Preparation method of multilayer circuit board and multilayer circuit board

Abstract

The invention discloses a preparation method of a multi-layer circuit board and the multi-layer circuit board. The preparation method comprises the following steps: printing soldering paste at the position of a connection point pad of each single-layer circuit board; placing an insulating layer between every two adjacent single-layer circuit boards to obtain a multi-layer circuit board stack; placing the multilayer circuit board stacking body between the upper hot-pressing lining plate and the lower hot-pressing lining plate to obtain a multilayer circuit board stacking clamping body; placing the multi-layer circuit board stacking clamping body into a vacuum hot press, then performing hot pressing on an insulating layer between every two adjacent single-layer circuit boards, and performing reflow soldering on soldering paste on a connection point welding pad of every two adjacent single-layer circuit boards to obtain a hot-state multi-layer circuit board; and cooling the hot-state multilayer circuit board to obtain a cold-state multilayer circuit board. According to the invention, the preparation time of the multilayer circuit board can be shortened, the electrical connection performance between two adjacent single-layer circuit boards in the multilayer circuit board can be improved, and the mechanical structure performance of the prepared multilayer circuit board can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of circuit boards, and particularly relates to a method for manufacturing a multi-layer circuit board and a multi-layer circuit board. Background Art

[0002] Currently, when manufacturing a multi-layer circuit board, solder is first disposed at the pad positions of each single-layer circuit board, and then the solder at the pads of each single-layer circuit board is subjected to a reflow soldering process through a reflow soldering device. Then, an insulating layer is placed between every two adjacent single-layer circuit boards and bonded together by a hot pressing method. After that, the soldering tin on the pads of every two adjacent single-layer circuit boards is melted again by the reflow soldering device and then cooled and solidified to connect the pads of every two adjacent single-layer circuit boards by reflow soldering. However, the heating operation in the reflow soldering process will cause the single-layer circuit board to deform, so that when stacking each single-layer circuit board and the corresponding insulating layer, the pad positions of two adjacent single-layer circuit boards cannot be completely aligned, thereby affecting the electrical connection performance between two adjacent single-layer circuit boards in the manufactured multi-layer circuit board and affecting the mechanical structure performance of the manufactured multi-layer circuit board. Summary of the Invention

[0003] In view of the defects of the above-mentioned prior art, the present invention provides a method for manufacturing a multi-layer circuit board and a multi-layer circuit board, which can shorten the manufacturing time of the multi-layer circuit board, improve the electrical connection performance between two adjacent single-layer circuit boards in the multi-layer circuit board, and improve the mechanical structure performance of the manufactured multi-layer circuit board.

[0004] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0005] A method for manufacturing a multi-layer circuit board includes the following steps:

[0006] S1. Print solder paste at the connection pad positions of each single-layer circuit board;

[0007] S2. Place an insulating layer between every two adjacent single-layer circuit boards and align the connection pad positions of every two adjacent single-layer circuit boards, wherein each insulating layer is located on one side of the connection pads of the corresponding two adjacent single-layer circuit boards, and stack each single-layer circuit board and the corresponding insulating layer to obtain a multi-layer circuit board stack;

[0008] S3. Place the multi-layer circuit board stack between two upper and lower hot pressing backing plates to complete the clamping of the multi-layer circuit board stack and obtain a multi-layer circuit board stack clamping body;

[0009] S4. Place the stacked and clamped multi-layer circuit board into a vacuum hot press, and then thermally press the insulating layer between every two adjacent single-layer circuit boards, so that every two adjacent single-layer circuit boards are bonded together, and the solder paste on the connection solder pads of every two adjacent single-layer circuit boards is first melted and then cooled and solidified. At the same time, the gas generated during the melting and solidification of the solder paste is discharged from between the two adjacent single-layer circuit boards through the exhaust channels of the corresponding two adjacent single-layer circuit boards, completing the reflow soldering of the solder paste on the connection solder pads of every two adjacent single-layer circuit boards, realizing the electrical connection between the connection solder pads of every two adjacent single-layer circuit boards, and obtaining a hot multi-layer circuit board;

[0010] S5. Lower the temperature inside the cavity of the vacuum hot press, cool the hot multi-layer circuit board to obtain a cold multi-layer circuit board, and take out the cold multi-layer circuit board.

[0011] Further, step S4 is specifically: Place the stacked and clamped multi-layer circuit board between the upper and lower hot press plates with heating and cooling functions in the vacuum hot press, then start the heating functions of the upper and lower hot press plates and apply pressure to the upper and lower hot press plates, thermally press the insulating layer between every two adjacent single-layer circuit boards, so that the corresponding insulating layer is softened by thermal pressing, adheres to the surfaces of the corresponding two adjacent single-layer circuit boards and solidifies, and the solder paste on the connection solder pads of every two adjacent single-layer circuit boards is first melted, then start the cooling functions of the upper and lower hot press plates, cool and solidify the molten solder on the connection solder pads of every two adjacent single-layer circuit boards, and at the same time, discharge the gas volatilized during the melting and solidification of the solder paste from between the two adjacent single-layer circuit boards through the exhaust channels of the corresponding two adjacent single-layer circuit boards, completing the reflow soldering of the solder paste on the connection solder pads of every two adjacent single-layer circuit boards, realizing the electrical connection between the connection solder pads of every two adjacent single-layer circuit boards, and obtaining a hot multi-layer circuit board.

[0012] Further, step S5 is specifically: Continuously cool the upper and lower hot press plates to continuously cool the hot multi-layer circuit board. When the temperature inside the cavity of the vacuum hot press drops below the set temperature value, the hot multi-layer circuit board is transformed into a cold multi-layer circuit board, and the cold multi-layer circuit board is taken out.

[0013] Further, in step S4: The cooling function of the hot press plate is realized by arranging a liquid cooling circuit in the hot press plate, and coolant is introduced into the liquid cooling circuit to start the cooling function of the hot press plate.

[0014] Further, in step S4: The cooling and solidification rate of the molten solder on the connection solder pads of every two adjacent single-layer circuit boards is 3°C / s.

[0015] Further, in step S5: The set temperature value is 40°C.

[0016] Further, in step S5:

[0017] The cold multi-layer circuit board is placed between the upper and lower hot pressing backing plates;

[0018] Taking out the cold multi-layer circuit board specifically is: taking out the upper and lower hot pressing backing plates and the cold multi-layer circuit board placed between the upper and lower hot pressing backing plates together, and removing the upper and lower hot pressing backing plates.

[0019] Further, step S1 specifically is: using a screen printing machine to scrape and print solder paste at the connection solder pad positions of each single-layer circuit board, and performing drying and dehydration treatment on the solder paste on the connection solder pads to discharge the excess moisture in the solder paste, wherein the drying temperature is 50°C.

[0020] Further,

[0021] In step S1: the single-layer circuit board is a single-layer circuit copper plate, multiple conductors are arranged on the single-layer circuit copper plate, connection solder pads are arranged at the wire ends of each conductor, insulating glue is arranged between adjacent wires, and the exhaust channels on the single-layer circuit copper plate are arranged at the positions between adjacent connection solder pads;

[0022] In step S2: the insulating layer is a prepreg, and the prepreg is composed of resin and reinforcing material, wherein the reinforcing material is a glass fiber cloth.

[0023] A multi-layer circuit board is prepared by using the above preparation method of the multi-layer circuit board, and includes multiple single-layer circuit boards. An insulating layer is arranged between every two adjacent single-layer circuit boards. Every two adjacent single-layer circuit boards and the corresponding insulating layer are hot-pressed and bonded, and the solder paste on the connection solder pads of every two adjacent single-layer circuit boards is reflow soldered to realize the electrical connection between the connection solder pads of every two adjacent single-layer circuit boards.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] The preparation method of the multi-layer circuit board of the present invention comprises: printing solder paste at the connection solder pad positions of each single-layer circuit board; placing an insulating layer between every two adjacent single-layer circuit boards and aligning the connection solder pad positions of every two adjacent single-layer circuit boards, wherein each insulating layer is located on one side of the connection solder pads of the corresponding two adjacent single-layer circuit boards, stacking each single-layer circuit board and the corresponding insulating layer to obtain a multi-layer circuit board stack; placing the multi-layer circuit board stack between two upper and lower hot pressing backing plates to complete the clamping of the multi-layer circuit board stack and obtain a multi-layer circuit board clamping body; putting the multi-layer circuit board clamping body into a vacuum hot press, then hot pressing the insulating layer between every two adjacent single-layer circuit boards to bond every two adjacent single-layer circuit boards together, melting and then cooling and solidifying the solder paste on the connection solder pads of every two adjacent single-layer circuit boards, and discharging the gas generated during the melting and solidification of the solder paste from between the two adjacent single-layer circuit boards through the exhaust channels of the corresponding two adjacent single-layer circuit boards to complete the reflow soldering of the solder paste on the connection solder pads of every two adjacent single-layer circuit boards, realizing the electrical connection between the connection solder pads of every two adjacent single-layer circuit boards to obtain a hot multi-layer circuit board; reducing the internal cavity temperature of the vacuum hot press to cool the hot multi-layer circuit board to obtain a cold multi-layer circuit board, and taking out the cold multi-layer circuit board. Compared with the existing preparation method of multi-layer circuit boards in the background art, the preparation method of the multi-layer circuit board in the present invention cancels the separate reflow soldering and tinning process, integrates the reflow soldering process of the solder paste in the hot pressing and bonding process of the multi-layer circuit board, so it can shorten the preparation process of the multi-layer circuit board, greatly shorten the preparation time of the multi-layer circuit board, and simplify the preparation method of the multi-layer circuit board; and because the separate reflow soldering and tinning process is cancelled, each single-layer circuit board in the obtained multi-layer circuit board stack does not deform due to the heating operation in the reflow soldering and tinning process, and then the connection solder pad positions of every two adjacent single-layer circuit boards in the obtained multi-layer circuit board stack can be completely aligned, so as to improve the electrical connection performance between two adjacent single-layer circuit boards in the multi-layer circuit board and improve the mechanical structure performance of the manufactured multi-layer circuit board. Moreover, canceling the separate reflow soldering and tinning process can save the investment in reflow soldering equipment, thereby reducing the occupation of production space and reducing the consumed energy cost; in addition, in the present invention, the reflow soldering of the solder paste on the connection solder pads of every two adjacent single-layer circuit boards is completed in the vacuum environment of the vacuum hot press, so that the bubbles in the solder can be reduced, thereby improving the electrical connection performance between two adjacent single-layer circuit boards. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a line graph showing the temperature change of the two upper and lower hot pressing plates with time in a specific embodiment;

[0027] Figure 2It is a line graph showing the pressure on the upper and lower hot plates changing over time in a specific embodiment;

[0028] Figure 3 It is a schematic structural diagram of a single-layer circuit board in a specific embodiment;

[0029] Figure 4 It is a schematic structural diagram after placing a stacked clamping body of multi-layer circuit boards between the upper and lower hot plates in a vacuum hot press in a specific embodiment;

[0030] Figure 5 It is Figure 4 An enlarged schematic diagram of the solder paste before the insulating layer at the circled A in

[0031] Figure 6 It is Figure 4 An enlarged schematic diagram after the insulating layer at the circled A in

[0032] Explanation of the reference numerals in the figure: 1. Hot plate, 2. Hot pressing backing plate, 3. Insulating layer, 4. Solder paste, 5. Single-layer circuit board, 501. Conductive wire, 502. Connecting solder pad, 503. Insulating glue, 504. Exhaust channel. Detailed implementation manners

[0033] The following further elaborates on the detailed implementation manners of the present invention with reference to the attached drawings. These implementation manners are only for illustrating the present invention and are not intended to limit the present invention.

[0034] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the attached drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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 construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0035] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] A method for preparing a multi-layer circuit board, comprising the following steps:

[0037] S1. Use a screen printing machine to scrape and print solder paste 4 at the positions of the connection solder pads 502 of each single-layer circuit board 5, and perform drying and dehydration treatment on the solder paste 4 on the connection solder pads 502 to discharge the excess moisture in the solder paste 4;

[0038] S2. Place an insulating layer 3 between every two adjacent single-layer circuit boards 5, and align the positions of the connection solder pads 502 of every two adjacent single-layer circuit boards 5, wherein each insulating layer 3 is located on one side of the connection solder pads 502 of the corresponding two adjacent single-layer circuit boards 5, and stack each single-layer circuit board 5 and the corresponding insulating layer 3 to obtain a multi-layer circuit board stack;

[0039] S3. Place the multi-layer circuit board stack between two upper and lower hot pressing backing plates 2 to complete the clamping of the multi-layer circuit board stack, obtaining a multi-layer circuit board stack clamping body, wherein the hot pressing backing plates 2 have heat conduction performance;

[0040] S4. Place the multi-layer circuit board stack clamping body between two upper and lower hot pressing plates 1 with heating and cooling functions in a vacuum hot press, then start the heating functions of the two upper and lower hot pressing plates 1 and apply pressure to the two upper and lower hot pressing plates 1, and perform hot pressing on the insulating layer 3 between every two adjacent single-layer circuit boards 5, so that the corresponding insulating layer 3 is softened by hot pressing, adheres to the surfaces of the corresponding two adjacent single-layer circuit boards 5 and solidifies, and first melts the solder paste 4 on the connection solder pads 502 of every two adjacent single-layer circuit boards 5, then start the cooling functions of the two upper and lower hot pressing plates 1, cool and solidify the molten solder on the connection solder pads 502 of every two adjacent single-layer circuit boards 5, and at the same time discharge the gas generated during the melting and solidification of the solder paste 4 from between the two adjacent single-layer circuit boards through the exhaust channels 504 of the corresponding two adjacent single-layer circuit boards 5, complete the reflow soldering of the solder paste 4 on the connection solder pads 502 of every two adjacent single-layer circuit boards 5, and realize the electrical connection between the connection solder pads 502 of every two adjacent single-layer circuit boards 5 to obtain a hot multi-layer circuit board;

[0041] S5. Continuously cool the two upper and lower hot pressing plates 1 to realize the continuous cooling of the hot multi-layer circuit board. When the temperature inside the cavity of the vacuum hot press drops below the set temperature value, the hot multi-layer circuit board is transformed into a cold multi-layer circuit board, wherein the cold multi-layer circuit board is placed between the two upper and lower hot pressing backing plates 2, and then the two upper and lower hot pressing backing plates 2 and the cold multi-layer circuit board placed between the two upper and lower hot pressing backing plates 2 are taken out of the vacuum hot press together, and the two upper and lower hot pressing backing plates 2 are removed.

[0042] Compared with the existing preparation method of multi-layer circuit boards in the background art, in the preparation method of multi-layer circuit boards of the present invention, the separate reflow soldering and tinning process is cancelled, and the reflow soldering process of solder paste 4 is integrated into the hot pressing and bonding process of multi-layer circuit boards, which can shorten the preparation process of multi-layer circuit boards, greatly shorten the preparation time of multi-layer circuit boards, and simplify the preparation method of multi-layer circuit boards; moreover, due to the cancellation of the separate reflow soldering and tinning process, each single-layer circuit board 5 in the obtained multi-layer circuit board stack does not deform due to the heating operation in the reflow soldering and tinning process. Furthermore, the connection solder pads 502 of every two adjacent single-layer circuit boards 5 in the obtained multi-layer circuit board stack can be completely aligned, so as to improve the electrical connection performance between two adjacent single-layer circuit boards 5 in the multi-layer circuit board and improve the mechanical structure performance of the manufactured multi-layer circuit board. In addition, the cancellation of the separate reflow soldering and tinning process can save the investment in reflow soldering equipment, reduce the occupation of production space, and reduce the consumed energy cost; in addition, in the present invention, the reflow soldering of solder paste 4 on the connection solder pads 502 of every two adjacent single-layer circuit boards 5 is completed in the vacuum environment of a vacuum hot press, which can reduce the bubbles in the solder, thereby improving the electrical connection performance between two adjacent single-layer circuit boards 5.

[0043] Among them,

[0044] In step S1: The single-layer circuit board 5 is a single-layer circuit copper plate, and a plurality of conductors are arranged on the single-layer circuit copper plate. Connection solder pads 502 are arranged at the ends of the leads 501 of each conductor, and insulating glue 503 is arranged between adjacent leads. The exhaust channel 504 on the single-layer circuit copper plate is arranged at a position between adjacent connection solder pads 502; among them, the drying temperature for the drying and dehydration treatment is 50 °C.

[0045] In step S2: The insulating layer 3 is a prepreg, and the prepreg is composed of resin and reinforcing material, and the reinforcing material is a fiberglass cloth.

[0046] Among them, in step S4: The cooling function of the hot pressing plate 1 is realized by arranging a liquid cooling circuit in the hot pressing plate 1, and coolant is introduced into the liquid cooling circuit to start the cooling function of the hot pressing plate 1; among them, the cooling and solidification rate of the molten solder on the connection solder pads 502 of every two adjacent single-layer circuit boards 5 is 3 °C / s.

[0047] Among them, in step S5: The set temperature value is 40 °C.

[0048] A multi-layer circuit board is prepared by using the above-mentioned preparation method of the multi-layer circuit board, and includes a plurality of single-layer circuit boards 5. An insulating layer 3 is arranged between every two adjacent single-layer circuit boards 5. Every two adjacent single-layer circuit boards 5 and the corresponding insulating layer 3 are hot-pressed and bonded, and the solder paste 4 on the connection solder pads 502 of every two adjacent single-layer circuit boards 5 is reflow soldered to achieve electrical connection between the connection solder pads 502 of every two adjacent single-layer circuit boards 5. Specific embodiment

[0050] A multi-layer circuit board is prepared by using the above-mentioned preparation method of the multi-layer circuit board, and includes two single-layer circuit boards 5. An insulating layer 3 is arranged between the two single-layer circuit boards 5. The two single-layer circuit boards 5 and the insulating layer 3 are hot-pressed and bonded, and the solder paste 4 on the connection solder pads 502 of the two single-layer circuit boards 5 is reflow soldered to achieve electrical connection between the connection solder pads 502 of the two single-layer circuit boards 5.

[0051] A preparation method of a multi-layer circuit board includes the following steps:

[0052] S1. Use a screen printing machine to scrape and print solder paste 4 at the positions of the connection solder pads 502 of two single-layer circuit boards 5, and perform drying and dehydration treatment on the solder paste 4 on the connection solder pads 502 to discharge the excess moisture in the solder paste. The structural schematic diagram of the single-layer circuit board 5 is shown in Figure 3 ;

[0053] S2. Place an insulating layer 3 between the two single-layer circuit boards 5 and align the positions of the connection solder pads 502 of the two single-layer circuit boards 5. The insulating layer 3 is located on one side of the connection solder pads 502 of the two single-layer circuit boards 5 to complete the stacking of the two single-layer circuit boards 5 and the insulating layer 3, and obtain a multi-layer circuit board stack.

[0054] S3. Place the multi-layer circuit board stack between the upper and lower hot-pressing backing plates 2 to complete the clamping of the multi-layer circuit board stack and obtain a multi-layer circuit board stack clamping body.

[0055] S4. Place the multi-layer circuit board stack clamping body between the upper and lower hot pressing plates 1 with heating and cooling functions in a vacuum hot press, as shown in Figure 4 and 5, then start the heating function of the upper and lower hot pressing plates 1 and apply pressure to the upper and lower hot pressing plates 1 to hot press the insulating layer 3 between the two single-layer circuit boards 5, so that the insulating layer 3 is softened by hot pressing, adheres to the surfaces of the two single-layer circuit boards 5 and is cured, and the solder paste 4 on the connection solder pads 502 of the two single-layer circuit boards 5 is first melted, and then start the cooling function of the upper and lower hot pressing plates 1 to cool and cure the molten solder on the connection solder pads 502 of the two single-layer circuit boards 5. At the same time, the gas generated during the melting and solidification of the solder paste 4 is discharged from between the two adjacent single-layer circuit boards through the exhaust channels 504 of the corresponding two adjacent single-layer circuit boards 5, completing the reflow soldering of the solder paste 4 on the connection solder pads 502 of the two single-layer circuit boards 5 and realizing the electrical connection between the connection solder pads 502 of the two single-layer circuit boards 5, as shown in Figure 6 , obtaining a hot multi-layer circuit board;

[0056] S5. Continuously cool the upper and lower hot pressing plates 1 to continuously cool the hot multi-layer circuit board. When the temperature inside the vacuum hot press drops below 40 °C, the hot multi-layer circuit board turns into a cold multi-layer circuit board, where the cold multi-layer circuit board is placed between the upper and lower hot pressing liners 2. Then, take out the upper and lower hot pressing liners 2 and the cold multi-layer circuit board placed between the upper and lower hot pressing liners 2 from the vacuum hot press together, and remove the upper and lower hot pressing liners 2.

[0057] As Figure 1 shown, the temperature of the upper and lower hot pressing plates 1 gradually increases with time between 0 - 1 min, remains constant between 1 - 6 min, continues to gradually increase with time between 6 - 44 min, remains constant between 44 - 49 min, continues to gradually increase with time between 49 - 52 min, continues to gradually increase with time between 52 - 60 min, rapidly decreases with time between 60 - 60.33 min, and continues to gradually decrease with time between 60.33 - 85 min. Figure 1 The time and temperature represented by each point on the broken line of Figure 2As shown, at the 0th minute, the pressure received by the upper and lower hot press plates 1 is 0 and directly rises to 16 bar. Between 0 - 6 minutes, the pressure received by the upper and lower hot press plates 1 remains unchanged. At the 6th minute, the pressure received by the upper and lower hot press plates 1 directly rises to 20 bar. Between 6 - 26 minutes, the pressure received by the upper and lower hot press plates 1 remains unchanged. At the 26th minute, the pressure received by the upper and lower hot press plates 1 directly rises to 25 bar. Between 26 - 36 minutes, the pressure received by the upper and lower hot press plates 1 remains unchanged. At the 36th minute, the pressure received by the upper and lower hot press plates 1 directly rises to 30 bar. Between 36 - 46 minutes, the pressure received by the upper and lower hot press plates 1 remains unchanged. At the 46th minute, the pressure received by the upper and lower hot press plates 1 directly rises to 35 bar. Between 46 - 85 minutes, the pressure received by the upper and lower hot press plates 1 remains unchanged. At the 85th minute, the pressure received by the upper and lower hot press plates 1 directly drops to 0. Figure 2 The time and pressure represented by each point on the broken line of Figure 2 are shown in Table 2.

[0058] Table 1 Relationship table of the temperature of the upper and lower hot press plates changing with time

[0059]

[0060] Table 2 Relationship table of the pressure received by the upper and lower hot press plates changing with time

[0061]

[0062] From Figure 1 and Figure 2 it can be seen that between 0 - 52 minutes is the process of hot pressing and softening the insulating layer 3 and adhering the surfaces of the two single - layer circuit boards 5. Between 52 - 60.33 minutes is the reflow soldering process of the solder paste 4 on the connection solder pads 502 of the two single - layer circuit boards 5. Among them, between 60 - 60.33 minutes is the cooling and solidification process of the molten solder on the connection solder pads 502 of the two single - layer circuit boards 5. Specifically, at the 60th minute, the cooling function of the upper and lower hot press plates 1 is started, so that the molten solder on the connection solder pads 502 of the two single - layer circuit boards 5 rapidly cools within the cooling time range between 60 - 60.33 minutes, forming Figure 6The shown form, wherein the temperature of the upper and lower hot pressing plates 1 is 230°C at the 60th minute, and the temperature of the upper and lower hot pressing plates 1 drops to 170°C at the 60.33rd minute. Then, the cooling and solidification rate of the molten solder on the connection solder pads 502 of the two single-layer circuit boards 5 is 3°C / s. During the period from 60.33 to 85 minutes, the upper and lower hot pressing plates 1 are continuously cooled to achieve continuous cooling of the hot multi-layer circuit board. When the internal cavity temperature of the vacuum hot press drops below 40°C, the hot multi-layer circuit board turns into a cold multi-layer circuit board. The cold multi-layer circuit board is placed between the upper and lower hot pressing liners 2. Then, the upper and lower hot pressing liners 2 and the cold multi-layer circuit board placed between the upper and lower hot pressing liners 2 are taken out of the vacuum hot press together, and the upper and lower hot pressing liners 2 are removed.

[0063] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the technical principle of the present invention, several improvements and replacements can be made, and these improvements and replacements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a multi-layer circuit board, characterized in that, Including the following steps: S1. Print solder paste (4) at the position of the connection solder pads (502) of each single-layer circuit board (5); S2. Place an insulating layer (3) between every two adjacent single-layer circuit boards (5), and align the positions of the connection solder pads (502) of every two adjacent single-layer circuit boards (5), where each insulating layer (3) is located on one side of the connection solder pads (502) of the corresponding two adjacent single-layer circuit boards (5), and stack each single-layer circuit board (5) and the corresponding insulating layer (3) to obtain a multi-layer circuit board stack; S3. Place the multi-layer circuit board stack between two upper and lower hot pressing backing plates (2) to complete the clamping of the multi-layer circuit board stack and obtain a multi-layer circuit board stack clamping body; S4. Place the multi-layer circuit board stack clamping body into a vacuum hot press, and then hot press the insulating layer (3) between every two adjacent single-layer circuit boards (5) to bond every two adjacent single-layer circuit boards (5) together, and first melt and then cool and solidify the solder paste (4) on the connection solder pads (502) of every two adjacent single-layer circuit boards (5). At the same time, discharge the gas generated during the melting and solidification of the solder paste (4) from between the two adjacent single-layer circuit boards through the exhaust channels (504) of the corresponding two adjacent single-layer circuit boards (5), complete the reflow soldering of the solder paste (4) on the connection solder pads (502) of every two adjacent single-layer circuit boards (5), realize the electrical connection between the connection solder pads (502) of every two adjacent single-layer circuit boards (5), and obtain a hot multi-layer circuit board; S5. Reduce the temperature inside the cavity of the vacuum hot press, cool the hot multi-layer circuit board to obtain a cold multi-layer circuit board, and take out the cold multi-layer circuit board.

2. The manufacturing method of a multi-layer circuit board according to claim 1, wherein, Step S4 is specifically: Place the multi-layer circuit board stack clamping body between two upper and lower hot pressing plates (1) with heating and cooling functions in the vacuum hot press, then start the heating functions of the two upper and lower hot pressing plates (1) and apply pressure to the two upper and lower hot pressing plates (1) to hot press the insulating layer (3) between every two adjacent single-layer circuit boards (5), so that the corresponding insulating layer (3) is softened by hot pressing, adheres to the surfaces of the corresponding two adjacent single-layer circuit boards (5) and solidifies, and first melt the solder paste (4) on the connection solder pads (502) of every two adjacent single-layer circuit boards (5), then start the cooling functions of the two upper and lower hot pressing plates (1) to cool and solidify the molten solder on the connection solder pads (502) of every two adjacent single-layer circuit boards (5). At the same time, discharge the gas generated during the melting and solidification of the solder paste (4) from between the two adjacent single-layer circuit boards through the exhaust channels (504) of the corresponding two adjacent single-layer circuit boards (5), complete the reflow soldering of the solder paste (4) on the connection solder pads (502) of every two adjacent single-layer circuit boards (5), realize the electrical connection between the connection solder pads (502) of every two adjacent single-layer circuit boards (5), and obtain a hot multi-layer circuit board.

3. The preparation method of a multi-layer circuit board according to claim 2, characterized in that, Step S5 specifically is: Continuously cool the upper and lower hot press plates (1) to continuously cool the hot multi-layer circuit board. When the temperature inside the vacuum hot press drops below the set temperature value, the hot multi-layer circuit board turns into a cold multi-layer circuit board, and then take out the cold multi-layer circuit board.

4. The manufacturing method of a multi-layer circuit board according to claim 2, wherein, In step S4: The cooling function of the hot press plate (1) is achieved by arranging a liquid cooling circuit inside the hot press plate (1), and coolant is introduced into the liquid cooling circuit to start the cooling function of the hot press plate (1).

5. The manufacturing method of a multi-layer circuit board according to claim 2, characterized in that, In step S4: The cooling and solidification rate of the molten solder on the connecting solder pads (502) of every two adjacent single-layer circuit boards (5) is 3 °C / s.

6. The manufacturing method of a multilayer circuit board according to claim 3, wherein, In step S5: The set temperature value is 40 °C.

7. The preparation method of a multi-layer circuit board according to claim 1, characterized in that In step S5: The cold multi-layer circuit board is placed between the upper and lower hot press liners (2); Taking out the cold multi-layer circuit board specifically is: Take out the upper and lower hot press liners (2) and the cold multi-layer circuit board placed between the upper and lower hot press liners (2) together, and then remove the upper and lower hot press liners (2).

8. A method for preparing a multi-layer circuit board according to claim 1, characterized in that, Step S1 specifically is: Use a screen printing machine to scrape and print solder paste (4) at the positions of the connecting solder pads (502) of each single-layer circuit board (5), and perform drying and dehydration treatment on the solder paste (4) on the connecting solder pads (502) to discharge the excess moisture in the solder paste (4).

9. A method for manufacturing a multi-layer circuit board according to claim 1, wherein, In step S1: The single-layer circuit board (5) is a single-layer circuit copper plate. Multiple conductors are provided on the single-layer circuit copper plate. Connecting solder pads (502) are provided at the ends of the leads (501) of each conductor. An insulating adhesive (503) is provided between adjacent leads. The exhaust channels (504) on the single-layer circuit copper plate are arranged at positions between adjacent connecting solder pads (502); In step S2: The insulating layer (3) is a prepreg, and the prepreg is composed of a resin and a reinforcing material, wherein the reinforcing material is a glass fiber cloth.

10. A multilayer circuit board is formed by using the preparation method of the multilayer circuit board according to any one of claims 1-9, and is characterized in that: It includes multiple single-layer circuit boards (5). An insulating layer (3) is provided between every two adjacent single-layer circuit boards (5). Every two adjacent single-layer circuit boards (5) and the corresponding insulating layer (3) are hot-pressed and bonded. The solder paste (4) on the connecting solder pads (502) of every two adjacent single-layer circuit boards (5) is reflow soldered to achieve electrical connection between the connecting solder pads (502) of every two adjacent single-layer circuit boards (5).

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