WO2024099148A1

WO2024099148A1 - Circuit board, electronic device, and manufacturing method for circuit board

Info

Publication number: WO2024099148A1
Application number: PCT/CN2023/127969
Authority: WO
Inventors: 刘志涛; 韩磊; 徐可新
Original assignee: 华为技术有限公司
Priority date: 2022-11-10
Filing date: 2023-10-30
Publication date: 2024-05-16
Also published as: CN118019216A

Abstract

The present application relates to the technical field of terminal devices. Provided in the embodiments are a circuit board, an electronic device and a manufacturing method for the circuit board. The circuit board comprises an adapter board, and a first functional board and a second functional board which are arranged on the two sides of the adapter board respectively, the first functional board and the second functional board being electrically connected by means of the adapter board. The adapter board comprises a base board, a first conductive layer and a conductive structure. The base board is provided with a through hole, and the base board comprises a first surface and a second surface which are opposite to each other. The first conductive layer comprises two first conductive portions and a second conductive portion, the two first conductive portions being respectively arranged on the first surface and the second surface of the base board, and the second conductive portion covering the inner wall of the through hole and being connected to the two first conductive portions. At least part of the conductive structure fills the through hole and is in contact with the second conductive portion. One end of the conductive structure is electrically connected to the first functional board, while the other end of the conductive structure is electrically connected to the second functional board. With a simple structure, the adapter board can save design space, thereby helping to achieve miniaturization of adapter boards.

Description

Circuit board, electronic device and method for preparing circuit board

This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on November 10, 2022, with application number 202211407632.0 and application name "Circuit board, electronic device and method for preparing circuit board", all contents of which are incorporated by reference in this application.

Technical Field

The present application relates to the technical field of terminal equipment, and in particular to a circuit board, an electronic device, and a method for preparing the circuit board.

Background technique

With the rapid development of electronic technology, the demand for the number and performance of various functional components of terminal equipment has gradually increased, resulting in greater challenges to the design space of terminal equipment. In order to achieve more reasonable space utilization and solve the problem of increased terminal equipment size and difficulty in miniaturization due to the increase in the number of functional components, "sandwich structure" circuit boards came into being.

A "sandwich structure" circuit board refers to two functional boards for carrying electronic devices stacked in the thickness direction, and the two functional boards are electrically connected through a adapter board, thereby expanding the design space from two-dimensional to three-dimensional and improving the integration of the circuit board.

Summary of the invention

The embodiments of the present application provide a circuit board, an electronic device, and a method for preparing the circuit board, aiming to simplify the structure of the adapter board and save design space, thereby facilitating the miniaturization design of the circuit board.

To achieve the above objectives, the embodiments of the present application adopt the following technical solutions:

In a first aspect, a circuit board is provided. The circuit board includes an adapter board, and a first function board and a second function board respectively arranged on both sides of the adapter board. The first function board and the second function board are electrically connected through the adapter board.

The adapter board includes a substrate, a first conductive layer and a conductive structure. The substrate is provided with a through hole; the substrate includes a first surface and a second surface opposite to each other. The first conductive layer includes two first conductive parts and a second conductive part; the two first conductive parts are provided on the first surface and the second surface of the substrate, and the second conductive part covers the inner wall of the through hole and is connected to the two first conductive parts. At least part of the conductive structure is filled in the through hole and contacts the second conductive part; one end of the conductive structure is electrically connected to the first functional board, and the other end of the conductive structure is electrically connected to the second functional board.

In the circuit board provided in the embodiment of the present application, a conductive structure is arranged in the through hole of the adapter board, so that the first functional board and the second functional board located on both sides of the adapter board can be electrically connected through the conductive structure; at the same time, the conductive structure can also serve as a filler for the through hole to form an effective support for the first functional board and the second functional board, thereby avoiding the collapse of the parts of the first functional board and the second functional board corresponding to the through hole position toward the through hole, thereby improving the reliability of the circuit board; in addition, the adapter board in the embodiment of the present application can achieve the electrical connection between the first functional board and the second functional board only through the conductive structure, and has a simple structure, avoiding the design of a complex structure at the location of the through hole, thereby reducing the space occupied by the pad at the location of each through hole, saving the design space of the adapter board, and facilitating the miniaturization design of the adapter board and even the circuit board.

In a possible implementation manner of the first aspect, in the axial direction of the through hole, two ends of the conductive structure protrude beyond the surface of the two first conductive portions away from the substrate.

The first functional board and the second functional board located on both sides of the adapter board can be electrically connected to the adapter board by welding, for example, solder paste is applied between the conductive structures of the first functional board and the adapter board, and solder paste is applied between the conductive structures of the second functional board and the adapter board, and soldering is achieved by reflow soldering. The solder paste between the functional board (the first functional board or the second functional board) and the adapter board has a certain fluidity. Under the extrusion of the functional board and the adapter board, the solder paste corresponding to the two adjacent conductive structures will flow along the board surface and approach or even contact each other, that is, a bridging problem occurs, resulting in problems such as short circuit or failure of the circuit board.

By arranging the two ends of the conductive structure to protrude from the surface of the two first conductive parts away from the substrate, a certain space is provided between the board surfaces of the functional board and the adapter board (for example, the plane where the surface of the first conductive part away from the substrate is located) under the support of the protruding parts of the conductive structure, thereby avoiding the problem of bridging caused by excessive squeezing of the solder paste by the board surfaces of the functional board and the adapter board, thereby effectively improving the performance of the circuit board.

In a possible implementation manner of the first aspect, a surface of the protruding portion of the conductive structure is a curved surface, and the curved surface is bent toward the substrate.

By setting the surface of the protruding part of the conductive structure to be a curved surface, sufficient contact can be made between the solder paste and the conductive structure of the adapter board, thereby avoiding the problem of residual bubbles due to insufficient contact between the solder paste and the conductive structure due to the irregular surface of the part of the conductive structure that is used to contact the solder paste, which can easily cause cold soldering.

In a possible implementation manner of the first aspect, along the axial direction of the through hole, a maximum distance between the protruding portion of the conductive structure and a surface of the first conductive portion away from the substrate is 10 μm to 100 μm.

That is, the maximum value of the height of the protruding portion of the conductive structure is set to 10 μm to 100 μm, thereby effectively avoiding the solder connection problem caused by the extrusion between the functional board and the adapter board.

In a possible implementation manner of the first aspect, in the axial direction of the through hole, two ends of the conductive structure are recessed relative to the two first conductive portions and away from the surface of the substrate.

By setting the two ends of the conductive structure to be recessed relative to the surface of the two first conductive parts away from the substrate, the space for holding the solder paste between the board surfaces of the functional board and the adapter board (for example, the plane where the surface of the first conductive parts away from the substrate is located) becomes larger. Similarly, the degree of squeezing of the solder paste by the board surfaces of the functional board and the adapter board can be reduced, thereby avoiding the problem of bridging the solder, and effectively improving the performance of the circuit board.

In a possible implementation manner of the first aspect, end surfaces at both ends of the conductive structure are curved surfaces, and the curved surfaces are bent away from the substrate.

By setting the end faces of both ends of the conductive structure as curved surfaces, sufficient contact can be made between the solder paste and the conductive structure of the adapter board, thereby avoiding the problem of residual bubbles due to insufficient contact between the solder paste and the conductive structure due to the irregular surface of the part of the conductive structure that is used to contact the solder paste, which can easily cause cold soldering.

In a possible implementation manner of the first aspect, along the axial direction of the through hole, a maximum distance between the recessed portion of the conductive structure and a surface of the first conductive portion away from the substrate is 10 μm to 100 μm.

That is, the maximum value of the recessed portion of the conductive structure is set to be 10 μm to 100 μm, thereby effectively avoiding the solder joint problem caused by the extrusion between the functional board and the adapter board.

In a possible implementation of the first aspect, the conductive structure includes a main body, and two sub-parts disposed at both ends of the main body and connected to the main body. The main body is filled in the through hole. On the same surface of the substrate, the sub-part covers at least part of the first conductive part. The two sub-parts are electrically connected to the first functional board and the second functional board respectively.

By setting a sub-portion of the conductive structure to cover the first conductive portion, the position of the adapter board in contact with the first functional board and the second functional board can be made smooth, thereby improving the reliability of welding between the adapter board and the functional board (the first functional board or the second functional board).

In a possible implementation manner of the first aspect, the material of the conductive structure includes one or more of tin, copper and silver.

In a possible implementation manner of the first aspect, a diameter of the through hole is 150 μm to 250 μm.

In the embodiments provided in the present application, the aperture of the through hole can be made larger, for example, 200 μm, that is, a larger drill bit can be used to prepare the through hole, thereby reducing the difficulty of the drilling process and reducing the drilling cost.

In a possible implementation manner of the first aspect, a distance between two adjacent through holes is greater than or equal to 400 μm.

In the embodiment provided in the present application, the conductive structure used to realize the electrical connection between the first functional board and the second functional board has a simple structure and occupies a small area of the adapter board. Therefore, the spacing between two adjacent through holes can be reduced to 400μm, thereby saving the design space for setting the through holes on the adapter board, which is conducive to the miniaturization design of the adapter board and even the circuit board.

In a possible implementation of the first aspect, the circuit board further includes a first connection structure and a second connection structure. The first connection structure is provided between the first functional board and the adapter board, and one end of the conductive structure is welded to the first functional board through the first connection structure. The second connection structure is provided between the second functional board and the adapter board, and the other end of the conductive structure is welded to the second functional board through the second connection structure.

The melting point of the conductive structure is greater than the melting point of the first connecting structure, and greater than the melting point of the second connecting structure. The melting point of the first connecting structure is not equal to the melting point of the second connecting structure.

By setting the melting point of the conductive structure to be greater than the melting point of the first connection structure and greater than the melting point of the second connection structure, it is possible to prevent the conductive structure from melting in the high temperature environment during the welding process between the adapter board and the functional board (the first functional board and the second functional board), thereby preventing the structure of the adapter board from being damaged. By setting the melting point of the first connection structure to be unequal to the melting point of the second connection structure, it is possible to prevent the welding process of the first functional board and the welding process of the second functional board from affecting each other. For example, when the first functional board and the adapter board are welded first and then the second functional board and the adapter board are welded, the melting point of the first connection structure is greater than the melting point of the second connection structure, thereby preventing the solder paste of the welded first functional board from melting during the welding process between the second functional board and the adapter board.

In a possible implementation of the first aspect, the substrate includes at least one substrate and multiple second conductive layers, the substrate and the second conductive layers are alternately stacked, and the second conductive layers are respectively disposed on both sides of the substrate. One conductive part is close to one side of the substrate, and the second conductive layer overlaps the first conductive part. That is, the embodiment of the present application can also be applied to a transfer board of a multilayer board, and has a wide range of applications.

In a possible implementation of the first aspect, the circuit board further includes two solder resist layers, which are respectively disposed on the first surface and the second surface of the substrate; on the same surface of the substrate, at least part of the solder resist layers is located between two adjacent first conductive portions.

By arranging at least part of the solder resist layer between two adjacent first conductive parts on the same surface of the substrate, the phenomenon of solder joints between the solders at the positions of adjacent through holes can be further avoided, thereby optimizing the reliability of the circuit board.

In a second aspect, an electronic device is provided, the electronic device comprising a plurality of electronic devices and a circuit board according to any one of the embodiments of the first aspect, wherein the plurality of electronic devices are disposed on a first functional board and a second functional board.

The technical effects brought about by the electronic device in the second aspect can refer to the technical effects brought about by the design method of the circuit board in the first aspect, and will not be repeated here.

In a third aspect, a method for preparing a circuit board is provided, comprising: providing a substrate, the substrate comprising a first surface and a second surface opposite to each other; forming a through hole penetrating the substrate; plating a first conductive layer in the through hole and on the first surface and the second surface; etching the first conductive layer to form two first conductive portions located on the first surface and the second surface; and filling a conductive structure in the through hole plated with the first conductive layer.

The technical effects brought about by the preparation method in the third aspect can be referred to the technical effects brought about by the design method of the circuit board in the first aspect, and the technical effects brought about by the electronic device in the second aspect, which will not be repeated here.

In a possible implementation of the third aspect, a conductive structure is filled in a through hole plated with a first conductive layer, including: placing a tin ball on the through hole plated with the first conductive layer; heating the tin ball so that the tin ball melts and fills the through hole; and solidifying the melted tin ball to form a conductive structure.

The conductive structure is filled into the through hole by solder ball planting to achieve the preparation of the conductive structure, avoid the use of resin injection and other preparation processes with high operation difficulty, and reduce the preparation difficulty and preparation cost of the adapter board.

In a possible implementation of the third aspect, after the conductive structure is filled in the through hole plated with the first conductive layer, it also includes: welding the first functional board at one end of the conductive structure at a first preset temperature; welding the second functional board at the other end of the conductive structure at a second preset temperature.

The heating temperature of the solder ball is greater than the first preset temperature and greater than the second preset temperature; the first preset temperature is not equal to the second preset temperature.

By setting the heating temperature of the solder ball to be greater than the first preset temperature and greater than the second preset temperature, it is possible to prevent the welding temperature during the welding process of the first functional board and the adapter board, and the welding temperature during the welding process of the second functional board and the adapter board from melting the conductive structure and damaging the adapter board. By setting the first preset temperature to be unequal to the second preset temperature, it is possible to prevent the welding process of the first functional board and the adapter board, and the welding process of the second functional board and the adapter board from influencing each other. For example, when the first functional board and the adapter board are welded first and then the second functional board and the adapter board are welded, the first preset temperature is greater than the second preset temperature, which can prevent the solder paste of the welded first functional board from melting during the welding process of the second functional board and the adapter board.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application;

FIG2 is a schematic diagram of the structure of a circuit board provided in an embodiment of the present application;

FIG3 is a cross-sectional view of the circuit board along the section line A-A' in FIG2;

FIG4 is a schematic diagram of the structure of an adapter board provided in an embodiment of the present application;

FIG5 is an enlarged view of the structure of the area where the dotted box B in FIG4 is located;

FIG6 is a cross-sectional view of the adapter plate along the section line C-C' in FIG5;

FIG7 is another cross-sectional view of the adapter plate along the section line C-C' in FIG5;

FIG8 is another cross-sectional view of the adapter plate along the section line C-C' in FIG5;

FIG9 is another cross-sectional view of the adapter plate along the section line C-C' in FIG5;

FIG10 is another cross-sectional view of the adapter plate along the section line C-C' in FIG5 ;

FIG11 is another cross-sectional view of the adapter plate along the section line C-C' in FIG5 ;

FIG12 is another cross-sectional view of the adapter plate along the section line C-C' in FIG5;

FIG13 is another cross-sectional view of the adapter plate along the section line C-C' in FIG5;

FIG14 is another cross-sectional view of the adapter plate along the section line CC' in FIG5;

FIG15 is a cross-sectional view of the circuit board along the section line C-C' in FIG5;

FIG16 is a flow chart of preparing a circuit board provided in an embodiment of the present application;

FIG17 is a cross-sectional view of each preparation step in FIG16;

FIG18 is another preparation flow chart of a circuit board provided in an embodiment of the present application;

FIG19 is another preparation flow chart of a circuit board provided in an embodiment of the present application;

FIG. 20 is a cross-sectional view of each preparation step in FIG. 19 .

Detailed ways

The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in some embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments provided by the present application, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present application.

In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", 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.

Unless the context requires otherwise, throughout the specification and claims, the term "including" is interpreted as an open, inclusive meaning, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "exemplarily" or "some examples" and the like are intended to indicate that specific features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present application. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more.

When describing some embodiments, the term "connection" and its derivative expressions may be used. For example, when describing some embodiments, the term "connection" may be used to indicate that two or more components have direct physical or electrical contact with each other.

Exemplary embodiments are described herein with reference to cross-sectional views and/or plan views that are idealized exemplary drawings. In the drawings, the thickness of layers and regions are exaggerated for clarity. Therefore, variations in shape relative to the drawings due to, for example, manufacturing techniques and/or tolerances are conceivable. Therefore, the exemplary embodiments should not be interpreted as being limited to the shapes of the regions shown herein, but include shape deviations due to, for example, manufacturing. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the actual shapes of regions of the device, and are not intended to limit the scope of the exemplary embodiments.

Some embodiments of the present application provide an electronic device. The electronic device may be a consumer electronic product, a home electronic product, a vehicle-mounted electronic product, a financial terminal product, or a communication electronic product. Among them, consumer electronic products include, for example, mobile phones, tablet computers, laptop computers, e-readers, personal computers (PCs), personal digital assistants (PDAs), desktop displays, smart wearable products (e.g., smart watches, smart bracelets), virtual reality (VR) terminal devices, augmented reality (AR) terminal devices, drones, cars, etc. Home electronic products include, for example, smart door locks, televisions, remote controls, refrigerators, rechargeable small household appliances (e.g., soybean milk machines, sweeping robots), etc. Vehicle-mounted electronic products include, for example, vehicle-mounted navigation systems, vehicle-mounted high-density digital video discs (DVDs), etc. Financial terminal products include, for example, automated teller machines (ATMs), self-service terminals, etc. Communication electronic products include, for example, servers, storage devices, radars, base stations and other communication equipment.

Fig. 1 is a schematic diagram of the structure of an electronic device 1000 provided in an embodiment of the present application. As shown in Fig. 1 , the electronic device 1000 may include a plurality of electronic devices 200 and a circuit board 100.

The circuit board 100 is designed as a sandwich structure. Referring to FIG. 2 and FIG. 3 , the circuit board 100 includes a first functional board 10 and a second functional board 20. The first functional board 10 and the second functional board 20 are stacked in the thickness direction of the board and electrically connected through the adapter board 30 therebetween, thereby realizing the expansion of the circuit board 100 from two dimensions to three dimensions, reducing the area occupied by the circuit board 100 in the electronic device 1000, saving the design space for arranging the circuit board 100 in the electronic device 1000, and improving the electronic device 1000. The integration level of the sub-device 1000 facilitates the miniaturization design of the electronic device 1000 .

2 and 3 , a plurality of electronic devices 200 are disposed on the first function board 10 and the second function board 20 .

Exemplarily, a plurality of electronic devices 200 may be disposed on the first functional board 10 and the second functional board 20 by surface mounting technology. For example, the electronic devices 200 may be welded on the first functional board 10 and the second functional board 20 by ball-jointed array packaging technology.

The electronic device 200 is used to implement specific functions. For example, the electronic device 200 is used to implement a signal transmission function, a signal receiving function, a storage function, a temperature sensing function, a fault detection function, and the like.

By way of example, the electronic device 200 may include one or more of a resistor, an inductor, a capacitor, a switch (eg, a relay), an oscillator, a transistor, a rectifier, a transformer, a diode, and a potentiometer.

Exemplarily, the electronic device 200 may also include one or more chips such as a processor chip, a memory chip, a radio frequency chip, a radio frequency power amplifier chip, a power management chip, and a touch control chip.

It should be noted that the electronic device 200 may also be other devices that can realize specific functions. This application only gives examples of the types of the electronic device 200 and does not limit them.

It is also understood that the structure illustrated in the embodiment of the present application does not constitute a specific limitation on the electronic device 1000. In other embodiments of the present application, the electronic device 1000 may include more or fewer components than shown in the figure, or combine some components, or split some components, or arrange the components differently. The components shown in the figure may be implemented in hardware, software, or a combination of software and hardware.

For example, in some embodiments, the electronic device 1000 may also include input and output devices (such as a keyboard, a display screen, a camera, a USB interface, etc.), a heat sink, a battery, a speaker, etc.

For example, in some embodiments, the electronic device 1000 may further include a rear shell and a cover plate, and the rear shell and the cover plate may be combined to form a cavity that can hold the circuit board 100 .

With the development of science and technology, the functions of the electronic device 1000 are increasing. Correspondingly, the number of electronic devices 200 in the electronic device 1000 for realizing the various functions is also increasing. At the same time, as users' requirements for the performance of the various functions of the electronic device 1000 (such as computing power, computing speed, etc.) are continuously improved, the size of some components in the electronic device 1000 (including the circuit board 100 and the electronic device 200) is getting larger and larger, resulting in a significant squeeze on the design space of the electronic device 1000.

In order to solve the above technical problems, a circuit board 100 with a sandwich structure comes into being.

In the related art, as shown in Fig. 6, the adapter board 30' includes a substrate 1' (including a substrate 11' and a second conductive layer 12'), a first conductive layer 2', a filling structure 3' and an auxiliary conductive layer 4'. The substrate 1' is provided with a through hole K', and the first conductive layer 2' is plated on the inner wall of the through hole K' and the two side surfaces of the substrate 1', so that the circuits on the upper and lower side surfaces of the substrate 1' are connected through the first conductive layer 2'.

Among them, the material of the filling structure 3’ is resin, and the filling structure 3’ is injected into the through hole K’ by using the resin plugging process, so as to fill the through hole K’. This can avoid the problem that the first functional board 10 and the second functional board 20 are recessed toward the through hole K’ at the position of the through hole K’, causing the circuit board 100 to fail.

After the filling structure 3’ is formed by the resin plugging process, resin remains on the surface of the first conductive layer 2’ away from the substrate 1’, and the resin is an insulating material. The resin remaining on the surface of the first conductive layer 2’ will cause the conductivity between the functional board (refer to the first functional board 10 or the second functional board 20 in Figure 3) and the adapter board 30’ to be poor, and will also cause the surface of the first conductive layer 2’ to be uneven, thereby reducing the reliability of welding between the functional board and the adapter board 30’. Therefore, it is necessary to grind the surface of the first conductive layer 2’ and plate an auxiliary conductive layer 4’ on the surface of the first conductive layer 2’, so as to improve the conductivity while making the pads T’ on the adapter board 30’ for welding with the functional board (refer to Figure 6, the auxiliary conductive layer 4’ is patterned to form multiple pads T’) relatively flat, thereby improving the reliability of welding between the adapter board 30’ and the functional board.

The inventors of the present application have discovered through research that the adapter plate 30’ provided in the related art has a complex structure, and after the adapter plate 30’ is coated with the auxiliary conductive layer 4’, the auxiliary conductive layer 4’ blocks the through hole K’, thereby reducing the accuracy of positioning the through hole K’. When positioning the through hole K’ and forming the pad T’ on the through hole K’, it is necessary to prepare the pad T’ according to the correction value (the sum of the ideal value and the error value), that is, in order to eliminate the positioning error, it is necessary to enlarge the actual size value of the pad T’ based on the ideal size value, so as to avoid the situation where the pad T’ cannot cover the through hole K’ due to the positioning error. Therefore, the size of the pad T’ formed by the adapter plate 30’ in the related art is relatively large, which makes the utilization rate of the design space of the adapter plate 30’ low.

In order to optimize the design space of the adapter board 30 while ensuring the welding effect between the adapter board 30 and the functional board (the first functional board 10 or the second functional board 20 ), an embodiment of the present application provides a circuit board 100 .

FIG. 2 is a diagram of a stacked structure of a circuit board 100 provided in an embodiment of the present application, and FIG. 3 is a cross-sectional view of a circuit board 100 provided in an embodiment of the present application.

As shown in FIG. 2 and FIG. 3 , the first functional board 10 and the second functional board 20 are used to carry a plurality of electronic devices 200 , and to implement wiring, electrical connection, and electrical insulation between some electronic devices 200 , so as to meet the electrical characteristics of the electronic devices 200 .

Exemplarily, the first functional board 10 and the adapter board 30 are electrically connected by welding, and the first functional board 10 and the adapter board 30 are electrically connected by welding. For example, solder paste is applied between the functional board (the first functional board 10 or the second functional board 20) and the adapter board 30, and welding is achieved by reflow soldering.

Exemplarily, the first functional board 10 and the second functional board 20 may have the same shape or area, and the first functional board 10 and the second functional board 20 may be completely overlapped, thereby saving design space.

Alternatively, illustratively, the shapes or areas of the first functional board 10 and the second functional board 20 may be different. For example, referring to FIG. 2 , the area of the first functional board 10 is larger than that of the second functional board 20 , and the second functional board 20 is stacked on top of the first functional board 10 .

Exemplarily, the first functional board 10 and the second functional board 20 may be single-sided boards, double-sided boards, or multi-layer boards. For example, referring to FIG3 , the first functional board 10 is a double-sided board, and electronic devices 200 are disposed on both sides of the first functional board 10 close to and away from the second functional board 20, while the second functional board 20 is a single-sided board, and electronic devices 200 are disposed only on one side of the second functional board 20 close to the first functional board 10.

Exemplarily, the first function board 10 and the second function board 20 are provided with a plurality of circuits to realize interconnection, power supply, control and function realization between the electronic devices 200. For example, the first function board 10 and the second function board 20 are provided with a radio frequency circuit, a voice circuit, a processor and a memory circuit, a power supply and a charging circuit, etc.

Exemplarily, one of the first function board 10 and the second function board 20 may be a main board, and the other may be a radio frequency board. For example, the first function board 10 is a main board on which electronic devices 200 such as a processor chip are carried, and the second function board 20 is a radio frequency board on which a radio frequency chip is carried to realize functions such as frequency transmission and reception, frequency synthesis, and power amplification.

For example, one of the first function board 10 and the second function board 20 may be a main function board, and the other may be a secondary function board. A plurality of electronic devices 200 are disposed on the first function board 10 and the second function board 20 .

It should be noted that the present application does not limit the specific functions implemented by the first functional board 10 and the second functional board 20, and the types of electronic devices 200 arranged thereon. Any structural design of two functional boards electrically connected through the adapter board 30 is within the protection scope of the present application.

Fig. 4 is a top view of the adapter board 30 provided in the embodiment of the present application. As shown in Fig. 4, the adapter board 30 in the circuit board 100 provided in the present application is provided with a plurality of through holes K.

Among them, one side of the adapter board 30 close to the first functional board 10 and one side of the adapter board 30 close to the second functional board 20 are connected through the conductive medium set in the through hole K, so that the first functional board 10 and the second functional board 20 electrically connected to the two sides of the adapter board 30 are conductive.

FIG5 is a partial enlarged view of a top view of the adapter board 30 provided in an embodiment of the present application. As shown in FIG5, each through hole K of the adapter board 30 is provided with a pad T covering the through hole K, and each through hole K is provided with two pads T, which are provided on both sides of the adapter board 30 (see FIG7 to FIG14). The pad T is used to electrically connect to the functional board (the first functional board 10 or the second functional board 20) (see FIG15).

7 to 14 are cross-sectional views of the adapter plate 30 provided in the embodiment of the present application.

As shown in FIGS. 7 to 14 , the adapter board 30 includes a substrate 1 , a first conductive layer 2 and a conductive structure 3 .

7 to 14 , the substrate 1 is provided with a through hole K. Exemplarily, the substrate 1 is drilled by a dedicated drilling tool to form the through hole K.

7 to 14 , the substrate 1 includes a first surface 1 a and a second surface 1 b opposite to each other.

Exemplarily, the surface of the substrate 1 close to the first functional board 10 is the first surface 1 a , and the surface of the substrate 1 close to the second functional board 20 is the second surface 1 b .

Exemplarily, the substrate 1 includes at least one substrate 11 and multiple second conductive layers 12, the substrate 11 and the second conductive layers 12 are alternately stacked, and the second conductive layers are respectively disposed on both sides of the substrate. That is, the adapter board 30 can be a single-layer board or a multi-layer board.

For example, referring to FIG. 7 and FIG. 9 to FIG. 14 , the substrate 1 includes a substrate 11 and two second conductive layers 12 disposed on both sides of the substrate 11 .

Or, for example, referring to FIG. 8 , the substrate 1 includes two substrates 11 and three second conductive layers 12 alternately stacked with the substrates 11 .

5 , on the same side of the substrate 11 , the second conductive layer 12 is located on a side of the first conductive portion 21 close to the substrate 11 , and the second conductive layer 12 overlaps the first conductive portion 21 .

Exemplarily, referring to Fig. 5 , the surface of the substrate 1 is provided with wiring L. Exemplarily, the wiring L is provided on both the first surface 1a and the second surface 1b of the substrate 1.

5 , interconnection between pads T corresponding to some through holes K can be achieved through routing L, so that after the adapter board 30 is electrically connected to the functional board (the first functional board 10 and the second functional board 20), interconnection between multiple electronic devices 200 electrically connected to the pads T can be achieved.

Exemplarily, when the substrate 1 includes a substrate 11 and a second conductive layer 12 , the trace L is formed by etching the second conductive layer 12 .

For example, referring to Figure 5, on the same side of the substrate 11, the second conductive layer 12 overlaps with the trace L formed after etching the first conductive part 21, so that the traces on both sides of the substrate 11 can be electrically connected through the first conductive layer 2, so as to ultimately achieve electrical connection between the first functional board 10 and the second functional board 20.

7 to 14 , the first conductive layer 2 includes two first conductive portions 21 and one second conductive portion 22 . The two first conductive portions 21 are respectively disposed on the first surface 1 a and the second surface 1 b of the substrate 1 , and the second conductive portion 22 covers the inner wall of the through hole K and is connected to the two first conductive portions 21 .

It is worth noting that the adapter board 30 may include a plurality of first conductive layers 2 , and the plurality of through holes K are disposed in a one-to-one correspondence with the plurality of first conductive layers 2 .

5 , the multiple first conductive layers 2 are disconnected from each other. For example, the multiple first conductive layers 2 can be separated by etching.

Exemplarily, the material of the first conductive layer 2 may include copper.

Exemplarily, the first conductive portion 21 and the second conductive portion 22 are integrally provided. For example, the first conductive layer 2 can be plated on the first surface 1a and the second surface 1b of the substrate 1 and the inner wall of the through hole K by electroplating.

Exemplarily, referring to FIG. 5 , the first conductive portion 21 is in a ring shape disposed around the through hole K. As shown in FIG.

Exemplarily, referring to FIG5 , the first conductive portion 21 is in electrical contact with the trace L arranged on the first surface 1a and the second surface 1b of the substrate 1. For example, among the two first conductive portions 21 electrically connected to the same second conductive portion 22, one is in electrical contact with the trace L arranged on the first surface 1a of the substrate 1, and the other is in electrical contact with the trace L arranged on the second surface 1b of the substrate 1, so that the trace L arranged on the first surface 1a and the second surface 1b of the substrate 1 can be connected through the second conductive portion 22 located in the through hole K, so that the first functional board 10 and the second functional board 20 arranged on both sides of the adapter board 30 can be electrically connected.

7 to 14 , at least a portion of the conductive structure 3 is filled in the through hole K and is in contact with the second conductive portion 22 .

Exemplarily, the material of the conductive structure 3 may include one or more of tin, silver or copper. For example, the material of the conductive structure 3 includes only tin, or only copper, or only silver. Alternatively, the material of the conductive structure 3 may be an alloy of tin, silver and copper. Alternatively, exemplarily, the material of the conductive structure 3 may also include lead.

Exemplarily, the conductive structure 3 can be filled in the through hole K by planting a ball. For example, a solder ball is placed above the through hole K, and then heated to melt a portion of the solder ball and flow into the through hole K, and then cured to obtain the conductive structure 3 filling the through hole K.

For example, the conductive structure 3 may be filled after the plurality of first conductive layers 2 are spaced apart, so that the size of the first conductive portion 21 may be precisely controlled without blocking the through hole K, which is beneficial for accurately controlling the size of the pad T finally formed.

It is worth noting that the adapter board 30 may include a plurality of conductive structures 3 , and the plurality of through holes K are arranged in a one-to-one correspondence with the plurality of conductive structures 3 .

15 , one end of the conductive structure 3 is electrically connected to the first functional board 10 , and the other end of the conductive structure 3 is electrically connected to the second functional board 20 .

That is, one end and the other end of the conductive structure 3 can serve as at least a portion of the pad T to be welded to the first functional board 10 and the second functional board 20 .

For example, referring to FIG. 7 to FIG. 10 and FIG. 13 , the end of the conductive structure 3 and the first conductive portion 21 on the same surface of the substrate 1 are At least part of them together form the pad T, that is, the end of the conductive structure 3 and the first conductive portion 21 are both welded to the first functional board 10 and the second functional board 20 .

Or, for example, referring to Figures 11, 12, and 14, when the conductive structure 3 completely covers the first conductive portion 21, the end of the conductive structure 3 located on the first surface 1a of the substrate 1 serves as a soldering pad T, which is welded to the first functional board 10; the end of the conductive structure 3 located on the second surface 1b of the substrate 1 serves as another soldering pad T, which is welded to the second functional board 20.

It can be understood that the end of the conductive structure 3 is one of the two ends of the conductive structure 3 in the thickness direction of the substrate 1 .

For example, referring to Figure 15, when the surface of the substrate 1 close to the first functional board 10 is the first surface 1a, and the surface of the substrate 1 close to the second functional board 20 is the second surface 1b, one end of the conductive structure 3 close to the first surface 1a is electrically connected to the first functional board 10, and one end of the conductive structure 3 close to the second surface 1b is electrically connected to the second functional board 20.

In the circuit board 100 provided in the embodiment of the present application, by providing a conductive structure 3 to fill the through hole K, on the one hand, it is possible to avoid using a resin plugging process and subsequent processes such as polishing the resin, thereby simplifying the process and reducing the difficulty of the process.

On the other hand, by providing the conductive structure 3, the electrical connection between the adapter board 30 and the functional board (the first functional board 10 and the second functional board 20) can be realized without plating the auxiliary conductive layer 4' (see FIG. 6), thereby simplifying the structure of the adapter board 30.

At the same time, since there is no need to plate the auxiliary conductive layer 4' as the pad T, the adapter board 30 in the embodiment of the present application can define the pad T area before filling the through hole K. For example, the first conductive layer 2 is etched to form the first conductive portion 21, and the area where the first conductive portion 21 is located is the pad T area. When etching to form the first conductive portion 21, the through hole K is not blocked, and the through hole K can be accurately positioned. That is, it can be etched according to the ideal size value of the pad T (that is, the minimum size value of the pad T that can meet the welding requirements of the adapter board 30 and the functional board) without reserving an error value. The size of the pad T prepared in the present application is smaller than the size of the pad T' (see Figure 6) in the related art, saving the design space of the adapter board 30. The saved design space can be used to set other structures, such as setting more pads T, or arranging more wiring, etc., thereby improving the space utilization of the adapter board 30.

In some embodiments, as shown in FIG. 7 , in the axial direction Li of the through hole K, two ends of the conductive structure 3 protrude from the surface of the two first conductive portions 21 away from the substrate 1 .

Solder paste is applied between the pads T of the first functional board 10 and the adapter board 30, and solder paste is applied between the pads T of the second functional board 20 and the adapter board 30, and the adapter board 30 is welded to the functional board (the first functional board 10 or the second functional board 20) by reflow soldering. During the welding process, the solder paste between the functional board and the adapter board 30 has a certain fluidity. Under the extrusion of the functional board and the adapter board 30, the solder paste corresponding to the two adjacent pads T will flow along the board surface (for example, the surface of the adapter board 30 on the side close to the functional board) so as to approach each other or even contact each other, that is, a bridging problem occurs, resulting in problems such as short circuit or failure of the circuit board.

By arranging the two ends of the conductive structure 3 to protrude from the two first conductive parts 21 away from the surface of the substrate 1, a certain space is provided between the board surfaces of the functional board and the adapter board 30 under the support of the protruding parts of the conductive structure 3, that is, the placement space of the solder paste is expanded, and the squeezing force of the functional board and the adapter board 30 on the solder paste is reduced, thereby avoiding the problem of bridging caused by excessive squeezing of the board surfaces of the functional board and the adapter board 30 on the solder paste, thereby effectively improving the performance of the circuit board.

Exemplarily, as shown in FIG7 and FIG8 , the surface of the protruding portion of the conductive structure 3 is a curved surface, and the curved surface is bent toward the substrate, so that the surface of the protruding portion of the conductive structure 3 has a smooth arc.

By setting the surface of the protruding part of the conductive structure 3 to be a curved surface, the solder paste can fully contact the conductive structure 3 of the adapter board 30 during the welding process of the functional board and the adapter board 30, thereby avoiding the problem of residual bubbles between the solder paste and the conductive structure 3 due to the irregular surface of the part of the conductive structure 3 that is used to contact the solder paste, which can easily cause cold soldering.

For example, the surface of the protruding portion of the conductive structure 3 may be made into a curved surface through subsequent mechanical processing, or the conductive structure 3 may be naturally formed into a curved surface under the action of surface tension during the preparation process.

For example, the surface of the protruding portion of the conductive structure 3 and the surface of the first conductive portion 21 may intersect at approximately an obtuse angle, thereby avoiding the problem of residual bubbles due to insufficient contact of the solder paste at the intersection of the conductive structure 3 and the first conductive portion 21 during the welding process between the functional board and the adapter board 30, leading to the problem of cold solder joints.

Exemplarily, as shown in FIG. 7 , along the axial direction Li of the through hole K, a maximum distance D1 between the protruding portion of the conductive structure 3 and the surface of the first conductive portion 21 away from the substrate 1 is 10 μm to 100 μm.

Exemplarily, referring to Figure 7, when the surface of the protruding portion of the conductive structure 3 is a curved surface and the curved surface is bent toward the substrate, the maximum distance D1 between the protruding portion of the conductive structure 3 and the surface of the first conductive portion 21 away from the substrate 1 can be the distance between the highest point of the protruding portion of the conductive structure 3 and the surface of the first conductive portion 21 away from the substrate 1.

For example, the maximum distance D1 may be 10 μm to 30 μm, 25 μm to 60 μm, 43.5 μm to 75 μm, 50.12 μm to 89.578 μm, or 80 μm to 100 μm. For example, the maximum distance D1 may be 10 μm, 23 μm, 45.8 μm, 78.48 μm, or 100 μm.

By setting the highest point of the protruding portion of the conductive structure 3 to be 10 μm to 100 μm away from the surface of the first conductive portion 21 away from the substrate 1 , the solder joint problem caused by the extrusion between the functional board and the adapter board 30 can be effectively avoided.

In some embodiments, as shown in FIG. 9 , in the axial direction Li of the through hole K, two ends of the conductive structure 3 are recessed relative to the two first conductive portions 21 away from the surface of the substrate 1 .

By setting the two ends of the conductive structure 3 to be recessed relative to the two first conductive parts 21 and away from the surface of the substrate 1, the placement space of the solder paste can be expanded during the welding process of the functional board and the adapter board 30, and the squeezing force of the functional board and the adapter board 30 on the solder paste can be reduced, thereby avoiding the problem of bridging caused by excessive squeezing of the solder paste by the board surfaces of the functional board and the adapter board 30, thereby effectively improving the performance of the circuit board.

9 , the two end surfaces of the conductive structure 3 are curved surfaces, which are bent away from the substrate 1. That is, the surface of the concave portion of the conductive structure 3 is a curved surface, so that the surface of the conductive structure 3 for functional board welding has a smooth arc.

By setting the surface of the recessed part of the conductive structure 3 to be a curved surface, the solder paste can fully contact the conductive structure 3 of the adapter board 30 during the welding process of the functional board and the adapter board 30, thereby avoiding the problem of residual bubbles between the solder paste and the conductive structure 3 due to the irregular surface of the part of the conductive structure 3 that is used to contact the solder paste, which can easily cause cold soldering.

For example, the surface of the recessed portion of the conductive structure 3 may be made into a curved surface through subsequent mechanical processing.

For example, when the surface of the end of the conductive structure 3 intersects with the second conductive part 22, the angle of intersection between the two can be roughly an obtuse angle. This can also avoid the problem of residual bubbles due to insufficient contact between the solder paste at the intersection of the conductive structure 3 and the second conductive part 22 during the welding process between the functional board and the adapter board 30, leading to the problem of cold soldering.

Exemplarily, as shown in FIG. 9 , along the axial direction Li of the through hole K, a maximum distance D2 between the recessed portion of the conductive structure 3 and the surface of the first conductive portion 21 away from the substrate 1 is 10 μm to 100 μm.

Exemplarily, referring to FIG. 9 , the maximum distance D2 between the recessed portion of the conductive structure 3 and the surface of the first conductive portion 21 away from the substrate 1 may be the distance between the lowest point of the recessed portion of the conductive structure 3 and the surface of the first conductive portion 21 away from the substrate 1 .

For example, the maximum distance D2 may be 10 μm to 30 μm, 25 μm to 60 μm, 43.5 μm to 75 μm, 50.12 μm to 89.578 μm, or 80 μm to 100 μm. For example, the maximum distance D2 may be 10 μm, 23 μm, 45.8 μm, 78.48 μm, or 100 μm.

By setting the lowest point of the recessed portion of the conductive structure 3 to be 10 μm to 100 μm away from the surface of the first conductive portion 21 away from the substrate 1 , the solder joint problem caused by the extrusion between the functional board and the adapter board 30 can be effectively avoided.

In some embodiments, as shown in FIG10 , on the same surface of the substrate 1, the end surface of the conductive structure 3 is flush with the surface of the first conductive portion 21 away from the substrate 1. That is, the surface of the pad T is made flat, which improves the reliability of welding between the adapter board 30 and the functional board (the first functional board 10 or the second functional board 20), thereby improving the stability of the circuit board 100 structure.

In some embodiments, as shown in FIGS. 11 to 14 , the conductive structure 3 includes a main body 31 and two sub-parts 32 disposed at two ends of the main body 31 and connected to the main body 31 .

11 , 12 , 13 and 14 , the main body 31 is filled in the through hole K. As shown in FIG.

Exemplarily, the main body 31 and the two sub-parts 32 are integrally formed. For example, the conductive structure 3 is filled by solder ball implantation: a solder ball is placed on the through hole K plated with the first conductive layer 2, and the solder ball is heated so that the solder ball melts and flows to fill the through hole K to form the main body 31. The flowing solder ball material will also extend along the first conductive part 21 of the first conductive layer 2 under the wetting characteristics of the fluid to form the sub-part 32.

11 to 14 , on the same surface of the substrate 1 , two sub-portions 32 cover at least a portion of the first conductive portion 21 .

In some embodiments, as shown in FIGS. 11 and 12 , the sub-portion 32 entirely covers the first conductive portion 21 .

The two sub-parts 32 are electrically connected to the first functional board 10 and the second functional board 20, respectively. Referring to FIG. 11 and FIG. 12, when the two sub-parts 32 completely cover the first conductive part 21, the two sub-parts 32 serve as two ends of the conductive structure 3 in the thickness direction of the substrate 1, and the two sub-parts 32 form the pads T of the adapter board 30 and are electrically connected to the first functional board 10 and the second functional board 20.

By setting the sub-portion 32 of the conductive structure 3 to completely cover the first conductive portion 21, the surface of the pad T is made of the material of the conductive structure 3, which improves the uniformity of the material of the pad T, thereby improving the reliability of welding the pad T and the functional board; The sub-portion 32 of the electrical structure 3 completely covers the first conductive portion 21, so that the surface of the pad T is complete and smooth, avoiding bubbles remaining on the surface of the pad T after solder paste coating due to the uneven surface of the pad T, thereby further improving the reliability of welding between the adapter board 30 and the functional board.

For example, referring to FIG. 11 , the sub-portion 32 covering the first conductive portion 21 may be raised in a direction away from the substrate 1. Thus, under the support of the raised portion of the sub-portion 32, a certain space may be provided between the adapter board 30 and the functional board, that is, the placement space of the solder paste is expanded, and the extrusion force of the functional board and the adapter board 30 on the solder paste is reduced, thereby avoiding the problem of solder bridging caused by excessive extrusion of the solder paste by the board surfaces of the functional board and the adapter board 30, and effectively improving the performance of the circuit board.

For example, referring to Fig. 11, the surface of the sub-portion 32 covering the first conductive portion 21 is curved. The surface of the pad T can be kept intact and smooth, thereby improving the reliability of welding between the adapter board 30 and the functional board, and also avoiding the problem of solder jointing caused by excessive extrusion of the solder paste between the functional board and the adapter board 30, thereby improving the performance of the circuit board.

Exemplarily, referring to FIG. 12 , the surface of the sub-portion 32 covering the first conductive portion 21 is parallel to the surface of the substrate 1 , thereby making the surface of the pad T flat, improving the reliability of welding between the adapter board 30 and the functional board, and thus improving the stability of the circuit board 100 structure.

In some embodiments, as shown in FIG13 , the main body portion 31 is filled in the through hole K. On the same surface of the substrate 1 , the sub-portion 32 may cover a portion of the first conductive portion 21 .

13 , the pad T includes a sub-portion 32 and a portion of the first conductive portion 21 not covered by the sub-portion 32 .

The material of the first conductive part 21 is copper, and the material of the conductive structure 3 may include tin. Compared with the adapter board 30' shown in Figure 7, in this embodiment, the area of the sub-part 32 covering the first conductive part 21 is designed to increase the proportion of the material of the conductive structure 3 in the pad T, so that when the adapter board 30 is soldered with the functional board through solder paste, the contact area between the solder paste and the conductive structure 3 having tin material is increased, which can also improve the reliability of welding between the adapter board 30 and the functional board to a certain extent.

5 and 14 , the circuit board 100 further includes two solder resist layers 4, which are disposed on the first surface 1a and the second surface 1b of the substrate 1. On the same surface of the substrate 1, at least part of the solder resist layer 4 is located between two adjacent first conductive portions 21.

For example, the material of the solder resist layer 4 may include an insulating material such as polyimide or polyethylene terephthalate.

By arranging at least a portion of the solder resist layer 4 between two adjacent first conductive parts 21 on the same surface of the substrate 1, it is possible to further prevent the solder paste on the pads T corresponding to the two adjacent first conductive parts 21 from flowing close to each other under the squeezing action of the adapter board 30 and the functional board during the soldering of the adapter board 30 and the functional board using solder paste, thereby preventing the problem of solder bridging.

It can be seen from the above-mentioned multiple embodiments that in the circuit board 100 provided in the embodiment of the present application, by providing the conductive structure 3 to be filled in the through hole K, the design space of the adapter board 30 can be saved. The saved design space can be fully utilized, for example, the aperture of the through hole K can be enlarged by utilizing the saved space, thereby reducing the difficulty of preparing the through hole K, or the saved design space can be cut off to realize the miniaturized design of the adapter board 30.

In some embodiments, referring to FIG11 , the aperture D3 of the through hole K is 150 μm to 250 μm. For example, the aperture D3 of the through hole K may be 180 μm to 200 μm. For example, the aperture D3 of the through hole K may be 150 μm, 168 μm, 180.5 μm, 193.43 μm or 200 μm.

It should be noted that the present application only takes the embodiment in FIG. 11 as an example to exemplarily illustrate the aperture D3 of the through hole K, and other embodiments may also be applicable to the limitation on the aperture D3 of the through hole K herein.

In order to avoid the problem of solder joints during the welding process between the adapter board 30 and the functional board, a certain distance needs to be maintained between adjacent pads T on the adapter board 30 .

In the related art, referring to FIG6 , due to the use of resin plugging technology, resin will remain on the surface of the first conductive layer 2’ away from the substrate 1’, resulting in poor conductivity between the functional board and the adapter board 30’. Therefore, it is necessary to plate an auxiliary conductive layer 4’ on the surface of the first conductive layer 2’ to improve the conductivity. However, the auxiliary conductive layer 4’ will block the through hole K’. When positioning the through hole K’ and forming a pad T’ on the through hole K’, in order to ensure that the formed pad T’ smoothly covers the through hole K’, the pad T’ needs to be larger in size.

In the adapter board 30 provided in the embodiment of the present application, since the conductive structure 3 is used to fill the through hole K, the conductivity between the functional board and the adapter board 30 is guaranteed. Therefore, there is no need to plate the auxiliary conductive layer 4' (see Figure 6), and the through hole K will not be blocked. At the same time, without the need to plate the auxiliary conductive layer 4', the first conductive layer 2 can be patterned (i.e., the process of forming the first conductive portion 21 and defining the area of the pad T), and then the conductive structure 3 can be filled. Therefore, when forming the pad T, the through hole K can be accurately positioned, so the size of the pad T can be reduced, or the size of the pad T can be compared with the size of the pad T' in the related art. While maintaining consistency, the aperture of the through hole K in the adapter plate 30 provided in the embodiment of the present application can be increased.

For example, in the related art, when the hole spacing between adjacent through holes K’ is limited to 500μm (that is, the spacing between adjacent pads T’ is limited), the aperture of through hole K’ can only be 150μm or less to ensure that pad T’ can cover through hole K’, while in the present application, when the hole spacing between adjacent through holes K is limited to 500μm and the size of pad T remains unchanged, the aperture of through hole K can meet the requirement that pad T covers through hole K even if it is made into 200μm.

To sum up, in the circuit board 100 provided in the embodiment of the present application, the saved design space of the adapter plate 30 can be used to increase the aperture of the through hole K. The preparation difficulty of the through hole K with a large aperture is lower, and the probability of damage is lower. At the same time, the cost of a large-size drill bit is lower, and the preparation cost of the adapter plate 30 of the through hole K with a large aperture can be reduced.

In some embodiments, referring to Fig. 12 , the distance D4 between two adjacent through holes K is greater than or equal to 400 μm. For example, the distance D4 is 400 μm, 407 μm, 431.4 μm, 450 μm or 500 μm.

In the related art, in order to ensure that the formed pad T' (see FIG. 6) smoothly covers the through hole K' (see FIG. 6), the size of the pad T' is relatively large. In the adapter board 30 provided in the embodiment of the present application, since the through hole can be accurately positioned, the size of the pad T can be reduced. After reducing the size of the pad T, more space is saved between adjacent pads T, that is, there is still space to shorten the spacing between adjacent pads T.

For example, in the related art, the hole spacing between adjacent through holes K' is limited to 500μm to avoid the bridging problem. In the present application, the size of the pad T is reduced, and the hole spacing between adjacent through holes K is reduced to 400μm to ensure that the spacing between the pads T meets the requirements.

To sum up, in the circuit board 100 provided in the embodiment of the present application, the hole spacing between adjacent through holes K can be reduced, thereby saving more design space. The saved design space can be used to arrange traces L, or to arrange more pads T or devices, or the saved space can be cut off to further realize the miniaturization design of the adapter board 30 and even the circuit board 100.

After the adapter plate 30 is prepared, the first functional board 10 and the second functional board 20 need to be welded to both sides of the adapter plate 30 in sequence.

For example, the conductive structure 3 can be melted and filled into the through hole K by means of reflow soldering, and the adapter board 30 and the functional board (the first functional board 10 and the second functional board 20) can also be welded by means of reflow soldering.

FIG15 is a cross-sectional view of a circuit board 100 provided in an embodiment of the present application. As shown in FIG15, in some embodiments, the circuit board 100 further includes a first connection structure 40 and a second connection structure 50. The first connection structure 40 is disposed between the first functional board 10 and the adapter board 30, and one end of the conductive structure 3 is welded to the first functional board 10 through the first connection structure 40. The second connection structure 50 is disposed between the second functional board 20 and the adapter board 30, and the other end of the conductive structure 3 is welded to the second functional board 20 through the second connection structure 50.

Exemplarily, the material of the first connection structure 40 and the second connection structure 50 may include one or more of tin, silver, bismuth, or copper.

Exemplarily, the first connecting structure 40 and the second connecting structure 50 are both prepared by reflow soldering of solder paste. For example, the solder paste is coated on the pad T of the adapter board 30. After the functional board (the first functional board 10 or the second functional board 20) is fixed on one side of the adapter board 30, the adapter board 30 and the functional board are reflow soldered together, and finally the first connecting structure 40 or the second connecting structure 50 located between the adapter board 30 and the functional board is obtained.

The melting point of the conductive structure 3 is greater than the melting point of the first connection structure 40 and greater than the melting point of the second connection structure, so as to avoid the conductive structure from melting in the high temperature environment of the adapter board and the functional board (the first functional board and the second functional board) during the welding process, thereby avoiding damage to the structure of the adapter board.

The melting point of the first connection structure 40 is not equal to the melting point of the second connection structure 50 .

For example, when the first functional board 10 and the adapter board 30 are first welded through the first connecting structure 40 and then the second functional board 20 and the adapter board 30 are welded through the second connecting structure 50, the melting point of the first connecting structure 40 is greater than the melting point of the second connecting structure 50, thereby preventing the high temperature environment during the welding process of the second functional board 20 and the adapter board 30 from melting the welded first connecting structure 40 and affecting the firmness between the first functional board 10 and the adapter board 30.

Alternatively, for example, when the second functional board 20 is first welded to the adapter board 30 through the second connecting structure 50, and then the first functional board 10 is welded to the adapter board 30 through the first connecting structure 40, the melting point of the second connecting structure 50 is greater than that of the first connecting structure 40. The melting point of the structure 40 can prevent the first functional board 10 and the adapter board 30 from being melted by the high temperature environment during the welding process, thereby avoiding affecting the firmness between the second functional board 20 and the adapter board 30.

Exemplarily, the melting point of the conductive structure 3 may be 245°C.

For example, the melting point of the first connection structure 40 may be 217°C, and the melting point of the second connection structure 50 may be 138°C.

Alternatively, illustratively, the melting point of the first connection structure 40 may be 138° C., and the melting point of the second connection structure 50 may be 217° C.

Exemplarily, the preparation temperature of the conductive structure 3 may be greater than or equal to 245°C.

Exemplarily, the preparation temperature of the first connection structure 40 may be greater than or equal to 217°C and less than 245°C. For example, it may be 220°C to 240°C. For example, it may be 220°C, 235°C, 237.4°C or 240°C. The preparation temperature of the second connection structure 50 may be greater than or equal to 138°C and less than 217°C. For example, it may be 140°C to 200°C. For example, it may be 140°C, 163.5°C, 190.36°C or 200°C.

Alternatively, illustratively, the preparation temperature of the second connection structure 50 may be greater than or equal to 217°C and less than 245°C. For example, it may be 220°C to 240°C. For example, it may be 220°C, 235°C, 237.4°C, or 240°C. The preparation temperature of the first connection structure 40 may be greater than or equal to 138°C and less than 217°C. For example, it may be 140°C to 200°C. For example, it may be 140°C, 163.5°C, 190.36°C, or 200°C.

In the related art, due to the use of resin plugging technology, during the preparation of the adapter plate 30', the resin needs to be subjected to multiple mechanical processing steps such as grinding and cutting, and the preparation process is cumbersome. In addition, after the resin plugging, resin will remain on the surface of the adapter plate 30', resulting in poor conductivity between the functional board and the adapter plate 30', so it is necessary to plate the auxiliary conductive layer 4' to improve the conductivity between the functional board and the adapter plate 30'. After the auxiliary conductive layer 4' is plated, the auxiliary conductive layer 4' blocks the through hole K', reducing the accuracy of positioning the through hole K'. When positioning the through hole K' and forming the pad T' on the through hole K', it is necessary to prepare the pad T' according to the correction value (the sum of the ideal value and the error value), that is, in order to eliminate the positioning error, it is necessary to expand the actual size value on the basis of the ideal size value of the pad T', so as to avoid the situation where the pad T' cannot cover the through hole K' due to the positioning error. Therefore, the size of the pad T' formed by the adapter plate 30' in the related art is large, which makes the utilization rate of the design space of the adapter plate 30' low.

In order to solve the aforementioned problems, simplify the preparation process of the adapter plate 30 , and optimize the design space of the adapter plate 30 , another aspect of an embodiment of the present application provides a method for preparing a circuit board 100 .

FIG16 is a flow chart of preparing a circuit board provided in an embodiment of the present application, and FIG17 is a cross-sectional view of each preparation step in FIG16 .

As shown in Figures 16 and 17, the preparation method includes:

S1: Provide a substrate 1. As shown in FIG. 17(A) , the substrate 1 includes a first surface 1 a and a second surface 1 b that are opposite to each other.

Exemplarily, step S1 includes: providing a substrate 11 , plating a second conductive layer 12 , and patterning the second conductive layer 12 to form a trace L.

S2: As shown in FIG. 17(B) , a through hole K penetrating the substrate 1 is formed.

Exemplarily, a dedicated drilling tool may be used to prepare the through hole K.

Illustratively, the drill bit used in the present application may be a drill bit of 150 μm to 250 μm, for example, a 200 mm drill bit may be used.

S3: As shown in (C) of FIG. 17 , the first conductive layer 2 is plated in the through hole K and on the first surface 1 a and the second surface 1 b .

Exemplarily, the first conductive layer 2 is electroplated to electrically connect the traces L on the first surface 1a and the second surface 1b of the substrate 1, so as to facilitate subsequent connection between the first functional board 10 and the second functional board 20.

S4: As shown in (D) of FIG. 17 , the first conductive layer 2 is etched to form two first conductive portions 21 located on the first surface 1 a and the second surface 1 b .

Exemplarily, the first conductive portion 21 formed after etching the first conductive layer 2 is the area where the pad T is located. In this step, the through hole K is in an exposed state, so the through hole K can be accurately positioned, so that the pad T can be formed according to an ideal size. Compared with the related art, the pad T of the adapter board 30 in the present application is smaller in size, which saves the design space of the adapter board 30.

S5 : As shown in FIG. 17 (E) , the conductive structure 3 is filled in the through hole K plated with the first conductive layer 2 .

Illustratively, after performing step S4 and before performing step S5, the method may further include: coating a protective layer on the surface of the substrate 1 plated with the first conductive layer 2 and the inner wall of the through hole K to prevent the first conductive layer 2 from being oxidized.

Exemplarily, after performing step S5, the method may further include: coating a solder resist layer 4 (see FIGS. 5 and 14 ) so that at least a portion of the solder resist layer 4 is located between two adjacent first conductive portions 21, thereby further avoiding the two adjacent first conductive portions 21 from contacting each other. The solder paste on the corresponding pad T flows close to each other under the squeezing effect of the transfer board 30 and the functional board, resulting in the problem of solder joints.

FIG. 18 is another preparation flow chart of a circuit board provided in an embodiment of the present application.

In some embodiments, as shown in FIG. 18 , step S5: filling the conductive structure 3 in the through hole K plated with the first conductive layer 2 comprises:

S51: placing a solder ball on the through hole K plated with the first conductive layer 2;

S52: heating the solder ball so that the solder ball melts and fills the through hole K;

S53: solidifying the melted solder balls to form a conductive structure 3.

That is, the conductive structure 3 can be prepared by solder ball implantation.

Exemplarily, the conductive structure 3 may be prepared by using materials such as copper balls and silver balls.

Exemplarily, the conductive structure 3 may be prepared by other methods such as steel screen printing.

Exemplarily, in step S52 , after the solder ball melts, it flows along the surface of the first conductive portion 21 , and finally covers the portion of the first conductive portion 21 and forms the sub-portion 32 of the conductive structure 3 after solidification.

Exemplarily, the area of the sub-portion 32 covering the first conductive portion 21 can be controlled by controlling the ratio of the volume of the solder ball to the volume of the through hole K. For example, a larger volume of solder ball will form a larger amount of fluid after melting, which can completely cover the first conductive portion 21.

For example, by controlling the ratio of the volume of the solder ball to the volume of the through hole K, it is also possible to control the protrusion, depression or flushness of the end of the conductive structure 3 .

For example, the ratio of the volume of the solder ball to the volume of the through hole K may be 1.4 to 4.8. For example, when the aperture of the through hole K is 150 μm, the depth is 850 μm, and the diameter of the solder ball is 350 μm, the end of the conductive structure 3 formed by the solder ball may be convex relative to the first conductive portion 21. For example, when the aperture of the through hole K is 150 μm, the depth is 850 μm, and the diameter of the solder ball is 300 μm, the end of the conductive structure 3 formed by the solder ball may be concave relative to the first conductive portion 21.

Exemplarily, the protrusion, depression or flushness of the end of the conductive structure 3 can also be controlled by other means, such as mechanical processing.

FIG19 is another preparation flow chart of a circuit board provided in an embodiment of the present application, and FIG20 is a cross-sectional view of each preparation step in FIG19 .

In some embodiments, as shown in FIG. 19 and FIG. 20 , after step S5: filling the conductive structure 3 in the through hole K plated with the first conductive layer 2 , the method further includes:

S6: welding the first functional board 10 to one end of the conductive structure 3 at a first preset temperature.

Exemplarily, step S6 includes: referring to FIG. 20 (A), coating the first connection structure 40 on the surface of the adapter plate 30 ; referring to FIG. 20 (B), welding the first functional board 10 and the adapter plate 30 through the first connection structure 40 .

S7: welding the second functional board 20 to the other end of the conductive structure 3 at a second preset temperature.

Exemplarily, step S7 includes: referring to (C) in FIG. 20 , coating the second connection structure 50 on the surface of the adapter plate 30 ; referring to (D) in FIG. 20 , welding the second functional board 20 and the adapter plate 30 through the second connection structure 50 .

Exemplarily, the material of the first connection structure 40 and the second connection structure 50 includes tin.

Exemplarily, step S6 and step S7 may be replaced. For example, referring to FIG. 20 , step S6 may be performed first and then step S7. The embodiment of the present application is not limited to this.

The heating temperature of the solder ball is greater than the first preset temperature and greater than the second preset temperature, so as to avoid the welding temperature during the welding process of the first functional board 10 and the adapter board 30 from melting the conductive structure 3 and damaging the adapter board 30, and also avoid the welding temperature during the welding process of the second functional board 20 and the adapter board 30 from melting the conductive structure 3 and damaging the structure of the adapter board 30.

The first preset temperature is not equal to the second preset temperature.

Exemplarily, when step S6 is performed first and then step S7, the first preset temperature is greater than the second preset temperature. At this time, the welding temperature during the welding process of the second functional board 20 and the adapter board 30 can be avoided, and the already welded solder structure between the first functional board 10 and the adapter board 30 can be melted to avoid affecting the welding firmness of the first functional board 10 and the adapter board 30.

Or, exemplarily, when step S7 is performed first and then step S6, the first preset temperature is lower than the second preset temperature. At this time, the welding temperature during the welding process of the first functional board 10 and the adapter board 30 can be avoided, and the already welded solder structure between the second functional board 20 and the adapter board 30 can be melted to avoid affecting the welding firmness of the second functional board 20 and the adapter board 30.

Exemplarily, the heating temperature of the solder ball is greater than or equal to the melting point of the solder ball, and the first preset temperature is greater than or equal to the first connection structure 40, and the second preset temperature is greater than or equal to the melting point of the second connection structure 50.

The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that a person skilled in the art can think of within the technical scope disclosed in the present disclosure should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

A circuit board, characterized in that it comprises: an adapter board, and a first function board and a second function board respectively arranged on both sides of the adapter board, wherein the first function board and the second function board are electrically connected through the adapter board;

Wherein, the adapter plate comprises:

A substrate having a through hole; the substrate comprises a first surface and a second surface opposite to each other;

A first conductive layer, comprising two first conductive parts and one second conductive part; the two first conductive parts are arranged on the first surface and the second surface of the substrate, and the second conductive part covers the inner wall of the through hole and is connected to the two first conductive parts;

A conductive structure, at least a portion of which is filled in the through hole and in contact with the second conductive portion; one end of the conductive structure is electrically connected to the first functional board, and the other end of the conductive structure is electrically connected to the second functional board.
The circuit board according to claim 1 is characterized in that, in the axial direction of the through hole, two ends of the conductive structure protrude from the surface of the two first conductive parts away from the substrate.
The circuit board according to claim 2 is characterized in that the surface of the protruding portion of the conductive structure is a curved surface, and the curved surface is bent toward the substrate.
The circuit board according to claim 2, characterized in that, along the axial direction of the through hole, the maximum distance between the protruding portion of the conductive structure and the surface of the first conductive portion away from the substrate is 10 μm to 100 μm.
The circuit board according to claim 1 is characterized in that, in the axial direction of the through hole, both ends of the conductive structure are recessed relative to the two first conductive parts away from the surface of the substrate.
The circuit board according to claim 5 is characterized in that both end surfaces of the conductive structure are curved surfaces, and the curved surfaces are bent away from the substrate.
The circuit board according to claim 5, characterized in that, along the axial direction of the through hole, the maximum distance between the recessed portion of the conductive structure and the surface of the first conductive portion away from the substrate is 10 μm to 100 μm.
The circuit board according to claim 1, characterized in that the conductive structure comprises a main body portion, and two sub-parts disposed at two ends of the main body portion and connected to the main body portion;

The main body is filled in the through hole; on the same surface of the substrate, the sub-part covers at least part of the first conductive part; and the two sub-parts are electrically connected to the first functional board and the second functional board respectively.
The circuit board according to any one of claims 1 to 8, characterized in that the material of the conductive structure includes one or more of tin, copper and silver.
The circuit board according to any one of claims 1 to 8, characterized in that the aperture of the through hole is 150 μm to 250 μm.
The circuit board according to any one of claims 1 to 8, characterized in that a spacing between two adjacent through holes is greater than or equal to 400 μm.
The circuit board according to any one of claims 1 to 8, further comprising:

A first connection structure is provided between the first functional board and the adapter board, and one end of the conductive structure is welded to the first functional board through the first connection structure;

A second connection structure is provided between the second functional board and the adapter board, and the other end of the conductive structure is welded to the second functional board through the second connection structure;

The melting point of the conductive structure is greater than the melting point of the first connecting structure, and greater than the melting point of the second connecting structure; the melting point of the first connecting structure is not equal to the melting point of the second connecting structure.
The circuit board according to any one of claims 1 to 8, characterized in that the substrate comprises at least one substrate layer and multiple second conductive layers, the substrate and the second conductive layers are alternately stacked, and the second conductive layers are respectively provided on both side surfaces of the substrate;

On the same side of the substrate, the second conductive layer is located on a side of the first conductive portion close to the substrate, and the second conductive layer overlaps the first conductive portion.
The circuit board according to any one of claims 1 to 8, characterized in that it further comprises:

Two solder resist layers are respectively arranged on the first surface and the second surface of the substrate; on the same surface of the substrate, at least part of the solder resist layers is located between two adjacent first conductive parts.
An electronic device, characterized in that it comprises: a plurality of electronic devices, and any one of claims 1 to 14 Circuit boards;

Wherein, the plurality of electronic components are separately arranged on the first functional board and the second functional board.
A method for preparing a circuit board, characterized by comprising:

providing a substrate, the substrate comprising a first surface and a second surface opposite to each other;

forming a through hole penetrating the substrate;

Plating a first conductive layer in the through hole and on the first surface and the second surface;

Etching the first conductive layer to form two first conductive parts located on the first surface and the second surface;

A conductive structure is filled in the through hole plated with the first conductive layer.
The preparation method according to claim 16, characterized in that the step of filling the conductive structure in the through hole plated with the first conductive layer comprises:

placing a solder ball on the through hole plated with the first conductive layer;

Heating the solder ball so that the solder ball melts and fills the through hole;

The melted solder balls are solidified to form the conductive structure.
The preparation method according to claim 17, characterized in that after filling the conductive structure in the through hole plated with the first conductive layer, it also includes:

Welding the first functional board at one end of the conductive structure at a first preset temperature;

Welding the second functional board at the other end of the conductive structure at a second preset temperature;

The heating temperature of the solder ball is greater than the first preset temperature and greater than the second preset temperature; the first preset temperature is not equal to the second preset temperature.