Manufacturing method of circuit board, circuit board and terminal device

Abstract

According to the manufacturing method of the circuit board, in the pressing step, the mode of emitting ultrasonic waves is adopted to cure the adhesive layer so as to bond the adjacent substrates, the mode of curing the adhesive layer through high-temperature melting of the adhesive layer and the mode of curing the adhesive layer through ultrasonic waves are replaced, and the substrates (such as the first substrate and the second substrate) can be prevented from being placed in a high-temperature environment; therefore, the warping phenomenon of the manufactured circuit board is effectively improved; the adhesive layer is cured through ultrasonic waves, the adhesive layer can be cured within several seconds, an additional cooling step is not needed, consumed time is short, and the manufacturing cost is reduced; the glue layer is cured under the action of ultrasonic waves, no obvious glue overflowing phenomenon is generated, and the glue overflowing phenomenon generated in the high-temperature pressing step can be effectively improved. The invention further provides a circuit board and a terminal device.

Description

Technical Field

[0001] The present application relates to the technical field of circuit board manufacturing, and particularly to a method for manufacturing a circuit board, a circuit board, and a terminal device. Background Art

[0002] During the manufacturing process of a circuit board, a lamination step is usually required, that is, the substrates to be laminated and the adhesive layer are placed in a high-temperature environment for baking to melt the colloid. After cooling, the colloid solidifies to bond the substrates. In a high-temperature environment, the substrates expand, and when cooling, the substrates contract, and the substrates are prone to warping. For the lamination of multi-layer substrates, multiple laminations may be required, which further increases the risk of low yield of the manufactured circuit board; moreover, as the thickness of the laminated substrates increases, the baking time increases accordingly, and after baking, a coolant is required for cooling. Therefore, the cost consumed in the manufacturing process is relatively large. Summary of the Invention

[0003] In view of this, it is necessary to provide a method for manufacturing a circuit board that can prevent substrate warping and reduce costs to solve the above problems.

[0004] A method for manufacturing a circuit board includes covering an adhesive layer on the surface of a first substrate; covering a second substrate on the surface of the adhesive layer facing away from the first substrate; placing the first substrate, the adhesive layer, and the second substrate between two pressing plates, pressing the two pressing plates and applying ultrasonic waves to the pressing plates to cure the adhesive layer under the action of the ultrasonic waves.

[0005] In some embodiments, the step of pressing the two pressing plates and applying ultrasonic waves to the pressing plates to cure the adhesive layer under the action of the ultrasonic waves includes: respectively pushing the two pressing plates by cylinders; placing an ultrasonic head that emits the ultrasonic waves on the pressing plates and moving on the pressing plates to cure the adhesive layer.

[0006] In some embodiments, blind holes are formed on the first substrate, and openings are formed on the adhesive layer; in the step of covering the adhesive layer on the surface of the first substrate, the openings communicate with the blind holes.

[0007] In some embodiments, after the adhesive layer is cured, the adhesive layer does not overflow into the openings and / or the blind holes.

[0008] In some embodiments, the adhesive layer includes one of epoxy resin, bismaleimide-triazine, and polyimide.

[0009] In some embodiments, the adhesive layer further contains at least one of dicyandiamide, terephthalic acid, and inorganic hydroxide.

[0010] In some embodiments, the first substrate includes a first dielectric layer, and the material of the first dielectric layer includes one of polyimide and modified polyimide.

[0011] In some embodiments, the second substrate includes a second dielectric layer, and the material of the second dielectric layer includes one of polypropylene, liquid crystal polymer, and polytetrafluoroethylene.

[0012] A circuit board is formed by a circuit board manufacturing method.

[0013] A terminal device, the terminal device includes a circuit board.

[0014] In the circuit board manufacturing method provided by the embodiments of the present application, in the lamination step, ultrasonic waves are emitted to cure the adhesive layer to bond adjacent substrates, instead of curing the adhesive layer by the method of high-temperature melting the adhesive layer. Curing the adhesive layer by ultrasonic waves can avoid placing the substrates (such as the first substrate and the second substrate) in a high-temperature environment, thereby effectively improving the warping phenomenon of the manufactured circuit board; and the present application uses ultrasonic waves to cure the adhesive layer, and the adhesive layer can be cured within a few seconds, and no additional cooling step is required, which takes a short time and reduces the manufacturing cost; the adhesive layer is cured under the action of ultrasonic waves, and no obvious glue overflow phenomenon will occur, which can effectively improve the glue overflow phenomenon generated in the high-temperature lamination step. Description of the Drawings

[0015] Figure 1 It is a cross-sectional schematic diagram of the first substrate provided by the embodiments of the present application.

[0016] Figure 2 It is for Figure 1 The cross-sectional schematic diagram after covering a protective layer on the surface of the first substrate shown.

[0017] Figure 3 It is for Figure 2 The cross-sectional schematic diagram after covering an adhesive layer on the surface of the first substrate shown.

[0018] Figure 4 It is for Figure 3 The cross-sectional schematic diagram after covering a second substrate on the surface of the adhesive layer shown.

[0019] Figure 5 It is for Figure 4 The cross-sectional schematic diagram of setting a pressing plate on the surface of the second substrate shown and emitting ultrasonic waves.

[0020] Figure 6 It is for removing Figure 5 The cross-sectional schematic diagram after removing the pressing plate shown and manufacturing a circuit on the second substrate.

[0021] Figure 7 It is for Figure 6Schematic cross-sectional view of the surface of the second substrate shown, successively covered with an adhesive layer and a third substrate.

[0022] Figure 8 To remove Figure 7 Schematic cross-sectional view of a circuit board obtained after removing the second substrate and the third substrate corresponding to the protective layer shown.

[0023] Main component symbol description

[0024] circuit board 100 first substrate 10 first dielectric layer 11 first circuit layer 13 blind hole 15 protective layer 20 surface treatment layer 21 adhesive layer 30 opening 31 second substrate 40 second dielectric layer 41 copper layer 43 second circuit layer 432 conductive hole 434 laminated board 50 cylinder 51 ultrasonic head 53 third substrate 60 Detailed implementation manners

[0025] In order to more clearly understand the above objects, features and advantages of the present application, the present application will be described in detail below with reference to the drawings and specific implementation manners. It should be noted that, without conflict, the implementation manners of the present application and the features in the implementation manners can be combined with each other. Many specific details are set forth in the following description in order to fully understand the present application. The described implementation manners are only a part of the implementation manners of the present application, rather than all of the implementation manners.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific implementation manners, and are not intended to limit this application. The term "and / or" used herein includes all and any combinations of one or more of the related listed items.

[0027] In the embodiments of the present application, for the convenience of description rather than limiting the present application, the term "connection" used in the patent application specification and claims of the present application is not limited to physical or mechanical connection, whether direct or indirect. "Upper", "lower", "above", "below", "left", "right", etc. are only used to represent relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship also changes accordingly.

[0028] Please refer to Figures 1 to 8 , an embodiment of the present application provides a method for manufacturing a circuit board 100, which may include the following steps:

[0029] Step S1: Please refer to Figure 1 , provide a first substrate 10.

[0030] The first substrate 10 may be a circuit board. For example, it may be a flexible circuit board or a rigid circuit board. In this embodiment, the first substrate 10 is a flexible circuit board. The first substrate 10 may include a first dielectric layer 11 and a first circuit layer 13 located on the surface of the first dielectric layer 11. The number of layers of the first dielectric layer 11 and the first circuit layer 13 may be one or more layers.

[0031] The material of the first dielectric layer 11 may be one of flexible materials such as polyimide (PI), modified polyimide (MPI), etc., or may be selected from hard materials such as polypropylene (PP), liquid crystal polymer (LCP), and polytetrafluoroethylene (PTFE).

[0032] A blind via 15 is formed on the first substrate 10. The blind via 15 penetrates through the first circuit layer 13, and the surface of the first dielectric layer 11 is exposed to the first circuit layer 13.

[0033] Step S2: Refer to Figure 2 , and cover a protective layer 20 on the surface of the first substrate 10.

[0034] In this embodiment, the first substrate 10 is a flexible circuit board, and the area covered by the protective layer 20 may be used as the bending area of the subsequent formed circuit board 100. The protective layer 20 covers the first circuit layer 13 and / or the first dielectric layer 11.

[0035] In some embodiments, the step of covering the protective layer 20 may be omitted accordingly according to the type of the manufactured circuit board 100.

[0036] In some embodiments, before the step of covering the protective layer 20, the manufacturing method further forms a surface treatment layer 21 on a part of the surface of the first circuit layer 13. The surface treatment layer is subsequently used to be exposed on the surface of the protective layer 20, and the surface treatment layer 21 is used to prevent the first circuit layer 13 from oxidation. The material of the surface treatment layer 21 may be gold or nickel.

[0037] Step S3: Refer to Figure 3 , and cover an adhesive layer 30 on the surface of the first substrate 10. The adhesive layer 30 is provided with an opening 31, and the opening 31 communicates with the blind via 15.

[0038] The protective layer 20 may penetrate through the adhesive layer 30.

[0039] The adhesive layer 30 is a prepreg. A prepreg generally includes glass fibers, resin, and additives. The glass fibers are used as reinforcing materials, the resin is impregnated on the glass fibers, and the additives are dispersed in the resin. During the curing process of the prepreg, the resin gradually crosslinks and then becomes solid.

[0040] The resin can be epoxy resin, bismaleimide-triazine, polyimide, etc.; the additives include but are not limited to curing agents, toughening agents, accelerators, and hardeners, etc. In some embodiments, the resin in the prepreg is epoxy resin, the curing agent is dicyandiamide, the toughening agent is terephthalic acid, and the accelerator is inorganic hydroxide.

[0041] Step S4: Please refer to Figure 4 , cover the second substrate 40 on the surface of the adhesive layer 30 facing away from the first substrate 10.

[0042] The second substrate 40 covers the opening 31 and also covers the protective layer 20.

[0043] In this embodiment, the second substrate 40 can be a circuit board or a copper-clad laminate. In this embodiment, the second substrate 40 is a single-sided copper-clad laminate. The second substrate 40 includes a second dielectric layer 41 and a copper layer 43. The copper layer 43 is located on the surface of the second dielectric layer 41 facing away from the first substrate 10. The copper layer 43 is subsequently used to make a circuit layer. The second dielectric layer 41 is selected from one of hard materials such as PP, LCP, and PTFE.

[0044] Among them, the protective layer 20 can penetrate through the second dielectric layer 41 and be connected to the surface of the copper layer 43.

[0045] Step S5: Please refer to Figure 5 , place the first substrate 10, the adhesive layer 30, and the second substrate 40 between two pressing plates 50, press the two pressing plates 50 and apply ultrasonic waves to the pressing plates 50 so that the adhesive layer 30 cures under the action of the ultrasonic waves.

[0046] Specifically, it can include the following steps:

[0047] Step S51: Place two cylinders 51 on one side of the first substrate 10 and the second substrate 40 respectively. The cylinders 51 can be used to push the two pressing plates 50 to move relative to each other to apply pressure to press the first substrate 10, the adhesive layer 30, and the second substrate 40.

[0048] Step S52: Place the ultrasonic head 53 for emitting the ultrasonic waves on the pressing plate 50. The ultrasonic head 53 emits ultrasonic waves and moves on the pressing plate 50 so that the adhesive layer 30 gradually cures.

[0049] When ultrasonic waves act on the bonding plate 50, pass through the first substrate 10 and the second substrate 40 respectively, and propagate towards the colloid, the colloid will absorb the acoustic energy and convert it into heat energy, causing the temperature of the colloid to rise and start to melt. Among them, under the vibration of ultrasonic waves, a cavitation effect occurs in the colloid, that is, the instantaneous high temperature generated by the explosion of extremely small air cavities in the gaps of the colloid causes the temperature inside the colloid to further rise. As the temperature of the colloid rises, the viscosity decreases accordingly, and the colloid will fully fill the gaps between the colloid and the first substrate 10 and between the colloid and the second substrate 40. The curing agent in the colloid causes the colloid to start curing. Among them, the instantaneous high temperature generated by the explosion of extremely small air cavities is different from the high temperature during baking. The range of the high-temperature area of the instantaneous high temperature is small and mainly exists in the colloid, and the influence on the first substrate 10 and the second substrate 40 connected by the colloid is very small; while the range of the high-temperature area during baking is all the substrates and adhesive layers placed in the high-temperature environment, that is, both the substrate and the adhesive layer are in a high-temperature state.

[0050] In addition, the instantaneous high temperature and high pressure generated by the cavitation effect can reduce the surface energy of the particles in the adhesive layer 30, improve the interfacial compatibility between the particles and the polymer, and break up the bonding between the particles, thereby improving the dispersibility of the particles; at the same time, the "explosion" wave generated by cavitation will push the tiny particles in the colloid to move slowly in the colloid with lower viscosity, accelerating the dispersion of the particles in the colloid; the mechanical mass transfer effect generated by the ultrasonic wave acting on the object can make the particles in the colloid enter the vibration state, which will also increase the dispersion of the particles in the colloid. As the resin in the adhesive layer 30 crosslinks to form tight groups, the curing degree of the colloid increases until the adhesive layer 30 is completely cured.

[0051] Among them, through the action of ultrasonic waves, the curing time of the adhesive layer 30 is completed within seconds, and the adhesive layer 30 hardly overflows, that is, it is difficult to overflow into the opening 31 or the blind hole 15 within milliseconds. For substrates with structures such as grooves and blind holes, in the high-temperature pressing step adopted in the related art, it is easy to have glue overflow, causing the excess colloid to overflow into the grooves and blind holes, affecting the performance of the circuit board. If a baffle is used to block it, the requirement for bonding accuracy is extremely high, and the manufacturing process is complex; moreover, the curing time of the adhesive layer 30 is short, and no additional cooling step is required, which can greatly improve the manufacturing efficiency of the circuit board 100 and reduce the production cost; in addition to the adhesive layer 30, the influence of ultrasonic waves on other materials used to manufacture the circuit board 100 is low, and during the curing process of the colloid, no high temperature is generated and the reaction mechanism of the colloid will not be changed, the material of the colloid will not denature, and the influence of the curing process of the colloid on the first substrate 10 and the second substrate 40 is minimized, which can effectively reduce or prevent the expansion, contraction and warping of the first substrate 10 and the second substrate 40 caused by high temperature.

[0052] Step S53: After the adhesive layer 30 is cured, remove the pressing plate 50 to expose the first substrate 10 and the second substrate 40, and the excess heat in the adhesive layer 30 is dissipated to the first substrate 10 and the second substrate 40.

[0053] Due to the instantaneous high temperature generated under the action of ultrasonic waves, the heat generated by ultrasonic waves is less than the heat of high-temperature baking. After the adhesive layer 30 is cured, natural cooling can be achieved without additional cooling steps.

[0054] Step S6: Refer to Figure 6 , perform circuit manufacturing on the second substrate 40 to form the second circuit layer 432 from the copper layer 43.

[0055] In the circuit manufacturing step, conductive vias 434 can also be formed to electrically connect the second circuit layer 432 and the first circuit layer 13.

[0056] When the build-up step is required, steps S3 - S5 are adaptively repeated. For example, in this embodiment, the manufacturing method may further include:

[0057] Step S7: Refer to Figure 7 , cover another adhesive layer 30 on the surface of the second circuit layer 432, and cover a third substrate 60 on the surface of the adhesive layer 30. Use the combined action of the pressing plate 50 and ultrasonic waves to bond the second substrate 40 and the third substrate 60 after the adhesive layer 30 is cured.

[0058] Step S8: Refer to Figure 8 , remove the regions corresponding to the second substrate 40 and the third substrate 60 of the protective layer 20 to expose the protective layer 20, so that the regions corresponding to the protective layer 20 form bending regions.

[0059] The manufacturing method further includes: removing a part of the protective layer 20 to expose the surface treatment layer 21.

[0060] The circuit board 100 manufactured in this embodiment is a rigid-flexible combination board. In other embodiments, a rigid circuit board or a flexible circuit board can also be manufactured. In other embodiments, the manufacturing steps of the circuit board 100 can also be adaptively adjusted according to the requirements of the number of circuit layers.

[0061] The embodiment of the present application further provides a terminal device (not shown in the figure), and the terminal device includes the circuit board 100 manufactured by the above manufacturing method. The terminal device can be a mobile phone, a camera, a drone, a computer, a camera, etc.

[0062] In the method for manufacturing the circuit board 100 provided by the embodiment of the present application, in the lamination step, ultrasonic waves are emitted to cure the adhesive layer 30 to bond adjacent substrates, instead of curing the adhesive layer by means of high-temperature melting of the adhesive layer. Curing the adhesive layer 30 by ultrasonic waves can avoid placing the substrates (such as the first substrate 10 and the second substrate 40) in a high-temperature environment, thereby effectively improving the warping phenomenon of the manufactured circuit board. Moreover, in the present application, the adhesive layer 30 is cured by ultrasonic waves. The adhesive layer 30 can be cured within several seconds, and no additional cooling step is required, which takes a short time and reduces the manufacturing cost. The adhesive layer 30 is cured under the action of ultrasonic waves, and no obvious glue overflow phenomenon will occur, which can effectively improve the glue overflow phenomenon generated in the high-temperature lamination step.

[0063] The above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the above preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for manufacturing a circuit board, characterized in that, comprising: covering an adhesive layer on the surface of a first substrate; covering a second substrate on the surface of the adhesive layer facing away from the first substrate; and placing the first substrate, the adhesive layer, and the second substrate between two pressing plates, pressing the two pressing plates and applying ultrasonic waves to the pressing plates so that the adhesive layer cures under the action of the ultrasonic waves.

2. The method for manufacturing a circuit board according to claim 1, characterized in that, the step of pressing the two pressing plates and applying ultrasonic waves to the pressing plates so that the adhesive layer cures under the action of the ultrasonic waves comprises: using air cylinders to push the two pressing plates respectively; and placing an ultrasonic head emitting the ultrasonic waves on the pressing plates and moving on the pressing plates so that the adhesive layer cures.

3. The method for manufacturing a circuit board according to claim 1, characterized in that, blind holes are formed on the first substrate, and openings are formed on the adhesive layer; in the step of covering the adhesive layer on the surface of the first substrate, the openings communicate with the blind holes.

4. The method for manufacturing a circuit board according to claim 3, characterized in that, after the adhesive layer cures, the adhesive layer does not overflow into the openings and / or the blind holes.

5. The method for manufacturing a circuit board according to claim 1, characterized in that, the adhesive layer comprises one of epoxy resin, bismaleimide-triazine, and polyimide.

6. The method for manufacturing a circuit board according to claim 5, characterized in that, the adhesive layer further contains at least one of dicyandiamide, terephthalic acid, and inorganic hydroxide.

7. The method for manufacturing a circuit board according to claim 1, characterized in that, the first substrate comprises a first dielectric layer, and the material of the first dielectric layer comprises one of polyimide and modified polyimide.

8. The method for manufacturing a circuit board according to claim 1, characterized in that, the second substrate comprises a second dielectric layer, and the material of the second dielectric layer comprises one of polypropylene, liquid crystal polymer, and polytetrafluoroethylene.

9. A circuit board, characterized in that, it is formed by the method for manufacturing a circuit board according to any one of claims 1-8.

10. A terminal device, characterized in that, the terminal device comprises the circuit board according to claim 9.

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