CN114266182B - Circuit board forming pressure optimization method, system, storage medium and equipment - Google Patents
Circuit board forming pressure optimization method, system, storage medium and equipment Download PDFInfo
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Abstract
The invention provides a circuit board forming pressure optimizing method, a system, a storage medium and equipment, wherein the invention adopts a finite element method, takes the maximum pressure and the depressurization process specification of the circuit board at high temperature and high pressure in the circuit board press-fit forming process as decision variables, takes the minimization of the warp deformation of the circuit board after press-fit forming after mold opening and cooling to the room temperature or the control as required as an optimizing objective function, rapidly and accurately simulates the warp deformation of the circuit board after press-fit is finished to the room temperature, and is beneficial to improving the yield of the circuit board manufacture and the stability and reliability of the service process.
Description
Technical Field
The invention belongs to the technical field of PCB molding and manufacturing, and particularly relates to a circuit board molding pressure optimization method, a system, a storage medium and equipment.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
Along with the development of mobile communication technology, the industry of printed circuit boards (Printed Circuit Boards, abbreviated as PCB) has also rapidly developed. The PCB production integrates world high-tech, the printed circuit production technology adopts new technologies such as liquid photosensitive imaging, direct electroplating, pulse electroplating, laminated multilayer board and the like, and the printed circuit manufacturing process not only needs higher technical and equipment investment, but also needs experience accumulation of technicians and production personnel, so that the PCB is more complex to manufacture and has higher requirements.
The process flow of the multi-layer PCB is shown in fig. 1 and can be divided into eight parts: inner layer circuit, lamination, drilling, hole metallization, outer layer dry film, outer layer circuit, silk screen printing, surface process and post working procedure. Wherein, lamination is a process of bonding each layer of circuit into a whole by utilizing the adhesiveness of the prepreg at high temperature, and the bonding is realized by interdiffusion and permeation between macromolecules on an interface so as to generate interdigitation. In the process production, materials such as copper foil, prepreg, inner layer plate, mirror surface stainless steel plate, isolation plate, kraft paper, outer layer steel plate and the like are overlapped together from bottom to top through positioning holes according to the process requirement. The materials of each layer of the PCB are different in physical and chemical properties, and residual internal stress can be generated after the materials are pressed together, so that the multilayer board is subjected to buckling deformation after demolding. Meanwhile, after the PCB is pressed and formed, various processes such as high temperature, mechanical cutting, wet treatment and the like are carried out, and the processes can also have important influence on the deformation of the PCB. In summary, the reason why the warpage deformation occurs after the PCB is press-molded is complex and various, and therefore, how to reduce or control the deformation caused by the different material characteristics or the processing becomes one of the most important problems faced by PCB manufacturers.
During PCB fabrication and surface mount components, warpage may occur in either the BGA package or the PCB itself. If the BGA package is warped, the corner points of the BGA are subjected to maximum displacement in the thickness direction, which may cause a large number of open circuits and bridging phenomena; if the PCB itself is warped, the circuit board may bend upward or downward, pushing the solder paste inward, which may cause open or short circuits on the other individual component areas. The severely warped PCB may even cause problems such as pillow effect, bridging, etc. to fail when it is reflow soldered to the BGA packaged chip.
In order to solve the problems, the prior art of improving the warpage of the PCB and the chip packaging process by using the finite element method has more researches, but the researches mainly aim at the researches of the warpage deformation of the PCB in the working process and the reflow soldering process, and the researches related to the PCB lamination forming process are rarely performed, and have certain limitations in practical application.
Disclosure of Invention
In order to solve the problems, the invention provides a circuit board forming pressure optimization method, a system, a storage medium and equipment, wherein the invention adopts a finite element method, takes the maximum pressure and the depressurization process specification of the PCB at high temperature and high pressure in the PCB press forming process as decision variables, takes the minimization of the warp deformation of the PCB after press forming after mold opening and cooling to the room temperature or the control as required as an optimization objective function, quickly and accurately simulates the warp deformation of the PCB after press finishing to the room temperature, and is beneficial to improving the yield of PCB manufacture and the stability and reliability of the service process.
According to some embodiments, the present invention employs the following technical solutions:
A circuit board molding pressure optimization method comprises the following steps:
Establishing a simulation model of circuit board press molding, taking the maximum pressure and the depressurization process specification of the circuit board at high temperature and high pressure in the press molding process of the circuit board as decision variables, minimizing the warpage deformation of the circuit board after press molding after mold opening and cooling to room temperature or controlling the warpage deformation as required as an optimization objective function, and numerically solving the stress strain field and the displacement field in the press molding process of the circuit board under different maximum pressures and different depressurization process specification conditions through thermal-chemical-mechanical coupling analysis to obtain the optimal pressure and the optimal depressurization process specification of the circuit board in the high temperature and high pressure stage.
As an alternative implementation mode, the specific process for establishing the simulation model of the circuit board press molding comprises the following steps: the geometric model of the circuit board is built through a graphical interface of the finite element software, or a data file is generated by utilizing the geometric modeling software, then the data file is imported into the finite element software, the CCL base plate, the prepreg and the wiring layers of the circuit board are built layer by layer along the thickness direction according to the lamination sequence, and then geometric partition is carried out on each wiring layer according to the outline size of the circuit board.
As an alternative implementation mode, the specific process for establishing the simulation model of the circuit board press molding comprises the following steps: and establishing a material performance model of the circuit board, geometrically partitioning each wiring layer, defining uniform and equivalent material performance in the partitions to simplify the model, and defining equivalent material performance parameters corresponding to the area according to different copper contents in each partition, so as to macroscopically reflect the non-uniformity of the copper content of the wiring layer in-plane and interlayer distribution, and further reflect the circuit characteristics of the wiring diagram.
As an alternative implementation mode, the specific process for establishing the simulation model of the circuit board press molding comprises the following steps: establishing a unit cell model of the circuit board, establishing a series of unit cell models mixed with copper-resin under the copper content of 0% to 100% for geometric partitions of different copper contents of a wiring layer based on a micro-mechanics theory, and simultaneously establishing periodic boundary conditions for the unit cell model according to the position characteristics of the unit cell model in the macroscopic geometric model of the circuit board, and calculating to obtain equivalent material performance parameters of the unit cell model with different copper contents.
In an alternative embodiment, the process of numerically solving the stress-strain field and the displacement field in the lamination forming process of the circuit board through thermal-chemical-mechanical coupling analysis includes: based on the geometric model, the material performance model and the unit cell model of the circuit board, establishing initial conditions and boundary conditions of mechanical displacement constraint and load, and initial conditions and boundary conditions of heat transfer science according to actual lamination process conditions; and obtaining material performance parameters of the circuit board, including density, specific heat capacity, heat conductivity coefficient, thermal expansion coefficient, chemical shrinkage, modulus, poisson ratio and the like, according to experimental tests, constructing a simulation model of press molding of the circuit board, and carrying out numerical solution on stress, strain and displacement of the circuit board in the press molding process through finite element software.
In an alternative embodiment, the calculation process of the warp deformation amount of the circuit board after press molding and mold opening and cooling to room temperature includes: based on the simulation model of the circuit board press-fit molding, the initial conditions and boundary conditions of heat transfer and mechanics required by the simulation, and the required material performance parameters, adopting the composite material mesomechanics, the composite material thermo-elasticity theory, the composite material structural mechanics and the generalized Max Wei Nian elasticity theory to numerically solve the thermal-chemical-mechanical coupling stress strain field and the displacement field of the circuit board in the press-fit molding process, and further obtaining the maximum relative displacement of the surface of the circuit board in the thickness direction after the press-fit is finished and the die opening is finished through data processing and a graphical interaction interface, namely the required warp deformation.
As a further limitation, in the process of calculating the buckling deformation amount of the circuit board after the die opening after the pressing is finished, the mechanical boundary condition, the thermal conductivity boundary condition and other technological parameters of the cold pressing stage are kept unchanged, the maximum pressure and the depressurization process specifications of the constant high pressure and the constant high temperature stage in the circuit board hot pressing process are optimized, the stress, the strain and the displacement of the circuit board when the die opening is cooled to the room temperature after the pressing are obtained by using a finite element simulation means under different maximum pressures and different depressurization process specifications, the influence of the pressure condition in the circuit board pressing forming process after the circuit board pressing is analyzed, and the aim of optimizing the pressure of the circuit board pressing forming process is achieved.
As an alternative embodiment, the depressurization process specification refers to the pressure relief rate and time requirements of the press pressure relief stage, including the total time of different relief pressures, the pressure magnitude at each moment of the relief pressure stage, etc.
A circuit board molding pressure optimization system comprising:
the model construction module is used for building a simulation model of circuit board compression molding, and comprises a circuit board geometric model, a material performance model of the circuit board and a unit cell model of the circuit board;
The parameter setting module is used for setting parameters required by a thermal-chemical-mechanical coupling stress strain field and a displacement place in the process of numerically solving the circuit board press-fit forming, and comprises the steps of establishing initial conditions and boundary conditions of mechanical displacement constraint and load and initial conditions and boundary conditions of heat transfer science according to actual press-fit process conditions; the material performance parameters of the circuit board, which are obtained according to experimental tests, comprise a plurality of density, specific heat capacity, heat conductivity coefficient, thermal expansion coefficient, chemical shrinkage rate, modulus and poisson ratio;
And the optimization solving module is used for taking the maximum pressure and the depressurization process specification thereof during the circuit board compression molding process as decision variables, minimizing the warpage deformation of the circuit board after compression molding after mold opening and cooling to room temperature or controlling the warpage deformation as required as an optimization objective function, and respectively carrying out numerical simulation on the circuit board compression molding process under different maximum pressures and different depressurization process specifications by utilizing a finite element simulation method to obtain the optimal pressure and the optimal depressurization process specification of the circuit board molding under the current high-temperature high-pressure conditions.
An electronic device comprising a memory and a processor and computer instructions stored on the memory and running on the processor, which when executed by the processor, perform the steps of the above method.
A computer readable storage medium storing computer instructions which, when executed by a processor, perform the steps of the above method.
Compared with the prior art, the invention has the beneficial effects that:
The invention establishes a finite element simulation method in the PCB press molding process, which is used for improving the warp deformation after the PCB press molding, namely reducing the warp deformation after the PCB press molding by changing the maximum pressure and the depressurization process specification in the press stage without repeated experimental test improvement process, thereby effectively reducing the cost, providing theoretical guidance for the design of PCB products and improving the stability of the subsequent processing process of the PCB.
The invention establishes a mathematical model of multilayer PCB press molding, is used for providing theoretical support for finite element simulation in the PCB press molding process with larger size, and takes the minimum warp deformation amount of the PCB press molding die opening cooled to room temperature or the control as required as an objective function by means of computer software and a numerical calculation method to finish the aim of optimizing the pressure in the PCB press molding process.
In order to make the above objects, features and advantages of the present invention more comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 is a process flow diagram of a multi-layer PCB manufacturing process;
FIG. 2 is a schematic diagram of a PCB press-fit finite element modeling technique according to the present invention;
FIG. 3 is a graph showing the temperature and resin curing degree with time obtained by simulation at the PCB lamination stage according to the first embodiment;
FIG. 4 shows the pressure history applied to the upper platen by the four example pressing processes according to the first embodiment;
fig. 5 is a simulation result and an experimental result of the relative buckling deformation amount of the PCB cooled to room temperature under the maximum pressures of the four embodiments in the hot pressing stage;
fig. 6 is a time-dependent curve of the PCB surface temperature during the lamination stage for three sets of examples related to the second embodiment;
FIG. 7 shows the pressure history applied to the upper platen during the pressing stage according to the third embodiment of the second embodiment;
Fig. 8 shows simulation results and experimental results of the relative warpage amounts of the PCB cooled to room temperature under the different pressure reduction process specifications at the hot press stage according to the three examples of the second embodiment.
The specific embodiment is as follows:
The invention will be further described with reference to the drawings and examples.
It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
The invention adopts a finite element method, takes the maximum pressure and the depressurization process specification of the high temperature and high pressure stage in the PCB press molding process as decision variables, minimizes the warp deformation of the PCB after press molding and mold opening cooling to the room temperature or controls the warp deformation as required as an optimized objective function, rapidly and accurately simulates the warp deformation of the PCB after press molding and cooling to the room temperature, verifies the warp deformation result of the PCB under the same condition with the experimental test warp result, and then uses the warp deformation result to improve the press molding process specification in the actual production process, thereby achieving the purposes of improving the yield of the PCB in the manufacturing process and the reliability and stability of the in-service process.
The invention adopts the basic thought of 'equal-side length partition and isotropy in the partition', and establishes a geometric model and a material performance model of the PCB, and the specific contents include: and establishing a geometric model of the CCL substrate, the prepreg and the wiring layers of the PCB layer by layer according to a lamination sequence, geometrically partitioning each layer of wiring layer, establishing equivalent material performance parameters in each partition according to the volume content of copper in each partition, and performing numerical simulation on the evolution of the warp deformation in the PCB press-fit forming process, wherein a specific numerical simulation technical route is shown in figure 2.
A pressure optimization method for reducing warp deformation in PCB press forming process comprises the following steps:
(1) Establishing a geometric model of PCB press molding: the invention adopts a modeling thought of partition and layering, a geometric model is built layer by a CCL substrate, a prepreg and wiring layers (same copper-resin mixed layers) of the PCB according to a lamination sequence, then each wiring layer is geometrically partitioned according to the outline size of the circuit board, and meanwhile, an upper pressing plate and a lower pressing plate are used as a die structure.
(2) Establishing an equivalent material performance model in the PCB partition: the geometric partition of each wiring layer is defined with uniform and equivalent material performance to simplify the model, and different equivalent performance parameters of the area are defined according to different copper contents in the partition, so that the non-uniformity of the copper content distribution of the wiring layer in the plane and between layers is shown macroscopically. Based on the micro-mechanics theory, a series of copper-resin mixed unit cell models under different copper contents are established for the partitions of the wiring layers, and meanwhile, periodic boundary conditions are established for the unit cell models according to the position characteristics of the unit cell models in the PCB macroscopic finite element model, and equivalent performance parameters of the unit cell models with different copper contents are obtained through calculation.
(3) Establishing a simulation model of PCB press molding: based on a geometric model, a material performance model and a single cell model of the PCB, establishing initial conditions and boundary conditions of mechanical displacement constraint and load, and initial conditions and boundary conditions of heat transfer science according to actual lamination process conditions; and obtaining material performance parameters of the circuit board according to experimental tests, including density, specific heat capacity, heat conductivity coefficient, thermal expansion coefficient, chemical shrinkage rate, modulus, poisson ratio and the like, and inputting the material performance parameters into finite element software.
The simulation model of the circuit board press-fit molding comprises a unit cell model of the circuit board and a geometric model of the circuit board, wherein the unit cell model of the circuit board is firstly constructed to obtain equivalent material performance parameters corresponding to the unit cell models with different copper contents, then the material properties of the geometric model of the circuit board are endowed in finite element software, and finally the simulation model of the circuit board press-fit molding is jointly constructed.
(4) And (3) calculating a numerical solution: based on a simulation model of PCB press-fit forming, adopting a composite material micromechanics theory, a composite material thermo-elasticity theory, a composite material structural mechanics theory and a generalized Maxwell Wei Nian elasticity theory, and carrying out thermal-chemical-mechanical coupling analysis to numerically solve stress, strain and displacement in the PCB press-fit forming process, and further carrying out data processing and graphical interaction interface calculation to obtain the buckling deformation of the PCB after press-fit finishing, mold opening and cooling to room temperature.
(5) Pressure optimization at high temperature and high pressure in PCB press forming process: based on a simulation model and a numerical calculation method of PCB compression molding, mechanical boundary conditions, heat transfer mechanical boundary conditions and other technological parameters of a cold compression stage are kept unchanged, and pressure conditions (maximum pressure and depressurization technological specifications) of a constant high temperature and constant high pressure stage in the PCB hot compression process are optimized.
The method can utilize finite element simulation means and experimental tests under the same conditions, obtain the simulation result and experimental result of the warping amount of the PCB in the thickness direction when the PCB is cooled to the room temperature by opening the mold under different maximum pressures and different depressurization process specifications, analyze the influence of the pressure conditions of the constant high temperature and constant high pressure stage in the PCB press-fit forming process on the warp deformation after the PCB press-fit through comparison and verification, and determine the optimal pressure conditions and the optimal depressurization process in the PCB press-fit forming process, thereby improving the actual press-fit process.
Of course, in this embodiment, the constant high temperature in the PCB lamination process is the highest temperature of 200 ℃ of the surface layer of the PCB in the hot lamination stage in the simulation process; the constant high pressure in the PCB pressing process is the highest pressure of 2.89MPa of the PCB in the hot pressing stage in the simulation process; the changing of the pressure at the constant high pressure and constant high temperature stage and the pressure reduction process specification thereof in the hot pressing process is to change the maximum pressure and the pressure reduction rate at the high temperature and high pressure in the hot pressing stage.
In other embodiments, however, other settings may be made for the values of the high pressure and high temperature.
A pressure optimization system for reducing warp deformation during compression molding of a PCB, comprising:
The model construction module is used for constructing a PCB geometric model comprising a die structure, an equivalent material performance model in a PCB wiring layer partition, a single cell model of the PCB and a mathematical model of numerical calculation, and the models jointly form a simulation model of the PCB press-fit forming process;
The parameter acquisition module is used for acquiring specific temperature, pressure, time and other technological parameters of a pressing stage in the PCB production process, and acquiring material performance parameters of the PCB, including density, specific heat capacity, heat conductivity coefficient, thermal expansion coefficient, chemical shrinkage rate, modulus, poisson ratio and the like, wherein the actual mechanical constraint, the load initial condition, the heat transfer initial condition and the boundary condition are acquired;
The numerical simulation module is used for performing numerical simulation on the process from press forming to mold opening and cooling to room temperature based on a simulation model of the PCB press forming process, and firstly, chemical reaction heat release and PCB temperature field of the resin are solved by utilizing chemical-thermal coupling analysis; then solving the chemical shrinkage strain and the thermal expansion and contraction strain of the composite material through the micro-mechanics of the composite material and the thermal-elastic theory of the composite material; then, strain and displacement of the PCB in the pressing process are solved by utilizing thermal-chemical-mechanical coupling analysis; and finally solving the buckling deformation of the PCB after finishing pressing and mold opening and cooling to room temperature by using the thermal-viscoelastic theory of the composite material structure mechanics, the anisotropic viscoelastic mechanics and the composite material structure.
The parameter optimization module is used for changing pressure process parameters in the pressing process, including changing the highest pressure and the depressurization process standard of the constant high temperature and constant high pressure stage in the hot pressing process, while other pressing process parameters are unchanged, respectively performing numerical simulation of the PCB pressing process, obtaining buckling deformation sensitivity curves of the PCB pressing under different highest pressures and different depressurization process standards after finishing die opening and cooling to room temperature, and determining the influence degree of the pressure process parameters on the numerical simulation result, thereby achieving the purposes of optimizing the pressure of the PCB high temperature and high pressure molding and reducing the buckling deformation after the PCB pressing molding.
Embodiment one:
In the embodiment, a mobile phone motherboard with a certain outline dimension of 260mm×160mm is used as a research object, firstly, a geometric model is built on the PCB according to a layering and partitioning mode, in the modeling process, irregular geometric characteristics such as bulges and depressions are ignored, a wiring layer of the PCB is equally divided into 20 geometric areas in a 4×5 mode, 8 wiring layers are shared by the PCB, geometric modeling is respectively carried out on a CCL substrate layer, a prepreg and the wiring layer, and different equivalent performance parameters are defined according to copper content corresponding to the position of the partition.
In finite element software, mechanical and thermal initial conditions and boundary conditions are set according to actual lamination process parameters, and corresponding material performance parameters of each layer are respectively given according to different actual lamination layers. The numerical simulation flow comprises the following steps: firstly, a program containing a resin curing reaction kinetic equation and a composite material viscoelasticity constitutive equation is called to calculate the temperature and resin curing degree evolution of the PCB in the process of opening a mold and cooling to room temperature after lamination; and then, a program containing a composite material thermal-elastic theory, a composite material structural mechanics and a generalized Maxwell Wei Nian elastic theory is called to calculate the stress, strain and displacement of the PCB in the pressing process, and the material behaviors such as curing reaction shrinkage, thermal expansion shrinkage and the like of the PCB and the mechanical response under pressure such as stress, strain state, PCB warp deformation state and the like are simulated. The pressing process comprises a hot pressing process 16400s, a cold pressing process 3800s and a process 3000s of mold opening and cooling to room temperature. Fig. 3 is a graph showing the temperature and resin curing degree change with time obtained by the simulation of the PCB during the lamination stage. In the experimental process corresponding to the simulation, the technological parameters and the like in the pressing process are ensured to be consistent with the simulation setting parameters, and the obtained experimental result is compared with the simulation result.
On the basis of the simulation result, the compression force (the pressure which changes along with time) applied on the upper pressing plate is changed, the mechanical boundary condition, the thermal conductivity boundary condition and the technological parameters of the cold compression stage are not modified, the temperature field of the PCB is calculated first, then the temperature field is used as a pre-defined field for stress-strain calculation, the displacement and the distribution of the PCB in the thickness direction when the PCB is cooled to the room temperature after the die opening are further calculated and output, and the buckling deformation of the PCB when the PCB is cooled to the room temperature after the die opening is obtained.
The present embodiment relates to four sets of calculation examples. One group is a control group, namely the maximum pressure of constant temperature and constant pressure in the hot pressing stage of the PCB is set to be 2.89MPa, and the other three groups are used for keeping other conditions unchanged, and the maximum pressures of constant temperature and constant pressure in the hot pressing stage are respectively changed to be 1.45MPa, 2.00MPa and 3.20MPa. The temperature field of the PCB is calculated firstly, and then the temperature field is used as a predefined field for calculating the stress strain field, so that the warp deformation of the PCB after being cooled to the room temperature in a die opening mode is obtained through data processing, and the simulation result is compared with the experimental result, so that the actual press forming process is improved, the production cost is reduced, and the yield of products is improved. FIG. 4 shows the pressure history of the upper platen during the press-fit process for four examples. Fig. 5 shows simulation results and experimental results of the maximum pressure PCB relative to the warpage amount by changing the constant temperature and the constant pressure in the thermal compression stage according to four examples. Table 1 is a time-pressure data table (local) for the upper platen of the four example press-fit process.
Table 1 four sets of examples time-pressure data table (local) for pressing upper plate during pressing
From the above results, it is understood that the warpage amount of the PCB gradually decreases with the increase of the maximum pressure of the high temperature and the high pressure under the same other conditions; the higher the high-temperature and high-pressure maximum pressure is, the more remarkable the strain (pure mechanical strain) which cannot cause the PCB warp deformation is than the strain (mainly chemical shrinkage strain) which can cause the PCB warp deformation, and accordingly the influence degree of the strain (mainly chemical shrinkage strain) which can cause the PCB warp deformation on the PCB warp deformation is weakened in the viscoelastic deformation process of the higher strain. The maximum pressure of high temperature and high pressure is continuously increased, but the safety production pressure and the manufacturing cost are increased, so that the excessive time is not suitable to be prolonged in the actual production process. By properly improving the maximum pressure at high temperature and high pressure in the hot press stage, the proposal for reducing the buckling deformation amount of the PCB in the press molding process is feasible, so the buckling deformation amount of the PCB which is cooled to the room temperature after the press finishing die opening can be reduced according to the optimization design system and the optimization design method.
Embodiment two:
In this embodiment, the same PCB as in embodiment one is used as a study object, and the modeling scheme and the definition of the material parameters are the same as in embodiment one. The embodiment includes three sets of calculation examples, wherein one set is to simultaneously relieve pressure and cool under a high-temperature high-pressure hot-pressing state, the simultaneous relieving pressure and cool refers to cooling the PCB from a certain pressure of 0.69MPa to 774Pa in the hot-pressing stage, cooling from a certain temperature of 198 ℃ to 25 ℃, and the other two sets of the calculation examples have the same hot-pressing process parameters, and the two sets of calculation examples respectively are to maintain the high temperature of 198 ℃ to relieve pressure to 1Pa and 0.1Pa and cool when the pressure of the PCB in the hot-pressing stage is 687055 Pa. Only changing the pressure reduction standard of the hot pressing stage, and not changing the convection heat transfer coefficient and the technological parameters of the cold pressing stage, firstly calculating the temperature field of the PCB, and then taking the temperature field as a pre-defined field for stress strain calculation, thereby calculating and outputting the displacement distribution and the size of the PCB in the thickness direction when the PCB is cooled to the room temperature after die opening. Tables 2, 3 and 4 are time-temperature and time-pressure setting data tables (local) of the current three sets of example temperature fields and corresponding time tables of each stage. Fig. 6 is a graph showing the temperature of the PCB surface over time for three exemplary lamination stages. FIG. 7 shows the pressure history applied to the upper platen during the lamination stage of three examples. Fig. 8 shows simulation results and experimental results of three sets of calculation examples for changing the constant-temperature and constant-high-pressure depressurization process specifications at the hot pressing stage corresponding to the relative warp deformation amount of the PCB.
Table 2 three sets of tables (local) for time-temperature settings of the example thermocompression bonding stage
Table 3 time-pressure setting data table (local) for three sets of example upper press plates
Table 4 corresponding timetable for each stage
From the results, the simulated warp deformation of the PCB is respectively reduced by 10.76% and 10.88% when the pressure is released to 0.1Pa and 1Pa at the same time when the pressure is released and the temperature is reduced at the high temperature and the high pressure in the hot pressing stage. This is probably because the mechanical equilibrium state of the PCB at high temperature and high pressure is broken by the large relief of pressure at high temperature, and the residual thermal stress is not completely relaxed, so that the warpage of the PCB is increased, so the stress relief specification at constant high temperature and constant time has a large influence on the warpage of the PCB. The result of this embodiment shows that the pressure reducing specification at high temperature and high pressure in the hot pressing stage does affect the warp deformation amount after the PCB is pressed and formed, and the scheme of reducing the warp deformation amount of the PCB in the press forming process by simultaneously releasing pressure and reducing temperature in the hot pressing stage in this embodiment is feasible, and the pressure reducing specification in the hot pressing stage can be properly adjusted, so that the warp deformation amount of the PCB after the press is finished, which is cooled to room temperature by opening the mold can be reduced according to the optimization design system and method.
It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While the foregoing description of the embodiments of the present invention has been presented in conjunction with the drawings, it should be understood that it is not intended to limit the scope of the invention, but rather, it is intended to cover all modifications or variations within the scope of the invention as defined by the claims of the present invention.
Claims (9)
1. A circuit board forming pressure optimization method is characterized in that: the method comprises the following steps:
Establishing a simulation model of circuit board press forming, wherein the simulation model comprises a geometric model of the circuit board, a material performance model of the circuit board and a unit cell model of the circuit board, after the simulation model of the circuit board press forming is established, taking the maximum pressure and a depressurization process specification thereof during high temperature and high pressure in the circuit board press forming process as decision variables, so that the warp deformation of the circuit board after press forming, which is cooled to room temperature, is minimum as an optimized objective function, and numerically solving a stress strain field and a displacement field during the circuit board press forming under different maximum pressures and different depressurization process specification conditions through thermal-chemical-mechanical coupling analysis to obtain the optimal pressure and the optimal depressurization process specification during the circuit board press forming process at high temperature and high pressure;
The specific process for establishing the unit cell model of the circuit board is as follows: based on the micro-mechanics theory, a series of copper-resin mixed unit cell models with different copper contents are built for geometric partitions of different copper contents of a wiring layer, and meanwhile, periodic boundary conditions are built for the unit cell models according to the position characteristics of the unit cell models in a macroscopic geometric model of a circuit board, and equivalent material performance parameters of the unit cell models with different copper contents are obtained through calculation.
2. The method for optimizing the molding pressure of the circuit board according to claim 1, wherein the method comprises the following steps: the specific process for establishing the geometric model of the circuit board is as follows: the geometric model of the circuit board is built through a graphical interface of the finite element software, or a data file is generated by utilizing the geometric modeling software, then the data file is imported into the finite element software, the CCL substrate, the prepreg and the wiring layers of the circuit board are built layer by layer according to the lamination sequence, and then geometric partition is carried out on each wiring layer according to the outline size of the circuit board.
3. The method for optimizing the molding pressure of the circuit board according to claim 1, wherein the method comprises the following steps: the specific process for establishing the material performance model of the circuit board is as follows: and geometrically partitioning each wiring layer, defining uniform and equivalent material performance in the partitions to simplify the model, and defining equivalent material performance parameters corresponding to the partitions according to different copper contents in each partition, so that the non-uniformity of the copper content of the wiring layer in-plane and interlayer distribution is macroscopically reflected, and further, the circuit characteristics of the wiring diagram are reflected.
4. The method for optimizing the molding pressure of the circuit board according to claim 1, wherein the method comprises the following steps: the process for numerically solving the stress-strain field and the displacement field in the circuit board press forming process under different maximum pressures and different depressurization process standard conditions through thermal-chemical-mechanical coupling analysis comprises the following steps: based on the geometric model, the material performance model and the unit cell model of the circuit board, establishing initial conditions and boundary conditions of mechanical displacement constraint and load, and initial conditions and boundary conditions of heat transfer science according to actual lamination process conditions; and obtaining material performance parameters of the circuit board, including a plurality of density, specific heat capacity, heat conductivity coefficient, thermal expansion coefficient, chemical shrinkage, modulus and poisson ratio, according to experimental tests, then constructing a simulation model of press molding of the circuit board, and carrying out numerical solution on stress, strain and displacement of the circuit board in the press molding process through finite element software.
5. The method for optimizing the molding pressure of the circuit board according to claim 1, wherein the method comprises the following steps: the calculation process of the buckling deformation amount of the circuit board after press forming and mold opening and cooling to room temperature comprises the following steps: based on the simulation model of the circuit board press-fit molding, the initial conditions and boundary conditions of heat transfer and mechanics required by the simulation, and the required material performance parameters, adopting the composite material mesomechanics, the composite material thermo-elasticity theory, the composite material structural mechanics and the generalized Max Wei Nian elasticity theory to numerically solve the thermal-chemical-mechanical coupling stress strain field and the displacement field of the circuit board in the press-fit molding process, and further obtaining the maximum relative displacement of the surface of the circuit board in the thickness direction after the press-fit is finished and the die opening is finished through data processing and a graphical interaction interface, namely the required warp deformation.
6. The method for optimizing the molding pressure of the circuit board according to claim 5, wherein the method comprises the following steps: in the process of calculating the buckling deformation amount of the circuit board after the die opening is completed in a pressing mode, maintaining the mechanical boundary condition, the thermal conductivity boundary condition and the technological parameters of a cold pressing stage unchanged, obtaining the stress, the strain and the displacement of the circuit board when the die opening is cooled to the room temperature after the die pressing by utilizing a finite element simulation means under different maximum pressures and different depressurization technological specifications, analyzing the influence of the pressure condition in the high-temperature and high-pressure circuit board pressing forming process on the buckling deformation of the circuit board after the die pressing, and optimizing the hot pressing process of the circuit board so as to achieve the aim of optimizing the pressure in the circuit board forming process.
7. A circuit board molding pressure optimizing system is characterized in that: comprising the following steps:
the model construction module is used for building a simulation model of circuit board compression molding, and comprises a circuit board geometric model, a material performance model of the circuit board and a unit cell model of the circuit board;
the parameter setting module is used for setting parameters required by a thermal-chemical-mechanical coupling stress strain field and a displacement place in the process of numerically solving the circuit board press-fit forming, and comprises the steps of establishing initial conditions and boundary conditions of mechanical displacement constraint and load and initial boundary conditions and initial boundary values and boundary conditions of heat transfer science according to actual press-fit process conditions; the material performance parameters of the circuit board, which are obtained according to experimental tests, comprise a plurality of density, specific heat capacity, heat conductivity coefficient, thermal expansion coefficient, chemical shrinkage rate, modulus and poisson ratio;
The optimization solving module is used for taking the maximum pressure and the depressurization process specification of the circuit board during high-temperature and high-pressure forming process as decision variables, so that the minimum warping deformation of the circuit board after press forming after mold opening and cooling to room temperature is an optimization objective function, and respectively carrying out numerical simulation on the circuit board forming process under different maximum pressures and different depressurization process specifications by utilizing a finite element simulation method to obtain the optimal pressure and the optimal depressurization process specification of the circuit board under the current high-temperature and high-pressure conditions;
The specific process for establishing the unit cell model of the circuit board is as follows: based on the micro-mechanics theory, a series of copper-resin mixed unit cell models with different copper contents are built for geometric partitions of different copper contents of a wiring layer, and meanwhile, periodic boundary conditions are built for the unit cell models according to the position characteristics of the unit cell models in a macroscopic geometric model of a circuit board, and equivalent material performance parameters of the unit cell models with different copper contents are obtained through calculation.
8. An electronic device, characterized by: comprising a memory and a processor and computer instructions stored on the memory and running on the processor, which, when executed by the processor, perform the steps in the method of any of claims 1-6.
9. A computer-readable storage medium, characterized by: for storing computer instructions which, when executed by a processor, perform the steps in the method of any of claims 1-6.
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| JP2007110051A (en) * | 2005-09-15 | 2007-04-26 | Denso Corp | Device for adjusting warpage amount of circuit board |
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| JP2007110051A (en) * | 2005-09-15 | 2007-04-26 | Denso Corp | Device for adjusting warpage amount of circuit board |
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