JP2000031631A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the improvement in reliability and mounting in high density of wiring. SOLUTION: The external form of a land 5 is made circular, and the opening 10a of a solder resist 10 is made into an ellipse, whose short axis conforms to the diameter of the land 5. A wiring 11 for drawing is made in the section A where the periphery of the land 5 and the opening 10a of the solder resist 10 makes contact with each other. Hereby, the high-density arrangement of wiring becomes possible, and also the junction force of a solder ball to the land 5 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board having lands on which solder balls are fixed via solder, and more particularly to a ball grid array package (hereinafter referred to as BGAP) and a chip size package (hereinafter referred to as "BGAP"). CSP), or a motherboard on which these BGAPs and CSPs are mounted.

[0002]

2. Description of the Related Art BGAP or CSP having a surface mounting structure
In (2), the solder balls are provided in a lattice pattern on the back surface of the interposer, and it is possible to increase the number of pins and the fine pitch. FIGS. 8A and 8B schematically show a conventional BGAP. FIG. 8A is a plan view and FIG. 8B is a side view. In FIG. 1, reference numeral 1 denotes an IC chip, and lands 2 as a plurality of electrode portions are provided in a lattice pattern on the back surface, and solder balls 3 are mounted on these lands 2 respectively. Reference numeral 4 denotes a printed wiring board called an interposer, on which lands 5 arranged in a lattice pattern corresponding to the solder balls 3 are provided. The lands 2 and 5 are connected via solder balls 3 fixed to the lands 2 and 5 by solder. A land 6 connected to the land 5 provided on the front surface via a through hole is also provided on the back surface of the interposer 4. Reference numeral 7 denotes a printed wiring board called a motherboard, and lands 8 are provided corresponding to the lands 6. The lands 6 and 8 are connected via solder balls 9 fixed by solder.

FIG. 9 shows a connection between a solder ball 3 and a land 5 of an interposer 4 using a so-called SMD (Soldeel).
r Mask Determined) structure. That is, in this SMD structure, as shown in FIG. 3A, the outer diameter of the opening 10a of the solder resist 10 is formed smaller than the outer diameter of the land 5, and the outer peripheral portion of the land 5 is
Covered by 0. Reference numeral 11 denotes a lead-out wiring drawn out from the land 5.
Are also covered with the solder resist 10. According to such an SMD structure, the solder 13 does not adhere to the side of the land 5 as shown in FIG.
It is possible to increase the number of wirings 12 between the lands 5 and 5.

On the other hand, the bonding strength of the solder balls 3 to the lands 5 is reduced due to an insufficient amount of the solder 13 attached. For this reason, since the thermal expansion coefficients of the interposer 4 and the IC chip 1 are different, when a stress is generated due to a difference in thermal contraction between the two, there is a problem that the solder ball 3 is easily peeled off the land 5 by the stress. To solve this, the connection structure is non-S
Some are formed by an MD structure. That is, as shown in FIG. 10A, the diameter of the opening 10a of the solder resist 10 is formed to be larger than the diameter of the land 5,
The outer periphery of the land 5 is opened from the solder resist 10. As shown in FIG. 3C, the solder 1 is formed up to the side of the land 5 by the formation as described above.
3 adheres, so that the bonding strength of the solder ball 3 to the land 5 is improved.

[0005]

However, in the above-described non-SMD structure, since the solder 13 adheres to the side of the land 3, the wiring 1 between the lands 3 and 3 is not provided.
There was a problem that the number of 2 was limited. Further, as shown in FIG. 2A, when the number of the lead-out wirings 11 is one, the solder 13 adheres to the base portion 11a of the lead-out wirings 11, whereas the opposite side in the drawing has Since the amount of solder to be attached is small, the amount of solder 13 to be attached is different between left and right. Thus, the solder 1 on the left and right
When the amount of the element 3 becomes asymmetric, as described above, due to the difference in thermal expansion coefficient between the interposer 4 and the IC chip 1, when stress is generated due to the difference in thermal contraction between the two, the stress concentrates on the root portion 11a. However, there is a problem that the root portion 11a is easily peeled off from the interposer 4 and reliability is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a printed wiring board which improves reliability and increases the density of wiring. is there.

[0007]

To achieve the above object, according to the present invention, there is provided a printed wiring board in which a plurality of lands provided with lead-out wirings are covered with a solder resist. Is partially covered with the solder resist, and the other part is opened from the solder resist. Therefore, the number of wirings can be increased in a portion where the outer peripheral portion of the land is covered with the solder resist, and in a portion where the land is opened by the solder resist, the solder adheres to the side of the land. Power improves. According to the eleventh aspect of the present invention, in the printed wiring board in which the periphery of the plurality of lands provided with the lead-out wiring is opened from the solder resist, the lead-out wiring is provided so as to be point-symmetrical from the center of the land. It is a thing. Therefore, the amount of solder adhering to the lead wiring does not become asymmetric from the center of the land.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. 1 is an enlarged plan view showing a main part of a printed wiring board according to the present invention, FIG. 2A is a sectional view taken along the line II (a) -II (a) in FIG. 1, and FIG. 1 is a sectional view taken along the line II (b) -II (b), and FIG. 3 is a plan view of the printed wiring board according to the present invention. In FIG. 1, the outer shape of the land 5 is formed in a circular shape, and the opening 10 a of the solder resist 10 is formed in an ellipse with the diameter of the land 5 as a short axis AA. Are formed.

Therefore, as shown in FIG. 2 (b), the outer periphery of the land 5 is in contact with the opening 10a of the solder resist 10 at the point A, A.
The lead wires 11 are covered with the solder resist 10. Further, as shown in FIG. 2A, the other outer periphery 5a of the land 5 is opened without being covered with the solder resist 10. As shown in FIG. 3, a large number of lands 5 are provided on the interposer 4 radially from the center G1 point of the interposer 4, and the elliptical openings 10a of the solder resist 10 have their major axes extending from the center G1 point. It is provided to extend in the radial direction.

[0010] With such a configuration, as shown in FIG.
Since the solder for fixing the solder ball 3 to the land 5 adheres to the side of the outer peripheral portion 5a opened from 0, the bonding force of the solder ball 3 to the land 5 is improved. Also,
A pair of lead-out wires 11 and 11 are solder resist 1
Since the lead-out wirings 11 are protected by the solder resist 10 by being covered with 0, peeling from the interposer 4 is restricted. Also,
Opening 10a of solder resist 10 formed in an ellipse
Is provided so as to extend in the radial direction from the center G point, so that the distance L between adjacent lands in the direction substantially orthogonal to the radial direction from the center G point is formed. Therefore, more wiring can be provided between these adjacent lands, so that the density can be increased.

FIG. 4 is a plan view of an interposer according to a second embodiment of the present invention. The second embodiment differs from the first embodiment in that many lands on the interposer 4 are arranged in a grid. Even if they are arranged in a grid like this,
As in the first embodiment, the bonding force of the solder ball 3 to the land 5 is improved, the separation of the solder ball 3 from the land 5 due to concentration of stress is prevented, and more wiring is provided between adjacent lands. Can be provided, so that the density can be increased.

In the first and second embodiments described above, all the solder resists 10 on the interposer 4 are formed into ellipses. However, if necessary, due to the difference in the thermal expansion coefficient between the IC chip 1 and the interposer 4, the interposer 4 having the largest stress can be used.
The solder resist 10 corresponding to only the land 5 located at the outermost peripheral portion of the above, that is, at least the portion surrounded by the two-dot chain line in FIGS. 3 and 4 may be formed in an elliptical shape. In this case, lands located other than the portion surrounded by the two-dot chain line can have the SMD structure.
High-density wiring becomes possible. In order to simply improve the bonding force of the solder ball 3 to the land 5, the long axis of the opening 10a of the elliptical solder resist 10 is provided so as to extend in the radial direction from the center G1 point. There is no particular need.

FIG. 5 is a plan view of a main part showing a third embodiment of the present invention. In the third embodiment,
The shape of the land 5 is rectangular, and the opening 10a of the solder resist 10 is a rectangle whose short side 101 is shorter than the long side 51 of the land 5 and whose long side 102 is longer than the short side 52 of the land 5. The wirings 11 are provided on the short sides 52 of the land 5. With this configuration, a part of the long side 51 of the land 5 is released from the solder resist 10, so that the solder adheres to the side of the long side 51, so that the solder ball 3 with respect to the land 5 The joining force is improved. Further, since the lead-out wiring 11 is covered with the solder resist 10, the lead-out wiring 11 is protected by the solder resist 10, and
Therefore, the solder balls 3 are prevented from peeling off from the lands 5.

Here, as shown in FIG. 5, even when the outer periphery of the land 5 is partially covered with the solder resist 10, as shown in FIG.
At the point A, the opening 10 of the solder resist 10
The state in contact with a is also a state in which a part of the outer peripheral portion of the land 5 is substantially covered with the solder resist 10.

FIG. 6 is a plan view of a main part showing a fourth embodiment of the present invention. In the figure, the outer shape of a land 5 is formed in a circular shape, and an opening 10 of a solder resist 10 having a diameter larger than the diameter of the land 5 is formed on the land 5.
a is formed, and the entire outer periphery of the land 5 has a so-called non-SMD structure in which the land 5 is opened from the solder resist 10. The feature of the fourth embodiment is that four lead-out wires 1 drawn out from the land 5 are provided.
1 are provided at equal intervals in the circumferential direction of the land 5, in other words, the four lead-out wires 11
Is provided so as to be symmetrical with respect to the center G2.

With such a configuration, the solder for fixing the solder balls 3 is formed by the four lead-out wirings 1.
1, the four lead-out wires 11 are provided so as to be point-symmetrical with respect to the center G2 of the land 5, so that the amount of the solder to be attached does not become asymmetric from the center of the land 5. Therefore, the solder uniformly adheres to the outer periphery of the land 5, so that the interposer 4 and the IC chip 1
Even if a stress is generated between the land 5 and the solder ball 3 due to a difference in thermal expansion coefficient between the lands 5 and the solder balls 3, it is possible to prevent the extraction wiring 11 from peeling off from the interposer 4 due to the concentration of the stress.

FIG. 7 is a plan view of a main part showing a fifth embodiment of the present invention. The fifth embodiment has a non-SMD structure similarly to the fourth embodiment, and the lead-out wiring 11 is provided so as to be point-symmetric with respect to the center G of the land 5. And this fifth embodiment is
The difference from the fourth embodiment is that two lead wires 11 are used, and the lands 5 and the openings 10a of the solder resist 10 are arranged in a direction perpendicular to the direction BB in which the lead wires extend. The point is that the ellipse has a long axis of C-C.

With this configuration, the width W of the lead-out wiring 11 can be increased without reducing the overall length of the outer periphery of the land 5. The solder adheres, and the bonding force of the solder ball 3 to the land 5 which is an advantage of the non-SMD structure can be maintained. At the same time, by increasing the width W of the lead-out wiring 11, the base 11 a of the lead-out wiring 11 is formed.
Since the adhesion of the base portion 11 to the interposer 4 is improved, the base portion 11 can be more reliably than the above-described fourth embodiment.
a can be prevented from peeling off from the interposer 4.

Table 1 shows that the solder balls 3 for the lands 5
9 is a comparison between the conventional technique of the SMD structure described in FIG. 9 and the fifth embodiment described in FIG. 7, and shows that the bonding strength of the fifth embodiment is smaller than that of the conventional technique. It can be seen that the bonding strength has been improved. This is because the outer shape of the land 5 and the opening 10a of the solder resist 10 is made elliptical, and as described above, the entire length of the outer periphery of the land 5 is not shortened, and the lead-out wiring 11
It is considered that since the width W can be increased, the amount of solder adhering to the outer peripheral side of the land 5 can be increased.

[0020]

EXAMPLE In the fifth embodiment shown in FIG. 7, the short axis of the land 5 is R1, the opening 10a of the solder resist 10 is provided.
Where r1 is the minor axis of R1, R2 is the diameter of land 5 in the prior art shown in FIG. 9, and r2 is the diameter of opening 10a of solder resist 10. R1 = 0.562 mm, r1 = 0.762 mm R2 = 0 .80 mm, r2 = 0.63 mm 2, and the results of comparing the peel strengths are shown in Table 1.

[0021]

[Table 1] Sample number of the product of the present invention: n = 52, sample number of the conventional product: n = 64

[0022]

As described above, according to the first to third aspects of the present invention, the density of the wiring can be increased, and the bonding strength of the solder ball to the land can be improved.

According to the fourth aspect of the present invention, since the lead-out wiring is protected by the solder resist, peeling of the lead-out wiring from the printed wiring board is prevented.

According to the fifth aspect of the present invention, even if stress is generated due to a difference in thermal expansion coefficient between the chip component and the interposer, the bonding of the solder ball to the land is maintained.

According to the sixth aspect of the present invention, even when a stress is generated due to a difference in thermal expansion coefficient between the interposer and the motherboard, the solder ball is kept connected to the land.

According to the seventh to ninth aspects of the present invention, the distance between adjacent lands in the direction perpendicular to the radial direction from the center of the printed wiring board is increased, so that high density can be achieved. .

According to the tenth aspect of the present invention, since parts other than necessary parts can have the SMD structure, high-density wiring becomes possible.

According to the eleventh aspect of the present invention, it is possible to prevent the lead-out wiring from peeling off from the printed wiring board.

According to the twelfth aspect of the present invention, the joining force of the solder ball to the land can be maintained, and the lead-out wiring can be more reliably prevented from peeling from the printed wiring board.

[Brief description of the drawings]

FIG. 1 is an enlarged plan view showing a main part of a printed wiring board according to the present invention.

FIG. 2 (a) shows II (a) -I in FIGS. 1 and 5.
1 (a) is a cross-sectional view, and FIG.
FIG. 2 is a sectional view taken along the line (b) -II (b).

FIG. 3 is a plan view of the printed wiring board according to the present invention.

FIG. 4 is a plan view showing a printed wiring board according to a second embodiment of the present invention.

FIG. 5 is a plan view showing a main part of a third embodiment of the printed wiring board according to the present invention.

FIG. 6 is a plan view showing a main part of a fourth embodiment of the printed wiring board according to the present invention.

FIG. 7 is a plan view showing a main part of a fifth embodiment of the printed wiring board according to the present invention.

FIG. 8 schematically shows a conventional BGAP.
(A) is a plan view and (b) is a side view.

9A and 9B show a main part of a printed wiring board having a conventional SMD structure, wherein FIG. 9A is a plan view, FIG.
(C) is a side sectional view schematically showing a relationship with a wiring.

10A and 10B show a main part of a printed wiring board having a conventional non-SMD structure, where FIG. 10A is a plan view, FIG. 10B is a side sectional view, and FIG. 10C schematically shows a relationship with wiring. It is a side sectional view.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... IC chip, 2, 5, 6, 8 ... Land, 5a ... Side part, 3, 9 ... Solder ball, 4 ... Interposer, 7 ...
Mother board, 10: solder resist, 10a: opening, 11: lead-out wiring, 12: wiring, 13: solder, 51, 102: long side, 52, 101: short side.

Claims (12)

[Claims] 1. A printed wiring board in which the periphery of a plurality of lands on which lead-out wirings are provided is covered with a solder resist, a part of an outer peripheral portion of the lands is substantially covered with the solder resist, A printed wiring board characterized in that other parts are opened from the solder resist. 2. The printed wiring board according to claim 1, wherein the shape of the land is circular, and the opening of the solder resist is an ellipse having a diameter of the land as a short axis. 3. The printed wiring board according to claim 1, wherein the outer shape of the opening of the land is rectangular, and the opening of the solder resist is formed such that the shorter side is shorter than the longer side of the land and the longer side is shorter than the longer side of the land. A printed wiring board having a rectangular shape longer than a side. 4. The printed wiring board according to claim 1, wherein the lead wiring is covered with a solder resist. 5. A printed wiring board according to claim 1, wherein said printed wiring board is an interposer for a semiconductor device. 6. A printed wiring board according to claim 1, wherein said printed wiring board is a mother board on which electronic components are mounted. 7. The printed wiring board according to claim 1, wherein a portion opened by the solder resist is provided radially from a center of the printed wiring board. 8. The printed wiring board according to claim 7, wherein a plurality of lands are arranged in a grid. 9. The printed wiring board according to claim 7, wherein a plurality of lands are arranged radially from a center of the printed wiring board. 10. The printed wiring board according to claim 1, wherein at least a part of an outermost land is substantially covered with the solder resist, and another part is opened from the solder resist. And printed wiring board. 11. A printed wiring board in which the periphery of a plurality of lands on which lead-out wirings are provided is opened from a solder resist, wherein the lead-out wirings are provided so as to be point-symmetric from the center of the lands. Printed wiring board. 12. The printed wiring board according to claim 11, wherein two lead-out wirings are provided, and the opening of the land and the solder resist has a major axis in a direction orthogonal to a direction in which the lead-out wirings extend. A printed wiring board having an elliptical shape.