JP2013089853A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board capable of reducing the limit applied to the layout of the outside of a component mounting region while preventing the wiring failure such as a solder crack.SOLUTION: In a printed wiring board 1 having a plurality of electrode pads 3 arranged in matrix, and a hole 7 for easing thermal stress provided on the outside of a component mounting region 5 where the plurality of electrode pads 3 are arranged, a BGA package 2 having an outer edge larger than the component mounting region 5 in a plan view is mounted in the component mounting region 5, and the hole 7 is provided at a position corresponding to the outer edge of the BGA package 2.

Description

  The present invention relates to a printed wiring board.

  Patent Document 1 below discloses a printed wiring board on which a BGA (Ball grid array) package is mounted as an electronic component. In recent years, printed wiring boards tend to be mounted with such small electronic components at a high density, and at the time of operation, they are in a high temperature state due to the influence of these heat generation. When the printed wiring board repeats expansion during operation and restoration (contraction) during non-operation, thermal stress is greatly applied to the mounted BGA package or the like.

  In the above prior art, when an external stress is applied to the printed wiring board, at least one deflection reducing hole for reducing the deflection due to the external stress is formed. The deflection reducing hole is formed on at least one diagonal line of the region outside the component mounting region of the plurality of electrode pads arranged in a matrix. According to this configuration, since the deformation of the wiring board can be absorbed by the deflection reduction hole, the thermal stress accompanying the thermal stress can be alleviated, and problems such as poor contact of the wiring part and disconnection (solder crack) can be avoided. .

JP 2001-119107 A

  However, in the above prior art, the space outside the component mounting area is consumed by forming a hole such as a deflection reducing hole, so the wiring outside the component mounting area and the arrangement of other electronic components, etc. There is a problem that the degree of freedom of layout is limited.

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide a printed wiring board capable of reducing restrictions on the layout outside the component mounting area while preventing wiring defects such as solder cracks. And

  In order to solve the above problems, the present invention includes a plurality of electrode pads arranged in a matrix, and a hole provided on the outside of a component mounting region in which the plurality of electrode pads are arranged to relieve thermal stress. The printed wiring board includes a component package mounted on the component mounting area and having an outer edge larger than the component mounting area in plan view, and the hole corresponds to the outer edge of the component package. A configuration that is provided at a position to be adopted is adopted.

  Further, in the present invention, a configuration is adopted in which the hole is provided at a corner where the first side and the second side of the outer edge of the component package intersect.

  Further, in the present invention, the hole portion includes an intersection point where the first side and the second side intersect, and each of the first side and the second side at a predetermined distance from the intersection point. The configuration that is provided in is adopted.

  Moreover, in this invention, the said hole is employ | adopted as the structure provided ranging over the said 1st edge | side and the said 2nd edge | side.

  In the present invention, the hole is a through hole that is electrically grounded.

In the present invention, a component package that is mounted in the component mounting region and has an outer edge larger than the component mounting region in a plan view is provided, and the hole is provided at a position corresponding to the outer edge of the component package. . When the outer edge of the component package is larger than the component mounting area, alignment marks are required for alignment in order to properly place the ball electrodes of the component package on the electrode pads arranged in the component mounting area. It becomes. Here, by providing a hole at a position corresponding to the outer edge of the component package, not only a function of relieving thermal stress but also an alignment function is added to the hole, and the hole is also used as an alignment mark. Thereby, it is possible to reduce the space consumption outside the component mounting area without providing an alignment mark separately.
Thus, according to the present invention, it is possible to reduce restrictions on the layout outside the component mounting area while preventing wiring defects such as solder cracks.

It is a top view of the printed wiring board in a 1st embodiment of the present invention. It is an enlarged plan view which shows the principal part of the printed wiring board in 1st Embodiment of this invention. It is an enlarged plan view which shows the principal part of the printed wiring board in 2nd Embodiment of this invention. It is an enlarged plan view which shows the principal part of the printed wiring board in 3rd Embodiment of this invention.

  Hereinafter, an embodiment of a printed wiring board according to the present invention will be described with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

(First embodiment)
FIG. 1 is a plan view of a printed wiring board 1 according to the first embodiment of the present invention. FIG. 2 is an enlarged plan view showing a main part of the printed wiring board 1 according to the first embodiment of the present invention.
As shown in FIG. 1, the printed wiring board 1 is a substrate on which a component package (BGA package 2 in this embodiment) is mounted. The component package mounted on the printed wiring board 1 of the present embodiment is not limited to a BGA (Ball grid array) package, but may be an LGA (Land grid array) package or the like.

  The printed wiring board 1 is a plate-like member made of an insulating material such as a glass epoxy material or a glass composite material, and electrode pads 3 and a wiring pattern (not shown) are formed on the surface thereof. This printed wiring board 1 is accommodated in an external housing (not shown) (for example, aluminum die-casting), and its edge is fixed to the external housing by screws or the like.

  The electrode pad 3 is a place where a ball electrode (solder ball) on the bottom surface of the package is disposed when the BGA package 2 is reflow soldered. A plurality of electrode pads 3 are provided according to the number of electrodes of the BGA package 2. The electrode pads 3 are arranged in a matrix as shown in the figure. Note that a rectangular region in plan view where the plurality of electrode pads 3 are arranged is a component mounting region 5.

  The printed wiring board 1 includes a hole 7 that relieves thermal stress outside the component mounting region 5 in which a plurality of electrode pads 3 are arranged. The hole 7 is a hole formed in the thickness direction of the printed wiring board 1. The hole 7 of this embodiment is a through hole in which a conductive layer 7a is formed on the inner wall. The hole 7 is electrically grounded as shown in FIG. The hole 7 may be a simple through hole in which the conductive layer 7a is not formed on the inner wall.

  Returning to FIG. 1, the BGA package 2 is mounted in the component mounting region 5 and has an outer edge larger than the component mounting region 5 in plan view. The hole 7 is provided at a position corresponding to the outer edge of the BGA package 2. The outer edge of the BGA package 2 of the present embodiment has a shape similar to that of the component mounting region 5 and has a rectangular shape in plan view that is slightly larger. A plurality of holes 7 in the present embodiment are provided along the outer edge of the BGA package 2.

  Specifically, four hole portions 7 of the present embodiment are provided corresponding to each of the four corner portions 8 of the outer edge of the BGA package 2. The plurality of holes 7 have the same diameter and the same configuration, and are arranged on the diagonal line of the outer edge of the BGA package 2. Specifically, among the plurality of hole portions 7, the hole portion 7 </ b> A and the hole portion 7 </ b> C are arranged on the diagonal line of the outer edge of the BGA package 2, and the hole portion 7 </ b> B and the hole portion 7 </ b> D are combined. Are arranged on the diagonal line of the outer edge of the BGA package 2.

  As shown in FIG. 2, the corner 8 of the outer edge of the BGA package 2 is the inner edge of the BGA package 2 including the intersection 10 where the first side 9A and the second side 9B of the outer edge of the BGA package 2 intersect. This is a predetermined area. The hole 7 is formed around an intersection 10 where the first side 9A and the second side 9B intersect. In the present embodiment, a part of the hole 7 overlaps with the corner part 8 in a plan view, and the remaining part of the hole 7 is formed so as to be visible in a plan view.

  The hole 7 is formed at a position corresponding to the corner 8 by a tool such as a drill. Since the corner 8 has a positional relationship adjacent to the electrode pad 3 a located at the corner end of the component mounting region 5, if the hole 7 is too close to the electrode pad 3 a, the gap between the electrode pad 3 a and the hole 7 is increased. In this case, the resist cannot be properly formed. For example, the resist may cover the electrode pad 3a. Therefore, when forming the hole portion 7, it is preferable to form the hole portion with an appropriate distance in consideration of the resist covering.

Next, the operation of the printed wiring board 1 having the above configuration will be described.
The printed wiring board 1 is constrained by screwing or the like to an external housing (not shown), and the influence of thermal expansion due to the temperature rise during operation is in the direction of the white arrow shown in FIG. Works. If it does so, it will become easy to produce a solder crack with the BGA package 2 in the corner end (for example, electrode pad 3a) of the component mounting area | region 5. FIG.

  The printed wiring board 1 according to the present embodiment includes a hole 7 that relaxes thermal stress outside the component mounting region 5 in which a plurality of electrode pads 3 are arranged. As described above, by providing the hole 7 outside the component mounting area 5, the influence of the thermal expansion of the wiring board can be efficiently absorbed on the front side of the component mounting area 5. For this reason, in the component mounting region 5, the distortion and thermal stress of the wiring board are alleviated, and wiring defects such as solder cracks are prevented.

  In the present embodiment, the BGA package 2 is mounted in the component mounting area 5 and has an outer edge larger than the component mounting area 5 in plan view, and the hole 7 is a position corresponding to the outer edge of the BGA package 2. Is provided. When the outer edge of the BGA package 2 is larger than the component mounting area 5, in order to properly arrange the ball electrodes of the BGA package 2 on the electrode pads 3 arranged in the component mounting area 5, An alignment mark is required.

  In the present embodiment, the hole 7 is provided in the corner 8 where the first side 9A and the second side 9B intersect on the outer edge of the BGA package 2. Therefore, by aligning the four hole portions 7 and the four corner portions 8, it is possible to align the ball electrodes of the BGA package 2 at appropriate positions on the electrode pads 3. And the reflow soldering of the BGA package 2 can be performed appropriately.

  Thus, by providing the hole 7 at a position corresponding to the outer edge of the BGA package 2, not only a function of relieving thermal stress but also an alignment function is added to the hole 7, and it is also used as an alignment mark. be able to. Thereby, the space consumption outside the component mounting area 5 can be reduced without providing an alignment mark separately. Therefore, it is possible to reduce the restriction on the layout outside the component mounting area 5.

  In the present embodiment, the hole 7 is a through hole that is electrically grounded. According to this configuration, the hole 7 is electrically grounded, and the potential is stabilized by using the GND potential, and noise in the component mounting region 5 and the like can be reduced. In addition, in the electrode pads 3a at the corners of the component mounting region 5, the GND electrodes of the BGA package 2 are easily arranged. Thus, by adding a function of stabilizing the potential to the hole portion 7, the space consumption outside the component mounting region 5 can be further reduced without providing a separate GND electrode.

  Therefore, according to the above-described embodiment, the plurality of electrode pads 3 arranged in a matrix and the hole 7 that is provided outside the component mounting region 5 in which the plurality of electrode pads 3 are arranged and relaxes thermal stress. A printed wiring board 1 having a BGA package 2 mounted on the component mounting area 5 and having an outer edge larger than the component mounting area 5 in plan view. By adopting the configuration of being provided at a position corresponding to the outer edge of the circuit board, it is possible to reduce the restriction on the layout outside the component mounting region 5 while preventing wiring defects such as solder cracks.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the following description, the same or equivalent components as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof is simplified or omitted.

FIG. 3 is an enlarged plan view showing a main part of the printed wiring board according to the second embodiment of the present invention.
As shown in FIG. 3, in the second embodiment, the hole 7 includes an intersection 10 where the first side 9 </ b> A and the second side 9 </ b> B intersect, and a first side 9 </ b> A at a predetermined distance from the intersection 10. And the second side 9B.

According to this structure, since it can arrange | position so that the electrode pad 3a may be enclosed by the said three hole parts 7, wiring defects, such as a solder crack, can be prevented reliably.
In addition, when the number of the holes 7 is increased, there is a trade-off that the layout is more limited than in the above embodiment. However, by aligning the three holes 7 and one corner 8, the entire BGA package 2 can be aligned. Therefore, as in the above-described embodiment, alignment can be performed without providing the holes 7 in all the corners 8 (for example, at two locations on the diagonal line), so that there are excessive restrictions on the layout outside the component mounting region 5. It will never grow.

(Third embodiment)
Next, a third embodiment of the present invention will be described. In the following description, the same or equivalent components as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof is simplified or omitted.

FIG. 4 is an enlarged plan view showing a main part of the printed wiring board according to the third embodiment of the present invention.
As shown in FIG. 4, in the third embodiment, the hole portion 7 is provided in a substantially L shape in plan view across the first side 9 </ b> A and the second side 9 </ b> B.

According to this configuration, since the electrode pad 3a is surrounded by the L-shaped hole 7 in plan view without leaving a gap as in the second embodiment, wiring defects such as solder cracks can be more reliably prevented. Can do.
Further, the trade-off is the same as that of the second embodiment, and alignment can be performed without providing the holes 7 in all the corners 8, so that the restriction on the layout outside the component mounting area 5 becomes excessively large. There is nothing.

  As mentioned above, although preferred embodiment of this invention was described referring drawings, this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Printed wiring board, 2 ... BGA package (component package), 3 ... Electrode pad, 5 ... Component mounting area, 7 ... Hole part (through hole), 8 ... Corner | angular part, 9A ... 1st edge | side, 9B ... 1st 2 sides, 10 ... intersection

Claims (5)

A printed wiring board having a plurality of electrode pads arranged in a matrix and a hole provided outside a component mounting region in which the plurality of electrode pads are arranged to relieve thermal stress,
A component package mounted on the component mounting region and having an outer edge larger than the component mounting region in plan view,
The printed wiring board, wherein the hole is provided at a position corresponding to an outer edge of the component package.   The printed wiring board according to claim 1, wherein the hole is provided at a corner where the first side and the second side of the outer edge of the component package intersect.   The hole is provided at each of the intersection of the first side and the second side, and the first side and the second side at a predetermined distance from the intersection. The printed wiring board according to claim 2, wherein   The printed wiring board according to claim 2, wherein the hole is provided across the first side and the second side.   The printed wiring board according to claim 1, wherein the hole is a through hole that is electrically grounded.

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