JP2003270060A - Stress strain analyzing system, stress strain analyzing method therefor, and program therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stress strain analyzing system for displaying the results of model formation for analyzing stress strains, of analysis by a finite element method, of a remaining life, and of a stress-strain distribution by a simple operation in a short time. <P>SOLUTION: An analytical model creating means 11 and a material constant creating means 12 urge the selection of the sizes of constituent components and of material data in a base model selected by a processing device 1 and create an analytical model 13. A finite element method analytical means 14 computes the relation between stress and strain through the use of both the analytical model 13 and a general-purpose finite element method program and transmits the relation to both a remaining life predicting means 15 and a graph creating means 16. The remaining life predicting means 15 computes a rupture life to repeated loads from the transmitted relation between stress and strain. The graph creating means 16 graphs both the relation between stress and strain and a remaining life in a form determined by the conditions for drawing graphs selected by the processing device 1 and displays them on the screen of a display device 6. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stress-strain analysis system, a stress-strain analysis method used therefor, and a program therefor, and in particular, solder deformation and generated stress (stress-strain relationship) when an arbitrary load is applied to a structure. With a high degree of accuracy for use in structural strength design,
The present invention relates to a stress-strain analysis system that predicts fracture life for an arbitrary load.

[0002]

2. Description of the Related Art The finite element method is a method of dividing an analysis target into small elements and approximating the solutions piecewise with a function having a finite value for each element to obtain the entire solution. This finite element method is advantageous for a structure having a complicated shape because the analysis target is divided into small elements to solve the partial differential equation.

For this reason, the finite element method is widely used in the field of structural analysis, and is also applied to various stress strain analysis. A suitable example of this type of stress-strain analysis is, for example, the technique disclosed in Japanese Patent No. 2765288.

Conventionally, as a stress-strain analysis system for calculating the stress and strain generated in the solder material by the finite element method with respect to the load and the load due to temperature change, the stress-strain relationship is given as a reference straight line before the stress analysis. The method is generally done.

FIG. 15 shows an example of a reference straight line in this conventional typical stress strain analysis system. In FIG. 15, the stress-strain relationship, which actually becomes a curve in solder, is approximated by two straight lines. In this case, stress up to the yield point −
It is approximated that the strain has a linear relationship, and when the stress reaches the yield stress, the stress is approximated to be constant even if the strain increases. The reference straight line may be a multi-straight line or a reference straight line may be given for each temperature, but most stress strain analysis systems have a limit to the number of reference straight lines.

Elastic strain is a strain that returns to its original shape upon unloading, like a spring, and plastic strain is a strain that remains as a permanent deformation even after unloading. Both are independent of time and temperature and do not change with the deformation rate. Stress analysis that calculates the relationship between these elastic strains and plastic strains and stress is called elasto-plastic analysis.

The viscous strain is a strain that changes with time and temperature, and the deformation progresses after the load. In a material test, it is measured by a creep test in which a change in strain is measured under a constant load, and is also called creep strain. Generally, it is said that viscous strain occurs at a temperature of 0.5 times or more the melting point in absolute temperature notation.

Among the solder materials, lead solder containing lead (Pb) (Sn-Pb solder) is likely to cause this viscous strain. Therefore, the elastic strain may be ignored, and the elastic creep analysis may be performed to calculate the elastic strain and the viscous strain.

As a relationship between viscous strain and stress, the Norton rule of dεc = A · σ ⁿ · dt (1) is generally known. here,
dεc is the increment of viscous strain, σ is the stress generated in the material, d
t is a time step, A and n are material constants.

In addition, the ANAND model is sometimes used for high temperature materials such as rolled materials. Generally speaking, the plastic strain that does not depend on strain rate or temperature is
The AND model treats it as depending on the strain rate and temperature, and does not consider viscous strain.

Therefore, when the ANAND model is used, neither plastic strain nor viscous strain is generated at a temperature not more than 0.5 times the melting point in absolute temperature notation. 0.5 times the melting point in absolute temperature notation means that the solder material is -50.
It is -20 degreeC. A connection reliability test such as a temperature cycle test may be performed even at −65 ° C., which is inconvenient to use the ANAND model for a solder material.

Although there are various theories academically, in general, in the finite element method that handles a three-dimensional large-scale analysis model, convergence calculation is time-consuming and is not practical. It is rarely incorporated in the finite element method and practically used.

As a method for predicting the life of a low cycle cyclic load, the Coffin-Manson life formula of Nf = CΔεin ^-n (2) is generally used as a empirical formula. It is used. Here, Nf is the predicted number of fractures, Δεin is the amplitude of inelastic strain, and C and n are material constants.

This Coffin-Manson life equation is used especially when predicting the fracture life of a semiconductor component joined to a substrate by lead solder. That is, it is assumed that there is a relationship between the inelastic strain, which is the sum of plastic strain and viscous strain generated in the solder material by the finite element method, and the fracture life.

FIG. 16 shows an example of the finite element method analysis in the conventional typical stress strain analysis system. This FIG.
The finite element method analysis in the stress strain analysis system will be described with reference to.

First, an analytical model for obtaining the stress and strain generated by a load, such as an electronic component including a solder material and a circuit board, by numerical calculation is prepared. This work is performed by the user himself / herself based on the shape, size, etc. of the structure to be analyzed (step S31 in FIG. 16). Subsequently, the material constants such as Young's modulus and Poisson's ratio and the reference straight line for calculating the plastic strain are input (step S3 in FIG. 16).
2, S33).

Linear analysis is performed on this analysis model by applying a part of the load such as load and temperature as an initial load (see FIG. 1).
6 steps S34, S35). In the case of microdeformation, Young's modulus is used as a proportional coefficient and strain and stress are proportional to each other.

Next, the calculated stress is compared with the yield stress input as a reference straight line in advance to check whether or not the yield has occurred (step S36 in FIG. 16). If the stress is smaller than the yield stress and no yield occurs, increase the load toward the final load and continue the analysis (Fig. 1
6 steps S38, S39, S41).

On the other hand, if the stress is larger than the yield stress and the yield has occurred, the plastic strain is calculated from the stress-strain approximation line input in advance (step S3 in FIG. 16).
7). And increase the load towards the final load,
Continue analysis (steps S38, S39, S4 in FIG. 16)
1).

Thus, when the load reaches the final load (step S39 in FIG. 16), the stress and strain at that time are obtained (step S40 in FIG. 16). Further, when the analysis results are graphed or the breaking life is predicted, the user himself or herself aggregates the analysis results and prepares a graph and predicts the life by using a separate graph creation tool.

As described above, in the conventional stress-strain analysis system, an analysis method is generally performed in which a yield point at which plastic strain begins to occur is given in advance by the reference line.

In the above description, the expression "increase the load little by little" was used, but in many general-purpose finite element programs, the load is often associated with time. Therefore, it means "advancing time little by little", "increasing a certain time increment" or "every certain time step". In many cases, the user can select the time increment such that it is constant or the maximum and minimum values are specified so that the general-purpose finite element method program automatically determines it from the converged state of the solution.

[0023]

However, since the solder material has an extremely narrow elastic region where stress and strain are linear and the stress-strain relationship is a smooth curve, the conventional finite element method described above is used. The linear approximation by the stress-strain analysis system used has a problem that the error is large.

Further, the conventional stress-strain analysis system has a problem that it is not possible to express a change in yield stress (Baussinger effect) due to a history of loads. Many metal and solder materials exhibit a behavior called the Bauschinger effect that occurs when cyclic strain is applied, as in the case where the reference straight line shown in FIG. The Bauschinger effect is a phenomenon in which the yield stress on the compression side decreases below σy when the final stress σ ′ is reached after passing the yield stress σy on the tensile side and subsequently the compressive side is loaded. The difference between the final stress σ ′ on the tension side and the yield stress on the compression side is approximately equal to 2σy.

However, in the conventional general-purpose finite element method program, a reference straight line that approximates the stress-strain curve is input in advance, and at that time, the stress-strain curve obtained from the tensile test is used, and the load history is Not considered. In many cases, the yield stress on the compression side is treated to be equal to the final stress σ'on the tension side. For this reason, when tensile-compression is repeated, the yield stress gradually increases, and finally the yield does not occur, which is a problem that the actual material behavior is significantly different.

Further, the conventional stress-strain analysis system has a problem that the fracture life cannot be accurately predicted under various load conditions. The Coffin-Manson life equation, which is empirically well established, is for lead solders and metallic materials. For example, empirically for lead-free solders with various compositions and different mechanical characteristics. Has not been fully verified.

The Coffin-Manson rule assumes that inelastic strain (the sum of plastic strain and viscous strain) determines the rupture life, but depending on the material,
As shown in FIG. 18, the stress may be different even with the same inelastic strain amount. In this case, the lifespans of the two are significantly different, but the Coffin-Manson rule determines that the lifespans of the both are the same.

As described above, the Coffin-Manson rule, which has been often used in the past, focuses only on the amount of strain among various mechanical properties of a material, and the prediction accuracy is poor depending on the material. There is.

Furthermore, in the conventional stress-strain analysis system, it is necessary for the user to approximate the stress-strain relationship, which is often a curve, with a straight line, or to determine and input a material constant such as Young's modulus. However, there is a problem that inputting material constants and reference straight lines is troublesome.

In addition to the above, in the conventional stress-strain analysis system, it is general that the user of the system himself / herself inputs numerical values for various load conditions such as load conditions changing with time and temperature. There is also a problem that inputting load conditions is troublesome.

Further, in the conventional stress-strain analysis system, the stress-strain analysis result is uniquely determined by how to handle the measurement result of the material property, which has a variation of at least 10 to 20%. Another problem is that the degree is unclear.

Further, in the conventional stress-strain analysis system, since the user needs to directly operate the general-purpose finite element method program, specialized knowledge is required for analysis of the command unique to the software program to be used. Since there is no support function for model generation, it takes a lot of time and effort to generate an analysis model, and there is no support function for graphing analysis results and predicting fracture life.
There is also a problem that it is necessary to aggregate the analysis results to create a necessary graph and to make a life prediction.

Therefore, an object of the present invention is to solve the above problems, to eliminate the error between the experiment and the analysis, and to provide a stress-strain analysis system capable of improving the prediction accuracy. .

Another object of the present invention is that it is possible to easily generate an analysis model without requiring specialized knowledge such as a command for analysis, to smoothly perform analysis to graph display, and It is to provide a stress-strain analysis system, a stress-strain analysis method used for the system, and a program thereof, which enables even a beginner to easily create a graph and easily check how much remaining life is.

[0035]

A stress-strain analysis system according to the present invention is a stress-strain analysis system for analyzing strain of a material by using a finite element method, wherein the total strain generated in the material by a load is elastic strain, Plastic strain,
Using a constitutive equation expressed as the sum of viscous strains, the curve relationship between stress and strain due to load direction, load speed, and temperature is expressed without inputting a reference line.

Another stress-strain analysis system according to the present invention is a stress-strain analysis system for analyzing the strain of a material by using the finite element method, and the list of models of the finite element method and the list of materials are externally provided. Means for displaying, means for creating a model of the finite element method according to instructions from the outside based on a list of models of the finite element method,
Means for determining the mechanical constitutive equation and its constant according to the contents of instructions from the outside based on the list of the material, and the model of the finite element method and the mechanical constitutive equation and its constant using the material A means for predicting the stress-strain relationship and a means for predicting the fracture life with respect to the load from the stress-strain relationship are provided.

The stress-strain analysis method according to the present invention is a stress-strain analysis method for analyzing the strain of a material by using the finite element method, and displays the model list of the finite element method and the material list externally. A step of creating a model of the finite element method according to instructions from the outside based on the list of models of the finite element method, and a dynamics according to instructions from the outside based on the list of materials Of the dynamic constitutive equation and its constant, the step of predicting the stress-strain relationship of the material using the model of the finite element method and the mechanical constitutive equation, and the fracture life against load from these stress-strain relationship And a step of predicting.

A program for a stress-strain analysis method according to the present invention is a program for a stress-strain analysis method for analyzing a strain of a material by using the finite element method, and the computer is provided with a list of models of the finite element method and the material. From the outside based on the list of the material, the process of creating the model of the finite element method according to the instruction from the outside based on the list of the model of the finite element method, Of processing to determine the mechanical constitutive equation and its constants according to the instruction content, the process of predicting the stress-strain relationship of the material using the model of the finite element method and the mechanical constitutive equation, and these stress- The process of predicting the fracture life with respect to the load from the strain relationship is executed.

That is, the stress-strain analysis system of the present invention uses a constitutive equation in which the total strain caused by a load is represented by the sum of elastic strain, plastic strain, and viscous strain in the analysis system using the finite element method. It is characterized by expressing the curve relationship between stress and strain due to load direction, load speed, and temperature without inputting.

Further, in the stress-strain analysis system of the present invention, an elastic-plastic coefficient or an elastic-plastic matrix for accurately expressing the deformation with respect to the load in consideration of the history by giving a material constant expressing the mechanical characteristics. It is characterized by creating.

In this mechanical constitutive equation, by setting the plastic strain and the viscous strain to 0, it becomes possible to represent the stress-strain relationship of the ceramic material in which only elastic strain occurs, and to set the plastic strain to 0. Thus, it becomes possible to deal with resin materials exhibiting viscoelastic characteristics, and by calculating all strains, it becomes possible to deal with metal materials and solder materials that undergo creep deformation at high temperatures. When only elasto-plastic deformation is caused by a change in temperature, the viscous strain becomes 0, and it becomes possible to handle them uniformly.

In this way, lead solder / lead-free solder, high temperature / low temperature, etc. can be used commonly for all materials and all load conditions. Therefore, it is not necessary to select an appropriate stress-strain analysis system according to the deformation characteristics of the material, and it is possible to obtain the effect that the user is not required to have knowledge or skill. Here, among the materials to be analyzed, Sn-based lead-free solder and the like, which have a large elastic strain, plastic strain, and viscous strain, are particularly high compared to the conventional technique. Accuracy can be obtained.

Further, the stress-strain analysis system of the present invention is characterized in that the back stress is calculated at the same time as the calculation of the stress, and the compound hardening rule including the isotropic hardening rule is incorporated. This compound hardening rule enables the Bausinger effect to be expressed by moving the yield surface (movement hardening rule), and it is possible to expand the yield surface appropriately (isotropic hardening rule). It is possible to accurately express the yield stress when the load direction is changed after different initial yields. Therefore, for example, it is possible to accurately simulate the deformation of various materials under various loads, such as a hysteresis curve when the tension-compression load is repeated.

Furthermore, the stress-strain analysis system of the present invention is characterized by predicting the fracture life with respect to the load by using the energy loss obtained from the stress-strain relationship during cyclic loading. That is, by calculating the loss energy from the area surrounded by the stress-strain curve caused by a certain load condition, by collating the loss energy-breaking life relational expression stored in the material database,
It is characterized by calculating the fracture life for a certain load condition.

In this case, in the stress-strain analysis system of the present invention, the area surrounded by the stress-strain curve obtained from the stress-strain analysis is calculated by element division of the analysis model. The method using this loss energy is to calculate the stress by integrating it with total strain or inelastic strain (the sum of plastic strain and viscous strain). -It is intended to utilize more information from the strain relation for life prediction.
For example, even if the amount of inelastic strain is the same, it is possible to consider that the fracture life is different when the stress is different. Therefore, it is possible to obtain the effect that the prediction accuracy is high for any material.

In addition to the above characteristics, the stress-strain analysis system of the present invention calculates the material constants for new materials that are not in the material database by inputting the stress-strain relationship obtained from the material experiment. , Is characterized by having a function to be added to the database. In this material constant generating means, for example, when stress-strain curves at various temperatures and various strain rates are input in a file or the like, the Young's modulus related to elastic strain and the asymptotic line or asymptote of stress related to plastic strain It becomes possible to automatically calculate the temperature change and strain rate change of the asymptotes related to the way and viscous strain.

Therefore, even for an unknown material, it is possible to accurately simulate the deformation of various materials under various loads by conducting a material experiment only once. It becomes possible to efficiently determine the material constants and the like.

Further, the stress-strain analysis system of the present invention is characterized by having a load condition input function capable of easily inputting a change in load condition with time or a change in temperature. For example, the load, temperature or displacement given as a load can be given by any formula as a function of time or temperature.
The input load (load, temperature, displacement, etc.) is displayed as a graph with the horizontal axis representing time, temperature, etc., and can be operated with a mouse etc. to draw straight lines or curves (exponential curve, logarithmic curve, polynomial curve, Power curve etc.). Even when inputting the repeated load, if you input one cycle and specify the number of times,
All loads are instantly input and displayed on the graph.
Therefore, it is possible to obtain an effect that the input becomes easy even under various and complicated load conditions.

Further, the stress-strain analysis system of the present invention calculates the optimum material constants from the results of material experiments with variations, and predicts the fracture value of a structure under a certain load condition from the obtained life constants. It is characterized by calculating and displaying a more accurate optimum value by statistical processing such as Weibull distribution when calculating. With this statistical processing function, it is possible to process the variation from the simple average according to the user's designation such as normal distribution or Weibull distribution. In particular, the Weibull distribution option has a function of automatically ignoring data when it is determined that the data is in a mode different from other data.

Therefore, it is possible to minimize the error that occurs in the analysis result by handling the measurement result of the material property, which usually has a variation of at least 10 to 20%, and in the case of the Weibull distribution processing. For example, it is possible to highly accurately predict the life by designating the reliability of 99.9% or the like, and narrow the predicted fracture life to a narrow range by designating the reliability of 50% or the like.

Furthermore, the stress-strain analysis system of the present invention is an analysis model for stress-strain analysis of typical structures of some semiconductor components, circuit boards, etc. by using the finite element method. The analysis model file that stores the
The material database that stores the material constants and the dimensions of the analysis model of the structure are rewritten according to the user's input from the input device, and the material constants selected from the material database according to the user's instructions from the input device. Is set as the material constant of the structure of the analytical model to generate an analytical model, having the above analytical method, and about some graphs showing the stress-strain relationship and the fracture life prediction result. , A graph creation condition file storing the creation conditions, and prediction of the analysis result and rupture life of the finite element method analysis means according to the graph creation condition selected from the graph creation condition file according to the user's instruction from the input device And a graph creating means for displaying values on a display device in the form of a graph.

With the analysis model generation support function and the output processing support function such as graphing and life prediction, the user can select with a mouse or the like from the menu stored in the database by accumulating a wealth of experience. . Therefore, it is not necessary for the user to directly operate the general-purpose finite element method program, specialized knowledge regarding the analysis of commands and the like peculiar to the software program used is unnecessary, and it takes a lot of time and effort to generate the analysis model. None,
It is possible to collect the analysis results and create the necessary graphs, and the effect of not having to predict the service life is obtained. It is easy to create a finite element method model for various board mounting, numerical analysis, and service life prediction on a personal computer. It has the effect of being operable.

[0053]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a stress strain analysis system according to an embodiment of the present invention. In FIG. 1, a stress-strain analysis system according to an embodiment of the present invention uses a finite element method, and a processing device 1
A basic analysis model database 2, a material database 3, a graph creation condition database 4, and an input device 5.
The display device 6 and the recording medium 7 are connected to each other.

The processing device 1 includes an analysis model generating means 11,
The material constant generation means 12, the analysis model 13, the finite element method analysis means 14, the life prediction means 15, and the graph creation means 16 are included.

For example, when the processing apparatus 1 is composed of a personal computer, the analysis model generating means 11, the material constant generating means 12, the finite element method analyzing means 14, the life predicting means 15 and the graph creating means 16 are the personal computer. It is realized by software (program) to be executed. This software is stored in the recording medium 7. The analysis model 13 is an analysis model generated by the analysis model generation means 11 and the material constant generation means 12.

The basic analysis model file 2 includes basic models 2-1 to 2-m for the stress strain analysis of some typical structures of structures using the finite element method.
Is stored. Further, in the material database 3, representative material names of structures, various material test results such as stress-strain curves and stress relaxation curves, and Young's modulus, material strength, life, etc. registered in the past are registered. Some material data 3-1 to 3-n including and are stored. Further, the graph creation condition file 4 stores graph creation conditions 4-1 to 4-p indicating graph creation conditions such as how to set the vertical axis-horizontal axis for some frequently used typical graphs. .

FIG. 2 is a flow chart showing an example of the processing operation of the processing apparatus 1 of FIG. 1, FIG. 3 is a diagram showing a hysteresis curve according to an embodiment of the present invention, and FIG. 4 is an embodiment of the present invention. 6 is a diagram showing a loss energy-breaking life relational expression according to FIG. 5, and FIG. 5 is a diagram showing an example of a screen for easily inputting a complicated change with time of temperature which is a load condition according to an embodiment of the present invention. FIG. 6 is a diagram showing a transmitted stress-strain relationship hysteresis curve according to an embodiment of the present invention. The operation of the stress-strain analysis system according to the embodiment of the present invention will be described with reference to FIGS.

When performing stress-strain analysis on a certain structure, the user activates the processing device 1 from the input device 5 such as a keyboard or a mouse. In the activated processing apparatus 1, the analysis model generation means 11, the material constant generation means 12, the finite element method analysis means 14, the life prediction means 15, and the graph creation means 1
The operation is started in the order of 6.

First, the processing device 1 displays on the screen of the display device 6,
Basic models 2-1 to 2-m and graph creation conditions 4-1 to 4-1
Display a list of 4-p and encourage each to select. When the user selects a basic model from the list of basic models 2-1 to 2-m on the screen, the processing device 1 inputs the selected basic model from the basic model file 2 and transmits it to the analysis model generating means 11. To do. When the user selects a graph creation condition from the list of graph creation conditions 4-1 to 4-p on the screen, the processing device 1 inputs the selected graph creation condition from the graph creation condition file 4 and draws the graph. This is transmitted to the creating means 16 (step S1 in FIG. 2).

The analysis model generating means 11 displays the transmitted basic model on the display device 6 and requests the user to rewrite the dimensions of the constituent parts in the basic model. The user corrects the size of the structural part in the basic model displayed on the display device 6 by key input from the input device 5 so as to match the structure to be analyzed (FIG. 2).
Step S2). Further, the analysis model generation means 11 prompts the user to set the constraint condition and sets the inputted constraint condition in the basic model (step S3 in FIG. 2).

The material constant generating means 12 uses the material data 3-1.
A list of 3 to 3-n is displayed on the display device 6 to prompt selection. When the user selects a corresponding material from the list of material data on the screen, the material constant generating means 12 selects from the material database 3 the material constants and mechanical constitutive equations that are judged necessary for this selected material. Input (Fig. 2 Step S
4), set as material constants and mechanical constitutive equations in the selected basic model (step S5 in FIG. 2).

In the material database 3, the stress for each material-
Results of various material tests such as strain curves and stress relaxation curves,
Mechanical constitutive equations suitable for expressing the stress-strain relationship and material constants used in the past are registered. When the material constant generating means 12 determines that the material constants necessary for the mechanical constitutive equation used by the selected material are not registered in the material database 3, various material tests registered in the material database 3 are performed. The necessary material constants are calculated based on the result of (1), set as the material constants in the selected basic model, and newly registered in the material database 3.
Further, the material constant generating means 12 transmits the material strength and life data included in the selected material data to the graph creating means 16.

In this way, the generation of the analysis model 13 is completed by the analysis model generation means 11 and the material constant generation means 12 (step S6 in FIG. 2), and this analysis model 13 is transmitted to the finite element method analysis means 14.

The finite element method analysis means 14 uses the analysis model 13 to perform stress strain analysis as follows in the case of a lead-free solder having a composition of Sn-3.0Ag-0.5Cu, for example. First, the user inputs final load conditions such as temperature and load through the input device 5 (step S7 in FIG. 2).

In the present embodiment, the strain (total strain) caused by the load condition is calculated by the sum of elastic strain, plastic strain and viscous strain, and in the increment form, dεt = dεe + dεp + dεc (3) dεt = dσ / E + Bσ ^m It can be represented by the equation dσ + Aσ ⁿ dt (4). Where dε
t is the total strain increment, dεe is the elastic strain increment, dε
p is the increment of plastic strain, dεc is the increment of viscous strain, σ
Is the stress generated in the material, dσ is the stress increment, E is the Young's modulus, dt is the time step, and A, B, m, and n are the material constants of the lead-free solder.

The finite element method analysis means 14 first uses the Norton's law to calculate the increment of viscous strain, that is, (1) above.
Calculation is performed using an expression (step S8 in FIG. 2). in this case,
In the equation (1), dεc is an increment of viscous strain, σ is a stress generated in the material, dt is a time step, and A and n are material constants of the lead-free solder.

Next, the finite element method analysis means 14 calculates the elastoplastic coefficient or the elastoplastic matrix (1 / E + Bσ ^m ) (step S9 in FIG. 2). Where σ is the current stress, E
Is the Young's modulus, B and m are material constants, and this elasto-plastic coefficient changes with stress.

[0068] Finite element analysis unit 14, dσ = (dεt-dεc) / (1 / E + Bσ m) ...... stress and incremental Dishiguma of the the expression (5) σ = σ + dσ ...... (6), a new stress Find σ. In this embodiment, the back stress that changes depending on the direction of the load is calculated in the same manner as the stress (FIG. 2, step S1).
0).

Subsequently, the finite element method analysis means 14 calculates a new elastic strain εe from the equation εe = εe + dσ / E (7) (step S11 in FIG. 2), and εp = εp + Bσ ^m dσ. 8) A new plastic strain εp is calculated from the equation (8) (step S12 in FIG. 2).

Further, the finite element method analysis means 14 calculates the increment dεc of viscous strain and a new viscous strain εc from the equation: dεc = Aσ ⁿ dt (9) εc = εc + dεc (10) 2 step S13). When the final load is not reached (step S14 in FIG. 2), the finite element method analysis means 14 increases the load (or at the next time step) and calculates the next elastic-plastic coefficient or elastic-plastic matrix (FIG. 2). 2 steps S8 to S15).

In this way, in this embodiment, the increment is calculated using the current value, and a new value is obtained as the cumulative value. By repeating the above process, the stress and the strain can be calculated without giving the yield stress and the reference straight line, and the stress-strain relationship becomes a curve. The finite element method analysis unit 14 transmits the stress-strain relationship at each step to the life prediction unit 15 and the graph creation unit 16 (step S16 in FIG. 2).

The life predicting means 15 determines the transmitted stress-
From the strain relationship, the fracture life for cyclic loading is calculated. First, an appropriate one cycle is extracted from the stress-strain relationship, and a hysteresis curve is drawn from the stress-strain graph (see FIG. 3). The life prediction unit 15 obtains the loss energy for one cycle by integrating the stress with strain and calculating the area thereof (step S17 in FIG. 2).

The life predicting means 15 compares this loss energy with the loss energy-breaking life relational expression (see FIG. 4) input as life data from the material database 3 (step S18 in FIG. 2) to find a margin for the load. The life is calculated (step S19 in FIG. 2). Life Prediction Means 1
5 transmits the prediction result of this remaining life to the graph creating means 16.

The graph creating means 16 creates a graph of the transmitted stress-strain relationship and residual life in each step in a format determined by the transmitted graph creating conditions, and displays the data on the display device 6.
Displayed on the screen. Further, the data of the material strength and the repeated life curve of the material transmitted from the analysis model generation means 11 are also displayed on the screen of the display device 6 (step S in FIG. 2).
20).

In the present embodiment, the load conditions input through the input device 5 are the load, stress, and
It may be given by strain or temperature distribution. Normal,
With this as the final load, the load condition is set for each step by dividing into an arbitrary number.

Further, in the present embodiment, it is also possible to use a function capable of easily inputting a change in load condition due to time or temperature. FIG. 5 shows an example of a screen for easily inputting a complicated change in temperature, which is the load condition, with time. By inputting the combination of time and temperature at that time, or the combination of time increment and temperature in sequence, a temperature-time graph is displayed on the screen. be able to.

Further, by inputting one cycle, it is possible to complete the input at once by designating the range and the number of repetitions. In this way, it is possible to avoid repeatedly inputting the same load condition many times. Furthermore, it is possible to store frequently used load conditions and previous conditions and call them each time the default button is pressed.

The above-mentioned input device 5 and display device 6, the processing device 1, the basic analysis model database 2, the material database 3, and the graph creation database 4 operate on different computers and are connected by a network or the internet. May be. Usually, the processing device 1 is operated on a large-sized computer or a host computer having the highest processing speed, and the input device 5 and the display device 6 can be simultaneously used by a plurality of users.

Here, the program displayed on the input device 5 and the display device 6 for inputting and outputting may be realized by the program of the stress strain analysis system according to the present embodiment, and in many cases, it is attached to a personal computer. General-purpose software such as existing spreadsheet software may be used by adding functions as macros or additional applications.

Alternatively, a Web browser may be used to access the address of another computer in which the stress-strain analysis system according to this embodiment is installed for input and display. Further, this system prepares a program that can be read by the Web function for operating the stress-strain analysis system according to the present embodiment, installs it on the user's computer, and the user uses the Web browser to execute the program. You may access and use.

Further, in the present embodiment, the mechanical constitutive equation of the solder is described in the user subroutine etc. separately from the material constant generating means 12 so that it operates in conjunction with the program of the finite element method analyzing means 14. You may compile and use it. In this case, the mechanical constitutive equation according to the present embodiment can be described in a user subroutine format and incorporated into various general-purpose finite element method programs for use. As a general-purpose finite element method program, for example, MSC. So
Mar from ftware Corporation
c, ANSYS Inc. ANSYS®, Hibbitt, Karlsson & Soren
sen, Inc. ABAQUS or NASTR
There are AN and others.

Furthermore, the life predicting means 15 obtains the energy loss from the transmitted stress-strain relationship. At this time, the transmitted stress-strain relationship hysteresis curve is divided into elements by the function of the finite element method program. Then
You may calculate the area. An example of this is shown in FIG. The life predicting means 15 calculates the remaining life with respect to the load by collating the result with the loss energy-breaking life relational expression input as life data from the material database 3.

Generally, stress-strain analysis is roughly divided into three parts: generation of an analysis model, finite element method analysis, and result display.
It is divided into stages. Among these, according to the present embodiment, the generation of the analysis model has the file in which the basic model and the material constants are registered. Therefore, the basic model is selected, the dimensions of the component parts are rewritten, and the material is specified. However, the analysis model can be easily generated by giving the constraint condition. Particularly, the material can be specified only by specifying any of the material data 3-1 to 3-n stored in the material database 3.

Therefore, in this embodiment, the working time required for generating the analysis model can be greatly shortened as compared with the conventional case. Further, since the stress-strain analysis using the analysis model and the general-purpose finite element method program is automatically advanced by the finite element method analysis means 14, even a user who lacks specialized knowledge such as commands specific to the general-purpose finite element method program Stress-strain analysis can be performed. Therefore, this embodiment does not require specialized knowledge such as an analysis command as in the conventional case.

Further, in the present embodiment, the user can also select a desired graph creation condition from the graph creation condition database 4 for the graph that outputs the analysis result, such as stress, strain, deformation, and remaining life. Collects the analysis results and automatically outputs the graph of the analysis result from the display device 6 without creating the necessary graph by itself, so that it is possible to smoothly perform the analysis to the graph display, and the graph can be displayed even by a beginner. Can be created easily.

Furthermore, in this embodiment, since the stress and strain of the analysis result by the finite element method are displayed together with the value of the material strength of the component parts and the repeated life curve obtained from the experiment, It is possible to easily confirm whether the stress caused by the load condition does not exceed the strength of the material and the remaining life.

FIG. 7 is a diagram showing an example of the display screen of the basic model according to the embodiment of the present invention, and FIGS. 8 and 9 are diagrams showing an example of the dimension input screen according to the embodiment of the present invention. FIG. 10 is a diagram showing an example of a material constant input screen according to an embodiment of the present invention, and FIG. 11 is a diagram showing an example of a temperature input screen as a load condition according to an embodiment of the present invention.

FIG. 12 is a view showing an example of a stress-strain relation display screen of the analysis results according to the embodiment of the present invention, and FIG. 13 shows the life curve of the material according to the embodiment of the present invention. It is a figure which shows an example of the display screen shown by the relationship between loss energy and remaining life, and FIG. 14 is a figure which shows an example of the input screen of the relational expression of loss energy and remaining life of the material by one Example of this invention. is there.

Each input screen and display screen in the stress-strain analysis system using the finite element method according to an embodiment of the present invention will be specifically described with reference to FIGS. 7 to 14.

FIG. 7 shows an example of a screen displaying the basic model displayed on the screen of the personal computer. Figure 7
In the, each hierarchy is displayed in an easy-to-understand classification, and the user selects the applicable basic model from the list of basic models using a mouse or keyboard.

Below the screen shown in FIG. 7, the contents of the next screen are displayed. When this is pressed, the screen is jumped to and displayed. When displaying the contents of the next screen, the screen that has already been processed is skipped. In this way, even a beginner can perform the same analysis work as an expert by inputting according to the instruction.

On the left side of the screen, the flow of a series of analysis work items as a whole is displayed. The items on the current screen are displayed so as to be distinguishable from other items, and the processed items are also displayed as other items. It is displayed in a distinguishable manner, and you can immediately understand the overall flow, and if you select an item with a mouse or keyboard,
It jumps to the screen and is displayed.

8 and 9 show examples of screens for inputting dimensions.
Shown in. Figure 8 shows the screen for entering the dimensions of the overall shape,
FIG. 9 shows a screen for inputting the dimensions of the detailed portion. By selecting the bookmark part above these screens, the screens are switched and displayed from the input screen of the dimensions of the entire shape to the input screen of the dimensions of the detailed parts.

Each time the default button on the screen is pressed, the load condition and the previous condition stored in the system, which are frequently used, can be called. The user can input a predetermined size by only partially modifying it.

FIG. 10 shows an example of a screen for inputting material constants. In this drawing, the mechanical constitutive equations to be used are selected in conjunction with the selection of the material, and when the analysis is executed, the analytical method that improves the accuracy of the mechanical constitutive equations is automatically selected. Even if the materials have the same name, they can be selected and specified using a mouse or keyboard. In this way, the creation of the analytical model is completed.

FIG. 11 shows an example of a screen for inputting the temperature as the load condition. By sequentially inputting a time and a temperature at that time, or a time increment and a temperature on this screen, a temperature-time graph is updated on the screen. Further, by selecting the start and end of one cycle on the graph and designating the number of repetitions, it is possible to easily input the repetition load at one time.

In this way, even under troublesome repeated load conditions, it is possible to easily input the data without making an error while visually checking. Although the load condition of the temperature change with time is taken as an example, the same applies to the case where the load changes with time and temperature. In addition, remember frequently used load conditions and previous conditions,
You can also call them every time you press the default button.

When the analysis execution button is selected, data is sent to the large computer, and when the analysis is completed after a while, a message to that effect is displayed on the user's personal computer screen.

FIG. 12 shows an example of a screen displaying the stress-strain relationship among the analysis results, and FIG. 1 shows an example of the screen displaying the life curve of the material in terms of the loss energy and the remaining life.
3 shows. In the present embodiment, the predicted fracture frequency is displayed above the analysis result display menu shown in FIG. 12 for the user who wants to know the remaining life as soon as possible. In FIG. 12, the energy loss is calculated immediately from the displayed hysteresis curve, and the predicted number of fractures is displayed from the relationship between the material energy loss and the remaining life displayed in FIG. 13.

FIG. 14 shows an example of a screen for inputting the relational expression between the energy loss of the material and the remaining life. On this screen, data is automatically entered from the material database when selecting a material, but you can check or correct the value. The life prediction result when the above relational expression is corrected is immediately displayed on the screen shown in FIG.

In this way, the stress-strain analysis system according to this embodiment predicts and guides the operation that the user will perform. As a result, the user can easily predict the life of the material, which has been difficult in the past, by operating the stress-strain analysis system according to the present embodiment as instructed.

In this embodiment, an example of the finite element method two-dimensional analysis model is shown, but for the three-dimensional model, from the input screen to the life prediction, the same processes and screens as described above are performed. You can

The present invention is not limited to the above-mentioned embodiment of the present invention, and various other additions and modifications can be made. For example, the present invention provides various general-purpose finite element method programs (Marc, ANSYS, ABAQ) having a finite element method analysis function.
Can be used in combination with US or NASTRAN). In addition, the present invention, contact analysis and heat conduction, vibration,
As a pre- and post-processor for general-purpose finite element method programs such as fluid analysis, it is also effective when making model creation more efficient and creating complex graphs.

As described above, in the present invention, the optimum mechanical constitutive equation is selected only by selecting the material, and the finite element method analysis suitable for it is performed, so that even a beginner can easily operate. For example, linear analysis is performed for ceramic materials, elastic-plastic analysis is performed for metals, elastic creep analysis is performed for resins and lead solders, and viscoplastic analysis is performed for lead-free solders.

Further, in the present invention, since the composite hardening law is incorporated by calculating the back stress when calculating the plastic strain and the viscous strain, various loads such as stress-strain of repeated load and Bausinger effect are calculated. It is possible to accurately simulate complex deformations of various materials with respect to.

Further, according to the present invention, the remaining life for an arbitrary load can be easily predicted with high accuracy even by a beginner.
The life can be predicted by specifying the reliability. that time,
Even when the first material is selected, the necessary material constants are automatically calculated from the experimental results of that material and added to the material database, which makes it easy to use each time.

As described above, in the present invention, it is possible to easily input changes in various load conditions due to time and temperature.

On the other hand, in the present invention, since the more accurate optimum value can be calculated by the statistical processing of the Weibull distribution etc., the function of automatically removing the data of different modes can be used to measure the material properties. The error of the analysis result caused by the variation can be suppressed to the minimum.

In the present invention, as described above, the user does not need to directly operate the general-purpose finite element method program, specialized knowledge regarding analysis of commands and the like peculiar to the software program to be used is not required, and analysis model generation is performed. It does not require a lot of time and labor, and it does not require the trouble of totaling the analysis results to create the necessary graphs and predicting the service life.

In the present invention, it is possible to easily operate from the creation of the finite element method model of various board mounting, the numerical analysis and the life prediction on the personal computer.

In the present invention, the selection means 11 and the analysis model generation means 12 which are support functions for generation of the analysis model.
In addition, since the finite element method analysis means 15 for automatically advancing a series of processes for performing a finite element method analysis by applying a final load is provided, the user is lacking in specialized knowledge. However, stress-strain analysis can be performed easily. Therefore, it is not necessary to train a design engineer who is skilled in a general-purpose finite element method program, and the human cost can be reduced.

Further, according to the present invention, since the graph creating means 17 which is a support function for graphing is provided, the analysis result can be graphed easily.

As described above, in the present invention, in the analysis system using the finite element method, by using the constitutive equation in which the total strain caused by the load is represented by the sum of elastic strain, plastic strain, and viscous strain, It is possible to express a curve relationship between stress and strain due to load direction, load speed, and temperature without inputting.

Further, in the present invention, an elastic-plastic coefficient or an elastic-plastic matrix for accurately expressing the deformation with respect to the load in consideration of the history is created by giving a material constant expressing the mechanical characteristic. In this mechanical constitutive equation, by setting the plastic strain and the viscous strain to 0,
It is possible to express the stress-strain relationship of the ceramic material in which only elastic strain occurs, and by setting the plastic strain to 0,
It can be applied to a resin material exhibiting viscoelastic characteristics, and by calculating all strains, it can be applied to a metal material or a solder material that undergoes creep deformation at high temperatures. When only elasto-plastic deformation is caused by a change in temperature, the viscous strain becomes 0, and it can be treated in a unified manner.

In this way, lead solder / lead-free solder, high temperature / low temperature, etc. can be used in common for all materials and all load conditions. Therefore, it is not necessary to select an appropriate stress-strain analysis system according to the deformation characteristics of the material, and it is possible to obtain the effect that the user is not required to have knowledge or skill. Here, among the materials to be analyzed, Sn-based lead-free solder and the like, which have a large elastic strain, plastic strain, and viscous strain, are particularly high compared to the conventional technique. Accuracy can be obtained.

Further, in the present invention, the back stress is calculated at the same time when the stress is calculated, and the compound hardening rule including the isotropic hardening rule is incorporated. This compound hardening law can express the Bauschinger effect by moving the yield surface (movement hardening rule), and it also depends on the material by expanding the yield surface appropriately (isotropic hardening rule). It is possible to accurately express the yield stress when the load direction is changed after yielding. Therefore, for example, it is possible to accurately simulate the deformation of various materials under various loads such as a hysteresis curve when the tension-compression load is repeated.

Furthermore, in the present invention, the fracture life with respect to the load is predicted by using the loss energy obtained from the stress-strain relationship during cyclic loading. That is, the loss energy is calculated from the area surrounded by the stress-strain curve generated under a certain load condition, and the loss life for a certain load condition is calculated by collating the loss energy-fracture life relational expression stored in the material database. It is calculated.

In this case, in the present invention, the area surrounded by the stress-strain curve obtained from the stress-strain analysis is calculated by element division of the analysis model. The method using this loss energy is to calculate the stress by integrating it with total strain or inelastic strain (the sum of plastic strain and viscous strain). -It is intended to utilize more information from the strain relation for life prediction. For example, it is possible to consider that the fracture lives differ when the stresses are different even with the same inelastic strain amount. Therefore, it is possible to obtain the effect that the prediction accuracy is high for any material.

In addition to the above, in the present invention, by inputting the stress-strain relationship obtained from the material experiment, the material constant is calculated even for a new material that is not in the material database, and the function of adding to the database is provided. have. In this material constant generating means, for example, when stress-strain curves at various temperatures and various strain rates are input in a file or the like, the Young's modulus related to elastic strain and the asymptotic line or asymptote of stress related to plastic strain It is possible to automatically calculate a change in temperature, a change in strain rate, etc. of the asymptote associated with the method and viscous strain.

Therefore, even if an unknown material is subjected to a material experiment only once, it is possible to accurately simulate the deformation of various materials under various loads. It is possible to efficiently determine the constant and the like.

Further, the present invention has a load condition input function capable of easily inputting a change in load condition with time or a change with temperature. For example, the load applied as a load, temperature, or displacement is given by an arbitrary formula as a function of time or temperature, and the input load (load, temperature, displacement, etc.) is a graph with time or temperature as the horizontal axis. Is displayed, and can be operated with a mouse etc. to draw straight lines and curves (exponential curve, logarithmic curve,
Polynomial curve, power curve, etc.). Even when the repeated load is input, if one cycle is input and the number of times is specified, all the loads are instantaneously input and displayed on the graph. Therefore, it is possible to obtain an effect that the input becomes easy even under various and complicated load conditions.

Furthermore, according to the present invention, when calculating the optimum material constant from the material experiment results with variations and when calculating the fracture prediction value of the structure under a certain load condition from the obtained life constant, By statistical processing such as Weibull distribution, a more accurate optimum value is calculated and displayed. With this statistical processing function, it is possible to process the variation according to the user's designation such as a normal distribution or a Weibull distribution from a simple average. Especially for the Weibull distribution option,
When it is determined that the data is in a mode different from other modes, it also has a function of automatically ignoring the data and calculating.

Therefore, it is possible to minimize the error that occurs in the analysis result by handling the measurement result of the material property, which usually has a variation of at least about 10 to 20%. In this case, for example, it is possible to specify the reliability of 99.9% or the like to predict the life with high accuracy, or to specify the reliability of 50% or the like to narrow the predicted fracture life to a narrow range.

Furthermore, in the present invention, regarding the constitution of some typical structures such as semiconductor parts and circuit boards,
An analysis model file that stores an analysis model for stress-strain analysis using the finite element method, a material database that stores the material constants of some typical materials of the structure, and an input device The size of the analysis model of the structure is rewritten according to the user's input, and the material constant selected from the material database according to the user's instruction from the input device is set as the material constant of the structure of the analysis model and analyzed. A graph creation condition file that stores creation conditions for an analysis model generation unit that generates a model, the above-described analysis method, and some graphs indicating the stress-strain relationship and the fracture life prediction result, and input. A finite element according to the graph creation condition selected from the graph creation condition file according to the user's instruction from the device And a graph creation unit for displaying on the display device to chart the predicted values of the analysis results and rupture life analysis unit.

With the analysis model generation support function and the output processing support function such as graphing and life prediction, the user can select from a database menu by accumulating a wealth of experience with a mouse or the like. Therefore, it is not necessary for the user to directly operate the general-purpose finite element method program, specialized knowledge regarding the analysis of commands and the like peculiar to the software program used is unnecessary, and it takes a lot of time and effort to generate the analysis model. The advantage is that it does not require the trouble of totaling the analysis results to create the necessary graphs and predicting the service life, and the finite element method model creation of various board mountings, numerical analysis, and service life prediction can be performed on a personal computer. The effect is that it can be easily operated.

The present invention may further have the following aspects in connection with the description of the claims.

(1) A stress-strain analysis system for analyzing strain of a material by using the finite element method, wherein a means for displaying a list of models of the finite element method and a list of the materials to the outside, and the finite element Means for creating a model of the finite element method according to the instruction contents from the outside based on the list of the model of the method, and a mechanical constitutive equation and its constant according to the instruction contents from the outside based on the list of the materials Means, a means for predicting the stress-strain relationship of the material using the model of the finite element method, the mechanical constitutive equation and its constant, and predicting the fracture life against load from these stress-strain relationship. And a means for controlling the stress-strain analysis system, wherein the material is a viscous material containing at least a resin and a metal at a high temperature.

(2) A stress-strain analysis system for analyzing strain of a material by using the finite element method, which is a means for displaying a list of models of the finite element method and a list of materials to the outside, and the finite element. Means for creating a model of the finite element method according to the instruction contents from the outside based on the list of the model of the method, and a mechanical constitutive equation and its constant according to the instruction contents from the outside based on the list of the materials Means, a means for predicting the stress-strain relationship of the material using the model of the finite element method, the mechanical constitutive equation and its constant, and predicting the fracture life against load from these stress-strain relationship. And a means for doing so, wherein the material is an industrially-used solder material containing at least Sn-based solder.

(3) The Sn-based solder is at least S
The lead-free solder material containing no n-Ag system, Sn-Zn system, and Sn-Bi system that does not contain lead, and the stress-strain analysis system according to (2).

(4) A graph creating condition file storing the creating conditions of some graphs showing the stress-strain relationship and the predicted result of the fracture life, and selected from the graph creating condition file according to an instruction from the outside. The stress according to any one of (1) to (3), further comprising: a graph creating means for displaying the analysis result of the finite element method and the predicted value of the fracture life based on the graph creating condition. Strain analysis system.

(5) A stress-strain analysis system for analyzing the strain of a material by using the finite element method, which is a means for displaying a list of models of the finite element method and the list of materials to the outside, and the finite element. Means for creating a model of the finite element method according to the instruction contents from the outside based on the list of the model of the method, and a mechanical constitutive equation and its constant according to the instruction contents from the outside based on the list of the materials Means, a means for predicting the stress-strain relationship of the material using the model of the finite element method, the mechanical constitutive equation and its constant, and predicting the fracture life against load from these stress-strain relationship. Means, a graph creation condition file storing the creation conditions of some graphs showing the stress-strain relationship and the prediction result of the fracture life, and according to an instruction from the outside. Stress-strain analysis system and having a graphing means for displaying graphs the predicted values of the analysis results and rupture life of the finite element method based on the selected graph creation condition from serial charting condition file.

(6) As the means for determining the mechanical constitutive equation, the mechanical constitutive equation of the material is used in consideration of the difference of the deformation of the material due to the load history, temperature dependency and strain rate dependency. The stress strain analysis system according to any one of (1) to (5), characterized in that

(7) The means for predicting the stress-strain relationship of the material uses a constitutive equation in which the strain generated by the load is represented by the sum of elastic strain, plastic strain and viscous strain, and the direction of the load is The stress-strain analysis system according to any one of (1) to (6), characterized in that a change in yield point when changed is simulated, and a stress-strain relationship during cyclic loading of the material is simulated.

(8) The means for predicting the rupture life is characterized by predicting the rupture life with respect to the cyclic load by using the energy loss obtained from the stress-strain relationship during cyclic load. ) Any one of the stress-strain analysis system described above.

(9) A material database for storing a list of the materials, a means for generating the material constants based on the stored contents of the material database, a means for inputting the load and restraint conditions of the structure, and (1) from (1) including means for calculating at least deformation, elasticity / plasticity / viscous strain, and stress of a structure under load, and means for displaying the fracture life of the structure under the arbitrary load. The stress strain analysis system according to any one of 8).

(10) A material constant not yet registered in the material database is calculated based on the stress-strain curve obtained from the material experiment, and the calculation result is additionally registered in the material database (9). ) The stress strain analysis system described.

(11) A constant representing the material life of a new material not registered in the material database was calculated based on the relationship between the life and any of stress and strain obtained from the material experiment under cyclic loading, and the calculation result was obtained. Is additionally registered in the material database. The stress-strain analysis system according to (9) or (10) above.

(12) The means for predicting the breaking life is
Loss energy is calculated from the area surrounded by the stress-strain curve under an arbitrary load condition, and the breaking life for the arbitrary load condition is calculated by collating the loss energy-breaking life relational expression stored in the material database. The stress-strain analysis system according to any one of (9) to (11).

(13) The means for predicting the breaking life is
The area surrounded by the stress-strain curve obtained from the stress-strain analysis is calculated by element division of the analysis model of the finite element method (12).

(14) Lead-free solder of a semiconductor component and a circuit board joined by lead-free solder, stress, strain, and deformation generated in each of the component and the substrate are analyzed using the finite element method, and a typical number For the structure of a structure, an analysis model file that stores an analysis model when stress-strain analysis is performed using the finite element method, and the constants of some typical materials of the structure are stored. In addition to rewriting the dimensions of the analysis model of the structure according to the input from the outside, the material constant selected from the material database according to the instruction from the outside is used as the material constant of the structure of the analysis model. It is characterized by setting and setting the required material constants in the database to generate the material constants to generate an analysis model (2 Stress-strain analysis system according to any of (13).

(15) The stress-strain analysis system according to any one of (1) to (14), characterized in that at least changes in load conditions due to time and temperature can be input.

(16) When generating the constant of the material,
Even if the results of material experiments have variations, optimal constants are generated by statistical processing that includes at least the Weibull distribution, and the predicted fracture value of the structure under any load condition is calculated from the constants that represent the life obtained by the statistical processing. The stress-strain analysis system according to any one of (1) to (15), which is calculated and displayed.

[0143]

As described above, the stress-strain analysis system of the present invention is a stress-strain analysis system that analyzes the strain of a material using the finite element method. By using the constitutive equation expressed as the sum of viscous strains and expressing the curve relationship between stress and strain due to load direction, load speed, and temperature without inputting a reference straight line, the error between experiment and analysis It is possible to eliminate the problem, and it is possible to improve the prediction accuracy. As a result, in the present invention, it is possible to know the deformation and fracture life of a structure, which has conventionally required an experiment under various conditions, by a simulation, and it is possible to obtain the effect that the condition and the number of the experiment can be reduced.

Further, another stress-strain analysis system of the present invention is a stress-strain analysis system using the finite element method for predicting the reliability of solder connection. The list is displayed externally, and the finite element method model is created according to the instruction contents from the outside based on the finite element method model list. According to the instruction contents from the outside based on the solder material list, By determining the mechanical constitutive equation and its constant, predicting the stress-strain relationship of the solder using the model and the mechanical constitutive equation of the finite element method, by predicting the fracture life to load from these stress-strain relationship, An analysis model can be easily generated without requiring specialized knowledge such as analysis commands, and it is possible to perform smoothly from analysis to graph display. It is possible to create graphs easily in person, remaining life is effect that how much it is possible to easily confirm.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a stress strain analysis system according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an example of processing operation of the processing apparatus of FIG.

FIG. 3 is a diagram showing a hysteresis curve according to an embodiment of the present invention.

FIG. 4 is a diagram showing a loss energy-breaking life relational expression according to an embodiment of the present invention.

FIG. 5 is a diagram showing an example of a screen for easily inputting a complicated change with time of temperature which is a load condition according to an embodiment of the present invention.

FIG. 6 shows a transmitted stress-strain relationship hysteresis curve according to an embodiment of the present invention.

FIG. 7 is a diagram showing an example of a display screen of a basic model according to an embodiment of the present invention.

FIG. 8 is a diagram showing an example of a dimension input screen according to an embodiment of the present invention.

FIG. 9 is a diagram showing an example of a dimension input screen according to an embodiment of the present invention.

FIG. 10 is a diagram showing an example of a material constant input screen according to an embodiment of the present invention.

FIG. 11 is a diagram showing an example of an input screen for temperature as a load condition according to an embodiment of the present invention.

FIG. 12 is a diagram showing an example of a stress-strain relationship display screen of the analysis results according to the embodiment of the present invention.

FIG. 13 is a diagram showing an example of a display screen showing a life curve of a material according to an embodiment of the present invention in a relationship between loss energy and remaining life.

FIG. 14 is a diagram showing an example of an input screen for a relational expression of energy loss and remaining life of a material according to an embodiment of the present invention.

FIG. 15 is an explanatory diagram of a conventional stress strain analysis system.

FIG. 16 is a flowchart showing the procedure of a conventional stress strain analysis method.

FIG. 17 is a diagram showing a problem of the conventional stress strain analysis system.

FIG. 18 is a diagram showing a problem of the conventional stress strain analysis system.

[Explanation of symbols] 1 processor 2 Basic analysis model database 3 Material database 4 Graph creation condition database 5 Input device 6 Display device 7 recording media 11 Analysis model generation means 12 Material constant generation means 13 Analysis model 14 Finite element method analysis means 15 Life Prediction Means 16 Graph creation means

Claims (16)

[Claims] 1. A stress-strain analysis system for analyzing strain of a material by using a finite element method, wherein a constitutive equation representing a total strain generated in the material by a load as a sum of elastic strain, plastic strain, and viscous strain. A stress-strain analysis system characterized by expressing a curved relationship between stress and strain due to load direction, load speed, and temperature without using a reference straight line. 2. A material constant expressing a mechanical property is given,
The stress-strain analysis system according to claim 1, wherein one of an elasto-plastic coefficient and an elasto-plastic matrix for accurately expressing the deformation with respect to the load based on the load history is created. 3. A stress-strain analysis system for analyzing strain of a material by using the finite element method, wherein a means for displaying a list of models of the finite element method and a list of the materials to the outside, and the finite element method. Means for creating a model of the finite element method according to the instruction content from the outside based on the list of models, and a mechanical constitutive equation and its constant according to the instruction content from the outside based on the material list. Means for determining, means for predicting the stress-strain relationship of the material using the model of the finite element method, the mechanical constitutive equation and its constants, and predicting the fracture life against load from these stress-strain relationships And a stress-strain analysis system. 4. The means for determining the mechanical constitutive equation uses the mechanical constitutive equation of the material in consideration of the difference in deformation history of the material due to load history, temperature dependency and strain rate dependency. The stress strain analysis system according to claim 3. 5. The means for predicting the stress-strain relationship of the material, wherein the strain generated by the load is elastic strain,
Using the constitutive equation represented by the sum of plastic strain and viscous strain,
4. A stress-strain relationship during cyclic loading of the material is simulated by simulating a change in yield point when the direction of the loading is changed.
Alternatively, the stress strain analysis system according to claim 4. 6. The means for predicting the stress-strain relationship of the material creates one of an elasto-plastic coefficient and an elasto-plastic matrix for accurately expressing the deformation with respect to the load based on the load history, and The stress-strain according to any one of claims 3 to 5, wherein an increment of stress is calculated using either an elasto-plastic coefficient or an elasto-plastic matrix, and the plastic strain is obtained using the calculation result. Analysis system. 7. The rupture life predicting means predicts the rupture life with respect to the cyclic load by using a loss energy obtained from a stress-strain relationship during cyclic load. The stress-strain analysis system according to any one of 1. 8. The stress-strain analysis system according to claim 3, wherein the material is a lead-free solder material. 9. A material database for storing a list of the materials, a means for generating a constant of the material based on the stored contents of the material database, a means for inputting a load and a constraint condition of a structure, A stress-strain curve obtained from a material experiment including means for calculating at least deformation, elasticity / plasticity / viscous strain, and stress of a structure under load, and means for displaying the fracture life of the structure under the arbitrary load. The stress-strain analysis system according to any one of claims 3 to 8, wherein a material constant that has not been registered in the material database is calculated based on the above, and the calculation result is additionally registered in the material database. 10. A constant representing the material life of a new material not registered in the material database is calculated based on the relationship between the life and any of stress and strain obtained from material experiments under cyclic loading, and the calculated result is calculated. The stress-strain analysis system according to claim 9, which is additionally registered in the material database. 11. The means for predicting the breaking life calculates loss energy from an area surrounded by a stress-strain curve under an arbitrary load condition, and calculates a loss energy-breaking life relational expression stored in the material database. The stress-strain analysis system according to claim 9 or 10, wherein the fracture life for the arbitrary load condition is calculated by collation. 12. The finite element method is used to analyze the stress, strain, and deformation generated in each of the material and the structure containing the material, and the finite element is analyzed for a typical structure of some structures. Input from the outside, including an analysis model file that stores an analysis model for stress-strain analysis using the element method, and a material database that stores the constants of the materials for some typical materials of the structure According to the instruction from the outside, the material constant selected from the material database is set as the material constant of the structure of the analysis model, and the necessary material constant is stored in the database. 4. If not, the material constant is generated to generate an analytical model thereof.
To the stress strain analysis system according to claim 11. 13. The stress-strain analysis system according to claim 3, wherein at least changes in load conditions due to time and temperature can be input. 14. When the constant of the material is generated, an optimum constant is generated by a statistical process including at least a Weibull distribution even if the result of the material experiment has variations, and the constant representing the obtained life is used to generate the constant. The stress-strain analysis system according to any one of claims 3 to 13, wherein a predicted fracture value of the structure under an arbitrary load condition is calculated and displayed by statistical processing. 15. A stress-strain analysis method for analyzing strain of a material using a finite element method, the step of displaying a list of models of the finite element method and the list of materials to the outside, and the finite element method. The step of creating a model of the finite element method according to the instruction content from the outside based on the list of models, and the mechanical constitutive equation and its constant according to the instruction content from the outside based on the material list. The method includes a step of determining, a step of predicting a stress-strain relationship of the material using the model of the finite element method and the mechanical constitutive equation, and a step of predicting a fracture life against a load from the stress-strain relationship. A stress-strain analysis method characterized by the above. 16. A program of a stress-strain analysis method for analyzing strain of a material by using the finite element method, the method comprising: displaying a list of models of the finite element method and a list of the materials on a computer. A process for creating a model of the finite element method according to an instruction content from the outside based on a list of the model of the finite element method, and a mechanical configuration according to an instruction content from the outside based on the list of the materials A process of determining an equation and its constant, a process of predicting the stress-strain relationship of the material by using the model of the finite element method and the mechanical constitutive equation, and a fracture life against a load from the stress-strain relationship. A program for executing the processing to be performed.