Multi-layer circuit board preparation method and system based on via hole filling optimization and multi-layer circuit board

Abstract

The invention discloses a multilayer circuit board preparation method and system based on via hole filling optimization and a multilayer circuit board, and relates to the technical field of circuit board preparation, and the method comprises the steps: obtaining the size of a via hole, calculating the depth-to-width ratio, constructing a viscosity gradient function, taking a via hole filling quality evaluation index as a first optimization target, and solving an optimal ratio; designing a vacuum degree control strategy; the current capillary pressure is obtained, differential pressure driving force is calculated according to the current through hole gas pressure intensity, the time needed for filling and the preset ultrasonic vibration duration are calculated in combination with the through hole diameter, the hole depth and the viscosity gradient function, and ultrasonic auxiliary filling is carried out while through hole filling is carried out; filling the via hole, and controlling the vacuum degree according to the vacuum degree adjusting curve; and the real-time filling rate and the cavity volume are obtained, a second target function is constructed with the difference between the minimum target filling rate and the actual filling rate and the filling cost as a second optimization target, and the optimal filling step number and the optimal single injection material volume are solved.

Description

Technical Field

[0001] The present application relates to the technical field of circuit board preparation, and in particular to a method and system for preparing a multilayer circuit board based on via hole filling optimization, and a multilayer circuit board. Background Art

[0002] Multilayer printed circuit boards are widely used in electronic devices. They achieve high-density integration and complex functions through circuit designs of different layers. Vias are important structures that connect different circuit layers, including through holes, blind holes and buried holes. The filling quality of vias has an important impact on the reliability, electrical performance and processing accuracy of multilayer circuit boards. Optimizing the filling process is an important step to improve the performance of multilayer circuit boards. One of the existing via filling technologies is resin filling technology, which is suitable for multilayer printed circuit boards with high-speed signal transmission and high reliability requirements.

[0003] The Chinese patent application publication number discloses a multilayer circuit board and a method for making the same, which includes: providing a sub-board, the sub-board having a via hole and the first surface of the sub-board having a conductive pattern electrically connected to the via hole; making a photosensitive film on the first surface so that the photosensitive film covers at least part of the conductive pattern; exposing and developing the photosensitive film to form a protective pattern at the conductive pattern; making an insulating layer on the first surface so that the insulating layer covers the first surface where the protective pattern is not retained; removing the protective pattern so that the insulating layer forms a conductive channel at the conductive pattern; filling the conductive channel with conductive material to form a conductive column electrically connected to the conductive pattern; and making a build-up circuit on the sub-board. The multilayer circuit board and the method for making the same provided by the present application solve the technical problems of low processing efficiency and poor product quality of multilayer circuit boards in the related art.

[0004] In the prior art, when filling via holes during the preparation of multilayer circuit boards, the distribution of filling materials in the holes is often uneven, which easily generates air gaps or voids between the hole walls and the filling materials, resulting in reduced conductivity and reliability of the via holes. Summary of the invention

[0005] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, one purpose of the present application is to propose a method, system and multilayer circuit board preparation method based on via filling optimization, which improves the conductivity problem of the circuit board caused by bubbles in the existing filling process.

[0006] One aspect of the present application provides a method for preparing a multilayer circuit board based on via filling optimization, comprising: Step S100: obtaining the size of the via hole in the substrate of the multilayer circuit board, calculating its aspect ratio, setting the value range of the initial viscosity and the final viscosity of the filling material, constructing a viscosity gradient function, taking the via hole filling quality evaluation index as the first optimization target and the filling material ratio as the first optimization variable, and solving the optimal ratio; Step S200: establishing a first relationship model and a second relationship model between vacuum degree and filling rate, and between vacuum degree and via gas pressure, respectively, and designing a vacuum degree control strategy according to the first relationship model and the second relationship model to calculate the pressure control threshold of the vacuuming process and the target vacuum degree at each moment; Step S300: obtaining the capillary pressure at the current moment, calculating the differential pressure driving force according to the gas pressure of the via hole at the current moment, calculating the time required for filling in combination with the via hole diameter and hole depth and the viscosity gradient function, presetting the ultrasonic vibration duration, and performing ultrasonic-assisted filling while the via hole is being filled; Step S400: obtaining a filling material according to the optimal ratio and the viscosity gradient function to fill the via hole, and controlling the vacuum degree of the external vacuum cavity according to the vacuum degree adjustment curve to minimize the deviation between the gas pressure of the via hole and the pressure control threshold; Step S500: obtaining the real-time filling rate and cavity volume of the via hole, taking the number of filling steps and the single injection material volume as the second optimization variable, taking minimizing the difference between the target filling rate and the actual filling rate and the filling cost as the second optimization target, constructing a second objective function, and solving the optimal number of filling steps and the optimal single injection material volume; The method of obtaining the size of the via hole in the multilayer circuit board substrate, calculating its aspect ratio, setting the value range of the initial viscosity and the final viscosity of the filling material, constructing the viscosity gradient function, taking the via hole filling quality evaluation index as the first optimization target and the filling material ratio as the first optimization variable, and solving the optimal ratio is as follows: Step S110: Obtain a multilayer circuit board substrate with processed via holes and obtain the aperture of the via holes and hole depth , calculate the aspect ratio of the via hole ; Step S120: Setting the initial viscosity of the filling material according to the via hole diameter and end viscosity scope; The specific method for setting the range of the initial viscosity and the final viscosity of the filling material according to the aperture of the via hole is: Step S121: Based on the relationship between the flow rate of the filling material in the via hole and the viscosity, pore size, capillary pressure and hole depth, the filling material can fill the via hole only when the flow rate is greater than or equal to the critical flow rate. When the viscosity Equal to the critical viscosity, according to the preset critical flow rate , calculate the critical viscosity ; Step S122: For a given aperture , respectively calculate the upper limit of the initial viscosity under capillary flow conditions and the upper limit of the final viscosity ; Step S123: As the value range of initial viscosity, As the range of values ​​of the end viscosity; Step S130: Obtain the number of filling steps of the via hole as N steps, and define the viscosity gradient function of each step , calculate the viscosity of the filling material at each step; Step S140: Taking maximizing the via filling quality evaluation index Q as the first optimization goal, taking the filling material ratio X as the first optimization variable, taking the viscosity constraint and the filling material ratio constraint as the first constraint condition, constructing a first objective function, and solving the first objective function to obtain the optimal ratio; The first and second relationship models of vacuum degree and filling rate, vacuum degree and via gas pressure are respectively established, and a vacuum degree control strategy is designed according to the first and second relationship models. The specific method for calculating the pressure control threshold of the vacuuming process and the target vacuum degree at each moment is: Step S210: Obtain different apertures , aspect ratio and vacuum The data of the filling rate F of the lower via hole is used to fit the first relationship model between the aperture, aspect ratio, vacuum degree and filling rate; Step S220: According to the ideal gas state equation, the vacuum degree of the external vacuum cavity and the gas pressure of the via hole are obtained. The second relationship model between Step S230: Divide the vacuuming process into three stages and preset the target filling rate for each stage. , substituting the target filling rate into the first relationship model to calculate the target vacuum degree of the corresponding stage, and based on the second relationship model, calculating the pressure control threshold of the corresponding stage according to the target vacuum degree; Step S240: Selecting a hyperbolic tangent function as a transition function, constructing a vacuum adjustment curve based on the target vacuum degree of each stage and the turning point of each stage, for calculating the target vacuum degree at each moment in each stage, and using the vacuum adjustment curve and the pressure control threshold as a vacuum control strategy; The specific method of obtaining the capillary pressure at the current moment, calculating the pressure difference driving force according to the gas pressure of the via hole at the current moment, calculating the time required for filling in combination with the via hole diameter and hole depth and viscosity gradient function, and presetting the ultrasonic vibration duration, and performing ultrasonic-assisted filling while filling the via hole is as follows: Step S310: Based on the diameter of the via hole, the contact angle between the filling material and the hole wall is calculated. , calculate the capillary pressure ; Step S320: Based on the gas pressure of the via hole at that moment , the atmospheric pressure at that moment The gas pressure of the via at that moment The difference between ; Step S330: Calculate the flow velocity of the filling material in the via hole at the current moment according to the capillary pressure, the pressure difference driving force, the hole diameter and hole depth of the via hole, and the viscosity gradient function. ; Step S340: Calculate the time required for filling according to the hole depth of the via hole and the flow rate of the filling material ; Step S350: Preset ultrasonic vibration duration The ultrasonic vibration duration is greater than or equal to the time required for filling. , ultrasonic assisted filling is performed simultaneously with via filling; The specific method of obtaining the filling material according to the optimal ratio and the viscosity gradient function to fill the via hole, and controlling the vacuum degree of the external vacuum cavity according to the vacuum degree adjustment curve so as to minimize the deviation between the gas pressure of the via hole and the pressure control threshold is: Step S410: preparing a filling material according to the viscosity of each step obtained by the viscosity gradient function and combining the best ratio of each step to fill the via hole; Step S420: adjusting the vacuum degree of the external vacuum chamber to the target vacuum degree according to the vacuum degree adjustment curve, and calculating the gas pressure of the via hole in real time to minimize the gas pressure of the via hole. Pressure control threshold The deviation between as a regulatory target; The specific method of obtaining the real-time filling rate and cavity volume of the via hole, taking the filling steps and the single injection material volume as the second optimization variable, minimizing the difference between the target filling rate and the actual filling rate and the filling cost as the second optimization target, constructing the second objective function, and solving the optimal filling steps and the optimal single injection material volume is as follows: Step S510: During the via hole filling process, a three-dimensional image of the via hole is obtained after each step, and the volume of the filling material is obtained by an image processing algorithm. and via volume , calculate the real-time fill rate ; Step S520: Calculate the remaining unfilled cavity volume in the via hole according to the hole diameter and hole depth of the via hole and the real-time filling rate. ; Step S530: Filling step number N and single injection material volume For the second optimization variable, calculate the target fill rate The actual filling rate The absolute value of the difference between the target filling rate and the actual filling rate is taken as the difference between the target filling rate and the actual filling rate, and the filling material cost per unit volume is calculated. and filling cost per unit time , calculate the material cost and time cost to get the total filling cost; Step S540: Taking minimizing the difference between the target filling rate and the actual filling rate and minimizing the filling cost as the second optimization goal, defining a second constraint goal, and constructing a second objective function; The second constraint target is defined including a filling volume constraint, a filling rate constraint and a filling time constraint. The calculation formula of the filling volume constraint is: ,in represents the initial cavity volume; the initial cavity volume is the remaining unfilled cavity volume in the via when n is equal to 0 The value of The calculation formula of the fill rate constraint is: ,in, Indicates the actual filling rate after N times of filling, It represents the minimum filling rate, which is set by those skilled in the art based on experience.

[0007] The calculation formula of the filling time constraint is: , ,in, represents the differential pressure driving force for filling in the nth step; Step S550: using a genetic algorithm to solve the second objective function to obtain an optimal number of filling steps and an optimal single injection material volume, which are used to guide the optimization of the current via filling process.

[0008] One aspect of the present application provides a multilayer circuit board preparation system based on via filling optimization, comprising: A filling material ratio module is used to obtain the size of the via hole in the substrate of the multilayer circuit board, calculate its aspect ratio, set the value range of the initial viscosity and the final viscosity of the filling material, construct a viscosity gradient function, and use the via hole filling quality evaluation index as the first optimization target and the filling material ratio as the first optimization variable to solve the optimal ratio; A vacuum process control module, used to respectively establish a first relationship model and a second relationship model between vacuum degree and filling rate, and between vacuum degree and gas pressure of the via, and to design a vacuum control strategy based on the first relationship model and the second relationship model, so as to calculate a pressure control threshold of the vacuum process and a target vacuum degree at each moment; Ultrasonic assisted filling module, used to obtain the capillary pressure at the current moment, calculate the pressure difference driving force according to the gas pressure of the via hole at the current moment, calculate the time required for filling in combination with the via hole diameter and hole depth and viscosity gradient function, preset the ultrasonic vibration duration, and perform ultrasonic assisted filling while the via hole is being filled; A real-time filling control module is used to obtain a filling material according to an optimal ratio and a viscosity gradient function to fill the via hole, and to control the vacuum degree of the external vacuum cavity according to a vacuum degree adjustment curve, so as to minimize the deviation between the gas pressure of the via hole and the pressure control threshold; The filling process optimization module is used to obtain the real-time filling rate and cavity volume of the via hole, take the filling steps and the single injection material volume as the second optimization variable, take minimizing the difference between the target filling rate and the actual filling rate and the filling cost as the second optimization goal, construct the second objective function, and solve the optimal filling steps and the optimal single injection material volume.

[0009] One aspect of the present application provides a multi-layer circuit board, which is manufactured by executing a multi-layer circuit board manufacturing method based on via hole filling optimization by using the multi-layer circuit board manufacturing system based on via hole filling optimization.

[0010] The multi-layer circuit board preparation method, system and multi-layer circuit board based on via filling optimization proposed in this application have the following advantages over the prior art: The present application designs a viscosity gradient function of the filling material so that the viscosity of the filling material gradually increases from the initial viscosity to the final viscosity during the filling process, so that the flow rate of the filling material in the via hole is optimized and controlled. In the early stage of filling, a lower viscosity is conducive to the rapid entry of the filling material into the via hole, while in the later stage of filling, a higher viscosity can slow down the flow of the filling material and prevent the filling material from flowing back or generating bubbles in the via hole, thereby improving the uniformity of the distribution of the filling material in the hole and reducing the generation of air gaps or voids.

[0011] This application establishes a relationship model between vacuum degree, filling rate and gas pressure of vias, and designs a phased vacuum degree control strategy. During the filling process, the vacuum degree of the external vacuum cavity is adjusted in real time, which can effectively remove the gas inside the vias, reduce the gas pressure inside the vias, and improve the filling rate of the filling material. At the same time, the vacuum environment can also reduce the generation of bubbles during the filling process, further improve the distribution uniformity of the filling material in the hole, and reduce the generation of air gaps and voids.

[0012] The present application introduces ultrasonic vibration during the via filling process, and the duration of the ultrasonic vibration is greater than or equal to the time required for filling, thereby achieving the simultaneous filling process and ultrasonic assistance, improving the interface bonding between the filling material and the hole wall, and reducing air gaps and voids at the interface.

[0013] The present application obtains the filling rate and cavity volume of the via in real time during the filling process, uses the number of filling steps and the volume of material injected at a single time as optimization variables, dynamically optimizes the filling process, controls the amount of material filled in each step, achieves precise filling, avoids overfilling or underfilling, and improves the conductive performance and reliability of the via. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A method flow chart of a multilayer circuit board preparation method based on via filling optimization provided in this application; Figure 2 Flowchart of the construction method of the vacuum control strategy provided in this application Figure 3 A flow chart of the method for optimizing the optimal number of filling steps and the optimal single injection material volume provided in this application; Figure 4 Functional module diagram of a multilayer circuit board preparation system based on via filling optimization provided in this application. DETAILED DESCRIPTION

[0015] In order to better understand the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of exemplary embodiments of the present application and do not limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0016] In the accompanying drawings, the size, dimensions and shapes of the elements have been slightly adjusted for ease of illustration. The drawings are for illustration only and are not strictly drawn to scale. As used herein, the terms "substantially", "approximately" and similar terms are used as terms of approximation, not as terms of degree, and are intended to illustrate the inherent deviations in measurements or calculations that will be recognized by those of ordinary skill in the art. In addition, in this application, the order in which the steps are described does not necessarily represent the order in which these processes occur in actual operation, unless otherwise specified or can be derived from the context.

[0017] It should also be understood that expressions such as "including", "comprising", "having", "containing" and / or "comprising" are open rather than closed expressions in this specification, which indicate the presence of the stated features, elements and / or components, but do not exclude the presence of one or more other features, elements, components and / or combinations thereof. In addition, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire list of features rather than just the individual elements in the list. In addition, when describing embodiments of the present application, "may" is used to mean "one or more embodiments of the present application". And, the term "exemplary" is intended to refer to an example or illustration.

[0018] Unless otherwise defined, all words (including engineering terms and scientific and technological terms) used in this article have the same meaning as those commonly understood by ordinary technicians in the field to which this application belongs. It should also be understood that unless there is a clear explanation in this application, words defined in commonly used dictionaries should be interpreted as having the same meaning as their meaning in the context of the relevant technology, and should not be interpreted in an idealized or overly formal sense.

[0019] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0020] Example 1 like Figure 1 As shown, the method for preparing a multilayer circuit board based on via hole filling optimization provided by the present application includes: Step S100: obtaining the size of the via hole in the substrate of the multilayer circuit board, calculating its aspect ratio, setting the value range of the initial viscosity and the final viscosity of the filling material, constructing a viscosity gradient function, taking the via hole filling quality evaluation index as the first optimization target and the filling material ratio as the first optimization variable, and solving the optimal ratio; The method of obtaining the size of the via hole in the multilayer circuit board substrate, calculating its aspect ratio, setting the value range of the initial viscosity and the final viscosity of the filling material, constructing the viscosity gradient function, taking the via hole filling quality evaluation index as the first optimization target and the filling material ratio as the first optimization variable, and solving the optimal ratio is as follows: Step S110: Obtain a multilayer circuit board substrate with processed via holes, obtain the hole diameter and hole depth of the via holes, and calculate the aspect ratio of the via holes. ; The calculation formula of the aspect ratio is: ,in, is the hole depth of the via hole, is the aperture of the via hole; Step S120: Setting the initial viscosity of the filling material according to the via hole diameter and end viscosity scope; The specific method for setting the range of the initial viscosity and the final viscosity of the filling material according to the aperture of the via hole is: Step S121: Based on the relationship between the flow rate of the filling material in the via hole and the viscosity, pore size, capillary pressure and hole depth, the filling material can fill the via hole only when the flow rate is greater than or equal to the critical flow rate. When the viscosity Equal to the critical viscosity, according to the preset critical flow rate , calculate the critical viscosity ; The critical flow rate is set by those skilled in the art according to the via size and production cycle requirements, and is generally in the range of [0.1 mm / s, 1 mm / s].

[0021] The relationship between the flow velocity and viscosity, pore size, capillary pressure and pore depth is: ,in, is the capillary pressure, is the flow velocity, is viscosity; The calculation formula of the critical viscosity is: ; Step S122: For a given aperture , respectively calculate the upper limit of the initial viscosity under capillary flow conditions and the upper limit of the final viscosity ; The calculation formula for the upper limit of the initial viscosity is: ,in, is the capillary pressure in the initial stage; The calculation formula for the upper limit of the end viscosity is: ,in, is the capillary pressure at the termination stage; The capillary pressure in the initial stage and the capillary pressure in the termination stage are estimated by those skilled in the art based on the contact angle between the filling material and the pore wall.

[0022] Step S123: As the value range of initial viscosity, As the range of values ​​of the end viscosity; in, , The value of is set by those skilled in the art based on experience.

[0023] Step S130: Obtain the number of filling steps of the via hole as N steps, and define the viscosity gradient function of each step , calculate the viscosity of the filling material at each step; The functional expression of the viscosity gradient function is: ,in, represents the viscosity of the filling material in step n, is the initial viscosity, Indicates the viscosity variation range, is the viscosity change rate control factor, is the midpoint of viscosity change; The calculation formula for the viscosity variation range is: ; The viscosity change rate control factor is set by those skilled in the art based on experience, and the value range is 1 to 10; The midpoint value range of the viscosity change is ; Step S140: Taking maximizing the via filling quality evaluation index Q as the first optimization goal, taking the filling material ratio X as the first optimization variable, taking the viscosity constraint and the filling material ratio constraint as the first constraint condition, constructing a first objective function, and solving the first objective function to obtain the optimal ratio; The calculation formula of the first optimization objective is: ,in, is the filling rate of the n-1th step, is the filling uniformity of the n-1th step, is the defect density at step n-1, , , , are the weight coefficients of filling rate, filling uniformity and defect density respectively, represents the via filling quality evaluation index of step n-1, It represents the via filling quality evaluation index when the filling material ratio X in the nth step is maximized; The expression of the viscosity constraint is: ; The expression of the filling material ratio constraint is: , ,in, is the ratio of the nith filling material, NI is the number of filling material types, and the filling material ratio ; The calculation formula of the filling rate of the nth step is: ,in, is the filling material volume of the nth step, is the volume of the via hole; The calculation formula for the filling uniformity in the nth step is: ,in, is the standard deviation of the hardness of the filling material; The calculation formula of the defect density in the nth step is: ,in, is the number of defects at step n, including bubbles and cavities; The above steps are aimed at determining the best filling material combination suitable for via filling, laying the foundation for the subsequent filling process. By comprehensively considering factors such as via size and aspect ratio, a filling material combination with a suitable viscosity range and optimal ratio is selected, which can significantly improve the filling quality and efficiency.

[0024] Step S200: establishing a first relationship model and a second relationship model between vacuum degree and filling rate, and between vacuum degree and via gas pressure, respectively, and designing a vacuum degree control strategy according to the first relationship model and the second relationship model to calculate the pressure control threshold of the vacuuming process and the target vacuum degree at each moment; The first and second relationship models of vacuum degree and filling rate, vacuum degree and via gas pressure are respectively established, and a vacuum degree control strategy is designed according to the first and second relationship models. The specific method for calculating the pressure control threshold of the vacuuming process and the target vacuum degree at each moment is: Step S210: Obtain different apertures , aspect ratio and vacuum The data of the filling rate F of the lower via hole is used to fit the first relationship model between the aperture, aspect ratio, vacuum degree and filling rate; The calculation formula of the first relationship model is: ,in, , , , , , , , , , is the fitting coefficient; The fitting coefficient is obtained according to the different pore sizes , aspect ratio and vacuum The data of the lower via hole filling rate F is obtained by fitting.

[0025] Step S220: obtaining a second relationship model between the vacuum degree of the external vacuum cavity and the gas pressure of the via hole according to the ideal gas state equation; The calculation formula of the via gas pressure is: ,in, is the volume of the via hole, is the volume of the vacuum chamber; Step S230: Divide the vacuuming process into three stages and preset the target filling rate for each stage. , substituting the target filling rate into the first relationship model to calculate the target vacuum degree of the corresponding stage, and based on the second relationship model, calculating the pressure control threshold of the corresponding stage according to the target vacuum degree; The target fill rate It represents the target filling rate at the corresponding stage of the filling process step n.

[0026] The three stages are the initial vacuuming stage, the intermediate pressure holding stage and the final vacuuming stage; in the initial vacuuming stage, the vacuum degree is adjusted from normal pressure to the target vacuum degree of the first stage. , the corresponding time range is ; During the intermediate pressure holding stage, the vacuum degree is maintained at the target vacuum degree of the second stage , the corresponding time range is ; End the vacuuming stage and increase the vacuum degree from the target vacuum degree of the second stage Adjust to the target vacuum degree of the third stage , the corresponding time range is ; The target filling rate is set by those skilled in the art according to production equipment and material properties.

[0027] The pressure control threshold value of the corresponding stage is calculated based on the target vacuum degree based on the second relationship model, which means that the target vacuum degree is substituted into the second relationship model, and the obtained gas pressure of the via hole is the pressure control threshold value corresponding to the target filling rate.

[0028] Step S240: Selecting a hyperbolic tangent function as a transition function, constructing a vacuum adjustment curve based on the target vacuum degree of each stage and the turning point of each stage, for calculating the target vacuum degree at each moment in each stage, and using the vacuum adjustment curve and the pressure control threshold as a vacuum control strategy; The expression of the vacuum degree adjustment curve is: ,in, is the target vacuum degree at each stage, is the vacuum degree change rate control factor, It is the turning point between the second and third stages; The vacuum degree change rate control factor is set by those skilled in the art based on experience.

[0029] Figure 2 A flow chart of the construction method of the vacuum control strategy provided in this application; The construction process of the vacuum degree adjustment curve is as follows: The vacuum adjustment curve for the initial vacuuming stage is constructed as follows: ,in, Indicates the target vacuum degree at time t in the initial vacuuming stage; The vacuum adjustment curve for the intermediate pressure holding stage is constructed as follows: ; The vacuum adjustment curve for terminating the vacuum pumping stage is constructed as follows: ,in, Indicates the target vacuum degree at the time t when the vacuuming phase is terminated; The three stages of vacuum adjustment curves are combined to form a complete vacuum adjustment curve: ,in, is a step function. When t is greater than or equal to 0, =1, otherwise, =0; Simplify and obtain the final vacuum adjustment curve.

[0030] The above steps reveal their internal connection by establishing a quantitative relationship model between vacuum degree and filling rate, vacuum degree and gas pressure of via hole, and provide a theoretical basis for the optimization control of vacuum-assisted filling. By applying negative pressure to the via hole in a vacuum environment and reducing the gas pressure in the hole, it helps the filling material to fully fill the via hole under capillary action and pressure difference drive, and reduce the generation of bubble defects.

[0031] Step S300: obtaining the capillary pressure at the current moment, calculating the differential pressure driving force according to the gas pressure of the via hole at the current moment, calculating the time required for filling in combination with the via hole diameter and hole depth and the viscosity gradient function, presetting the ultrasonic vibration duration, and performing ultrasonic-assisted filling while the via hole is being filled; The specific method of obtaining the capillary pressure at the current moment, calculating the pressure difference driving force according to the gas pressure of the via hole at the current moment, calculating the time required for filling in combination with the via hole diameter and hole depth and viscosity gradient function, and presetting the ultrasonic vibration duration, and performing ultrasonic-assisted filling while filling the via hole is as follows: Step S310: Based on the diameter of the via hole, the contact angle between the filling material and the hole wall is calculated. , calculate the capillary pressure ; The calculation formula of the capillary pressure is: ,in, is the surface tension of the filling material; Step S320: Based on the gas pressure of the via hole at that moment , the atmospheric pressure at that moment The gas pressure of the via at that moment The difference between ; The calculation formula of the pressure difference driving force is: ; Step S330: Calculate the flow velocity of the filling material in the via hole at the current moment according to the capillary pressure, the pressure difference driving force, the hole diameter and hole depth of the via hole, and the viscosity gradient function. ; The calculation formula of the flow velocity is: ; Step S340: Calculate the time required for filling according to the hole depth of the via hole and the flow rate of the filling material ; The calculation formula for the filling time is: ,in, is the hole depth, i.e. the length that the filling material needs to flow; Step S350: Preset ultrasonic vibration duration The ultrasonic vibration duration is greater than or equal to the time required for filling. , ultrasonic assisted filling is performed simultaneously with via filling; When presetting the value of the ultrasonic vibration duration, the ultrasonic vibration duration needs to be greater than or equal to the time required for filling, in order to ensure that the ultrasonic vibration can be continuously applied before the filling material is completely injected into the conductive hole to play its role in promoting filling. The specific value of the ultrasonic vibration duration is set by technical personnel in this field based on experience.

[0032] Step S400: obtaining a filling material according to the optimal ratio and the viscosity gradient function to fill the via hole, and controlling the vacuum degree of the external vacuum cavity according to the vacuum degree adjustment curve to minimize the deviation between the gas pressure of the via hole and the pressure control threshold; The specific method of obtaining the filling material according to the optimal ratio and the viscosity gradient function to fill the via hole, and controlling the vacuum degree of the external vacuum cavity according to the vacuum degree adjustment curve so as to minimize the deviation between the gas pressure of the via hole and the pressure control threshold is: Step S410: preparing a filling material according to the viscosity of each step obtained by the viscosity gradient function and combining the best ratio of each step to fill the via hole; Step S420: adjusting the vacuum degree of the external vacuum chamber to the target vacuum degree according to the vacuum degree adjustment curve, and calculating the gas pressure of the via hole in real time to minimize the gas pressure of the via hole. Pressure control threshold The deviation between as a regulatory target; The calculation formula for the deviation between the gas pressure of the via and the pressure control threshold is: ; As the filling material is continuously injected, the volume of the gas in the via is further reduced, and its pressure increases accordingly. At the same time, the vacuum degree of the external vacuum cavity is dynamically controlled by the vacuum degree adjustment curve; when the gas pressure in the via increases to the preset pressure control threshold, it means that the pressure difference driving force at this time is large enough to effectively promote the flow and filling of the filling material.

[0033] In order to maintain the gas pressure of the via hole near the pressure control threshold, it is necessary to dynamically adjust the vacuum degree of the external vacuum chamber through the vacuum degree adjustment curve. Specifically, when the gas pressure of the via hole is lower than the pressure control threshold, the external vacuum degree is appropriately reduced to promote the increase of the pressure difference; when the gas pressure of the via hole is higher than the pressure control threshold, the external vacuum degree is appropriately increased to promote the decrease of the pressure difference.

[0034] Step S500: obtaining the real-time filling rate and cavity volume of the via hole, taking the number of filling steps and the single injection material volume as the second optimization variable, taking minimizing the difference between the target filling rate and the actual filling rate and the filling cost as the second optimization target, constructing a second objective function, and solving the optimal number of filling steps and the optimal single injection material volume; The specific method of obtaining the real-time filling rate and cavity volume of the via hole, taking the filling steps and the single injection material volume as the second optimization variable, minimizing the difference between the target filling rate and the actual filling rate and the filling cost as the second optimization target, constructing the second objective function, and solving the optimal filling steps and the optimal single injection material volume is as follows: Step S510: During the via hole filling process, a three-dimensional image of the via hole is obtained after each step, and the volume of the filling material is obtained by an image processing algorithm. and via volume , calculate the real-time fill rate ; The calculation formula of the real-time filling rate is: ; Step S520: Calculate the remaining unfilled cavity volume in the via hole according to the hole diameter and hole depth of the via hole and the real-time filling rate. ; The calculation formula of the cavity volume is: ; Step S530: Filling step number N and single injection material volume For the second optimization variable, calculate the target fill rate The actual filling rate The absolute value of the difference between the target filling rate and the actual filling rate is taken as the difference between the target filling rate and the actual filling rate, and the filling material cost per unit volume is calculated. and filling cost per unit time , calculate the material cost and time cost to get the total filling cost; Step S540: Taking minimizing the difference between the target filling rate and the actual filling rate and minimizing the filling cost as the second optimization goal, defining a second constraint goal, and constructing a second objective function; The calculation formula of the second optimization objective is: , ,in, is the filling time of step n, represents the minimization of filling cost, It means minimizing the difference between the target filling rate and the actual filling rate; The second constraint target is defined including a filling volume constraint, a filling rate constraint and a filling time constraint. The calculation formula of the filling volume constraint is: ,in represents the initial cavity volume; the initial cavity volume is the remaining unfilled cavity volume in the via when n is equal to 0 The value of The calculation formula of the fill rate constraint is: ,in, Indicates the actual filling rate after N times of filling, It represents the minimum filling rate, which is set by those skilled in the art based on experience.

[0035] The calculation formula of the filling time constraint is: , ,in, represents the differential pressure driving force for filling in the nth step; Step S550: using a genetic algorithm to solve the second objective function to obtain an optimal number of filling steps and an optimal single injection material volume, which are used to guide the optimization of the current via filling process.

[0036] Figure 3 A flow chart of the method for optimizing the optimal number of filling steps and the optimal single injection material volume provided in this application; The multilayer circuit board preparation method based on via hole filling optimization provided in the present application can be used to optimize the current via hole filling process, and the specific implementation steps are: obtain a multilayer circuit board substrate with processed via holes, measure the aperture of the via hole to be 0.1mm, the hole depth to be 1mm, and calculate the aspect ratio of the via hole to be 10; according to the aperture of the via hole of 0.1mm, set the initial viscosity range of the filling material to 50-100Pa×s, and the final viscosity range to 800-1000Pa×s; set the number of filling steps of the via hole to 10 steps, construct a viscosity gradient function, calculate the viscosity of the filling material at each step, and the viscosity increases linearly from the initial viscosity to the final viscosity; design a vacuum control strategy, divide the vacuuming process into three stages, and calculate the pressure control threshold and target vacuum adjustment curve of each stage; in the via hole filling process, obtain the capillary pressure and the via hole gas pressure at the current moment in real time, calculate the pressure difference driving force, the flow rate of the filling material and the time required for filling, and perform ultrasonic assisted filling; prepare the filling material according to the optimal ratio and the viscosity gradient function , fill the via hole, and control the vacuum degree of the external vacuum cavity according to the vacuum degree adjustment curve to minimize the deviation between the gas pressure of the via hole and the pressure control threshold; after completing the 5th step of filling, the real-time filling rate of the via hole is obtained to be 60%, and the cavity volume is 0.05ml. Substitute these parameters into the second objective function and solve it, and the optimal number of filling steps is 8 steps, and the optimal single injection material volume is 0.015ml; according to the optimization results, adjust the subsequent filling steps, change the originally planned 6-10 steps to 6-8 steps, and increase the injection material volume of each step from 0.01ml to 0.015ml, so as to optimize the current filling process of the via hole; after completing the filling of the via hole, deposit a metal plating layer on the inner wall of the filled via hole to realize the interconnection between the inner wall of the via hole and the filling material and the circuit board substrate, and use pattern transfer, etching, electroplating and other processes to form the required pattern circuit and interconnection circuit on the surface of the multilayer circuit board, perform metallization, solder mask and other surface treatments on the surface of the circuit board, and perform electrical performance test and reliability inspection on the finished circuit board.

[0037] In addition, the above-mentioned multi-layer circuit board preparation method based on via hole filling optimization can also be used for via hole filling and multi-layer circuit board preparation processes with similar via hole sizes and structures to the current ones.

[0038] Example 2 like Figure 4 As shown, a multi-layer circuit board preparation system based on via filling optimization provided by the present application includes: A filling material ratio module is used to obtain the size of the via hole in the substrate of the multilayer circuit board, calculate its aspect ratio, set the value range of the initial viscosity and the final viscosity of the filling material, construct a viscosity gradient function, and use the via hole filling quality evaluation index as the first optimization target and the filling material ratio as the first optimization variable to solve the optimal ratio; A vacuum process control module, used to respectively establish a first relationship model and a second relationship model between vacuum degree and filling rate, and between vacuum degree and gas pressure of the via, and to design a vacuum control strategy based on the first relationship model and the second relationship model, so as to calculate a pressure control threshold of the vacuum process and a target vacuum degree at each moment; Ultrasonic assisted filling module, used to obtain the capillary pressure at the current moment, calculate the pressure difference driving force according to the gas pressure of the via hole at the current moment, calculate the time required for filling in combination with the via hole diameter and hole depth and viscosity gradient function, preset the ultrasonic vibration duration, and perform ultrasonic assisted filling while the via hole is being filled; A real-time filling control module is used to obtain a filling material according to an optimal ratio and a viscosity gradient function to fill the via hole, and to control the vacuum degree of the external vacuum cavity according to a vacuum degree adjustment curve, so as to minimize the deviation between the gas pressure of the via hole and the pressure control threshold; The filling process optimization module is used to obtain the real-time filling rate and cavity volume of the via hole, take the filling steps and the single injection material volume as the second optimization variable, take minimizing the difference between the target filling rate and the actual filling rate and the filling cost as the second optimization goal, construct the second objective function, and solve the optimal filling steps and the optimal single injection material volume.

[0039] Example 3 According to another aspect of an embodiment of the present invention, a printed circuit board is provided, wherein the multilayer circuit board is manufactured by executing a multilayer circuit board preparation method based on via hole filling optimization by a multilayer circuit board preparation system based on via hole filling optimization. The embodiment of the present invention provides a multilayer circuit board preparation method, system and multilayer circuit board based on via hole filling optimization, by obtaining the filling rate and cavity volume of the via hole in real time during the filling process, taking the filling steps and the single injection material volume as optimization variables, dynamically optimizing the filling process, controlling the amount of material filled in each step, achieving precise filling, avoiding overfilling or underfilling, and improving the conductive performance and reliability of the via hole.

[0040] The parts of the above-mentioned technical solutions provided in the embodiments of the present application that are consistent with the implementation principles of the corresponding technical solutions in the prior art are not described in detail to avoid excessive redundancy.

[0041] The specific implementation modes as described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation mode of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a multilayer circuit board based on via filling optimization, characterized in that: include: Obtain the size of the via hole in the substrate of the multilayer circuit board, calculate its aspect ratio, set the value range of the initial viscosity and the final viscosity of the filling material, construct a viscosity gradient function, take the via hole filling quality evaluation index as the first optimization target and the filling material ratio as the first optimization variable, and solve the optimal ratio; A first relationship model and a second relationship model between vacuum degree and filling rate, and between vacuum degree and gas pressure of the via are established respectively, and a vacuum degree control strategy is designed according to the first relationship model and the second relationship model to calculate the pressure control threshold of the vacuum pumping process and the target vacuum degree at each moment; The capillary pressure at the current moment is obtained, and the differential pressure driving force is calculated according to the gas pressure of the via hole at the current moment. The time required for filling is calculated by combining the via hole diameter, hole depth and viscosity gradient function, and the ultrasonic vibration duration is preset, and ultrasonic-assisted filling is performed while the via hole is being filled; The via hole is filled with a filling material obtained according to an optimal ratio and a viscosity gradient function, and the vacuum degree of the external vacuum cavity is controlled according to a vacuum degree adjustment curve, so that the deviation between the gas pressure of the via hole and the pressure control threshold is minimized; The real-time filling rate and cavity volume of the via are obtained, and the number of filling steps and the single injection material volume are used as the second optimization variables. The second optimization goal is to minimize the difference between the target filling rate and the actual filling rate and the filling cost. The second objective function is constructed to solve the optimal number of filling steps and the optimal single injection material volume.

2. The method for preparing a multilayer circuit board based on via filling optimization according to claim 1, characterized in that: The method of obtaining the size of the via hole in the multilayer circuit board substrate, calculating its aspect ratio, setting the value range of the initial viscosity and the final viscosity of the filling material, constructing the viscosity gradient function, taking the via hole filling quality evaluation index as the first optimization target and the filling material ratio as the first optimization variable, and solving the optimal ratio is as follows: Get the multi-layer circuit board substrate with processed via holes and get the aperture of the via holes and hole depth , calculate the aspect ratio of the via hole ; Set the initial viscosity of the filling material according to the via hole diameter and end viscosity scope; Get the number of filling steps of the via hole as N steps, and define the viscosity gradient function of each step , calculate the viscosity of the filling material at each step; Taking maximizing the via filling quality evaluation index Q as the first optimization goal, taking the filling material ratio X as the first optimization variable, taking the viscosity constraint and the filling material ratio constraint as the first constraint condition, constructing the first objective function, and solving the first objective function to obtain the optimal ratio.

3. The method for preparing a multilayer circuit board based on via filling optimization according to claim 2, characterized in that: The specific method for setting the range of the initial viscosity and the final viscosity of the filling material according to the aperture of the via hole is: According to the relationship between the flow velocity of the filling material in the via hole and the viscosity, pore size, capillary pressure and hole depth, the filling material can fill the via hole only when the flow velocity is greater than or equal to the critical flow velocity. When the viscosity Equal to the critical viscosity, according to the preset critical flow rate , calculate the critical viscosity ; For a given aperture , respectively calculate the upper limit of the initial viscosity under capillary flow conditions and the upper limit of the final viscosity ; Will As the value range of initial viscosity, As the range of values ​​for the final viscosity.

4. The method for preparing a multilayer circuit board based on via filling optimization according to claim 3, characterized in that: The first and second relationship models of vacuum degree and filling rate, vacuum degree and via gas pressure are respectively established, and a vacuum degree control strategy is designed according to the first and second relationship models. The specific method for calculating the pressure control threshold of the vacuuming process and the target vacuum degree at each moment is: Get different apertures , aspect ratio and vacuum The data of the filling rate F of the lower via hole is used to fit the first relationship model between the aperture, aspect ratio, vacuum degree and filling rate; According to the ideal gas state equation, the vacuum degree of the external vacuum cavity and the gas pressure of the via hole are obtained. The second relationship model between Divide the vacuuming process into three stages and preset the target filling rate for each stage , substituting the target filling rate into the first relationship model to calculate the target vacuum degree of the corresponding stage, and based on the second relationship model, calculating the pressure control threshold of the corresponding stage according to the target vacuum degree; The hyperbolic tangent function is selected as the transition function. Based on the target vacuum degree of each stage and the turning moment of each stage, a vacuum adjustment curve is constructed to calculate the target vacuum degree at each moment in each stage. The vacuum adjustment curve and the pressure control threshold are used as the vacuum control strategy.

5. The method for preparing a multilayer circuit board based on via filling optimization according to claim 4, characterized in that: The specific method of obtaining the capillary pressure at the current moment, calculating the pressure difference driving force according to the gas pressure of the via hole at the current moment, calculating the time required for filling in combination with the via hole diameter and hole depth and viscosity gradient function, and presetting the ultrasonic vibration duration, and performing ultrasonic-assisted filling while filling the via hole is as follows: Based on the hole diameter of the via, combined with the contact angle between the filling material and the hole wall , calculate the capillary pressure ; According to the gas pressure of the via hole at this moment , the atmospheric pressure at that moment The gas pressure of the via at that moment The difference between ; Calculate the flow rate of the filling material in the via hole at the current moment based on the capillary pressure, differential pressure driving force, the diameter and depth of the via hole, and the viscosity gradient function. ; Calculate the time required for filling based on the hole depth of the via and the flow rate of the filling material ; Preset ultrasonic vibration duration The ultrasonic vibration duration is greater than or equal to the time required for filling. , ultrasonic assisted filling is performed simultaneously with via filling.

6. The method for preparing a multilayer circuit board based on via filling optimization according to claim 5, characterized in that: The specific method of obtaining the real-time filling rate and cavity volume of the via hole, taking the filling steps and the single injection material volume as the second optimization variable, minimizing the difference between the target filling rate and the actual filling rate and the filling cost as the second optimization target, constructing the second objective function, and solving the optimal filling steps and the optimal single injection material volume is as follows: During the via filling process, a 3D image of the via is obtained after each step, and the volume of the filling material is obtained through image processing algorithms. and via volume , calculate the real-time fill rate ; Calculate the remaining unfilled cavity volume in the via hole based on the hole diameter and hole depth, combined with the real-time filling rate ; The number of filling steps N and the volume of material injected in a single injection For the second optimization variable, calculate the target fill rate The actual filling rate The absolute value of the difference between the target filling rate and the actual filling rate is taken as the difference between the target filling rate and the actual filling rate, and the filling material cost per unit volume is calculated. and filling cost per unit time , calculate the material cost and time cost to get the total filling cost; Taking minimizing the difference between the target filling rate and the actual filling rate and minimizing the filling cost as the second optimization goal, defining the second constraint goal, and constructing the second objective function; The genetic algorithm is used to solve the second objective function to obtain the optimal number of filling steps and the optimal single injection material volume, which are used to guide the optimization of the current via filling process.

7. The method for preparing a multilayer circuit board based on via filling optimization according to claim 6, characterized in that: The second constraint target is defined including a filling volume constraint, a filling rate constraint and a filling time constraint. The calculation formula of the filling volume constraint is: ,in represents the initial cavity volume; the initial cavity volume is the remaining unfilled cavity volume in the via when n is equal to 0 The value of The calculation formula of the fill rate constraint is: ,in, Indicates the actual filling rate after N times of filling, Indicates the minimum value of the filling rate, which is set by those skilled in the art based on experience; The calculation formula of the filling time constraint is: , ,in, Represents the differential pressure driving force for the nth filling step.

8. A multilayer circuit board preparation system based on via hole filling optimization, which is implemented based on the multilayer circuit board preparation method based on via hole filling optimization according to any one of claims 1 to 7, characterized in that: include: A filling material ratio module is used to obtain the size of the via hole in the substrate of the multilayer circuit board, calculate its aspect ratio, set the value range of the initial viscosity and the final viscosity of the filling material, construct a viscosity gradient function, and use the via hole filling quality evaluation index as the first optimization target and the filling material ratio as the first optimization variable to solve the optimal ratio; A vacuum process control module, used to respectively establish a first relationship model and a second relationship model between vacuum degree and filling rate, and between vacuum degree and gas pressure of the via, and to design a vacuum control strategy based on the first relationship model and the second relationship model, so as to calculate a pressure control threshold of the vacuum process and a target vacuum degree at each moment; Ultrasonic assisted filling module, used to obtain the capillary pressure at the current moment, calculate the pressure difference driving force according to the gas pressure of the via hole at the current moment, calculate the time required for filling in combination with the via hole diameter and hole depth and viscosity gradient function, preset the ultrasonic vibration duration, and perform ultrasonic assisted filling while the via hole is being filled; A real-time filling control module is used to obtain a filling material according to an optimal ratio and a viscosity gradient function to fill the via hole, and to control the vacuum degree of the external vacuum cavity according to a vacuum degree adjustment curve, so as to minimize the deviation between the gas pressure of the via hole and the pressure control threshold; The filling process optimization module is used to obtain the real-time filling rate and cavity volume of the via hole, take the filling steps and the single injection material volume as the second optimization variable, take minimizing the difference between the target filling rate and the actual filling rate and the filling cost as the second optimization goal, construct the second objective function, and solve the optimal filling steps and the optimal single injection material volume.

9. A multilayer circuit board, characterized in that: The multilayer circuit board is manufactured by executing the multilayer circuit board manufacturing method based on via hole filling optimization as claimed in any one of claims 1 to 7 using the multilayer circuit board manufacturing system based on via hole filling optimization as claimed in claim 8.

Images