Method for manufacturing multilayer PCB and multilayer PCB board
Patent Information
- Application Number
- CN202611121643.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-27
- Publication Date
- 2026-09-15
Smart Images
Figure CN122765879A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of circuit board manufacturing technology, and in particular relates to the fabrication of a multilayer PCB and a multilayer PCB board. Background Technology
[0002] In the manufacturing process of multilayer PCBs, laminating multiple substrates into a single unit is a core technological step. Due to the differences in thermal expansion behavior of different material layers during hot lamination, the laminated PCB often warps, severely affecting the flatness of the product and the reliability of subsequent assembly. Currently, existing solutions use copper-clad laminates with one side of the copper layer completely etched away to replace conventional single-layer copper foil, creating a symmetrical distribution of the physical thickness of the structure to be laminated about the mid-section. However, the number and placement of the pseudo-double-layer substrates are predetermined by a fixed formula for the target number of layers, which cannot adapt to the actual fluctuations in material properties such as the coefficient of thermal expansion and the modulus of elasticity of different batches of boards, representing a static rule-based decision. When etching the sides of the double-layer substrates, the method of removing the entire copper layer is used, without considering the non-uniformity of stress distribution in the laminated structure; excessive etching can actually weaken local mechanical strength. The entire pseudo-double-layer substrate configuration process lacks a quantitative evaluation method for the actual material properties and stress state of each layer in the current structure to be laminated, making it impossible to customize the optimal configuration for each batch and each specific structural combination. Therefore, there is an urgent need for a PCB manufacturing method that can dynamically determine the optimal configuration of the pseudo-double-layer substrate based on the actual stress distribution of each layer of the current structure to be laminated, and accurately remove the copper layer in a patterned manner. This would solve the problems of existing solutions using fixed rules, which cannot be dynamically optimized according to the actual stress symmetry of the current structure to be laminated, and the fact that the copper layer removal on the missing surface using the whole-surface etching method cannot match the requirements of non-uniform stress distribution, resulting in limited warpage suppression effect and weakened local mechanical strength. Summary of the Invention
[0003] This application provides a method for manufacturing a multilayer PCB, which solves the problems of existing solutions that use fixed rules, cannot dynamically optimize based on the actual stress symmetry of the structure to be laminated, and whose full-surface etching method for removing missing copper layers cannot match the requirements of non-uniform stress distribution, resulting in limited warpage suppression and weakened local mechanical strength. By evaluating the stress symmetry after copper layer removal on each side of each bilayer substrate to optimally determine the target side, and discretizing the target side into several micro-regions, a corresponding etching strategy is determined and executed based on the local stress compensation requirements of each micro-region, forming a patterned pseudo-bilayer substrate. This patterned pseudo-bilayer substrate is then laminated with other substrates to produce a multilayer PCB. This method solves the problems of existing solutions that use fixed rules, cannot dynamically optimize based on the actual stress symmetry of the structure to be laminated, and whose full-surface etching method for removing missing copper layers cannot match the requirements of non-uniform stress distribution, resulting in limited warpage suppression and weakened local mechanical strength.
[0004] In a first aspect, embodiments of this application provide a method for manufacturing a multilayer PCB, the method comprising the following steps: For each side of each double-layer substrate, the stress symmetry corresponding to the structural state after the copper layer is removed from the side is evaluated. Based on the evaluation results of each side, the missing side selected as the pseudo double-layer substrate is determined as the target side. The target side is discretized into several micro-regions. The etching strategy of each micro-region is determined according to the local stress compensation requirements of each micro-region. The etching strategy is executed to etch the target side to obtain a patterned pseudo-double-layer substrate. The patterned pseudo-double-layer substrate is laminated with other substrates to obtain a multilayer PCB.
[0005] Optionally, the evaluation of the stress symmetry corresponding to the structural state after the copper layer is removed on each side of each double-layer substrate specifically includes: Obtain the material property parameters of each double-layer substrate in the structure to be laminated, and calculate the interlayer stress asymmetry of each double-layer substrate based on the material property parameters; The global symmetry score corresponding to the structural state after the copper layer is removed from each side of each double-layer substrate is calculated. The global symmetry score is used to characterize the stress symmetry of the overall structure to be laminated after the copper layer is removed.
[0006] Optionally, determining the missing surface selected as the target surface of the pseudo-double-layer substrate based on the evaluation results of each of the said sides specifically includes: The side corresponding to the structural state that minimizes the global symmetry score is selected as the target side.
[0007] Optionally, the interlayer stress asymmetry is calculated as follows: For each double-layer substrate, calculate the ratio of the product of the equivalent elastic modulus and equivalent thermal expansion coefficient on both sides of the double-layer substrate and the thickness of the metal layer to the total thickness of the substrate. The absolute value of the difference between the two sides is taken as the interlayer stress asymmetry of the double-layer substrate.
[0008] Optionally, discretizing the target side into several micro-regions specifically includes: The target side is divided into several grid units according to a preset spatial resolution, which serve as the initial micro-regions of the target side. Finite element simulation was performed on each of the initial microregions to calculate the local theoretical shrinkage driving force of each initial microregion under the compression thermal process. Based on the local theoretical contraction driving force, the initial micro-region is adjusted to obtain the final micro-region on the target side.
[0009] Optionally, determining the etching strategy for each micro-region based on its local stress compensation requirements specifically includes: Calculate the statistical baseline value of the local theoretical contraction driving force of all final micro-regions on the side of the target; If the local theoretical shrinkage driving force of the final micro-region is greater than the statistical benchmark value, then the final micro-region is determined to be a high stress compensation demand area, and copper layer removal is performed. If the local theoretical shrinkage driving force of the final micro-region is less than or equal to the statistical benchmark value, then the final micro-region is determined to be a low stress compensation requirement area, and the copper layer is retained.
[0010] Optionally, the step of laminating the patterned pseudo-double-layer substrate with other substrates to obtain a multilayer PCB specifically includes: During the lamination process of the patterned pseudo-double-layer substrate with other substrates, the instantaneous stress values at each position of the lamination structure are collected in real time by a distributed stress sensor array embedded in the lamination structure. The instantaneous warping trend and action threshold are calculated based on the instantaneous stress value; When the instantaneous warping trend is greater than or equal to the action threshold, a dynamic compensation action is performed until the instantaneous warping trend falls back below the action threshold, and a multilayer PCB is obtained by lamination.
[0011] Optionally, the step of calculating the instantaneous warping trend and action threshold based on the instantaneous stress value specifically includes: Calculate the difference in instantaneous stress values at corresponding positions on both sides of the cross section, and calculate the integral of the absolute value of this difference on the plane of the pressed structure as the instantaneous warping trend; For each final micro-region, the local root mean square error of the instantaneous stress value within that final micro-region is calculated, and the maximum value of the local root mean square error of each final micro-region is used as the action threshold for the current sampling period; or, the weighted average of the local root mean square errors of each final micro-region is used as the action threshold for the current sampling period.
[0012] Optionally, the execution of the dynamic compensation action specifically includes: When the instantaneous warping trend is greater than or equal to the action threshold, it is determined whether the difference between the average instantaneous stresses on both sides of the mid-section exceeds the current action threshold. If the average instantaneous stress on one side of the cross section is higher than that on the other side and the difference exceeds the current action threshold, the heating power of the local area of the hot plate corresponding to the side with higher stress will be reduced by the zoned temperature control system. If the side with higher stress is the missing side of the pseudo-double-layer substrate, the micro-injection device built into the press is activated to inject thermosetting resin compensator into the edge of the adjacent semi-cured sheet on the side with higher stress, so as to change the stress distribution characteristics of the local area of the hot press plate.
[0013] Secondly, embodiments of the present invention also provide a multilayer PCB board, which is manufactured using the multilayer PCB manufacturing method provided in embodiments of the present invention.
[0014] The above-mentioned solution of this application has the following beneficial effects: For each side of each double-layer substrate, the stress symmetry corresponding to the structural state after the copper layer is removed from the side is evaluated. Based on the evaluation results of each side, the missing side selected as the pseudo double-layer substrate is determined as the target side. The target side is discretized into several micro-regions. The etching strategy of each micro-region is determined according to the local stress compensation requirements of each micro-region. The etching strategy is executed to etch the target side to obtain a patterned pseudo double-layer substrate. The patterned pseudo double-layer substrate is laminated with other substrates to obtain a multilayer PCB. By evaluating the stress symmetry after copper layer removal on each side of each double-layer substrate to optimally determine the target side, the target side is discretized into several micro-regions. The corresponding etching strategy is determined and executed according to the local stress compensation requirements of each micro-region to form a patterned pseudo-double-layer substrate. The patterned pseudo-double-layer substrate is then laminated with other substrates to produce a multi-layer PCB. This solves the problems of existing solutions that use fixed rules and cannot be dynamically optimized according to the actual stress symmetry state of the current structure to be laminated, and that the copper layer removal on the missing side using the whole-surface etching method cannot match the requirements of non-uniform stress distribution, resulting in limited warpage suppression effect and weakened local mechanical strength.
[0015] Other beneficial effects of this application will be described in detail in the following detailed description section. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 This is a flowchart illustrating a method for manufacturing a multilayer PCB according to an embodiment of this application. Detailed Implementation
[0018] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.
[0019] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.
[0020] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.
[0021] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."
[0022] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0023] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.
[0024] like Figure 1 As shown, Figure 1 This is a flowchart of a method for manufacturing a multilayer PCB according to an embodiment of the present invention. The method for manufacturing a multilayer PCB includes the following steps: 101. For each side of each double-layer substrate, evaluate the stress symmetry corresponding to the structural state after the copper layer is removed from the side. Based on the evaluation results of each side, determine the missing side selected as the pseudo double-layer substrate as the target side.
[0025] In this embodiment of the invention, the above-described method for manufacturing a multilayer PCB can be applied to a multilayer PCB board. The multilayer PCB board is a printed circuit board formed by stacking multiple substrate layers through a thermo-pressing process. The interior of the multilayer PCB board contains alternating conductive lines and insulating dielectric layers. The thermo-pressing process involves bonding multiple double-layer substrates, prepregs, and other functional layer materials into a single multilayer PCB board under high temperature and pressure through heating and pressurization. The core function of the conductive lines is to transmit electrical signals, carry current, and achieve electrical interconnection between various electronic components. The insulating dielectric layer prevents short circuits between different conductive layers; it provides sufficient rigidity and thickness to the PCB board; and it flows and fills gaps during thermo-pressing, firmly bonding the conductive lines into a single unit.
[0026] The aforementioned double-layer substrate can be a basic unit for constructing a multilayer PCB. The double-layer substrate structure is a copper-clad laminate structure formed by covering both sides of an insulating dielectric layer with copper layers. Each double-layer substrate has two opposite sides, and each side is covered with a copper layer.
[0027] The aforementioned pseudo-double-layer substrate can be a structure formed by removing the copper layer from one side of a complete double-layer substrate. Due to the asymmetry in the thickness of the copper layers on both sides, the pseudo-double-layer substrate has specific stress compensation characteristics and is placed in the structure to be laminated to adjust the overall stress balance.
[0028] The aforementioned missing surface can be the side selected in a pseudo-double-layer substrate where the copper layer has been removed.
[0029] The aforementioned target side can be the missing side selected as a pseudo-double-layer substrate.
[0030] The aforementioned stress symmetry can be used to quantitatively evaluate the symmetry of the stress distribution of the entire structure to be laminated with respect to its cross-section after the copper layer has been removed from one side of a double-layer substrate. A higher degree of stress symmetry results in a lower risk of warping after lamination.
[0031] It should be noted that by evaluating the stress symmetry after copper layer removal for each side of each double-layer substrate, and determining the missing side selected as the target side based on the evaluation results, dynamic optimization of the selection of the missing side of the false double-layer substrate is achieved, so that the determination of the missing side no longer depends on fixed rules.
[0032] 102. Discretize the target side into several micro-regions, determine the etching strategy for each micro-region according to the local stress compensation requirements of each micro-region, and execute the etching strategy to etch the target side to obtain a patterned pseudo double-layer substrate.
[0033] In this embodiment of the invention, the aforementioned micro-region can be a number of small regional units into which the target side is divided on a two-dimensional plane according to spatial resolution. Each micro-region, as an independent etching decision unit, can be individually designated to remove or retain the copper layer.
[0034] The aforementioned localized stress compensation requirement can refer to the extent of copper layer removal needed at local locations within each micro-region to balance the stress distribution in the laminated structure. The stress compensation requirements differ between different micro-regions; areas with higher stress require copper layer removal to release stress, while areas with lower stress do not require removal.
[0035] The above etching strategies can be copper layer processing methods determined for each micro-region. Etching strategies include removing the copper layer, retaining the copper layer, partially thinning the copper layer, and surface roughening treatment.
[0036] The aforementioned patterned pseudo-double-layer substrate can be a pseudo-double-layer substrate morphology obtained by etching each micro-region on the target side according to an etching strategy. In the pseudo-double-layer substrate morphology, the copper layer on the target side is not completely removed, but rather exhibits a patterned distribution where the high-stress areas expose the dielectric and the low-stress areas retain the copper layer.
[0037] It should be noted that by discretizing the target side into several micro-regions and determining the etching strategy for each micro-region based on the local stress compensation requirements of each micro-region before performing etching, the copper layer removal on the target side is no longer carried out by removing the entire surface. Instead, a patterned distribution is formed in which high-stress areas are removed and low-stress areas are retained, thus achieving a precise match between the amount of material removed and the local stress compensation requirements.
[0038] 103. The patterned pseudo-double-layer substrate is laminated with other substrates to obtain a multilayer PCB.
[0039] In this embodiment of the invention, the other substrates mentioned above include conventional double-layer substrates, inner layer boards with etched circuit patterns, prepregs, and single-layer copper foil, as well as other structural units required to form a multilayer PCB.
[0040] The above-mentioned lamination can be a process in which a patterned pseudo-double-layer substrate and other substrates are bonded together by melting and curing a prepreg under high temperature and high pressure conditions.
[0041] It should be noted that by laminating a patterned pseudo-double-layer substrate with other substrates to obtain a multilayer PCB, the lamination warpage is suppressed by a combination of adaptive optimization of missing surfaces and patterned etching, thereby improving the flatness of the PCB product.
[0042] In this embodiment of the invention, after forming a patterned pseudo-double-layer substrate, the patterned pseudo-double-layer substrate is laminated with other substrates to obtain a multilayer PCB. The laminated multilayer PCB has achieved the optimal configuration of stress balance at the structural level, thereby effectively suppressing warping deformation.
[0043] In this embodiment of the invention, for each side of each bilayer substrate, the stress symmetry corresponding to the structural state after the copper layer is removed is evaluated. Based on the evaluation results of each side, the missing surface selected as the target side of the pseudo bilayer substrate is determined. The target side is discretized into several micro-regions, and the etching strategy of each micro-region is determined according to the local stress compensation requirements of each micro-region. The etching strategy is executed to etch the target side to obtain a patterned pseudo bilayer substrate. The patterned pseudo bilayer substrate is then laminated with other substrates to obtain a multilayer PCB. By evaluating the stress symmetry after copper layer removal for each side of each bilayer substrate to optimally determine the target side, discretizing the target side into several micro-regions, determining the corresponding etching strategy according to the local stress compensation requirements of each micro-region, and executing it to form a patterned pseudo bilayer substrate, and then laminating the patterned pseudo bilayer substrate with other substrates to produce a multilayer PCB, this invention solves the problems of existing solutions using fixed rules, which cannot dynamically optimize according to the actual stress symmetry state of the current structure to be laminated, and the use of whole-surface etching for removing the copper layer on the missing surface, which cannot match the requirements of non-uniform stress distribution, resulting in limited warpage suppression effect and weakened local mechanical strength.
[0044] It is understood that in the specific implementation of this application, data such as side data, strategy data, and etching data are involved. When the embodiments in this application are applied to specific products or technologies, user permission or consent is required. Furthermore, the collection, use, and processing of related data, as well as the training, deployment, and invocation of algorithm models, must comply with the relevant laws, regulations, and standards of the relevant countries and regions.
[0045] Optionally, in the step of evaluating the stress symmetry of the structural state after the copper layer is removed from each side of each double-layer substrate, the material property parameters of each double-layer substrate in the structure to be laminated can be obtained, and the interlayer stress asymmetry of each double-layer substrate can be calculated based on the material property parameters; and the global symmetry score corresponding to the structural state after the copper layer is removed from each side of each double-layer substrate can be calculated respectively.
[0046] In this embodiment of the invention, the structure to be laminated can be a stacked combination of all structural units to be laminated into a multilayer PCB. The structure to be laminated includes multiple double-layer substrates and necessary prepreg, copper foil, and other constituent units.
[0047] The aforementioned material property parameters are a set of quantitative indicators used to characterize the physical properties of each double-layer substrate in the structure to be laminated. These material property parameters include the thickness of the copper and dielectric layers on both sides of the double-layer substrate, the elastic modulus and coefficient of thermal expansion of each layer, and the total thickness of the substrate.
[0048] The interlayer stress asymmetry mentioned above is a numerical index used to quantify the degree of asymmetry in the stress distribution within a single bilayer substrate about its own cross-section. The higher the interlayer stress asymmetry, the more asymmetrical the bilayer substrate itself is, and the more easily internal stress imbalance will occur during the lamination process.
[0049] The global symmetry score described above is used to characterize the overall stress symmetry of the structure to be laminated after the copper layer is removed. The global symmetry score is obtained by summing the squares of the differences in stress asymmetry between layers at symmetrical locations. The smaller the score, the higher the overall stress symmetry of the structure; the larger the score, the worse the overall structural symmetry and the higher the risk of warping.
[0050] Specifically, the global symmetry score can be represented as: in, For global symmetry scoring, For the first Interlayer stress asymmetry of a double-layer substrate In order to be with the first The interlayer stress asymmetry of bilayer substrates at symmetrical locations on each substrate, wherein... and These are two substrates positioned symmetrically about the midsection.
[0051] It should be noted that by calculating the interlayer stress asymmetry of each double-layer substrate based on material property parameters, the difference in stress contribution between the upper and lower sides of a single double-layer substrate is accurately quantified. By calculating the global symmetry score corresponding to the structural state after the copper layer is removed from each side of each double-layer substrate, the system can quantitatively compare the overall stress balance effect after the removal of each side of each substrate, providing a standardized quantitative decision basis for selecting the optimal target side.
[0052] Optionally, in the step of determining the missing surface selected as the target side of the pseudo-double-layer substrate based on the evaluation results of each side, the side corresponding to the structural state that minimizes the global symmetry score can be selected as the target side.
[0053] In this embodiment of the invention, the minimum global symmetry score can be the smallest global symmetry score obtained after comparing the evaluation results of all sides of all double-layer substrates. The lower the global symmetry score, the closer the stress distribution of the entire structure to be laminated is to perfect symmetry after the copper layer on the sides is removed, and the lower the risk of warping after lamination.
[0054] The aforementioned target side can be selected by comparing the evaluation results of each side and choosing the side corresponding to the structural state that minimizes the global symmetry score.
[0055] Understandably, by using global symmetry scoring as a unified selection criterion, the optimal decision-making on the target side is kept strictly consistent with the physical meaning of stress symmetry, thus avoiding inappropriate selection due to the disconnect between decision rules and evaluation indicators.
[0056] It should be noted that the global symmetry score is calculated based on the actual material properties of each double-layer substrate. When different batches of copper-clad laminates differ in their coefficient of thermal expansion, elastic modulus, or thickness, the global symmetry score of each side will change accordingly. By minimizing the selection, adaptive optimization of the target side is achieved.
[0057] Optionally, the interlayer stress asymmetry can be calculated as follows: For each double-layer substrate, calculate the ratio of the product of the equivalent elastic modulus and equivalent thermal expansion coefficient on both sides of the double-layer substrate and the thickness of the metal layer to the total thickness of the substrate. The absolute value of the difference between the two sides is taken as the interlayer stress asymmetry of the double-layer substrate.
[0058] In this embodiment of the invention, the aforementioned double-layer substrate is the basic unit constituting a multilayer PCB. The double-layer substrate structure is a copper-clad laminate structure formed by covering both sides of an insulating dielectric layer with copper layers. Each double-layer substrate has two opposing sides, namely a first side and a second side, each side being covered with a copper layer. The first side can be the upper side, i.e., the side facing upward in the stacking direction; the second side can be the lower side, i.e., the side facing downward in the stacking direction.
[0059] The aforementioned equivalent elastic modulus can be considered as an equivalent measure of the ability of a composite material to resist elastic deformation when subjected to external forces, after considering the copper layer and the adjacent dielectric layer on one side of a double-layer substrate as a whole composite.
[0060] The aforementioned equivalent coefficient of thermal expansion can be considered as an integral composite material, where the copper layer and the adjacent dielectric layer on one side of the bilayer substrate are regarded as an integral composite material, and the equivalent elongation per unit length of the composite material under temperature changes.
[0061] The aforementioned metal layer thickness can be the actual physical thickness of the copper layer covering one side of the double-layer substrate.
[0062] The total thickness of the substrate can be the total thickness of a double-layer substrate.
[0063] Specifically, the interlayer stress asymmetry can be expressed as: in, This refers to the interlayer stress asymmetry. For the first The equivalent elastic modulus of the copper layer and dielectric layer composite on the upper side of the substrate. For the first The equivalent coefficient of thermal expansion of the composite on the upper side of the substrate within the pressing temperature range. For the first The thickness of the copper layer on the upper side of the substrate For the first The equivalent elastic modulus of the composite on the lower side of the substrate. For the first The equivalent thermal expansion coefficient of the composite material on the lower side of the substrate. For the first The thickness of the copper layer on the underside of the substrate For the first The total thickness of each substrate.
[0064] The interlayer stress asymmetry mentioned above is a numerical index used to quantify the degree of asymmetry in the stress distribution within a single bilayer substrate about its own cross-section. The higher the interlayer stress asymmetry, the more asymmetrical the bilayer substrate itself is, and the more easily internal stress imbalance will occur during the lamination process.
[0065] Optionally, in the step of discretizing the target side into several micro-regions, the target side can be divided into several grid units according to a preset spatial resolution as the initial micro-regions of the target side; finite element simulation is performed on each initial micro-region to calculate the local theoretical shrinkage driving force of each initial micro-region under the compression thermal process; based on the local theoretical shrinkage driving force, the initial micro-regions are adjusted to obtain the final micro-regions of the target side.
[0066] In this embodiment of the invention, the target side can be a missing side selected as a pseudo-double-layer substrate.
[0067] The aforementioned preset spatial resolution can be a pre-defined spatial resolution. The spatial resolution is used to determine the basic size of the initial micro-region. The spatial resolution can be 1mm × 1mm, etc.
[0068] The aforementioned grid unit can be several basic region units formed by dividing the side of the target according to a preset spatial resolution, and each grid unit has the same initial size and shape.
[0069] The aforementioned initial micro-region can be a collection of several grid cells obtained by dividing the side of the target according to a preset spatial resolution.
[0070] The aforementioned finite element simulation is a numerical analysis method that discretizes a continuous structure into a finite number of elements and simulates the mechanical response of the structure under given loads and boundary conditions by solving mechanical equations. Finite element simulation is used to simulate the thermo-mechanical coupling behavior of each micro-region on the side of the target under the compression thermal process, in order to calculate the contraction driving force borne by each initial micro-region.
[0071] The aforementioned thermal history of compression can be a complete curve of temperature change over time experienced by each initial micro-region during the compression process, including the heating stage, the holding stage, and the cooling stage. As the thermal load input for finite element simulation, the thermal history of compression determines the stress evolution of each initial micro-region due to differences in thermal expansion.
[0072] The aforementioned local theoretical shrinkage driving force can be the theoretical driving force value generated by the thermal shrinkage behavior of the material in each initial micro-region during the compression thermal process. The local theoretical shrinkage driving force reflects the intensity of the shrinkage effect exerted by each micro-region on adjacent regions during the compression process.
[0073] The aforementioned adjustments can be a process of readjusting the boundaries and sizes of initial micro-regions based on the distribution characteristics of the local theoretical shrinkage driving force of each initial micro-region. These adjustments may include adjusting the micro-region boundary positions to align them with the contour lines of the local theoretical shrinkage driving force, merging adjacent initial micro-regions with similar shrinkage driving force values into larger units, or further subdividing initial micro-regions in regions with large theoretical shrinkage driving force gradients into smaller units to improve the etching control accuracy of the region.
[0074] The aforementioned final micro-region can be the final micro-region division result of the target side obtained by adjusting the initial micro-region based on the local theoretical contraction driving force.
[0075] It should be noted that by performing finite element simulation on each initial micro-region and calculating the local theoretical contraction driving force, the stress intensity at each position on the side of the target was quantitatively perceived. By adjusting the initial micro-region according to the local theoretical contraction driving force, the final micro-region was obtained, realizing the adaptive optimization of the micro-region mesh. This aligned the boundary position of the micro-region with the natural distribution characteristics of the stress field, improving the spatial matching accuracy of subsequent patterned etching and stress compensation requirements.
[0076] Optionally, in the step of determining the etching strategy for each micro-region based on the local stress compensation requirements of each micro-region, a statistical benchmark value of the local theoretical shrinkage driving force of all final micro-regions on the target side can be calculated; if the local theoretical shrinkage driving force of the final micro-region is greater than the statistical benchmark value, then the final micro-region is determined to be a high stress compensation requirement area, and copper layer removal is performed; if the local theoretical shrinkage driving force of the final micro-region is less than or equal to the statistical benchmark value, then the final micro-region is determined to be a low stress compensation requirement area, and copper layer is retained.
[0077] In this embodiment of the invention, the final micro-region can be the final micro-region division result of the target side obtained by adjusting the initial micro-regions according to the local theoretical shrinkage driving force of each initial micro-region under the compression heat process.
[0078] The aforementioned local theoretical shrinkage driving force can be the theoretical driving force value generated by the thermal shrinkage behavior of the material in each initial micro-region under the compression thermal process.
[0079] The aforementioned statistical benchmark values can be obtained through statistical analysis of the local theoretical contraction driving forces of all final micro-regions on the target side. These statistical benchmark values serve as reference boundary values to distinguish between high-stress compensation requirements and low-stress compensation requirements.
[0080] The aforementioned high-stress compensation requirement area can be the final micro-region where the local theoretical shrinkage driving force is greater than the statistical benchmark value. The final micro-region corresponding to the high-stress compensation requirement area has experienced a shrinkage driving force higher than the average level during the compression thermal process, and the copper layer needs to be removed to release stress and prevent warping due to stress concentration.
[0081] The aforementioned low-stress compensation requirement zone can be the final micro-region where the local theoretical shrinkage driving force is less than or equal to the statistical benchmark value. The final micro-region corresponding to the low-stress compensation requirement zone experiences shrinkage driving forces at or below the average level during the thermal bonding process, thus requiring no removal of the copper layer; the copper layer is retained to maintain local mechanical strength.
[0082] The copper layer removal mentioned above can be achieved by chemical etching or other etching processes to completely remove the copper layer on the surface of the micro-area, exposing the dielectric layer in the micro-area and thus releasing the stress in the micro-area.
[0083] The aforementioned retention of the copper layer can be achieved by not performing a copper layer removal operation on the micro-area, maintaining the original copper layer coverage state, so as to preserve the mechanical strength and conductivity of the micro-area.
[0084] It should be noted that by identifying the final micro-area with a local theoretical shrinkage driving force greater than the benchmark value as a high stress compensation demand area and removing the copper layer, and identifying the final micro-area with a local theoretical shrinkage driving force less than or equal to the benchmark value as a low stress compensation demand area and retaining the copper layer, a differentiated matching of the amount of copper layer removed with the change of local stress compensation demand is achieved, avoiding damage to local mechanical strength caused by excessive etching.
[0085] Optionally, in the step of laminating the patterned pseudo-double-layer substrate with other substrates to obtain a multilayer PCB, the instantaneous stress values at each position of the lamination structure can be collected in real time by a distributed stress sensor array embedded in the lamination structure during the lamination process; the instantaneous warping trend and action threshold are calculated based on the instantaneous stress values; when the instantaneous warping trend is greater than or equal to the action threshold, dynamic compensation is performed until the instantaneous warping trend falls back below the action threshold, and the multilayer PCB is obtained by lamination.
[0086] In this embodiment of the invention, the above-mentioned pressing structure can be an integral assembly formed by stacking and assembling a patterned pseudo double-layer substrate with other substrates, which is to be sent into a pressing equipment for hot pressing.
[0087] The aforementioned distributed stress sensor array can refer to a sensing network composed of multiple micro stress sensing units arranged at certain spatial intervals. It is embedded at the interface between the hot press plate and the structure to be pressed or between the prepreg and the substrate, and is in direct contact with the structure to be pressed.
[0088] The instantaneous stress values mentioned above can be the local stress values measured by each sensing unit in the sensor array at the current sampling time. Each set of instantaneous stress values reflects a snapshot of the stress distribution inside the press-fit structure at the current moment.
[0089] The aforementioned instantaneous warping trend can be a numerical indicator calculated based on the instantaneous stress value, used to quantify the tendency or strength of the warping of the press-fit structure at the current moment.
[0090] The aforementioned action threshold can be a dynamic judgment critical value calculated based on the instantaneous stress value. The action threshold represents the upper limit of acceptable symmetrical deviation under the current stress fluctuation level.
[0091] The aforementioned dynamic compensation action can be an active intervention measure taken on the side with higher stress when the instantaneous warping trend is greater than or equal to the action threshold. The purpose of dynamic compensation action is to reduce the stress driving force or change the stress distribution state in the region, so as to restore the overall stress symmetry of the structure to an acceptable level.
[0092] It should be noted that, during the lamination process of the patterned pseudo-double-layer substrate with other substrates, a distributed stress sensor array embedded in the lamination structure collects the instantaneous stress values at various locations of the lamination structure in real time, achieving online, high-resolution real-time sensing of the stress distribution inside the lamination structure. By calculating the instantaneous warping trend and dynamic action threshold in real time based on the instantaneous stress value, an adaptive judgment standard based on the current lamination state is established, enabling the judgment criteria for compensation triggering to be dynamically adjusted according to the changes in the overall stress level during the lamination process. By executing dynamic compensation actions when the instantaneous warping trend is greater than or equal to the action threshold, and continuously monitoring until the warping trend falls back below the action threshold, closed-loop active suppression of stress asymmetry during the lamination process is achieved, allowing the stress compensation effect of the pseudo-double-layer substrate to be dynamically maintained and enhanced during the actual lamination process.
[0093] Optionally, in the step of calculating the instantaneous warping trend and action threshold based on the instantaneous stress value, the difference between the instantaneous stress values at corresponding positions on both sides of the cross section can be calculated, and the integral of the absolute value of the difference on the plane of the pressed structure can be calculated as the instantaneous warping trend; for each final micro-region, the local root mean square error of the instantaneous stress value in the final micro-region can be calculated, and the maximum value of the local root mean square error of each final micro-region can be used as the action threshold of the current sampling period; or, the weighted average of the local root mean square errors of each final micro-region can be used as the action threshold of the current sampling period.
[0094] In this embodiment of the invention, the aforementioned mid-section can be the central symmetry plane of the structure to be pressed in the thickness direction. The corresponding positions on both sides can be two points symmetrical about the midsection.
[0095] The integration of the absolute value of the above difference on the plane refers to the operation of summing or integrating the absolute values of the differences between all symmetrical pairs of positions within the structural plane.
[0096] Specifically, the instantaneous warping trend is obtained by calculating the integral of the absolute value of the difference between the instantaneous stress values at corresponding positions on both sides of the cross section on the plane of the pressed structure. The massive stress sensing data scattered throughout the entire structural plane is integrated into the instantaneous warping trend, which improves the assessment of the warping trend from qualitative observation to precise quantitative analysis.
[0097] The aforementioned final micro-region can be the final micro-region division result of the target side obtained by adjusting the initial micro-regions based on the local theoretical shrinkage driving force of each initial micro-region under the compression heat process.
[0098] The aforementioned local root mean square error (RMSE) refers to the statistical measure of the dispersion of the instantaneous stress values measured by each sensing unit relative to the average stress value of the final micro-region within its spatial range. A larger RMSE indicates a more uneven stress distribution within the final micro-region, with localized stress concentrations or severe fluctuations; a smaller RMSE indicates a more uniform stress distribution within the final micro-region.
[0099] The aforementioned weighted average can be achieved by assigning a weighting coefficient to the local root mean square error of each final micro-region and then summing the results. It is understandable that the weighting coefficient can be set based on factors such as the area of each final micro-region, its importance in the structure, or its criticality in the process.
[0100] Understandably, the final micro-region with the maximum value in the local root mean square error represents the area with the most intense and uneven stress fluctuations on the entire structural plane.
[0101] It should be noted that by calculating the local root mean square error for each final micro-region, the local root mean square error reflects the dispersion of stress distribution within the final micro-region. A large root mean square error indicates that the stress fluctuation within the final micro-region is severe, and it should contribute more to the action threshold. By calculating the local root mean square error for each final micro-region, the determination of the action threshold is no longer based on a coarse method using a single global statistic, but rather the calculation of the action threshold has micro-region-level spatial resolution.
[0102] Furthermore, by using the maximum value of the local root mean square error of each final micro-region as the action threshold for the current sampling period, a worst-case driven safety-oriented threshold setting method is established to ensure that the compensation action is not missed when intervention is most needed, effectively guaranteeing the safety of the pressing quality. By using the weighted average of the local root mean square errors of each final micro-region as the action threshold for the current sampling period, optional threshold sensitivity adjustment means are provided for different application scenarios, enabling the system to flexibly configure the sensitivity of compensation triggering according to process requirements.
[0103] Optionally, in the step of performing dynamic compensation, when the instantaneous warping trend is greater than or equal to the action threshold, it is determined whether the difference between the average instantaneous stress on both sides of the mid-section exceeds the current action threshold; if the average instantaneous stress on one side of the mid-section is higher than that on the other side and the difference exceeds the current action threshold, the heating power of the local area of the hot press plate corresponding to the side with higher stress is reduced by the zoned temperature control system; if the side with higher stress is the missing side of the pseudo double-layer substrate, the micro-injection device built into the press is activated to inject thermosetting resin compensator into the edge of the adjacent semi-cured sheet on the side with higher stress to change the stress distribution characteristics of the local area of the hot press plate.
[0104] In this embodiment of the invention, the average instantaneous stress on both sides of the mid-section can be the average of the instantaneous stress values measured by all sensing units on the upper side of the mid-section, and the average of the instantaneous stress values measured by all sensing units on the lower side of the mid-section. The average instantaneous stress on both sides of the mid-section represents the overall stress level of the upper and lower sides of the structure at the current moment. The difference between the average instantaneous stress on both sides of the mid-section reflects the direction and magnitude of the systematic stress deviation of the structure in the thickness direction.
[0105] The aforementioned current action threshold can be a dynamic judgment critical value calculated based on the local root mean square error of each final micro-region within the current sampling period.
[0106] The aforementioned zoned temperature control system can be a heating system configured in the pressing equipment that can divide the hot press plate into multiple independent temperature control zones and perform differentiated temperature control.
[0107] The aforementioned heating power can be the intensity of heat output applied to the local area of the hot press plate corresponding to the side with high stress by the zoned temperature control system. Reducing the heating power means reducing the heat input to the local area of the hot press plate corresponding to the side with high stress, thereby reducing the stress level in that area.
[0108] The aforementioned pseudo-double-layer substrate can be a structure formed by removing the copper layer from one side of a complete double-layer substrate.
[0109] The missing side of the aforementioned pseudo-double-layer substrate can be the side selected in the pseudo-double-layer substrate where the copper layer has been removed.
[0110] The aforementioned micro-injection device can be a precision injection mechanism capable of injecting micro-volume liquids or gel-like substances into specific edge positions of the press-fit structure.
[0111] The aforementioned prepreg can be a thermosetting material layer located between the substrates in a press-fit structure, which melts and solidifies at high temperature to bond the layers together.
[0112] The aforementioned thermosetting resin compensator can be a resin material of the same type or compatibility as the prepreg, which can be cured by heating and can change the local stress distribution characteristics after curing.
[0113] It should be noted that when the instantaneous warping trend is greater than or equal to the action threshold, it is determined whether the difference between the average instantaneous stress on both sides of the mid-section exceeds the current action threshold. This effectively avoids unnecessary compensation operations when the stress asymmetry is still within an acceptable range. When the average instantaneous stress on one side of the mid-section is higher than that on the other side and the difference exceeds the current action threshold, the heating power of the local area of the hot press plate corresponding to the side with higher stress is reduced by the zoned temperature control system. This achieves refined and spatially differentiated active intervention in the stress distribution of the press-fit structure, suppressing the deterioration of stress asymmetry from the source of thermal driving force. When the side with higher stress is the missing side of the pseudo-double-layer substrate, thermosetting resin compensator is injected into the edge of the adjacent prepreg on the side with higher stress through a micro-spraying device. This provides an additional mechanical compensation means for the missing side where the stiffness has decreased due to the removal of the copper layer, so that structural compensation and process compensation can work synergistically.
[0114] This invention also provides a multilayer PCB board, which is manufactured using the multilayer PCB manufacturing method provided in this invention. The multilayer PCB board is a printed circuit board formed by stacking multiple substrate layers through a thermo-pressing process. The interior of the multilayer PCB board includes an alternating structure of conductive lines and insulating dielectric layers.
[0115] In this embodiment of the invention, the aforementioned hot-pressing process can be a process of bonding multiple double-layer substrates, prepregs, and other functional layer materials into a single multilayer PCB board under high temperature and high pressure by heating and pressurizing. The core function of the aforementioned conductive circuit layer is to transmit electrical signals, carry current, and realize electrical interconnection between various electronic components. The aforementioned insulating dielectric layer can prevent short circuits between different conductive layers; the insulating dielectric layer can give the PCB board sufficient rigidity and thickness; the insulating dielectric layer can flow and fill gaps during hot pressing, firmly bonding the conductive circuit layers into a single unit.
[0116] The above description is the preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principles described in this application, and these improvements and modifications should also be considered within the scope of protection of this application.
Claims
1. A method for manufacturing a multilayer PCB, characterized in that, The method includes the following steps: For each side of each double-layer substrate, the stress symmetry corresponding to the structural state after the copper layer is removed from the side is evaluated. Based on the evaluation results of each side, the missing side selected as the pseudo double-layer substrate is determined as the target side. The target side is discretized into several micro-regions. The etching strategy of each micro-region is determined according to the local stress compensation requirements of each micro-region. The etching strategy is executed to etch the target side to obtain a patterned pseudo-double-layer substrate. The patterned pseudo-double-layer substrate is laminated with other substrates to obtain a multilayer PCB.
2. The method for manufacturing a multilayer PCB as described in claim 1, characterized in that, The evaluation of the stress symmetry of the structural state after the copper layer is removed from each side of each double-layer substrate specifically includes: Obtain the material property parameters of each double-layer substrate in the structure to be laminated, and calculate the interlayer stress asymmetry of each double-layer substrate based on the material property parameters; The global symmetry score corresponding to the structural state after the copper layer is removed from each side of each double-layer substrate is calculated. The global symmetry score is used to characterize the stress symmetry of the overall structure to be laminated after the copper layer is removed.
3. The method for manufacturing a multilayer PCB as described in claim 2, characterized in that, The step of determining the missing surface selected as the target surface of the pseudo-double-layer substrate based on the evaluation results of each of the aforementioned surfaces specifically includes: The side corresponding to the structural state that minimizes the global symmetry score is selected as the target side.
4. The method for manufacturing a multilayer PCB as described in claim 3, characterized in that, The interlayer stress asymmetry is calculated as follows: For each double-layer substrate, calculate the ratio of the product of the equivalent elastic modulus and equivalent thermal expansion coefficient on both sides of the double-layer substrate and the thickness of the metal layer to the total thickness of the substrate. The absolute value of the difference between the two sides is taken as the interlayer stress asymmetry of the double-layer substrate.
5. The method for manufacturing a multilayer PCB as described in claim 1, characterized in that, Discretizing the target side into several micro-regions specifically includes: The target side is divided into several grid units according to a preset spatial resolution, which serve as the initial micro-regions of the target side. Finite element simulation was performed on each of the initial microregions to calculate the local theoretical shrinkage driving force of each initial microregion under the compression thermal process. Based on the local theoretical contraction driving force, the initial micro-region is adjusted to obtain the final micro-region on the target side.
6. The method for manufacturing a multilayer PCB as described in claim 5, characterized in that, The determination of the etching strategy for each micro-region based on the local stress compensation requirements of each micro-region specifically includes: Calculate the statistical baseline value of the local theoretical contraction driving force of all final micro-regions on the side of the target; If the local theoretical shrinkage driving force of the final micro-region is greater than the statistical benchmark value, then the final micro-region is determined to be a high stress compensation demand area, and copper layer removal is performed. If the local theoretical shrinkage driving force of the final micro-region is less than or equal to the statistical benchmark value, then the final micro-region is determined to be a low stress compensation requirement area, and the copper layer is retained.
7. The method for manufacturing a multilayer PCB as described in claim 6, characterized in that, The step of laminating the patterned pseudo-double-layer substrate with other substrates to obtain a multilayer PCB specifically includes: During the lamination process of the patterned pseudo-double-layer substrate with other substrates, the instantaneous stress values at each position of the lamination structure are collected in real time by a distributed stress sensor array embedded in the lamination structure. The instantaneous warping trend and action threshold are calculated based on the instantaneous stress value; When the instantaneous warping trend is greater than or equal to the action threshold, a dynamic compensation action is performed until the instantaneous warping trend falls back below the action threshold, and a multilayer PCB is obtained by lamination.
8. The method for manufacturing a multilayer PCB as described in claim 7, characterized in that, The calculation of the instantaneous warping trend and action threshold based on the instantaneous stress value specifically includes: Calculate the difference in instantaneous stress values at corresponding positions on both sides of the cross section, and calculate the integral of the absolute value of this difference on the plane of the pressed structure as the instantaneous warping trend; For each final micro-region, the local root mean square error of the instantaneous stress value within that final micro-region is calculated, and the maximum value of the local root mean square error of each final micro-region is used as the action threshold for the current sampling period; or, the weighted average of the local root mean square errors of each final micro-region is used as the action threshold for the current sampling period.
9. The method for manufacturing a multilayer PCB as described in claim 7, characterized in that, The execution of the dynamic compensation action specifically includes: When the instantaneous warping trend is greater than or equal to the action threshold, it is determined whether the difference between the average instantaneous stresses on both sides of the mid-section exceeds the current action threshold. If the average instantaneous stress on one side of the cross section is higher than that on the other side and the difference exceeds the current action threshold, the heating power of the local area of the hot plate corresponding to the side with higher stress will be reduced by the zoned temperature control system. If the side with higher stress is the missing side of the pseudo-double-layer substrate, the micro-injection device built into the press is activated to inject thermosetting resin compensator into the edge of the adjacent semi-cured sheet on the side with higher stress, so as to change the stress distribution characteristics of the local area of the hot press plate.
10. A multilayer PCB board, characterized in that, It is manufactured using the multilayer PCB fabrication method according to any one of claims 1 to 10.