JP2005223090A - Connection structure of mounting substrate and component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection structure of a mounting substrate and a component with which advance of a crack is stopped on the way and it is prevented from being extended to a whole solder since the solder is divided into two or above regions, even if the crack occurs in the solder positioned between a terminal electrode of the component and a connection electrode of the mounting board. <P>SOLUTION: In the connection structure of the mounting substrate 61 and the component 51, the connection electrodes 21a formed on a component mounting face of the mounting substrate 61 are connected to the terminal electrodes 11a formed at four corners on a back of the component 51 through the solder parts 31a. At least on one side between a connection electrode 21a-side or a terminal electrode 11a-side, the solder 31a is divided into two or above regions in a direction where a diagonal line passing on the solder part 31a in diagonal lines at the back of the component. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a connection structure between a mounting board and components connected on the mounting board.

  In general, when a surface-mount type electronic component is mounted on a mounting board, the terminal electrode formed on the component side and the connection electrode formed on the mounting board side are connected via solder. The board on which the component-side terminal electrodes are formed is made of ceramic or the like having a relatively low thermal expansion coefficient, whereas the mounting board is often made of glass epoxy resin or the like having a relatively large thermal expansion coefficient. . At this time, due to the temperature change in the operating environment after becoming a product, a thermal stress is generated in the solder portion, which is a location where the two substrates are connected, due to the difference in the thermal expansion coefficient between the two substrates. In particular, a large thermal stress is generated in the solder portion located farthest from the center of the component.

  In recent years, mounting boards in which components are joined with solder are often mounted on set products that operate at high temperatures such as personal computers and automobiles. In addition, the use of the set product is repeated between operation and non-operation, and accordingly, the temperature change becomes severe, and thermal shock is repeatedly applied to the solder portion. Under these conditions, cracks are likely to occur in the solder portion, and there arises a problem that connection reliability is lowered, such as a problem that parts that should be mounted in the worst case are removed.

  The connection reliability problem is also affected by the metal component contained in the formed electrode. When soldering, the metal component contained in the electrode is dissolved in the solder part, and the vicinity of the electrode in the solder part contains a large amount of metal compound. In particular, among commonly used electrode materials, silver is easily dissolved in solder. Since the compound of silver and solder is weaker than the solder alone, cracks are likely to occur near the electrodes in the solder portion.

With respect to such problems, Patent Document 1 proposes a mounting substrate that increases connection strength by forming large-diameter electrodes at the four corners of the substrate.
Japanese Patent Laid-Open No. 2001-210749

  However, when forming a large-diameter electrode as proposed in Patent Document 1 is applied to a terminal electrode of a component mounted on a mounting substrate, the terminal electrode is proportional to increasing the connection strength of the terminal electrode. The area becomes large. For this reason, an empty area on the back side of the component is inevitably narrowed. Even if it is desired to form electrodes for other purposes in a narrow space, it is necessary to increase the size of the component board itself and increase the space. It becomes a factor to prevent.

  Further, when the terminal electrode area is changed, it is necessary to change the connection electrode area on the mounting board side of the connection destination so that the connection strength does not decrease. One change will affect the other, increasing the response to design changes.

  Therefore, an object of the present invention is to provide a connection structure between a mounting board and a component that can solve the above-described problems.

  In order to solve the above problems, the connection structure between the mounting board and the component according to the present invention includes a connection electrode formed on the component mounting surface of the mounting substrate and terminal electrodes formed at the four corners on the back surface of the component via the solder portion. The solder portion is divided into two or more regions in a direction in which a diagonal line passing over the solder portion of the diagonal lines on the component back surface extends on at least one side of the connection electrode side or the terminal electrode side. It is characterized by being.

  In the connecting structure between the mounting board and the component of the present invention, the solder portion is divided into two or more regions by providing a slit in at least one of the terminal electrode or the connecting electrode. To do.

  In the connection structure between the mounting substrate and the component according to the present invention, the solder portion is coated with a linear film on which at least one of the terminal electrode or the connection electrode does not adhere to the solder, so that two or more regions are formed. It is divided into two.

  In the connection structure between the mounting substrate and the component according to the present invention, the main component of the electrode on the side where the solder portion is divided into two or more regions is silver.

  Furthermore, in the connection structure between the mounting board and the component of the present invention, the connection electrode formed on the component mounting surface of the mounting substrate and the terminal electrode formed at the four corners on the back surface of the component are connected via the solder portion, A plurality of irregularities are formed on the surface of the terminal electrode.

  In the connection structure between the mounting substrate and the component of the present invention, the main component of the terminal electrode is silver.

  If the mounting structure of the mounting substrate and the component of the present invention is used, even if a crack is generated in the solder portion located between the terminal electrode of the component and the connecting electrode of the mounting substrate, the region where two or more solder portions exist Therefore, the progress of the crack can be stopped halfway, so that it does not spread to the entire solder part. As a result, components are not detached from the mounting board, and connection reliability is not lowered.

  In addition, since the present invention is characterized by the shape of the solder portion connecting both electrodes, the electrode formation region is not enlarged more than necessary, and even if the shape of one electrode is changed, the other electrode There is no need to change the shape.

  FIG. 1 is a perspective view showing a state in which components are mounted on a mounting board for explaining a first embodiment of the present invention. In general, a large number of components are mounted on the mounting board, but in FIG. 1, only one component 51 and a part of the mounting board 61 on which the component 51 is mounted are illustrated.

  In the component 51 shown in FIG. 1, terminal electrodes 11a mainly composed of silver are formed at the four corners of the back surface of the ceramic substrate. The back surface of the component 51 has a substantially rectangular shape. On the other hand, the mounting substrate 61 is made of glass epoxy resin, and a connection electrode 21a mainly composed of copper is formed on the component mounting surface. The terminal electrode 11a and the connection electrode 21a are connected via a solder portion 31a.

  FIG. 2 is an enlarged perspective view of the solder portion 31a and the mounting substrate 61 (including the connection electrode 21a) when it is assumed that the component 51 (including the terminal electrode 11a) is removed in FIG. In this state, it seems that the groove 32 is formed in the solder portion 31a, and the solder 31a is divided into two regions 34 and 35 on the terminal electrode 11a side with the groove 32 as a boundary. 2 corresponds to a diagonal line passing over the solder portion 31a among the diagonal lines connecting the four corners of the back surface of the component 51 shown in FIG. The arrow of the alternate long and short dash line D points in the direction away from the center of the component 51, and the solder portion 31a is divided into two regions in the direction in which the diagonal line extends. The solder portion 31a is not completely separated in these two regions, and solder is attached immediately below the groove 32, and the two regions are connected on the connection electrode 21a side.

  In this embodiment, a method of providing a slit in the terminal electrode 11a is used as a method for dividing the region of the solder portion 31a into two. FIG. 3 is a perspective view in which one of the four terminal electrodes 11a is enlarged by turning over the component 51 of FIG. According to FIG. 3, the terminal electrode 11 a is obtained by dividing the terminal electrode 11 a which originally was one region into two regions 16 and 17 by providing the slit 12. When the terminal electrode 11a divided into the two regions 16 and 17 is soldered to the connection electrode 21a, no solder adheres to the slit 12 portion, and the solder portion 31a has a groove 32 as shown in FIG. Will be divided into two areas.

  When the mounting substrate 61 mounted with the component 51 having such a connection structure is placed in an environment with a large temperature change, the difference in thermal expansion coefficient between the ceramic substrate of the component 51 and the mounting substrate 61 of glass epoxy resin is the same as in the past. As a result, thermal stress is generated in the solder portion 31a. As a result, a crack occurs in the solder portion 31a closer to the terminal electrode 11a from the corner farthest from the center of the component, and the crack progresses in the direction opposite to the arrow of the one-dot chain line D shown in FIG. .

  FIG. 4 is a cross-sectional view assuming that the component 51 shown in FIG. 1 after the generation of the crack is cut to the mounting substrate 61 along the two-dot chain line AA. A two-dot chain line AA is opposite to the diagonal line on the back surface of the substrate. According to FIG. 4, it is shown that a crack 33a is generated from the outside toward the inside in the solder portion 31a near the terminal electrode 11a. However, the crack 33 a does not spread to the entire area of the solder portion 31 a and stops at the groove 32. That is, the groove 32 functions so as to stop the progress of the crack 33 a halfway and not to spread to the region 35.

  FIG. 5 is a perspective view showing a state where components are mounted on a mounting board for explaining a second embodiment of the present invention. As in the first embodiment, one component 52 and a part of the mounting substrate 62 on which the component 52 is mounted are illustrated.

  In the component 52 shown in FIG. 5, terminal electrodes 11b mainly composed of copper are formed at the four corners of the back surface of the ceramic substrate. The back surface of the component 52 has a substantially rectangular shape. On the other hand, the material of the mounting substrate 62 is glass epoxy resin, and the connection electrode 21b mainly composed of silver is formed on the component mounting surface. The terminal electrode 11b and the connection electrode 21b are connected via a solder portion 31b.

  FIG. 6 is an enlarged perspective view of the solder portion 31b and the mounting substrate 62 (including the connection electrode 21b) when it is assumed that the component 52 (including the terminal electrode 11b) is removed in FIG. In this state, it seems that a hole 36 like a tunnel is formed in the solder part 31b, and the solder part 31b is divided into two regions 34 and 35 on the connection electrode 21b side with the hole 36 as a boundary. ing. Similar to the first embodiment, the regions 34 and 35 are divided into two regions in the extending direction of the diagonal line passing over the solder portion 31b among the diagonal lines connecting the four corners of the back surface of the component 52. The solder portion 31b is not completely separated in these two regions, solder is attached directly above the hole 36, and the two regions are connected on the terminal electrode 11b side.

  In this embodiment, a method of providing a slit in the connection electrode 11b is used as a method for dividing the region of the solder portion 31b into two. FIG. 7 is an enlarged perspective view of one connection electrode 21b formed on the mounting substrate 62 of FIG. According to FIG. 7, the connection electrode 21 b is obtained by dividing the connection electrode 21 b which originally was one region into two regions 18 and 19 by providing a slit 23. When the connection electrode 21b divided into the two regions 18 and 19 is soldered to the terminal electrode 11b, no solder adheres to the slit 23 portion, and the solder portion 31b has a hole 36 as shown in FIG. 6 as a boundary. Will be divided into two areas.

  When the mounting substrate 62 mounted with the component 52 having such a connection structure is placed in an environment with a large temperature change, a thermal stress is generated in the solder portion 32a as in the first embodiment. As a result, a crack is generated in the solder portion 31b closer to the connection electrode 21b from the corner farthest from the center of the component, and the crack progresses toward the inside of the solder portion 31b.

  FIG. 8 is a cross-sectional view assuming that the component 52 shown in FIG. 5 after the generation of the crack is cut up to the mounting substrate 62 along the two-dot chain line BB. A two-dot chain line BB is opposite to the diagonal line on the back surface of the substrate. According to FIG. 8, it is shown that a crack 33b is generated from the outside toward the inside in the solder portion 31b near the connection electrode 21b. However, the crack 33b does not extend to the entire area of the solder portion 31b, but stops at the hole 36. That is, the hole 36 functions so as to stop the progress of the crack 33b halfway and not to extend to the region 35.

  FIG. 9 is a perspective view showing a state where components are mounted on a mounting board for explaining a third embodiment of the present invention. As in the first embodiment, one component 53 and a part of the mounting substrate 63 on which the component 53 is mounted are illustrated.

  In a component 53 shown in FIG. 9, terminal electrodes 11a mainly composed of silver are formed at the four corners of the back surface of the ceramic substrate. The back surface of the component 53 has a substantially rectangular shape. On the other hand, the material of the mounting substrate 63 is glass epoxy resin, and the connection electrode 21b mainly composed of silver is formed on the component mounting surface in the same manner as the terminal electrode 11a. The terminal electrode 11a and the connection electrode 21b are connected via a solder portion 31c.

  FIG. 10 is an enlarged perspective view of the solder portion 31c and the mounting board 63 (including the connection electrode 21b) when it is assumed that the component 53 (including the terminal electrode 11a) is removed in FIG. In this state, it seems that a gap 37 is formed in the solder portion 31 c, and the solder portion 31 c is completely divided into two regions 34 and 35 with the gap 37 as a boundary. The regions 34 and 35 are divided into two regions in the direction in which the diagonal line passing over the solder portion 31 c extends among the diagonal lines connecting the four corners of the back surface of the component 53.

  In this embodiment, a method of providing slits in both the terminal electrode 11a and the connection electrode 11b is used as a method for completely dividing the region of the solder portion 31c into two.

  In FIG. 11, the mounting substrate 63 mounted with the component 53 having such a connection structure is placed in an environment with a large temperature change, and the component 53 shown in FIG. It is sectional drawing assumed that the mounting board | substrate 63 was cut | disconnected along. A two-dot chain line CC is opposed to a diagonal line on the back surface of the substrate. According to FIG. 11, it is shown that a crack 33c is generated in the solder portion 31c from the outside toward the inside. However, the crack 33 c does not spread to the entire area of the solder portion 31 c and stops at the gap 37. That is, the gap 37 functions so as to stop the progress of the crack 33c halfway and not spread to the region 35.

  In this embodiment, since silver is used for both the terminal electrode 11a and the connection electrode 21b, it cannot be predicted whether the position of the crack generated in the solder portion is closer to the terminal electrode 11a side or the connection electrode 21b side. . Thus, in order to reliably stop the progress even when the occurrence position of the crack cannot be predicted, it is preferable to completely separate the solder portion as in this embodiment.

  In the above embodiment, the slit is provided in at least one of the terminal electrode and the connection electrode so as to be divided into a rectangle in accordance with the shape of the electrode, but it may be a single straight slit as shown in FIG. Absent.

  FIG. 12 is a perspective view showing a state in which one straight slit 44 is formed in the terminal electrode 11e. A slit 44 is provided so as to connect the end face of the terminal electrode 11e formed on the substrate of the component 55 and the adjacent end face with one straight line, and the terminal electrode 11e is divided into two regions 16 and 17. When the terminal electrode 11e divided into the two regions 16 and 17 is soldered to the connection electrode, no solder adheres to the slit 44, and the solder portion is the solder portion of the diagonal line connecting the four corners of the back surface of the component. It will be divided into two regions in the direction in which the diagonal passing through the top extends. As a result, it is possible to form two separate solder portions that can stop the progress of cracks.

  In addition, a curved slit may be used instead of a straight line. It is not limited to the shape of the slit.

  In the above embodiment, the solder part is divided into two parts. However, among the diagonal lines connecting the four corners of the back surface of the component, the diagonal line passing over the solder part is further divided into three or more. It doesn't matter.

  In the above embodiment, as a method of dividing the solder part into a plurality of parts, a slit is provided in at least one of the terminal electrode and the connection electrode. However, a method of applying a linear film to which solder does not adhere is used. It doesn't matter.

  FIG. 13 is a perspective view showing a state in which a linear film 45 to which no solder adheres is applied to the terminal electrode 11f. A film 45 is provided on the terminal electrode 11 f formed on the substrate of the component 56, and the terminal electrode 11 f is divided into two regions 16 and 17. As a coating method of the film 45, for example, there is a method of screen printing a ceramic paste or the like.

  When the terminal electrode 11f divided into the two regions 16 and 17 is soldered to the connection electrode, the solder portion has two regions in the direction in which the diagonal line passing over the solder portion extends among the diagonal lines connecting the four corners of the back surface of the component. Even if cracks occur, the progress can be stopped.

  FIG. 14 is a cross-sectional view showing a state in which components are mounted on a mounting board for explaining a fourth embodiment of the present invention. In the component 54, terminal electrodes 11d mainly composed of silver are formed at the four corners of the back surface of the ceramic substrate. On the other hand, the material of the mounting substrate 64 is glass epoxy resin, and the connection electrode 21d mainly composed of copper is formed on the component mounting surface. The terminal electrode 11d and the connection electrode 21d are connected via a solder portion 31d.

  In this embodiment, the solder portion 31a is not divided into two regions as in the first embodiment, but a plurality of concave and convex portions 15 are formed on the surface of the terminal electrode 11d. Depending on the shape of the uneven portion 15 of the terminal electrode 11d, the shape of the surface of the solder portion 31d is necessarily uneven.

  In order to form a plurality of projections and depressions on the surface of the terminal electrode 11d as shown in FIG. 14, for example, the screen mesh used for screen printing of the electrode paste to be the terminal electrode 11d is made a polka dot pattern, The amount of electrode paste applied can be controlled by a method.

  FIG. 14 also shows a state after the mounting substrate 64 mounted with the component 54 having such a connection structure is placed in an environment with a large temperature change and a crack is generated. The crack 33d is generated from the corner farthest from the center of the component on the terminal electrode 11d side, and proceeds toward the inside of the solder portion 31d along the surface shape of the terminal electrode 11d. However, the crack 33d does not extend to the entire area of the solder portion 31d, but stops at the uneven portion 15 of the terminal electrode 31d. That is, the uneven portion 15 functions to stop the progress of the crack 33d halfway.

It is a perspective view which shows the state in which components are mounted on the mounting board | substrate for demonstrating the 1st Example of this invention. It is an expansion perspective view of the solder part of FIG. It is the perspective view which turned over the components of FIG. 1 and expanded the terminal electrode. FIG. 2 is a cross-sectional view assuming that a part from one corner of the component shown in FIG. 1 is cut to a mounting board along a diagonal line. It is a perspective view which shows the state in which components are mounted on the mounting board | substrate for demonstrating the 2nd Example of this invention. FIG. 6 is an enlarged perspective view of the solder portion of FIG. 5. It is the perspective view which expanded the connection electrode of FIG. FIG. 6 is a cross-sectional view assuming that a part from one corner of the component shown in FIG. 5 to a mounting board is cut along a diagonal line. It is a perspective view which shows the state in which components are mounted on the mounting board | substrate for demonstrating the 3rd Example of this invention. FIG. 10 is an enlarged perspective view of the solder portion of FIG. 9. FIG. 10 is a cross-sectional view assuming that the component shown in FIG. 9 is cut from one corner to a mounting board along a diagonal line. It is a perspective view of the terminal electrode for showing the modification of the shape of a slit. It is a perspective view of the terminal electrode in which the linear film | membrane which solder does not adhere is formed. It is sectional drawing which shows the state in which components are mounted on the mounting board | substrate for demonstrating the 4th Example of this invention.

Explanation of symbols

11a to 11f Terminal electrode 12, 23, 44 Slit 15 Concave portion 16, 17 Terminal electrode region 18, 19 Connection electrode region 21a, 21b, 21d Connection electrode 31a to 31d Solder portion 32 Groove 33a to 33d Crack 34, 35 Solder Part area 36 hole 37 gap 45 linear film to which solder does not adhere 51-56 parts 61-64 mounting board

Claims (6)

In the connection structure of the mounting substrate and the component in which the connection electrodes formed on the component mounting surface of the mounting substrate and the terminal electrodes formed at the four corners on the back surface of the component are connected via the solder portion,
The solder portion is divided into two or more regions in a direction in which a diagonal line passing over the solder portion of diagonal lines on the component back surface extends on at least one side of the connection electrode side or the terminal electrode side. A connection structure between a mounting board and a component. 2. The connection structure between a mounting board and a component according to claim 1, wherein the solder portion is divided into two or more regions by providing a slit in at least one of the terminal electrode or the connection electrode. . 2. The solder part according to claim 1, wherein the solder part is divided into two or more regions by applying a linear film to which solder does not adhere to at least one of the terminal electrode or the connection electrode. Connection structure between mounting board and components. 4. The connection structure between a mounting board and a component according to claim 1, wherein a main component of the electrode on the side where the solder portion is divided into two or more regions is silver. . In the connection structure of the mounting substrate and the component in which the connection electrodes formed on the component mounting surface of the mounting substrate and the terminal electrodes formed at the four corners on the back surface of the component are connected via the solder portion,
A connection structure between a mounting substrate and a component, wherein a plurality of concave and convex portions are formed on a surface of the terminal electrode. 6. The connection structure between a mounting board and a component according to claim 5, wherein a main component of the terminal electrode is silver.

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