the circuit board, and simplify the manufacturing process.

[0074] It should be noted that when the signal hole 40 is used as a rejection hole to remove the first filler 30 , the second filler 50 should be removed first.

[0075] S162 , removing the first filler 30 by heating the first filler 30 to melt it or cooling it to powder it.

[0076] Since melting and powdering are physical changes, no acidic or alkaline solution is needed, thus avoiding damage to the circuit pattern of the circuit board. Since melting or powdering is triggered by the temperature change of the first filler 30, it is more suitable for removing the first filler 30 in a complex cavity, and will not be affected by the difficulty of solution exchange, thereby improving the efficiency and reliability of removing the first filler 30.

[0077] Specifically, the first filler 30 is removed by any of the following methods: applying a low temperature to the area where the first filler 30 is located, so that the first filler 30 is converted into powder and discharged from the removal hole; or applying a high temperature to the area where the first filler 30 is located, so that the first filler 30 is melted and discharged from the removal hole.

[0078] In this way, the first filler 30 is conveniently removed from the circuit board with low damage by melting or powdering, which can meet the special requirements of removing the first filler 30 from smaller openings (such as knockout holes) in the circuit board manufacturing process, thereby improving the yield and flexibility of the circuit board manufacturing method and meeting the requirements of different circuit board manufacturing. In addition, by applying low temperature or high temperature to the area where the first filler 30 is located to achieve removal, it is possible to ensure the removal of the first filler 30 while reducing the impact of the heating and cooling process on the surface structure or components of the circuit board.

[0079] Specifically, considering that high temperature is also generated during the pressing process, in order to prevent the first filler 30 from melting during pressing and causing the glue to flow into the cavity, the melting point of the first filler 30 should be greater than or equal to 180°C.

[0080] In the embodiment of removing the first filler 30 by high temperature melting, in order to reduce the damage to the circuit board during the melting process, the melting point of the first filler 30 should be lower than the maximum temperature that the circuit board can withstand. Exemplarily, the melting point of the first filler 30 can be selected between 210°C and 270°C.

[0081] In the embodiment of removing the first filler 30 by low temperature pulverization, in order to avoid pulverization at room temperature, the pulverization temperature of the first filler 30 should be lower than room temperature. Exemplarily, the first filler 30 can be pulverized at a temperature lower than 13.2°C.

[0082] It should be noted that in the method of high-temperature melting removal or low-temperature powdering removal of the first filler 30 mentioned in the embodiments of the present application, high temperature refers to a temperature greater than or equal to the melting point of the first filler 30, and low temperature refers to a temperature less than or equal to the powdering temperature of the first filler 30.

[0083] In some embodiments, the first filler 30 includes tin (tin element or tin alloy), thereby satisfying the above requirements for the first filler 30 .

[0084] It is understandable that metallic tin has three allotropes: gray tin, white tin and brittle tin. Its Mohs hardness is only 3.75, making it one of the softest metals with good ductility but poor ductility. Within the temperature range of 13.2℃-161℃, the properties of tin are relatively stable, with a tetragonal lattice, called "white tin".

[0085] When the ambient temperature is lower than 13.2℃, the atoms in the tin crystal will rearrange and gradually change from a tetragonal lattice to a cubic lattice. This change changes the tin into a gray powder, which is "gray tin". At a temperature of -30℃, the crystal transformation speed reaches its maximum, and the tin block quickly turns into powder. The transformation from white tin to gray tin is called tin plague.

[0086] When the temperature is above 161℃, white tin turns into orthorhombic tin with orthorhombic crystal structure. Orthorhombic tin is very brittle, it will break when knocked, its brittleness increases, and its ductility is poor, so it is called "brittle tin".

[0087] When the temperature is above 232°C, tin melts.

[0088] First, using tin as the first filler 30 can meet the requirements of pressing.

[0089] At the beginning of pressing, the pressure will be increased first. When it reaches the highest pressure, the temperature is about 110℃. At this time, the tin is in a stable white tin state, providing reliable support.

[0090] Thereafter, the temperature is continuously raised on the basis of constant pressure, and the fluidity of the bonding sheet 20 is further enhanced. When the temperature reaches about 140°C, the viscosity of the bonding sheet 20 is the lowest and the fluidity is the strongest. During this process, the tin can continue to remain in the state of white tin, and the hardness of the tin can withstand the squeezing force of the flowing glue, thereby effectively blocking the flowing glue and preventing the area that will serve as the cavity from being occupied by the flowing glue.

[0091] After that, the temperature continues to rise, the viscosity of the bonding sheet 20 gradually increases, the fluidity deteriorates and solidifies, and when it reaches 160°C, the tin begins to become unstable and turns into brittle tin, but at this time the glue flow has basically entered a solidified state, and will not cause a large squeeze or other impact on the area where the tin is located (that is, the area serving as the cavity), ensuring that the area is not occupied. At the same time, since the circuit board is in a stable placement state during the hot pressing process, the first filler 30 is not impacted, so the glue flow will not be squeezed in turn due to the crushing of the brittle tin.

[0092] Continue to raise the temperature to about 200℃, the metal tin begins to soften gradually. At this time, the flow glue has solidified and will not affect the area where the tin is located.

[0093] In summary, based on the physical properties of tin, the entire pressing process will not affect the space occupied by tin, and tin as the first filler 30 can meet the requirement of endurance during the pressing process.

[0094] Secondly, tin can be removed by high-temperature melting. Taking tin as an example, heating to slightly above 232°C can turn tin into liquid. At this time, it is only necessary to process a removal hole connected to the first groove 21, so that the liquid tin can be easily discharged from the removal hole. The position of the removal hole is not affected by the shape of the first filler 30, and the size of the removal hole is not affected by the size of the first filler 30. Since 232°C is only slightly higher than the temperature during pressing (for example, 200°C), it is not easy to cause damage to the structure on the circuit board. Since liquid tin is fluid, the complexity of the shape of the cavity (for example, a mesh cavity) will not affect the discharge of the first filler 30.

[0095] Finally, tin can also be removed by low-temperature powderization. Taking tin as an example, cooling to below 13.2°C can cause tin to undergo tin pulverization and transform into a powder state. Cooling to below -30°C can accelerate this process. At this time, only a rejection hole connected to the first groove 21 needs to be processed to conveniently discharge the powdered tin from the rejection hole. The position of the rejection hole is not affected by the shape of the first filler 30, and the size of the rejection hole is not affected by the size of the first filler 30.

[0096] It is understandable that for some temperature-sensitive circuit boards, such as those with embedded precision components, the melting temperature may exceed the tolerance of the circuit board. However, 13.2°C will hardly have a negative impact on the circuit board. The low-temperature powder removal method can better avoid the problem of damaging the circuit board and more reliably remove the first filler 30.

[0097] It should be pointed out that in the embodiments of the present application, tin is the main component of the first filler 30, but the first filler 30 is not required to be a single tin substance. It is allowed to add some other components to the first filler 30 (that is, a tin alloy that meets the requirements as the first filler 30) to adjust the physical properties of the first filler 30, as long as it does not hinder the removal of the first filler 30 by heating or cooling.

[0098] Optionally, the melting point of the first filler 30 or the temperature at which tin poisoning occurs may be adjusted by adding other components according to the needs of the process.

[0099] For example, if there are other low-temperature links in the process, in order to prevent the first filler 30 from being powdered in advance, the occurrence temperature of tin pest may be reduced by adding aluminum or zinc.

[0100] Alternatively, ferromagnetic metal powder may be added to the first filler 30 so that the first filler 30 can be selectively heated locally and directionally by high-frequency electromagnetic heating, thereby reducing the heat received by other areas of the circuit board during the melting process and reducing the impact on other areas.

[0101] For example, some iron powder can be sprinkled on the surface of the tin block to form the desired first filler 30; or some iron powder can be sandwiched between two tin blocks to form the desired first filler 30; or, tin can be melted in a mold, iron powder can be added and stirred evenly, and the desired first filler 30 can be formed after solidification.

[0102] It can be understood that the above-mentioned embodiment introduces the circuit board manufacturing method of the present application by taking the tin-based first filler 30 as an example, but the first filler 30 applicable to the circuit board manufacturing method is not limited to the tin-based first filler 30. As long as the first filler 30 can satisfy the melting point greater than or equal to 180°C, and the first filler 30 has any of the following characteristics: the melting point of the first filler 30 is between 210°C and 270°C; the first filler 30 can be powdered at a temperature below 13.2°C, the basic requirements of the circuit board manufacturing method can be met.

[0103] However, the first filler 30 based on tin (tin element or tin alloy) is preferred among the first fillers 30 because of its powderization property and suitable melting point and hardness.

[0104] S163, removing the first filler 30 through the removal hole.

[0105] In some embodiments, the method for manufacturing a circuit board further includes the following steps:

[0106] S170 , removing the second filler 50 .

[0107] This can prevent the second filler 50 from interfering with the signal of the circuit board, thereby ensuring the reliability of the circuit board.

[0108] It can be understood that in some other embodiments, the second filler 50 may also remain in the signal hole 40 .

[0109] Optionally, in some embodiments, when the bonding force between the second filler 50 and the hole wall of the signal hole 40 is small, the second filler 50 can be removed by external force, thereby simplifying and facilitating the removal of the second filler 50, which is beneficial to the production of the circuit board.

[0110] It is understandable that in other embodiments, the second filler 50 may also be removed in the same manner as the first filler 30 , that is, the second filler 50 is removed by melting at a higher temperature or powdering at a lower temperature.

[0111] Optionally, there is no order difference between the above-mentioned step S170 and the above-mentioned step S160, that is, in the process of manufacturing the circuit board, the first filler 30 can be removed first and then the second filler 50, or the second filler 50 can be removed first and then the first filler 30. The specific process can be adjusted according to actual needs and is not limited here.

[0112] For example, Figure 4 A flow chart of a method for making a pattern inside a PCB slot hole provided in some other embodiments of the present application is shown.

[0113] Reference Figure 4 , and combined with Figure 5 The circuit board embodiment shown, the circuit board manufacturing method of some embodiments of the present application includes the following steps:

[0114] S210 , providing a core board 10 and a bonding sheet 20 .

[0115] S220 , setting a first groove 21 on the core board 10 or the bonding sheet 20 and filling the first filler 30 .

[0116] S230 , pressing the core board 10 and the bonding sheet 20 together to form a mother board.

[0117] The contents and beneficial effects of steps S210 to S230 are the same as those of steps S110 to S130 and are not described in detail here.

[0118] S240 , using a drill to control the depth of drilling holes in the motherboard to form via holes, and the drill stops working when it moves to contact the first filler 30 .

[0119] Optionally, in some embodiments, the method of controlling the drill to stop working when it contacts the first filler 30 can be achieved by controlling the preset drilling depth of the drill. Since the original depth of the bottom of the via hole is replaced by the first filler 30, and the first filler 30 has a sufficiently large height, the preset drilling depth of the drill does not need to be so precise, as long as the drill is controlled to be located between the upper and lower surfaces of the first filler 30 after stopping working, so as to ensure that the first filler 30 is directly connected to the outside world, so as to facilitate the removal of the first filler 30, so that the first groove 21 after removing the first filler 30 and the hole obtained by the drill on the motherboard through controlled depth drilling together form a via hole, so as to facilitate ensuring the drilling depth. On the other hand, the height of the first filler 30 is used to provide an allowable error for the drilling depth of the drill, so as to protect the copper layer at the bottom of the via hole and avoid damage to the copper layer at the bottom of the via hole, thereby ensuring the reliability of the circuit board. In addition, the use of this method does not require the provision of signal holes and second fillers, which can simplify the manufacturing process and save manufacturing costs.

[0120] In other embodiments, the method of controlling the drill to stop working when it contacts the first filler 30 can also be to use the debris discharged from the drilling as feedback judgment. Since the first filler 30 is made of different materials from the core board 10 and the bonding sheet 20, when the debris discharged from the drilling changes, it can be judged that the first filler 30 is drilled, and the drill can be controlled to stop working. This method can not only ensure the safety of the copper layer at the bottom of the via hole and achieve lossless feedback, but also save the setting of the signal hole and the second filler, so as to simplify the production process and save manufacturing costs.

[0121] It is understandable that in other embodiments, the method of controlling the drill to stop working when it contacts the first filler 30 may be other methods, which can be set according to actual needs and are not limited here.

[0122] S250 , removing the first filler 30 to form a cavity on the motherboard.

[0123] The content and beneficial effects of step S250 are the same as those of step S160 and are not described again here.

[0124] In some optional embodiments, the function / operation mentioned in the flow chart may not occur in the order mentioned in the operation diagram. For example, depending on the function / operation involved, the two boxes shown in succession can actually be executed substantially simultaneously or the boxes can sometimes be executed in reverse order. In addition, the embodiment presented and described in the flow chart of the application is provided by way of example, for the purpose of providing a more comprehensive understanding of technology. The disclosed method is not limited to the operation and logic flow presented herein. Optional embodiments are expected, wherein the order of various operations is changed and the sub-operation of a part for which is described as a larger operation is performed independently.

[0125] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for manufacturing a circuit board, characterized in that: include: Provide core board and bonding sheet; Arranging a first groove on the core plate or the bonding sheet and filling it with a first filler; Laminating the core board and the bonding sheet to form a mother board; Using a drill to control the depth of the motherboard to form a via hole, the drill stops working when it moves to contact the first filler; The first filler is removed to form a cavity on the mother board.

2. The method for manufacturing a circuit board according to claim 1, characterized in that: The method further comprises: A signal hole is set on the motherboard and filled with a second filler, and the second filler is connected to the first filler, so that when the drill contacts the first filler, the drill is connected to the second filler to form a feedback loop to control the drill to stop working.

3. The method for manufacturing a circuit board according to claim 2, characterized in that: The method further includes removing the second filler.

4. The method for manufacturing a circuit board according to claim 2, characterized in that: The depth of the signal hole is greater than or equal to the distance from the cutting surface of the motherboard to a side of the first filler close to the cutting surface.

5. The method for manufacturing a circuit board according to claim 1, characterized in that: The first groove is arranged at the bottom of the core board or the bottom of the bonding sheet, and the opening of the first groove faces a direction away from the cutting surface of the mother board.

6. The method for manufacturing a circuit board according to claim 5, characterized in that: The height of the first filler is greater than or equal to the safe distance at which the drill stops working.

7. The method for manufacturing a circuit board according to claim 1, characterized in that: The removing the first filler to form a cavity on the motherboard includes: A knockout hole communicating with the first groove is provided on the motherboard, or the through hole is used as the knockout hole; The first filler is removed through the knockout hole.

8. The method for manufacturing a circuit board according to claim 7, characterized in that: Before removing the first filler through the knockout hole, the method further includes: The first filler is removed by heating the first filler to melt it or cooling it to powder it.

9. The method for manufacturing a circuit board according to claim 8, characterized in that: The first filler includes tin, and the first filler is removed by any of the following methods: applying a low temperature to the area where the first filler is located, so that the first filler is converted into powder and discharged from the removal hole; or applying a high temperature to the area where the first filler is located, so that the first filler is melted and discharged from the removal hole.

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

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