JP2009010201A - Printed circuit board and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure a connection between a semiconductor package and a printed wiring board without applying an excessive amount of an adhesive. <P>SOLUTION: The printed circuit board 15 includes: the printed wiring board 16; a semiconductor package 17 which has a plurality of solder balls 29 on the backside of the package and is mounted on the printed wiring board 16 by solder joining using the solder balls 29; a plurality of recessed portions 41 which are provided on a mount surface portion of the printed wiring board 16 where the semiconductor package 17 is mounted and disposed near an outer edge of the semiconductor package 17; and an adhesive made of a reinforcing material making a reinforcement connection between the mount surface portion and the backside of the package, the recessed portions 41 being filled with part of the adhesive 31. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a printed circuit board, and more particularly to a printed circuit board on which circuit components such as a BGA (Ball Grid Array) type semiconductor package are mounted.

  For example, a printed circuit board used for a portable computer has a printed wiring board on which a BGA type semiconductor package is mounted. In such a printed circuit board, since the semiconductor package and the printed wiring board are precisely connected through a plurality of solder balls, it is necessary to secure the predetermined strength and fix the semiconductor package to the printed wiring board. For this reason, in the conventional printed circuit board, the corner | angular part of a semiconductor package is fixed to a printed wiring board via resin-made adhesive agents. The adhesive is filled in the side surface of the circuit component. The adhesive filling position is adjacent to the area where the solder is supplied.

When the adhesive flows into the plurality of solders, thermal stress is applied to the solder joint due to repeated expansion and contraction due to heat, and cracks may occur. For example, Patent Document 1 discloses a technique in which an entire region filled with an adhesive is configured as a step portion between a circuit component and a printed wiring board.
Japanese Patent Laying-Open No. 2007-48976 (page 8, FIG. 4)

  However, in the technique of Patent Document 1, the entire surface of the adhesive application region is a position lower than the periphery thereof. Therefore, when the adhesive is applied to a predetermined height, the adhesive is always applied in excess of the height lowered by one step. On the other hand, when an extra adhesive is not applied in the amount of the predetermined adhesive, the adhesive is applied in a state where the adhesive is lowered one step, so that the adhesive may not reach the semiconductor package sufficiently.

  Therefore, the present invention has been made to solve the above problems, and provides a printed circuit board that can ensure the connection between the semiconductor package and the printed wiring board without applying an excessive amount of adhesive. With the goal.

  In order to achieve the above object, a printed circuit board according to the present invention includes a printed wiring board, a semiconductor having a plurality of solder joints on the back surface of the package, and mounted on the printed wiring board by solder joining of the solder joints. A package, a plurality of recesses that are provided on a mounting surface portion of the printed wiring board on which the semiconductor package is mounted, are formed by a reinforcing material that reinforces and connects the mounting surface portion and the back surface of the package. And a part of the reinforcing part is filled in the concave part.

  The electronic device of the present invention is an electronic device containing a printed circuit board, the printed circuit board having a printed wiring board and a plurality of solder joints on the back surface of the package, and the solder of the solder joints A semiconductor package mounted on the printed wiring board by bonding, a plurality of recesses located near an outer edge of the semiconductor package, provided on a mounting surface portion of the printed wiring board on which the semiconductor package is mounted; the mounting surface portion; And a reinforcing portion formed of a reinforcing material that reinforces and connects the back surface of the package, and a portion of the reinforcing portion is filled in the concave portion.

  The connection between the semiconductor package and the printed wiring board can be ensured without applying an excessive amount of adhesive.

  FIG. 1 is a perspective view of a portable computer according to an embodiment of the present invention. In FIG. 1, a main body 12 of a portable computer 11 is provided with a display housing 14a so as to be rotatable via a hinge mechanism. The main body 12 is provided with operation units such as a pointing device 13b and a keyboard 13a. The display housing 14a is provided with a display device 14b such as an LCD.

  The main body 12 is provided with a printed circuit board (mother board) 15 incorporating a control circuit for controlling the operation device such as the pointing device 13b and the keyboard 13a and the display device 14b.

FIG. 2 is a perspective view showing a part of the printed circuit board shown in FIG. As shown in FIG. 2, the printed circuit board 15 includes a printed wiring board 16 and a BGA (Ball Gr
id Array) type semiconductor package 17.

  FIG. 3 is a top view of the printed circuit board shown in FIG. As shown in FIG. 3, the semiconductor package 17 is fixed to the printed wiring board 16 with the package body 28 superimposed on the upper quarter of the first adhesive element 32. In addition, the semiconductor package 17 is fixed to the printed wiring board 16 with the package body 28 superimposed on the upper half of the second adhesive element 34.

  4 is a cross-sectional view of the printed circuit board shown in FIG. 3 cut along line AA. As shown in FIG. 4, the printed wiring board 16 is composed of a copper-clad laminate in which, for example, copper wiring layers are laminated. The printed wiring board 16 includes a resin insulating layer 18 having a glass cloth as a base material, a wiring layer 19 provided between the insulating layers 18, and a plurality of pads 25 provided on the upper surface of the printed wiring board. And a solder resist layer 26 that covers the surface of the printed wiring board 16 while leaving a portion of the pad 25 and a concave portion 41 to be described later. The wiring layer 19 is formed on the insulating layer 18 in a predetermined pattern, for example, by etching a copper foil.

  The pad 25 is plated provided in a via hole (not shown) and connected to, for example, a wiring 27 located in a lower layer. The solder resist layer 26 is formed, for example, by printing a solder resist on the uppermost layer wiring (not shown).

  As shown in FIG. 2, the semiconductor package 17 is an example of a circuit component and is mounted on the printed wiring board 16. The semiconductor package 17 has a package body 28 in which a semiconductor element (not shown) is resin-molded, and a plurality of solder balls 29 as connection terminals. The package body 28 has a square plate shape. The plurality of solder balls 29 are arranged in a lattice pattern on the lower surface of the package body 28 so as to correspond to the pads 25.

Therefore, as shown in FIG. 4, the connection portion between the solder ball 29 and the pad 25 is located between the printed wiring board 16 and the semiconductor package 17.

  As shown in FIG. 2, the four corners 17 a of the semiconductor package 17 are fixed to the printed wiring board 16 via adhesives 31, respectively. The adhesive 31 is made of, for example, a thermosetting resin. The adhesive 31 fixes the package body 28 to the printed wiring board 16 at three points for each corner 17 a of the semiconductor package 17. That is, the adhesive 31 includes a first adhesive element 32 provided facing the corner portion 17a of the semiconductor package 17, and a pair of second adhesive elements 34 provided adjacent to the first adhesive element 32. have. The second adhesive element 34 is provided facing two sides of the semiconductor package 17 adjacent to the corner portion 17a. The adhesive 31 is filled between the outer peripheral portion 33 of the semiconductor package 17 and the printed wiring board 16.

  As shown in FIG. 4, a stepped portion 40 is provided on the printed wiring board 16. In the present embodiment, the stepped portion 40 is a recess 41 formed by not applying the solder resist layer 26 covering the surface of the printed wiring board 16 to the edge of the adhesive surface of the adhesive 31 applied to the printed wiring board. It is prescribed. The recess 41 protrudes from the solder resist layer of the printed wiring board 16 toward the insulating layer 18. In the present embodiment, the recess 41 is provided on the semiconductor package 17 side on the bonding surface. That is, the adhesive 31 includes the recess 41 and is applied in the outer circumferential direction of the semiconductor package 17.

  Next, a flow of mounting work of the semiconductor package 17 will be described.

  First, the solder 44 is supplied corresponding to the position of the pad 25 on the printed wiring board 16.

  Next, an adhesive 31 is applied on the printed wiring board 16. Application of the adhesive 31 applies the adhesive elements 32 and 34 to the region of the adhesive surface including the recess 41. The height of the adhesive 31 after application of the adhesive elements 32 and 34 is set sufficiently higher than the height of the solder ball 29. Further, it is preferable that the coating is appropriately adjusted so that the height reaches the height of the semiconductor package 17.

  By applying the adhesive 31, a part of the adhesive elements 32, 34 enters the recess 41, but the amount is extremely small compared to the total amount of each of the adhesive elements, and thus the adhesive elements 32, 34. The height of the adhesive 31 after coating is not extremely lowered depending on the presence or absence of the recess 41.

  As described above, the adhesive 31 is thermosetting. The adhesive 31 is a so-called “first-in” adhesive that is applied onto the printed wiring board 16 before the semiconductor package 17. In other words, an adhesive having a higher viscosity than the “last-in” adhesive applied on the printed wiring board 16 after the semiconductor package 17 is used.

  Next, the semiconductor package 17 is picked up by an automatic mounting machine (mounter) and mounted on the upper side of the printed wiring board 16. The semiconductor package 17 is mounted on the printed wiring board 16 so that the solder balls 29 are placed on the solder 44 supplied to the pads 25.

  Next, the melting of the solder 44 and the curing of the adhesive are collectively performed in a reflow furnace. Thereby, the solder 44 and the solder ball 29 are melted. The printed wiring board 16 and the semiconductor package 17 are electrically connected by melting the solder 44 and the solder ball 29. Further, the adhesive is cured, and the corners of the semiconductor package and the printed wiring board 16 are connected by the adhesive 31. Note that the heat treatment in the reflow furnace is preferably set so that the adhesive 31 is cured after the solder 44 is melted. In this way, even after the solder 44 is melted, fine adjustment, that is, alignment, of the semiconductor package 17 mounted with a misalignment can be performed. In this case, after the alignment operation, the heating is further continued and the adhesive 31 is cured.

  According to this embodiment, the adhesive 31 is applied on the recess 41. This adhesive is a so-called first-in-adhesive, and has a higher viscosity than the latter-in-adhesive. Therefore, there is a recess 41 in a part of the bonding surface on the printed wiring board 16, and a part of the adhesive 31 is filled in the recess 41. Therefore, in order to flow into the solder ball 29 inside the semiconductor package 17, the adhesive 31 must get over the recess 41. That is, it becomes difficult for the adhesive 31 to flow into the plurality of solders. Therefore, it is possible to reduce the occurrence of cracks in the solder joint due to repeated expansion and contraction due to heat.

  Further, although the adhesive elements 32 and 34 enter the recess 41, the amount thereof is extremely small as compared with the total amount of each of the adhesive elements. Therefore, the adhesive 31 after application of the adhesive elements 32 and 34 is performed. Is not extremely low depending on the presence or absence of the recess 41. Therefore, it is possible to reduce the capacity of the adhesive 31 as compared with the case where the area of the bottom surface of the recess is wide and the bonding surface is the entire bottom surface of the recess.

  Therefore, the connection between the semiconductor package and the printed wiring board can be secured without applying an excessive amount of adhesive.

  In the present embodiment, the recess 41 is formed by not applying the solder resist layer 26. However, by the laser processing or the like, not only the solder resist layer 26 but also the depth of the insulating layer 18 and the wiring layer 19 or the case. Thus, the printed wiring board 19 may be formed by processing as in the thickness direction. Further, although the recess 41 is adjacent to the semiconductor package 17, as shown in FIG. 4B, the recess 41 may be close to the extent that the outermost solder ball 29 and the adhesive element 32 are in contact with each other.

(Second Embodiment)
Next, a second embodiment of the printed circuit board 15 will be described with reference to FIG. FIG. 5 is a cross-sectional view of the printed circuit board according to the second embodiment, taken along a line corresponding to the line AA in FIG. Since the configuration of the printed circuit board 15 of the second embodiment is the same as that of the first embodiment except for the printed wiring board 16, the same reference numerals are used and description thereof is omitted.

In the printed circuit board 15 of the second embodiment, the stepped portion 40 is constituted by a recess 51 provided not only on the side closer to the semiconductor package 17 but also on the far side.

  The recess 51 can be formed by not applying the solder resist layer 26 as in the case of the recess 41. Further, not only the solder resist layer 26 but also the depth of the insulating layer 18 and the wiring layer 19 may be formed by laser processing or the like, or the printed wiring board 19 may be formed by processing such as in the thickness direction.

  By providing the recess 51, not only can the adhesive 31 flow into the semiconductor package 17, but it can also be prevented from spreading in the circumferential direction of the package, and the height of the adhesive can be ensured reliably.

  Therefore, the connection between the semiconductor package and the printed wiring board can be secured without applying an excessive amount of adhesive.

(Third embodiment)
Next, a third embodiment of the printed circuit board 15 will be described with reference to FIG. FIG. 6 is a top view of a printed circuit board according to the third embodiment of the present invention. FIG. 7 is a cross-sectional view of the printed circuit board shown in FIG. 6 cut along line BB. Since the configuration of the printed circuit board 15 of the third embodiment is the same as that of the first embodiment except for the printed wiring board 16 and the adhesive 31, the same reference numerals are given and description thereof is omitted.

  As shown in FIGS. 6 and 7, the printed circuit board 15 of the third embodiment is configured by a recess 61 in which a stepped portion 40 is connected at each corner, and the adhesive elements 32 and 34 are continuous in the portion. Applied.

  The recess 61 can be formed by not applying the solder resist layer 26, similarly to the recess 41. Further, not only the solder resist layer 26 but also the depth of the insulating layer 18 and the wiring layer 19 may be formed by laser processing or the like, or the printed wiring board 19 may be formed by processing such as in the thickness direction. By providing the recess 61, the semiconductor package 17 and the printed wiring board 16 can be more firmly connected.

  FIG. 8 is a cross-sectional view showing another embodiment of the concave portion of the printed circuit board shown in FIG. As shown in FIG. 8, the step sub 40 may be a recess 71 provided not only near the semiconductor package 17 but also on the far side. Also in FIG. 8, the semiconductor package 17 and the printed wiring board 16 can be more firmly connected.

  The printed circuit board according to the present invention is not limited to the portable computer shown in the above embodiment, and can be implemented for other electronic devices such as a portable information terminal.

1 is a perspective view of a portable computer according to a first embodiment of the present invention. FIG. 2 is a perspective view showing a part of the printed circuit board housed in the casing of the portable computer shown in FIG. 1. FIG. 3 is a top view of the printed circuit board shown in FIG. 2. Sectional drawing which cut | disconnected the printed circuit board shown in FIG. 3 by the AA line. Sectional drawing which cut | disconnected the printed circuit board which concerns on 2nd Embodiment by the line corresponding to the AA line of FIG. The top view of the printed circuit board which concerns on the 3rd Embodiment of this invention. Sectional drawing which cut | disconnected the printed circuit board shown in FIG. 6 by the BB line. Sectional drawing which showed other embodiment of the recessed part of the printed circuit board shown in FIG.

Explanation of symbols

11 Portable computer 11
12 Body 12
13a Keyboard 13a
13b pointing device 13b
14a Display housing 14a
14b display device 14b
15 Printed circuit board 15
16 Printed wiring board 16
17 Semiconductor Package 17
17a Corner 17a
18 Insulating layer 18
19 Wiring layer 19
25 Pad 25
26 Solder resist layer 26
27 Wiring 27
28 Package body 28
29 Solder balls 29
31 Adhesive 31
32, 34 Adhesive element 32
33 Outer part 33
40 Step 40
41, 51, 61, 71 Recess 41
44, Solder 44

Claims (6)

A printed wiring board;
A semiconductor package having a plurality of solder joints on the back surface of the package, and mounted on the printed wiring board by solder joining of the solder joints;
A plurality of concave portions provided in a mounting surface portion on which the semiconductor package of the printed wiring board is mounted, and located near an outer edge of the semiconductor package;
A reinforcing portion formed of a reinforcing material for reinforcing connection between the mounting surface portion and the back surface of the package;
A printed circuit board, wherein a part of the reinforcing portion is filled in the recess.   The printed circuit board according to claim 1, wherein the reinforcing portion locally reinforces a plurality of corner portions of the semiconductor package.   The printed wiring board according to claim 1, wherein another recessed portion is provided outside the periphery of the semiconductor package from the recessed portion.   The printed circuit board according to claim 1, wherein a part of the reinforcing part is in contact with a part of a solder joint part of the semiconductor package.   The printed circuit board according to claim 1, wherein the reinforcing portion is applied on the printed wiring board prior to the semiconductor package. An electronic device containing a printed circuit board,
The printed circuit board is:
A printed wiring board;
A semiconductor package having a plurality of solder joints on the back surface of the package, and mounted on the printed wiring board by solder joining of the solder joints;
A plurality of concave portions provided in a mounting surface portion on which the semiconductor package of the printed wiring board is mounted, and located near an outer edge of the semiconductor package;
A reinforcing portion formed of a reinforcing material for reinforcing connection between the mounting surface portion and the back surface of the package;
An electronic apparatus characterized in that a part of the reinforcing portion is filled in the recess.

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