A method for preparing millimeter wave radar circuit board based on pulse electroplating

Abstract

The present invention relates to the technical field of radar circuit board preparation, and in particular to a method for preparing a millimeter-wave radar circuit board based on pulse electroplating, comprising: performing pulse electroplating copper plating on a semi-finished printed circuit board, determining whether the bubble density variation trend is consistent based on a second quantity ratio of bubble density curves in several regions, and determining a method for determining the eligibility of the copper plating process based on the determination result; obtaining the rate matching degree of the copper plating process to determine the eligibility of the copper plating process, or, for several bubble distribution regions, obtaining the average residence time of the bubbles to determine the eligibility of the copper plating process; adjusting the angle between the axis of the electrolyte nozzle and the axis of the blind hole or the electrolyte nozzle pressure based on the pulsating speed; determining the copper distribution deviation within the blind hole, and optimizing the second preset ratio or the preset pulsating speed based on the copper distribution deviation. The present invention improves the copper plating quality within the blind hole.

Description

Technical Field

[0001] The present invention relates to the technical field of radar circuit board preparation, and in particular to a method for preparing a millimeter-wave radar circuit board based on pulse electroplating. Background Art

[0002] Millimeter-wave radar, as a core sensor for autonomous driving and intelligent transportation systems, places stringent demands on the dielectric properties, signal integrity, and thermal reliability of PCBs for its high-frequency signal transmission performance. Traditional DC electroplating processes face multiple challenges in millimeter-wave radar circuit board manufacturing: blind via copper filling is prone to dents and copper powder contamination, resulting in reduced antenna etching accuracy; the mixed-pressure stacking structure of high-frequency board and FR-4 is prone to warping due to thermal expansion coefficient mismatch, affecting the stability of the antenna pattern; and the surface roughness of traditional electroplated copper layers exacerbates signal scattering, resulting in excessive phase accuracy deviations in the millimeter-wave band, making it impossible to meet the millimeter-level detection accuracy requirements of 4D imaging radars. Therefore, it is urgent to develop a pulse electroplating-based process that dynamically controls current density to suppress concentration polarization and reduce copper ion concentration gradient fluctuations. Simultaneously, combining low-roughness copper foil with a ceramic filling substrate can achieve high-precision blind via filling and low-loss transmission of high-frequency signals.

[0003] Chinese patent application publication number CN111491466A discloses a method for preparing a 77GHz millimeter-wave radar circuit board, comprising the following steps: separately fabricating L1-L2, L3-L4, and L5-L6 layers; sequentially laminating the three layers to form a composite board; sequentially subjecting the composite board to guillotine treatment, first copper reduction and browning, first outer dry film coating, acid etching, laser blind via treatment, second outer dry film coating, and pattern electroplating, followed by post-processing according to conventional circuit board processing procedures; the laser blind via treatment includes, in sequence, first drilling, first copper plate electroplating, second copper reduction and browning, resin plugging, second drilling, and second copper plate electroplating. This invention utilizes the laser blind via processing steps of first drilling, first copper plate electroplating, second copper reduction and browning, resin plugging, second drilling, and second copper plate electroplating, using a windowed laser method to reduce the difficulty of copper reduction and improve copper reduction accuracy, thereby improving quality and reducing defects.

[0004] The following problems also exist in the existing technology: in the preparation process of millimeter-wave radar circuit boards in the existing technology, due to the large thickness-to-diameter ratio of the blind hole, the electrolyte can easily form a laminar retention area in the blind hole, causing an imbalance in the copper ion concentration gradient, and then causing the copper at the bottom of the hole to be thin, resulting in low copper plating quality in the blind hole. Summary of the Invention

[0005] To this end, the present invention provides a method for preparing a millimeter-wave radar circuit board based on pulse electroplating, so as to overcome the problem of low copper plating quality in blind holes caused by the large aspect ratio of the blind holes in the prior art.

[0006] To achieve the above objectives, the present invention provides a method for preparing a millimeter wave radar circuit board based on pulse electroplating, comprising:

[0007] Pulse electroplating copper is performed on a semi-finished printed circuit board, and a ratio of the number of bubble density curves with the same change trend in several cathode regions during the copper deposition stage to a second number of the total number is obtained to determine whether the change trend of the bubble density is consistent;

[0008] Obtaining the copper thickness growth rate in the copper deposition stage and the copper thickness reduction rate in the copper dissolution stage to determine rate matching, and determining the eligibility of the copper plating process based on the rate matching, or, for several bubble distribution areas, obtaining the average residence time of the bubbles to determine the eligibility of the copper plating process;

[0009] Under the condition that the copper plating process is qualified, the pulsation speed of the electrolyte in the blind hole is determined to adjust the angle between the axis of the electrolyte nozzle and the axis of the blind hole or the pressure of the electrolyte nozzle;

[0010] The quality inspection cycle of the finished printed circuit board is determined based on the recovery time of the copper ion concentration in the electrolyte, and the copper distribution deviation in the blind hole is determined based on the random sampling inspection results of several inspection cycles. Based on the copper distribution deviation, the judgment basis of the change trend of the bubble density or the comparison basis of the pulsation speed is optimized.

[0011] Furthermore, during the copper deposition stage, the process of determining the consistency of the changing trend of the cathode bubble density in several regions includes:

[0012] Acquiring a plurality of frames of images for a single region to establish a bubble density curve according to the bubble density of the single frame images;

[0013] Dividing the single bubble density curve into a plurality of curve segments based on the coordinate nodes of the abscissa axis;

[0014] comparing the plurality of bubble density curves respectively based on the curve segment;

[0015] Determining curve segments with consistent slopes as having consistent change trends, and determining a plurality of bubble density curves as having consistent change trends based on a comparison result that the first quantity ratio is greater than or equal to a first preset ratio;

[0016] Determining that the change trends of the bubble densities of the cathode bubbles are consistent based on a comparison result that the second number ratio is greater than or equal to the second preset ratio;

[0017] Determining that the change trend of the bubble density of the cathode bubbles is inconsistent based on a comparison result that the second number proportion is less than the second preset proportion;

[0018] Among them, the first number proportion is the ratio of the number of curve segments with consistent change trends to the total number of curve segments of the corresponding bubble density curve, and the second number proportion is the ratio of the number of the bubble density curves with consistent change trends to the total number of the bubble density curves.

[0019] Furthermore, under the condition that the change trend of the bubble density is determined to be consistent, the process of determining the eligibility of the copper plating process based on the rate matching degree includes:

[0020] The ratio of the copper thickness growth rate in the copper deposition stage to the copper thickness reduction rate in the copper dissolution stage of the copper plating process is determined as the rate matching degree;

[0021] Comparing the rate matching degree with the preset matching degree respectively;

[0022] The copper plating process is determined to be qualified based on a comparison result that the rate matching degree is less than or equal to the first preset matching degree and greater than or equal to the second preset matching degree.

[0023] Furthermore, under the condition that the change trend of the bubble density is determined to be inconsistent, the process of determining the eligibility of the copper plating process according to the average residence time of the bubbles includes:

[0024] Acquire several frames of images for a single area to determine the average residence time of the bubble;

[0025] Comparing the average length of stay with a preset length of stay;

[0026] Determining that the average residence time of the bubbles in a single area is qualified based on a comparison result that the average residence time is less than or equal to the preset time;

[0027] Determine a third ratio of regions having a qualified average length of stay and compare the ratio with a third preset ratio;

[0028] The copper plating process is determined to be qualified based on a comparison result that the third quantity proportion is greater than or equal to the third preset proportion.

[0029] Furthermore, under the condition that the copper plating process is determined to be qualified, the process of adjusting the axis angle according to the pulsation speed of the electrolyte in the blind hole includes:

[0030] comparing the pulsation speed with a preset pulsation speed respectively;

[0031] Determining to reduce the axis angle based on a comparison result that the pulsation speed is greater than a first preset pulsation speed;

[0032] Among them, the axis angle is the angle between the nozzle axis and the blind hole axis, the pulsating speed is subtracted from the first preset pulsating speed to obtain a first speed difference, and several angle adjustment coefficients corresponding to the first speed difference are set to reduce the axis angle according to the angle adjustment coefficient.

[0033] Furthermore, under the condition that the copper plating process is determined to be qualified, the process of determining and adjusting the nozzle pressure of the electrolyte according to the pulsation speed of the electrolyte in the blind hole includes:

[0034] comparing the pulsation speed with a preset pulsation speed respectively;

[0035] Determining to increase the nozzle pressure based on a comparison result that the pulsation speed is less than a second preset pulsation speed;

[0036] The second preset pulsating speed is subtracted from the pulsating speed to obtain a second speed difference, and a plurality of pressure adjustment coefficients corresponding to the second speed difference are set to increase the nozzle pressure according to the pressure adjustment coefficients.

[0037] Furthermore, the process of determining the recovery time of the copper ion concentration includes:

[0038] Monitor the copper ion concentration of the electrolyte in real time and establish an ion concentration curve;

[0039] On the ion concentration curve, a horizontal line is established parallel to the abscissa axis with the preset ion concentration as the ordinate;

[0040] An average of time differences between a plurality of intersection points of the horizontal line and the ion concentration curve is determined, and the average of the time differences is determined as the recovery duration.

[0041] Furthermore, the quality inspection cycle of the finished printed circuit board is determined according to the recovery time. For a single inspection cycle, the process of determining the copper distribution deviation in the blind via includes:

[0042] Determine, for a single blind hole, a first area ratio where the copper thickness is greater than a first preset copper thickness and a second area ratio where the copper thickness is less than a second preset copper thickness;

[0043] Determining an absolute difference in area between the first area ratio and the second area ratio;

[0044] Determine the standard deviation of several absolute area differences for a single test, and determine the standard deviation as the copper distribution deviation,

[0045] Furthermore, the process of determining and optimizing the second preset proportion according to the copper distribution deviation includes:

[0046] comparing the copper distribution deviation with a preset deviation;

[0047] Determining to optimize the second preset proportion based on a comparison result that the copper distribution deviation is greater than the preset deviation;

[0048] Determining a first deviation value between the copper distribution deviation and the preset deviation;

[0049] A plurality of proportion optimization coefficients corresponding to the first deviation value are set to increase the second preset proportion according to the proportion optimization coefficients.

[0050] Furthermore, the process of determining and optimizing the preset pulsation speed according to the copper distribution deviation includes:

[0051] comparing the copper distribution deviation with a preset deviation;

[0052] Determining to optimize the preset pulsation speed based on a comparison result that the copper distribution deviation is less than or equal to the preset deviation;

[0053] Determining a second deviation value between the preset deviation and the copper distribution deviation;

[0054] A plurality of speed optimization coefficients corresponding to the second deviation value are set to respectively reduce the first preset pulsation speed and increase the second preset pulsation speed according to the speed optimization coefficients.

[0055] Compared with the prior art, the present invention has the following beneficial effects: the present invention divides the semi-finished printed circuit board into several areas, and determines the eligibility of the copper plating process based on the consistency of the change trend of the bubble density. In the copper plating process, the consistency of the change trend of the bubble density is the core indicator for evaluating the stability of the copper plating process and the quality of the coating. The change of the bubble density reflects the dynamic balance between the electrochemical reaction rate and the gas precipitation in the plating solution. If the change trend of the bubble density in each area suddenly changes, it indicates that at least one copper plating parameter deviates from the set value and needs to be adjusted; the determination method for the eligibility of the copper plating process is determined based on the determination result of the consistency of the bubble density trend, the overall copper thickness is determined if the consistency is qualified, and the thickness is determined if the consistency is unqualified. The qualification of the copper plating process is determined according to the judgment results of each area, thereby improving the judgment efficiency while ensuring the judgment accuracy; the state of the electrolyte in the blind hole is determined based on the qualified judgment result of the overall copper plating process, and the copper plating quality in the blind hole is further determined, and the unqualified situation is accurately adjusted, thereby further improving the copper plating quality of the printed circuit board; the quality inspection period is determined according to the recovery time of the copper ion concentration. If the recovery time of the copper ion concentration is too long or too short, the copper plating quality will be reduced. In view of this situation, the inspection period is shortened, and the judgment standard of the change trend of the bubble density is improved according to the periodic inspection results, or the judgment standard of the copper plating quality in the blind hole is improved, thereby further improving the copper plating quality in the blind hole of the printed circuit board.

[0056] Furthermore, the present invention determines the changing trend of the bubble density by performing segmented comparison on the bubble density curves in the copper deposition stage. During the copper plating process, the bubble density will show regular changes with the increase of the copper plating time. The changing patterns of several areas are compared with each other to determine whether the changing trends of the bubble density are consistent, thereby improving the judgment benchmark of the overall copper plating process and further improving the copper plating quality in the blind holes of the printed circuit board.

[0057] Furthermore, the present invention determines the eligibility of the copper plating process according to the rate matching degree. During the copper plating process of the printed circuit board, the forward current density and the reverse current density are alternately performed, the forward current density increases the copper thickness, and the reverse current density reduces the copper thickness. The mismatch between the rate of increase of the copper thickness and the rate of decrease of the copper thickness will lead to unqualified thickness of the overall coating or unqualified roughness of the coating. The overall copper plating quality is judged according to the rate matching degree, which improves the accuracy of the overall quality judgment, thereby further improving the copper plating quality in the blind hole of the printed circuit board.

[0058] Furthermore, the present invention determines the quality of regional copper plating by the mean residence time of the bubbles. If the bubble residence time is too long, defects such as pitting will appear on the copper-plated surface. The copper plating quality of the local area is determined according to the mean residence time of the bubbles, and the quality of the copper plating process is determined according to the statistical results of the regional copper plating quality, thereby improving the accuracy of the copper plating quality judgment and further improving the copper plating quality in the blind holes of the printed circuit board.

[0059] Furthermore, the present invention determines the copper plating quality in the blind hole by the pulsating speed of the electrolyte in the blind hole. An appropriate pulsating speed can enhance the exchange rate of copper ions inside and outside the blind hole and alleviate concentration polarization. An excessively high pulsating speed will destroy the steady state of the plating solution in the blind hole, resulting in local supersaturation of copper ions, triggering reverse current to break through the plating layer, forming protrusions or voids. An excessively low pulsating speed will cause inhibitors to accumulate at the hole mouth, inhibit deposition on the hole wall, and form depressions. The pulsating speed is monitored so that targeted adjustments can be made according to the situation where the pulsating speed is too high or too low, thereby further improving the copper plating quality in the blind hole of the printed circuit board.

[0060] Furthermore, the present invention improves the criterion for judging the changing trend of bubble density under the condition of large copper distribution deviation, and improves the criterion for judging the quality of copper plating in blind holes under the condition of small copper distribution deviation. The judgment of the acceptability of the copper plating process or the judgment of the quality of copper plating in blind holes is essentially a judgment of the fluidity of the electrolyte. When the changing trend of the bubble density is inconsistent, it indicates that the overall flow of the electrolyte is uneven and there is a stagnant area, which causes an imbalance in the copper ion concentration gradient and is more likely to cause low copper plating quality in the blind holes. Under the condition that the overall flow uniformity of the electrolyte is acceptable, the criterion for judging the pulsation speed of the electrolyte in the blind holes is improved, and the criterion for judging the quality of copper plating in the blind holes is more targeted, thereby further improving the copper plating quality in the blind holes of the printed circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 This is a flow chart of a method for preparing a millimeter-wave radar circuit board based on pulse electroplating according to an embodiment of the present invention;

[0062] Figure 2 A flow chart showing the consistency of a change trend of the bubble density of cathode bubbles according to an embodiment of the present invention;

[0063] Figure 3 A flow chart of determining the eligibility of a copper plating process based on rate matching according to an embodiment of the present invention;

[0064] Figure 4 This is a flow chart of determining the eligibility of a copper plating process based on the mean residence time of bubbles in an embodiment of the present invention. DETAILED DESCRIPTION

[0065] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0066] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0067] See also Figure 1-Figure 4 As shown, Figure 1 This is a flow chart of a method for preparing a millimeter-wave radar circuit board based on pulse electroplating according to an embodiment of the present invention; Figure 2 A flow chart showing the consistency of a change trend of the bubble density of cathode bubbles according to an embodiment of the present invention; Figure 3 A flow chart of determining the eligibility of a copper plating process based on rate matching according to an embodiment of the present invention; Figure 4 This is a flow chart of determining the eligibility of a copper plating process based on the mean residence time of bubbles in an embodiment of the present invention.

[0068] An embodiment of the present invention provides a method for preparing a millimeter wave radar circuit board based on pulse electroplating, comprising:

[0069] Step S1, after the substrate is surface cleaned, inner layer pattern processing, multilayer board lamination, drilling, chemical copper deposition and outer layer pattern transfer processing are sequentially performed to obtain a semi-finished printed circuit board;

[0070] Step S2, performing pulse electroplating copper plating on the semi-finished printed circuit board, obtaining a second ratio of the number of bubble density curves with the same change trend in a plurality of cathode regions during the copper deposition stage to the total number to determine whether the change trend of the bubble density is consistent;

[0071] Step S3, obtaining the copper thickness growth rate in the copper deposition stage and the copper thickness reduction rate in the copper dissolution stage to determine rate matching, and determining the eligibility of the copper plating process based on the rate matching, or, for several bubble distribution areas, obtaining the average residence time of the bubbles to determine the eligibility of the copper plating process;

[0072] Step S4, determining a pulsation speed of the electrolyte in the blind hole based on the result of determining that the copper plating process is qualified, and adjusting an angle between an axis of the electrolyte nozzle and an axis of the blind hole or a pressure of the electrolyte nozzle according to a comparison result of the pulsation speed with a preset pulsation speed;

[0073] Step S5: determining a quality inspection cycle of the finished printed circuit board according to the recovery time of the copper ion concentration in the electrolyte, determining the copper distribution deviation in the blind hole based on the random sampling inspection results of several inspection cycles, and optimizing the second preset proportion or optimizing the preset speed based on the copper distribution deviation.

[0074] Specifically, the processes of substrate surface cleaning, inner layer pattern processing, multilayer board lamination, drilling, chemical copper deposition and outer layer pattern transfer are all existing technologies and will not be described in detail here.

[0075] Specifically, the area division basis of the printed circuit board surface can be divided according to the distribution density of the holes, for example, the distribution density of the holes is 10 / cm 2 The regions are divided based on the criteria without any specific limitation.

[0076] Specifically, during the copper deposition stage, the process of determining the consistency of the changing trend of the cathode bubble density in several regions includes:

[0077] Acquiring a plurality of frames of images for a single region to establish a bubble density curve according to the bubble density of the single frame images;

[0078] Dividing the single bubble density curve into a plurality of curve segments based on the coordinate nodes of the abscissa axis;

[0079] comparing the plurality of bubble density curves respectively based on the curve segment;

[0080] Determining curve segments with consistent slopes as having consistent change trends, and determining a plurality of bubble density curves as having consistent change trends based on a comparison result that the first quantity ratio is greater than or equal to a first preset ratio;

[0081] Determining that the change trends of the bubble densities of the cathode bubbles are consistent based on a comparison result that the second number ratio is greater than or equal to the second preset ratio;

[0082] Determining that the change trend of the bubble density of the cathode bubbles is inconsistent based on a comparison result that the second number proportion is less than the second preset proportion;

[0083] Among them, the first number proportion is the ratio of the number of curve segments with consistent change trends to the total number of curve segments of the corresponding bubble density curve, and the second number proportion is the ratio of the number of the bubble density curves with consistent change trends to the total number of the bubble density curves.

[0084] Specifically, the first preset proportion and the second preset proportion are determined according to the historical copper plating process, the value range of the first preset proportion is set to [60%, 80%], and 70% is preferred in the embodiment of the present invention; the value range of the first preset proportion is set to [70%, 90%], and 80% is preferred in the embodiment of the present invention.

[0085] Specifically, under the condition that the change trend of the bubble density is consistent, the process of determining the eligibility of the copper plating process based on the rate matching degree includes:

[0086] The ratio of the copper thickness growth rate in the copper deposition stage to the copper thickness reduction rate in the copper dissolution stage of the copper plating process is determined as the rate matching degree;

[0087] Comparing the rate matching degree with the preset matching degree respectively;

[0088] Determining that the copper plating process is qualified based on a comparison result that the rate matching degree is less than or equal to the first preset matching degree and greater than or equal to the second preset matching degree;

[0089] The copper plating process is determined to be unqualified based on a comparison result that the rate matching degree is greater than a first preset matching degree or less than a second preset matching degree.

[0090] Specifically, the preset matching degree is a value corresponding to the mode of the qualified rate matching degrees of the copper plating process in the historical copper plating process. The specific value range is set to [2.5, 5], and 3 is preferred in the embodiment of the present invention.

[0091] It can be understood that during the copper plating process, forward current and reverse current are carried out alternately. A large rate matching degree indicates that the copper deposition rate caused by the forward current is too fast or that the copper deposition ablation rate caused by the reverse current is too slow. Too fast a copper deposition rate will lead to insufficient replenishment of copper ions in the hole, resulting in the copper layer at the bottom of the hole being too thin or even no copper. The copper deposition ablation rate is too slow to effectively defoam and dissolve the pore mouth oxide, resulting in increased surface roughness of the copper deposition and decreased uniformity of the copper deposition thickness.

[0092] Under the condition that the trend of bubble density change is inconsistent, the process of determining the eligibility of the copper plating process according to the mean value of the bubble residence time includes:

[0093] Acquire several frames of images for a single area to determine the average residence time of the bubble;

[0094] Comparing the average length of stay with a preset length of stay;

[0095] Determining that the average residence time of the bubbles in a single area is qualified based on a comparison result that the average residence time is less than or equal to the preset time;

[0096] Determining that the average residence time of the bubbles in a single area is unqualified based on a comparison result that the average residence time is greater than the preset time;

[0097] Determine a third ratio of regions having a qualified average length of stay and compare the ratio with a third preset ratio;

[0098] Determining that the copper plating process is qualified based on a comparison result that the third quantity ratio is greater than or equal to the third preset ratio;

[0099] The copper plating process is determined to be unqualified based on a comparison result that the third quantity ratio is less than the third preset ratio.

[0100] Specifically, the preset duration is determined based on the premise that the residence time of the bubbles does not affect the copper plating quality, and the specific value range is set to [2s, 5s]. In the embodiment of the present invention, 3s is preferred.

[0101] Specifically, the value of the third preset proportion is determined according to the historical copper plating quality process, and the specific value range is set to [80%, 95%]. The preferred value in the embodiment of the present invention is 90%.

[0102] Specifically, under the condition that the copper plating process is determined to be unqualified, the process of determining and adjusting the vacuum assist time before copper plating according to the bubble density of the cathode includes:

[0103] comparing the bubble density with a predetermined density;

[0104] Determining to increase the vacuum assist time based on a comparison result that the bubble density is greater than the preset density;

[0105] Subtracting the bubble density from the preset density to obtain a density difference;

[0106] A plurality of duration adjustment coefficients corresponding to the density difference are provided to increase the vacuum assist duration according to the duration adjustment coefficients.

[0107] Specifically, the preset density is the average bubble density of cathodes that have passed the historical copper plating process, and the specific value range is set to [10 / cm 2 , 100 pieces / cm 2 ], the embodiment of the present invention preferably has 50 pieces / cm 2 .

[0108] Specifically, comparing the first density difference value with a preset density difference value;

[0109] determining, based on a comparison result that the first density difference is greater than the preset density difference, to increase the vacuum assist duration by a first duration adjustment coefficient;

[0110] Based on a comparison result that the first density difference is less than or equal to the preset density difference, it is determined to increase the vacuum assist duration by a second duration adjustment coefficient.

[0111] Specifically, the range of the preset density difference is set to [5 / cm 2 , 20 pieces / cm 2 ], the embodiment of the present invention preferably has 10 / cm 2 ; The value range of the first duration adjustment coefficient is set to [1.5, 2], and the preferred embodiment of the present invention is 1.8; the value range of the second duration adjustment coefficient is set to [1.1, 4], and the preferred embodiment of the present invention is 1.3.

[0112] Specifically, under the condition that the copper plating process is determined to be qualified, the process of determining the adjustment axis angle according to the pulsation speed of the electrolyte in the blind hole includes:

[0113] comparing the pulsation speed with a preset pulsation speed respectively;

[0114] Determining to reduce the axis angle based on a comparison result that the pulsation speed is greater than a first preset pulsation speed;

[0115] Among them, the axis angle is the angle between the nozzle axis and the blind hole axis, the pulsating speed is subtracted from the first preset pulsating speed to obtain a first speed difference, and several angle adjustment coefficients corresponding to the first speed difference are set to reduce the axis angle according to the angle adjustment coefficient.

[0116] It can be understood that the pulsating speed is the random fluctuation component of the instantaneous speed, that is, the deviation between the instantaneous speed and the average speed.

[0117] Specifically, under the condition that the copper plating process is determined to be qualified, the process of determining and adjusting the nozzle pressure of the electrolyte according to the pulsation speed of the electrolyte in the blind hole includes:

[0118] comparing the pulsation speed with a preset pulsation speed respectively;

[0119] Determining to increase the nozzle pressure based on a comparison result that the pulsation speed is less than a second preset pulsation speed;

[0120] The second preset pulsating speed is subtracted from the pulsating speed to obtain a second speed difference, and a plurality of pressure adjustment coefficients corresponding to the second speed difference are set to increase the nozzle pressure according to the pressure adjustment coefficients.

[0121] Specifically, the values ​​of the first preset pulsating speed and the second preset pulsating speed are determined according to the historical copper plating process with qualified copper plating quality. The value range of the first preset pulsating speed is set to [5 cm / s, 8 cm / s], and 7 cm / s is preferred in the embodiment of the present invention; the value range of the second preset pulsating speed is set to [2 cm / s, 4 cm / s], and 3 cm / s is preferred in the embodiment of the present invention.

[0122] It is understandable that when the pulsation speed is too large, the axis angle needs to be reduced. When the angle between the nozzle axis and the blind hole axis decreases, the jet direction is closer to vertical, which can reduce the lateral impact force and the turbulence intensity in the blind hole. The pulsation speed will decrease as the turbulence intensity decreases; when the pulsation speed is too small, the nozzle pressure needs to be increased to increase the pulsation speed.

[0123] Specifically, comparing the first speed difference with a preset difference;

[0124] Determining to reduce the axis angle by a first angle adjustment coefficient based on a comparison result that the first speed difference is greater than or equal to the preset difference;

[0125] Based on the comparison result that the first speed difference is less than the preset difference, it is determined to reduce the axis angle by a second angle adjustment coefficient.

[0126] Specifically, the value range of the preset difference is set to [0.5 cm / s, 1.5 cm / s], and the embodiment of the present invention is preferably 0.8 cm / s; the value range of the first angle adjustment coefficient is set to [0.6, 0.8], and the embodiment of the present invention is preferably 0.75; the value range of the second angle adjustment coefficient is set to [0.81, 0.92], and the embodiment of the present invention is preferably 0.85.

[0127] Specifically, comparing the second speed difference with the preset difference;

[0128] determining to increase the nozzle pressure by a first pressure adjustment coefficient based on a comparison result that the second speed difference is greater than or equal to the preset difference;

[0129] Based on the comparison result that the second speed difference is less than the preset difference, it is determined to increase the nozzle pressure by a second pressure adjustment coefficient.

[0130] Specifically, the value range of the first pressure adjustment coefficient is set to [1.3, 1.5], and preferably 1.4 in the embodiment of the present invention; the value range of the second pressure adjustment coefficient is set to [1.1, 1.29], and preferably 1.2 in the embodiment of the present invention.

[0131] Specifically, the process of determining the recovery time of the copper ion concentration includes:

[0132] Monitor the copper ion concentration of the electrolyte in real time and establish an ion concentration curve;

[0133] On the ion concentration curve, a horizontal line is established parallel to the abscissa axis with the preset ion concentration as the ordinate;

[0134] An average of time differences between a plurality of intersection points of the horizontal line and the ion concentration curve is determined, and the average of the time differences is determined as the recovery duration.

[0135] It is understandable that during the copper plating process of printed circuit boards, as the forward current density continues, the copper ions in the electrolyte will undergo a reduction reaction and adhere to the surface of the board, and the concentration will gradually decrease. At the same time, the anode is also continuously providing copper ions, so the copper ion concentration will fluctuate over time. When the electrolyte circulates or is insufficiently replenished, the recovery time of the copper ion concentration will be too long. When the recovery time is too short, the copper ions are not consumed in time, which will cause the copper ion reduction rate to exceed the surface atomic migration rate, forming dendritic crystals and reducing the bonding strength of the coating.

[0136] Specifically, the quality inspection cycle of the finished printed circuit board is determined according to the recovery time. For a single inspection cycle, the process of determining the copper distribution deviation in the blind via includes:

[0137] Determine, for a single blind hole, a first area ratio where the copper thickness is greater than a first preset copper thickness and a second area ratio where the copper thickness is less than a second preset copper thickness;

[0138] Determining an absolute difference in area between the first area ratio and the second area ratio;

[0139] The standard deviation of several of the absolute differences in area is determined for a single test, and the standard deviation is determined as the copper distribution deviation.

[0140] Specifically, the quality inspection cycle of the printed circuit board is negatively correlated with the recovery time, and the specific inspection cycle is determined according to the required accuracy of copper plating of the circuit board.

[0141] Specifically, the value range of the first preset copper thickness is set to [22μm, 25μm], and 23μm is preferred in the embodiment of the present invention; the value range of the second preset copper thickness is set to [18μm, 20μm], and 18μm is preferred in the embodiment of the present invention.

[0142] Specifically, the process of determining and optimizing the second preset proportion according to the copper distribution deviation includes:

[0143] comparing the copper distribution deviation with a preset deviation;

[0144] Determining to optimize the second preset proportion based on a comparison result that the copper distribution deviation is greater than the preset deviation;

[0145] Determining a first deviation value between the copper distribution deviation and the preset deviation;

[0146] A plurality of proportion optimization coefficients corresponding to the first deviation value are set to optimize the second preset proportion according to the proportion optimization coefficients.

[0147] Specifically, the process of determining and optimizing the preset pulsation speed according to the copper distribution deviation includes:

[0148] comparing the copper distribution deviation with a preset deviation;

[0149] Determining to reduce the preset pulsation speed based on a comparison result that the copper distribution deviation is less than or equal to the preset deviation;

[0150] Determining a second deviation value between the preset deviation and the copper distribution deviation;

[0151] A plurality of speed optimization coefficients corresponding to the second deviation value are set to respectively reduce the first preset pulsation speed and increase the second preset pulsation speed according to the speed optimization coefficients.

[0152] Specifically, comparing the first deviation value with a preset deviation value;

[0153] Determining, based on a comparison result that the first deviation value is greater than or equal to the preset deviation value, to increase the second preset proportion by a first proportion optimization coefficient;

[0154] Based on a comparison result that the first deviation value is less than the preset deviation value, it is determined to increase the second preset proportion by a second proportion optimization coefficient.

[0155] Specifically, comparing the second deviation value with a preset deviation value;

[0156] Based on a comparison result that the second deviation value is greater than or equal to the preset deviation value, determining to reduce the first preset pulsation speed by a first speed optimization coefficient and to increase the second preset pulsation speed by a second speed optimization coefficient;

[0157] Based on the comparison result that the second deviation value is less than the preset deviation value, it is determined to reduce the first preset pulsation speed by a third speed optimization coefficient and to increase the second preset pulsation speed by a fourth speed optimization coefficient.

[0158] Specifically, the value range of the preset deviation is set to [0.5, 1.2], and the preferred embodiment of the present invention is 0.8; the value range of the preset deviation value is set to [0.1, 0.4], and the preferred embodiment of the present invention is 0.2.

[0159] Specifically, the value range of the first proportion optimization coefficient is set to [1.1, 1.2], and the embodiment of the present invention preferably sets it to 1.15; the value range of the second proportion optimization coefficient is set to [1.01, 1.09], and the embodiment of the present invention preferably sets it to 1.05; the value range of the first speed optimization coefficient is set to [0.91, 0.93], and the embodiment of the present invention preferably sets it to 0.92; the value range of the second speed optimization coefficient is set to [1.04, 1.07], and the embodiment of the present invention preferably sets it to 1.06; the value range of the third speed optimization coefficient is set to [0.94, 0.98], and the embodiment of the present invention preferably sets it to 0.95; the value range of the fourth speed optimization coefficient is set to [1.02, 1.03], and the embodiment of the present invention preferably sets it to 1.02.

[0160] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A method for preparing a millimeter wave radar circuit board based on pulse electroplating, characterized in that: include: Pulse electroplating copper is performed on a semi-finished printed circuit board, and a ratio of the number of bubble density curves with the same change trend in several cathode regions during the copper deposition stage to a second number of the total number is obtained to determine whether the change trend of the bubble density is consistent; Obtaining the copper thickness growth rate in the copper deposition stage and the copper thickness reduction rate in the copper dissolution stage to determine rate matching, and determining the eligibility of the copper plating process based on the rate matching, or, for several bubble distribution areas, obtaining the average residence time of the bubbles to determine the eligibility of the copper plating process; Under the condition that the copper plating process is qualified, the pulsation speed of the electrolyte in the blind hole is determined to adjust the angle between the axis of the electrolyte nozzle and the axis of the blind hole or the pressure of the electrolyte nozzle; Determining a quality inspection cycle for a finished printed circuit board based on the recovery time of the copper ion concentration in the electrolyte, determining a copper distribution deviation within the blind via based on random sampling test results from several inspection cycles, and optimizing a determination benchmark for a change trend in bubble density or a comparison benchmark for the pulsation speed based on the copper distribution deviation; During the copper deposition stage, the process of determining the consistency of the changing trend of the cathode bubble density in several regions includes: Acquiring a plurality of frames of images for a single region to establish a bubble density curve according to the bubble density of the single frame images; Dividing the single bubble density curve into a plurality of curve segments based on the coordinate nodes of the abscissa axis; comparing the plurality of bubble density curves respectively based on the curve segment; Determining curve segments with consistent slopes as having consistent change trends, and determining a plurality of bubble density curves as having consistent change trends based on a comparison result that the first quantity ratio is greater than or equal to a first preset ratio; Determining that the change trends of the bubble densities of the cathode bubbles are consistent based on a comparison result that the second number ratio is greater than or equal to the second preset ratio; Determining that the change trend of the bubble density of the cathode bubbles is inconsistent based on a comparison result that the second number proportion is less than the second preset proportion; The first number ratio is the ratio of the number of curve segments with a consistent change trend to the total number of curve segments of the corresponding bubble density curve, and the second number ratio is the ratio of the number of bubble density curves with a consistent change trend to the total number of bubble density curves. Under the condition that the change trend of the bubble density is consistent, the process of determining the eligibility of the copper plating process based on the rate matching degree includes: The ratio of the copper thickness growth rate in the copper deposition stage to the copper thickness reduction rate in the copper dissolution stage of the copper plating process is determined as the rate matching degree; Comparing the rate matching degree with the preset matching degree respectively; Determining that the copper plating process is qualified based on a comparison result that the rate matching degree is less than or equal to the first preset matching degree and greater than or equal to the second preset matching degree; Under the condition that the trend of bubble density change is inconsistent, the process of determining the eligibility of the copper plating process according to the mean value of the bubble residence time includes: Acquire several frames of images for a single area to determine the average residence time of the bubble; Comparing the average length of stay with a preset length of stay; Determining that the average residence time of the bubbles in a single area is qualified based on a comparison result that the average residence time is less than or equal to the preset time; Determine a third ratio of regions having a qualified average length of stay and compare the ratio with a third preset ratio; Determining that the copper plating process is qualified based on a comparison result that the third quantity ratio is greater than or equal to the third preset ratio; Under the condition that the copper plating process is qualified, the process of determining and adjusting the axis angle according to the pulsation speed of the electrolyte in the blind hole includes: comparing the pulsation speed with a preset pulsation speed respectively; Determining to reduce the axis angle based on a comparison result that the pulsation speed is greater than a first preset pulsation speed; The axis angle is the angle between the nozzle axis and the blind hole axis, the pulsating speed is subtracted from the first preset pulsating speed to obtain a first speed difference, and a plurality of angle adjustment coefficients corresponding to the first speed difference are set to reduce the axis angle according to the angle adjustment coefficients; Under the condition that the copper plating process is qualified, the process of determining and adjusting the nozzle pressure of the electrolyte according to the pulsation speed of the electrolyte in the blind hole includes: comparing the pulsation speed with a preset pulsation speed respectively; Determining to increase the nozzle pressure based on a comparison result that the pulsation speed is less than a second preset pulsation speed; wherein, the second preset pulsating speed is subtracted from the pulsating speed to obtain a second speed difference value, and a plurality of pressure adjustment coefficients corresponding to the second speed difference value are set to increase the nozzle pressure according to the pressure adjustment coefficients; The process of determining the recovery time of the copper ion concentration includes: Monitor the copper ion concentration of the electrolyte in real time and establish an ion concentration curve; On the ion concentration curve, a horizontal line is established parallel to the abscissa axis with the preset ion concentration as the ordinate; Determine an average of time differences between a plurality of intersection points of the horizontal line and the ion concentration curve, and determine the average of the time differences as the recovery duration; The quality inspection cycle of the finished printed circuit board is determined based on the recovery time. For a single inspection cycle, the process of determining the copper distribution deviation in the blind via includes: Determine, for a single blind hole, a first area ratio where the copper thickness is greater than a first preset copper thickness and a second area ratio where the copper thickness is less than a second preset copper thickness; Determining an absolute difference in area between the first area ratio and the second area ratio; The standard deviation of several of the absolute differences in area is determined for a single test, and the standard deviation is determined as the copper distribution deviation.

2. The method for preparing a millimeter wave radar circuit board based on pulse electroplating according to claim 1, characterized in that: The process of determining and optimizing the second preset proportion according to the copper distribution deviation includes: comparing the copper distribution deviation with a preset deviation; Determining to optimize the second preset proportion based on a comparison result that the copper distribution deviation is greater than the preset deviation; Determining a first deviation value between the copper distribution deviation and the preset deviation; A plurality of proportion optimization coefficients corresponding to the first deviation value are set to increase the second preset proportion according to the proportion optimization coefficients.

3. The method for preparing a millimeter wave radar circuit board based on pulse electroplating according to claim 1, characterized in that: The process of determining and optimizing the preset pulsation speed according to the copper distribution deviation includes: comparing the copper distribution deviation with a preset deviation; Determining to optimize the preset pulsation speed based on a comparison result that the copper distribution deviation is less than or equal to the preset deviation; Determining a second deviation value between the preset deviation and the copper distribution deviation; A plurality of speed optimization coefficients corresponding to the second deviation value are set to respectively reduce the first preset pulsation speed and increase the second preset pulsation speed according to the speed optimization coefficients.

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