Material selection assistance device, method for manufacturing circuit board, circuit board core, and circuit board

Abstract

A relationship estimation unit (32) estimates a correspondence relationship between a combination of a coefficient of thermal expansion and an elastic modulus of a circuit board core and a combination of a coefficient of thermal expansion and an elastic modulus of a circuit board using the circuit board core. A reception unit (34) receives a coefficient of thermal expansion of a substrate joined to the circuit board by solder. A reliability estimation unit (36) estimates, for each combination of the coefficient of thermal expansion and the elastic modulus of the circuit board, the reliability of the solder when the substrate and the circuit board are joined by solder. A calculation unit (38) calculates, on the basis of the correspondence relationship, the range of the combination of the coefficient of thermal expansion and the elastic modulus of the circuit board core corresponding to the combination of the coefficient of thermal expansion and the elastic modulus of the circuit board having a reliability greater than or equal to a prescribed value.

Description

Material selection support device, circuit board manufacturing method, circuit board core, and circuit board

[0001] The present disclosure relates to a material selection assistance device, a circuit board manufacturing method, a circuit board core, and a circuit board.

[0002] A semiconductor device is manufactured by soldering a substrate of a semiconductor package including a substrate, a chip, and a heat spreader to a circuit board. Because solder joints are susceptible to damage due to warping of the board, it is desirable to select materials for the substrate and the circuit board that will improve the reliability of the solder.

[0003] Therefore, a wiring board capable of suppressing the occurrence of warpage has been proposed. This wiring board has an insulating layer made of insulating resin containing glass cloth, a wiring layer filled in a recess formed in the lower surface of the insulating layer, a wiring structure laminated on the upper surface of the insulating layer, and a solder resist layer formed on the lower surface of the insulating layer. The lower surface of the wiring layer is formed so as to be recessed toward the wiring structure relative to the lower surface of the insulating layer. The solder resist layer is formed so as to cover a portion of the lower surface of the wiring layer and to cover the inner surface of the recess exposed from the wiring layer. The glass cloth is located closer to the wiring structure than the center of the thickness of the insulating layer and is positioned at the center of the thickness from the lower surface of the insulating layer to the upper surface of the wiring layer, the top layer of the wiring structure (see Patent Document 1).

[0004] Also proposed is a semiconductor device that improves connection reliability with other wiring boards by suppressing stress concentration within conductor posts formed on a wiring conductor layer of a printed wiring board. This semiconductor device includes a wiring conductor layer having a first surface and a second surface, and a conductor post formed on a portion of the second surface of the wiring conductor layer. This semiconductor device also includes a resin insulating layer having a first surface and a second surface, in which the wiring conductor layer is embedded so that the first surface is exposed on the first surface, and covering the side surfaces of the conductor posts. The end surface of the conductor post opposite the wiring conductor layer is exposed on the second surface of the resin insulating layer, and the side surface of the conductor post is curved at the end of the conductor post facing the wiring conductor layer, curving outward toward the conductor post as it approaches the wiring conductor layer. The resin insulating layer is made of a molding resin material with a thermal expansion coefficient of 6 to 25 ppm / °C and an elastic modulus of 5 to 30 GPa (see Patent Document 2).

[0005] Also proposed is a wiring board that provides excellent durability for semiconductor packages. The wiring board includes a core substrate, a conductor pattern, and an insulating resin film. The conductor pattern is provided on at least one outermost surface of the core substrate. The insulating resin film is the outermost layer of the wiring board and is provided on the conductor pattern. The insulating resin film has a plurality of openings, and a portion of the conductive portion of the conductor pattern is located within at least one opening. The insulating resin film also has a storage modulus at 25°C of 1 GPa to 20 GPa, and a linear thermal expansion coefficient of 10 ppm / °C to 50 ppm / °C below Tg (see Patent Document 3).

[0006] JP 2022-16495 A JP 2016-92365 A JP 2016-31985 A

[0007] To improve solder reliability, it is desirable for the physical properties of the substrate and the circuit board to be equivalent, so it is conceivable to select a circuit board with physical properties close to those of the substrate. However, since the physical properties of the circuit board core used in the circuit board change depending on the circuit board, it is difficult to select an appropriate circuit board core that corresponds to a substrate with the desired physical properties.

[0008] The present disclosure has been made in consideration of the above points, and aims to provide a material selection assistance device that can assist in the selection of a material that improves solder reliability for a circuit board core of a circuit board that is soldered to a substrate of a semiconductor package. The present disclosure also aims to provide a method for manufacturing a circuit board using a circuit board core selected by the material selection assistance device, the selected circuit board core, and a circuit board manufactured using the circuit board core.

[0009] To achieve the above object, a material selection assistance device according to the present disclosure includes a relationship estimation unit that estimates a correspondence relationship between a combination of a thermal expansion coefficient and an elastic modulus of a circuit board core and a combination of a thermal expansion coefficient and an elastic modulus of a circuit board using the circuit board core, a receiving unit that receives a thermal expansion coefficient of a substrate to be soldered to the circuit board, a reliability estimation unit that estimates the reliability of the solder when the substrate and the circuit board are soldered together for each combination of a thermal expansion coefficient and an elastic modulus of the circuit board, and a calculation unit that calculates, based on the correspondence relationship, a range of combinations of a thermal expansion coefficient and an elastic modulus of the circuit board core that correspond to combinations of a thermal expansion coefficient and an elastic modulus of the circuit board that result in the reliability being equal to or greater than a predetermined value. This makes it possible to assist in the selection of a material that improves solder reliability for a circuit board core of a circuit board to be soldered to a substrate of a semiconductor package.

[0010] The relationship estimation unit may estimate the correspondence relationship by homogenization, which estimates physical properties of a material obtained by joining the plurality of materials based on the physical properties of each of the plurality of materials.

[0011] Furthermore, the reliability estimation unit may estimate the reliability of the solder for each combination of the thermal expansion coefficient and elastic modulus of the circuit board based on the physical properties of the substrate, including the thermal expansion coefficient, and the physical properties of the circuit board, including the thermal expansion coefficient and elastic modulus, received by the receiving unit, and the calculation unit may identify a range surrounded by contour lines indicating the predetermined value of reliability in a space with the thermal expansion coefficient and elastic modulus of the circuit board as the two axes, where the reliability is expressed by contour lines connecting points with similar reliability, as the range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board where the reliability is equal to or greater than the predetermined value.

[0012] The calculation unit may also convert the identified range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board into a range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board core based on the correspondence relationship.

[0013] In addition, the manufacturing method for a circuit board according to the present disclosure is a manufacturing method for selecting a circuit board core whose thermal expansion coefficient and elastic modulus fall within the range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board core calculated by the material selection assistance device, laminating a prepreg with copper foil on the selected circuit board core, and etching the copper foil to form a circuit.

[0014] Furthermore, the circuit board core according to the present disclosure is a circuit board core used for a circuit board on which a semiconductor package is mounted, the circuit package including a substrate having a 25 mm square chip with a thickness of 0.725 mm and a 1.5 mm thick copper heat spreader mounted thereon, the substrate having a circuit layer structure of 5-2-5, a size of 60 mm square, and a core base material with a thickness of 0.8 mm, and the circuit board core has a modulus of elasticity E and a modulus of thermal expansion α that satisfy E≧4 GPa, α≦12.5 ppm / K, E≦(6×α−35) GPa, and E≧(1.33×α−8.67) GPa, based on the range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board core calculated by the material selection assistance device described above.

[0015] The circuit board according to the present disclosure is a circuit board obtained by laminating a prepreg with copper foil on the circuit board core and etching the copper foil to form a circuit.

[0016] The material selection assisting device according to the present disclosure can assist in the selection of a material that improves solder reliability for a circuit board core of a circuit board that is soldered to a substrate of a semiconductor package. Furthermore, by using the circuit board core selected by the material selection assisting device according to the present disclosure, it is possible to provide a circuit board manufacturing method, a circuit board core, and a circuit board that improve solder reliability.

[0017] 1 is an external perspective view showing a schematic configuration of a semiconductor device; FIG. 2 is a cross-sectional view showing a schematic configuration of a semiconductor device; FIG. 3 is a block diagram showing a hardware configuration of a material selection assistance device; FIG. 4 is a block diagram showing an example of a functional configuration of a material selection assistance device; FIG. 5 is a diagram for explaining estimation of a correspondence relationship between characteristics of a motherboard core and a motherboard; FIG. 6 is a diagram showing an example of a correspondence DB; FIG. 7 is a diagram showing an example of a life cycle indicating reliability; FIG. 8 is a diagram showing an example of a range of physical properties of a motherboard core; FIG. 9 is a diagram showing an example of a material DB showing another example of a range of physical properties of a motherboard core; FIG. 10 is a diagram showing an example of a recommended material screen; FIG. 11 is a flowchart showing the flow of material selection assistance processing.

[0018] An example of this embodiment will be described below with reference to the drawings. The same or equivalent components and parts in each drawing are designated by the same reference numerals. The dimensions and proportions of the drawings are exaggerated for the sake of explanation and may differ from the actual proportions.

[0019] <Configuration of Semiconductor Device> Fig. 1 is an external perspective view showing a schematic configuration of a semiconductor device 100 according to this embodiment. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. Note that some wiring layers, insulating layers, etc. are omitted from Figs. 1 and 2.

[0020] 1 and 2, a semiconductor device 100 is configured by mounting a semiconductor package 110 on a motherboard 102, which is a circuit board. The motherboard 102 includes a motherboard core 104, which is a circuit board core, and a circuit 106 formed by etching copper foil. The semiconductor package 110 includes a substrate 112, a chip 114, and a heat spreader 116. The lower diagram of FIG. 1 shows the configuration of the upper diagram of FIG. 1 , excluding the heat spreader 116. The motherboard 102 and the substrate 112 of the semiconductor package 110 are joined by solder 120.

[0021] <Material Selection Support Device> Fig. 3 is a block diagram showing the hardware configuration of a material selection support device 10 according to this embodiment. As shown in Fig. 3, the material selection support device 10 has a CPU (Central Processing Unit) 12, a memory 14, a storage device 16, an input device 18, an output device 20, a storage medium reader 22, and a communication I / F (Interface) 24. Each component is connected to each other via a bus 26 so as to be able to communicate with each other.

[0022] The storage device 16 stores a material selection assistance program for executing the material selection assistance process described below. The CPU 12 is a central processing unit that executes various programs, controls each component, etc. That is, the CPU 12 reads the program from the storage device 16 and executes the program using the memory 14 as a work area. The CPU 12 controls each component and performs various arithmetic operations in accordance with the program stored in the storage device 16.

[0023] The memory 14 is configured with RAM (Random Access Memory) and serves as a working area for temporarily storing programs and data. The storage device 16 is configured with ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), etc., and stores various programs including the operating system and various data.

[0024] The input device 18 is a device for performing various inputs, such as a keyboard, a mouse, etc. The output device 20 is a device for outputting various information, such as a display, a printer, etc. A touch panel display may be used as the output device 20 to function as the input device 18.

[0025] The storage medium reader 22 reads data stored in various storage media such as CD (Compact Disc)-ROM, DVD (Digital Versatile Disc)-ROM, Blu-ray Disc, USB (Universal Serial Bus) memory, etc., and writes data to the storage media. The communication I / F 24 is an interface for communicating with other devices, and uses standards such as Ethernet (registered trademark), FDDI, and Wi-Fi (registered trademark).

[0026] Next, the functional configuration of the material selection assisting device 10 according to this embodiment will be described.

[0027] Fig. 4 is a block diagram showing an example of the functional configuration of the material selection assisting device 10. As shown in Fig. 4, the functional configuration of the material selection assisting device 10 includes a relationship estimation unit 32, a reception unit 34, a reliability estimation unit 36, a calculation unit 38, and a presentation unit 40. A correspondence DB (database) 50 and a material DB 52 are stored in a predetermined storage area of ​​the material selection assisting device 10. Each functional configuration is realized when the CPU 12 reads out a material selection assisting program stored in the storage device 16, expands it into the memory 14, and executes it.

[0028] The relationship estimation unit 32 estimates the correspondence between the combination of the thermal expansion coefficient and elastic modulus of the motherboard core 104 and the combination of the thermal expansion coefficient and elastic modulus of the motherboard 102 that uses the motherboard core 104. Specifically, the relationship estimation unit 32 estimates the correspondence by homogenization, which estimates the physical properties of a material obtained by joining multiple materials together, based on the physical properties of each of the multiple materials.

[0029] More specifically, the relationship estimation unit 32 sets a plurality of virtual physical properties each combining a coefficient of thermal expansion and a coefficient of elasticity of any value. For example, as shown in the upper diagram of FIG. 5 , the relationship estimation unit 32 sets virtual physical properties (black circles in FIG. 5 ) in a space having two axes, the coefficient of thermal expansion and the coefficient of elasticity. In the example of FIG. 5 , the numbers written next to the black circles representing virtual physical properties are numbers for identifying each virtual physical property. The virtual physical properties may include properties equivalent to the actual physical properties of the motherboard core 104 registered in the material DB 52 described below. Furthermore, the virtual physical properties may be set without bias within a range that includes the actual physical properties of the motherboard core 104 registered in the material DB 52.

[0030] The relationship estimation unit 32 estimates the thermal expansion coefficient and elastic modulus of a virtual motherboard using a virtual motherboard core with each virtual physical property by homogenization using the thermal expansion coefficient, elastic modulus, Poisson's ratio, volume ratio, and copper circuit pattern of each virtual motherboard core as parameters. The Poisson's ratio may be the Poisson's ratio of an actual motherboard core whose physical properties are similar to those of the virtual physical properties. The volume ratio is the ratio of the volume of the virtual motherboard core to the volume of the copper foil in the virtual motherboard, and may be determined based on predetermined design information for the virtual motherboard. Furthermore, since the copper circuit pattern is unknown at the time of estimation, a predetermined pattern such as a grid pattern may be used.

[0031] The lower diagram in Figure 5 shows the combination of the estimated thermal expansion coefficient and elastic modulus of the virtual motherboard. As shown in Figure 5, a motherboard using a motherboard core with low elasticity and low thermal expansion will have higher thermal expansion properties than one using a motherboard core with high elasticity. In other words, to improve the reliability of the solder 120 between the substrate 112 and the motherboard 102, a motherboard core 104 with a thermal expansion coefficient equivalent to that of the substrate 112 is selected. In this case, a mismatch in the thermal expansion coefficients occurs between the substrate 112 and the motherboard 102. Therefore, to ensure good solder reliability, it is important to understand the correspondence between the physical properties of the motherboard core 104 and the motherboard 102.

[0032] The relationship estimation unit 32 stores, in a correspondence DB 50 such as that shown in FIG. 6, a combination of the thermal expansion coefficient and elastic modulus of a virtual motherboard core and a combination of the thermal expansion coefficient and elastic modulus estimated for a virtual motherboard that uses that virtual motherboard core, in association with each other.

[0033] The receiving unit 34 receives physical property information including the thermal expansion coefficient of the substrate 112 used in the semiconductor device 100. Physical property information other than the thermal expansion coefficient is received as parameters necessary for estimating reliability in the reliability estimation unit 36, which will be described later. In this embodiment, in order to estimate the temperature cycle life of the solder as reliability, the receiving unit 34 receives the shape, elastic modulus, and Poisson's ratio of the substrate 112 in addition to the thermal expansion coefficient of the substrate 112. Furthermore, the receiving unit 34 receives a plasticity curve of the solder 120.

[0034] The reliability estimation unit 36 ​​estimates the reliability of the solder 120 when the substrate 112 and the motherboard 102 are joined by the solder 120 for each combination of the thermal expansion coefficient and elastic modulus of the motherboard 102. Specifically, the reliability estimation unit 36 ​​estimates the life of the solder 120 as reliability in accordance with the physical properties of the motherboard 102, based on the physical properties of the substrate 112 received by the reception unit 34 and the physical properties of the motherboard 102, including the thermal expansion coefficient and elastic modulus.

[0035] More specifically, the reliability estimation unit 36 ​​creates a simulation model in which the substrate 112 indicated by the physical property information received by the receiving unit 34 is joined with the motherboard 102 having various physical properties by the solder 120. For each simulation model, the reliability estimation unit 36 ​​calculates the nonlinear distortion of the solder 120 when a predetermined temperature change is repeatedly applied as one cycle. The reliability estimation unit 36 ​​inputs the calculated nonlinear distortion into the Coffin-Manson law, which was created in advance in a separate test, and estimates the number of cycles until the solder 120 breaks.

[0036] FIG. 7 shows an example of the life cycle of the solder 120 estimated by the reliability estimation unit 36. In the example of FIG. 7, reliability is expressed by contour lines connecting points with similar life cycles in a space with the thermal expansion coefficient and elastic modulus of the motherboard 102 as the two axes. When simply specifying a motherboard 102 with a thermal expansion coefficient similar to that of the substrate 112, a motherboard 102 with physical properties on or near the solid line S in FIG. 7 is specified. In this embodiment, by estimating the reliability of the solder 120 as shown in FIG. 7, the required physical properties of the motherboard 102 can be specified as a range of combinations of the thermal expansion coefficient and elastic modulus of the motherboard 102.

[0037] The calculation unit 38 calculates a range of combinations of the thermal expansion coefficient and the elastic modulus of the motherboard core 104 corresponding to the combinations of the thermal expansion coefficient and the elastic modulus of the motherboard 102 that result in reliability equal to or greater than a predetermined value, based on the correspondence estimated by the relationship estimation unit 32. Specifically, the calculation unit 38 specifies, in the reliability represented by contour lines as shown in FIG. 7 , a range surrounded by contour lines indicating the predetermined value of reliability, as the range of combinations of the thermal expansion coefficient and the elastic modulus of the motherboard 102 that result in reliability equal to or greater than the predetermined value. The calculation unit 38 converts the specified range of combinations of the thermal expansion coefficient and the elastic modulus of the motherboard 102 into a range of combinations of the thermal expansion coefficient and the elastic modulus of the motherboard core 104, based on the correspondence estimated by the relationship estimation unit 32.

[0038] More specifically, the calculation unit 38 calculates a conversion formula for converting the physical properties of the motherboard 102 into the physical properties of the motherboard core 104 based on the correspondence stored in the correspondence DB 50. Then, based on the calculated conversion formula, the calculation unit 38 converts the contour lines of a predetermined value of life cycles (e.g., 1000 cycles) corresponding to the physical properties of the motherboard 102 into contour lines corresponding to the physical properties of the motherboard core 104. FIG. 8 shows an example of the contour lines of the predetermined value of life cycles after conversion. By selecting a motherboard core 104 with a combination of physical properties, i.e., a thermal expansion coefficient and an elastic modulus, that fall within the converted contour lines, it is possible to manufacture a motherboard 102 with required physical properties.

[0039] If the thermal expansion coefficient of the motherboard core 104 is close to that of the substrate 112, the gap in the thermal expansion coefficient between the substrate 112 and the motherboard 102 will be small, thereby suppressing warpage, and if the motherboard core 104 has high elasticity, deformation of the motherboard 102 itself will be less likely to occur, which obviously further suppresses warpage, and therefore the life cycle will not be reduced. Therefore, the range indicated by the contour lines corresponding to the physical properties of the motherboard core 104 may be the range shown in Figure 9.

[0040] Also, instead of using the correspondence DB 50, a conversion formula calculated from the correspondence DB 50 may be stored in advance.

[0041] The presenting unit 40 presents to the user a range of combinations of the coefficient of thermal expansion and the modulus of elasticity of the motherboard core 104 that results in a reliability equal to or greater than a predetermined value for the substrate 112 having the physical properties received by the receiving unit 34. The presenting unit 40 also presents, as recommended motherboard cores, motherboard cores 104 registered in the material DB 52 whose combinations of the coefficient of thermal expansion and the modulus of elasticity fall within the range. The material DB 52 stores, for example, as shown in FIG. 10 , physical properties such as the actual coefficient of thermal expansion and the modulus of elasticity associated with the material name of the motherboard core 104.

[0042] For example, the presentation unit 40 displays a recommended material screen 60 as shown in FIG. 11 on a display, which is an example of the output device 20. In the example of FIG. 11, the recommended material screen 60 includes a first display area 62, a second display area 64, and a third display area 66. The first display area 62 displays contour lines of a life cycle corresponding to the physical properties of the motherboard 102. The first display area 62 may also display points indicating virtual physical properties and the thermal expansion coefficient of the substrate 112 received by the receiving unit 34. The second display area 64 displays contour lines of predetermined values ​​corresponding to the physical properties of the motherboard core 104. The second display area 64 may also display points indicating virtual physical properties. The third display area 66 displays, as recommended motherboard cores, the names of materials for the motherboard core 104 whose combinations of thermal expansion coefficient and elastic modulus are included within the range of the contour lines displayed in the second display area 64.

[0043] The first display area 62 may accept a predetermined value for the life cycle by selecting a contour line, selecting a contour line legend, inputting a numerical value for the life cycle, or the like. In this case, each time the presentation unit 40 accepts the selection of a predetermined value for the life cycle, it causes the calculation unit 38 to calculate a range of combinations of the thermal expansion coefficient and elastic modulus of the motherboard core 104 according to the selected predetermined value. Then, the presentation unit 40 updates the display in the second display area 64 and the third display area 66 according to the calculated range.

[0044] Next, the operation of the material selection assisting device 10 according to this embodiment will be described. Fig. 12 is a flowchart showing the flow of the material selection assisting process executed by the CPU 12 of the material selection assisting device 10. The CPU 12 reads the material selection assisting program from the storage device 16, loads it into the memory 14, and executes it, causing the CPU 12 to function as each functional component of the material selection assisting device 10, and the material selection assisting process shown in Fig. 12 is executed.

[0045] In step S10, the relationship estimation unit 32 estimates the correspondence between the combination of the thermal expansion coefficient and elastic modulus of the motherboard core 104 and the combination of the thermal expansion coefficient and elastic modulus of the motherboard 102 using that motherboard core 104 through homogenization.

[0046] Next, in step S12 , the receiving unit 34 receives physical property information including the thermal expansion coefficient of the substrate 112 used in the semiconductor device 100 .

[0047] Next, in step S14, the reliability estimation unit 36 ​​estimates the reliability of the solder 120 when the substrate 112 and the motherboard 102 are joined by the solder 120 for each combination of the thermal expansion coefficient and elastic modulus of the motherboard 102.

[0048] Next, in step S16, the calculation unit 38 calculates, based on the correspondence estimated in step S10, the range of combinations of the thermal expansion coefficient and elastic modulus of the motherboard core 104 that correspond to the combinations of the thermal expansion coefficient and elastic modulus of the motherboard 102 that result in reliability above a predetermined value.

[0049] Next, in step S18, the presentation unit 40 displays the recommended material screen 60 including the range of combinations of the thermal expansion coefficient and elastic modulus of the motherboard core 104 calculated in step S16 above, and the recommended motherboard cores that fall within that range, and the material selection support process ends.

[0050] As described above, the material selection assisting device according to this embodiment estimates the correspondence between the combination of the thermal expansion coefficient and elastic modulus of a motherboard core and the combination of the thermal expansion coefficient and elastic modulus of a motherboard using that motherboard core. The material selection assisting device also receives the thermal expansion coefficient of a substrate to be soldered to the motherboard. The material selection assisting device also estimates the reliability of solder when the substrate and the motherboard are soldered together for each combination of the thermal expansion coefficient and elastic modulus of the motherboard. Based on the estimated correspondence, the material selection assisting device then calculates a range of combinations of the thermal expansion coefficient and elastic modulus of the motherboard core that correspond to combinations of the thermal expansion coefficient and elastic modulus of the motherboard that result in reliability equal to or greater than a predetermined value. This allows for assistance in selecting a material that improves solder reliability.

[0051] As described above, to ensure reliable soldering between a substrate and a motherboard, it is necessary to design the substrate and motherboard to have similar coefficients of thermal expansion. Furthermore, a motherboard is formed by etching copper foil onto a motherboard core to form a circuit. Therefore, the physical properties of the motherboard are affected by the physical properties of the motherboard core and the physical properties of the copper foil. The smaller the modulus of elasticity of the motherboard core, the more pronounced the physical properties of the copper foil. Therefore, in order to design the thermal expansion coefficient of the motherboard to be similar to that of the substrate, it is difficult to select an appropriate motherboard core; for example, the lower the modulus of elasticity of the motherboard core, the lower the thermal expansion coefficient of the motherboard core. According to this embodiment, a motherboard core that provides solder reliability above a predetermined value can be easily selected for the specified physical properties of the substrate.

[0052] Furthermore, unlike the inventions described in Patent Documents 2 and 3, which specify the ranges of the thermal expansion coefficient and the elastic modulus, in this embodiment, the physical properties of the motherboard core that provide good reliability are specified based on the relationship between the thermal expansion coefficient and the elastic modulus. Specifically, as shown in Figure 8, by specifying the range based on the value of the elastic modulus that changes with the thermal expansion coefficient (the diagonal line in Figure 8), it becomes possible to select a more appropriate material than in the prior art.

[0053] In the above embodiment, the material selection assistance process executed by the CPU by reading software (programs) may be executed by various processors other than the CPU. Examples of such processors include dedicated electrical circuits, such as programmable logic devices (PLDs) (such as field-programmable gate arrays (FPGAs)) whose circuit configuration can be changed after manufacture, and application-specific integrated circuits (ASICs) that are processors with circuit configurations specifically designed to execute specific processes. The material selection assistance process may be executed by one of these various processors, or by a combination of two or more processors of the same or different types (e.g., multiple FPGAs, or a combination of a CPU and an FPGA). The hardware structure of these various processors is, more specifically, an electrical circuit that combines circuit elements such as semiconductor devices.

[0054] In the above embodiment, the material selection assistance program is pre-stored (installed) in a storage device, but this is not limiting. The program may be provided in a form stored in a storage medium such as a CD-ROM, a DVD-ROM, or a USB memory. The program may also be downloaded from an external device via a network.

[0055] <Method for Manufacturing Circuit Board> A method for manufacturing a motherboard 102, which is a circuit board according to this embodiment, first includes a step of selecting a motherboard core 104 whose thermal expansion coefficient and elastic modulus fall within the range of combinations of thermal expansion coefficient and elastic modulus calculated by the material selection assisting device 10. For example, a recommended motherboard core presented by the material selection assisting device 10 is selected.

[0056] Next, the manufacturing method includes laminating a prepreg with copper foil to the selected motherboard core 104 and etching the copper foil to form the circuitry 106 .

[0057] This makes it possible to produce a motherboard 102 with highly reliable solder 120 joints.

[0058] In addition, for steps other than the step of selecting a motherboard core 104 whose thermal expansion coefficient and elastic modulus fall within the range of combinations of thermal expansion coefficient and elastic modulus calculated by the material selection assistance device 10 described above, the same steps as those in existing motherboard manufacturing methods may be applied, and detailed explanations will be omitted.

[0059] <Circuit Board Core and Circuit Board> As a result of research into the range of physical properties of the motherboard core 104 calculated by the material selection assisting device 10, it was found that good reliability (1,000 or more life cycles) can be achieved by setting the elastic modulus E and thermal expansion coefficient α of the motherboard core 104 to E≦(6×α−35) GPa. It was also found that good reliability (1,000 or more life cycles) can be achieved by setting E≧(1.33×α−8.67) GPa. It was also found that a thermal expansion coefficient α of 12.5 ppm or more results in poor reliability. Furthermore, because the motherboard core 104 is made by impregnating glass cloth with resin and solidifying it, it is difficult to achieve an elastic modulus E of less than 4 GPa.

[0060] Therefore, in this embodiment, a motherboard core 104 is provided that satisfies all of these ranges, i.e., E≧4 GPa, α≦12.5 ppm / K, E≦(6×α−35) GPa, and E≧(1.33×α−8.67) GPa. Also provided is a motherboard 102 that uses the motherboard core 104 having the above characteristics.

[0061] By using the motherboard 102, it is possible to manufacture a semiconductor device in which the soldering between the substrate and the motherboard is highly reliable.

[0062] The following notes are provided regarding the above embodiment.

[0063] (Additional Item 1) A material selection assistance device including: a relationship estimation unit that estimates a correspondence relationship between a combination of a thermal expansion coefficient and an elastic modulus of a circuit board core and a combination of a thermal expansion coefficient and an elastic modulus of a circuit board using the circuit board core; a receiving unit that receives a thermal expansion coefficient of a substrate to be joined to the circuit board with solder; a reliability estimation unit that estimates the reliability of the solder when the substrate and the circuit board are joined with solder for each combination of a thermal expansion coefficient and an elastic modulus of the circuit board; and a calculation unit that calculates, based on the correspondence relationship, a range of combinations of a thermal expansion coefficient and an elastic modulus of the circuit board core that correspond to combinations of a thermal expansion coefficient and an elastic modulus of the circuit board that result in the reliability being equal to or greater than a predetermined value.

[0064] (Supplementary Item 2) The material selection assistance device according to Supplementary Item 1, wherein the relationship estimation unit estimates the correspondence relationship by homogenization, which estimates physical properties of a material obtained by joining the plurality of materials, based on physical properties of each of the plurality of materials.

[0065] (Supplementary Item 3) The material selection assisting device according to Supplementary Item 1 or Supplementary Item 2, wherein the reliability estimation unit estimates the reliability of the solder for each combination of the thermal expansion coefficient and elastic modulus of the circuit board based on the physical properties of the substrate, including the thermal expansion coefficient, and the physical properties of the circuit board, including the thermal expansion coefficient and elastic modulus, received by the receiving unit; and the calculation unit identifies a range surrounded by contour lines indicating a predetermined value of reliability in a space having two axes defined by the thermal expansion coefficient and elastic modulus of the circuit board, as the range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board for which the reliability is equal to or greater than the predetermined value.

[0066] (Supplementary Item 4) The material selection assistance device according to Supplementary Item 3, wherein the calculation unit converts the identified range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board into the range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board core based on the correspondence relationship.

[0067] (Supplementary Item 5) A material selection support method executed by a material selection support device including a relationship estimation unit, a receiving unit, a reliability estimation unit, and a calculation unit, wherein the relationship estimation unit estimates a correspondence relationship between a combination of a thermal expansion coefficient and an elastic modulus of a circuit board core and a combination of a thermal expansion coefficient and an elastic modulus of a circuit board using the circuit board core, the receiving unit receives the thermal expansion coefficient of a substrate to be joined to the circuit board with solder, the reliability estimation unit estimates the reliability of the solder when the substrate and the circuit board are soldered together, for each combination of the thermal expansion coefficient and elastic modulus of the circuit board, and the calculation unit calculates, based on the correspondence relationship, a range of combinations of the thermal expansion coefficient and the elastic modulus of the circuit board core that corresponds to the combination of the thermal expansion coefficient and the elastic modulus of the circuit board that makes the reliability equal to or greater than a predetermined value.

[0068] (Addendum 6) A material selection support program that causes a computer to function as: a relationship estimation unit that estimates a correspondence relationship between a combination of a thermal expansion coefficient and an elastic modulus of a circuit board core and a combination of a thermal expansion coefficient and an elastic modulus of a circuit board that uses the circuit board core; a reception unit that receives a thermal expansion coefficient of a substrate to be joined to the circuit board with solder; a reliability estimation unit that estimates the reliability of the solder when the substrate and the circuit board are joined with solder for each combination of a thermal expansion coefficient and an elastic modulus of the circuit board; and a calculation unit that calculates, based on the correspondence relationship, a range of combinations of a thermal expansion coefficient and an elastic modulus of the circuit board core that correspond to combinations of a thermal expansion coefficient and an elastic modulus of the circuit board that result in the reliability being equal to or greater than a predetermined value.

[0069] (Supplementary Item 7) A method for manufacturing a circuit board, comprising: selecting a circuit board core whose thermal expansion coefficient and elastic modulus are within a range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board core calculated by the material selection assistance device described in any one of Supplementary Items 1 to 4; laminating a prepreg with copper foil on the selected circuit board core; and etching the copper foil to form a circuit.

[0070] (Supplementary Item 8) A circuit board core used for a circuit board on which a semiconductor package is mounted, the circuit package including a substrate having a 25 mm square chip with a thickness of 0.725 mm and a 1.5 mm thick copper heat spreader mounted thereon, the substrate having a circuit layer configuration of 5-2-5, a size of 60 mm square, and a core base material with a thickness of 0.8 mm, wherein, based on the range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board core calculated by the material selection assisting device described in any one of Supplementary Items 1 to 4, the elastic modulus E and the thermal expansion coefficient α satisfy the following: E≧4 GPa, α≦12.5 ppm / K, E≦(6×α−35) GPa, and E≧(1.33×α−8.67) GPa.

[0071] (Additional Item 9) A circuit board obtained by laminating a prepreg with copper foil on the circuit board core according to Additional Item 8, and etching the copper foil to form a circuit.

[0072] REFERENCE SIGNS LIST 10 Material selection support device 12 CPU 14 Memory 16 Storage device 18 Input device 20 Output device 22 Storage medium reading device 24 Communication I / F 26 Bus 32 Relationship estimation unit 34 Reception unit 36 ​​Reliability estimation unit 38 Calculation unit 40 Presentation unit 60 Recommended material screen 62 First display area 64 Second display area 66 Third display area 100 Semiconductor device 102 Motherboard 104 Motherboard core 106 Circuit 110 Semiconductor package 112 Substrate 114 Chip 116 Heat spreader

Claims

1. A material selection support device comprising: a relationship estimation unit that estimates a correspondence relationship between a combination of a thermal expansion coefficient and elastic modulus of a circuit board core and a combination of a thermal expansion coefficient and elastic modulus of a circuit board using the circuit board core; a receiving unit that receives a thermal expansion coefficient of a substrate to be soldered to the circuit board; a reliability estimation unit that estimates the reliability of the solder when the substrate and the circuit board are soldered to each other for each combination of a thermal expansion coefficient and elastic modulus of the circuit board; and a calculation unit that calculates, based on the correspondence relationship, a range of combinations of a thermal expansion coefficient and elastic modulus of the circuit board core that correspond to the combinations of a thermal expansion coefficient and elastic modulus of the circuit board that provide a predetermined value or more of reliability.

2. The material selection assistance device according to claim 1, wherein the relationship estimation unit estimates the correspondence relationship by homogenization, which estimates the physical properties of a material obtained by joining a plurality of materials based on the physical properties of each of the plurality of materials.

3. The material selection assistance device of claim 1 or 2, wherein the reliability estimation unit estimates the life of the solder for each combination of the thermal expansion coefficient and elastic modulus of the circuit board as the reliability based on the physical properties of the substrate received by the receiving unit, including the thermal expansion coefficient, and the physical properties of the circuit board, including the thermal expansion coefficient and elastic modulus, and the calculation unit identifies a range surrounded by contour lines indicating the predetermined value of reliability in a space with the thermal expansion coefficient and elastic modulus of the circuit board as the two axes, in which the reliability is expressed by contour lines connecting points having the same degree of reliability, as the range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board in which the reliability is equal to or greater than the predetermined value.

4. The material selection support device of claim 3, wherein the calculation unit converts the identified range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board into the range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board core based on the correspondence relationship.

5. A method for manufacturing a circuit board, comprising: selecting a circuit board core whose thermal expansion coefficient and elastic modulus are within the range of the combination of the thermal expansion coefficient and elastic modulus of the circuit board core calculated by the material selection support device described in claim 1 or 2; laminating a prepreg with copper foil on the selected circuit board core; and etching the copper foil to form a circuit.

6. A circuit board core used for a circuit board mounting a semiconductor package including a substrate having a chip that is 25 mm square and 0.725 mm thick, a heat spreader made of copper and 1.5 mm thick, a circuit layer structure of 5-2-5, a circuit board layer structure of 60 mm square, and a core base material of 0.8 mm thick, wherein the elastic modulus E and the thermal expansion coefficient α satisfy E≧4 GPa, α≦12.5 ppm / K, E≦(6×α-35) GPa, and E≧(1.33×α-8.67) GPa based on the range of combinations of the thermal expansion coefficient and elastic modulus of the circuit board core calculated by the material selection assistance device according to claim 1 or 2.

7. A circuit board in which a prepreg with copper foil is laminated on the circuit board core according to claim 6, and a circuit is formed by etching the copper foil.

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