Millimeter wave radar circuit board processing method and millimeter wave radar circuit board

Abstract

The invention discloses a processing method of a millimeter wave radar circuit board, which can realize signal shielding by embedding a copper wire, and compared with the traditional method for realizing signal shielding by adopting a blind hole, the embedded copper wire can be continuously arranged along a radio frequency circuit pattern, so that the signal shielding area can be effectively increased, and the signal shielding efficiency is improved. And the signal shielding effect can be improved. Besides, traditional blackening, blackening removal, plasma degumming, hole filling electroplating, copper reduction and other procedures can be omitted in the machining process, the machining process is greatly shortened, and then the machining efficiency of the millimeter wave radar circuit board can be improved. In addition, the invention further discloses the millimeter-wave radar circuit board formed by the processing method of the millimeter-wave radar circuit board.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit board processing, and in particular to a processing method of a millimeter wave radar circuit board and a millimeter wave radar circuit board. Background Art

[0002] At present, the main way to shield the signal of the millimeter-wave radar circuit board is to add blind holes in the RF circuit layer, and then fill the blind holes by electroplating, and achieve signal shielding through the copper layer. The specific process is: inner layer circuit production → pressing plate → blackening → laser blind hole → de-blackening → mechanical drilling → high-pressure water washing → plasma degumming → chemical degumming → hole metallization → hole filling electroplating → pulse electroplating → resin plugging hole → copper reduction → outer layer circuit etching. Due to the spacing between adjacent blind holes, it is impossible to achieve full closure of the signal, and the disadvantage of signal leakage is prone to occur. Secondly, since the blind hole is processed by laser, it is necessary to blacken it before the laser blind hole to facilitate the smooth progress of the laser process. De-blackening is required after the laser blind hole, and plasma degumming is required to remove the residual glue in the blind hole, otherwise it will not be possible to plate copper on the inner wall of the blind hole smoothly. In addition, since there are both blind holes and through holes on the circuit board, both the blind holes and through holes need to be plated during electroplating. Due to the limitation of hole-filling electroplating capacity, it is usually impossible to achieve blind and through hole co-plating at one time. Therefore, it is necessary to first plate the inner wall of the blind hole by hole-filling electroplating, and then electroplate the inner wall of the through hole by pulse plating. Due to the two electroplating steps, the surface copper thickness of the circuit board will increase significantly. Therefore, after electroplating, the surface copper of the circuit board needs to be reduced. The operation is extremely cumbersome, the processing flow is long, and the production efficiency is low. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a method for processing a millimeter wave radar circuit board, which can not only improve the signal shielding effect, but also shorten the processing flow and improve production efficiency.

[0004] The present invention also provides a millimeter wave radar circuit board formed by using the above-mentioned millimeter wave radar circuit board processing method.

[0005] The method for processing a millimeter wave radar circuit board according to an embodiment of the present invention comprises the following steps:

[0006] S1: Cutting materials to obtain a first PP board, a second PP board, a first copper foil, a second copper foil, an inner core board and copper wire;

[0007] S2: Gong material, processing a first through groove on the first copper foil according to the RF circuit pattern, and processing a second through groove on the first PP board according to the RF circuit pattern;

[0008] S3: inner layer circuit production, producing inner layer circuit patterns on the inner core board;

[0009] S4: stacking the boards, stacking the second copper foil, the second PP board, the inner core board, the first PP board, and the first copper foil in sequence from bottom to top, the inner core board having a metal surface facing the first PP board, the first through groove being aligned with the second through groove, and the first through groove, the second through groove, and the upper surface of the inner core board are surrounded to form an installation groove, and the copper wire is embedded in the installation groove;

[0010] S5: Pressing the stacked multilayer boards;

[0011] S6: drilling, processing through holes on the multilayer board;

[0012] S7: copper plating, forming a first copper layer on the surface of the first copper foil, the first copper layer covers the mounting groove and is embedded between the copper wire and the inner wall of the mounting groove, and forming a second copper layer on the inner wall of the through hole;

[0013] S8: Post-process.

[0014] The method for processing a millimeter wave radar circuit board according to an embodiment of the present invention has at least the following beneficial effects:

[0015] In the processing method of the millimeter-wave radar circuit board of the embodiment of the present invention, signal shielding can be achieved by embedding copper wires. Compared with the traditional method of using blind holes to achieve signal shielding, the embedded copper wires can be continuously arranged along the RF circuit pattern, thereby effectively increasing the signal shielding area and further improving the signal shielding effect. Secondly, since the blind hole structure in the traditional structure is eliminated, there is no need to perform laser blind holes, and thus there is no need for blackening, de-blackening and plasma degumming. In addition, during electroplating, only one electroplating is required to achieve through-hole metallization, eliminating the process of filling the blind holes with electroplating, and the circuit board will not have too thick surface copper due to the need to perform two electroplating processes, so there is no need to perform a copper reduction process. It can be seen that compared with the traditional processing method, the processing method of the millimeter-wave radar circuit board of the embodiment of the present invention only needs to perform gong plate after cutting to process the first through groove and the second through groove, and then press the copper wire into the installation groove formed by the connection of the first through groove and the second through groove when stacking the boards. There is no need to perform blackening, de-blackening, plasma degumming, filling hole plating, copper reduction and other processes, which greatly shortens the processing flow, thereby helping to improve the processing efficiency of the millimeter-wave radar circuit board.

[0016] According to some embodiments of the present invention, between step S3 and step S4, browning is also included, in which the copper wire and the inner core board are subjected to browning treatment, and the amount of copper bitten by browning is 1.4μm-1.8μm. After browning, the surface roughness Rz value of the copper wire and the inner core board is 3±1μm, and the Ra value is 0.4±0.2μm.

[0017] According to some embodiments of the present invention, when the copper wire is subjected to browning treatment, the copper wire is fixed on a tray and passed through a browning line at a browning line speed of 1.0 m / min. After browning, the copper wire is dried at a drying temperature of 90±5°C.

[0018] According to some embodiments of the present invention, step S5 comprises:

[0019] S5.1: pre-pressing, sequentially covering the first copper foil with a first kraft paper assembly and a first steel plate, and pre-pressing the stacked copper wire, the second copper foil, the second PP plate, the inner core plate, the first PP plate, and the first copper foil through the first steel plate;

[0020] S5.2: Hot pressing: sequentially cover the second kraft paper assembly and the second steel plate on the first copper foil, and hot press the stacked second steel plate, the second kraft paper assembly, the copper wire, the second copper foil, the second PP plate, the inner core plate, the first PP plate, and the first copper foil, with a heating rate of 2.5°C / min.

[0021] S5.3: cold pressing: cold pressing the stacked second steel plate, the second kraft paper assembly, the copper wire, the second copper foil, the second PP plate, the inner core plate, the first PP plate, and the first copper foil, with a cold pressing pressure of 30 bar and a cold pressing time of 45 minutes.

[0022] According to some embodiments of the present invention, the inner core board includes at least two copper substrates, all of which are stacked in sequence, and a prepreg layer is sandwiched between two adjacent copper substrates.

[0023] According to some embodiments of the present invention, step S7 includes:

[0024] S7.1: grinding the surfaces of the first copper foil and the second copper foil to remove the flash at the through hole and the residual glue at the mounting groove;

[0025] S7.2: removing adhesive residues formed by the prepreg layer on the inner wall of the through hole, and removing adhesive residues formed by the first PP layer between the copper wire and the inner wall of the mounting groove;

[0026] S7.3: electroplating, forming the first copper layer and the second copper layer by means of horizontal copper deposition and pulse electroplating.

[0027] According to some embodiments of the present invention, step S7.1 comprises:

[0028] Abrasive belt grinding plate, the mesh number of the abrasive belt is 320#

[0029] Needle brush grinding plate, the mesh number of the needle brush is 320#-540#, and the grinding plate pressure is 0.8±0.2kg / cm2.

[0030] According to some embodiments of the present invention, the thickness of the first copper foil and the second copper foil is 20 μm, the thickness of the first PP board and the second PP board is 125±12.5 μm, the width of the mounting groove is 200 μm, the width of the copper wire is 190 μm-200 μm, and the thickness of the copper wire is 90 μm-105 μm;

[0031] In the step S7.1, the surface copper removal thickness of the first copper foil and the second copper foil is 5-10 μm;

[0032] In the step S7.2, roughening is performed by chemical degumming;

[0033] In the step S7.3, the thickness of the first copper layer located on the surface of the first copper foil is not less than 30 μm.

[0034] According to some embodiments of the present invention, step S8 includes:

[0035] S8.1: outer layer circuit production, producing an outer layer circuit pattern on the surface of the first copper layer, and setting a pattern edge compensation amount on the portion of the outer layer circuit pattern located above the copper wire;

[0036] S8.2: baking the multilayer board at a temperature of 120° C. for 1 hour.

[0037] The millimeter wave radar circuit board according to the embodiment of the present invention is formed by processing the millimeter wave radar circuit board according to any one of the above embodiments.

[0038] The millimeter wave radar circuit board according to the embodiment of the present invention has at least the following beneficial effects:

[0039] In the millimeter-wave radar circuit board of the embodiment of the present invention, by adopting the processing method of the millimeter-wave radar circuit board of any of the above-mentioned embodiments, signal shielding can be achieved by embedding copper wires. Compared with the traditional method of using blind holes to achieve signal shielding, the embedded copper wires can be continuously arranged along the RF circuit pattern, thereby effectively increasing the area of ​​signal shielding, thereby improving the signal shielding effect. Secondly, since the millimeter-wave radar circuit board of the embodiment of the present invention does not require laser blind holes during processing, it is also unnecessary to perform blackening, de-blackening, plasma degumming, hole filling electroplating, copper reduction and other processes, thereby greatly shortening the processing flow of the millimeter-wave radar circuit board and improving the processing efficiency of the millimeter-wave radar circuit board.

[0040] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0042] Figure 1 This is a schematic diagram of the material preparation in step S2 of the method for processing a millimeter wave radar circuit board according to an embodiment of the present invention;

[0043] Figure 2 It is a schematic diagram of stacking boards in step S4 of the method for processing a millimeter wave radar circuit board according to an embodiment of the present invention;

[0044] Figure 3 It is a schematic diagram of a pressing plate in step S5 of a method for processing a millimeter wave radar circuit board according to an embodiment of the present invention;

[0045] Figure 4 A schematic diagram of drilling in step S6 of the method for processing a millimeter wave radar circuit board according to an embodiment of the present invention;

[0046] Figure 5 Schematic diagram of copper plating in step S7 of the method for processing a millimeter wave radar circuit board according to an embodiment of the present invention.

[0047] Reference numerals:

[0048] Multilayer board 100, first copper foil 110, first through groove 111, first PP board 120, second through groove 121, inner core board 130, copper substrate 131, prepreg sheet 132, second PP board 140, second copper foil 150, copper wire 160, mounting groove 200, through hole 300, first copper layer 400, second copper layer 500, third copper layer 600. DETAILED DESCRIPTION

[0049] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0050] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention 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 invention.

[0051] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0052] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0053] Reference Figures 1 to 5 An embodiment of the present invention provides a method for processing a millimeter wave radar circuit board, comprising the following steps:

[0054] S1: Cutting the materials to obtain a first PP board 120, a second PP board 140, a first copper foil 110, a second copper foil 150, an inner core board 130 and a copper wire 160;

[0055] S2: Gong material, processing the first through groove 111 on the first copper foil 110 according to the RF circuit pattern, and processing the second through groove 121 on the first PP board 120 according to the RF circuit pattern;

[0056] S3: inner layer circuit production, producing inner layer circuit patterns on the inner core board 130;

[0057] S4: stacking the boards, stacking the second copper foil 150, the second PP board 140, the inner core board 130, the first PP board 120, and the first copper foil 110 in sequence from bottom to top, the inner core board 130 has a metal surface facing the first PP board 120, the first through groove 111 is aligned with the second through groove 121, and the first through groove 111, the second through groove 121 and the upper surface of the inner core board 130 are surrounded to form a mounting groove 200, and the copper wire 160 is embedded in the mounting groove 200;

[0058] S5: Pressing the stacked multilayer boards 100;

[0059] S6: drilling, processing a through hole 300 on the multilayer board 100;

[0060] S7: Copper plating, forming a first copper layer 400 on the surface of the first copper foil 110, the first copper layer 400 covers the mounting groove 200 and is embedded between the copper wire 160 and the inner wall of the mounting groove 200, and forming a second copper layer 500 on the inner wall of the through hole 300;

[0061] S8: Post-process.

[0062] By adopting the processing method of the millimeter wave radar circuit board of the embodiment of the present invention, the inner layer circuit pattern is normally produced after cutting, and then the first through groove 111 is processed on the first copper foil 110 according to the radio frequency circuit pattern, and the second through groove 121 is processed on the first PP board 120 according to the radio frequency circuit pattern. When stacking the boards, the second copper foil 150, the second PP board 140, the inner core board 130, the first PP board 120, and the first copper foil 110 are stacked from bottom to top in sequence, and the inner core board 130 faces the first PP board 120. One side is a metal surface, the first through groove 111 and the second through groove 121 are aligned with each other and are enclosed with the upper surface of the inner core board 130 to form a mounting groove 200, thereby, when the copper wire 160 is embedded in the mounting groove 200, it will contact the metal surface of the inner core board 130, and then the multilayer board 100 is formed by pressing the board. During the pressing process, the first PP layer can not only tightly connect the first copper foil 110 and the inner core board 130, but also can be connected to the copper wire 160 so that the copper wire 160 is more stably embedded in the mounting groove 200. After the plate is pressed, drilling, copper plating and other processes can be carried out according to the normal process, and the through hole 300 can be processed on the multilayer board 100, and the second copper layer 500 can be formed on the inner wall of the through hole 300 by copper plating, thereby realizing the metallization of the through hole 300. In addition, during the copper plating process, a first copper layer 400 can also be formed on the surface of the first copper foil 110. The first copper layer 400 covers the mounting groove 200 and is embedded between the copper wire 160 and the inner wall of the mounting groove 200, thereby the copper wire 160 can be buried inside the multilayer board 100, so that the structure of the copper wire 160 is more stable, and the inner core board 130 and the first copper foil 110 can be connected through the copper wire 160, thereby realizing the signal shielding function.

[0063] It can be seen from the above that in the processing method of the millimeter-wave radar circuit board of the embodiment of the present invention, signal shielding can be achieved by embedding the copper wire 160. Compared with the traditional method of using blind holes to achieve signal shielding, the embedded copper wire 160 can be continuously arranged along the RF circuit pattern, thereby effectively increasing the signal shielding area and further improving the signal shielding effect. Secondly, in the processing method of the millimeter-wave radar circuit board of the embodiment of the present invention, since the blind hole structure in the traditional structure is cancelled, there is no need to perform laser blind holes, and thus there is no need to perform blackening, de-blackening and plasma degumming. In addition, during electroplating, only one electroplating is required to achieve metallization of the through hole 300, eliminating the process of filling the blind hole with electroplating, and the circuit board will not cause the surface copper to be too thick due to the need to perform two electroplating processes, so there is no need to perform a copper reduction process. It can be seen that compared with the traditional processing method, the processing method of the millimeter-wave radar circuit board of the embodiment of the present invention only needs to perform gong plate after cutting to process the first through groove 111 and the second through groove 121, and then press the copper wire 160 into the installation groove 200 formed by connecting the first through groove 111 and the second through groove 121 when stacking the plates. There is no need to perform blackening, de-blackening, plasma degumming, filling hole plating, copper reduction and other processes, which greatly shortens the processing flow, thereby helping to improve the processing efficiency of the millimeter-wave radar circuit board.

[0064] It is understandable that the copper wire 160 can be made of pure copper, so that the copper wire 160 has good flexibility and stretchability, which is not only conducive to achieving signal shielding effect, but also facilitates the smooth progress of the pressing process.

[0065] It is understandable that, since the copper wire 160 needs to be embedded in the second through groove 121 of the first PP board 120, in order to improve the installation stability of the copper wire 160, the first PP board 120 is selected from high-glue PP material with a glue content of ≥ 68%, and the first PP board 120 does not contain glass fiber, but is only filled with resin. The second PP board 140 can be selected from common FR4 PP material.

[0066] It is understandable that, in the milling process of step S2 , a milling cutter may be used to process the first copper foil 110 and the first PP board 120 to form the first through groove 111 and the second through groove 121 .

[0067] It can be understood that when the inner layer circuit is produced in step S3, in order to facilitate the stable connection between the copper wire 160 and the metal surface of the inner core board 130 close to the first PP board 120, a large copper surface design can be made on the side of the inner core board 130 close to the first PP board 120, and a normal inner layer circuit design can be made on the other metal surfaces of the inner core board 130.

[0068] It is understandable that during the drilling in step S6 , conventional drilling equipment may be used to mechanically drill the multilayer board 100 .

[0069] In some embodiments, between step S3 and step S4, browning is also included, in which the copper wire 160 and the inner core board 130 are browned, and the amount of copper bitten by browning is 1.4μm-1.8μm. After browning, the surface roughness Rz value of the copper wire 160 and the inner core board 130 is 3±1μm, and the Ra value is 0.4±0.2μm.

[0070] By adopting the above processing method, the copper wire 160 and the inner core board 130 are browned before lamination. The browning treatment can effectively improve the surface roughness of the copper wire 160 and the inner core board 130, which is beneficial to improve the surface bonding force between the copper wire 160 and the inner core board 130 in the subsequent lamination process, so that the bonding between the copper wire 160 and the inner core board 130, and between the inner core board 130 and the first PP board 120 and the second PP board 140 is more firm and stable, which is beneficial to improve the structural stability of the millimeter wave radar circuit board.

[0071] In some embodiments, when the copper wire 160 is subjected to browning treatment, the copper wire 160 is fixed on a tray and passed through a browning line at a browning line speed of 1.0 m / min. After browning, the copper wire 160 is dried at a drying temperature of 90±5°C.

[0072] By adopting the above processing method, the copper wire 160 is fixed on the tray, which can facilitate the copper wire 160 to be browned through the browning line, making the browning of the copper wire 160 more convenient. Browning the copper wire 160 can erode the oxide layer on the surface of the copper wire 160 and roughen the surface of the copper wire 160, thereby enhancing the surface bonding force of the copper wire 160 during pressing. After browning, the copper wire 160 is dried, which can facilitate the subsequent pressing of the copper wire 160.

[0073] In some embodiments, when stacking the boards in step S4, rivet holes need to be processed on the second copper foil 150, the second PP board 140, the inner core board 130, the first PP board 120, and the first copper foil 110, and rivets are pressed into the rivet holes during the stacking process. The second copper foil 150, the second PP board 140, the inner core board 130, the first PP board 120, and the first copper foil 110 are fixed together by rivets, thereby positioning the lamination of the multilayer board 100 and accurately aligning the first through groove 111 and the second through groove 121, thereby avoiding the occurrence of plate offset or lateral shift of the pattern during the lamination process.

[0074] It is understandable that the rivet holes can be processed separately for the first PP board 120, the second PP board 140, the first copper foil 110, the second copper foil 150, and the inner core board 130, or the rivet holes can be processed together after the second copper foil 150, the second PP board 140, the inner core board 130, the first PP board 120, and the first copper foil 110 are stacked from bottom to top, and the rivets are pressed into the rivet holes to fix the second copper foil 150, the second PP board 140, the inner core board 130, the first PP board 120, and the first copper foil 110 together. It is understandable that in order to achieve a better fixing effect, the rivet holes can be set at the four corners of the plate and the middle of the four sides of the plate, that is, eight rivet holes are opened on each plate.

[0075] In some embodiments, step S5 includes:

[0076] S5.1: Pre-pressing: sequentially cover the first kraft paper assembly and the first steel plate on the first copper foil 110, and pre-press the stacked copper wire 160, the second copper foil 150, the second PP plate 140, the inner core plate 130, the first PP plate 120, and the first copper foil 110 through the first steel plate;

[0077] S5.2: Hot pressing: sequentially cover the second kraft paper assembly and the second steel plate on the first copper foil 110, and hot press the stacked second steel plate, the second kraft paper assembly, the copper wire 160, the second copper foil 150, the second PP board 140, the inner core board 130, the first PP board 120, and the first copper foil 110, with a heating rate of 2.5°C / min.

[0078] S5.3: cold pressing: cold pressing the stacked second steel plate, the second kraft paper assembly, the copper wire 160, the second copper foil 150, the second PP plate 140, the inner core plate 130, the first PP plate 120, and the first copper foil 110, with a cold pressing pressure of 30 bar and a cold pressing time of 45 minutes.

[0079] By adopting the above method, the stacked copper wire 160, the second copper foil 150, the second PP board 140, the inner core board 130, the first PP board 120, and the first copper foil 110 are pre-pressed by the first steel plate, so that the second copper foil 150, the second PP board 140, the inner core board 130, the first PP board 120, and the first copper foil 110 can be made more flat, so as to facilitate the subsequent hot pressing process. During hot pressing, the first PP board 120 and the second PP board 140 can be melted at high temperature and high pressure, and the first copper foil 110, the inner core board 130, and the second copper foil 150 are tightly combined together through the first PP board 120 and the second PP board 140, so that the connection between the layers of the multilayer board 100 is more firm, ensuring more reliable electrical connection. Finally, cold pressing is performed, which can effectively eliminate the thermal stress generated by the multilayer board 100 during the hot pressing process, reduce the risk of warping and deformation of the multilayer board 100 due to thermal stress in subsequent processing, and ensure the flatness of the multilayer board 100 during the entire production and processing process, thereby helping to improve the dimensional stability and mechanical stability of the multilayer board 100.

[0080] In some embodiments, the thickness of the first steel plate is greater than the thickness of the second steel plate.

[0081] Since step S5.1 is to pre-press the stacked copper wire 160, the second copper foil 150, the second PP board 140, the inner core board 130, the first PP board 120, and the first copper foil 110 directly through the first steel plate, and step S5.2 is to hot press the stacked second steel plate, the second kraft paper assembly, the copper wire 160, the second copper foil 150, the second PP board 140, the inner core board 130, the first PP board 120, and the first copper foil 110 through the hot pressing equipment during hot pressing, therefore, setting the thickness of the first steel plate to be greater than the thickness of the second steel plate can facilitate the effective implementation of the pre-pressing process, thereby better pre-pressing the stacked copper wire 160, the second copper foil 150, the second PP board 140, the inner core board 130, the first PP board 120, and the first copper foil 110.

[0082] It is understood that in some embodiments, the thickness of the first steel plate is specifically 3.2 mm, and the thickness of the second steel plate is specifically 1.6 mm. Of course, this is only an exemplary description of a preferred embodiment, and the specific thickness of the first steel plate and the second steel plate is not specifically limited in the embodiment of the present invention. In addition, in order to further improve the flatness of the stacked copper wire 160, the second copper foil 150, the second PP plate 140, the inner core plate 130, the first PP plate 120, and the first copper foil 110 during hot pressing, the warping of the first steel plate during pre-pressing should not exceed 3 mm.

[0083] It is understandable that the first kraft paper assembly specifically includes twelve sheets of first kraft paper, which can protect the first copper foil 110 during the pre-pressing process, and prevent the first steel plate from directly contacting the first copper foil 110, thereby causing damage such as squeezing and scratching the first copper foil 110. Similarly, the second kraft paper assembly specifically includes eight sheets of second kraft paper, which can protect the first copper foil 110 during the hot pressing process, and prevent the first steel plate from directly contacting the first copper foil 110, thereby causing damage such as squeezing and scratching the first copper foil 110. In order to improve the utilization rate of kraft paper, the second kraft paper can be new kraft paper, and the second kraft paper can be old kraft paper.

[0084] It should be noted that the first kraft paper assembly specifically includes twelve sheets of first kraft paper, which is only an exemplary description of an embodiment of the present invention. The number of first kraft paper may also be one, two, or other numbers, and the present invention does not specifically limit this. Similarly, the second kraft paper assembly specifically includes eight sheets of second kraft paper, which is only an exemplary description of an embodiment of the present invention. The number of second kraft paper may also be one, two, or other numbers, and the present invention does not specifically limit this.

[0085] In some embodiments, in step S5.2, the heating rate may be controlled at 2.5°C / min, thereby allowing the temperature to rise slowly and improving the hot pressing effect.

[0086] In some embodiments, in step S5.2, the hot pressing process can be divided into 10 sub-processes, so that the hot plate temperature, hot plate time, pressure, and pressure time of each sub-process can be controlled and adjusted separately, making the regulation of the hot pressing process more flexible, and thus achieving better hot pressing effects as needed.

[0087] It should be noted that the hot pressing process is divided into 10 sub-processes. The hot plate temperature, hot plate time, pressure, and pressure time of each sub-process can refer to the following table:

[0088] Subprocess 1 2 3 4 5 6 7 8 9 10 Hot plate temperature (℃) 140 165 190 210 230 230 230 210 180 140 Hot plate time (min) 8 5 3 2 2 95 73 27 20 20 Pressure (psi) 100 200 260 370 470 470 470 370 290 220 Pressure time (min) 7 5 5 4 3 95 71 25 20 20

[0089] In some embodiments, between step S5.1 and step S5.2, the multilayer board 100 needs to be preheated by electromagnetic heat fusion, and the preheating temperature can be set to 250° C. When preheating by electromagnetic heat fusion, multiple heat fusion heads can be used, and the temperature deviation between any two heat fusion heads is controlled to be no more than 15° C.

[0090] Reference Figures 1 to 5 In some embodiments, the inner core board 130 includes four copper substrates 131 , and a prepreg layer is sandwiched between two adjacent copper substrates 131 .

[0091] The above structure is adopted to improve the electrical performance of the millimeter wave radar circuit board.

[0092] It is understandable that the inner core board 130 includes four copper substrates 131, which is only for Figures 1 to 5 As an exemplary illustration, in some embodiments, the inner core board 130 may also include two, three, five or more copper substrates 131, which is not specifically limited in the present invention.

[0093] It can be understood that when the inner core board 130 includes at least two copper substrates 131, when the inner layer circuit is produced in step S3, for the copper substrate 131 close to the first PP board 120, that is, the uppermost copper substrate 131, the upper surface is designed as a large copper surface, and the lower surface is designed as a normal inner layer circuit layout, thereby facilitating the subsequent embedding of the copper wire 160 into the mounting groove 200 so that the copper wire 160 can effectively contact with the uppermost copper substrate 131.

[0094] It is understandable that when the inner core board 130 includes at least two copper substrates 131, during the stacking process in step S4, each copper substrate 131 and the semi-cured sheet layer in the inner core board 130 needs to be stacked in sequence between the first PP board 120 and the second PP board 140.

[0095] In some embodiments, step S7 includes:

[0096] S7.1: grinding the surfaces of the first copper foil 110 and the second copper foil 150 to remove the flash at the through hole 300 and the residual glue at the mounting groove 200;

[0097] S7.2: Remove glue, remove the residual glue formed by the prepreg layer on the inner wall of the through hole 300, and remove the residual glue formed by the first PP layer between the copper wire 160 and the inner wall of the mounting groove 200;

[0098] S7.3: electroplating, forming the first copper layer 400 and the second copper layer 500 by means of horizontal copper deposition and pulse electroplating.

[0099] By adopting the above processing method, during the drilling process, flashes are likely to appear at both ends of the through hole 300, and the part of the semi-cured sheet layer located on the inner wall of the through hole 300 is likely to be carbonized or have residual glue. During the pressing process, the first PP board 120 will also be carbonized or have residual glue between the copper wire 160 and the inner wall of the mounting groove 200. Therefore, it is necessary to first grind the surfaces of the first copper foil 110 and the second copper foil 150 to remove the flashes on the surfaces of the first through hole 300 and the second through hole 300 at the through hole 300, and the residual glue of the first copper foil 110 at the opening position of the mounting groove 200, and then clean the inner wall of the through hole 300 and the mounting groove 200 through a degumming process to remove the through hole 30 0, and at the same time, the carbonized structure and residual glue formed on the inner wall of the copper wire 160 and the inner wall of the mounting groove 200 are removed, thereby facilitating the normal progress of the subsequent electroplating process, so that the first copper layer 400 can be smoothly formed on the inner wall of the through hole 300 during electroplating, and the second copper layer 500 is formed on the surface of the first copper foil 110, so that the second copper layer 500 can cover the mounting groove 200 and be embedded in the gap between the copper wire 160 and the inner wall of the mounting groove 200, so that the copper wire 160 is buried in the mounting groove 200, and the connection stability between the copper wire 160 and the inner core board 130, and the copper wire 160 and the first copper foil 110 is improved, which is conducive to achieving a better signal shielding effect.

[0100] It is understandable that, referring to Figures 1 to 5 During the electroplating process, in addition to forming the first copper layer 400 and the second copper layer 500 , a third copper layer 600 may also be formed on the surface of the second copper foil 150 .

[0101] It is understandable that in order to achieve a better electroplating effect, the first copper foil 110 may be placed downward during horizontal copper deposition.

[0102] In some embodiments, step S7.1 includes:

[0103] Belt grinding plate, the mesh number of the belt is 320#

[0104] Needle brush grinding plate, the mesh of the needle brush is 320#-540#, and the grinding plate pressure is 0.8±0.2kg / cm 2 .

[0105] By adopting the above processing method, using a sanding belt and a needle brush to grind the plate, the flash of the through hole 300 and the residual glue at the opening position of the first copper foil 110 surface mounting groove 200 can be effectively removed, especially the needle brush process can also effectively remove the flash inside the through hole 300.

[0106] Reference Figures 1 to 5In some embodiments, the thickness of the first copper foil 110 and the second copper foil 150 is 20 μm, the thickness of the first PP board 120 and the second PP board 140 is 125±12.5 μm, the width of the mounting groove 200 is 200 μm, the width of the copper wire 160 is 190 μm-200 μm, and the thickness of the copper wire 160 is 90 μm-105 μm;

[0107] In step S7.1, the surface copper removal thickness of the first copper foil 110 and the second copper foil 150 is 5-10 μm;

[0108] In step S7.2, roughening is performed by chemical debonding;

[0109] In step S7.3, the thickness of the first copper layer 400 located on the surface of the first copper foil 110 is not less than 30 μm.

[0110] In the above processing method, by setting the thickness of the first copper foil 110 and the second copper foil 150 to 20 μm, the subsequent grinding process can be ensured to proceed smoothly, and the first copper foil 110 and the second copper foil 150 can be prevented from being too thin after grinding. The depth of the mounting groove 200 is the sum of the thickness of the first PP plate 120 and the thickness of the first copper foil 110. By setting the thickness of the first PP plate 120 to 125±12.5 μm, the depth of the mounting groove 200 is 145±12.5 μm. By setting the thickness of the copper wire 160 to 90 μm-105 μm, and the width of the copper wire 160 is less than or equal to the width of the mounting groove 200, the copper wire 160 can be well embedded in the mounting groove 200.

[0111] In addition, the carbonized structure and residual glue formed on the inner wall of the through hole 300, as well as the carbonized structure and residual glue between the copper wire 160 and the inner wall of the mounting groove 200 can be effectively removed by using chemical degumming. In addition, chemical degumming can also achieve the roughening of the inner wall of the through hole 300, the surface of the copper wire 160 and the inner wall of the mounting groove 200 while removing the residual glue, which is beneficial to improve the adhesion of the copper layer in the subsequent electroplating process. Since the outer layer circuit needs to be made later, the first copper layer 400 needs to be etched when the outer layer circuit is made. Therefore, during the electroplating process, the thickness of the first copper layer 400 located on the surface of the first copper foil 110 is controlled to be not less than 30μm, that is, the thickness of the first copper layer 400 located on the surface of the first copper foil 110 is 30μm or more, which can facilitate the etching process when the outer layer circuit is made later.

[0112] It is understandable that in some embodiments, during the chemical debonding in step S7.2, the debonding amount needs to be controlled within 5-10 microinches, so that the residual glue on the inner wall of the through hole 300 and between the copper wire 160 and the mounting groove 200 can be removed as much as possible.

[0113] In some embodiments, step S8 includes:

[0114] S8.1: outer layer circuit production, producing an outer layer circuit pattern on the surface of the first copper layer 400, and setting a pattern edge compensation amount on the portion of the outer layer circuit pattern located above the copper wire 160;

[0115] S8.2: baking the multilayer board 100 at a temperature of 120° C. for 1 hour.

[0116] In the above processing method, since the outer layer circuit needs to be exposed, developed and etched when it is made, when the outer layer circuit pattern is located above the copper wire 160, it is easy to cause the first copper layer 400 to be etched through and etched to the copper wire 160 due to the existence of side etching, that is, the copper wire 160 may be etched. For this reason, when the outer layer circuit is made in step S8.1, the pattern edge compensation amount is set at the part of the outer layer circuit pattern located above the copper wire 160, thereby reducing the risk of etching the copper wire 160 due to the occurrence of side etching, etc., which is conducive to improving the signal shielding capability of the millimeter wave radar circuit board. In addition, by baking the multilayer board 100 in step S8.2, the internal stress of the multilayer board 100 can be released, reducing the risk of warping and deformation of the multilayer board 100.

[0117] It is understandable that before the outer layer circuit is made in step S8.1, the surface of the first copper foil 110 and the second copper foil 150 can be roughened to facilitate the improvement of the bonding force of the film when making the outer layer circuit. In addition, in step S8.1, an LDI exposure machine can be used for exposure, and the alignment accuracy is controlled to be 25μm. In addition, the edge compensation amount of the outer layer circuit pattern located above the copper wire 160 can be set to 2-3mil, thereby effectively reducing the risk of etching the copper wire 160 due to the occurrence of side etching, etc., which is beneficial to improve the signal shielding capability of the millimeter wave radar circuit board.

[0118] It is understandable that, referring to Figures 1 to 5 In the copper plating process of step S7, in addition to forming the first copper layer 400 and the second copper layer 500, a third copper layer 600 can also be formed on the surface of the second copper foil 150. Therefore, in step S8.1, an outer layer circuit pattern can also be made on the surface of the third copper foil.

[0119] It is understandable that the post-process of step S8 may include not only the outer layer circuit production and the baking board, but also the solder mask, electrical testing, appearance processing, etc. in the normal processing flow, and the present invention does not make specific limitations on this.

[0120] An embodiment of the present invention further provides a millimeter wave radar circuit board, which is formed by the processing method of the millimeter wave radar circuit board of any of the above embodiments.

[0121] In the millimeter wave radar circuit board of the embodiment of the present invention, by adopting the processing method of the millimeter wave radar circuit board of any of the above embodiments, signal shielding can be achieved by embedding copper wire 160. Compared with the traditional method of using blind holes to achieve signal shielding, the embedded copper wire 160 can be continuously arranged along the RF circuit pattern, thereby effectively increasing the area of ​​signal shielding, thereby improving the signal shielding effect. Secondly, since the millimeter wave radar circuit board of the embodiment of the present invention does not need to be processed by laser blind holes, it is also unnecessary to perform blackening, de-blackening, plasma degumming, hole filling electroplating, copper reduction and other processes, which greatly shortens the processing flow, thereby helping to improve the processing efficiency of the millimeter wave radar circuit board.

[0122] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A method for processing a millimeter wave radar circuit board, characterized in that: The following steps are involved: S1: Cutting the materials to obtain a first PP board (120), a second PP board (140), a first copper foil (110), a second copper foil (150), an inner core board (130) and a copper wire (160); S2: Gong material, processing a first through groove (111) on the first copper foil (110) according to the radio frequency circuit pattern, and processing a second through groove (121) on the first PP board (120) according to the radio frequency circuit pattern; S3: inner layer circuit production, producing inner layer circuit patterns on the inner core board (130); S4: stacking the boards, stacking the second copper foil (150), the second PP board (140), the inner core board (130), the first PP board (120), and the first copper foil (110) in sequence from bottom to top, the side of the inner core board (130) facing the first PP board (120) being a metal surface, the first through groove (111) being aligned with the second through groove (121), and the first through groove (111), the second through groove (121), and the upper surface of the inner core board (130) forming a mounting groove (200), and embedding the copper wire (160) into the mounting groove (200); S5: pressing the stacked multilayer boards (100); S6: drilling, processing a through hole (300) on the multilayer board (100); S7: copper plating, forming a first copper layer (400) on the surface of the first copper foil (110), wherein the first copper layer (400) covers the mounting groove (200) and is embedded between the copper wire (160) and the inner wall of the mounting groove (200), and forming a second copper layer (500) on the inner wall of the through hole (300); S8: Post-process.

2. The method for processing a millimeter wave radar circuit board according to claim 1, characterized in that: Between step S3 and step S4, browning is also included, wherein the copper wire (160) and the inner core board (130) are browned, and the amount of copper bitten by browning is 1.4 μm-1.8 μm. After browning, the surface roughness Rz value of the copper wire (160) and the inner core board (130) is 3±1 μm, and the Ra value is 0.4±0.2 μm.

3. The method for processing a millimeter wave radar circuit board according to claim 2, characterized in that: When the copper wire (160) is subjected to browning treatment, the copper wire (160) is fixed on a tray and passed through a browning line at a browning line speed of 1.0 m / min. After browning, the copper wire (160) is dried at a drying temperature of 90±5°C.

4. The method for processing a millimeter wave radar circuit board according to claim 1, characterized in that: The step S5 comprises: S5.1: pre-pressing, sequentially covering the first copper foil (110) with a first kraft paper assembly and a first steel plate, and pre-pressing the stacked copper wire (160), the second copper foil (150), the second PP plate (140), the inner core plate (130), the first PP plate (120), and the first copper foil (110) through the first steel plate; S5.2: Hot pressing: sequentially cover the first copper foil (110) with a second kraft paper assembly and a second steel plate, and hot press the stacked second steel plate, the second kraft paper assembly, the copper wire (160), the second copper foil (150), the second PP board (140), the inner core board (130), the first PP board (120), and the first copper foil (110), with a heating rate of 2.5°C / min. S5.3: cold pressing the stacked second steel plate, the second kraft paper assembly, the copper wire (160), the second copper foil (150), the second PP plate (140), the inner core plate (130), the first PP plate (120), and the first copper foil (110), with a cold pressing pressure of 30 bar and a cold pressing time of 45 minutes.

5. The method for processing a millimeter wave radar circuit board according to claim 1, characterized in that: The inner core board (130) comprises at least two copper base boards (131), all of the copper base boards (131) are stacked in sequence, and a prepreg layer is sandwiched between two adjacent copper base boards (131).

6. The method for processing a millimeter wave radar circuit board according to claim 5, characterized in that: The step S7 comprises: S7.1: grinding the surfaces of the first copper foil (110) and the second copper foil (150) to remove the flash at the through hole (300) and the residual glue at the mounting groove (200); S7.2: removing adhesive residues formed by the prepreg layer on the inner wall of the through hole (300), and removing adhesive residues formed by the first PP layer between the copper wire (160) and the inner wall of the mounting groove (200); S7.3: electroplating, forming the first copper layer (400) and the second copper layer (500) by means of horizontal copper deposition and pulse electroplating.

7. The method for processing a millimeter wave radar circuit board according to claim 6, characterized in that: The step S7.1 comprises: Abrasive belt grinding plate, the mesh number of the abrasive belt is 320# Needle brush grinding plate, the mesh number of the needle brush is 320#-540#, and the grinding plate pressure is 0.8±0.2kg / cm2.

8. The method for processing a millimeter wave radar circuit board according to claim 7, characterized in that: The thickness of the first copper foil (110) and the second copper foil (150) is 20 μm, the thickness of the first PP board (120) and the second PP board (140) is 125±12.5 μm, the width of the mounting groove (200) is 200 μm, the width of the copper wire (160) is 190 μm-200 μm, and the thickness of the copper wire (160) is 90 μm-105 μm; In the step S7.1, the surface copper removal thickness of the first copper foil (110) and the second copper foil (150) is 5-10 μm; In the step S7.2, roughening is performed by chemical degumming; In the step S7.3, the thickness of the first copper layer (400) located on the surface of the first copper foil (110) is not less than 30 μm.

9. The method for processing a millimeter wave radar circuit board according to claim 1, characterized in that: The step S8 comprises: S8.1: outer layer circuit production, producing an outer layer circuit pattern on the surface of the first copper layer (400), and setting a pattern edge compensation amount at a portion of the outer layer circuit pattern located above the copper wire (160); S8.2: baking the multilayer board (100) at a temperature of 120° C. for 1 hour.

10. A millimeter wave radar circuit board, characterized in that: The millimeter wave radar circuit board is formed by the processing method of any one of claims 1 to 9.

Images