Manufacturing method for electronic components

Abstract

An electronic component manufacturing method is provided which involves a step for preparing a mounting substrate on which multiple bumps are provided, a step for preparing a member to be mounted that has multiple external conductor members, a step for applying a fixing member on the surface of the mounting substrate where the bumps are formed and / or the surface of the member to be mounted where the external conductor members are formed, and a step for fixing the mounting substrate and the member to be mounted with the fixing member such that the bumps and the external conductor members contact. The step for applying the fixing member involves a step in which a material containing a first main agent and a second main agent having the characteristic that the viscosity changes depending on the temperature is prepared as said fixing member, and a step in which the fixing member is applied to the mounting substrate and / or the member to be mounted at a temperature lower than a first temperature; the fixing step involves a step in which, in a state in which the temperature of the fixing member is lower than the first temperature, the mounting substrate is pressed against the member to be mounted, and a step in which the fixing member is heated to a temperature higher than a second temperature and cured.

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing an electronic component. [Background technology]

[0002] Conventionally, as disclosed in Patent Document 1, a method has been known in which a mounting substrate provided with bumps and a semiconductor chip provided with an external conductor member are attached by using a non-conductive adhesive. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5513417 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional technology, when the mounting substrate and the semiconductor chip are fixed with a non-conductive adhesive, the non-conductive adhesive remains between the bump and the external conductor member, which causes a problem in that the conductivity between the bump and the external conductor member is affected.

[0005] An object of the present invention is to improve the electrical conductivity between bumps and external conductor members in an electronic component in which a mounting substrate and a semiconductor chip are fixed together with a non-conductive adhesive. [Means for solving the problem]

[0006] According to one aspect of the present invention, a method for manufacturing a mounting substrate includes the steps of: preparing a mounting substrate having a plurality of bumps; preparing a mounted substrate having a plurality of external conductor members; applying a fastening member to one or both of the surface of the mounting substrate having the bumps and the surface of the mounted substrate having the external conductor members; and pressing the mounting substrate against the mounted substrate so that the plurality of bumps come into contact with the plurality of external conductor members, thereby fastening the mounting substrate and the mounted substrate to each other with the fastening member. The step of applying the fastening member includes preparing, as the fastening member, a material containing a first main agent and a second main agent having a property that the viscosity of the first main agent changes depending on the temperature, and the first main agent has a viscosity of the lowest second main agent at a first temperature. the first base has a first viscosity, the second base has a second lowest viscosity at a second temperature higher than the first temperature, and the adhesive member has a viscosity higher than the first and second viscosities at a third temperature lower than the first temperature and has a property of hardening at a fourth temperature higher than the second temperature; and a step of applying the adhesive member to one or both of a mounting board and a mounted member at a temperature lower than the first temperature, wherein the adhesive member is fixed to the mounting board by pressing the mounting board against the mounted member while the temperature of the adhesive member is lower than the first temperature, and by heating the adhesive member to a temperature higher than the second temperature to harden the adhesive member.

[0007] According to this embodiment, when the mounting substrate and the mounted member are fixed with the non-conductive adhesive, the amount of non-conductive adhesive remaining between the bumps and the external conductor member can be reduced, thereby providing an electronic component having sufficient conductivity between the bumps and the external conductor member. [Brief description of the drawings]

[0008] [Figure 1] 5(a) to 5(d) are longitudinal cross-sectional views showing a manufacturing process of the mounting board according to the first embodiment. [Diagram 2] 5(a) to 5(c) are longitudinal cross-sectional views illustrating a manufacturing process for the electronic component according to the first embodiment. [Diagram 3] 1(a) to 1(c) are a perspective view of an electronic component according to a first embodiment and a longitudinal sectional view of a portion thereof. [Figure 4] 11(a) to 11(d) are plan views showing variations in the positions where bumps are formed. [Diagram 5] 4(a) to (d) are longitudinal sectional views corresponding to FIG. 4(a) to (d). [Figure 6] 5(a) to 5(d) are longitudinal sectional views showing examples of bump structures. [Figure 7] 11(a) to 11(e) are vertical cross-sectional views showing a manufacturing process of a bump according to a second embodiment. [Figure 8] FIG. 11 is a plan view showing a plane pattern of a bump according to the third embodiment. [Figure 9] 13 is a diagram showing an example of the temperature-viscosity characteristics of the non-conductive adhesive 25. FIG. [Figure 10] 13 is a diagram showing an example of temperature-viscosity characteristics of multiple base agents contained in a non-conductive adhesive 25. FIG. [Figure 11] 13 is a diagram showing another example of the temperature-viscosity characteristics of the non-conductive adhesive 25. FIG. [Figure 12] 13 is a diagram showing another example of the temperature-viscosity characteristics of the non-conductive adhesive 25. FIG. [Figure 13] FIG. 13 is a diagram showing the temperature-viscosity characteristics of a non-conductive adhesive in a comparative example. [Figure 14] 10A to 10C are vertical cross-sectional views showing a manufacturing process of the mounting board according to the fourth embodiment. [Figure 15] 13 is a diagram showing an example of the cumulative distribution of the dimensions of conductive particles 51 contained in a printing ink 15x. [Figure 16] FIG. 13 is a diagram showing an example of the relationship between the size of an opening 33 in a printing plate 30 and the bump defect rate (non-conductive rate) and bump height. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 1(a) to 1(d) are longitudinal sectional views showing a manufacturing process of a mounting board B according to embodiment 1. FIGs. 2(a) to 2(c) are longitudinal sectional views showing a manufacturing process of an electronic component A according to embodiment 1. FIG 3 is a perspective view of the electronic component A according to embodiment 1 and a longitudinal sectional view of a part thereof.

[0010] Hereinafter, the manufacturing process of the mounting board B and electronic component A according to the present embodiment, as well as their structures, will be described with reference to FIGS.

[0011] [Structure and manufacturing process of mounting board] First, in the step shown in Fig. 1(a), a ceramic substrate 10, which is a base material, is prepared. Wiring 11, which is a conductive member, is formed on the upper surface of the ceramic substrate 10. The ceramic substrate 10 is a well-known multilayer substrate in which a large number of vias (plugs) 12 and wiring 11 are laminated with insulating films interposed therebetween, and a back surface electrode 13 is provided on the back surface of the ceramic substrate 10. A large number of partial regions Rn are provided in a checkerboard pattern on the ceramic substrate 10, and a mounted member such as a semiconductor chip is mounted on each partial region Rn. Figs. 1(a) to (d) show examples of the longitudinal cross-sectional structure of a portion of each partial region Rn.

[0012] The substrate is not limited to a ceramic substrate, but may be a rigid wiring substrate or a flexible substrate using an inorganic material other than ceramic or an organic resin. Also, the substrate is not limited to a multilayer wiring substrate, but may be a wiring substrate provided with only a single layer of wiring.

[0013] In this embodiment, the wiring 11 is arranged at a pitch of about 70 μm. The width of the wiring 11 is about 30 to 40 μm, and the thickness is about 5 to 10 μm. The material of the wiring 11 may be, for example, Cu, Cu alloy, Al, Al alloy, W, W alloy, Mo, Mo alloy, or the like, and any of these may be used.

[0014] 1(b), a printing plate 30 with openings only in the areas to which the ink is to be transferred is placed on the ceramic substrate 10, and a printing ink paste 15x is placed on top of the printing plate 30. A squeegee 31 is then slid over the printing plate 30 to transfer the printing ink 15x onto the ceramic substrate 10 through the openings in the printing plate 30. Generally, a conductive paste such as Ag paste (silver conductive paste) is used as the printing ink 15x, but a non-conductive paste such as a resin ink may also be used.

[0015] As a result, as shown in Fig. 1(c), the transferred printing ink 15x flows to form a mountain-shaped bump body 15a. In this example, the bump body 15a is in contact only with the wiring 11, but as described later, it is preferable that the bump body 15a is also in contact with the ceramic substrate 10. The printing ink 15x made of Ag paste is mainly composed of highly conductive silver powder and a resin binder. The curing temperature of the resin binder is, for example, about 100 to 200°C.

[0016] Next, the Ag paste is cured in this state. At this time, the bump body 15a has a structure in which Ag particles are piled up like a mountain, as shown in the partially enlarged view. Then, by curing, the bump body 15a is firmly bonded to the wiring 11 and the ceramic substrate 10.

[0017] 1(c), it is sufficient to only preliminarily harden the bump body 15a. In this case, after the chip mounting process described later, the entire bump 15 can be hardened at the same time as the process of hardening the adhesive used for mounting. In this embodiment, an epoxy resin is used as the adhesive, as described later. Therefore, when this process is adopted, a resin binder that can be hardened at a temperature lower than the thermal hardening temperature of the epoxy resin can be used for the printing ink.

[0018] Moreover, instead of the resin binder, an inorganic binder (or a mixture of an inorganic binder and a resin binder) such as glass frit that is fired at a relatively high temperature (for example, 500° C. or higher) may be used. In this case, the bump body 15a and the ceramic substrate 10 can be metallized and bonded. In this case, too, the bump body 15a can be plastically deformed by appropriately selecting the composition of the inorganic binder (or the mixture of an inorganic binder and a resin binder).

[0019] As shown in the enlarged view of FIG. 1(c), the bump body 15a formed by printing the Ag paste has a surface with large irregularities due to the Ag particles, which allows the bump body 15a to maintain high adhesion with the adhesive during mounting.

[0020] Next, in the step shown in Fig. 1(d), a bump film 15b made of a plating layer is formed. The bump film 15b can be formed by electrolytic plating or electroless plating. The material of the plating layer may be, for example, a Ni / Au layer, a Ni / Pd / Au layer, or a single Au layer, but in this embodiment, a single Au layer is used. At this time, although not shown in Fig. 1(d), a plating layer 14 (see Fig. 5(b)) is also formed on the surface of the wiring 11.

[0021] The bump body 15a and the bump film 15b constitute the bump 15 for electrically connecting an external conductive member of a mounted member to a conductive member (wiring 11).

[0022] As described above, through the steps shown in FIGS. 1(a) to 1(d), a mounting substrate B is formed, which includes a base material (ceramic substrate 10) having a conductive member (wiring 11) formed on its upper surface, and bumps 15 formed on the base material.

[0023] [Structure and manufacturing process of electronic components] 2(a), a non-conductive adhesive (NCP) 25, which is a fastening member, is applied from a container 32 onto the upper surface of the mounting substrate B. Any non-conductive adhesive that exhibits a strong fastening force when hardened may be used, such as epoxy resin, polyimide resin, modified polyimide resin, etc.

[0024] Next, in the step shown in FIG. 2(b), a chip tray 27 on which a large number of semiconductor chips 21 (mounting members) are mounted is prepared.

[0025] 2(c), the mounting substrate B is placed on a support table (not shown), the semiconductor chip 21 removed from the chip tray 27 is mounted on the partial region Rn of the mounting substrate B, and the back electrodes 22 (external conductor members) of the semiconductor chip 21 and the bumps 15 of the mounting substrate B are aligned with each other. Then, the non-conductive adhesive 25 is cured while the semiconductor chip 21 is pressed by a pressing member (not shown).

[0026] Fig. 9 is a diagram showing an example of the temperature-viscosity characteristics of the non-conductive adhesive 25. First, as shown in Fig. 9, the viscosity of the non-conductive adhesive 25 generally gradually decreases with increasing temperature, and then the adhesive exhibits a generally constant degree of viscosity within a predetermined temperature range, and hardens when the temperature exceeds a certain level.

[0027] 2(a), the non-conductive adhesive 25 is applied at a temperature of, for example, about room temperature (about 25° C.). At that temperature, the non-conductive adhesive 25 has a viscosity sufficient to fill spaces between the wiring 11 and bumps 15 provided on the surface of the mounting substrate B while maintaining a state in which the surfaces of the bumps 15 are covered. The non-conductive adhesive 25 also has a viscosity sufficient to maintain an area around the mounting substrate B where the non-conductive adhesive 25 is not present, as shown in FIG. 2(a).

[0028] 2(c), electronic component A and mounting board B are bonded together via non-conductive adhesive 25 at, for example, about room temperature. Then, with electronic component A and mounting board B bonded together, back electrodes 22 of semiconductor chip 21 (electronic component A) are pressed relatively against bumps 15 while non-conductive adhesive 25 is heated.

[0029] When the non-conductive adhesive 25 is applied to the mounting substrate B and heated to increase its temperature, its viscosity gradually decreases as shown in FIG. 9. Furthermore, when the temperature of the non-conductive adhesive 25 further increases, the non-conductive adhesive 25 has a low viscosity range in which the non-conductive adhesive 25 exhibits a generally constant viscosity within a certain temperature range. The viscosity is low enough that the non-conductive adhesive 25 present between the back electrode 22 and the bump 15 is discharged to the periphery of the back electrode 22 and the bump 15. That is, the non-conductive adhesive 25 becomes low-viscosity as the temperature increases by heating, and is discharged from between the back electrode 22 and the bump 15 in this low-viscosity range. As a result, the back electrode 22 and the bump 15 are bonded to each other so that there is sufficient conductivity between the back electrode 22 and the bump 15 as shown in FIG. 3(c).

[0030] The non-conductive adhesive 25 in this embodiment has temperature characteristics with a wide low viscosity range, as shown in Fig. 9. That is, in the manufacturing method according to this embodiment, the non-conductive adhesive 25 can maintain a low viscosity state for a long time until the applied non-conductive adhesive 25 is heated and cured. As a result, the non-conductive adhesive 25 is sufficiently discharged from between the back electrode 22 and the bump 15, so that sufficient conductivity between the back electrode 22 and the bump 15 can be ensured.

[0031] FIG. 10 is a diagram showing an example of the temperature-viscosity characteristics of a plurality of base agents contained in the non-conductive adhesive 25. The non-conductive adhesive 25 in this embodiment is configured to include base agents 1 and 2 having different temperature-viscosity characteristics. The base agents 1 and 2 are, for example, epoxy resins such as bisphenol F type, epoxy resins such as bisphenol A type, cresol novolac type epoxy resins, phenol novolac type epoxy resins, dicyclopentadiene (DCPD) type epoxy resins, etc. In this embodiment, two types of base agents are selected from the above-mentioned epoxy resins, which have different melting or softening temperatures and gelling or hardening temperatures, that is, different temperature ranges in which the viscosity decreases, due to differences in molecular skeletons and molecular weights. Among them, base agent 1 has a low viscosity range 1, which is a temperature range in which the viscosity is 5 Pa·s or less. Furthermore, base agent 2 has a low viscosity range 2, which is a temperature range in which the viscosity is 5 Pa·s or less. The lower limit of low-viscosity range 2 is higher than the lower limit of low-viscosity range 1, and the upper limit of low-viscosity range 2 is higher than the upper limit of low-viscosity range 1. Low-viscosity range 1 is in the range of about 50°C to about 90°C, and low-viscosity range 2 is in the range of about 70°C to about 110°C. That is, in this embodiment, the temperature ranges of low-viscosity range 1 and low-viscosity range 2 overlap each other. Also, the temperature at which the viscosity of main agent 2 is lowest is higher than the temperature at which the viscosity of main agent 1 is lowest. In this embodiment, the temperature at which the viscosity of main agent 1 is lowest is about 80°C, and the temperature at which the viscosity of main agent 2 is lowest is about 100°C.

[0032] In this embodiment, the non-conductive adhesive 25 includes two main components, but may include three or more main components. In addition to the multiple main components, the non-conductive adhesive 25 may further include an inhibitor that inhibits a decrease or increase in viscosity or hardening of at least one of the multiple main components, or an accelerator that accelerates a decrease or increase in viscosity or hardening. The non-conductive adhesive 25 may include both an inhibitor and an accelerator.

[0033] 11 and 12 are diagrams showing other examples of the temperature-viscosity characteristics of the non-conductive adhesive 25. As shown in FIG. 11, the non-conductive adhesive 25 may have a characteristic that the viscosity increases and then decreases again as the temperature increases in a part of the low-viscosity range. For example, in the non-conductive adhesive 25, there may be no or at least an overlapping region between the low-viscosity range of the main component 1 and the low-viscosity range of the main component 2. Also, as shown in FIG. 12, the non-conductive adhesive 25 may have a characteristic that the viscosity increases and then becomes approximately constant in a part of the low-viscosity range as the temperature increases. In this way, the viscosity of the non-conductive adhesive 25 does not need to be approximately constant in the entire region of the low-viscosity range in which the viscosity is equal to or lower than a predetermined viscosity.

[0034] FIG. 13 is a diagram showing the temperature-viscosity characteristics of the non-conductive adhesive in the comparative example. In the comparative example, the non-conductive adhesive contains one main component. The non-conductive adhesive in the comparative example has a property that its viscosity decreases as the temperature increases, and then the viscosity increases and hardens, but its low viscosity range is narrower than the low viscosity range of the non-conductive adhesive 25 in the present embodiment. That is, in the comparative example, in the process of heating the non-conductive adhesive to fix the mounting board and the semiconductor chip, the time during which the non-conductive adhesive has a sufficiently low viscosity is shortened. As a result, in the comparative example, there may be a case where the non-conductive adhesive present between the back electrode and the bump is not sufficiently discharged. When the conductivity between the back electrode and the bump was measured in an electronic component made using the non-conductive adhesive of the comparative example and an electronic component made using the non-conductive adhesive 25 of the present embodiment, the conductivity in the comparative example was about 50%, while the conductivity in the present embodiment was nearly 100%, and it was confirmed that the manufacturing method in the present embodiment has a remarkable effect.

[0035] When the non-conductive adhesive 25 is cured, the thermal contraction force of the non-conductive adhesive 25 causes the bumps 15 to plastically deform, and the mountain-shaped tops are flattened (see, for example, FIG. 5(a)). The thickness of the bumps 15 becomes 90% or less of the thickness before mounting. Then, as shown in FIGS. 3(a) and (b), the bumps 15 electrically connect the wiring 11 (conductive member) of the mounting substrate B and the back electrode 22 (external conductive member) of the semiconductor chip 21 (mounted member) to each other.

[0036] It is not necessary for the bumps to be plastically deformed, and they may simply be elastically deformed, but in order to achieve a large amount of deformation, it is preferable for them to be plastically deformed.

[0037] As a result of the above, an electronic component A is formed by mounting the semiconductor chip 21 (mounted member) on the mounting substrate B.

[0038] In the cross section shown in FIG. 2(c), the bump body 15a is in contact only with the wiring 11, but it is preferable that the bump body 15a also be in contact with the ceramic substrate 10, as described below.

[0039] As shown in FIG. 3(c), a specific filler 41 may be added to the non-conductive adhesive 25 (fixing member) so that the non-conductive adhesive 25 is composed of a base agent 40 and a specific filler 41 made of a plurality of particles. However, the base agent 40 is not necessarily made of resin alone, but generally contains various additives. The specific filler 41 brings the thermal expansion coefficient of the non-conductive adhesive 25 closer to the thermal expansion coefficients of the mounting substrate B (mainly the ceramic substrate 10) and the semiconductor chip 21, respectively, thereby reducing the thermal stress between the non-conductive adhesive 25 and the mounting substrate B, and between the non-conductive adhesive 25 and the semiconductor chip 21. This can increase the reliability of the electrical connection between the mounting substrate B and the semiconductor chip 25 (mounted member).

[0040] Typical examples of the material of the specific filler 41 as described above include insulating materials such as SiO2, ZrO2, SiC, and Al2O3. Semiconductor materials such as Si, Ge, and GaN may also be used. Even when the fastening member is a non-conductive adhesive, a small amount of a metal material such as W, Mo, Cu, Al, or an alloy thereof may be used within a range that allows the insulating properties of the non-conductive adhesive 25 to be maintained.

[0041] By adding the specific filler 41, the thermal expansion coefficient of the non-conductive adhesive 25 can be adjusted as follows.

[0042] In this embodiment, the thermal expansion coefficient of the mounting substrate B can be considered to be almost the same as the thermal expansion coefficient of the ceramic substrate 10. For example, when the ceramic substrate 10 is an alumina substrate, its thermal expansion coefficient is about 7×10 -6 / K, and when the semiconductor chip 21 is a silicon substrate, its thermal expansion coefficient is about 3×10 -6 / K. The thermal expansion coefficient of epoxy resin is approximately 62×10 -6 / K, and the thermal expansion coefficient of polyimide resin is 54×10 -6 / K, and the thermal expansion coefficient of modified polyimide resin is 20~60×10 -6 / K.

[0043] On the other hand, the thermal expansion coefficient of SiO2 is about 3×10 -6 / K, the thermal expansion coefficient of ZrO2 is about 8×10 -6 / K, the thermal expansion coefficient of SiC is about 4×10 -6 / K, the thermal expansion coefficient of Al2O3 is about 7.0×10 -6 / K. In other words, both materials have a thermal expansion coefficient that is nearly one order of magnitude lower than that of the resin material.

[0044] The thermal expansion coefficient of Cu is approximately 17×10 -6 / K, the thermal expansion coefficient of Al is approximately 21×10 -6 / K, it is relatively high, so it is weak at reducing the thermal expansion coefficient of non-conductive adhesives. On the other hand, the thermal expansion coefficient of W is about 4.5×10 -6 / K, the thermal expansion coefficient of Mo is about 5.1×10 -6 / K, which is as low as that of insulating materials, can fully perform the function of adjusting the thermal expansion coefficient.

[0045] Therefore, by mixing specific filler 41 into base agent 40, the thermal expansion coefficient of non-conductive adhesive 25 (bonding member) can be made closer to the thermal expansion coefficient of semiconductor chip 21 (mounted member) and mounting board B. Then, by changing the mixing ratio of specific filler 41 to base agent 40 according to the material of specific filler 41, the thermal expansion coefficient of non-conductive adhesive 25 can be adjusted to a desired range.

[0046] Furthermore, as shown in Figures 2(a) to (c), when the non-conductive adhesive 25 is applied onto the mounting substrate B and then the semiconductor chip 21 is mounted on the mounting substrate B, some of the specific fillers 41b are sandwiched at the boundary between the bumps 15 and the back electrode 22 of the semiconductor chip 21, as shown in Figure 3(c).

[0047] It is preferable to adjust the hardness of the cured bump 15 so that it is harder than the base agent 40 of the non-conductive adhesive 25 and softer than the specific filler 41. Furthermore, in the step shown in FIG. 1(c), when the bump body 15a is only preliminarily cured, it is preferable to adjust the hardness of the preliminarily cured bump 15 so that it is harder than the base agent 40 of the non-conductive adhesive 25 and softer than the specific filler 41. To achieve this, the temperature and time of the curing process may be appropriately selected. Note that the hardness of the preliminarily cured bump 15 may be harder than the specific filler 41 after the final curing process.

[0048] The "hardness" of the bumps means the resistance to plastic deformation of the printed ink that makes up the bumps when it is solidified. Methods for evaluating hardness include a Vickers hardness tester and a durometer.

[0049] 3(c), the specific filler 41b is pushed into the bump 15 while contacting the back electrode 22. At this time, in the boundary region between the bump 15 and the back electrode 22, the base material 40 of the non-conductive adhesive 25 is almost entirely expelled to the outside except in the vicinity of the base of the bump 15. Therefore, the bump 15 and the back electrode 22 are in stable electrical contact with each other in the region other than the portion where the specific filler 41b is sandwiched. As a result, the reliability of the electrical connection between the mounting substrate B and the semiconductor chip 21 (mounted member) is improved.

[0050] If the specific filler 41 is a conductive particle such as W or Mo, the outer portion of the non-conductive adhesive 25 maintains insulation while the bump 25 and the back electrode 22 are conductive via a portion of the specific filler 41b, thereby further improving the reliability of the electrical connection.

[0051] [Modification of bump formation position] In the above embodiment, the bumps 15 are formed only on the wiring 11 in the mounting substrate B, but in this embodiment, the bumps can be formed in various positions.

[0052] Figures 4(a) to (d) are plan views showing modified examples of the formation positions of bumps 15. Figures 5(a) to (d) are longitudinal sectional views corresponding to Figures 4(a) to (d). The left drawings in Figures 4(a) to (d) and 5(a) to (d) show the state on the mounting board, and the right drawings show the state of electronic component A after semiconductor chip 21 is mounted.

[0053] 4(a) and 5(a) show a case where bump 15 is formed across wiring 11 and the regions of ceramic substrate 10 on both sides of the wiring 11 on mounting substrate B. Although not shown in the cross section shown in FIG. 5(a), in another cross section, a plating layer continuous with bump film 15b is formed on the surface of wiring 11. Then, after mounting semiconductor chip 21, bump 15 is pressed and plastically deformed by back electrode 22 (not shown) of semiconductor chip 21, and the top portion (which is also the center portion) is flattened as shown in FIG. 5(a).

[0054] 4(b) and 5(b) show a case where bump 15 is formed across wiring 11 and the region of ceramic substrate 10 on one side of wiring 11 on mounting substrate B. As shown in FIG. 5(b), plating layer 14 is also formed on the surface of wiring 11, and bump film 15b and plating layer 14 of wiring 11 form a continuous film. Then, after mounting semiconductor chip 21, bump 15 is pressed by back electrode 22 (not shown) of semiconductor chip 21, causing plastic deformation, and the top portion is flattened, as shown in FIG. 5(b).

[0055] 4(c) and 5(c) show a case where the bump 15 is formed across the tip of the wiring 11 and the adjacent region of the ceramic substrate 10 on the mounting substrate B. In a cross section perpendicular to the cross section shown in the figures, the shape is as shown in Figures 4(b) and 5(b).

[0056] In this case as well, after the semiconductor chip 21 is mounted, the back surface of the semiconductor chip 21 is The bump 15 is pressed and plastically deformed by the pole 22 (not shown), and the top portion is flattened. Also, the plating layer 14 is formed on the surface of the wiring 11, and the bump film 15b and the plating layer 14 of the wiring 11 become a continuous film.

[0057] 4(d) and 5(d) show a case where bumps 15 are formed only in the region of the ceramic substrate 10 adjacent to the wiring 11 in the mounting board B. The cross section shown is perpendicular to the cross sections shown in FIGS. 4(a) to (c) and 5(a) to (c).

[0058] In this case as well, after mounting the semiconductor chip 21, the bumps 15 are pressed and plastically deformed by the back electrodes 22 (not shown) of the semiconductor chip 21, and the tops are flattened. Also, a plating layer 14 is formed on the surface of the wiring 11. Then, the plastically deformed bump coating 15b and the plating layer 14 of the wiring 11 come into contact with each other, so that after mounting, the bumps 15 and the wiring 11 are electrically connected to each other.

[0059] 4(a) to 4(c) and 5(a) to 5(c), the bumps 15 straddle the surfaces of the wiring 11 and the ceramic substrate 10. Therefore, the bumps 15 are in close contact with not only the wiring 11 but also the ceramic substrate 10, thereby enhancing the adhesion between the wiring 11 and the ceramic substrate 10 (base material).

[0060] [Example of bump structure] In the above embodiment, an example has been described in which the bump 15 is composed of the bump body 15a and the bump film 15b, but the structure of the bump 15 in this embodiment is not limited to this example.

[0061] 6(a) to 6(d) are vertical cross-sectional views showing examples of bump structures.

[0062] In the structure shown in Fig. 6(a), the bump 15 is composed of a single Ag layer formed by printing. In this case, the process of plating the surface of the bump 15 is unnecessary, and since Au is not used, the manufacturing cost can be reduced. In addition, the plastic deformation of the bump 15 during mounting is also easy.

[0063] In the structure shown in Fig. 6(b), an intermediate plating layer 15c is interposed between the bump body 15a and the bump film 15b. In this case, for example, a Ni plating layer can be formed as the intermediate plating layer 15c, and an Au plating layer can be formed as the bump film 15b. That is, the plating layer can be a Ni / Au layer. In this case, the intermediate plating layer 15c can improve the adhesion between the bump body 15a and the bump film 15b, and the Au plating thickness can be reduced to reduce manufacturing costs.

[0064] The intermediate plating layer 15c may be a plurality of plating layers, for example, Ni / Pd layers.

[0065] In the structure shown in Fig. 6(c), an intermediate plating layer 15c is interposed between the bump body 15a and the bump film 15b, only at the top of the bump body 15a and the bump film 15b. In this case, for example, a Ni plating layer can be formed as the intermediate plating layer 15c, and an Au plating layer can be formed as the bump film 15b. Since the Ni plating layer is hard, there is a risk that deformation of the entire bump 15 is hindered. However, in the structure shown in Fig. 6(c), plastic deformation is easy in the area where the Ni plating layer is not present. Therefore, the intermediate plating layer 15c can facilitate mounting while ensuring adhesion between the bump body 15a and the bump film 15b.

[0066] 6(d), the bump coating 15b and the intermediate plating layer 15c are formed only on the top of the bump body 15a. In this structure, the entire bump 15 is more easily plastically deformed than in the structure shown in 15(c).

[0067] An example of a manufacturing process for the structure shown in FIGS. 6(c) and 6(d) will be described in the second embodiment.

[0068] The mounting board B and electronic component of this embodiment provide the following advantageous effects.

[0069] At least the main body 15a of the bump 15 is formed by printing, so it is possible to form a thick-film bump 15 that would be difficult to form by plating. Therefore, even if there is a large variation in the height positions of the base material and the conductive member, it is possible to maintain high reliability of the electrical connection between the wiring 11 (conductive member) and the back electrode 22 (external conductive member) of the semiconductor chip 21 (mounted member) via the bump 15. In other words, it is possible to maintain high reliability of the electrical connection between the mounting board B and the mounted member.

[0070] As described later, even when a ceramic substrate 10 is used, the variation in height of the conductive member (such as the wiring 11) in each partial region Rn may be about 10 μm or more, taking into account warpage and dimensional errors of the conductive member during formation. However, in the protruding electrodes formed by electrolytic plating in the above-mentioned conventional Patent Document 1, the thickness is actually 5 to 8 μm due to limitations in the resist film thickness and plating time, so that it is not possible to maintain high reliability of the electrical connection between the conductive member and the external conductive member of the mounted member. Moreover, since the protruding electrodes in Patent Document 1 are formed using the wiring surface as the reference surface, the variation in the height position of the substrate surface caused by warpage of the substrate and the like are combined with the variation in the thickness of the wiring, resulting in large variation in the height position of the protruding electrodes.

[0071] In contrast, the thickness of the top of the bump body 15a formed by printing can be increased to about 20 to 50 μm, so even if there is a large variation in the height position of the conductor member, the reliability of the electrical connection between the conductor member and the external conductor member of the mounted member can be maintained at a high level. Also, since the bump body 15a formed by printing in this embodiment is formed using the substrate surface as the reference surface, the variation in the conductor member such as wiring can be ignored.

[0072] In the above embodiment, a ceramic substrate is used as the base material. However, the base material of this embodiment may be an inorganic substrate other than a ceramic substrate, such as a glass substrate, or an organic substrate made of polyimide, PET, PEI, or the like.

[0073] In particular, there are many advantages to using an inorganic substrate such as a ceramic substrate rather than an organic substrate as the base material. For example, let's compare a package with 1000 terminals.

[0074] Generally, in an organic substrate, the package area (corresponding to the partial region Rn) is 30 mm square or more, and the substrate thickness is 2 mm or more, but in an inorganic substrate such as a ceramic substrate, it is possible to reduce the area of ​​the partial region Rn by about 64% and the substrate thickness by about 78%. The overall size of an inorganic substrate such as a ceramic substrate is 100 to 300 mm square.

[0075] Furthermore, compared to organic substrates, ceramic substrates have higher heat and moisture resistance, allowing for the production of highly reliable electronic components.

[0076] Furthermore, in organic substrates, warping of about 250 μm occurs for a 30 mm square substrate at high temperatures, whereas in ceramic substrates and the like, warping at high temperatures can be suppressed to 50 μm or less.

[0077] However, even if a ceramic substrate or the like is used, the variation in height of the conductor members (such as wiring 11) will reach approximately 10 μm or more, taking into account warping and dimensional errors of the conductor members during formation.

[0078] Furthermore, in the case of an organic substrate that has a certain degree of flexibility, when the mounted component is strongly pressed against the mounting substrate during mounting, the organic substrate is deformed, so that the variation in height of the conductive members (such as wiring 11) is reduced. Therefore, even if the protruding electrode is thin, it is easy to bring the protruding electrode into contact with both the conductive member and the external conductive member.

[0079] In contrast, in the case of a hard ceramic substrate or glass substrate, it is difficult to reduce the variation in height of the conductive members (such as wiring 11) even if the mounted member is pressed against the mounting substrate during mounting. Therefore, by applying this embodiment to an inorganic substrate such as a ceramic substrate, it is possible to maintain high connection reliability while taking advantage of the above-mentioned advantages of the inorganic substrate.

[0080] In particular, since the height of the upper end of bump 15 from the top surface of the base material (in this embodiment, ceramic substrate 10) is at least twice the height of the conductive member (in this embodiment, wiring 11), variations in the height of the conductive member can be easily absorbed.

[0081] In the above embodiment, the bumps are shaped like mountains, but they do not necessarily have to be shaped like mountains. Even if the tip is a relatively flat plateau, the deformation of the bump during mounting makes it possible to maintain high reliability of the electrical connection after mounting.

[0082] In addition, the deformation of the bump is preferably plastic, but is not necessarily limited to plastic, and may be elastic. Even in the case of elastic deformation, it is possible to ensure the reliability of the electrical connection by the fastening force of a fastening member such as a non-conductive adhesive.

[0083] (Embodiment 2) In this embodiment, an example of a manufacturing process for the bump structure shown in FIG. 6(c) or (d) will be described.

[0084] 7(a) to 7(e) are vertical cross-sectional views showing the manufacturing process of the bump according to the second embodiment.

[0085] 7(a), a bump body 15a is formed on the ceramic substrate 10 by screen printing using Ag paste, straddling the wiring 11 and the regions of the ceramic substrate 10 on both sides thereof. The method for forming the bump body 15a is as described in the first embodiment.

[0086] Next, in the process shown in Fig. 7(b), an initial resist film Re1 thicker than the bump body 15a is formed on the ceramic substrate 10. Then, in the process shown in Fig. 7(c), the initial resist film Re1 is irradiated with O2 plasma to form a reduced-thickness resist film Re2 thinner than the bump body 15a. At this time, only the top of the mountain-shaped bump body 15a protrudes above the reduced-thickness resist film Re2.

[0087] 7(d), electroless plating is performed to form an intermediate plating layer 15c made of a Ni layer on the surface of the exposed top portion of the bump body 15a. However, electrolytic plating may be performed instead of electroless plating.

[0088] 7(e), the reduced-thickness resist film Re2 is removed by using a resist remover or by irradiating O2 plasma, and then electroless plating is performed to form a bump film 15b made of Au on the surfaces of the bump body 15a and the intermediate plating layer 15c. However, electrolytic plating may be performed instead of electroless plating.

[0089] That is, the bump 15 is formed by interposing the intermediate plating layer 15c only at the top portion between the bump body 15a and the bump coating 15b.

[0090] In this manner, the bump 15 shown in FIG. 6(c) is formed.

[0091] On the other hand, after the step shown in Fig. 7(d), the reduced-thickness resist film Re2 may not be removed, and electroless plating using Au may be subsequently performed to form the bump film 15b only on the intermediate plating layer 15c, as shown by the dotted line in Fig. 7(d). In this case, the structure of the bump 15 shown in Fig. 6(d) is obtained, and the bump film 15b does not exist on the region other than the top of the bump body 15a.

[0092] 7(a), the bump body 15a may be made of a non-conductive material, such as an organic resin. In that case, a process for generating nuclei for electroless plating is required before electroless plating is performed.

[0093] The electroless plating and the nucleation treatment are well known and commonly used processes, and therefore a detailed description thereof will be omitted.

[0094] Generally, when plating is performed, it is necessary to form a resist pattern that covers the non-plating area. In this case, since alignment is required between the resist pattern that covers the non-plating area and the pattern of the wiring 11 and the bump body portion 15a, a photolithography process for the resist pattern is required.

[0095] In contrast, in the method of the second embodiment, the bump body 15a formed by printing has a mountain shape, and by simply performing a process to thin the initial resist pattern Re1 (O2 plasma irradiation in this embodiment), only the region to be electroless plated can be exposed. In other words, the self-alignment effect makes the photolithography process unnecessary, thereby simplifying the manufacturing process and reducing manufacturing costs.

[0096] (Embodiment 3) Next, a third embodiment for ensuring smooth flow of the adhesive when mounting a mounted component will be described.

[0097] FIG. 8 is a plan view showing a plane pattern of the bump 15 according to the third embodiment.

[0098] As shown in the figure, in this embodiment, the planar shape of bump 15 is set so that the dimension in a first direction x from the center toward the periphery of ceramic substrate 10 (base material) is longer than the dimension in a second direction y perpendicular to the first direction x. In other words, the first direction x is the longitudinal direction of bump 15. The planar shape of bump 15 may be an ellipse as shown in FIG. 8, as well as an oval, a rectangle, a diamond, a track shape, an irregular shape, and the like, and any of these may be used.

[0099] In addition to the bumps 15, dummy bumps 16 are provided on the ceramic substrate 10.

[0100] According to this embodiment, the following effects can be obtained.

[0101] When mounting a member to be mounted on a mounting board, an adhesive (non-conductive adhesive 25 in the first embodiment) is applied as a fixing agent to the region Ra shown in Fig. 8, and the member to be mounted is placed on top of it. At that time, in a natural state, the adhesive spreads from the region Ra to the region Rb.

[0102] In this embodiment, the dimension of the bump 15 in the first direction x is set to be longer than the dimension of the bump 15 in the second direction y perpendicular to the first direction x, thereby improving the fluidity of the adhesive.

[0103] Also, as shown in region Rb, while the adhesive does not easily flow to the corners of the ceramic substrate 10, the adhesive overflows from the sides. In this embodiment, therefore, dummy bumps 16 are provided to hinder the flow of the adhesive to the sides, so that the adhesive flows as evenly as possible in all directions. Thus, this embodiment can prevent the adhesive from overflowing to the sides.

[0104] In this embodiment, the first direction x is a direction perpendicular to or parallel to each side of the rectangular ceramic substrate 10, but the first direction x (longitudinal direction) may be a direction (radial direction) from the center point outward. In other words, regardless of the shape of the ceramic substrate 10, the longitudinal directions of the bumps 15 may be arranged in a radial pattern.

[0105] However, by aligning them as in this embodiment, they can be adapted to a normal wiring pattern, so that mounting can be carried out smoothly.

[0106] (Embodiment 4) Next, a fourth embodiment in which printing ink 15x is transferred to a ceramic substrate 10 in the step shown in FIG. 1(b) will be described.

[0107] Fig. 14 is a vertical cross-sectional view showing a manufacturing process of a mounting board according to embodiment 4. Like Fig. 1(b), Fig. 14 illustrates a vertical cross-sectional structure of a part of each partial region Rn in Fig. 1(a).

[0108] 14, in this embodiment, after placing the printing plate 30 on the ceramic substrate 10, printing ink 15x is supplied onto the printing plate 30, and the squeegee 31 slides from left to right in the figure to fill the openings 33 of the printing plate 30 with the printing ink 15x. The squeegee 31 also scrapes off the printing ink on the printing plate 30. As a result, the printing ink 15x fills only the openings 33, and the filled printing ink 53 is transferred to the ceramic substrate 10. Then, the filled printing ink 53 is cured to form the bumps 15 (or bump main bodies 15a).

[0109] Fig. 15 is a diagram showing an example of the cumulative distribution of dimensions of conductive particles 51 contained in printing ink 15x. In this embodiment, printing ink 15x mainly contains a large number of conductive particles 51 and a resin binder 52. The conductive particles 51 have a cumulative distribution of dimensions as shown in Fig. 15. That is, in this embodiment, the dimensions of the large number of conductive particles 51 are distributed generally between 0.1 µm and 20 µm. Furthermore, the conductive particles 51 have a cumulative 50% dimension of 6.8 µm and a cumulative 90% dimension of 14.8 µm.

[0110] FIG. 16 is a diagram showing an example of the relationship between the size of the opening 33 of the printing plate 30, the bump defect rate (non-conductivity rate), and the bump height. In FIG. 16, the horizontal axis shows the size (μm) of the opening 33 of the printing plate 30, the left vertical axis shows the defect rate (%) of the bump 15, and the right axis shows the bump height (μm). The graph showing the bump height also shows the error range (variation) at each point. The bump defect rate is the non-conductivity rate between the back electrode and the bump. The bump height is the height of the bump 15 (or the bump main body 15a) in which the printing ink 53 is hardened after filling. Note that FIG. 16 shows the result of measuring the bump formed by transferring the printing ink 15x having the cumulative distribution shown in FIG. 15 to the ceramic substrate 10 using the printing plate 30 with a thickness t of 30 μm.

[0111] 16, the bump defect rate is about 62% when the opening dimension A is 20 μm, but as the opening dimension A increases, the bump defect rate decreases, the defect rate is about 6% when the opening dimension A is 30 μm, and the bump defect rate is about 0% when the opening dimension A is 40 μm or more. This is considered to occur because when the opening dimension A is not large enough relative to the thickness t of the printing plate 30 (for example, the opening dimension A is 30 μm or less), the conductive particles 51 remain in the openings 33 of the printing plate 30, and the printing ink 15x is not sufficiently transferred to the ceramic substrate 10. From this, it is considered that the opening dimension A of the printing plate 30 is preferably about four times or more the cumulative 50% dimension of the conductive particles 51, or about two times or more the cumulative 90% dimension. For example, in the results shown in Figure 16, the opening dimension A of the printing plate 30 is approximately 5.8 times the cumulative 50% dimension of 6.8 μm (see Figure 15), and approximately 2.7 times the cumulative 90% dimension of 14.8 μm (see Figure 15).

[0112] 16, when the opening dimension A of the printing plate 30 is in the range of about 40 μm or more and 60 μm or less, the error range of the bump height is about 5 μm or less. On the other hand, when the opening dimension A is about 70 μm or more, the variation in the bump height increases rapidly to 10 μm or more. This is because, if the opening dimension A of the printing plate 30 becomes too large compared to the thickness t of the printing plate 30, the printing ink 15x filled in the opening 33 is scraped off by the squeegee 31, and as a result, the printing ink 53 after filling and, ultimately, the bump height are largely varied. From this, it is considered that the opening dimension A of the printing plate 30 is preferably about 1.2 times or more and about 2.5 times or less than the thickness t of the printing plate.

[0113] It is also considered preferable that the opening dimension A of the printing plate 30 is 10 times or less than the cumulative 50% dimension or 5 times or less than the cumulative 90% dimension of the conductive particles 51. For example, in the results shown in Fig. 16, the opening dimension A of the printing plate 30 is about 8.8 times the cumulative 50% dimension of 6.8 µm (see Fig. 15), and about 4.1 times the cumulative 90% dimension of 14.8 µm (see Fig. 15).

[0114] According to this embodiment, by appropriately controlling the opening dimension A of the printing plate 30 relative to the cumulative dimension of the conductive particles 51 and the thickness t of the printing plate 30, it is possible to provide mounting substrates and electronic components with an extremely low bump defect rate and stable bump height.

[0115] The structures and manufacturing methods of the embodiments of the present invention disclosed above are merely examples, and the scope of the present invention is not limited to the scope of these descriptions. The scope of the present invention is defined by the claims, and further includes all modifications within the meaning and scope equivalent to the claims. [Explanation of symbols]

[0116] A Electronic Components B. Mounting board Ra,Rb,Rn area Re1 Initial resist film Re2 reduced thickness resist film x 1st direction y second direction 10 Ceramic substrate (base material) 11 Wiring (conductor material) 12 Via 13 Back electrode 15. Bump 15a Bump body 15b Bump coating 15c Interlayer plating 15x printing ink 16 Dummy Bump 21 Semiconductor Chips 22 Back electrode 25 Non-conductive adhesive (adhesive material) 30 Printing plate making 31 Squeegee 32 Container 33 Opening 40 Main Agent 41 Specific fillers 41a Specific filler 41b Specific filler 51 Conductive Particles 52 Resin Binder 53 Printing ink after filling

Claims

1. preparing a mounting substrate having a plurality of bumps; preparing a mount member having a plurality of external conductor members; applying an adhesive material to one or both of a surface of the mounting substrate on which the bumps are formed and a surface of the mounted member on which the external conductor member is formed; a step of pressing the mounting substrate against the mounted member via the fastening member so that the plurality of bumps come into contact with the plurality of external conductor members, thereby fastening the mounting substrate and the mounted member to each other with the fastening member; Equipped with The step of applying the adhesive member includes: a step of preparing, as the adhesive member, a material including a first main agent and a second main agent, the viscosity of which changes depending on temperature, wherein the first main agent has a first viscosity that is the lowest at a first temperature, the second main agent has a second viscosity that is the lowest at a second temperature that is higher than the first temperature, and the adhesive member has a viscosity that is higher than the first viscosity and the second viscosity at a third temperature that is lower than the first temperature, and has a property of being hardened at a fourth temperature that is higher than the second temperature; applying the adhesive material to one or both of the mounting substrate and the mounted member at a temperature lower than the first temperature; Including, The fixing step includes: pressing the mounting board against the mounted member while the temperature of the fastening member is lower than the first temperature; a step of heating the adhesive member to a temperature higher than the first temperature while pressing the mounting board against the mounted member, thereby reducing the viscosity of the adhesive member; heating the fastening member to a temperature greater than the second temperature to cure the fastening member; A method for manufacturing an electronic component, comprising:

2. 2. The method for manufacturing an electronic component according to claim 1, wherein the step of preparing a mounting substrate on which a plurality of bumps are provided comprises the steps of: Providing a conductive ink containing conductive particles; preparing a printing plate having a plurality of openings with predetermined opening dimensions; transferring the conductive ink to the mounting substrate through the openings of the printing plate to form the bumps on the mounting substrate; The conductive particle size is 0.1 μm or more and 20 μm or less, the opening size of the printing plate is four times or more than a cumulative 50% size of the conductive particles or two times or more than a cumulative 90% size of the conductive particles; an opening size of the printing plate is 10 times or less than a cumulative 50% size of the conductive particles or 5 times or less than a cumulative 90% size of the conductive particles; The opening dimension of the printing plate is 1.2 times or more and 2.5 times or less than the thickness of the printing plate. It is characterized by:

Images