Patent Publication Number: US-2018040525-A1

Title: Electronic component-mounted body and method for manufacturing same

Description:
This nonprovisional application claims priority under 35 U.S.C. §119 on Patent Application No. 2016-155713 filed in Japan on Aug. 8, 2016, the entire contents of which are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present invention relates to an electronic component-mounted body which includes a wiring substrate and an electronic component mounted on the wiring substrate, and a method for manufacturing the electronic component-mounted body. 
     BACKGROUND ART 
     An electronic component-mounted body (e.g., a printed-circuit-mounted product) which includes a wiring substrate (e.g., a printed wiring board) and an electronic component of various types (e.g., an IC chip) mounted on the wiring substrate is widely employed for use in an electronic device such as a communication device. Patent Literatures 1 through 4 are examples of documents disclosing the electronic component-mounted body. 
     Patent Literature 1 discloses a microwave/millimeter wave circuit device which is obtained in such a manner that an MMIC (monolithic microwave integrated circuit) chip is mounted on a baseboard by flip chip mounting with use of a bump made of Au or the like, and a gap between the MMIC chip and the baseboard (specifically, an outer side of an insulator wall surrounding the circuit inside the MMIC chip) is filled with underfill. 
     Patent Literature 2 discloses a semiconductor device which is obtained in such a manner that a semiconductor element is mounted on a circuit board by flip chip mounting with use of both a solder with a low melting point and a solder with a high melting point, and a gap between the semiconductor element and the circuit board is filled with a sealing resin having a flux function. 
     Patent Literature 3 discloses a wireless device which is obtained in such a manner that a high-frequency IC chip for a power amplifier is mounted on a substrate by flip chip mounting, and a gap between the high-frequency IC chip and the substrate is filled with underfill. 
     Patent Literature 4 discloses a flip chip mounted structure in which an IC chip is flip-chip mounted on a substrate. The flip chip mounting structure is achieved by providing a post, which is made of a dry film resist, between the IC chip and the substrate in order to hold the IC chip at a predetermined height and fill a space below the IC chip with underfill without letting air bubbles into the underfill. 
     Flip chip mounting is the fastest method for connecting a circuit of an MMIC chip while allowing the performance of the MMIC chip to be substantially maintained. As such, flip chip mounting is widely used as a method for mounting an MMIC chip to and from which a signal in a microwave band or a millimeter wave band is supplied or outputted. 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] 
     Japanese Patent Application Publication Tokukai No. 2000-269384 (Publication date: Sep. 29, 2000) 
     [Patent Literature 2] 
     Japanese Patent Application Publication Tokukai No. 2006-54360 (Publication date: Feb. 23, 2006) 
     [Patent Literature 3] 
     Japanese Patent Application Publication Tokukai No. 2013-102356 (Publication date: May 23, 2013) 
     [Patent Literature 4] 
     Japanese Patent Application Publication Tokukai No. 2001-6805 (Publication date: Mar. 16, 2001) 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, none of the conventional techniques above takes into account defective mounting which is caused by a difference between a linear expansion coefficient of a wiring substrate and a linear expansion coefficient of an electronic component mounted on the wiring substrate. 
     This problem is detailed below, with reference to  FIG. 8 , on the basis of an example case in which an IC chip (a Si chip)  120  is mounted on an LCP (liquid crystal polymer) substrate  110 . The LCP substrate  110  is constituted by an LCP base material  111  and wiring formed on a surface of the LCP base material  111 . The LCP base material  111  is a material whose linear expansion coefficient is anisotropic, and has a linear expansion coefficient of 1 ppm/K in an MD (machine direction) direction and a linear expansion coefficient of 64 ppm/K in a TD (transverse direction) direction. Meanwhile, the IC chip  120  has a linear expansion coefficient of approximately 2.6 ppm/K. 
       FIG. 8  is a view illustrating a method for mounting the IC chip  120  on the LCP substrate  110 . (a) through (d) of  FIG. 8  are side views each illustrating the IC chip  120  and the LCP substrate  110  in each step of the method. Note that in each of (a) through (d) of  FIG. 8 , a right-to-left direction of a drawing sheet of  FIG. 8  corresponds to the TD direction of the LCP substrate  110 . 
     (a) of  FIG. 8  illustrates a state in which the IC chip  120  is mounted on the LCP substrate  110 . The LCP substrate  110  includes the LCP base material  111 , a substrate wiring layer  112  provided on an upper surface of the LCP base material  111 , and a passivation layer  113  provided above the upper surface of the LCP base material  111  so as to cover part of the substrate wiring layer  112 . The IC chip  120  includes a semiconductor base material  121 , a pad  122  provided on a back surface of the semiconductor base material  121 , a Cu pillar  123  connected to the pad  122 , and a solder layer  124  provided at a tip of the Cu pillar  123 . When the IC chip  120  is mounted on the LCP substrate  110 , the tip of the Cu pillar  123  of the IC chip  120  and an exposed portion of the substrate wiring layer  112  of the LCP substrate  110  come in contact with each other via the solder layer  124 . 
     (b) of  FIG. 8  illustrates a state in which a reflow process is being performed in a heated atmosphere in order to melt the solder layer  124 . In the heated atmosphere, the LCP substrate  110  and the IC chip  120  expand (extend) in the TD direction independently of each other (since the solder layer  124  is melted, the LCP substrate  110  does not accelerate the expansion of the IC chip  120 , and the IC chip  120  does not inhibit the expansion of the LC chip  110  either). Since the linear expansion coefficient of the LCP substrate  110  in the TD direction is greater than that of the IC chip  120 , an amount of expansion (extension) of the LCP substrate  110  in the TD direction is greater than that of the IC chip  120 . 
     (c) of  FIG. 8  illustrates a state in which the atmosphere is cooled down (has returned to room temperature) after completion of the reflow process. In accordance with the cooling of the atmosphere, the IC chip  120  contracts toward a central part (indicated by a broken line in (c) of  FIG. 8 ) of the IC chip  120 . Meanwhile, the LCP base material  111  remains in an expanded state due to having thermoplasticity. This either causes the solder layer  124  to break so that the Cu pillar  123  falls off from the exposed portion of the substrate wiring layer  112 , or causes the LCP substrate  110  to be warped as illustrated in (c) of  FIG. 8 . 
     In a case where an external force is applied to the LCP substrate  110  in a direction indicated by an arrow in (d) of  FIG. 8  in order to cancel the warpage of the LCP substrate  110 , the solder layer  124  is broken by stress applied in a shear direction, so that the Cu pillar  123  becomes detached from the exposed portion of the substrate wiring layer  112 , as illustrated in a part surrounded by a broken line in (e) of  FIG. 8 . 
     It is thus possible that expansion of an IC chip and an LCP substrate at respective different linear expansion coefficients in a heating (reflow) step during solder connection causes a defective solder connection. 
     Note that  FIG. 8  is concerned with the TD direction, in which the linear expansion coefficient of the LCP substrate  110  is 64 ppm/K. In the example illustrated in  FIG. 8 , there is no significant difference in linear expansion coefficient between the LCP substrate  110  and the IC chip  120  in the MD direction, in which the linear expansion coefficient of the LCP substrate  110  is 1 ppm/K. Accordingly, the above-described defect in the TD direction is not caused in the MD direction. 
     The present invention is accomplished in view of the foregoing problem. An object of the present invention is to provide: an electronic component-mounted body which includes a wiring substrate and an electronic component mounted on the wiring substrate and enables prevention of defective mounting which is caused by a difference in linear expansion coefficient between the wiring substrate and the electronic component; and a method for manufacturing the electronic component-mounted body. 
     Solution to Problem 
     In order to attain the object, an electronic component-mounted body in accordance with the present invention is an electronic component-mounted body including: a wiring substrate; and an electronic component including a terminal connected to wiring of the wiring substrate by soldering, the electronic component being fixed to the wiring substrate with use of a post which is made of a thermosetting resin and not in contact with the wiring and the terminal. 
     Further, in order to attain the object, a method, in accordance with the present invention, for manufacturing an electronic component-mounted body is a method for manufacturing an electronic component-mounted body including a wiring substrate and an electronic component, the method including: a deposition step of causing a thermosetting resin in an uncured state to be deposited (i) on the wiring substrate into a columnar shape without bringing the thermosetting resin into contact with wiring of the wiring substrate or (ii) on the electronic component into a columnar shape without bringing the thermosetting resin into contact with a terminal of the electronic component; a contact step of bringing the terminal of the electronic component into contact with the wiring via solder without bringing the thermosetting resin into contact with the terminal and the wiring; a heating step of heating the thermosetting resin and the solder so as to cure the thermosetting resin and also to melt the solder; and a cooling step of cooling the solder so as to cure the solder. 
     Advantageous Effects of Invention 
     According to an embodiment of the present invention, it is possible to provide an electronic component-mounted body which enables prevention of defective mounting which is caused by a difference in linear expansion coefficient between a wiring substrate and an electronic component mounted on the wiring substrate. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view illustrating a configuration of an embodiment of an electronic component-mounted body in accordance with the present invention. (a) of  FIG. 1  is a top view of the electronic component-mounted body, (b) of  FIG. 1  is a cross-sectional view taken along a line A-A′ in (a) of  FIG. 1 , and (c) of  FIG. 1  is a cross-sectional view taken along a line B-B′ in (a) of  FIG. 1 . 
         FIG. 2  is a flowchart showing a method for manufacturing the electronic component-mounted body illustrated in  FIG. 1 . 
         FIG. 3  is a cross-sectional view illustrating a process for manufacturing the electronic component-mounted body manufactured in accordance with the flowchart of  FIG. 2 . 
         FIG. 4  is a view illustrating a configuration of another embodiment of the electronic component-mounted body in accordance with the present invention. (a) of  FIG. 4  is a top view of the electronic component-mounted body, (b) of  FIG. 4  is a cross-sectional view taken along a line A-A′ in (a) of  FIG. 4 , and (c) of  FIG. 4  is a cross-sectional view taken along a line B-B′ in (a) of  FIG. 4 . 
         FIG. 5  is a top view illustrating a configuration of still another embodiment of the electronic component-mounted body in accordance with the present invention. 
         FIG. 6  is a top view illustrating a configuration of still another embodiment of the electronic component-mounted body in accordance with the present invention. 
         FIG. 7  is a cross-sectional view illustrating a configuration of still another embodiment of the electronic component-mounted body in accordance with the present invention. 
         FIG. 8  is a view illustrating a conventional configuration. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiment 1 
     The following description will discuss, with reference to  FIGS. 1 through 3 , an embodiment of an electronic component-mounted body in accordance with the present invention and a method for manufacturing the electronic component-mounted body. 
     [Configuration of Electronic Component-Mounted Body] 
       FIG. 1  is a view schematically illustrating a configuration of an electronic component-mounted body  1  in accordance with Embodiment 1. (a) of  FIG. 1  is a top view of the electronic component-mounted body  1 , (b) of  FIG. 1  is a cross-sectional view taken along a line A-A′ in (a) of  FIG. 1 , and (c) of  FIG. 1  is a cross-sectional view taken along a line B-B′ in (a) of  FIG. 1 . Note that for easy explanation, (a) of  FIG. 1  partially includes a transparent view. 
     The electronic component-mounted body  1  in accordance with Embodiment 1 includes a wiring substrate  10 , an IC chip  20  (electronic component), and posts  30 . 
     The wiring substrate  10  includes an LCP base material  11 , a substrate wiring layer  12  (wiring) provided on an upper surface of the LCP base material  11 , and a passivation layer  13  provided over the upper surface of the LCP base material  11  so as to cover part of the substrate wiring layer  12 . As illustrated in (a) of  FIG. 1 , the LCP base material  11  has the upper surface which has a quadrangular shape and on which a plurality of wires constituted by the substrate wiring layer  12  are provided so as to extend from a peripheral edge portion of the LCP base material  11  to a central part of the upper surface of the LCP base material  11 . Note that the number of the plurality of wires constituted by the substrate wiring layer  12  is not limited to the number illustrated in (a) of  FIG. 1 . The passivation layer  13  is provided so as to cover a middle portion of each of the plurality of wires, and has an opening  13   a  in a central part of the passivation layer  13 . Due to the provision of the passivation layer  13  in this fashion, both ends of each of the plurality of wires are exposed so as to constitute a connection terminal. 
     To describe the LCP base material  11  in further detail, a linear expansion coefficient of the LCP base material  11  is anisotropic on the upper surface of the LCP base material  11 . Specifically, a linear expansion coefficient of the LCP base material  11  in a TD direction (first direction) shown in (a) of  FIG. 1  is greater than that in a MD direction (second direction). For example, the LCP base material  11  has a linear expansion coefficient of 64 ppm/K in the TD direction shown in (a) of  FIG. 1  and a linear expansion coefficient of 1 ppm/K in the MD direction shown in (a) of  FIG. 1 . That is, the LCP base material  11  has a property of extending, when heated, along the TD direction to a greater extent than along the MD direction. Note that in Embodiment 1, the LCP base material  11  is film-shaped and flexible. Even in a state where the substrate wiring layer  12  and the passivation layer  13  are provided on the LCP base material  11  (i.e., in a state where the wiring substrate  10  is formed), the LCP base material  11  maintains the flexibility and the above-described anisotropy of the LCP base material  11 . 
     As illustrated in (a) of  FIG. 1 , the IC chip  20  has a semiconductor base material  21  having a quadrangular-shaped upper surface. Further, as illustrated in (b) of  FIG. 1 , the IC chip  20  has (i) a Cu pillar  23  provided on an I/O pad  22  on a back surface of the semiconductor base material  21 , the I/O pad  22  being an (external) terminal of an MMIC, and (ii) a solder layer  24  and a flux agent  25  which are provided at a tip of the Cu pillar  23 . A plurality of the I/O pads  22  are provided in a peripheral edge portion of the quadrangular-shaped back surface of the semiconductor base material  21  (for example, in a peripheral arrangement) so as to each be located in a position facing the connection terminal of the substrate wiring layer  12 , which connection terminal is exposed in a central part of the wiring substrate  10 . 
     Note that a region of the back surface of the IC chip  20  (the semiconductor base material  21 ) in which region the I/O pad  22  is provided is hereinafter referred to as a “terminal-provided region,” and a region of the back surface in which region no I/O pad  22  is provided is hereinafter referred to as a “terminal-less region.” That is, in Embodiment 1, a peripheral part of the back surface of the IC chip  20  (the semiconductor base material  21 ) which peripheral part extends along four edges of the back surface is the terminal-provided region, and a region which is surrounded by the peripheral part and includes a central part of the back surface is the terminal-less region. 
     Note that an integrated circuit (IC) of the IC chip  20  may be a well-known high-frequency IC other than the MMIC, or may be even any well-known IC without being restricted to a high-frequency one. 
     The posts  30  are each a columnar structure which stands upright between the terminal-less region of the IC chip  20  and the upper surface of the LCP base material  11  (the wiring substrate  10 ) so as to be in contact with the terminal-less region and a region of the upper surface of the LCP base material  11  which region faces the terminal-less region. More specifically, (i) a lower end of each post  30  is fixedly in contact with the central part and the vicinity thereof of the upper surface of the LCP base material  11 , the central part and the vicinity thereof not being provided with the substrate wiring layer  12 , and (ii) an upper end of the post  30  is fixedly in contact with the terminal-less region of the IC chip  20 . Since a high-frequency signal is transmitted through a terminal of the IC chip  20 , specific inductive capacity/dielectric dissipation factor of an insulating resin applied around the terminal has a significant influence on transmission loss. Accordingly, the atmosphere, which has a specific inductive capacity of approximately 1, is desirable. In view of this, the posts  30  are preferably provided in a central part (i.e., terminal-less region) of the IC chip  20 , so that the mounted body has an improved strength and the transmission characteristics of the IC terminal is prevented from degrading. 
     The posts  30  are made of a resin which has a thermosetting property and an insulating property and also exhibits a good adhesion property between the LCP base material  11  and the IC chip  20 . Specifically, an insulating resin containing epoxy as a main component and cures at a curing temperature of 200° C. to 250° C. within 10 seconds is used. Note that the resin constituting the posts  30  does not have to have an insulating property, but in a case where the resin may affect the electrical characteristics of the IC chip  20 , it is preferable that the resin be an insulating resin. As described later, the resin constituting the posts  30  has a high thixotropy, and preferably has a viscosity of 45,000 Pa·s to 300,000 Pa·s before being heated (before being thermally cured). Further, the thermosetting resin constituting the posts  30  preferably contracts as being thermally cured. 
     The provision of the posts  30  having as described above allows a position of the LCP base material  11  (the wiring substrate  10 ) to be fixed at a contact portion between the LCP base material  11  (the wiring substrate  10 ) and the lower end of each of the posts  30  at a heating step of a reflow process during mounting. This suppresses expansion of the LCP base material  11  (the wiring substrate  10 ) at the contact portion and a region around the contact region. Note here that the IC chip  20  has a linear expansion coefficient of approximately 2.6 ppm/K. As such, fixation of the position of the LCP base material  11  by the posts  30  with respect to the TD direction, in which the linear expansion coefficient of the LCP base material  11  is 64 ppm/K, allows suppressing expansion of the LCP base material  11  in the TD direction. With respect to the MD direction, in which the LCP base material  11  has a linear expansion coefficient of 1 ppm/K, the IC chip  20  expands to a slightly greater extent than the LCP base material  11 . However, since a difference in linear expansion coefficient between the IC chip  20  and the LCP base material  11  is only minor, defective mounting due to a difference in amount of expansion is unlikely to occur. 
     Further, in Embodiment 1, two posts  30  (a post and another post) are arranged along the TD direction as illustrated in (a) of  FIG. 1 . As described above, a linear expansion coefficient of the LCP base material  11  in the MD direction is greater than that in the TD direction. As such, the provision of the posts  30  at a plurality of positions on the same line along the TD direction allows efficiently suppressing, with use of a limited number of posts  30 , expansion along the TD direction which is caused by heat. 
     Note here that a sum of (i) a length of one of the posts  30  along the TD direction (more precisely, the same line described above) in a contact region between the one of the posts  30  and the LCP base material  11  and (ii) a length of the other of the posts  30  along the TD direction (more precisely, the same line described above) in a contact region between the one other of the posts  30  and the LCP base material  11  is defined as X. X is a sum of the widths of the respective posts  30  as measured along a right-to-left direction of a drawing sheet of (b) of  FIG. 1 . Meanwhile, a length of each post  30  in a contact region between the post  30  and the LCP base material  11  as measured along another direction is defined as Y. Y, for example, is a width of each post  30  as measured along a right-to-left direction of a drawing sheet of (c) of  FIG. 1 . X and Y are in a relation of X&gt;Y. 
     Designing the posts  30  as described above allows the position of the LCP base material  11  to be fixed across a relatively large width along the TD direction. This enables effective suppression of expansion of the LCP base material  11  in the TD direction. 
     Thus, according to Embodiment 1, it is possible to provide an electronic component-mounted body which, due to including the posts  30 , enables suppression of expansion of the LCP base material  11  in the TD direction and, accordingly, enables prevention of defective mounting caused by a difference in linear expansion coefficient between the LCP base material  11  and the IC chip  20 . 
     Note that a gap between the IC chip  20  and the LCP base material  11  of the electronic component-mounted body  1  in accordance with Embodiment 1 is not sealed by an underfill material. That is, the electronic component-mounted body  1  has an empty space (air layer) under the IC chip  20 . 
     Note that, as illustrated in (a) of  FIG. 1 , each of the posts  30  is a columnar structure having a circular shape when viewed from above, but the shape of each of the posts  30  when viewed from above is not limited to this. 
     [Method for Manufacturing Electronic Component-Mounted Body] 
     The following description will discuss, with reference to  FIGS. 2 and 3 , a method for manufacturing the electronic component-mounted body  1  which has the configuration as described above.  FIG. 2  is a flowchart for explaining a method for manufacturing the electronic component-mounted body  1 .  FIG. 3  is a view illustrating a method for manufacturing the electronic component-mounted body  1 . (a) through (f) of  FIG. 3  are each a cross-sectional view of the wiring substrate  10  (the LCP base material  11 ) and the like viewed from the same direction as in (b) of  FIG. 1 . 
     First, the wiring substrate  10  is prepared ( FIG. 2 : step S 10 ). Specifically, on the upper surface of the LCP base material  11 , the substrate wiring layer  12  (e.g., Cu/Ni/Au), which constitutes (i) a wiring part, (ii) a reception pad for receiving the IC chip, and (iii) an I/O pad to be connected with wiring, another substrate, and the like, is formed by a method such as plating. Further, the passivation layer  13  is formed on the upper surface of the LCP base material  11  so as to cover the wiring part, which is not externally connected, of the substrate wiring layer  12 . This state is illustrated in (a) of  FIG. 3 . 
     Subsequently, on the upper surface of the LCP base material  11  (the wiring substrate  10 ), a resin from which the posts  30  are to be made and which is in an uncured state prior to heating is applied to the central part and the vicinity thereof, which are not provided with the substrate wiring layer  12 , so that the resin is deposited so as to form post precursors  31  each having a columnar shape ( FIG. 2 : step S 11 , deposition step). Since the resin to be applied has a high thixotropy, application of the resin to the same position continuously or intermittently causes the resin to be deposited in a direction perpendicular to the upper surface while spread of the resin along the upper surface is suppressed. Thus, the columnar post precursors  31  are obtained. This state is illustrated in (b) of  FIG. 3 . Note that a method for applying the resin may be application with use of a dispenser, or application by an inkjet method or printing. 
     As for the IC chip  20 , the IC chip  20  illustrated in (c) of  FIG. 3 , which includes (i) the MMIC (not illustrated) provided on the back surface of the semiconductor base material  21 , (ii) the I/O pad  22 , (iii) the Cu pillar  23  provided on the I/O pads  22  and having a height of, for example, 25 μm to 50 μm, and (iv) the solder layer  24  (e.g., SnAg solder) provided at the tip of the Cu pillar  23 , is prepared ( FIG. 2 : step S 20 ). 
     Subsequently, flux is applied onto the solder layer  24  of the IC chip  20  so as to form the flux agent  25  ( FIG. 2 : step S 21 ). This state is illustrated in (d) of  FIG. 3 . 
     Then, to the upper surface of the wiring substrate  10 , on which the columnar post precursor  31  has been formed through the step S 11  of  FIG. 2 , the IC chip  20  formed through the step S 21  of  FIG. 2  is bonded (contact step). At this time, the tips of the columnar post precursors  31  come in contact with the terminal-less region of the IC chip  20 . This state is illustrated in (e) of  FIG. 3 . 
     Subsequently, reflow is carried out in a heated atmosphere ( FIG. 2 : step S 12 , heating step). In the heated atmosphere, the columnar post precursor  31  is gradually cured by heat so as to become the posts  30 , and also the solder layer  24  and the flux agent  25  of the IC chip  20  melt so as to be electrically connected to the reception pad of the substrate wiring layer  12  of the wiring substrate  10 . Note that the reflow may be carried out by heating through a stage on which the wiring substrate  10  is placed or heating through a tool holding the IC chip  20  and the like. 
     Then, at a step S 13  shown in  FIG. 2 , the heating is ended and cooling is performed (back to normal temperature) (cooling step). This causes the solder layer  24  and the flux agent  25  of the IC chip  20  to be cured while the solder layer  24  and the flux agent  25  are in contact with the reception pad of the substrate wiring layer  12  of the wiring substrate  10 . Thus, connection between the IC chip  20  and the substrate wiring layer  12  by soldering is completed. This state is illustrated in (f) of  FIG. 3 . 
     Through the flow described above, the electronic component-mounted body  1  in accordance with Embodiment 1 is completed. 
     Modified Example 1 
     Embodiment 1 described above has provided an example case in which the LCP base material  11  having a film-shaped is used, but the present invention is not limited to this. It is possible to employ a rigid substrate. Further, it is also possible to employ a substrate (base material) other than a liquid crystal polymer which substrate (base material) has an anisotropic linear expansion coefficient. Examples of a rigid substrate having an anisotropic linear expansion coefficient encompass a ceramic substrate, which is usable in the present invention. Further, it is possible to employ a substrate which is made of a material whose linear expansion coefficient is not anisotropic. 
     Note here that even in a case where the IC chip (electronic component) has a linear expansion coefficient which exceeds the wiring substrate to a relatively significant extent, the posts in accordance with an aspect of the present invention are cured at the time of melting of the solder and thus suppress expansion of the IC chip. As described above, the IC chip contracts after an end of reflow so as to return to or approximate to a state before the reflow. As such, in a case where expansion of the IC chip is suppressed by the posts, the IC chip contracts less after the end of the reflow as compared with a case in which the expansion is not suppressed by the posts. It is thus possible to reduce warpage of the wiring substrate caused by a contraction of the electronic component. 
     Modified Example 2 
     Although two posts  30  are distanced from each other in Embodiment 1 described above, the present invention is not limited to this and can employ a configuration in which two posts  30  are in contact with each other. 
     Furthermore, the number of positions at which the posts  30  are provided is not limited to two, but can be three or more. 
     Modified Example 3 
     In Embodiment 1 described above, formation of the post precursors  31  in the production flow shown in  FIG. 2  is performed in such a manner that a resin from which the posts  30  are to be made and which is in an uncured state is applied to the central part and the vicinity thereof, which are not provided with the substrate wiring layer  12 , of the upper surface of the LCP base material  11  (the wiring substrate  10 ). However, the present invention is not limited to this. It is possible to form post precursors by applying, to the terminal-less region of the IC chip  20 , a resin from which the posts  30  are to be made and which is in an uncured state. 
     Embodiment 2 
     The electronic component-mounted body in accordance with the present invention is not limited to the configuration illustrated in  FIG. 1  of the electronic component-mounted body  1  in accordance with Embodiment 1. For example, while the electronic component-mounted body  1  illustrated in  FIG. 1  has a configuration in which two posts  30  are arranged along the TD direction, it is possible to employ an alternative aspect described below. 
       FIG. 4  is a view schematically illustrating a configuration of an electronic component-mounted body  2  in accordance with Embodiment 2. (a) of  FIG. 4  is a top view of the electronic component-mounted body  2 , (b) of  FIG. 4  is a cross-sectional view taken along a line A-A′ in (a) of  FIG. 4 , and (c) of  FIG. 4  is a cross-sectional view taken along a line B-B′ in (a) of  FIG. 4 . For easy explanation, (a) of  FIG. 4  partially includes a transparent view. Further, for easy explanation, the same reference signs will be given to members having the same function as a member described in Embodiment 1, and descriptions on such a member will be omitted. 
     As illustrated in  FIG. 4 , in Embodiment 2, a single post  30   a  is provided in place of the two posts  30  in accordance with Embodiment 1. 
     Similarly to the posts  30  in accordance with Embodiment 1, the post  30   a  is a columnar structure which stands upright between a terminal-less region of an IC chip  20  and an upper surface of a wiring substrate  10  so as to be in contact, at a single position, with the terminal-less region and in contact, at a single position, with a region of the upper surface of the wiring substrate  10  which region faces the terminal-less region. However, the post  30   a  in accordance with Embodiment 2 differs from the two posts  30  in accordance with Embodiment 1 in being a single post  30   a  which has a shape of an ellipse having a long axis parallel to a TD direction of the wiring substrate  10  (an LCP base material  11 ) and a short axis parallel to an MD direction of the wiring substrate  10  (the LCP base material  11 ). 
     That is, between the IC chip  20  and the wiring substrate  10  (the LCP base material  11 ), the post  30   a  is in contact with the IC chip  20  and the LCP base material  11  across a wide width along the TD direction (a right-to-left direction of a drawing sheet of (b) of  FIG. 4 ) as illustrated in (b) of  FIG. 4  and in contact with the IC chip  20  and the LCP base material  11  across a small width along the MD direction (a right-to-left direction of a drawing sheet of (c) of  FIG. 4 ) as illustrated in (c) of  FIG. 4 . 
     Note that the post  30   a  is made of the same resin as that of the posts  30  in accordance with Embodiment 1. 
     Thus, a length of the post  30   a  in a contact region between the post  30   a  and the wiring substrate  10  (the LCP base material  11 ) is longer in a direction in which the LCP base material  11  has a greater linear expansion coefficient. This allows expansion of the wiring substrate  10  in the TD direction to be suppressed in a similar manner to Embodiment 1. 
     Embodiment 3 
     The electronic component-mounted body in accordance with the present invention is not limited to the configuration illustrated in  FIG. 1  of the electronic component-mounted body  1  in accordance with Embodiment 1. For example, while the electronic component-mounted body  1  illustrated in  FIG. 1  has a configuration in which two posts  30  are arranged along the TD direction, it is possible to employ an alternative aspect described below. 
       FIG. 5  is a top view schematically illustrating a configuration of an electronic component-mounted body  3  of Embodiment 3. For easy explanation,  FIG. 5  partially includes a transparent view. Further, for easy explanation, the same reference signs will be given to members having the same function as a member described in Embodiment 1, and descriptions on such a member will be omitted. 
     As illustrated in  FIG. 5 , in Embodiment 3, a single post  30   b  is provided in place of the two posts  30  in accordance with Embodiment 1. 
     Similarly to the posts  30  in accordance with Embodiment 1, the post  30   b  is a columnar structure which stands upright between a terminal-less region of an IC chip  20  and an upper surface of a wiring substrate  10  so as to be in contact with the terminal-less region and a region of the upper surface of the wiring substrate  10  which region faces the terminal-less region. However, the post  30   b  in accordance with Embodiment 3 differs from the two posts  30  in accordance with Embodiment 1 in having a shape of a cross when viewed from above. 
     More specifically, a contact surface of the post  30   b  in accordance with Embodiment 3, which contact surface is in contact with the upper surface of the wiring substrate  10 , has a shape of a cross that is a combination of (i) a first rectangle having a long side parallel to a TD direction and (ii) a second rectangle having a long side which is parallel to an MD direction and shorter than the long side of the first rectangle. Note that the post  30   b  is made of a resin which has properties identical to those of the posts  30  in accordance with Embodiment 1. 
     Thus, a length of the post  30   b  in a contact region between the post  30   b  and the wiring substrate  10  (the LCP base material  11 ) is the longest when measured along a direction in which a linear expansion coefficient of the LCP base material  11  is high. This allows expansion of the wiring substrate  10  in the TD direction to be suppressed in a similar manner to Embodiment 1. 
     Embodiment 4 
     The electronic component-mounted body in accordance with the present invention is not limited to the configuration illustrated in  FIG. 1  of the electronic component-mounted body  1  in accordance with Embodiment 1. For example, while the electronic component-mounted body  1  illustrated in  FIG. 1  has a configuration in which two posts  30  are arranged along the TD direction, it is possible to employ an alternative aspect described below. 
       FIG. 6  is a top view schematically illustrating a configuration of an electronic component-mounted body  4  of Embodiment 4. For easy explanation,  FIG. 6  partially includes a transparent view. Further, for easy explanation, the same reference signs will be given to members having the same function as a member described in Embodiment 1, and descriptions on such a member will be omitted. 
     As illustrated in  FIG. 6 , in Embodiment 4, five posts  30   c  are provided in place of the two posts  30  in accordance with Embodiment 1. 
     Similarly to the posts  30  in accordance with Embodiment 1, each of the posts  30   c  is a columnar structure which stands upright between a terminal-less region of an IC chip  20  and an upper surface of a wiring substrate  10  so as to be in contact with the terminal-less region and a region of the upper surface of the wiring substrate  10  which region faces the terminal-less region. However, the posts  30   c  in accordance with Embodiment 4 differ from the two posts  30  in accordance with Embodiment 1 in that the posts  30   b  are scattered on the upper surface of the wiring substrate  10  whereas the posts  30  are arranged on the same line along the TD direction. 
     As with the posts  30  in accordance with Embodiment 1, the posts  30   c  in accordance with Embodiment 4 allow a position of the wiring substrate  10  to be fixed at a contact portion between the wiring substrate  10  and a lower end of each of the posts  30   c  at a heating step of a reflow process during mounting. This suppresses expansion, caused by a linear expansion coefficient of the LCP base material  11 , of the wiring substrate  10  at the contact portion and a region around the contact portion. A similar effect is exhibited with respect to the IC chip  20 . The posts  30   c  allows a position of the IC chip  20  to be fixed at a contact portion between the IC chip  20  and an upper end of each of the posts  30   c  at the heating step of the reflow process during the mounting. This suppresses expansion, caused by a linear expansion coefficient of the IC chip  20 , of the IC chip  20  at the contact portion and a region around the contact portion. 
     Further, a positional arrangement of the posts  30   c  can be determined with a high degree of freedom in such a manner that the posts  30   c  can be provided at any positions in consideration of a functional surface of an integrated circuit (IC) included in the IC chip  20 , and can be provided so as to avoid a portion to be left as an open space among a space below the IC chip  20 . 
     Thus, Embodiment 4 makes it possible to achieve good flip chip mounting. 
     Embodiment 5 
     The semiconductor device in accordance with the present invention is not limited to the configuration illustrated in  FIG. 1  of the semiconductor device  1  in accordance with Embodiment 1. It is possible to employ an alternative aspect described below. 
       FIG. 7  is a cross-sectional view of an electronic component-mounted body  5  of Embodiment 5, the view corresponding to the electronic component-mounted body  1  illustrated in (b) of  FIG. 1 . 
     The electronic component-mounted body  5  in accordance with Embodiment 5 differs from the electronic component-mounted body  1  in accordance with Embodiment 1 in that a gap between the IC chip  20  and the wiring substrate  10  of the electronic component-mounted body  1  illustrated in (b) of  FIG. 1  is filled with underfill  40  (filler). 
     The underfill  40  may be a conventionally well-known underfill material, but preferably is an underfill material having a low parasitic capacitance since the IC chip  20  includes an MMIC. 
     The underfill  40  may be provided after the posts  30  are formed. At a point in time when the posts  30  are formed, the IC chip  20  and the wiring substrate  10  are connected to each other with an improved strength as compared with a case in which the posts  30  are not provided. Accordingly, there is a reduced risk of breakage during a period after the connection by soldering is carried out until the gap is filled with the underfill material. 
     Thus, the provision of the underfill  40  as described above makes it possible to provide an electronic component-mounted body  5  which enables an improvement in strength of bonding between the wiring substrate and the IC chip and, accordingly, enables an improvement in reliability at a connection part between the wiring substrate and the chip. 
     Note that the sealing with use of the underfill material described above is also applicable to the electronic component-mounted bodies  2  through  4  of Embodiments 2 through 4. 
     [Recap] 
     An electronic component-mounted body in accordance with an embodiment of the present invention is an electronic component-mounted body including: a wiring substrate; and an electronic component including a terminal connected to wiring of the wiring substrate by soldering, the electronic component being fixed to the wiring substrate with use of a post which is made of a thermosetting resin and not in contact with the wiring and the terminal. 
     The configuration above allows providing an electronic component-mounted body which enables prevention of defective mounting which is caused by a difference in linear expansion coefficient between the wiring substrate and the electronic component. 
     That is, the electronic component and the wiring substrate are made of respective different materials, and there is a difference in linear expansion coefficient between the electronic component and the wiring substrate. However, according to the configuration above, the electronic component and the wiring substrate are fixed by a post which is cured by heat for soldering of the electronic component and the wiring substrate. This allows expansion or contraction of one of the electronic component and the wiring substrate, which one has a linear expansion coefficient greater than that of the other, to be suppressed by expansion or contraction of the other. 
     As such, even in a case where the wiring substrate has a linear expansion coefficient greater than that of the electronic component and expands during reflow, the curing of the post at the time of melting of the solder allows suppressing expansion of the wiring substrate, so that warpage of the wiring substrate which is caused after an end of the reflow is suppressed. Further, even in a case where the wiring substrate contracts during reflow, the curing of the post at the time of melting of the solder allows suppressing the contraction, so that warpage of the wiring substrate which is caused after an end of the reflow is suppressed. Accordingly, when an attempt is made to cancel warpage of the wiring substrate by applying an external force, less stress is exerted on a soldered portion as compared with a case in which the warpage is greater. This allows reducing a risk of breakage of the soldered portion. 
     Further, according to an aspect of the present invention, the electronic component-mounted body may be further configured such that: the electronic component is an IC chip including a plurality of the terminals arranged in a peripheral part of a back surface of the IC chip; and the post is provided in a region surrounded by the plurality of the terminals. 
     The configuration above allows providing an electronic component-mounted body which enables prevention of defective mounting which is caused by a difference in linear expansion coefficient between the wiring substrate and the IC chip. 
     Note that the IC chip may be an MMIC chip which will be described later. 
     Further, according to an aspect of the present invention, the electronic component-mounted body may be further configured such that: a linear expansion coefficient of the wiring substrate with respect to a first direction parallel to a substrate surface of the wiring substrate is greater than a linear expansion coefficient of the wiring substrate with respect to a second direction which is parallel to the substrate surface and different from the first direction; and a width of a contact surface between the wiring substrate and the post as measured along the first direction is greater than a width of the contact surface as measured along the second direction. 
     The configuration above allows efficiently suppressing, with use of the post having a limited volume, expansion or contraction of the wiring substrate along the first direction which expansion or contraction may be caused during reflow. 
     Note that the contact surface of the post, which contact surface is in contact with the wiring substrate, may have a shape of (1) an ellipse having a long axis parallel to the first direction and a short axis parallel to the second direction or (2) a cross which is a combination of (i) a first rectangle having a long side parallel to the first direction and (ii) a second rectangle having a long side which is parallel to the second direction and has a length shorter than that of the long side of the first rectangle. 
     Further, according to an aspect of the present invention, the electronic component-mounted body may be further configured such that: the electronic component is fixed to the wiring substrate with use of not only the post but also another post which is made of a thermosetting resin and not in contact with the wiring and the terminal; a linear expansion coefficient of the wiring substrate with respect to a first direction parallel to a substrate surface of the wiring substrate is greater than a linear expansion coefficient of the wiring substrate with respect to a second direction which is parallel to the substrate surface and different from the first direction; and the post and the other post are arranged along the first direction. 
     The configuration above allows efficiently suppressing, with use of a limited number of posts, expansion or contraction of the wiring substrate along the first direction which expansion or contraction may be caused during reflow. 
     Further, according to an aspect of the present invention, the electronic component-mounted body may be further configured such that: the wiring substrate is a liquid crystal polymer substrate including (i) a liquid crystal polymer base material and (ii) wiring provided on a surface of the liquid crystal polymer base material; and the first direction and the second direction are a TD (transverse direction) direction and a MD (machine direction) direction, respectively, of the liquid crystal polymer base material. 
     The configuration above allows providing an electronic component-mounted body which enables prevention of defective mounting which is caused by a difference in linear expansion coefficient between the liquid crystal polymer substrate and the electronic component. 
     Further, according to an aspect of the present invention, the electronic component-mounted body may be further configured such that a gap between the electronic component and the wiring substrate is filled with a resin. 
     The configuration above allows providing an electronic component-mounted body which enables a further improvement of reliability of connection by soldering, since the resin with which the gap is filled increases strength of bonding between the electronic component and the wiring substrate. 
     Further, a method, in accordance with an aspect of the present invention, for manufacturing an electronic component-mounted body is a method for manufacturing an electronic component-mounted body including a wiring substrate and an electronic component, the method including: a deposition step of causing a thermosetting resin in an uncured state to be deposited (i) on the wiring substrate into a columnar shape without bringing the thermosetting resin into contact with wiring of the wiring substrate or (ii) on the electronic component into a columnar shape without bringing the thermosetting resin into contact with a terminal of the electronic component; a contact step of bringing the terminal of the electronic component into contact with the wiring via solder without bringing the thermosetting resin into contact with the terminal and the wiring; a heating step of heating the thermosetting resin and the solder so as to cure the thermosetting resin and also to melt the solder; and a cooling step of cooling the solder so as to cure the solder. 
     The configuration above allows providing an electronic component-mounted body which enables prevention of defective mounting which is caused by a difference in linear expansion coefficient between the wiring substrate and the electronic component. 
     That is, the electronic component and the wiring substrate are made of respective different materials, and there is a difference in linear expansion coefficient between the electronic component and the wiring substrate. However, according to the configuration above, the electronic component and the wiring substrate are fixed by a post which is cured by heat for soldering of the electronic component and the wiring substrate. This allows expansion or contraction of one of the electronic component and the wiring substrate, which one has a linear expansion coefficient greater than that of the other, to be suppressed by expansion or contraction of the other. 
     As such, even in a case where the wiring substrate has a linear expansion coefficient greater than that of the electronic component and expands during reflow, the curing of the post at the time of melting of the solder allows suppressing expansion of the wiring substrate, so that warpage of the wiring substrate which is caused after an end of the reflow is suppressed. Further, even in a case where the wiring substrate contracts during reflow, the curing of the post at the time of melting of the solder allows suppressing the contraction, so that warpage of the wiring substrate which is caused after an end of the reflow is suppressed. Accordingly, when an attempt is made to cancel warpage of the wiring substrate by applying an external force, less stress is exerted on a soldered portion as compared with a case in which the warpage is greater. This allows reducing a risk of breakage of the soldered portion. 
     The present invention is not limited to the embodiments, but can be altered by a skilled person in the art within the scope of the claims. An embodiment derived from a proper combination of technical means each disclosed in a different embodiment is also encompassed in the technical scope of the present invention. 
     REFERENCE SIGNS LIST 
     
         
           1 ,  2 ,  3 ,  4 ,  5 : electronic component-mounted body 
           10 : wiring substrate 
           11 : liquid crystal polymer base material (LCP base material) 
           12 : substrate wiring layer (wiring) 
           13 : passivation layer 
           13   a : opening 
           20 : IC chip (electronic component) 
           21 : semiconductor base material 
           22 : I/O pad (terminal) 
           23 : Cu pillar 
           24 : solder layer 
           25 : flux agent 
           30 ,  30   a ,  30   b ,  30   c : post 
           31 : post precursor (columnar post precursor) 
           40 : underfill (filler)