Application of tin as filler in circuit board manufacturing, method and filler

Abstract

The invention provides an application of tin as a filler in circuit board manufacturing, a method and a filler, and the filler is used for filling a cavity of a circuit board before lamination and is removed from the circuit board through high-temperature melting or low-temperature powdering after lamination. According to the application of the tin as the filler in manufacturing of the circuit board, on one hand, when the tin is used as the filler, the filler can stably and reliably play a supporting role in the pressing process of the circuit board, and the circuit board is prevented from being deformed in the pressing process; and on the other hand, the filler can be removed more simply and conveniently, and the damage to the circuit board is reduced, so that the filler can be removed more conveniently and reliably. The invention relates to the field of circuit board manufacturing.

Description

Technical Field

[0001] The present application relates to the field of circuit board manufacturing, and in particular to an application, method and filler of tin as a filler in circuit board manufacturing. Background Art

[0002] In some circuit board manufacturing processes, it is necessary to set a filler on the sub-board that can withstand the high temperature during pressing, and then remove the filler after pressing. However, the commonly used fillers are difficult to remove.

[0003] For example, as disclosed in Chinese patent CN114190014A, in order to facilitate the bending of the soft-hard combination circuit board, a cavity needs to be made between the two layers of soft board core boards. At this time, a window can be opened on the bonding sheet between the two layers of soft board core boards, and a filler (generally a hard gasket, such as PTFE gasket, etc.) can be placed. After pressing, a groove is milled from the side to expose the gasket, and the gasket is pulled out to form a cavity. At this time, the width of the slot must be greater than the width of the filler, which makes the slot difficult to close.

[0004] For example, as disclosed in Chinese patent CN118591116A, in order to make a metallized hole disconnected at a specified layer, it is necessary to bury a filler (generally a curable ink) between two specified layers of sub-boards, and after lamination and drilling, a stepped hole is formed by removing the filler so that metal can be selectively electroplated on the hole wall. In the related art, the filler is generally removed by chemical corrosion, which has the risk of side corrosion and damage to the sub-board. Summary of the invention

[0005] 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 an application, method and filler of tin as a filler in the production of circuit boards. The use of tin as a filler helps to easily remove the filler after lamination.

[0006] According to the application, tin is used as a filler in the production of circuit boards. The filler is used to fill the cavity of the circuit board before pressing, and is removed from the circuit board by high-temperature melting or low-temperature powdering after pressing.

[0007] According to the application, the application of tin as a filler in the production of circuit boards has at least the following technical effects: on the one hand, the melting point of tin (such as 232°C for elemental tin) is higher than the temperature during conventional pressing (about 200°C), so when tin is used as a filler, the filler can remain stable during the pressing process of the circuit board, reliably play a supporting role, and avoid deformation of the circuit board during pressing; on the other hand, above 232°C, the filler will turn into a liquid state, suitable for discharge through small holes, making it easier to remove the filler, and at the same time, since the melting point of tin and the pressing temperature are relatively close, the temperature in this process is not easy to cause damage to the circuit board; below 13.2°C, tin will undergo tin rust and transform into an allotrope of gray tin, thereby powdering the filler, which is suitable for discharge through small holes, making it easier to remove the filler, and since low temperature rather than high temperature is applied, the damage to the circuit board can be further reduced, so the removal of the filler can be more convenient and reliable.

[0008] According to some embodiments of the present application, the filler is used in any of the following: making a circuit board with a cavity inside; making a circuit board with a metallized hole that is disconnected at a set position; making a circuit board with a controlled depth hole; making a circuit board with a metallized half hole.

[0009] The circuit board manufacturing method provided in the present application includes: providing a daughter board; forming a groove on the daughter board; filling the groove with a filler, the melting point of the filler is greater than or equal to 180°C, and the filler has any of the following characteristics: the melting point of the filler is between 210°C and 270°C; the filler can be powderized at a temperature below 13.2°C; pressing the daughter boards to form a mother board; drilling holes in the mother board to expose the filler; removing the filler to form a cavity on the mother board.

[0010] The circuit board manufacturing method provided in the present application has at least the following technical effects: on the one hand, the filler can provide stable support during pressing to prevent the circuit board from deforming during pressing; on the other hand, the filler can be conveniently and low-damage removed from the circuit board by melting or powdering, thereby improving the yield and flexibility of the circuit board manufacturing method and meeting the needs of different circuit board manufacturing.

[0011] According to some embodiments of the present application, the filler includes tin, and removing the filler includes applying low temperature to the area where the filler is located to cause the filler to be transformed into powder and discharged from the hole.

[0012] According to some embodiments of the present application, a catalyst is added from the hole while applying a low temperature to promote tin pest in the filler.

[0013] According to some embodiments of the present application, removing the filler includes applying high temperature to the area where the filler is located to melt the filler and discharge it from the hole.

[0014] According to some embodiments of the present application, a plurality of holes are drilled on the mother board, and positive pressure or negative pressure is applied to a portion of the holes to promote the discharge of the filler.

[0015] According to some embodiments of the present application, before filling the groove, an isolation layer is formed on the surface of the groove to prevent the filler and the sub-board from combining during pressing.

[0016] According to some embodiments of the present application, after removing the filler, the process further includes filling the hole.

[0017] According to the filler provided by the present application, the filler includes tin, and the filler is used to fill the cavity of the circuit board before pressing, and is removed from the circuit board through high-temperature melting or low-temperature powdering after pressing.

[0018] The filler provided in the present application can be used to implement the circuit board manufacturing method of the present application. Therefore, the filler of the present application has the beneficial effects provided by the circuit board manufacturing method, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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.

[0020] Figure 1 An example of a pressure-temperature curve commonly used when pressing a circuit board is shown;

[0021] Figure 2 A flow chart showing a method for manufacturing a circuit board according to an embodiment of the present application is shown;

[0022] Figure 3 A schematic diagram showing the principle of the circuit board manufacturing method of the embodiment of the present application when manufacturing a cavity;

[0023] Figure 4 A schematic diagram showing the principle of the circuit board manufacturing method of the embodiment of the present application when manufacturing a cavity;

[0024] Figure 5 A schematic diagram showing the principle of the circuit board manufacturing method of the embodiment of the present application when manufacturing disconnected metallized holes;

[0025] Figure 6 A schematic diagram showing the principle of the circuit board manufacturing method of the embodiment of the present application when manufacturing a depth-controlled hole;

[0026] Figure 7 A schematic diagram showing the principle of the circuit board manufacturing method of an embodiment of the present application when manufacturing a half hole.

[0027] Reference numerals:

[0028] The sub-board 110 , the core board 111 , the bonding sheet 112 , the groove 120 , the filler 130 , the hole 140 , the heat sink 150 , the metal wall 160 , and the conductive structure 170 . DETAILED DESCRIPTION

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] In the process of circuit board manufacturing, sometimes it is necessary to first set a filler on the daughter board as a support, and then remove the filler after lamination. This requires the filler to have good support ability, be able to withstand the temperature and pressure during lamination, and be suitable for removal from the mother board.

[0035] 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 means of grooving, windowing, etc., and take it out from the opening. For example, as disclosed in Chinese patent CN114190014A, when making the cavity of a hard-soft circuit board or a flexible circuit board, a groove can be made from the process edge and the filler can be pulled out from the side. Chemical removal is to remove the filler by etching with a reagent. For example, as disclosed in Chinese patent CN118591116A, the embedded filler is etched to form a stepped portion of the via, so as to facilitate the production of disconnected metallized holes. However, the existing methods all have some shortcomings.

[0036] Specifically, in some processes, it is necessary to make a closed cavity (such as the air dielectric layer in a high-frequency and high-speed flexible circuit board). Since the size of the opening needs to be larger than the size of the filler, it is difficult to seal the filler after it is taken out. In some processes, it is necessary to make a cavity with a more complex shape (such as making a loop of heat dissipation medium inside the circuit board). Correspondingly, more complex openings are required to meet the requirements for removing the filler, which complicates the design of the circuit board. In some processes, the position of the filler is close to the circuit pattern, and the circuit pattern is easily damaged during chemical removal.

[0037] To this end, the present application proposes the use of tin as a filler in the production of circuit boards. The use of tin as a filler can meet the support and pressing requirements while being more suitable for removal.

[0038] Specifically, the application of tin as a filler in the production of circuit boards proposed in this application achieves the technical objectives of this application based on the following physical properties.

[0039] There are three allotropes of metallic tin: gray tin, white tin and brittle tin. Its Mohs hardness is only 3.75. It is one of the softest metals with good ductility but poor ductility. In the temperature range of 13.2℃-161℃, the properties of tin are relatively stable and are tetragonal lattices, called "white tin". Therefore, tin as a filler can play a good supporting effect in the circuit board and meet the requirements of supporting the cavity shape.

[0040] 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.

[0041] When the temperature is above 161℃, white tin turns into orthorhombic tin with orthorhombic crystal structure. Orthorhombic tin is more brittle and has poor ductility, so it is called "brittle tin".

[0042] In addition, when laminating the circuit board, the maximum temperature is generally slightly higher than 200°C, and the melting point of tin is 232°C, so tin as a filler is suitable for withstanding the laminating process of the circuit board.

[0043] by Figure 1 For example, Figure 1 A typical temperature-pressure curve of the pressing process is shown.

[0044] At the beginning of pressing, the pressure is increased first. When the pressure reaches the highest level, the temperature is around 110°C. At this time, the tin is in a stable white tin state, providing reliable support.

[0045] After that, the temperature is continuously raised on the basis of constant pressure, and the fluidity of the bonding sheet is further enhanced. When the temperature reaches about 140°C, the viscosity of the bonding sheet 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.

[0046] After that, the temperature continues to rise, the viscosity of the adhesive sheet gradually increases, the fluidity deteriorates and solidifies. 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 as the cavity), ensuring that the area is not occupied. At the same time, because the circuit board is in a stable placement during the hot pressing process, the filler is not impacted, so the brittle tin will not break and cause the glue flow to be squeezed in turn.

[0047] 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.

[0048] In summary, based on the physical properties of tin, the entire pressing process will not affect the space occupied by tin, and tin as a filler can meet the requirements of endurance pressing process.

[0049] By utilizing the physical properties of tin, it can be easily removed after hot pressing by heating or cooling.

[0050] Specifically, taking tin as an example, in the method of temperature removal, heating to slightly above 232°C can turn tin into liquid. At this time, it is only necessary to process holes connecting the cavity area to conveniently discharge the liquid tin from the holes. The position of the holes is not affected by the shape of the filler, and the size of the holes is not affected by the size of the filler. The size of the holes is small, and it is also suitable for filling when necessary. 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 filler.

[0051] Taking tin as an example, in the cooling removal method, cooling to below 13.2°C can cause tin to undergo tin aging and turn into a powder state. Cooling to below -30°C can accelerate this process. At this time, only holes connecting the cavity area need to be processed to easily discharge the powdered tin from the holes. The position of the holes is not affected by the shape of the filler, and the size of the holes is not affected by the size of the filler. In addition, the size of the holes is small, which is suitable for filling when necessary.

[0052] It is understandable that for some temperature-sensitive circuit boards, such as those with embedded precision components, the melting temperature may exceed the circuit board's tolerance range. However, 13.2°C will hardly have a negative impact on the circuit board. Using the cooling removal method can better avoid the problem of damaging the circuit board and more reliably remove the filler.

[0053] Based on the application of the filler proposed in the present application in the production of circuit boards, the present application further proposes a method for producing circuit boards and a filler.

[0054] According to the circuit board manufacturing method of the present application, the filler of the present application is used to fill the groove of the sub-board (core board, bonding sheet, etc.) before lamination; after lamination, the filler is removed to transform the groove into a cavity.

[0055] According to the filler of the embodiment of the present application, the component thereof includes tin, and the filler has any of the following characteristics:

[0056] The melting point of the filler is between 210°C and 270°C;

[0057] The filler can be powderized at a temperature below 20°C.

[0058] Optionally, refer to Figure 2 and Figure 3 According to the circuit board manufacturing method of the embodiment of the present application, the following steps are included:

[0059] Step S110: providing a daughter board 110 .

[0060] It is understandable that the circuit board in the related art is generally composed of a multi-layer sub-board 110, which includes a core board 111 (such as a copper-clad board) and a bonding sheet 112 (such as a prepreg). The core board 111 is used to make a circuit pattern, and the bonding sheet 112 is used to bond two adjacent core boards. Figure 3 In the illustrated embodiment, the sub-board 110 includes two core boards 111 and a bonding sheet 112 between the two core boards 111 .

[0061] Providing the daughter board 110 also includes the process of making the required circuit pattern on the core board 111, which will not be repeated here.

[0062] Step S120 : forming a groove 120 on the daughter board 110 .

[0063] The groove 120 is used to form a cavity in the subsequent Figure 3 In the illustrated embodiment, the groove 120 is a through groove. In other embodiments, the groove 120 may also be a blind groove. The shape of the groove 120 may be flexibly designed according to actual needs. According to design requirements, the cavity may be used as a medium layer, a flow channel, a weight reduction layer, etc., and the present application does not limit this.

[0064] Step S130 : filling the groove 120 with a filler 130 , wherein the filler 130 includes tin.

[0065] The filler 130 is used to play a supporting and space-occupying role. On the one hand, it prevents the sub-board above the groove 120 from collapsing and deforming during pressing. On the other hand, it prevents the glue (resin produced by the softening of the adhesive sheet) from flowing into the groove 120 during the pressing process, resulting in the space of the cavity being squeezed.

[0066] In the present application, tin is the main component of the filler 130, but the filler 130 is not required to be a single tin substance. It is allowed to add some other components to the filler 130 (that is, a tin alloy that meets the requirements as the filler 130) to adjust the physical properties of the filler 130, as long as it does not hinder the removal of the filler 130 by heating or cooling.

[0067] Optionally, the melting point of the filler 130 or the temperature at which tin poisoning occurs may be adjusted by adding other components according to the needs of the process flow.

[0068] For example, if there are other low-temperature links in the process, in order to prevent the filler 130 from being powdered prematurely, the occurrence temperature of tin pest may be lowered by adding aluminum or zinc.

[0069] Alternatively, ferromagnetic metal powder may be added to the filler 130 so that the filler 130 can be selectively locally heated by high-frequency electromagnetic heating.

[0070] For example, some iron powder can be sprinkled on the surface of the tin block to form the required filler 130; or some iron powder can be sandwiched between two tin blocks to form the required filler 130; or, tin can be melted in a mold, iron powder can be added and stirred evenly, and the required filler 130 can be formed after solidification.

[0071] Step S140: pressing the daughter board 110 to form a mother board.

[0072] It should be pointed out that there are many possible process routes for “pressing the daughter board 110 to form a mother board”, and this application does not impose any limitation on this.

[0073] Specifically, the motherboard refers to a composite structure formed by laminating multiple layers of daughter boards 110. In most processes, lamination is performed only once, so there is only one motherboard, and the number of layers of the motherboard is the same as the number of layers of the circuit board. However, in some other processes, multiple laminations are performed for the needs of board processing. For example, the daughter boards 110 are divided into multiple groups, and each is pressed into a motherboard, and then multiple motherboards are pressed together to produce the final circuit board. For example, the motherboard of the first stage is pressed first, and then a new daughter board 110 is superimposed after processing to press the motherboard of the second stage, and the above process is repeated to produce the final motherboard.

[0074] Step S150 : drilling a hole 140 on the motherboard to expose the filler 130 .

[0075] Step S160: removing the filler 130 to form a cavity on the motherboard.

[0076] As mentioned above, the filler 130 can be removed by melting at elevated temperatures or powdering at reduced temperatures. It should be noted that, since the production of a circuit board may also include other process steps such as circuit pattern production, steps S140, S150, and S160 are often not performed continuously. In the production process of the circuit board, steps S150 and S160 are often placed after various steps involving high temperature and high pressure treatment to prevent the lack of support cavities from being damaged under high temperature and high pressure.

[0077] In the method of removing by increasing temperature, the filler 130 may be removed by applying a high temperature to the area where the filler 130 is located, so that the filler 130 melts and is discharged from the hole 140 .

[0078] For example, ferromagnetic metal powder can be added to the filler 130, and high temperature can be applied to the area where the filler 130 is located by high-frequency electromagnetic heating. It can be understood that in the ordinary overall heating method, heat needs to be gradually transferred from the outer surface of the circuit board to the internal filler 130, so there is a temperature gradient in the circuit board. When the filler 130 reaches the target temperature, there is a risk that the temperature of the circuit board surface exceeds the allowable temperature of some surface structures or components. Electromagnetic heating can heat the filler 130 in a directionally manner, thereby avoiding this risk.

[0079] In the cooling removal method, the filler 130 can be optionally removed by applying a low temperature to the area where the filler 130 is located, so that the filler 130 is converted into powder and discharged from the hole 140 .

[0080] Furthermore, a catalyst (ie, gray tin) may be added from the hole 140 while applying a low temperature to promote tin aging of the filler 130 .

[0081] According to the circuit board manufacturing method provided by the present application, on the one hand, tin can provide stable support during pressing to prevent the circuit board from deforming during pressing; on the other hand, tin can be conveniently and low-damage removed from the circuit board by melting or powdering, meeting the special needs of removing filler 130 from smaller openings (such as hole 140) in the circuit board manufacturing process, thereby improving the yield and flexibility of the circuit board manufacturing method and being able to meet the needs of different circuit board manufacturing.

[0082] It is understandable that the previous embodiments introduced the circuit board manufacturing method of the present application by taking the tin-based filler 130 as an example, but the filler 130 applicable to the circuit board manufacturing method is not limited to the tin-based filler 130. As long as the melting point of the filler 130 is greater than or equal to 180°C, and the filler 130 has any of the following characteristics: the melting point of the filler 130 is between 210°C and 270°C; the filler 130 can be powdered at a temperature below 13.2°C, the basic requirements of the circuit board manufacturing method can be met.

[0083] However, the tin-based filler 130 (tin element or tin alloy) is preferred among the fillers 130 due to its powderization characteristics and suitable melting point and hardness.

[0084] It should be noted that the diameter of the hole 140 in the circuit board is generally small, for example, about 1 mm, so it is difficult for the filler 130 to be discharged by itself and it is easy to leave residue. In addition to increasing the diameter of the hole 140, auxiliary means can also be considered to promote the discharge of the filler 130.

[0085] Optionally, a plurality of holes 140 are drilled on the motherboard, and positive pressure or negative pressure is applied to some of the holes 140 to promote the discharge of the filler 130. The function of the plurality of holes 140 is to form a fluid circuit to prevent the pressure difference from hindering the discharge of the filler 130 (especially in the method of temperature increase removal). The pressure can be applied continuously or intermittently, and can be always positive pressure / negative pressure, or positive pressure and negative pressure can be applied alternately. The specific pressurization method can be determined based on the experimental results on the specific circuit board, that is, it is determined comprehensively based on factors such as the position of the hole 140 (front or side), the shape of the filler 130, and the present application does not limit this.

[0086] Optionally, for the cooling and removal method, since the fluidity of powder is lower than that of liquid, a solution can be injected into the area where the filler 130 is located through the hole 140, and the powdered filler 130 can be taken out with the solution to avoid residue. It should be noted that since the filler 130 has been powdered, even if it is insoluble in the solution, it can be taken out in the form of turbid liquid, so it is not required that the filler 130 must be soluble in the solution, but it is necessary to ensure that the solution will not react with other structures of the circuit board.

[0087] Optionally, regardless of whether the removal is performed by increasing the temperature or decreasing the temperature, in order to avoid residues in the cavity, it is preferred to drill a plurality of holes 140 on the motherboard, and clean the cavity with a cleaning liquid (such as deionized water) after removing the filler 130 .

[0088] In addition, to avoid residue, an isolation layer may be formed on the surface of the groove 120 before filling the groove 120 to prevent the filler 130 and the sub-board 110 from being combined during lamination. Specifically, the isolation layer may be formed by spraying an isolation material.

[0089] Finally, if the process requires, after removing the filler 130 , the hole 140 is further filled.

[0090] The tin of the present application as the filler 130 can be used to make different features on the circuit board. As long as there is a need for filling and support on the circuit board, the filler 130 of the present application can be considered. For example, the filler 130 can be used in any of the following:

[0091] Making a circuit board with a cavity inside;

[0092] Making a circuit board with metallized holes that are disconnected at set positions;

[0093] Make circuit boards with controlled depth holes;

[0094] Fabrication of circuit boards with metallized half holes.

[0095] The present application further illustrates the application of tin as a filler in the manufacture of circuit boards and the method for manufacturing circuit boards provided by the present application through the following specific embodiments. It is worth noting that the following description is only an exemplary description and not a specific limitation of the present application. This specific embodiment can also be replaced by the above-mentioned corresponding technical features or combined with the above-mentioned technical features.

[0096] Embodiment 1: Tin is used as a filler to make a circuit board with a cavity inside, wherein the cavity is used to form a flow channel for a heat dissipation medium.

[0097] Traditional circuit boards generally rely on heat conduction to dissipate heat, but the thermal conductivity of the board is relatively low and the heat dissipation effect is general, especially for multi-layer thick circuit boards. If the heat inside the core cannot be dissipated quickly, heat accumulation is likely to occur, which may cause the circuit board to fail in severe cases.

[0098] Some related technologies, such as Chinese patent CN206323638U, adopt buried copper heat dissipation, that is, burying copper blocks or copper pillars in certain areas, and conducting the internal heat to the surface for heat dissipation through the good thermal conductivity of copper. However, the position and shape and size of copper are limited, which greatly restricts the heat dissipation effect.

[0099] Reference Figure 4 According to the circuit board manufacturing method of the embodiment of the present application, the following steps are included:

[0100] Step S210: providing a daughter board 110 .

[0101] Exemplarily, the sub-board 110 of the present application includes two core boards 111 and a bonding sheet 112. The core board 111 has a heat generating area (not shown in the figure).

[0102] Step S220 : forming a groove 120 on the daughter board 110 .

[0103] like Figure 4 As shown, the groove 120 may be provided on the bonding sheet 112 . To meet the need of heat dissipation, the groove 120 forms a loop connected end to end, and the projection of the loop on the core board 111 passes through the heating area.

[0104] Step S230 : filling the groove 120 with a filler 130 , wherein the filler 130 includes tin.

[0105] In particular, in this embodiment, for the purpose of heat dissipation, a heat dissipation block 150 is additionally placed in the slot 120 , and the heat dissipation block 150 may be a copper block.

[0106] Step S240: pressing the daughter board 110 to form a mother board.

[0107] Step S250 : drilling a hole 140 on the motherboard to expose the filler 130 .

[0108] As mentioned above, in the circuit board manufacturing method of the present application, there is no need to open an opening that completely exposes the filler 130. It is only necessary to select a suitable position and open a hole 140 that partially exposes the filler 130, so that the position of the hole 140 and the shape of the groove 120 can be designed more flexibly.

[0109] Step S260: removing the filler 130 to form a cavity on the motherboard.

[0110] Step S270 : injecting cooling liquid into the cavity through the hole 140 , and then filling the hole 140 .

[0111] Since the filler 130 can be removed through the hole 140, the circuit board manufacturing method of the embodiment of the present application breaks through the limitation of the cavity shape in the related art, and is suitable for forming a large-scale, complex heat dissipation channel inside the circuit board (such as the end-to-end loop in this embodiment). As long as the fluid medium is injected into the loop and the power source is connected (such as the micro pump used in Chinese patent CN116614991A), the power source is driven by the line on the core board 111, so that the fluid medium can circulate in the loop, and the heat is efficiently transported from the heating area to the heat dissipation area (in this embodiment, the area where the heat dissipation block 150 is located), so that the heat dissipation of the circuit board is no longer limited by the position of the heat dissipation block 150, and the heat dissipation effect of the circuit board is improved. The power source can be built-in, such as buried in the circuit board before pressing like the heat dissipation block 150, or it can be external, such as set on the surface of the circuit board after pressing, and the present application does not limit this.

[0112] It should be emphasized that the present application takes the buried copper heat dissipation method in the related art as an example to demonstrate the positive role played by the circuit board manufacturing method of the present application in improving the heat dissipation effect. However, the use scenario of the circuit board manufacturing method of the present application is not limited to the buried copper heat dissipation method. In other heat dissipation methods, as long as there is a need to construct a heat dissipation channel, the circuit board manufacturing method of the present application can play a role, which helps to more flexibly construct the required heat dissipation channel inside the circuit board.

[0113] Example 2: Tin is used as a filler to produce a circuit board having metallized holes that are disconnected at set positions.

[0114] Circuit boards are multi-layer structures. During the manufacturing process, it is often necessary to disconnect the circuit patterns of a specified layer. In order to reduce the number of process steps, the relevant technology will drill holes after the entire board is pressed together, and then electroplate copper (that is, form metallized holes) to connect all layers through continuous electroplated copper holes. Then, through etching and other copper reduction operations, disconnected metallized holes are generated to achieve disconnection between certain specified layers.

[0115] When etching is performed, over-etching is prone to occur.

[0116] Reference Figure 5 According to the circuit board manufacturing method of the embodiment of the present application, the following steps are included:

[0117] Step S310: providing a daughter board 110 .

[0118] Exemplarily, the daughter board 110 of the present application includes four core boards 111 and three bonding sheets 112. The metallized hole needs to be disconnected between the two middle core boards 111.

[0119] Step S320 : forming a groove 120 on the sub-board 110 .

[0120] like Figure 5 As shown, the groove 120 is provided on the bonding sheet 112 between the middle two core plates 111 .

[0121] Step S330 : filling the groove 120 with a filler 130 , wherein the filler 130 includes tin.

[0122] Step S340: pressing the daughter board 110 to form a mother board.

[0123] Step S350 : making a metallized hole, wherein the metallized hole has a metal wall 160 for conducting the circuit patterns of each layer, and the metallized hole penetrates the filler 130 .

[0124] It is understandable that the metallized holes can be made using conventional processes, namely drilling, copper plating, and electroplating. The metal wall 160 here can be a metal wall 160 after copper plating or a metal wall 160 after electroplating. The specific production process can refer to the relevant existing technology and will not be repeated here.

[0125] Step S360 : drilling a hole 140 on the motherboard to expose the filler 130 .

[0126] As mentioned above, in the circuit board manufacturing method of the present application, there is no need to open an opening that completely exposes the filler 130. It is only necessary to select a suitable position and open a hole 140 that partially exposes the filler 130, so that the position of the hole 140 and the shape of the groove 120 can be designed more flexibly.

[0127] Step S370: removing the filler 130 to form a cavity on the motherboard.

[0128] Step S380: disconnecting the metal wall 160 corresponding to the cavity.

[0129] It can be understood that at this time, the metal wall 160 corresponding to the cavity is suspended in the air, lacks support, and has a weak resistance to pressure, while the other metal walls 160 are supported by the sub-board 110 and have a strong resistance to pressure. Therefore, the metal wall 160 corresponding to the cavity can be disconnected by applying pressure.

[0130] For example, a tool such as a brush can be used to rotate in the metallized hole to apply a certain pressure to the metal wall 160. Since the metal wall 160 is relatively thin, the metal wall 160 that lacks support will be destroyed, while the metal wall 160 that is tightly combined with the sub-board 110 can remain, thereby forming a good designated layer disconnection effect.

[0131] Alternatively, the metal wall 160 may be disconnected by applying positive pressure or negative pressure to the cavity. Preferably, negative pressure is used, that is, the metal wall 160 is disconnected inwardly, so that the edge of the metal wall 160 is not easily pulled outward, resulting in the edge of the metal wall 160 that needs to be retained being separated from the supporting part below.

[0132] The circuit board manufacturing method of the present application utilizes the presence or absence of the material to which the metal wall 160 is attached, and utilizes the pressure difference to break the metal wall 160 or destroy the connectivity of the metal wall 160. The solution is simple and feasible. In addition, this method is not prone to produce residual piles, thereby eliminating the need for subsequent controlled depth drilling to remove the residual piles, thereby improving the manufacturing efficiency of the circuit board.

[0133] It should be emphasized that the application scenario of the circuit board manufacturing method of the present application is not limited to destroying the metal wall 160 by pressure. In other metallized hole manufacturing methods (such as Chinese patent CN118591116A), as long as there is a need to form a cavity, the circuit board manufacturing method of the present application can play a role. In addition, Figure 5 The metallized hole is shown as being disconnected at only one position. In other more complex circuit boards, the metallized hole may have multiple disconnected positions, and the circuit board manufacturing method of the present application is also applicable.

[0134] Example 3: Using tin as a filler to make a circuit board with controlled depth holes.

[0135] In the circuit board, depth-controlled drilling is required, that is, blind holes need to be drilled to the specified layer. Here, depth-controlled drilling does not require precise depth, but accurate drilling to the position of the target layer, generally drilling through a certain copper layer or drilling to a certain copper layer without damaging the copper layer.

[0136] Due to the small thickness of the circuit board, the depth control accuracy requirement is extremely high, and due to the glue flow during the high-temperature pressing process, the thickness of each sub-board 110 may fluctuate compared to the original thickness. The thickness parameters of the sub-board 110 before pressing cannot be used as a reference, so feedback adjustment is required to control the drilling depth.

[0137] In the related art, the feedback signal is generally triggered by the circuit pattern on the core board 111, but this requires reserving a special area on the internal circuit pattern, which has a certain impact on the signal design of the circuit pattern.

[0138] Reference Figure 6 According to the circuit board manufacturing method of the embodiment of the present application, the following steps are included:

[0139] Step S410: providing a daughter board 110 .

[0140] Step S420 : forming a groove 120 on the sub-board 110 .

[0141] like Figure 6 As shown, in this embodiment, the depth control requirement is to drill to the copper layer on the surface of the core board 111, so a groove 120 is opened on the bonding sheet 112, and the groove 120 can be a blind groove or a through groove.

[0142] Step S430 : Filling the groove 120 with a filler 130 , wherein the filler 130 includes tin.

[0143] Step S440: Pressing the daughter board 110 to form a mother board.

[0144] Step S450: making a signal hole extending to the filler 130, setting a conductive structure 170 in the signal hole, the conductive structure 170 and the filler 130 are conductive, and the conductive structure 170 is used to form a feedback loop with the drill.

[0145] The drilling accuracy of the signal hole is not high due to the thickness of the filler 130 . For example, the drilling depth can be set to be slightly larger than the theoretical distance from the upper surface of the filler 130 to the circuit board surface to ensure that the signal hole extends to the filler 130 .

[0146] For example, conductive metal may be inserted into the signal hole or molten metal tin may be poured into the signal hole to achieve the conduction effect. The conduction structure 170 extends to the surface of the circuit board so as to be electrically connected to the drill.

[0147] Step S460: depth-controlled drilling. When the drill bit contacts the filler 130, the drill bit, the filler 130 and the conductive structure 170 connect the feedback loop and generate an electrical signal, indicating that the target position has been reached. It is understandable that depth-controlled 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.

[0148] Step S470 : drilling a hole 140 on the motherboard to expose the filler 130 , or using a signal hole as the hole 140 .

[0149] Step S480: removing the filler 130 to form a cavity on the motherboard.

[0150] Removing the filler 130 prevents the feedback loop from affecting the circuit pattern. Since the filler 130 blocks the circuit pattern, it is less likely to damage the circuit pattern when drilling.

[0151] Specifically, in the motherboard, the filler 130 is located above the copper layer, and the lower surface of the filler 130 is the target depth for depth control. However, due to the existence of the filler 130, the drill does not need to drill directly to the lower surface of the filler 130. It can stop as long as it drills to the upper surface of the filler 130, and then the filler 130 is removed to achieve the effect of depth control to the target copper layer. In this way, direct contact between the drill and the target copper layer is avoided, and the copper layer is prevented from being damaged during the drilling process of the drill.

[0152] It should be emphasized that the method of generating feedback electrical signals in depth-controlled drilling is not limited to the method exemplified in this embodiment. The circuit board manufacturing method of the present application can also play a role in other feedback methods, which helps to more flexibly set the conductor for feedback (that is, the filler 130) inside the circuit board, and is suitable for removal from the circuit board after the depth-controlled drilling is completed.

[0153] Example 4: A circuit board with metallized half holes is made using tin as a filler.

[0154] There is a metallized half-hole design in the soft board area of ​​the hard-flex circuit board. For the half-hole shape processing of the soft board area, there are generally three types of processing: punching, laser processing, and milling. Punching brings mold investment costs, laser processing has carbon black defects, and milling processing has burrs in the suspended position of the half hole.

[0155] In related technologies (such as Chinese patent CN105934097A), fillers are generally used to plug holes first, and then milling is performed to avoid burr problems. The fillers are subsequently removed by chemical etching, which can easily cause problems such as filler residue and damage to surrounding circuit patterns.

[0156] Reference Figure 7 According to the circuit board manufacturing method of the embodiment of the present application, the following steps are included:

[0157] Step S510: providing a daughter board 110 .

[0158] Step S520 : forming a groove 120 on the daughter board 110 .

[0159] like Figure 7 As shown, in this embodiment, a via hole (ie, groove 120 ) is processed on a core board 111 (specifically, a flexible board core board), and then the via hole is metallized to form a metallized hole.

[0160] Step S530: Filling the metallization hole with a filler 130, wherein the filler 130 includes tin.

[0161] For example, first, tape is applied to one side of the metallized hole as a barrier; then, a tin rod / tin powder as a filler 130 is inserted into the metallized hole, and high-frequency heating is used to melt the tin so that the tin fills the entire metallized hole; next, the tape is torn off and then browned; finally, a barrier protective tape is applied to the entire area of ​​the flexible board.

[0162] Step S540: pressing the daughter board 110 to form a mother board.

[0163] Step S550: milling the metallized hole to form a half hole.

[0164] Step S560: opening the cover on the motherboard to expose the soft board area of ​​the circuit board and the filler 130 at the same time.

[0165] Step S570: removing the filler 130 to form a desired half hole.

[0166] It should be emphasized that the circuit board manufacturing method of the present application can play a role in other half-hole processing methods, help provide reliable support, thereby ensuring the processing quality of the half-hole, and is suitable for removal from the circuit board after the half-hole processing is completed.

[0167] In some selectable embodiments, the function / operation mentioned in the block diagram 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. Selectable embodiments are expected, wherein the order of various operations is changed and the sub-operation of a part described as a larger operation is performed independently.

[0168] 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. An application of tin as a filler in the production of circuit boards, characterized in that: The filler is used to fill the cavity of the circuit board before lamination, and is removed from the circuit board by high-temperature melting or low-temperature powderization after lamination.

2. The use of tin as a filler in circuit board production according to claim 1, characterized in that: The filler is used in any of the following: Making a circuit board with a cavity inside; Making a circuit board with metallized holes that are disconnected at set positions; Make circuit boards with controlled depth holes; Fabrication of circuit boards with metallized half holes.

3. A method for manufacturing a circuit board, characterized in that: include: Provide daughterboard; forming a slot on the daughter board; Filling the groove with a filler, the melting point of the filler is greater than or equal to 180° C., and the filler has any of the following characteristics: the melting point of the filler is between 210° C. and 270° C.; the filler can be powderized at a temperature below 13.2° C.; Pressing the daughter boards to form a mother board; Drilling holes in the motherboard to expose the filler; The filler is removed to form a cavity on the mother board.

4. The method for manufacturing a circuit board according to claim 3, characterized in that: The filler includes tin, and removing the filler includes applying low temperature to the area where the filler is located, so that the filler is transformed into powder by tin powder and discharged from the hole.

5. The method for manufacturing a circuit board according to claim 4, characterized in that: While applying low temperature, a catalyst is added from the holes to promote tin calcination of the fill.

6. The method for manufacturing a circuit board according to claim 3, characterized in that: Removing the filler includes applying high temperature to the area where the filler is located to melt the filler and discharge it from the hole.

7. The method for manufacturing a circuit board according to any one of claims 3 to 6, characterized in that: A plurality of holes are drilled on the mother board, and positive or negative pressure is applied to a portion of the holes to promote the discharge of the filler.

8. The method for manufacturing a circuit board according to claim 3, characterized in that: Before filling the groove, the method further includes forming an isolation layer on the surface of the groove to prevent the filler and the sub-board from being combined during lamination.

9. The method for manufacturing a circuit board according to claim 3, characterized in that: After removing the filler, the method further includes plugging the hole.

10. A filler, characterized in that: The filler includes tin, which is used to fill the cavity of the circuit board before lamination and is removed from the circuit board by high-temperature melting or low-temperature powderization after lamination.

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