JP2012054417A - Mounting structure of electronic component and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mounting structure of an electronic component in which impact of heat shrinkage in hardening of reinforcement resin can be minimized when soldering and thermal hardening of the reinforcement resin are carried out in the same heating process.SOLUTION: A mounting structure 1 of an electronic component comprises a printed board 2, an electronic component 4 having a square plane mounted on the printed board 2 with solder balls 3 interposed therebetween, and reinforcement resin 5 applied and formed across the printed board 2 and the electronic component 4. When viewed from a normal direction of the upper surface of the electronic component 4, the reinforcement resin 5 is applied and formed clockwise along each side starting from each corner of the upper surface of the electronic component 4 with a length not reaching the adjacent corner.

Description

  The present invention relates to a mounting structure in which an electronic component, in particular, a solder bump connection type electronic component is mounted on a printed circuit board, and a manufacturing method thereof.

  In recent years, electronic devices have been remarkably multifunctional, and demands for miniaturization and weight reduction are very high. Therefore, electronic components mounted on printed circuit boards are replaced with lead-connected electronic components such as quad flat packages (QFP), BGA packages, chip size packages (CSP (Chip Size Package)). Many solder bump connection type electronic components are used. However, mobile devices that are assumed to be carried by people are required to have high reliability against impacts such as dropping due to carelessness of the user. In general, in a mounting structure for a solder bump connection type electronic component such as a BGA package or a CSP, an impact is directly transmitted to the solder connection portion. Therefore, mounting of a lead connection type electronic component having a stress relaxation function by a lead is possible. The reliability of electrical connection is inferior compared to the structure. Therefore, various reinforcements are made to improve the reliability of the electrical connection. In particular, there are many cases where so-called underfill resin reinforcement or side fill resin reinforcement is performed, in which a thermosetting resin is injected between an electronic component and a printed circuit board for reinforcement.

  Conventionally, a technique has been proposed that enables the production efficiency to be improved by enabling the soldering and the thermosetting of the reinforcing resin to be performed in the same heating process (for example, see Patent Document 1). . In this case, as the reinforcing resin, the soldering portion reaches the solder melting temperature so that the soldering is not hindered by its hardening, and solder bonding is performed, and the solder ball of the solder connection portion sinks due to the weight of the electronic component, Resins are used that have the property of starting to cure after the soldering process is complete. Thereby, the heating process of the reinforcing resin can be reduced from two processes of applying the heating and soldering reflow to the soldering reflow and heating and curing, thereby reducing the number of steps.

Japanese Patent Laid-Open No. 11-204568

  However, depending on the shape of the application pattern of the reinforcing resin, either the warpage of the package of the electronic component or the warpage of the printed circuit board occurs due to the heat shrinkage at the time of hardening of the reinforcing resin, and in conjunction with these warpages, For example, when the gap between the package and the printed circuit board is shorter than the diameter of the solder ball, the sinking of the solder ball at the solder connection portion is promoted. As a result, the connection stress is stored as an internal stress in the solder connection part, or the solder ball deforms in a distorted manner, resulting in a short-circuit failure between adjacent solder balls. This will impede process stability. Conversely, if the gap between the package and the printed circuit board is longer than the diameter of the solder ball, the soldering becomes unstable, causing a solder failure.

  The present invention has been made to solve the above-mentioned problems in the prior art, and reduces the influence of thermal shrinkage during curing of the reinforcing resin when performing soldering and thermal curing of the reinforcing resin in the same heating process. An object of the present invention is to provide an electronic component mounting structure that can be suppressed and a method for manufacturing the same.

  In order to achieve the above object, a structure of an electronic component mounting structure according to the present invention includes a printed circuit board, an electronic component having a substantially rectangular planar shape mounted on the printed circuit board via solder, and the printed circuit board. A mounting structure for an electronic component comprising a reinforcing resin formed over both the substrate and the electronic component, and when viewed from the normal direction of the upper surface of the electronic component, the reinforcing resin is Each electronic component is formed with a length that does not reach the adjacent corner portion clockwise or counterclockwise along each side starting from each corner portion of the upper surface of the electronic component.

  According to the configuration of the electronic component mounting structure, the reinforcing resin is formed along only one side of each L-shaped corner portion of the upper surface of the electronic component when viewed from the normal direction of the upper surface of the electronic component. Therefore, when the soldering and the thermosetting of the reinforcing resin are performed in the same heating process, it is possible to suppress the influence of the thermal shrinkage when the reinforcing resin is cured. As a result, it is possible to prevent the warpage of the package of the electronic component and the warpage of the printed circuit board, and to prevent the solder balls from sinking in the solder connection portion. As a result, the connection stress is stored as an internal stress in the solder connection part, or the solder ball deforms in a distorted manner, resulting in a short circuit failure between adjacent solder balls. It can prevent that stability is inhibited.

  In the configuration of the electronic component mounting structure according to the present invention, it is preferable that the lengths of the reinforcing resins on two opposite sides of the upper surface of the electronic component are substantially equal. According to this preferred example, the sinking balance of the electronic components can be maintained and the total sinking amount can be reduced, so that the connection stress is stored as an internal stress in the solder connection part or the solder ball is deformed irregularly. As a result, it is possible to reliably prevent occurrence of a short circuit between adjacent solder balls and hindering connection reliability and stability of the mounting process.

  In the configuration of the electronic component mounting structure according to the present invention, the length of the reinforcing resin on each side of the upper surface of the electronic component is 1/3 or more of the length of each side. Is preferred.

  Further, in the configuration of the electronic component mounting structure according to the present invention, the reinforcing resin is formed so as to protrude from each corner portion in a substantially opposite direction continuously to the reinforcing resin on each side. It is preferable. The drop impact on the mounting structure of the electronic component mainly acts on the corner of the electronic component, but according to this preferred example, when viewed from the normal direction of the upper surface of the electronic component, Since the reinforcing resin is formed in a state including the corners, it is possible to ensure reliability against a drop impact.

  Further, in the configuration of the electronic component mounting structure according to the present invention, the protrusion of the reinforcing resin is formed to protrude from each corner portion in a substantially opposite direction continuously to the reinforcing resin on each side. The length in the direction is preferably in the range of 100 μm to 3000 μm. According to this preferred example, it is possible to ensure reliability against a drop impact while preventing an increase in the dead space around the electronic component.

  Further, in the configuration of the electronic component mounting structure according to the present invention, the reinforcing resin is formed to extend outside the electronic component along the sides of the upper surface of the electronic component, and The length of the reinforcing resin extending outside the electronic component in the extending direction on the printed circuit board is L, the height of the upper surface of the electronic component from the surface of the printed circuit board is T, and the reinforcing resin is When the height from the surface of the uppermost printed circuit board is H, it is preferable that the following relational expressions (1) and (2) are satisfied.

H> T (1)
L ≧ T (2)
According to this preferable example, it is possible to strengthen the reinforcement with the reinforcing resin while preventing an increase in the dead space around the electronic component.

  The method for manufacturing a mounting structure for an electronic component according to the present invention includes the step of soldering the electronic component to the printed circuit board and the thermosetting of the reinforcing resin in the same heating step. A method of manufacturing a mounting structure, wherein the soldering portion reaches a solder melting temperature so that soldering is not hindered by curing as the reinforcing resin, and solder connection is performed by the weight of the electronic component. This is characterized by using a thermosetting resin having such a characteristic that curing is started after the solder ball of the part sinks and the soldering process is completed.

  ADVANTAGE OF THE INVENTION According to this invention, the mounting structure of an electronic component which can suppress the influence of the heat shrink at the time of hardening of a reinforcement resin at the time of performing soldering and thermosetting of a reinforcement resin at the same heating process, and its manufacturing method Can be provided.

FIG. 1A is a schematic plan view showing a configuration of an electronic component mounting structure according to an embodiment, and FIG. 1B is a cross-sectional view taken along line AA ′ of FIG. FIG. 2 is a schematic perspective view illustrating the configuration of the electronic component mounting structure according to the embodiment. FIGS. 3A to 3C are schematic plan views showing a reinforcing resin coating pattern shape as a comparative example, and FIG. 3D is a diagram for explaining a difference in sinking amount of the electronic component mounting structure. FIG. FIG. 4 is a schematic cross-sectional view for explaining a suitable application state of the reinforcing resin in the electronic component mounting structure according to the embodiment. FIG. 5 is a schematic plan view showing another example of the reinforcing resin coating pattern shape of the electronic component mounting structure according to the embodiment. FIG. 6 is a plan view showing another example of an electronic component used in the electronic component mounting structure according to the embodiment.

  Hereinafter, the present invention will be described more specifically with reference to preferred embodiments. However, the following embodiments are merely examples embodying the present invention, and the present invention is not limited thereto.

  1A is a schematic plan view showing a configuration of a mounting structure for an electronic component in one embodiment, FIG. 1B is a cross-sectional view taken along line AA ′ of FIG. 1A, and FIG. FIG. 2 is a schematic perspective view showing a configuration of a mounting structure of the electronic component.

  As shown in FIGS. 1 and 2, the electronic component mounting structure 1 of the present embodiment has a printed circuit board 2 and a square shape mounted on the printed circuit board 2 via solder (solder balls 3). And a reinforcing resin 5 that is applied and formed across both the printed circuit board 2 and the electronic component 4.

  When viewed from the normal direction of the upper surface of the electronic component 4 (when FIG. 1A is viewed from the direction perpendicular to the paper surface), the reinforcing resin 5 has each corner of the upper surface of the electronic component 4 as a starting point. It is applied and formed in a length that does not reach the adjacent corner portion clockwise along the side. That is, when viewed from the normal direction of the upper surface of the electronic component 4, the reinforcing resin 5 is formed by coating along only one side of each L-shaped corner portion of the upper surface of the electronic component 4.

  Here, as the reinforcing resin 5, the soldering portion reaches the solder melting temperature so that the soldering is not hindered by the hardening, and solder bonding is performed, and the solder ball 3 of the solder connection portion is formed by the weight of the electronic component 4. After the sinking and soldering process is completed, a thermosetting resin having a thermal property that starts curing, such as a urethane resin or an epoxy resin, can be used.

  As described above, according to the electronic component mounting structure 1 of the present embodiment, when viewed from the normal direction of the upper surface of the electronic component 4, the reinforcing resin 5 has an L-shape on the upper surface of the electronic component 4. Since the coating is formed along only one side of each corner portion, the influence of thermal shrinkage during curing of the reinforcing resin 5 when soldering and thermal curing of the reinforcing resin 5 are performed in the same heating process is suppressed to a small level. be able to. As a result, the warpage of the package of the electronic component 4 and the warpage of the printed circuit board 2 can be prevented, and the sinking of the solder balls 3 in the solder connection portion can be prevented from being promoted. As a result, the connection stress is stored as an internal stress in the solder connection portion, or the solder ball 3 deforms in an irregular manner, thereby causing a short circuit failure between the adjacent solder balls 3. It can prevent inhibiting the stability of a process.

  In the electronic component mounting structure 1 of the present embodiment, the length of the reinforcing resin 5 on each side of the upper surface of the electronic component 4 is preferably substantially equal on the two sides facing each other (FIG. 1A). In FIG. 2, the reinforcing resins 5 on the four sides are all the same length). According to this configuration, since the sinking balance of the electronic component 4 can be maintained and the total sinking amount can be reduced, the connection stress is stored as an internal stress in the solder connection part, or the solder ball 3 is deformed irregularly. By doing so, it is possible to reliably prevent the occurrence of short-circuit failure between adjacent solder balls 3 and hinder the connection reliability and the stability of the mounting process.

  In the electronic component mounting structure 1 of the present embodiment, the length of the reinforcing resin 5 on each side of the upper surface of the electronic component 4 is preferably 1/3 or more of the length of each side. . 1A and 2, the length of the reinforcing resin 5 on the four sides is longer than 1/3 of the length of each side and shorter than 1/2 of the length of each side. ing.

  Further, in the electronic component mounting structure 1 of the present embodiment, the reinforcing resin 5 extends from each corner of the upper surface of the electronic component 4 to each side when viewed from the normal direction of the upper surface of the electronic component 4. It is preferable that the reinforcing resin 5 is formed so as to protrude continuously in the opposite direction. That is, when viewed from the normal direction of the upper surface of the electronic component 4, the reinforcing resin 5 is preferably applied and formed so as to include each corner portion of the upper surface of the electronic component 4. The drop impact on the mounting structure of the electronic component 4 mainly acts on the corner portion of the electronic component 4. According to this configuration, when viewed from the normal direction of the upper surface of the electronic component 4, Since the reinforcing resin 5 is applied and formed in a state including the corners on the upper surface, it is possible to ensure reliability against a drop impact.

  The length in the projecting direction of the reinforcing resin 5a (see FIG. 1 (a)) formed by projecting in the opposite direction from each corner of the upper surface of the electronic component 4 continuously with the reinforcing resin 5 on each side is Even with a slight amount, reliability against drop impact can be ensured. On the other hand, according to the electronic component mounting structure 1 of the present embodiment, it is possible to ensure reliability against a drop impact while preventing an increase in the dead space around the electronic component 4. . More specifically, the length in the protruding direction of the reinforcing resin 5a formed by protruding in the opposite direction from each corner of the upper surface of the electronic component 4 continuously with the reinforcing resin 5 on each side is 100 μm to It is preferably in the range of 3000 μm.

  According to the electronic component mounting structure 1 of the present embodiment, as described above, when the soldering and the thermosetting of the reinforcing resin 5 are performed in the same heating process, the heat shrinkage at the time of curing of the reinforcing resin 5 occurs. In particular, when the lengths of the reinforcing resin 5 on the two opposite sides of the electronic component 4 are substantially equal, the balance of the electronic component 4 is maintained and the total amount of subsidence is reduced. Can be reduced. The present inventors measured the difference (H1-H2) in the amount of subsidence of the electronic component mounting structure 1 of the present embodiment and confirmed that it was about 10 μm. Here, H1 is the height from the surface of the printed circuit board 2 at the highest point on the upper surface of the electronic component 4, and H2 is the height from the surface of the printed circuit board 2 at the lowest point on the upper surface of the electronic component 4. (See FIG. 3 (d)). As the reinforcing resin 5, an epoxy resin is used. As the electronic component 4, the size of the upper surface is 22 mm square, the thickness is 0.98 mm, the ball diameter of the solder ball is φ0.4 mm, and the ball height is 0.3 to 0. The length of the reinforcing resin 5 on each of the four sides was set to 8 mm.

  On the other hand, in the case of an electronic component mounting structure having a coating pattern shape of the reinforcing resin 5 ′ shown in FIGS. 3A to 3C, the difference in sinking amount (H1−H2) is 40 μm, 22 μm and 17 μm. In this case, the same epoxy resin as described above was used as the reinforcing resin 5 ′, and the same one as described above was used as the electronic component 4.

  From the above measurement results, in the case of the electronic component mounting structure having the application pattern shape of the reinforcing resin 5 ′ shown in FIGS. 3A to 3C, the soldering and the thermosetting of the reinforcing resin 5 ′ are the same. It can be seen that the effect of thermal shrinkage at the time of curing of the reinforcing resin 5 ′ cannot be suppressed to a sufficiently small level in the heating step.

  In the present embodiment, the reinforcing resin 5 is formed to extend outside the electronic component 4 along each side of the upper surface of the electronic component 4. In the electronic component mounting structure 1 according to the present embodiment, the length of the reinforcing resin 5 extending outside the electronic component 4 in the extending direction on the printed circuit board 2 is L, When the height from the top surface of the printed circuit board 2 is T and the height from the top surface of the printed circuit board 2 of the reinforcing resin 5 is H (see FIG. 4), the following relational expressions (1) and (2 ) Is preferably satisfied.

H> T (1)
L ≧ T (2)
If the reinforcing resin 5 is formed so as to satisfy the relational expressions (1) and (2), the dead space around the electronic component 4 is prevented from increasing, and the reinforcement with the reinforcing resin 5 is strengthened. Can be.

  In the present embodiment, when viewed from the normal direction of the upper surface of the electronic component 4, the reinforcing resin 5 is adjacent to each other in the clockwise direction along each side starting from each corner of the upper surface of the electronic component 4. However, as shown in FIG. 5, it does not reach the next corner counterclockwise along each side starting from each corner on the upper surface of the electronic component 4 as shown in FIG. The reinforcing resin 5 may be formed with a length.

  Further, in the present embodiment, the electronic component 4 having a square planar shape is used, but the planar shape of the electronic component may be a substantially rectangular shape. For example, an electronic component 4 ′ having a rectangular planar shape as shown in FIG. 6 may be used. Even in the case of such a mounting structure using a rectangular electronic component 4 ′, the length of the reinforcing resin 5 on each side of the upper surface of the electronic component 4 ′ is on two opposite sides. Are preferably substantially equal to each other, and preferably 1/3 or more of the length of each side.

  Further, in the present embodiment, when viewed from the normal direction of the upper surface of the electronic component 4, both ends of the application pattern shape of the reinforcing resin 5 are square, but when a coating nozzle having a circular opening is used The both ends of the application pattern shape of the reinforcing resin 5 are substantially circular. Even in this case, the intended purpose can be achieved and the same effect can be obtained.

  In the present embodiment, the case where the reinforcing resin 5 is applied and formed at a desired location using an application nozzle has been described as an example. However, the present invention is not necessarily limited to this embodiment. For example, the structure etc. which blow off reinforcement resin using the blowing outlet which has the desired width which can satisfy the above-mentioned characteristic can also be employ | adopted.

  As described above, according to the present invention, when the soldering and the thermosetting of the reinforcing resin are performed in the same heating process, the influence of the heat shrinkage during the curing of the reinforcing resin is suppressed to a small level, and the connection stress is applied to the solder connection portion. Can be stored as internal stress, or the solder balls can deform in a distorted manner, resulting in a short circuit failure between adjacent solder balls, impairing connection reliability and stability of the mounting process. Can be prevented. Therefore, the present invention is useful for a mounting structure of a solder bump connection type electronic component such as a BGA package and a CSP.

DESCRIPTION OF SYMBOLS 1 Electronic component mounting structure 2 Printed circuit board 3 Solder ball 4 Electronic component 5 Reinforcement resin

Claims (7)

A printed circuit board,
An electronic component having a substantially rectangular planar shape mounted on the printed circuit board via solder;
A mounting structure for an electronic component comprising a reinforcing resin formed across both the printed circuit board and the electronic component,
When viewed from the normal direction of the upper surface of the electronic component,
The electronic component is characterized in that the reinforcing resin is formed with a length that does not reach the adjacent corners clockwise or counterclockwise along each side starting from each corner of the upper surface of the electronic component Implementation structure.   The electronic component mounting structure according to claim 1, wherein the lengths of the reinforcing resins on two opposite sides of the upper surface of the electronic component are substantially equal.   The electronic component mounting structure according to claim 1 or 2, wherein a length of the reinforcing resin on each side of the upper surface of the electronic component is 1/3 or more of a length of each side.   2. The electronic component mounting structure according to claim 1, wherein the reinforcing resin is formed so as to protrude from each corner portion in a substantially opposite direction continuously to the reinforcing resin on each side.   The length in the protruding direction of the reinforcing resin formed so as to protrude from each corner portion in the substantially opposite direction continuously to the reinforcing resin on each side is in the range of 100 μm to 3000 μm. The electronic component mounting structure described in 1. The reinforcing resin is formed to extend outside the electronic component along each side of the upper surface of the electronic component, and
The length of the reinforcing resin extending outside the electronic component in the extending direction on the printed board is L, the height of the upper surface of the electronic component from the surface of the printed board is T, and the reinforcing resin 6. The electronic component mounting structure according to claim 1, wherein the following relational expressions (1) and (2) are satisfied, where H is the height from the surface of the printed circuit board at the top of the printed circuit board: body.
H> T (1)
L ≧ T (2) The method for manufacturing an electronic component mounting structure according to claim 1, wherein the soldering of the electronic component to the printed circuit board and the thermosetting of the reinforcing resin are performed in the same heating step. And
As the reinforcing resin, the soldering part reaches the solder melting temperature so that the soldering is not hindered by curing thereof, and solder bonding is performed. A method of manufacturing a mounting structure for an electronic component, comprising using a thermosetting resin having such a property that curing is started after the process is completed.

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