JP2004200437A - Printed wiring board - Google Patents

Abstract

An object of the present invention is to provide a printed wiring board capable of preventing a displacement and a Manhattan phenomenon at the time of mounting a surface mount type component and improving a non-defective mounting rate.
A pair of footprint patterns (20, 30) to which electrode portions (5A, 5B) of a chip component (5) are soldered have substantially planar shapes with respect to a reference line (BL). Both ends of the footprint patterns 20 and 30 are orthogonal to the reference line BL and symmetrical with respect to a center line CL that divides the pair of footprint patterns 20 and 30 into two, and are bent so as to approach the reference line BL. .
[Selection diagram] Fig. 1

Description

[0001]
The present invention relates to a printed wiring board, and more particularly to a printed wiring board for mounting chip components.
[0002]
[Prior art]
FIG. 8 is a plan view showing a state in which chip components are mounted on a conventional printed wiring board.
[0003]
The printed wiring board 101 includes a substrate body 110 and a pair of rectangular footprint patterns 120 and 130.
[0004]
The pair of footprint patterns 120 and 130 are arranged on the substrate main body 110 at predetermined intervals. The chip component 105 is mounted on the pair of footprint patterns 120 and 130.
[0005]
In order to mount the chip component 105, cream solders 121 and 131 are screen-printed on the footprint patterns 120 and 130 by a printing machine using a metal mask in which openings having the same shape as the footprint patterns 120 and 130 are formed. The chip component 105 is accurately positioned on the footprint patterns 120 and 130 using the mounting device.
[0006]
Then, the cream solders 121 and 131 are melted by passing through a reflow furnace set to a predetermined temperature profile, and the electrode portions 105A and 105B of the chip component 105 are soldered to the footprint patterns 120 and 130.
[0007]
[Problems to be solved by the invention]
By the way, at the time of the reflow, the chip component 105 is pulled in the direction shown by the arrow due to the surface tension of the melted cream solder 121, 131 on the footprint patterns 120, 130.
[0008]
When the amount of the cream solder 121 contacting the electrode portion 105A of the chip component 105 is equal to the amount of the cream solder 131 contacting the electrode portion 105B of the chip component 105, the surface tensions of the cream solders 121 and 131 are equal, and the chip The part 105 maintains a correct position and posture.
[0009]
However, for example, if there is a printing misalignment during screen printing, a difference occurs between the amount of cream solder 121 that contacts electrode portion 105A of chip component 105 and the amount of cream solder 131 that contacts electrode portion 105B. As a result, a difference occurs in the surface tension of the cream solders 121 and 131 at the time of reflow, which causes a positional shift of the chip component 105 and a Manhattan phenomenon (see FIG. 9). FIG. 9 is a cross-sectional view illustrating the Manhattan phenomenon of a chip component.
[0010]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a printed wiring board capable of preventing a positional shift and a Manhattan phenomenon of a surface-mounted component at the time of reflow and improving a non-defective mounting rate. That is.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention provides a printed wiring board on which a surface-mounted component is mounted, wherein the substrate body and the electrode portion of the surface-mounted component are soldered to the substrate body. A pair of footprint patterns, the planar shape of the pair of footprint patterns is substantially symmetric with respect to a reference line, and the footprint pattern is orthogonal to the reference line and defines the pair of footprint patterns. The footprint pattern is symmetrical with respect to a center line divided into two in the reference line direction, and both end portions of the footprint pattern are bent to approach the reference line or bent away from the reference line. I do.
[0012]
According to a second aspect of the present invention, in the printed wiring board according to the first aspect, a line segment connecting a center point of the footprint pattern located on the center line and a point farthest from the center line of the footprint pattern. When the angle formed between the footprint pattern and the center line is α, when both ends of the footprint pattern are bent so as to approach the reference line, 0 <α <90 °, and both ends of the footprint pattern Is characterized by 90 <α <180 ° when is bent away from the reference line.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0014]
FIG. 1 is a plan view of a printed wiring board according to the first embodiment of the present invention.
[0015]
The printed wiring board 1 includes a substrate body 10 and a pair of footprint patterns 20 and 30 formed on the substrate body 10. The electrode portions 5A, 5B of the chip component (surface-mounted component) 5 are soldered to the footprint patterns 20, 30.
[0016]
The planar shape of the pair of footprint patterns 20, 30 is substantially symmetric with respect to the reference line BL. Each of the footprint patterns 20, 30 is symmetrical with respect to a center line CL that is orthogonal to the reference line BL and divides the pair of footprint patterns 20, 30 into two.
[0017]
The footprint patterns 20, 30 are orthogonal portions 20A, 30A orthogonal to the center line CL, and oblique portions 20B, 20C, 30B, 30C extending obliquely from both ends of the orthogonal portions 20A, 30A so as to approach the reference line BL. It is composed of
[0018]
The footprint pattern 20 (30) is a line segment connecting the center point O of the footprint pattern 20 (30) located on the center line CL and the point P farthest from the center line CL of the footprint pattern 20 (30). When α is an angle between the center line CL and the center line CL, 0 <α <90 °.
[0019]
The pair of footprint patterns 20 and 30 are formed of copper foil at positions corresponding to the electrode portions 5A and 5B of the chip component 5.
[0020]
In order to print the cream solders 21 and 31 (see FIG. 2) on the footprint patterns 20 and 30, first, a metal mask (shown in FIG. 2) having the same shape as the footprint patterns 20 and 30 on the substrate body 10 is formed. 3) is superimposed on the footprint patterns 20, 30, and then the cream solder is supplied onto the metal mask, and the cream solders 21, 31 are printed on the footprint patterns 20, 30 using a squeegee of a printing machine.
[0021]
FIG. 2 is a plan view showing a state in which the cream solders 21 and 31 are printed to the left with respect to the footprint patterns 20 and 30, and the chip component 5 is correctly positioned on the footprint patterns 20 and 30.
[0022]
When the printed wiring board 1 is passed through a reflow furnace, the cream solders 21 and 31 printed to be shifted to the left are drawn to the footprint patterns 20 and 30 and moved to the right, and overlap the footprint patterns 20 and 30.
[0023]
At this time, the electrode portions 5A and 5B of the chip component 5 receive a force in the direction indicated by the arrow due to the surface tension of the cream solders 21 and 31, and the vertical direction (reference line BL direction) and the horizontal direction ( It moves to the center of the footprint patterns 20, 30 in the direction of the center line CL.
[0024]
FIG. 3 is a plan view showing a state in which the cream solders 21 and 31 are printed shifted to the left with respect to the footprint patterns 20 and 30, and the chip component 5 is shifted to the left and positioned on the footprint patterns 20 and 30. is there.
[0025]
When the printed wiring board 1 is passed through a reflow furnace, the cream solders 21 and 31 printed to be shifted to the left are drawn to the footprint patterns 20 and 30 and moved to the right, and overlap the footprint patterns 20 and 30.
[0026]
At this time, the chip component 5 receives a force in the direction shown by the arrow due to the surface tension of the cream solders 21 and 31, the self-alignment function is activated, and the chip component 5 moves to the right. That is, it moves to the center of the footprint patterns 20, 30 in the left-right direction. In FIG. 3, the length of the arrow indicates the strength of the surface tension.
[0027]
Further, a uniform force acts in the up-down direction as shown by the arrow, and the electrode portions 5A, 5B of the chip component 5 are located at the center of the footprints 20, 30 in the up-down direction.
[0028]
Although not shown, even when the cream solders 21 and 31 are printed shifted to the right with respect to the footprint patterns 20 and 30, and the chip component 5 is shifted to the right and positioned in the footprint patterns 20 and 30, In the same manner as described above, the chip component 5 moves to the center of the footprint patterns 20 and 30 by the self-alignment function due to the surface tension of the cream solders 21 and 31.
[0029]
FIG. 4 is a plan view showing a state in which the cream solders 21 and 31 are printed shifted to the left with respect to the footprint patterns 20 and 30, and the chip components 5 are shifted upward and positioned on the footprint patterns 20 and 30. is there.
[0030]
When the printed wiring board 1 is passed through a reflow furnace, the cream solders 21 and 31 printed to be shifted to the left are drawn to the footprint patterns 20 and 30 and moved to the right, and overlap the footprint patterns 20 and 30.
[0031]
At this time, the chip component 5 receives a force in the direction indicated by the arrow due to the surface tension of the cream solders 21 and 31 and moves downward by the self-alignment function, and moves vertically to the center of the footprint patterns 20 and 30. I do.
[0032]
Further, a uniform force acts in the left-right direction as indicated by arrows, and the electrode portion of the chip component 5 is located at the center of the footprints 20, 30 in the left-right direction.
[0033]
FIG. 5 is a plan view showing a state in which the cream solders 21 and 31 are printed to the left with respect to the footprint patterns 20 and 30, and the chip components 5 are shifted downward and positioned on the footprint patterns 20 and 30. is there.
[0034]
When the printed wiring board 1 is passed through a reflow furnace, the cream solders 21 and 31 printed to be shifted to the left are drawn to the footprint patterns 20 and 30 and moved to the right, and overlap the footprint patterns 20 and 30.
[0035]
At this time, the chip component 5 receives a force in the direction indicated by the arrow due to the surface tension of the cream solders 21 and 31 and moves upward by the self-alignment function, and moves to the center of the footprint patterns 20 and 30 in the vertical direction. I do.
[0036]
Further, a uniform force acts in the left-right direction as indicated by arrows, and the electrode portion of the chip component 5 is located at the center of the footprints 20, 30 in the left-right direction.
[0037]
FIG. 6 is a plan view showing a state in which the cream solders 21 and 31 are printed so as to be shifted upward with respect to the footprint patterns 20 and 30, and the chip component 5 is accurately positioned on the footprint patterns 20 and 30.
[0038]
When the printed wiring board 1 is passed through a reflow furnace, the cream solders 21 and 31 printed so as to be shifted upward are attracted to the footprint patterns 20 and 30 and move in the directions indicated by arrows, so that the footprint patterns 20 and 30 are moved. Overlap.
[0039]
At this time, the chip component 5 moves downward at the same time, but the self-alignment function by the surface tension of the cream solders 21 and 31 works to cause the electrode portions 5A and 5B of the chip component 5 to receive an upward force, so that the chip components 5 move in the horizontal direction and the vertical direction. It moves to the center of the footprint patterns 20 and 30.
[0040]
According to the first embodiment, the self-alignment function for the printing displacement of the cream solders 21 and 31 and the mounting displacement of the chip component 5 can be improved, so that the displacement of the chip component 5 and the Manhattan phenomenon at the time of reflow occur. It is difficult to improve the non-defective mounting rate of the printed wiring board 1.
[0041]
FIG. 7 is a plan view of a printed wiring board according to a second embodiment of the present invention, and the same reference numerals are given to portions common to the first embodiment, and description thereof will be omitted.
[0042]
The printed wiring board 51 includes a substrate body 10 and a pair of footprint patterns 70 and 80 formed on the substrate body 10. The electrode portions 5A, 5B of the chip component (surface mount type component) 5 are soldered to the footprint patterns 70, 80.
[0043]
The planar shapes of the pair of footprint patterns 70 and 80 are substantially symmetric with respect to the reference line BL. Each of the footprint patterns 70, 80 is symmetric with respect to a center line CL that is orthogonal to the reference line BL and divides the pair of footprint patterns 70, 80 into two.
[0044]
The footprint patterns 70, 80 are orthogonal portions 70A, 80A orthogonal to the center line CL, and oblique portions 70B, 70C, 80B, 80C extending obliquely away from the reference line BL from both ends of the orthogonal portions 70A, 80A. It is composed of
[0045]
The footprint pattern 70 (80) is a line segment connecting the center point O of the footprint pattern 70 (80) located on the center line CL and the point P farthest from the center line CL of the footprint pattern 70 (80). When an angle between the center line and the center line CL is α, 90 <α <180 °.
[0046]
The pair of footprint patterns 70 and 80 are formed of copper foil at positions corresponding to the electrode portions 5A and 5B of the chip component 5.
[0047]
Cream solder (not shown) is printed on the footprint patterns 70 and 80 by the same method as in the first embodiment.
[0048]
If there is a misalignment of printing of the cream solder or a misalignment of the chip component 5 with respect to the footprint patterns 70, 80, when the printed wiring board 1 is passed through a reflow furnace, the printed cream solder is removed from the footprint patterns 70, 80. The chip component 5 receives the force due to the surface tension of the cream solder, the self-alignment function is activated, and moves to the center of the footprint patterns 70, 80.
[0049]
According to the second embodiment, the same effects as those of the first embodiment can be obtained.
[0050]
In the above embodiment, the planar shape of each of the footprint patterns 20, 30, 70, and 80 is constituted by three linear portions. However, the planar shape is not limited to this, and the entire pattern may be curved.
[0051]
【The invention's effect】
As described above, according to the printed wiring board of the present invention, it is possible to prevent the misalignment of the chip components and the Manhattan phenomenon at the time of reflow and improve the non-defective mounting rate.
[Brief description of the drawings]
FIG. 1 is a plan view of a printed wiring board according to a first embodiment of the present invention.
FIG. 2 is a plan view showing a state in which cream solder is printed shifted to the left with respect to a footprint pattern, and a chip component is accurately positioned on the footprint pattern.
FIG. 3 is a plan view showing a state in which cream solder is printed shifted to the left with respect to the footprint pattern, and the chip component is shifted to the left and positioned in the footprint pattern.
FIG. 4 is a plan view showing a state in which the cream solder is printed shifted to the left with respect to the footprint pattern, and the chip component is shifted upward and positioned in the footprint pattern.
FIG. 5 is a plan view showing a state in which the cream solder is printed shifted to the left with respect to the footprint pattern, and the chip component is shifted downward and positioned in the footprint pattern.
FIG. 6 is a plan view showing a state in which the cream solder is printed so as to be shifted upward with respect to the footprint pattern, and the chip component is accurately positioned on the footprint pattern.
FIG. 7 is a plan view of a printed wiring board according to a second embodiment of the present invention.
FIG. 8 is a plan view showing a state in which a chip component is mounted on a conventional printed wiring board.
FIG. 9 is a cross-sectional view illustrating the Manhattan phenomenon of a chip component.
[Explanation of symbols]
1,51 Printed wiring board 5 Chip component (Surface mount type component)
5A, 5B Electrode unit 10 Substrate body 20, 30, 70, 80 Footprint pattern α Angle BL Reference line CL Center line O Center point P Point farthest from center line

Claims (2)

In printed wiring boards on which surface mount components are mounted,
Board body, comprising a pair of footprint patterns formed on the board body, the electrode portion of the surface-mounted component is soldered,
The planar shape of the pair of footprint patterns is substantially symmetric with respect to a reference line,
The footprint pattern is orthogonal to the reference line and symmetric with respect to a center line that divides the pair of footprint patterns into two in the reference line direction.
A printed wiring board, wherein both end portions of the footprint pattern are bent so as to approach the reference line or are bent away from the reference line. When α is an angle between a line segment connecting the center point of the footprint pattern located on the center line and a point farthest from the center line of the footprint pattern and the center line,
When both ends of the footprint pattern are bent so as to approach the reference line, 0 <α <90 °;
2. The printed wiring board according to claim 1, wherein 90 <[alpha] <180 [deg.] When both ends of the footprint pattern are bent away from the reference line.

Images