JP2008205064A - Electronic component mounting structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic component mounting structure which stabilizes the position of an electronic component and hardly allows the breakage of a connection material to occur. <P>SOLUTION: Recessions 3 each having an opening partially overlapping a terminal electrode 1a are formed on the upper surface of a circuit board 2 carrying an electronic component 1. A main electrode pad 4 counter to the terminal electrode 1a partially overlapping the opening is formed on the bottom face of each recession 3. Auxiliary electrode pads 5 each adjacent to the recession 3 and counter to the terminal electrode 1a are formed on the upper surface of the circuit board 2. A main conductive connection material 6 connecting the main electrode pad 4 to the terminal electrode 1a partially overlapping the opening is disposed in each recession 3. The auxiliary electrode pad 5 is connected to the terminal electrode 1a with an auxiliary connection material 7. In this mounting structure, distortion per unit area of the main conductive connection material 6 reduces and the presence of the auxiliary electrode pad 5 stabilizes the mounting position of the electronic component 1. This lowers a probability of the occurrence of breakage of the main conductive connection material 6 and a possibility of a wide shift of the mounting position. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mounting structure for an electronic component in which an electronic component such as a chip capacitor is mounted on a circuit board using a connecting material such as solder.

  In an electronic component mounting structure in which an electronic component such as a chip capacitor is mounted on a circuit board using a connecting material such as solder, the thermal expansion coefficient differs between the electronic component and the circuit board. Depending on the temperature change due to heat generation of electronic parts, the connecting material is distorted internally due to the difference in the amount of thermal expansion and contraction, thereby connecting the connecting material, the boundary between the connecting material and the electronic component, or connecting In some cases, cracks and fractures occurred near the boundary between the material and the electrode pad. In particular, when used in harsh conditions such as in-vehicle applications, the amount of thermal expansion and contraction of solder, electronic components, and circuit boards used as connecting materials increases because the temperature change range is wide, The amount of strain generated in the solder increases, and the probability of breakage increases.

  As a conventional electronic component mounting structure, for example, a spacer is disposed between the electronic component and the circuit board, and the terminal electrode formed on the lower surface of the electronic component and the electrode pad on the circuit board are soldered. A mounting structure of connected electronic components is known (see, for example, Patent Document 1).

According to this conventional electronic component mounting structure, since the distance between the electrode pad and the terminal electrode is increased by the spacer, the strain per unit volume of the solder is reduced, and the probability of occurrence of breakage can be reduced. Is.
Japanese Patent Laid-Open No. 11-163510

  However, in the case of the conventional electronic component mounting structure described above, there is a problem in that the number of steps increases because a spacer must be disposed between the circuit board and the electronic component. In addition, since the spacer is disposed between the circuit board and the electronic component, the electronic component is placed on the spacer in the mounting process. In such a state, the electronic component is easily tilted. There was also a problem that the mounting position at the time of connection was easily shifted.

  Further, in the mounting process, the distance between the terminal electrode and the electrode pad becomes long, so that the amount of solder formed between the terminal electrode and the electrode pad increases, and this causes variation in the amount of solder formed. Therefore, when the solder is melted, the force with which the terminal electrode is pulled by the solder becomes large, and there is a problem that the position of the electronic component is easily displaced after mounting.

  The present invention has been devised in view of the problems in the conventional electronic component mounting structure as described above, and its purpose is to stabilize the position of the electronic component while preventing breakage of the connecting material. To provide a mounting structure.

  The electronic component mounting structure of the present invention includes an electronic component having a terminal electrode formed on a lower surface, a circuit board on which the electronic component is mounted, an upper surface of the circuit board, and a portion of an opening formed on the terminal electrode. A concave portion that overlaps with the main electrode pad that is formed on the bottom surface of the concave portion and is opposed to the terminal electrode that overlaps a part of the opening, and is formed on the upper surface of the circuit board adjacent to the concave portion, An auxiliary electrode pad facing the terminal electrode, a main conductive connecting material disposed in the recess and connecting the main electrode pad and the terminal electrode overlapping with a part of the opening; and the auxiliary An auxiliary connecting material for connecting the electrode pad and the terminal electrode is provided.

  The electronic component mounting structure of the present invention is characterized in that, in the above configuration, a plurality of the concave portions are formed for one electronic component.

  The electronic component mounting structure of the present invention is characterized in that, in the above configuration, a plurality of the main electrode pads are formed in the recess.

  In the electronic component mounting structure according to the present invention, the main electrode pad corresponding to the terminal electrode formed in one electronic component is formed in one concave portion in the above configuration. Is.

  According to the electronic component mounting structure of the present invention, the recess is formed on the upper surface of the circuit board so that a part of the opening overlaps the terminal electrode, and the main electrode pad and the terminal electrode formed on the bottom surface of the recess are mainly formed. Since it is connected by the conductive connecting material, the distance between the terminal electrode and the main electrode pad is increased by the recess, and the distortion per unit volume of the main conductive connecting material is reduced, so that the main conductive connecting material is broken. Can be difficult to occur. In addition, the amount of the main conductive connection material formed between the terminal electrode and the main electrode pad is increased and tends to vary, and the variation in the force with which the terminal electrode is pulled by the main conductive connection material is increased. However, according to the electronic component mounting structure of the present invention, the auxiliary electrode pads formed adjacent to the recesses on the upper surface of the circuit board and the terminal electrodes are connected by the auxiliary connecting material, and these auxiliary electrode pads are connected. Since the distance between the terminal electrode and the terminal electrode is short, the amount of the auxiliary connection material is small and difficult to vary, and the variation in the force with which the terminal electrode is pulled by the auxiliary connection material is small. It can be. That is, according to the electronic component mounting structure of the present invention, the main conductive connecting material can be hardly broken while the position of the electronic component is stabilized by the auxiliary connecting material. Since the recess can be easily formed at the time of manufacturing the circuit board, the number of steps in the mounting process is not increased.

  Further, according to the electronic component mounting structure of the present invention, when a plurality of recesses are formed for one electronic component, the side walls of the recesses exist between the main conductive connecting members. An electronic component mounting structure in which electrical shorting between electrode pads is unlikely to occur is obtained.

  Also, according to the electronic component mounting structure of the present invention, when a plurality of main electrode pads are formed in the recess, the distance between the main electrode pads can be shortened and the main electrode pads can be arranged at high density. Therefore, it is possible to mount an electronic component in which the terminal electrodes are arranged with high density and the space between the terminal electrodes is narrow.

  According to the electronic component mounting structure of the present invention, when the main electrode pad corresponding to the terminal electrode formed in one electronic component is formed in one recess, the number of recesses formed in the circuit board is reduced. Since the number of the electronic components can be reduced, the electronic components mounted by the electronic component mounting structure of the present invention can be made dense on the circuit board.

  Hereinafter, the electronic component mounting structure of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an external perspective view showing an example of an embodiment of an electronic component mounting structure according to the present invention, and FIG. 2 is a cross-sectional view taken along the line A-A 'of FIG. The electronic component mounting structure shown in these drawings has a basic configuration in which the terminal electrode 1a formed on the lower surface of the electronic component 1 is connected to the main circuit board 2 via the main conductive connecting material 6 and the auxiliary connecting material 7. The electrode pad 4 and the auxiliary electrode pad 5 are connected.

  The electronic component 1 having the terminal electrode 1a formed on the lower surface is a chip electronic component such as a chip capacitor formed by laminating a plurality of dielectric layers mainly composed of barium titanate, and includes a plurality of ceramic green sheets. What was produced by laminating and firing is used. As the terminal electrode 1a of the chip capacitor, for example, a nickel conductor film and a tin conductor film formed by plating on a copper conductor film obtained by baking a copper paste obtained by dispersing copper powder and an organic binder in an organic solvent is used. It is done. In the case of a rectangular parallelepiped chip capacitor, the terminal electrode 1a of the electronic component 1 in the electronic component mounting structure of the present invention is continuous from both end surfaces of the main body to a part of the four adjacent side surfaces including the lower surface. It is formed as follows.

  The circuit board 2 on which the electronic component 1 is mounted is, for example, an organic multilayer circuit board made of polyimide resin, glass epoxy resin, or the like. And the recessed part 3 is formed in the upper surface of the circuit board 2 so that a part of opening of the recessed part 3 may overlap with a part of terminal electrode 1a when the electronic component 1 is mounted. The recess 3 is formed so as to penetrate at least one insulating layer from the upper surface of the circuit board 2. The depth is set to, for example, 50 to 200 μm so as to secure a distance between the terminal electrode 1a and the main electrode pad 4 so that the main conductive connecting member 6 does not break.

  In the electronic component mounting structure of the present invention, the main electrode pad 4 and the auxiliary electrode pad 5 are connected to the terminal electrode 1a on the circuit board 2 side.

  The main electrode pad 4 is formed on the bottom surface of the recess 3 and faces a part of the terminal electrode 1a overlapping with a part of the opening of the recess 3, and is, for example, a copper conductor film formed to a thickness of 5 to 15 μm And the surface is covered with a preflux film.

  The auxiliary electrode pad 5 is formed on the upper surface of the circuit board 1 adjacent to the recess 3 and faces another part protruding from the opening of the recess 3 of the terminal electrode 1a. The same is used.

  In the electronic component mounting structure of the present invention, the terminal electrode 1a is connected to the main electrode pad 4 by the main conductive connecting material 6 and is connected to the auxiliary electrode pad 5 by the auxiliary connecting material 7.

  The main conductive connecting material 6 is disposed in the recess 3 and connects a part of the terminal electrode 1a that overlaps a part of the opening of the recess 3 to the main electrode pad 4, and the material is, for example, solder or the like The brazing material is used.

  The auxiliary connection member 7 connects the other part of the terminal electrode 1 a protruding from the opening of the recess 3 and the auxiliary electrode pad 5. Usually, the same material as the main conductive connecting material 6 is used as the material, but the auxiliary connecting material 7 may not require electrical conductivity in particular, so a resin adhesive having a different material and not having electrical conductivity. Etc. may be used.

  The electronic component mounting structure of the present invention as described above can be obtained by the following method. First, a solder paste in which solder powder and flux are dispersed in an organic solvent is applied on the main electrode pad 4 and the auxiliary electrode pad 5. Next, in the electronic component 1, a part of the terminal electrode 1a and the main electrode pad 4 are opposed to each other through the solder paste, and another part of the terminal electrode 1a is opposed to the auxiliary electrode pad 5 through the solder paste. In this way, it is placed on the circuit board 2. Then, by heating the solder paste, the main conductive connecting material 6 is formed between a part of the terminal electrode 1a and the main electrode pad 4, and the two are connected to each other. An auxiliary connecting material 7 is formed between the electrode pads 5 and both are connected. Thus, when the main conductive connecting material 6 and the auxiliary connecting material 7 are made of the same material, they can be formed simultaneously.

  According to the electronic component mounting structure of the present invention, the concave portion 3 is formed on the upper surface of the circuit board 2 so that a part of the opening overlaps the terminal electrode 1 a of the electronic component 1, and the main portion formed on the bottom surface of the concave portion 3. Since the electrode pad 4 and the terminal electrode 1a are connected by the main conductive connecting material 6, the distance between the terminal electrode 1a and the main electrode pad 4 is increased, and the thermal expansion of the electronic component 1 and the circuit board 2 is achieved. In addition, since the strain per unit volume of the main conductive connecting member 6 due to heat shrinkage is reduced, the main conductive connecting member 6 can be hardly broken. On the other hand, the amount of the main conductive connecting material 6 formed between the terminal electrode 1a and the main electrode pad 4 increases and tends to vary, and the variation in force with which the terminal electrode 1a is pulled by the main conductive connecting material 6 is increased. However, according to the electronic component mounting structure of the present invention, the auxiliary electrode pad 5 formed adjacent to the recess 3 on the upper surface of the circuit board 2 and the terminal electrode 1a opposed thereto are provided. Since the distance between the two is short, the amount of the auxiliary connecting material 7 is small and difficult to vary, and the variation in the force with which the terminal electrode 1a is pulled by the auxiliary connecting material 7 is reduced. It can be difficult. That is, according to the electronic component mounting structure of the present invention, the main conductive connecting member 6 can be hardly broken while the position of the electronic component 1 is stabilized. In addition, since the recessed part 3 can be easily formed at the time of manufacture of the circuit board 2, the man-hour in a mounting process does not increase collectively.

  As shown in FIGS. 1 and 2, when a plurality of recesses 3 are formed for one electronic component 1, the recesses 3 are interposed between the main conductive connecting members 6 arranged in the respective recesses 3. Therefore, an electronic component mounting structure in which electrical short-circuiting between the main electrode pads 4 due to the contact between the main conductive connecting members 6 is less likely to occur.

  Thus, since the electronic component mounting structure of the present invention has high reliability and stable characteristics, for example, a circuit device incorporated in a computer, a communication device, various household electric devices, an in-vehicle circuit unit, or the like. Adopted.

  It should be noted that the present invention is not limited to the embodiments described above, and various modifications and improvements can be made without departing from the scope of the present invention.

  For example, in the example of the electronic component mounting method of the present invention described above, a chip capacitor is used as the electronic component 1, but the electronic component 1 is not limited to this, for example, on a substrate such as an alumina base. The present invention can also be applied when using a chip resistor in which a resistor mainly composed of ruthenium oxide or the like is formed.

  In the example of the electronic component mounting structure of the present invention described above, the main electrode pad 4 and the auxiliary electrode pad 5 connected to the same terminal electrode 1a are electrically connected by wiring inside the circuit board 2. It doesn't matter. Further, the auxiliary electrode pad 5 may be a so-called dummy electrode pad that is not connected to the wiring inside the circuit board 2.

  In the example of the electronic component mounting structure of the present invention described above, the main conductive connecting material 6 and the auxiliary connecting material 7 are made of the same material, but the present invention is not limited to this. You may form using a conductive resin as a material of either one of connection materials. Further, when the auxiliary electrode pad 5 is a so-called dummy electrode pad, a resin adhesive having no conductivity may be used for the auxiliary connecting material 7.

  Further, in the example of the electronic component mounting method of the present invention described above, the terminal electrodes 1a are formed one by one at both ends of the electronic component 1, but for example, FIG. 3 shows the electronic component mounting structure of the present invention. As shown in an external perspective view of another example of this embodiment, an electronic component 31 having a plurality of terminal electrodes 32a formed on one side surface may be used. In this example, as shown in FIG. 3, the circuit board is formed with a recess 33 corresponding to each terminal electrode 32a, and faces the terminal electrode 31a that overlaps a part of the opening on the bottom surface of the recess 33. A main electrode pad (not shown) is formed, an auxiliary electrode pad (not shown) is formed on the upper surface of the circuit board adjacent to the recess 33 and facing the terminal electrode 31a, and the main electrode pad And a terminal electrode 31a that overlaps a part of the opening of the recess 33 is disposed in the recess 33, and an auxiliary connection material (not shown) that connects the auxiliary electrode pad and the terminal electrode 31a. Z) is arranged.

  Furthermore, in the example of the electronic component mounting method of the present invention described above, a plurality of recesses 3 are formed in the circuit board 2 for one electronic component 1, but for example, as shown in FIGS. A structure is also possible.

  4 is an external perspective view showing still another example of the embodiment of the electronic component mounting structure according to the present invention, and FIG. 5 is a cross-sectional view taken along line B-B ′ of FIG. 4. When the plurality of main electrode pads 44 corresponding to the plurality of terminal electrodes 41a formed on one electronic component 41 are formed in one recess 43 as in the example of the electronic component mounting structure shown in these drawings. Since the number of recesses 43 formed on the circuit board 42 can be reduced, the area occupied by the electronic component mounting structure can be reduced, and the mounting structure can be arranged at high density.

  Further, when a plurality of main electrode pads 44 are formed in the recess 43 as in the example of the electronic component mounting structure shown in FIGS. 4 and 5, the distance between the adjacent main electrode pads 44 may be shortened. Since the main electrode pads 44 can be arranged with high density, it is possible to mount the electronic component 41 in which the terminal electrodes 41a are arranged with high density and the space between the terminal electrodes 41a is narrow.

  1 and 2, a circuit board 2 having a recess 3 is prepared, a sample in which the electronic part 1 is mounted on the circuit board 2 is prepared, and a temperature cycle is performed. The appearance of the connecting material after the test was confirmed.

  As the electronic component 1, a chip capacitor having a length of 2.0 mm × width of 1.2 mm × height of 1.2 mm made of a dielectric material mainly composed of barium titanate was used. As the terminal electrode 1a, a copper conductor film baked and having a nickel conductor film and a tin conductor film formed thereon was used.

  As the circuit board 2, an organic multilayer circuit board having a dimension of 60 mm long × 40 mm wide × 0.7 mm thick formed by laminating a plurality of insulating layers of polyimide resin each having a thickness of 25 μm was used. The recesses 3 are formed so that the number of insulating layers penetrating from the upper surface of the circuit board 2 is 1 layer, 2 layers, 4 layers, 6 layers, and 8 layers, respectively, and the depths of the formed recesses 3 are 25 respectively. , 50, 100, 150, 200 μm.

  As a comparative example, a sample in which the electronic component 1 was mounted on a conventional circuit board to which a conventional electronic component mounting structure in which no concave portion was formed was applied. The electrode pads to which the terminal electrodes 1a are connected are arranged at the same positions as the main electrode pads 4 and the auxiliary electrode pads 5 of the circuit board 2 of the embodiment in plan view from the upper surface side of the circuit board.

  A solder paste of 96% tin, 3% silver, 0.5% copper was applied to the main electrode pad 4 and the auxiliary electrode pad 5 of the circuit board 2 in the electronic component mounting structure of the present invention. Then, the electronic component 1 is placed on the circuit board 2 so that a part of the terminal electrode 1a and the main electrode pad 4 face each other, and another part of the terminal electrode 1a faces the auxiliary electrode pad 5. Then, by heating, a main conductive connecting material 6 is formed between a part of the terminal electrode 1a and the main electrode pad 4 by solder paste to connect the two, and another part of the terminal electrode 1a and the auxiliary electrode pad The auxiliary connecting material 7 was formed between the two and the two were connected. Also, the same solder paste as in the example is applied to the electrode pads of the circuit board to which the conventional electronic component mounting structure as a comparative example is applied, and the electronic component 1 is placed at the same position as in the example and heated. Then, a connecting material was formed between the terminal electrode 1a and the electrode pad, and both were connected.

Fourteen samples of Examples and Comparative Examples thus prepared were prepared, and a temperature cycle test was performed on the connecting materials. In the temperature cycle test, one cycle was made by continuously standing at 125 ° C. for 30 minutes and standing at −40 ° C. for 30 minutes. Table 1 shows the results of confirming the number of cracks and the number of fractures after performing this temperature cycle test for 1000, 2000, and 3000 cycles for each sample.

  As can be seen from the results shown in Table 1, in the sample of the comparative example in which the recess 3 was not formed, the connecting material was broken after 2000 cycles, but for the sample of the example in which the recess 3 was formed with a depth of 25 μm or more, After 2000 cycles, the connecting material did not break. And about the sample of the Example which made the depth of the recessed part 3 100 micrometers or more, the fracture | rupture of the connection material did not generate | occur | produce after 3000 cycles. In addition, a large shift in the mounting position of the electronic component 1 was not found in any of the examples.

  That is, according to the electronic component mounting structure of the present invention, the distance between the terminal electrode 1a and the main electrode pad 4 is increased, and the distortion per unit volume of the main conductive connecting material 6 is reduced. It was confirmed that the probability of breakage due to thermal expansion and contraction of the component 1 and the circuit board 2 can be extremely reduced. Further, there is an auxiliary electrode pad 5 formed adjacent to the recess 3 on the upper surface of the circuit board 2, and the auxiliary electrode pad 5 and another part of the terminal electrode 1 a are connected by the auxiliary electrode material 7. Since the distance between the auxiliary electrode pad 5 formed on the upper surface of the circuit board 2 and the terminal electrode 1a is shortened, the mounting position of the electronic component 1 is fixed thereby, and the temperature cycle load is reduced. However, it was confirmed that the mounting position of the electronic component 1 was stable.

It is an external appearance perspective view which shows an example of embodiment of the mounting structure of the electronic component of this invention. FIG. 2 is a cross-sectional view taken along line A-A ′ of FIG. 1. It is an external appearance perspective view which shows the other example of embodiment of the mounting structure of the electronic component of this invention. It is an external appearance perspective view which shows the further another example of embodiment of the mounting structure of the electronic component of this invention. FIG. 5 is a sectional view taken along line B-B ′ of FIG. 4.

Explanation of symbols

1,31,41 ... Electronic components 1a, 31a, 41a ... Terminal electrode 2,42 ... Circuit board 3,33,43 ... Recess 4,44 ... Main electrode pad 5,45 ..Auxiliary electrode pads 6,46 ... Main conductive connection material 7,47 ... Auxiliary connection material

Claims (4)

  An electronic component having a terminal electrode formed on the lower surface, a circuit board on which the electronic component is mounted, a recess formed on the upper surface of the circuit board, a portion of the opening overlapping the terminal electrode, and a bottom surface of the recess A main electrode pad facing the terminal electrode formed and overlapping a part of the opening, and an auxiliary electrode formed on the upper surface of the circuit board adjacent to the recess and facing the terminal electrode A main conductive connecting material that connects the pad, the main electrode pad and the terminal electrode that overlaps a part of the opening, and the auxiliary electrode pad and the terminal electrode, which are disposed in the recess. An electronic component mounting structure comprising an auxiliary connecting material.   The mounting structure for an electronic component according to claim 1, wherein a plurality of the concave portions are formed for one electronic component.   2. The electronic component mounting structure according to claim 1, wherein a plurality of the main electrode pads are formed in the recess.   4. The electronic component mounting structure according to claim 3, wherein the main electrode pad corresponding to the terminal electrode formed in one electronic component is formed in one concave portion.

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