Substrate bonding jig, substrate bonding system, and substrate bonding method

Abstract

To avoid contact between adjacent solder bumps at a center portion of a second substrate when a standoff member is disposed between a first substrate and the second substrate to be bonded to each other by the solder bumps to perform reflow.SOLUTION: A first substrate has a through-hole which is provided on an outer peripheral portion of the first substrate so as to penetrate through the first substrate in a thickness direction and into which a standoff member is mounted so as to be freely movable up and down, and a second substrate faces the first substrate and is arranged such that the outer peripheral portion can be supported by the standoff member. A substrate boding jig includes a mount portion on which the first substrate is placed when the first substrate is reflow-bonded to the second substrate via a plurality of adjacent solder bumps at least at a center portion of the first substrate and a center portion of the second substrate, and a push-up mechanism that is provided below the first substrate corresponding to a mount position of the standoff member attached to the first substrate placed on the mount portion, and deforms due to the temperature rise during the reflow bonding to push up the standoff member.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a substrate bonding jig, a substrate bonding system, and a substrate bonding method. [Background technology]

[0002] Conventionally, there have been proposals for maintaining an appropriate distance between a substrate and a flip chip IC (Integrated Circuit) when the flip chip IC is mounted on a substrate via solder bumps (see, for example, Patent Document 1). Patent Document 1 proposes maintaining the distance between the substrate and the flip chip IC by a control spacer having a pin that can be inserted into and removed from an engagement hole provided in the substrate, and a bimetal convex portion. The bimetal convex portion is provided on a base of the control spacer provided with a pin, and is disposed between the base and the lower surface of the substrate. The bimetal convex portion is deformed by a temperature rise caused by reflow, narrowing the distance between the base and the substrate. The flip chip IC is supported by the pin provided on the control spacer, and the substrate is lowered relative to the flip chip IC as the bimetal convex portion is deformed. This adjusts the distance between the flip chip IC and the substrate. It is considered that such a proposal can also be applied to an electronic device having a package substrate and a system board.

[0003] Also, an electronic device has been proposed in which a standoff member is disposed between a package substrate and a system board that is joined to the package substrate via bumps (see, for example, Patent Document 2). The standoff member remains between the package substrate and the system board even after reflow. A load may be applied to the package substrate when a heat sink is mounted, for example, but the placement of the standoff member makes it possible to maintain the distance between the package substrate and the system board. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-232202 [Patent Document 2] JP 2006-237369 A Summary of the Invention [Problem to be solved by the invention]

[0005] It is known that warping occurs in package substrates that are joined to a system board by solder bumps. Before and after reflow, that is, in package substrates where there is no increase in temperature due to reflow, warping occurs in a form in which the center of the substrate moves away from the system board. In contrast, in package substrates where the temperature has increased due to reflow, warping occurs in a form in which the center of the substrate moves closer to the system board. For this reason, there is a possibility that solder bumps provided in the center of the package substrate may come into contact with each other during reflow, causing a short circuit.

[0006] The proposal disclosed in Patent Document 2 does not take measures against warping of the package substrate during reflow. As a result, there is a possibility that the solder bumps provided in the center of the package substrate will come into contact with each other during reflow, causing a short circuit. On the other hand, if the proposal disclosed in Patent Document 1 is applied to an electronic device equipped with a package substrate and a system board, it is expected that the gap between the package substrate and the system board will be narrowed because no standoff members are provided.

[0007] In one aspect, the proposal disclosed in this specification aims to avoid contact between adjacent solder bumps in the center of the second substrate when a standoff member is placed between a first substrate and a second substrate joined by solder bumps and reflow is performed. [Means for solving the problem]

[0008] One aspect is a substrate joining jig comprising: a mounting portion on which a first substrate is placed when a first substrate having a through hole penetrating in the thickness direction and provided on its outer periphery, into which a stand-off member is attached so that it can be raised and lowered, and a second substrate facing the first substrate and positioned so that its outer periphery can be supported by the stand-off member, are reflow joined via a plurality of adjacent solder bumps at least at the center of the first substrate and the center of the second substrate; and a push-up mechanism that is provided below the first substrate in correspondence with the mounting position of the stand-off member attached to the first substrate placed on the mounting portion, and that deforms due to the rise in temperature during the reflow joining to push up the stand-off member.

[0009] Another aspect is a substrate bonding system including: a first substrate having a through hole at its outer periphery that penetrates the substrate in the thickness direction and into which a stand-off member is attached so that it can be raised and lowered; a second substrate arranged opposite the first substrate, with the stand-off member and a plurality of solder bumps arranged adjacent to each other at least at the center of the surface facing the first substrate arranged between the first substrate and the second substrate; and a substrate bonding jig that includes a mounting portion that supports the first substrate when the first substrate and the second substrate are reflow-bonded via the plurality of solder bumps adjacent to each other at least at the center of the first substrate and the center of the second substrate, and that includes a push-up mechanism that pushes up the stand-off member inserted into the through hole as the temperature rises during reflow.

[0010] Yet another aspect is a substrate bonding method including the steps of: placing a first substrate, the first substrate having a through hole penetrating the first substrate in a thickness direction and into which a standoff member is attached, on a mounting portion of a substrate bonding jig; placing a second substrate, the second substrate having the standoff member and a plurality of solder bumps disposed adjacent to at least the center of the surface facing the first substrate, between the first substrate and the second substrate; placing a push-up mechanism, which is provided in the substrate bonding jig and pushes up the standoff member, below the standoff member; and subjecting the first substrate placed on the mounting portion and the second substrate disposed opposite the first substrate to reflow, and operating the push-up mechanism to push up the standoff member. Effect of the Invention

[0011] According to the proposal disclosed in this specification, when a standoff member is placed between a first substrate and a second substrate joined by solder bumps and reflow is performed, contact between adjacent solder bumps in the center of the second substrate can be avoided. [Brief description of the drawings]

[0012] [Figure 1] Fig. 1(A) is a plan view of an electronic device to which substrates have been bonded by the substrate bonding system of the first embodiment, and Fig. 1(B) is a side view of the electronic device shown in Fig. 1(A). [Diagram 2] FIG. 2 is a cross-sectional view showing the state before reflow bonding of a system board, in which electronic components having package substrates are arranged opposite each other and which is placed in a substrate bonding jig, taken along a cutting line corresponding to the AA diagram in FIG. 1(A) in the first embodiment. [Diagram 3] FIG. 3(A) is a perspective view of a stand-off member lifting mechanism provided in the substrate joining jig of the first embodiment, and FIG. 3(B) is a cross-sectional view of the stand-off member lifting mechanism taken along line BB in FIG. 3(A). [Figure 4] FIG. 4 is an exploded perspective view of the stand-off member lifting mechanism. [Diagram 5] FIG. 5 is a time chart illustrating the change in the atmospheric temperature during reflow bonding. [Figure 6] FIG. 6 is a cross-sectional view taken along the line AA in FIG. 1(A) and showing a state of the system board that has been placed on the board joining jig of the first embodiment and has been reflow-joined to electronic components. [Figure 7] FIG. 7 is a cross-sectional view taken along the line AA in FIG. 1(A) and showing the state of the system board placed on the board bonding jig of the first embodiment and cooling down during reflow bonding with electronic components. [Figure 8]Fig. 8(A) is a cross-sectional view showing the state of the stand-off member lifting mechanism of the first embodiment before reflow bonding, Fig. 8(B) is a cross-sectional view showing the state of the stand-off member lifting mechanism of the first embodiment during reflow bonding, and Fig. 8(C) is a cross-sectional view showing the state of the stand-off member lifting mechanism of the first embodiment when the temperature is decreasing during reflow bonding. [Figure 9] FIG. 9 is a cross-sectional view showing the state before reflow bonding of a system board, in which electronic components having package substrates are arranged opposite each other and which is placed in a substrate bonding jig, in the second embodiment, taken along the cutting line corresponding to the AA diagram in FIG. 1(A). [Figure 10] 10(A) is a perspective view of a stand-off member lifting mechanism provided in a substrate joining jig of the second embodiment, and FIG. 10(B) is a cross-sectional view of the stand-off member lifting mechanism taken along line B'-B' in FIG. 10(A). [Figure 11] FIG. 11 is a cross-sectional view taken along the line AA in FIG. 1(A) and showing a state of a system board that has been placed on the board joining jig of the second embodiment and has electronic components joined by reflow bonding. [Figure 12] FIG. 12 is a cross-sectional view taken along the line AA in FIG. 1(A) and showing the state of a system board placed on the board bonding jig of the second embodiment and cooling down during reflow bonding with electronic components. [Figure 13] Fig. 13(A) is a cross-sectional view showing the state of the stand-off member lifting mechanism of the second embodiment before reflow bonding, Fig. 13(B) is a cross-sectional view showing the state of the stand-off member lifting mechanism of the second embodiment during reflow bonding, and Fig. 13(C) is a cross-sectional view showing the state of the stand-off member lifting mechanism of the second embodiment when the temperature is decreasing during reflow bonding. [Figure 14] FIG. 14 is a cross-sectional view showing a state before reflow bonding of a system board, in which electronic components having package substrates are arranged opposite each other and which is placed on a substrate bonding jig, taken along a cutting line corresponding to the AA diagram in FIG. 1(A) in the third embodiment. [Figure 15]FIG. 15 is a cross-sectional view taken along the line AA in FIG. 1(A) and showing a state of a system board that has been placed on the board bonding jig of the third embodiment and has electronic components bonded thereto by reflow bonding. [Figure 16] FIG. 16 is a cross-sectional view showing a state before reflow bonding of a system board, in which electronic components having package substrates are arranged opposite each other and which is placed on a substrate bonding jig, taken along a cutting line corresponding to the AA diagram in FIG. 1(A) in the fourth embodiment. [Figure 17] FIG. 17 is a cross-sectional view taken along the line AA in FIG. 1(A) and showing a state of a system board that has been placed on the board joining jig of the fourth embodiment and has electronic components joined by reflow bonding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. However, in the drawings, the dimensions, ratios, etc. of each part may not be illustrated to be completely consistent with the actual ones. In addition, in some drawings, for the convenience of explanation, components that actually exist may be omitted, or dimensions may be exaggerated compared to the actual ones.

[0014] (First embodiment) A substrate bonding system 100 according to a first embodiment will be described with reference to FIGS. 1(A) to 8. FIG.

[0015] [Substrate bonding system] 2, the board bonding system 100 includes a system board 10, an electronic component 30 which is a semiconductor device, and a board bonding jig 50. The board bonding system 100 uses the board bonding jig 50 to bond the system board 10 and a package substrate 31 included in the electronic component 30 via solder bumps 33. The system board 10 corresponds to a first substrate, and the package substrate 31 corresponds to a second substrate.

[0016] <Electronic equipment> A substrate bonding system 100 bonds a package substrate 31 of an electronic component 30 to a system board 10 to form an electronic device 1 (see FIGS. 1(A) and 1(B)). The electronic device 1 of this embodiment is rectangular in plan view, and the system board 10 and the package substrate 31 are connected via a plurality of solder bumps 33. The solder bumps 33 are arranged in a matrix to achieve BGA (Ball Grid Array) mounting. A standoff mechanism 20 is disposed between the system board 10 and the package substrate 31. The standoff mechanism 20 includes standoff members 21 arranged at the four corners of the package substrate 31.

[0017] <System board (first board)> The system board 10 has through holes 11 penetrating in the thickness direction, that is, in the Z direction shown in FIG. 1B, at positions corresponding to the four corners of the package substrate 31. The through holes 11 are provided in the outer peripheral portion 15 of the system board 10. Here, the outer peripheral portion 15 of the system board 10 refers to the region from the outer edge of the region where the solder bumps 33 are provided to the outer edge of the package substrate 31, as shown in FIG. 1A. A standoff member 21 is attached to each through hole 11. The surface of the system board 10 facing the package substrate 31 has two countersunk portions 14. Between the two countersunk portions 14, a central portion 13 is formed in which a plurality of solder bumps 33 are adjacently arranged. In this embodiment, the central portion 13 and the two countersunk portions 14 are provided in parallel along the X direction, but the central portion 13 and the two countersunk portions 14 may be provided in parallel in the Y direction.

[0018] As will be described in detail later, the package substrate 31 bonded to the system board 10 may warp due to temperature changes accompanying reflow bonding. The central portion 13 is a region including a point opposite to the lowest point of the package substrate 31 where warping occurs during reflow bonding. The central portion 13 is a region where adjacent solder bumps 33 may come into contact with each other due to warping of the package substrate 31, resulting in a short circuit, if reflow bonding is performed without taking any measures. Therefore, the central portion 13 is not a region whose scope is strictly defined.

[0019] A plurality of electrode pads 12 in contact with solder bumps 33 are provided on the surface of the system board 10 facing the package substrate 31 .

[0020] <Electronic components (semiconductor devices)> The electronic component 30 includes a package substrate 31, a CPU (Central Processing Unit) 32a, which is a chip component mounted on the package substrate 31, and a capacitor 32b. The electronic component 30 also includes a plurality of solder bumps 33 on a surface facing the system board 10. The electronic component 30 also includes a lid 34 that covers the mounting surface on which the CPU 32a is mounted. The lid 34 is made of a material with excellent thermal conductivity. In this embodiment, the lid 34 is made of copper. Instead of the lid 34, a frame-shaped member for protecting the CPU 32a may be attached.

[0021] The electronic component 30 of this embodiment includes two CPUs 32a. The CPUs 32a are mounted on the surface of the package substrate 31 opposite to the surface facing the system board 10. The capacitors 32b function as a noise countermeasure for the CPUs 32a, and are disposed on the rear surface of the CPUs 32a. That is, the capacitors 32b are disposed on the surface facing the system board 10. The recessed portion 14 provided on the system board 10 is provided corresponding to the position where the capacitors 32b are disposed so that the capacitors 32b do not come into contact with the system board 10. The CPUs 32a are an example of an LSI (Large Scale Integration), and the electronic component 30 may be provided with an LSI other than the CPUs 32a.

[0022] When the package substrate 31 faces the system board 10, the area facing the central portion 13 of the system board 10 becomes the central portion of the package substrate 31. When the package substrate 31 faces the system board 10, the area facing the peripheral portion 15 of the system board 10 becomes the peripheral portion of the package substrate 31.

[0023] (Warpage of package substrate) Here, the warping of the package substrate 31 will be described. As described above, the CPU 32a is mounted on one surface of the package substrate 31 (the upper surface of the package substrate 31). The CPU 32a is reflow-bonded to the mounting surface of the package substrate 31 by soldering. When the temperature is raised during reflow bonding, it is assumed that the thermal expansion amounts of the one surface of the package substrate 31 and the other surface, which is the reverse side of the one surface, are approximately equal. For this reason, it is considered that the package substrate 31 does not warp when the temperature is raised during reflow bonding. However, when the temperature of the package substrate 31 starts to decrease, the surface on which the CPU 32a is mounted is constrained by the CPU 32a in a state in which it has expanded due to the temperature rise. This is due to the difference between the linear expansion coefficient of the package substrate 31 and the linear expansion coefficient of the CPU 32a, which is a silicon wafer. In contrast, the contraction of the surface opposite to the surface on which the CPU 32a is mounted is not constrained by the CPU 32a. In other words, the contraction amount of the package substrate 31 differs between the one surface side and the other surface side. As a result, the package substrate 31 to which the CPU 32a is reflow-bonded is warped such that the surface on which the CPU 32a is mounted is convex. A lid 34 is attached to the CPU 32a-mounted surface of the warped package substrate 31. The lid 34 in this embodiment is bonded to the package substrate 31. In the following description, the form of warping in which the surface on which the CPU 32a is mounted is convex, as shown in Figs. 2 and 7, is referred to as a first warping form.

[0024] In such a package substrate 31, a change in the manner of warping occurs due to a rise in temperature accompanying reflow bonding with the system board 10. This is due to the difference between the linear expansion coefficient of the package substrate 31 and the linear expansion coefficient of the lid 34. The linear expansion coefficient of the package substrate 31 is greater than that of the lid 34. Therefore, when the temperature of the package substrate 31 on which the lid 34 is attached rises, the expansion of the surface of the package substrate 31 on which the lid 34 is attached is restricted. On the other hand, the expansion of the surface of the package substrate 31 opposite to the surface on which the lid is attached is not restricted. As a result, the amount of thermal expansion of the surface side facing the system board 10 becomes greater than the amount of thermal expansion of the surface side on which the lid 34 is attached. As a result, the package substrate 31 is warped such that the surface side facing the system board 10 (the lower surface side of the package substrate 31) becomes convex. Due to the occurrence of such warping, the center of the package substrate 31 approaches the center portion 13 of the system board 10. For this reason, if reflow bonding is performed without taking any measures, adjacent solder bumps 33 may come into contact with each other in the center portion 13, causing a short circuit. In the following description, the warpage form in which the surface facing the system board 10 is convex as shown in Fig. 6 will be referred to as the second warpage form.

[0025] When the reflow bonding transitions to the temperature decreasing period, the package substrate 31 returns to the first warpage state.

[0026] <Standoff component> As shown in an enlarged view in FIG. 2, the standoff member 21 includes a standoff portion 21a and a pin-shaped insertion portion 21b connected to the standoff portion 21a. The diameter of the standoff portion 21a is larger than the diameter of the insertion portion 21b. The standoff member 21 is provided in such a manner that the insertion portion 21b is inserted into the through hole 11 and the standoff portion 21a is disposed between the system board 10 and the package substrate 31. The lower end portion 21b1 of the insertion portion 21b is located below the lower opening 11a of the through hole 11. In other words, the standoff member 21 is installed on the system board 10 with the insertion portion 21b protruding through the through hole 11. The standoff member 21 is provided at the four corners of the package substrate 31 as shown in FIG. 1(A). The insertion portion 21b of each standoff member 21 is loosely fitted into the through hole 11 so as to be freely raised and lowered relative to the through hole 11.

[0027] <Board Joining Jig> The board joining jig (hereinafter simply referred to as the "jig") 50 can prevent the solder bumps 33 from contacting each other in the central portion 13 when reflow joining the system board 10 and the package substrate 31 via the solder bumps 33. The jig 50 includes a bottom plate portion 51, a side plate portion 52, and a mounting portion 53. A stand-off member lifting mechanism 60 is provided on the bottom plate portion 51. A stand-off member lifting mechanism 60 is provided for each stand-off member 21. Although not shown in the figure, the bottom plate portion 51 is rectangular in shape roughly similar to the external shape of the electronic device 1, and the side plate portions 52 are provided on its four sides.

[0028] <Placement section> The mounting portion 53 is a portion on which the system board 10 is positioned and mounted. The mounting portion 53 includes a support plate 53a extending from the upper edge of the side plate portion 52 toward the center. The mounting portion 53 includes a positioning portion 53b provided on the support plate 53a. The system board 10 is supported by the support plate 53a, and its position in the X and Y directions is determined by the positioning portion 53b.

[0029] <Standoff component lifting mechanism> The standoff member lifting mechanism (hereinafter simply referred to as the “lifting mechanism”) 60 has a function as a push-up mechanism that pushes up the standoff member 21, and a function as an elastic support part.

[0030] 3A to 4, the lifting mechanism 60 includes a housing 61, a spring member 63, a bimetal part 64, and a cover part 65. The lifting mechanism 60 includes a housing 61, a spring member 63, a bimetal part 64, and a cover part 65.

[0031] The housing 61 has a screw hole 61a for fixing the cover portion 65 with a screw 67. The housing 61 has a screw hole 61b for fixing to the bottom plate portion 51 with a screw 66. The housing 61 has a storage recess 62 for storing the spring member 63 and the bimetal portion 64.

[0032] The spring members 63 correspond to elastic support members. The spring members 63 are arranged in pairs below the bimetal portion 64 and support the bimetal portion 64 from below. In this embodiment, the spring members 63 are provided at four locations. The four spring members 63 support the weight of the electronic device 1. That is, the pair of spring members 63 supports one-fourth of the weight of the electronic device 1. Furthermore, each pair of spring members 63 supports the weight of the bimetal portion 64 that it supports. When the reflow bonding transitions to the temperature decreasing period, the central portion of the package substrate 31 reflow bonded to the system board 10 rises toward the side away from the system board 10 and deforms into a convex shape. Furthermore, the peripheral portion of the package substrate 31 relatively descends. Each spring member 63 elastically deforms during the process in which the package substrate 31 undergoes such deformation. That is, the spring member 63 has an elastic force that generates elastic deformation when the warping state transitions from the second warping state to the first warping state during reflow bonding.

[0033] The package substrate 31 and the system board 10 are joined by the solder bumps 33. It is considered that the molten solder bumps 33 attract the package substrate 31 and the system board 10 to each other due to their surface tension. It is considered that the package substrate 31 is constrained to the system board 10 by the surface tension exerted by the many solder bumps 33. When the package substrate 31 constrained to the system board 10 returns from the second warped form to the first warped form and the peripheral portion relatively descends, the force at that time acts on the spring member 63 via the bimetal portion 64. When the sum of such force, the weight of the electronic device 1, and the weight of the bimetal portion 64 exceeds the elastic force of the spring member 63, the spring member 63 undergoes elastic deformation. The bimetal portion 64 descends as a result of the spring member 63 undergoing elastic deformation. In other words, the spring member 63 allows the bimetal portion 64 to be pressed down by the restoring force when the warped form of the package substrate 31 is restored.

[0034] In this embodiment, a leaf spring is used, but the type of spring is not limited to this, and other types of springs may be used. Also, elastic members other than spring members may be used.

[0035] The bimetal part 64 corresponds to a push-up mechanism. The bimetal part 64 is formed by bonding together a high thermal expansion member 64a and a low thermal expansion member 64b, each of which is formed in a plate shape. The thermal expansion coefficient of the high thermal expansion member 64a only needs to be higher than that of the low thermal expansion member 64b. The bimetal part 64 is provided with a pin-shaped receiving part 64c on the high thermal expansion member 64a side. The receiving part 64c can abut against the lower end part 21b1 of the insertion part 21b of the standoff member 21.

[0036] The bimetal part 64 is stored in the storage recess 62 so that the high thermal expansion member 64a is located on the upper side and the low thermal expansion member 64b is located on the lower side. When the temperature rises due to reflow bonding, the bimetal part 64 deforms so that the high thermal expansion member 64a side becomes convex. This allows the receiving part 64c in contact with the insertion part 21b of the standoff member 21 to push up the standoff member 21 when the temperature rises due to reflow bonding. The bimetal part 64 is stored in the storage recess 62 so that the receiving part 64c is exposed from the receiving part insertion hole 65a provided in the lid part 65.

[0037] [Substrate bonding method] Next, a method for bonding the system board 10 and the package substrate 31 will be described. In the following description, the work is performed by a robot, but the process is the same when the work is performed by a worker. It is assumed that the package substrate 31 is in a state of electronic component 30 with components such as a CPU 32a and a capacitor 32b mounted in advance.

[0038] The robot places the system board 10 on the placement portion 53 of the jig 50. Then, the robot attaches the standoff members 21 to the through holes 11. Note that the standoff members 21 may be in a state of being attached before the system board 10 is placed on the placement portion 53.

[0039] The robot places the system board 10 and the package substrate 31 opposite each other. At this time, the surface of the package substrate 31 on which the solder bumps 33 are provided faces the system board 10. The process of placing the system board 10 and the package substrate 31 opposite each other may be completed before the system board 10 is placed on the placement portion 53 of the jig 50. In other words, the system board 10 with the package substrate 31 placed opposite each other may be placed on the placement portion 53.

[0040] The jig 50 is provided with a lifting mechanism 60. Therefore, by placing the system board 10 on the placement portion 53, the lifting mechanism 60 is disposed below the standoff members 21.

[0041] The system board 10 and the package substrate 31 placed on the jig 50 are placed in a reflow furnace and subjected to reflow bonding.

[0042] Here, the operating conditions and state changes of each part included in the substrate bonding system 100 will be described with reference to a time chart shown in FIG. 5, which illustrates an example of the change in the atmospheric temperature during reflow bonding.

[0043] The state in the furnace during the period from time t1 to time t2 shown in FIG. 5 is the same as room temperature. Therefore, the package substrate 31 is in a state exhibiting a first warpage mode as shown in FIG. 2. Moreover, the bimetal portion 64 is also in a flat state without warpage as shown in FIG. 8(A). The spring member 63 also supports the bimetal portion 64 without deformation. During this period, as shown in an enlarged view in FIG. 2, the stand-off portion 21a of the stand-off member 21 is not in contact with the lower surface of the package substrate 31, and a gap is generated between them. Moreover, a gap is generated between the lower end portion 21b1 of the insertion portion 21b of the stand-off member 21 and the receiving portion 64c.

[0044] 5 is a period in which the temperature inside the furnace rises and the temperature of the package substrate 31 gradually rises. The period in which the temperature inside the furnace remains constant from time t3 to time t4 in Fig. 5 is a period in which the temperature inside the furnace remains constant. Until time t4, the melting point of the solder bumps 33 is not reached and no change is observed in the state of the package substrate 31 or the bimetal portion 64.

[0045] During the period from time t4 to time t5 in FIG. 5, the temperature in the furnace further rises, and the solder bumps 33 begin to melt. During this period, the warpage of the package substrate 31 begins to change from the first warpage and transitions to a substantially flat state where no warpage occurs. Meanwhile, the bimetal portion 64 gradually deforms, and as shown in FIG. 8(B), the high thermal expansion member 64a side deforms to a convex shape, and the receiving portion 64c moves upward. As a result, the receiving portion 64c comes into contact with the lower end portion 21b1 of the insertion portion 21b of the standoff member 21, and pushes up the standoff member 21. The pushed-up standoff member 21 comes into contact with the lower surface of the package substrate 31, and pushes up the package substrate 31. The receiving portion 64c rises until it comes into contact with the system board 10.

[0046] The period from time t5 to time t6 in FIG. 5 is a period during which the temperature inside the furnace is at the set peak temperature. During this period, as shown in FIG. 6, the warpage of the package substrate 31 transitions to the second warpage. That is, the package substrate 31 warps convexly toward the surface facing the system board 10. As a result, the center of the package substrate 31 approaches the center 13 of the system board 10. During this period, each lifting mechanism 60 pushes up the standoff member 21, and in turn pushes up the package substrate 31, moving it away from the system board 10. Therefore, even if the package substrate 31 transitions to the second warpage, the adjacently arranged solder bumps 33 are not crushed in the center 13 of the system board 10. As a result, contact and short circuit between adjacently arranged solder bumps 33 are avoided.

[0047] The period from time t6 to time t7 in FIG. 5 is a temperature drop period. During this period, the solder bumps 33 gradually solidify. At this time, it is desirable that the stand-off member 21 is lowered. When the package substrate 31 is in the second warpage state, the stand-off member 21 pushes up the package substrate 31 to prevent the solder bumps 33 from contacting each other in the central portion 13 of the system board 10. The package substrate 31 returns from the second warpage state to the first warpage state as shown in FIG. 7 by lowering the temperature. Therefore, even if the package substrate 31 returns to the first warpage state, if the stand-off member 21 remains pushed up, the solder bumps 33 may solidify in a state stretched in the vertical direction (Z direction). The solder bumps 33 in the stretched state are more likely to be damaged and broken. In particular, the solder bumps 33 in the vicinity of the stand-off member 21 are likely to be stretched. Therefore, it is desirable that the standoff members 21 are lowered when the solder bumps 33 harden.

[0048] Therefore, in this embodiment, a spring member 63 is provided as an elastic support member. The spring member 63 can lower the standoff member 21 even when the bimetal portion 64 has not yet returned to the flat state. As shown in FIG. 8C, the spring member 63 is elastically deformed by a restoring force that restores the package substrate 31 from the second warped state to the first warped state. As a result, the bimetal portion 64 is in a state in which it has moved downward as shown in FIG. 7. As a result, the standoff member 21 descends even when the bimetal portion 64 has not yet returned to the flat state. As a result, the solder bump 33 is prevented from solidifying in an elongated state.

[0049] Through the above steps, the electronic device 1 shown in Fig. 1(A) and Fig. 2(B) can be obtained. The electronic device 1 may have a cooling device such as a heat sink mounted on the lid 34. In the electronic device 1 of this embodiment, the stand-off member 21 is disposed as is. Therefore, even if a cooling device or the like is mounted, the electronic device 1 has the strength to withstand the weight of the cooling device or the like.

[0050] This embodiment includes a bimetal portion 64. This makes it possible to prevent the solder bumps 33 arranged adjacent to each other in the central portion 13 of the system board 10 from coming into contact with each other when the package substrate 31 takes the second warping form due to a temperature rise caused by reflow bonding.

[0051] Furthermore, this embodiment includes a spring member 63. This allows the standoff member 21 to be lowered even when the bimetal portion 64 has not yet returned to its flat state.

[0052] Second embodiment Next, a second embodiment will be described with reference to Fig. 9 to Fig. 13(C). A substrate bonding system 200 of the second embodiment includes a jig 150 instead of the jig 50 in the substrate bonding system 100 of the first embodiment. The jig 150 includes a lifting mechanism 160 including a thermal expansion member 164 instead of the lifting mechanism 60 including a bimetal portion 64. Components common to the components in the first embodiment are given the same reference numbers in the drawings. In the following description, detailed descriptions of the common components are omitted.

[0053] The thermal expansion member 164 is made of a material that expands in volume due to a temperature rise caused by reflow bonding. In this embodiment, it is made of PTFE (polytetrafluoroethylene). The material of the thermal expansion member 164 may be any other material known in the art, as long as it has the property of expanding in volume due to a temperature rise.

[0054] 10(B), the thermal expansion member 164 is provided with a spring member 163 instead of the spring member 63. The elastic force of the spring member 163 is set from the same viewpoint as the spring member 63. In other words, the elastic force of the spring member 163 is set so as to allow the thermal expansion member 164 to be pressed down by the restoring force when the warped form of the package substrate 31 is restored. Note that while the spring members 63 in the first embodiment are provided in pairs, in this embodiment, one spring member 163 is provided for one thermal expansion member 164. Therefore, the elastic force of the spring member 163 is appropriately set taking this into consideration.

[0055] The package substrate 31 in the substrate bonding system 200 at room temperature before the temperature is increased for reflow bonding is in a first warpage state as shown in Fig. 9. The thermal expansion member 164 is not thermally expanded as shown in Fig. 13(A). The spring member 163 is not elastically deformed either.

[0056] In contrast, the package substrate 31 in the substrate bonding system 200, whose temperature has risen due to reflow bonding, transitions to a second warpage state as shown in FIG. 11. At this time, the thermal expansion member 164 thermally expands as shown in FIG. 13(B). In FIG. 13(B), the thermal expansion portion 164a is shown by thin hatching. As a result, the thermal expansion member 164 pushes up the standoff member 21, and in turn, pushes up the package substrate 31. This prevents the solder bumps 33 adjacently arranged in the center portion 13 of the system board 10 from contacting each other. At this point in time, the spring member 163 is not elastically deformed.

[0057] When the substrate bonding system 200 is in a temperature decreasing state, the package substrate 31 returns from the second warped state to the first warped state as shown in FIG. 12. At this time, the thermal expansion member 164 maintains the thermally expanded state. However, the spring member 163 is elastically deformed by a restoring force that restores the package substrate 31 from the second warped state to the first warped state. As a result, the thermal expansion member 164 moves downward as shown in FIG. 13(C). As a result, even when the thermal expansion member 164 maintains the thermally expanded state, the standoff member 21 moves downward. As a result, the solder bump 33 is prevented from solidifying in an extended state.

[0058] In this manner, the substrate bonding system 200 of the second embodiment can also provide the same effects as those of the substrate bonding system 100 of the first embodiment.

[0059] Third embodiment Next, a third embodiment will be described with reference to Figs. 14 and 15. In Figs. 14 and 15, only the mounting portion 53 and the bimetal portion 64 are depicted as a jig. The third embodiment differs from the first embodiment in that the bimetal portion 64 has an insertion pin portion 64c1 extending along the Z direction in the receiving portion 64c. The insertion pin portion 64c1 is inserted into a through hole 11 provided in the system board 10. Accordingly, the standoff member 21 in the eleventh embodiment is changed to a standoff member 221.

[0060] The standoff member 221 includes a standoff portion 221a and an insertion portion 221b, similar to the standoff member 21. However, the length of the insertion portion 221b is shorter than the length of the insertion portion 21b. Therefore, the lower end portion 221b1 of the insertion portion 221b remains in the through hole 11 when the insertion portion 221b is attached to the through hole 11. As a result, the bimetal portion 64 pushes up the package substrate 31 with the insertion pin portion 64c1 and the insertion portion 221b in contact with each other in the through hole 11. The contact between the insertion pin portion 64c1 and the insertion portion 221b in the through hole 11 prevents the receiving portion 64c from contacting the system board 10.

[0061] By preventing contact between the receiving portion 64c and the system board 10, the effect of an error in the thickness of the system board 10 on the amount of lift of the standoff member 221 can be mitigated.

[0062] In the first embodiment, the lower end 21b1 of the insertion portion 21b of the standoff member 21 protrudes from the lower opening 11a of the through hole 11. The amount by which the insertion portion 21b protrudes from the lower opening 11a is affected by the thickness of the system board 10. That is, as the thickness of the system board 10 increases, the amount by which the insertion portion 21b protrudes from the lower opening 11a decreases. In the first embodiment, the receiving portion 64c that pushes up the standoff member 21 abuts against the lower surface of the system board 10. Therefore, if the amount by which the insertion portion 21b protrudes decreases, the amount by which the standoff member 21 is pushed up also decreases. The thickness of the system board 10 has a manufacturing error. Therefore, the manufacturing error affects the amount by which the standoff member 21 is pushed up, and thus also affects the distance between the system board 10 and the package substrate 31.

[0063] Therefore, in this embodiment, an insertion pin portion 64c1 is provided on the bimetal portion 64, and the insertion pin portion 64c1 and the insertion portion 221b are brought into contact with each other inside the through hole 11. This reduces the effect of an error in the thickness of the system board 10 on the amount of push-up of the stand-off member 221, and makes it possible to stabilize the amount of push-up.

[0064] (Fourth embodiment) Next, a fourth embodiment will be described with reference to Figs. 16 and 17. In Figs. 16 and 17, only the mounting portion 53 and the thermal expansion member 164 are depicted as a jig. The fourth embodiment differs from the second embodiment in that the thermal expansion member 164 has an insertion pin portion 164c extending along the Z direction at its upper portion. The insertion pin portion 164c is inserted into a through hole 11 provided in the system board 10. Accordingly, the standoff member 21 in the eleventh embodiment is changed to a standoff member 221.

[0065] The insertion pin portion 164c has the same characteristics and functions as the insertion pin portion 64c1 in the third embodiment. Therefore, detailed description of the insertion pin portion 164c is omitted. In the fourth embodiment, by providing the insertion pin portion 164c, the influence of the error in the thickness of the system board 10 on the amount of pushing up of the standoff member 221 can be mitigated, and the amount of pushing up can be stabilized.

[0066] [effect] The effects of the substrate bonding system disclosed in this specification will now be described.

[0067] The substrate bonding system disclosed in this specification includes a first substrate, a second substrate, and a jig used to bond them. The jig has a mounting portion on which the first substrate is placed when the first substrate and the second substrate are reflow bonded via solder bumps. The jig is provided below the first substrate placed on the mounting portion, and includes a push-up mechanism that is deformed by a temperature rise during reflow bonding and pushes up the stand-off member. The push-up mechanism pushes up the second substrate. This prevents contact between adjacent solder bumps at the center of the first substrate and the center of the second substrate.

[0068] The jig disclosed in this specification includes an elastic support portion that supports the push-up mechanism. The elastic support portion has an elastic force that elastically deforms when the center portion of the second substrate, which is reflow-bonded to the first substrate, rises toward the side away from the first substrate and deforms into a convex shape, and the peripheral portion of the second substrate relatively descends. The elastic deformation of the elastic support portion causes the push-up mechanism to descend. The descending of the push-up mechanism prevents the solder bumps 33 from solidifying in an elongated state.

[0069] The push-up mechanism includes an insertion pin that is inserted into the through hole. The insertion pin contacts the stand-off member in the through hole and supports the stand-off member. This makes it possible to stabilize the amount of push-up of the second substrate by mitigating the effect of the thickness of the first substrate.

[0070] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

[0071] In addition, the following supplementary notes are disclosed in relation to the above-described embodiment. (Appendix 1) a mounting portion on which the first substrate is placed when a first substrate having a through hole penetrating in a thickness direction and provided on an outer periphery thereof, and a second substrate opposed to the first substrate and arranged such that the outer periphery thereof can be supported by the stand-off member, are reflow-bonded via a plurality of adjacent solder bumps at least at a center of the first substrate and a center of the second substrate; a push-up mechanism that is provided below the first substrate in correspondence with a mounting position of the stand-off member mounted on the first substrate mounted on the mounting portion, the push-up mechanism deforming due to a temperature rise during the reflow bonding to push up the stand-off member; A substrate bonding jig equipped with the above. (Appendix 2) Further comprising an elastic support portion supporting the push-up mechanism. 2. A substrate joining jig as described in appendix 1. (Appendix 3) When a central portion of the second substrate reflow-bonded to the first substrate is elevated and deformed into a convex shape away from the first substrate, and a peripheral portion of the second substrate is relatively lowered, the elastic support portion is elastically deformed and has an elastic force that lowers the push-up mechanism. 3. A substrate joining jig as described in appendix 2. (Appendix 4) The push-up mechanism is a bimetal part that deforms as the temperature increases. 2. A substrate joining jig as described in appendix 1. (Appendix 5) The push-up mechanism includes a thermal expansion member that expands in volume as the temperature increases. 2. A substrate joining jig as described in appendix 1. (Appendix 6) the push-up mechanism includes an insertion pin portion that is inserted into the through hole, and the insertion pin portion contacts the stand-off member in the through hole and supports the stand-off portion. 2. A substrate joining jig as described in appendix 1. (Appendix 7) a first substrate having a through hole at an outer periphery thereof, the through hole penetrating the first substrate in a thickness direction and into which a standoff member is attached so as to be movable up and down; a second substrate disposed opposite the first substrate, with the stand-off member and a plurality of solder bumps disposed adjacent to each other at least at a center of a surface facing the first substrate between the second substrate and the stand-off member; a substrate joining jig including a mounting portion that supports the first substrate when the first substrate and the second substrate are reflow-joined via a plurality of adjacent solder bumps at least at a center portion of the first substrate and a center portion of the second substrate, and including a push-up mechanism that pushes up the stand-off member inserted into the through hole as the temperature rises during reflow; A substrate bonding system comprising: (Appendix 8) Further comprising an elastic support portion supporting the push-up mechanism. 8. The substrate bonding system of claim 7. (Appendix 9) the elastic support portion is elastically deformed when a central portion of the second substrate reflow-bonded to the first substrate rises toward a side away from the first substrate and deforms into a convex shape, and a peripheral portion of the second substrate relatively descends, and has an elastic force that causes the push-up mechanism to descend. 9. The substrate bonding system of claim 8. (Appendix 10) The push-up mechanism is a bimetal part that deforms as the temperature increases. 8. The substrate bonding system of claim 7. (Appendix 11) The push-up mechanism includes a thermal expansion member that expands in volume as the temperature increases. 8. The substrate bonding system of claim 7. (Appendix 12) the push-up mechanism includes an insertion pin portion that is inserted into the through hole, and the insertion pin portion contacts the stand-off member in the through hole and supports the stand-off portion. 8. The substrate bonding system of claim 7. (Appendix 13) a step of placing a first substrate having a through hole penetrating in a thickness direction and into which a standoff member is attached, on a placement portion of a substrate joining jig; a step of disposing a second substrate facing the first substrate, the second substrate having the stand-off member and a plurality of solder bumps disposed adjacent to at least a center portion of a surface facing the first substrate between the second substrate and the first substrate; a step of disposing a push-up mechanism provided on the substrate joining jig and configured to push up the stand-off member below the stand-off member; a step of subjecting a first substrate placed on the placement portion and a second substrate arranged opposite the first substrate to reflow and operating the push-up mechanism to push up the stand-off member; A method for bonding substrates comprising: (Appendix 14) The push-up mechanism is a bimetal part that deforms as the temperature increases. 14. The method of bonding substrates according to claim 13. (Appendix 15) The push-up mechanism includes a thermal expansion member that expands in volume as the temperature increases. 14. The method of bonding substrates according to claim 13. [Explanation of symbols]

[0072] 1 electronic device, 10 system board (first substrate), 11 through hole, 11a lower opening, 12 electrode pad, 13 central portion, 14 countersunk portion, 15 outer periphery, 20 standoff mechanism, 21, 221 standoff member, 21a, 221a standoff portion, 21b, 221b insertion portion, 21b1, 221b1 lower end portion, 30 electronic component, 31 package substrate, 32a CPU, 32b capacitor, 33 solder bump, 34 lid, 50, 150 jig, 53 mounting portion, 53a support plate, 53b positioning portion, 60, 160 standoff member lifting mechanism, 63, 163 spring member, 64 bimetal portion, 64c receiving portion, 64c1, 164c insertion pin portion, 164 thermal expansion member, 164a thermal expansion portion.

Claims

1. a mounting portion on which the first substrate is placed when a first substrate having a through hole penetrating in a thickness direction and provided at an outer periphery thereof, into which a stand-off member is attached so as to be capable of being raised and lowered, and a second substrate facing the first substrate and disposed such that an outer periphery thereof can be supported by the stand-off member, are reflow-bonded via a plurality of adjacent solder bumps at least at a center of the first substrate and a center of the second substrate; a push-up mechanism that is provided below the first substrate in correspondence with a mounting position of the stand-off member mounted on the first substrate mounted on the mounting portion, the push-up mechanism deforming due to a temperature rise during the reflow bonding to push up the stand-off member; A substrate bonding jig equipped with the above.

2. Further comprising an elastic support portion for supporting the push-up mechanism. The substrate joining jig according to claim 1 .

3. a central portion of the second substrate reflow-bonded to the first substrate is elevated and deformed into a convex shape away from the first substrate, and a peripheral portion of the second substrate is relatively lowered, the elastic support portion is elastically deformed and has an elastic force that lowers the push-up mechanism. The substrate joining jig according to claim 2 .

4. The push-up mechanism is a bimetal part that deforms as the temperature increases. The substrate joining jig according to claim 1 .

5. The push-up mechanism includes a thermal expansion member that expands in volume as the temperature increases. The substrate joining jig according to claim 1 .

6. the push-up mechanism includes an insertion pin portion that is inserted into the through hole, and the insertion pin portion contacts the stand-off member in the through hole and supports the stand-off portion. The substrate joining jig according to claim 1 .

7. a first substrate having a through hole at an outer periphery thereof, the through hole penetrating the first substrate in a thickness direction and into which a standoff member is attached so as to be movable up and down; a second substrate disposed opposite the first substrate, with the standoff member and a plurality of solder bumps disposed adjacent to each other at least at a center of a surface facing the first substrate between the second substrate and the standoff member; a substrate joining jig including a mounting portion that supports the first substrate when the first substrate and the second substrate are reflow-joined via a plurality of adjacent solder bumps at least at a center portion of the first substrate and a center portion of the second substrate, and including a push-up mechanism that pushes up the stand-off member inserted into the through hole as a temperature rises during reflow; A substrate bonding system comprising:

8. a step of placing a first substrate having a through hole penetrating in a thickness direction and into which a standoff member is attached, on a placement portion of a substrate joining jig; a step of disposing a second substrate facing the first substrate, the second substrate having the standoff member and a plurality of solder bumps disposed adjacent to at least a center portion of a surface facing the first substrate between the second substrate and the first substrate; a step of disposing a push-up mechanism provided on the substrate joining jig and configured to push up the stand-off member below the stand-off member; a step of subjecting a first substrate placed on the placement portion and a second substrate arranged opposite the first substrate to reflow and operating the push-up mechanism to push up the stand-off member; A method for bonding substrates comprising:

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