Recording medium recording via lifetime calculation program, via lifetime calculation method, and information processing device

A recording medium recording a program for a process, the process includes: calculating an amount of distortion in a via of a printed circuit board based on an expression using coefficient m, Δε={(L×α×Δt×E)/(D×T)}×m, where Δε is the amount of distortion, L is a length of the via, α is a thermal expansion coefficient of a base material, Δt is a temperature change of an environment, E is a Young's modulus, D is a diameter of the via, and T is a thickness of plating in the via; and calculating a lifetime of the via based on an expression, M=N/(n×365), where M is the lifetime of the via, n is a frequency of the temperature change, and N is the number of cycles of the lifetime satisfying an expression Nx=C/Δε.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2018-4655, filed on Jan. 16, 2018 the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to a recording medium recording a via lifetime calculation program, a via lifetime calculation method, and an information processing device.

BACKGROUND

The fatigue lifetime of solder balls joining the printed circuit board and the semiconductor device is predicted. A predicted value of the lifetime of the solder joint portion is calculated.

Examples of the related art are disclosed in Japanese Laid-open Patent Publication No. 2006-313800 and Japanese Laid-open Patent Publication No. 2001-125945.

SUMMARY

According to an aspect of the embodiments, a non-transitory recording medium recording a via lifetime calculation program that causes a computer to execute a process, the process includes: calculating an amount of distortion occurring in a via of a printed circuit board based on an expression using coefficient m obtained by a stress calculation and a stress simulation which are based on a theory of material dynamics, Δε={(L×α×Δt×E)/(D×T)}×m, where Δε is the amount of distortion, L is a length of the via, α is a thermal expansion coefficient of a base material of the printed circuit board, Δt is a temperature change of an environment in which the printed circuit board is used, E is a Young's modulus of the base material of the printed circuit board, D is a diameter of the via, and T is a thickness of plating in the via; and calculating a lifetime of the via based on an expression, M=N/(n×365), where M is the lifetime of the via, n is a frequency of the temperature change, and N is the number of cycles of the lifetime satisfying an expression Nx=C/Δε, where X is a fatigue ductility exponent of a material used for plating, and C is a fatigue ductility coefficient of the material used for plating.

DESCRIPTION OF EMBODIMENTS

For example, since a printed circuit board is a composite of an insulator material (for example, an organic resin, a composite material of an organic resin and a glass cloth, and an inorganic material) and a conductive metal (for example, copper), the internal stress is generated in the insulator material and the metal when the temperature outside the printed circuit board changes. For example, cracks may occur in a via or a through hole (hereinafter simply referred to as via) in the printed circuit board depending on the internal stress generated in the insulator material and the metal. The via means a plated hole for connecting conductor layers with respect to a printed circuit board with two or more layers. Copper is often used for plating.

For example, since various electronic components such as a semiconductor device mounted on a printed circuit board are connected through the via, a connection failure may occur between the components when the crack is generated in the via. In this manner, the crack generated in the via is a factor that lowers the connection strength between the parts. Therefore, for example, reliability of the printed circuit board may be grasped at the design stage by calculating the lifetime of a via based on the crack.

For example, a via lifetime calculation program or the like capable of calculating the lifetime of the via may be provided.

Hereinafter, embodiments discussed herein will be described with reference to the drawings.

First Embodiment

FIG. 1is a diagram of an example of a via lifetime calculation system S. The via lifetime calculation system S includes a terminal device100and a server device200as a device that calculates a via lifetime. The terminal device100is used at the design stage by a designer of a printed circuit board, a person concerned, and so forth (hereinafter simply referred to as a user). InFIG. 1, although a personal computer (PC) is illustrated as an example of the terminal device100, a smart device may be used. Examples of the smart device include a smartphone and a tablet terminal. On the other hand, the server device200is provided in the data center DC or the like on a cloud CL. In this way, a base of the server device200may be different from a base of the terminal device100. The two bases may be the identical base such as the base in the identical office, for example. For example, the server device200may be a cloud type or an on-premise type.

The terminal device100and the server device200are connected to each other via a communication network NW. The communication network NW includes, for example, the Internet. Therefore, the terminal device100may be connected to the server device200through wireless communication or wired communication. When the terminal device100and the server device200are installed at the identical base, a local area network (LAN) or the like is used as the communication network NW. In this case, the server device200is provided in, for example, a server room.

The terminal device100includes an input device110, a display device120, and a control device130. The input device110and the display device120are connected to the control device130. The control device130controls the contents displayed by the display device120based on the input information input from the input device110. The control device130transmits input information input from the input device110to the server device200, and receives screen information and output information transmitted from the server device200. The control device130causes the display device120to display various screens based on the received screen information, and outputs the result processed by the server device200in the screen based on the received output information. Details of screen information and output information will be described later.

Next, with reference toFIG. 2, a hardware configuration of the server device200will be described. Since the above-described control device130basically has a hardware configuration identical to that of the server device200, its description will be omitted.

FIG. 2illustrates an example of a hardware configuration of the server device200. As illustrated inFIG. 2, the server device200includes at least a central processing unit (CPU)200A, a random access memory (RAM)200B, and a read only memory (ROM)200C as a hardware processor, and a network interface (I/F)200D. The server device200may include at least one of a hard disk drive (HDD)200E, an input I/F200F, an output I/F200G, an input/output I/F200H, and a drive device200I, as occasion arises. The CPU200A to the drive device200I are connected to each other through an internal bus200J. For example, the function of the server device200may be implemented by a computer. Instead of the CPU200A, a micro processing unit (MPU) may be used as a hardware processor.

An input device710is connected to the input I/F200F. Examples of the input device710include a keyboard and a mouse. The above-described input device110is similar to the input device710. A display device720is connected to the output I/F200G. An example of the display device720includes a liquid crystal display. The above-described display device120is similar to the display device720. A semiconductor memory730is connected to the input/output I/F200H. The semiconductor memory730includes, for example, a universal serial bus (USB) memory and a flash memory. The input/output I/F200H reads a program and data stored in the semiconductor memory730. The input I/F200F and the input/output I/F200H have, for example, USB ports. The output I/F200G has, for example, a display port.

A portable recording medium740is inserted into the drive device200I. Examples of the portable recording medium740include removable disks such as a compact disc (CD)-ROM and a digital versatile disc (DVD). The drive device200I reads a program and data recorded on the portable recording medium740. The network I/F200D has, for example, a LAN port. The network I/F200D is connected to the above-described communication network NW.

Programs stored in the ROM200C and the HDD200E are temporarily stored in the RAM200B by the CPU200A. Programs recorded in the portable recording medium740are temporarily stored in the RAM200B by the CPU200A. The stored programs are executed by the CPU200A, so that the CPU200A implements various functions to be described later and executes various processes to be described later. The program may correspond to a processing sequence diagram to be described later.

Next, functions of the terminal device100and the server device200will be described with reference toFIGS. 3 and 4.

FIG. 3is an example of a block diagram of the terminal device100and the server device200. For example,FIG. 3illustrates the main parts of the functional configurations of the control device130and the server device200.FIG. 4illustrates an example of a storage unit203.

First, the control device130will be described. As illustrated inFIG. 3, the control device130includes a communication unit131and a control unit132. The function of the communication unit131may be implemented by, for example, the above-described network I/F200D. The function of the control unit132may be implemented by, for example, the CPU200A and the RAM200B described above.

The communication unit131controls communication between the control device130and the server device200. For example, the communication unit131transmits the input information output from the control unit132to the server device200. For example, the communication unit131receives screen information and output information transmitted from the server device200, and outputs them to the control unit132. The screen information is information for causing the display device120to display various screens. The output information is information for outputting the result processed by the server device200in the output box in the screen displayed by the display device120.

The control unit132controls the operation of the terminal device100. For example, the control unit132receives input information from the input device110. The input information includes, for example, an input value input in an input box in the screen, and an instruction based on a screen operation. The control unit132receives the screen information output from the communication unit131and causes the display device120to display various screens corresponding to the screen information. The control unit132receives the output information output from the communication unit131, and outputs the result processed by the server device200to the output box in the screen displayed by the display device120.

Next, the server device200will be described. As illustrated inFIG. 3, the server device200includes a communication unit201, a processing unit202, and the storage unit203. The function of the communication unit201may be implemented by, for example, the above-described network I/F200D. The function of the processing unit202may be implemented by, for example, the CPU200A and the RAM200B described above. The function of the storage unit203may be implemented by, for example, the above-described HDD200E.

The communication unit201controls communication between the server device200and the control device130. For example, the communication unit201transmits screen information and output information output from the processing unit202to the control device130. For example, the communication unit201receives the input information transmitted from the control device130and outputs it to the processing unit202.

The processing unit202receives the input information output from the communication unit201. Upon receiving the input information, the processing unit202calculates the amount of distortion occurring in the via based on the received input information and a predetermined specific expression, and corrects the calculated amount of distortion. The via may or may not penetrate the printed circuit board. For example, the via may be a through via penetrating the printed circuit board, or may be an inner via (or a buried via) or a blind via which does not penetrate the printed circuit board. The processing unit202calculates the lifetime of the via based on the accepted input information, the calculated amount of distortion, and a predetermined specific expression, and performs the pass/fail determination of the calculated lifetime with respect to the requested lifetime. The processing unit202outputs the calculated lifetime and the result of the pass/fail determination to the communication unit201. As a result, the communication unit201transmits the output information including the lifetime and the determination result. When receiving the input information, the processing unit202may associates identification information (for example, name) for identifying the user with the received input information to store them in the storage unit203as a history. In addition, the processing unit202performs various processes, details of which will be described later.

The storage unit203stores input information. For example, as illustrated inFIG. 4, the input information is managed for each user by a management table TBL having a plurality of input fields. The length of the via, the diameter of the via, and the thickness of plating are stored in respective input fields of the via length, the via diameter, and the plating thickness. For example, information on the specification of the printed circuit board is stored. The thermal expansion coefficient, the glass transition temperature, and the Young's modulus of the base material of the printed circuit board are stored in the respective input fields of the thermal expansion coefficient, the glass transition temperature and the Young's modulus. For example, information on the physical properties of the printed circuit board is stored. The maximum temperature, the minimum temperature and the change frequency per day in the maximum temperature and the minimum temperature in the environment in which the printed circuit board, or an electronic equipment whose electronic components are mounted on the printed circuit board is used are stored in respective input fields of the maximum temperature, the minimum temperature, the temperature change frequency. For example, information on the use environment of the printed circuit board or the electronic equipment is stored. The number of years related to the lifetime and the safety factor which the printed circuit board or the electronic equipment is to have are stored in respective input fields of the requested years and the safety factor. For example, information on the condition under which the printed circuit board or the electronic equipment is used is stored. Upon detecting the specific instruction to call the input information, the processing unit202described above acquires the input information from the storage unit203and outputs it to the communication unit201.

An input field for storing information that affects the lifetime of the via may be provided in the management table TBL. Examples of the information that affects the lifetime of the via include a first coefficient corresponding to the land arrangement, a second coefficient corresponding to the via arrangement density with respect to the printed circuit board, and a third coefficient corresponding to the positional deviation between the via and the land. Examples of information that affects the lifetime of the via include a fourth coefficient corresponding to the size of the land, a fifth coefficient relating to the presence or absence of the solid layer, and a sixth coefficient relating to the physical property value of the resin filling the via. The management table TBL may store information on the specification of the printed circuit board designed by using an application program such as computer aided design (CAD) (hereinafter referred to as CAD application). The management table TBL may store information that affects the lifetime of the via designed using the CAD application.

Next, the operation of the via lifetime calculation system S will be described.

FIG. 5is an example of a processing sequence diagram (part1) of the via lifetime calculation system S.FIG. 6is an example of a processing sequence diagram (part2) of the via lifetime calculation system S. The processing sequence diagram illustrated inFIG. 5and the processing sequence diagram illustrated inFIG. 6are continuous by corresponding symbols.

First, the control unit132of the terminal device100requests screen information from the server device200(step S101). For example, when the user operates the input device110to input an instruction requesting a screen for predicting the lifetime of the via, the control unit132accepts the instruction input to the input device110. Upon receiving the instruction, the control unit132requests the server device200to transmit the screen information to the terminal device100. When the processing unit202of the server device200is requested by the terminal device100to transmit the screen information, the processing unit202transmits the screen information to the terminal device100through the communication unit201(step S201). As a result, the communication unit131of the terminal device100receives the screen information (step S102).

When the communication unit131receives the screen information, the control unit132causes the display device120to display a precaution (step S103), and causes the display device120to the first input screen (step S104). The precaution is noticed when using a process for predicting the lifetime of the via. Various pieces of information on the precaution, the first input screen, the second input screen to be described later, and the output screen are included in the screen information.

As illustrated inFIG. 7, the first input screen includes a plurality of input boxes11,12, and13for inputting the specification of the printed circuit board, and a plurality of input boxes21and23for inputting physical properties of the base material of the printed circuit board. The first input screen includes a plurality of input boxes31,32, and33for inputting the use environment of the printed circuit board or the electronic equipment, and a plurality of input boxes41,42for inputting the requested lifetime of the printed circuit board or the electronic equipment. The input values input to the plurality of input boxes11, . . . ,33are used as basic information for calculating the amount of distortion of the via. On the other hand, the input values input to the plurality of input boxes41,42are used as determination information for determining pass/fail of the lifetime of the via. For example, the safety factor, as an input value, input to the input box42is desirably appropriately selected within the range of 1.0 to 2.0 by the user since the requested values of the safety factor to be applied to electronic equipment are different for each electronic equipment.

In addition, the first input screen includes a plurality of selection boxes10,20,30, and40for selecting an input method, and a plurality of operation buttons BT1, BT2, and BT3. The operation button BT1represents an operable image area for invoking, from the storage unit203, input information corresponding to the user name and displaying the invoked input information in the plurality of corresponding input boxes11, . . . ,42. The operation button BT2represents an operable image area for causing the display device120to display a second input screen to be described later. The operation button BT3represents an operable image area for erasing numerical values displayed in the plurality of input boxes11, . . . ,42.

The user operates the input device110to perform an operation of inputting numerical values to the plurality of input boxes11, . . . ,42. The control unit132acquires the numerical values input to the input device110and causes the display device120to display the acquired numerical values in the input boxes11, . . . ,42. Upon completing the operation of inputting the numerical values into the plurality of input boxes11, . . . ,42, the user operates the input device110to perform an operation (for example, clicking) of pressing the operation button BT2. As a result, the control unit132detects an instruction to cause the display device120to display the second input screen, and causes the display device120to display the second input screen as illustrated inFIG. 5(step S105). Upon causing the display device120to display the second input screen, the control unit132waits until it detects an instruction to cause the server device200to estimate the lifetime of the via (step S106: “NO”).

As illustrated inFIG. 8, the second input screen includes an input box51for inputting an land arrangement, an input box52for inputting a via arrangement density, and an input box53for inputting a positional deviation between via and land. In addition, the second input screen includes an additional button50for adding another input box different from the plurality of input boxes51,52, and53and a plurality of operation buttons BT4, BT5, and BT6.

The numerical values input in the plurality of input boxes51,52, and53and another input box are used as correction information for correcting the amount of distortion of the via. The operation button BT4represents an operable image area for invoking, from the storage unit203, input information corresponding to the user name and displaying the invoked input information in the plurality of corresponding input boxes51,52, and53, and the like. An operation button BT5represents an operable image area for causing the server device200to predict the lifetime of the via. The operation button BT6represents an operable image area for erasing numerical values displayed in the plurality of input boxes51,52, and53, and the like.

For example, as illustrated inFIGS. 9A to 9D, a first coefficient β corresponding to the presence or absence of the land LND and the arrangement of the lands LND is input to the input box51. For example, in the case where the land LND is not disposed in the inner layer of a via V in view of the structure of the via V as illustrated inFIG. 9A, and in the case where the lands LND are arranged in the respective first layers of the via V as illustrated inFIG. 9B, 1.0, as the first coefficient β, is input to the input box51in accordance with the operation by the user. Similarly, in the case where the lands LND are arranged in the middle layers, which are the respective third layers of the via V in view of the structure of the via V as illustrated inFIG. 9C, 1.2, as the first coefficient β, is input to the input box51in accordance with the operation of the user. Similarly, in the case where the lands LND are arranged in all layers of the via V in view of the structure of the via V as illustrated inFIG. 9D, 1.6, as the first coefficient β, input to the input box51in accordance with the operation of the user. A specific numerical value of the first coefficient β may be appropriately changed within a range where the accuracy of the lifetime may be improved.

As illustrated inFIGS. 10A to 10D, a second coefficient γ corresponding to the via V arrangement density with respect to the printed circuit board PCB is input to the input box52. For example, in a case where 32 vias V (a quarter of a circle×4+a half of a circle×12+a circle×25) for an area of 1 cm2of the printed circuit board PCB are arranged in view of the structure of the via V as illustrated inFIG. 10A, 1.3 as the second coefficient γ is input to the input box52in accordance with the operation of the user. Similarly, in a case where 16 vias V (a quarter of a circle×4+a half of a circle×12+a circle×9) for an area of 1 cm2of the printed circuit board PCB are arranged in view of the structure of the via V as illustrated inFIG. 10B, 1.0 as the second coefficient γ is input to the input box52in accordance with the operation of the user. Similarly, in a case where 8 vias V (a quarter of a circle×4+a half of a circle×4+a circle×5) for an area of 1 cm2of the printed circuit board PCB are arranged in view of the structure of the via V as illustrated inFIG. 10C, 0.8 as the second coefficient γ is input to the input box52in accordance with the operation of the user. Similarly, in a case where 4 vias V (a quarter of a circle×4+a half of a circle×4+a circle×1) for an area of 1 cm2of the printed circuit board PCB are arranged in view of the structure of the via V as illustrated inFIG. 10D, 0.7 as the second coefficient γ is input to the input box52in accordance with the operation of the user. A specific numerical value of the second coefficient γ may be appropriately changed within a range where the accuracy of the lifetime may be improved.

As illustrated inFIGS. 11A to 11C, a third coefficient η corresponding to the positional deviation between the via V and the land LND is input to the input box53. For example, as illustrated inFIG. 11A, in the case of rank A where the positional deviation between the via V and the lands LND is 0 μm in the process of processing the via V, 1.0, as the third coefficient η, is input to the input box53in accordance with the operation of the user. Similarly, in the case of rank B where the positional deviation between the via V and the lands LND is more than 0 μm and equal to or less than 100 μm in the process of processing the via V as illustrated inFIG. 11B, 1.1, as the third coefficient η, is input to the input box53in accordance with the operation of the user. Similarly, in the case of rank C where the positional deviation between the via V and the lands LND is more than 100 μm in the process of processing the via V as illustrated inFIG. 11C, 1.3, as the third coefficient η, is input to the input box53in accordance with the operation of the user. A specific numerical value of the third coefficient η may be appropriately changed within the range where the accuracy of the lifetime may be improved.

As illustrated inFIGS. 12A to 12C, in a case where the additional button50is pressed, a fourth coefficient corresponding to variations in the sizes of the lands LND to the via V may be input to another input box (not illustrated). For example, in a case of rank A where the lands LND have no or few variations in size in view of the structure of the via V as illustrated inFIG. 12A, a fourth coefficient corresponding to the rank A is input to another input box in accordance with the operation of the user. Similarly, in a case of rank B where the lands LND have small variations in size in view of the structure of the via V as illustrated inFIG. 12B, a fourth coefficient corresponding to the rank B is input to another input box in accordance with the operation of the user. Similarly, in a case of rank C where the lands LND have large variations in size in view of the structure of the via V as illustrated inFIG. 12C, a fourth coefficient corresponding to the rank C is input to another input box in accordance with the operation of the user. In addition, although not illustrated, in a case where the additional button50is pressed, a fifth coefficient relating to the presence or absence of a solid layer, a sixth coefficient relating to the physical property value of the resin filling the via V, and so forth may be input in other input boxes.

The user operates the input device110to perform an operation of inputting numerical values into the plurality of input boxes51,52, and53and another input box. The control unit132acquires the numerical value input to the input device110to cause the display device120to display the acquired numerical value in the input boxes51,52, and53. Upon completion of the operation of inputting the numerical values into the plurality of input boxes51,52, and53, the user operates the input device110to perform an operation (for example, clicking) of depressing the operation button BT5. As a result, as illustrated inFIG. 5, the control unit132detects an instruction to cause the server device200to predict the lifetime of the via (step S106: “YES”), and the communication unit131transmits the basic information, the determination information, and the input information including the correction information to the server device200(step S107). When the communication unit131transmits the input information to the server device200, the control unit132causes the display device120to display an output screen (step S108). The control unit132may causes the display device120to display the output screen before transmitting the input information or may causes the display device120to display the output screen in parallel with the transmission of the input information.

As illustrated inFIG. 13A, the output screen has a plurality of output boxes61,62,63, and64for outputting prediction results. The lifetime of the via V, which is the result processed by the server device200, is output to each of the output boxes61and63. For example, the lifetime when the safety factor is 1 is output to the output box61, and the lifetime when the safety factor is the numerical value input on the first input screen is output to the output box63. On the other hand, the result of the pass/fail determination by the server device200are output to the output boxes62and64. Until receiving the output information, the control unit132causes the display device120to display an output screen on which all of the output boxes61,62,63, and64are blank.

Returning toFIG. 5, the communication unit201of the server device200receives the input information transmitted from the terminal device100(step S202). When the communication unit201receives the input information, the processing unit202calculates the amount of distortion (step S203).

For example, the processing unit202calculates the amount of distortion based on the following expression (1) using the coefficient m obtained by the stress calculation and the stress simulation based on the theory of material dynamics.
Δε={(L×α×Δt×E)/(D×T)}×m(1)

where Δε is the amount of distortion, and, in particular, represents the difference in distortion caused by the temperature change (the difference between the strain at the maximum temperature (tmax) and the strain at the minimum temperature (tmin)), L is the length of the via V, α is the thermal expansion coefficient of the base material of the printed circuit board PCB, Δt is the temperature change of the environment in which the printed circuit board PCB and electronic equipment are used, and, in particular, may be expressed by a difference value between the maximum temperature and the minimum temperature input on the first input screen, E is the Young's modulus of the base material of the printed circuit board PCB, D is the diameter of the via V, and T is the thickness of plating in the via V.

The length of the via V, the thermal expansion coefficient, the maximum temperature, the minimum temperature, the Young's modulus, the diameter of the via V, and the thickness of plating, all of which are described above, are included in the basic information of the input information. Therefore, if the coefficient m is defined in advance, the processing unit202may calculate the amount of distortion. For example, when the coefficient m is defined within the range of 0.75×10−4to 1.5×10−4, it is possible to calculate the amount of distortion with high accuracy. Furthermore, if the coefficient m is defined to be 1.4×10−4, it is possible to calculate the more accurate amount of distortion.

In the process of step S203, the processing unit202calculates the amount of distortion, and then corrects the amount of distortion (step S204).

For example, the processing unit202corrects the amount of distortion based on the following expression (4).
Δε′=Δε×β×γ×η  (4)

where β is the first coefficient corresponding to the arrangement of the lands LND, γ is the second coefficient corresponding to the via V arrangement density with respect to the printed circuit board PCB, and η is the third coefficient corresponding to the positional deviation between the via V and the land LND. The expression (4) may be multiplied by at least one of the fourth to sixth coefficients described above. One or two of the first coefficient to the third coefficient may be excluded from the expression (4). The processing unit202may not perform the process of step S204, but the calculation accuracy of the lifetime of the via V may be improved by performing the process of step S204. The first coefficient and the third coefficient are included in the correction information of the input information. On the other hand, the fourth coefficient to the sixth coefficient may or may not be included in the correction information of the input information.

In the process of step S204, the processing unit202corrects the amount of distortion, and then calculates the lifetime as illustrated inFIG. 6(step S205).

For example, the processing unit202calculates the lifetime based on the expression (2).
M=N/(n×365)  (2)

where M is the lifetime of the via V, N is the number of cycles of the lifetime that satisfies the expression (3) according to the Coffin-Manson rule described below, and n is the frequency of the temperature change.
Nx=C/Δε(3)

where x is the fatigue ductility exponent of the material used for plating, and C is the fatigue ductility coefficient of the material used for plating.

The above-described frequency of the temperature change is included in the basic information of the input information. Therefore, if the fatigue ductility exponent and the fatigue ductility coefficient are defined in advance, the processing unit202may calculate the lifetime. For fatigue ductility exponent and fatigue ductility coefficient, it is desirable to use values obtained from experiments on disruptive strength of copper.

In the process of step S205, the processing unit202calculates the lifetime, and then performs the pass/fail determination (step S206). For example, the processing unit202compares the lifetime calculated in the process in step S205with the requested lifetime set as the lifetime requested for the via V to determines whether the calculated lifetime of the via V satisfies the requested lifetime.

For example, when the lifetime calculated in the process of step S205is equal to or longer than the requested lifetime, the processing unit202determines that the calculated lifetime of the via V satisfies the requested lifetime. When the lifetime calculated by the process of step S205is less than the requested lifetime, the processing unit202determines that the lifetime of the calculated via V does not satisfy the requested lifetime. The processing unit202calculates the requested lifetime based on the requested years for the safety factor (requested years/safety factor) to perform the pass/fail determination. For example, the processing unit202calculates the requested lifetime when the safety factor is 1 and the requested lifetime when the safety factor is the numerical value input on the first input screen to perform the pass/fail determination. The requested years and the safety factor are included in the determination information of the input information as described above.

In the process of step S206, when the processing unit202performs the pass/fail determination, the communication unit201transmits the output information (step S207). For example, the processing unit202outputs to the communication unit201the calculated lifetime and the result of the pass/fail determination by combining them for each safety factor and the communication unit201transmits the output information including the lifetime and the determination result for each safety factor. For example, the processing unit202outputs the output information to the terminal device100through the communication unit201. In this embodiment, a character string such as “OK” or “NG” is used as a determination result, but symbols such as “◯” or “x” may be used.

The communication unit131of the terminal device100receives the output information transmitted from the server device200(step S109). When the communication unit131receives the output information, the control unit132outputs the lifetime and the determination result (step S110). For example, the control unit132outputs the lifetime and the determination result for each safety factor to the output boxes61,62,63, and64of the output screen. As a result, as illustrated inFIG. 13B, the lifetime of the via V when the safety factor is 1 is output to the output box61, and the determination result with respect to the requested lifetime is output to the output box62. Similarly, the lifetime of the via V when the safety factor is the input value is output to the output box63, and the determination result with respect to the requested lifetime is output to the output box64.

As described above, according to the first embodiment, the server device200includes the processing unit202. The processing unit202may calculate the amount of distortion representing a quantity of distortion occurring in the via V (for example, the inside of the via V) of the printed circuit board PCB based on the above-described expression (1), and may calculate the lifetime of the via V based on the above-described expressions (2) and (3). As a result, the user may grasp the reliability of the printed circuit board PCB at the design stage, and may take countermeasures at an early stage, for example change the design at an appropriate time.

For example, as illustrated inFIG. 14, since the physical properties of the base material of the printed circuit board PCB and the via V having the land LND are different from each other, when the temperature outside the printed circuit board PCB changes, a crack V1may occur in the via V due to the difference in the respective internal stresses F1and F2. If the crack V1occurs before the requested lifetime, the printed circuit board PCB may not operate properly due to the crack V1. However, according to the first embodiment, since the user may design the printed circuit board PCB after predicting the lifetime of the via V, the reliability of the printed circuit board PCB may be secured. In the printed circuit board PCB in which materials having different thermal expansion coefficients are combined, the internal stress is generated at the via V due to the temperature change. Therefore, the internal stress similarly occurs when the insulator material is an inorganic material. In this case, it is possible to estimate the lifetime of the via V by calculating the amount of distortion of the via V by utilizing the simulation and so forth.

Second Embodiment

A second embodiment discussed herein will be described with reference toFIG. 15.FIGS. 15A to 15Dare diagrams for describing an example of an input method. For example, in the above-described first embodiment, as illustrated inFIG. 15A, since a input method by direct input is selected in the selection box10, a method of directly inputting numerical values to a plurality of input boxes11,12, and13is employed. However, the input method selected in the selection box10is not limited to the input method by the direct input. For example, as illustrated inFIG. 15B, an input method according to a design specification predetermined in the selection box10may be selected. For example, when the design specification SP1is selected, the control unit132outputs the via length, the via diameter, and the plating thickness associated with the design specification SP1to the plurality of input boxes11,12, and13, respectively.

As illustrated inFIG. 15C, another input box14and an operation button BT7different from the plurality of input boxes11,12, and13may be provided in the first input screen are provided, and the via length, the via diameter, and the plating thickness of the CAD data input to the input box14may be read by depressing the operation button BT7. When such an operation is performed, the control unit132outputs the via length, the via diameter, and the plating thickness to the plurality of input boxes11,12, and13, respectively. Similarly, as illustrated inFIG. 15D, another input box15different from the plurality of input boxes11,12, and13and an operation button BT8may be provided in the first input screen, and the via length, the via diameter, and the plating thickness of the data which were input to the input box15and that were used in the past may be read by depressing the operation button BT8. When such an operation is performed, the control unit132outputs the via length, the via diameter, and the plating thickness to the plurality of input boxes11,12, and13, respectively. With the input method described above, it is possible to reduce the labor of input by the user. In the second embodiment, the specification of the printed circuit board have been described as an example, but the physical properties, the use environment, and the requested lifetime of the base material of the printed circuit board are also similarly processed as in the specification of the printed circuit board.

Third Embodiment

A third embodiment discussed herein will be described with reference toFIG. 16.FIG. 16is a diagram for describing an example of a output method. As illustrated inFIG. 16, the control unit132may output a pop-up screen91including the lifetime of the via V on a design screen90created using the CAD application. The control unit132may output a pop-up screen92including the lifetime of the via V to the outside of the design screen90in association with the via V in the design screen90. The control unit132may output a pop-up screen93including countermeasures to satisfy the requested lifetime together with the lifetime of the via V. The control unit132may output a pop-up screen94including the probability of lifetime prediction calculated using an artificial intelligence (AI). The lifetime of the via V may be linked with the CAD application by the above-described output method.

Fourth Embodiment

A fourth embodiment discussed herein will be described. In the first embodiment described above, the processing unit202calculates the amount of distortion based on the expression (1). On the other hand, as described in the fourth embodiment, instead of expression (1), the processing unit202may analyze statistically the influence degree of each factor from the result of the stress simulation with factors that affect the amount of distortion of the via V as variables to calculate the amount of distortion based on the following approximate expression (5) which synthesizes a function of each factor and a function including the interaction of these factors. Factors that affect the amount of distortion of the via V include, for example, the length of the via V, the diameter of the via V, the thickness of the plating in the via V, the thermal expansion coefficient of the base material of the printed circuit board PCB, the Young's modulus of the base material of the printed circuit board PCB, and temperature change in the environment in which the printed circuit board is used.
Δε={a×f(L)+b×f(T)+c×f(D)+d×f(α)+e×f(E)+g×f(L,T,D,α,E)}×Δt(5)

where Δε is the amount of distortion, in particular, represents the difference in distortion caused by the temperature change (the difference between the strain at the maximum temperature (tmax) and the strain at the minimum temperature (tmin)), L is the length of the via, α is the thermal expansion coefficient of the base material of the printed circuit board, Δt is the temperature change of the environment in which the printed circuit board is used, E is the Young's modulus of the base material of the printed circuit board, D is the diameter of the via, T is the thickness of the plating in the via, and a, b, c, d, e, and g are coefficients of an approximate expression of a simulation result by a stress simulation using, as variables, the length of the via, the diameter of the via, the thickness of the plating in the via, the thermal expansion coefficient of the base material of the printed circuit board, the Young's modulus of the base material of the printed circuit board, and the temperature change in the environment in which the printed circuit board is used. For example, the approximate expression (5) is an equation which is synthesized by carrying out a stress simulation with factors that affect the amount of distortion of the via as a variable to statistically analyze the influence degree of each factor. a, b, c, d, e, and g are coefficients of the approximate expression by the stress simulation result.

The approximate expression (6) described below may be used as an example of the approximate expression (5) described above.
Δε={a×ln(L)+b×T+c×T0.4+d×D−0.2+e×E2+f×E+(g×E+h×T+i)×α+j}×Δt(6)

where Δε is the amount of distortion, and in particular, represents the difference in distortion caused by the temperature change (the difference between the strain at the maximum temperature (tmax) and the strain at the minimum temperature (tmin)), L is the length of the via, α is the thermal expansion coefficient of the base material of the printed circuit board, Δt is the temperature change of the environment in which the printed circuit board is used, E is the Young's modulus of the base material of the printed circuit board, D is the diameter of the via, and T is the thickness of the plating in the via. For example, the approximate expression (6) is also an equation which is synthesized by carrying out a stress simulation with factors that affect the amount of distortion of the via as a variable to statistically analyze the influence degree of each factor. a, b, c, d, e, f, g, h, i, and j are coefficients of the approximate expression of the stress simulation result. In this manner, the processing unit202may calculate the amount of distortion of the via V based on the approximate expression (5) or the approximate expression (6), and may calculate the lifetime of the via V based on the above-described expressions (2) and (3).

Although the exemplary embodiments of the present disclosure has been described in detail above, the present disclosure is not limited to such specific embodiments, but various modifications and alterations may be made without departing from the spirit and scope of the present disclosure set forth in the claims. For example, in the above-described first embodiment, the control unit132causes the display device120to display the first input screen, the second input screen, and the output screen separately, but may causes the display device120to display an input/output screen in which the first input screen, the second input screen, and the output screen are combined into one. Part or all of the processing performed by the processing unit202may be performed by the control unit132.